Heat/Mass Transfer Analogy  Laminar Boundary Layer


 Jane Berry
 1 years ago
 Views:
Transcription
1 Chapter 3. Heat/Mass Transfer Analogy  Laminar Boundary Layer As noted in the previous chapter, the analogous behaviors of heat and mass transfer have been long recognized. In the field of gas turbine heat transfer, several experimental studies have been done with mass transfer because of its experimental advantages. In such cases, it was required that the heat/mass transfer analogy function be well known. This chapter reviews the conventional heat/mass transfer analogy function and numerically generates the analogy functions to examine their behaviors under the influences of streamwise pressure gradients and different thermal boundary conditions (BCs). For practical reasons, the fluid assumed in the heat transfer is air (Pr = 0.707) and that of the mass transfer is air with naphthalene being the substance to be transported (Sc = 2.28). Furthermore, since a typical use of heat/mass transfer analogy is to convert mass transfer data to heat transfer data, discussions are focused mainly on such a direction of the conversion. 3.1 Analytical Solutions Conventional relationship 20
2 The conventional relationship for laminar boundary layer flow is given by the following simple expression. 1 3 Nu Pr = (3.1.1) Sh Sc The conditions under which this equation is applicable are (1) no streamwise pressure gradient (plane wall, also called flat plate), (2) the same Reynolds number and (3) uniform temperature BCs. Note that this analogy function does not depend on streamwise position; in other words, a single value can be applied to all streamwise positions, provided that the flow is laminar. For this reason, the analogy functions are sometimes called the analogy factor in the present study, referring to the ratio of Nusselt number to Sherwood number. This section discusses how this analogy function comes about. Heat and mass transfer processes are governed by the partial differential equations: energy (or temperature) and mass transfer equations, respectively. For a steadystate and flow, twodimensional, laminar, incompressible boundary layer, they reduce to the following expressions. T T u + v x y m m u + v x y 2 T = α 2 y 2 m = D 2 y (3.1.2) (3.1.3) Since the velocity parameters, u and v, are involved, the continuity equation and the momentum equation of the boundary layer must be introduced. u v + = 0 (3.1.4) x y u u u + v x y 2 u = ν 2 y (3.1.5) The above momentum equation assumes no streamwise pressure gradient, incompressible flow and constant properties. Now we have four equations and four unknowns, u, v, T and m. Comparing Eqns. (3.1.2) and (3.1.3), when α = D, the temperature and the mass 21
3 transfer equations are identical. Upon nondimensionalizing Eqns. (3.1.2) and (3.1.3), the thermal diffussivity, α, and the diffusion coefficient, D, are replaced by the dimensionless transport properties: Prandtl number, Pr, and Schmidt number, Sc. They are defined by: ν ν Pr = ; Sc = (3.1.6 and 7) α D Solution methods are discussed in Eckert and Drake (1987) and Kays and Crawford (1993). The resulting Nusselt number, Nu, distribution for a laminar boundary layer as a function of streamwise position is well approximated as follows. 1/ 2 1/ 3 Nu x = Re x Pr (3.1.8) Similarly, for the mass transfer equation, the Sherwood number, Sh, distribution yields: 1/ 2 1/ 3 Sh x = Re x Sc (3.1.9) Equation (3.1.1) can now be obtained by dividing Eqn. (3.1.8) by Eqn. (3.1.9), assuming the same xreynolds number. As is obvious from Eqns. (3.1.2) and (3.1.3), Nu is equal to Sh when Pr is equal to Sc. Furthermore, in the case of air (Pr = 0.707) and naphthalene (Sc = 2.28), the analogy function becomes: Nu = (3.1.10) Sh As noted earlier, this relation assumes the same Reynolds number, the uniformlevel BCs (uniform wall temperature for the heat transfer and uniform mass concentration for the mass transfer) and no streamwise pressure gradients. Effects of these assumptions are evaluated in the next section Analytical solution to the crossboundarycondition analogy The conventional relationship was derived assuming both processes having the identical level boundary condition (BC). This relation, Eqn. (3.1.1), may be sufficient in gas turbine heat transfer studies as shown by the numerical simulations in the next section. When results from a mass transfer experiment are used to estimate heat transfer situations in an actual gas turbine engine, the conversion is from uniformlevelbc masstransfer 22
4 data to uniformlevelbc heattransfer data, for which Eqn. (3.1.1) is most suited. The gas turbine heat transfer situation is best simulated with a constant wall temperature boundary condition. This is because variations in temperature at the airfoil surface are relatively small compared to the difference between the surface and freestream temperatures (e.g. pp in Boyce, 1982). The next few sections show that this relation is quite accurate for a surface with nonzero streamwise pressure gradients. Another analytical solution is easy to derive. This is for the cases in which boundary conditions do not match between the two processes: a uniform level for one and a uniform flux for the other. Here, the relation is first derived, and discussions are made on its meaning and possible applications. Assuming a flat plate and laminar boundary layer, the distribution of Nusselt number for a uniform heat flux BC is well approximated by the following (Kays and Crawford 1993). 1/ 2 1/ 3 Nu x = 0.453Re x Pr (3.1.11) Dividing this by Eqn. (3.1.9) yields the analogy function for the crossbc processes. 1 3 Nu Pr = 1.36 (3.1.12) Sh Sc Corresponding to Eqn. (3.1.10), the above expression, for air and naphthalene, results in: Nu = (3.1.13) Sh Again, this relationship is not a function of Reynolds number or streamwise position. Noteworthy is that the value for the crossbc processes, Eqn. (3.1.13), differs 36% from the value for the conventional relationship, Eqn. (3.1.10). The first discussion focuses on a significance of these results. Because the governing partial differential equations are essentially identical for mass and heat transfer, Eqn. (3.1.12) can, for example, be written for two processes, both being heat transfer: Nu Nu Pr6 = Pr (3.1.14) 5 23
5 Here, the subscripts 6 and 5 designate the two different fluids and BCs; fluid 6 is at a uniform flux BC, and fluid 5 is at a uniform level BC (corresponding to designations introduced later, see Table 3.1). When these are the same fluids, the ratio of Nusselt numbers becomes This means that the heat transfer coefficient at any location on a flat plate with uniform heat flux BC is always 36% greater than that of the plate with the same Reynolds number (same location if ν 5 = ν 6 ) with a uniform temperature BC. This can be realized by comparing Eqns. (3.1.1) and (3.1.12) since the denominators have the same processes in the both equations. One possible application of this analogy function is to convert data from a heat transfer experiment with a uniform flux BC to uniformtemperature BC data. This would be useful especially since many heat transfer experiments (such as steady state measurements with liquid crystals) are done with uniform heat flux BCs. However, as shown in the next section, streamwise pressure gradients have a greater effect on Eqn. (3.1.14) than on Eqn. (3.1.1); the crossbc functions for an airfoil profile deviate from Eqn. (3.1.14) more than the matchingbc functions for an airfoil profile deviate from Eqn. (3.1.1). For this type of an application, it is necessary to study how pressure gradients affect the analogy functions. Another possible case in which the crossbc analogy function, Eqn. (3.1.12), may be useful is when a heat transfer experiment with a uniform heat flux BC is directly compared with a mass transfer experiment with a uniform mass concentration BC in order to determine effects of streamwise pressure gradients. Because of the identical governing PDEs, the mass transfer experiment is representative of both mass and heat transfer processes with a uniform level BC. The results of the comparison should be expressed as magnitudes of deviations from Eqn. (3.1.12). It will be shown that converting the mass transfer data into the heat transfer data with both at a uniform level BC should not be a problem even for a case with streamwise pressure gradients by the use of the conventional relationship, Eqn. (3.1.1). Once the generalized effect of pressure gradients is determined, this relationship may be applied when boundary conditions do not match. 24
6 3.2 Analogy Functions on the CF6 Profile Setup of cases This chapter uses the numerical boundary layer code, TEXSTAN, to computationally determine Nusselt number distributions for various flow and boundary conditions (BCs). Heat/mass transfer analogy functions are obtained from numerically evaluated Nu and Sh distributions under the flow and BCs of interest. In this section, the streamwise pressure (or velocity) gradient of the General Electric CF6 engine firststage vane is implemented into the simulations, and results are compared to the corresponding zeropressuregradient case. Also varied are BCs in order to examine the effects on the analogy function. The primary reason that the different BCs are tested is that a mismatch in BCs is frequent when heat transfer rates are experimentally determined from mass transfer experiments. Many heat transfer experiments are done with the BC of a uniform heat flux. If data from such experiments are used to calculate the analogy function, consistency with Eqn. (3.1.1) would be lost, for this equation was derived assuming uniform level BCs in both the mass and heat transfer experiments. Therefore, it is important that one knows the effects of different combinations of BCs. Figure 3.1 shows the velocity profiles of the CF6 and the GE90 profiles on the suction surfaces. The GE90 profile is used in the next section. The suction side profiles are shown here, and all the analyses focus on the suction side. This is because suction sides usually are of more interest, for they are the ones subjected to influences such as flow separation, transition and threedimensional secondary flows. When the input data files to TEXSTAN are prepared, all possible combinations of the three factors are sought, except cases of mass transfer with flux boundary conditions. This accumulates the number of cases considered in this section to six, and they are summarized in Table
7 Us/Uex CF6 profile GE90 profile x/c Figure 3.1 Velocity profiles of the CF6 and GE90 blades, normalized on exit velocity. The CF6 from Chen (1988) and the GE90 from Wang (1997). Table 3.1 Summary of cases for the CF6 profile Case CF61 CF62 CF63 CF64 CF65 CF66 Profile CF6 U s =constant plane wall Sc or Pr B.C. T w q w T w q w 26
8 The following is a description of each of the cases simulated in this section. This list can be applied also to the cases simulated in the next section with the GE90 profile. Case CF simulation under the same conditions as Chen (1988; and Chen and Goldstein, 1992), an experiment with the CF6 profile, a uniform mass concentration and a naphthalene/air mixture being the fluid Case CF case CF61 converted by Eqn. (3.1.1) to heat transfer to air Case CF simulation under the same conditions as Chung (1992; and Chung and Simon, 1993), an experiment with the CF6 profile, a uniform wall heat flux and air being the fluid Case CF the CF61 case with the pressure profile replaced with a uniform velocity, a flat plate case Case CF case CF64 converted by Eqn. (3.1.1) to heat transfer to air Case CF Case CF63 with the pressure profile replaced with a uniform velocity of a flat plate case Two other possible cases, processes with uniform mass flux BCs, were not included because, when a mass transfer experiment is done with naphthalene, the BC is of a uniform mass concentration (a uniform level, equivalent to uniform temperature), and usually, the conversion is performed from mass transfer to heat transfer. Thus, the cases with uniform mass flux are not important. Since two of the above cases correspond to heat transfer processes and the others mass transfer, there are 8 combinations for which to produce some kind of analogy functions. However, only the practical cases are analyzed. They are described below. As the original analogy function is expressed in terms of the ratio, Nu/Sh, the numerators below correspond to heat transfer processes and the denominators to mass transfer. CF65/CF reproducing Eqn. (3.1.1) with the same boundary conditions. CF62/CF same BCs as CF65/CF64 but with the CF6 pressure profile 27
9 CF63/CF the conditions used to compare the Chen s and the Chung s experiments as done in the next chapter CF66/CF same as CF63/CF61 but with absence of pressure gradient effects on both the mass and the heat transfer processes. CF64/CF both mass transfer processes. This shows effects of the streamwise pressure gradient. CF62/CF both heat transfer processes. This shows effects of the shift in BCs. If this were a simple function, one could easily convert the data from an experiment with a uniform heat flux BC to those of a uniform temperature BC, the latter being more representative of actual engine conditions. For each of the above six different cases, an input data file to TEXSTAN was prepared. They are presented in Appendix A. To introduce the computational code used in the present study, TEXSTAN was originally developed as the STAN5 program by Crawford and Kays (1976). The reference here provides theoretical backgrounds and instructions for STAN5, and basically the same operations apply to TEXSTAN. These programs solve transport equations such as momentum, energy and mass for twodimensional, internal and external boundary layer flows. The user of these programs is to prepare an input file that lists all necessary parameters such as boundary conditions and physical properties and directions for the outputs. The user solves the momentum equation and, if desired, heat and/or mass transport equations Results and discussions Figure 3.2 presents the variations of heat/mass transfer analogy functions versus streamwise positions. In a numerical simulation of a boundary layer, heat (or mass) transfer rates are calculated based on temperature (or mass concentration) gradients at the surface. The calculation cannot proceed after the flow separates, at which point the velocity gradient becomes zero. This is what happens to cases 3/1 and 2/1 near x/c of 28
10 0.95. Looking at the velocity profile on Fig. 3.1, one finds that the flow separates just after the mainstream flow starts to decelerate at x/c of 0.8. There are two main trends seen in Fig Both the functions 2/1 and 5/4 are essentially the same, as Eqn. (3.1.1) implies, the F ref value of Fig. 3.2, while functions 3/1 and 6/4 differ. First of all, looking at the functions that are consistent with Eqn. (3.1.1), one realizes that each pair consists of the same pressure profile (either the CF6 or flat plate) and the same level BC (temperature and mass concentration). Also, the pair 2/1 is only very weakly dependent on the nonzero pressure gradient. At this point, it can be concluded that using Eqn. (3.1.1) to convert mass transfer data would yield a perfect estimate of flatplate heat transfer with uniform temperature BC if the mass transfer were done with a flat plate. Similarly, it would yield an almost perfect estimate of heat transfer with the CF6 profile and uniform temperature BC if the mass transfer were also done with the CF6 profile. In other words, a single value from Eqn. (3.1.1) based only on Pr and Sc can be used to convert Sh to Nu at any and all streamwise locations, assuming that the heat transfer process has the same pressure profile, the same Re and a uniformtemperature BC. Second of all, the other two lines presented in Fig. 3.2, 3/1 and 6/4, form another group; the 3/1 line appears to vary in the vicinity of the 6/4 line. Referring to Table 3.1, one realizes that each line consists of heat transfer with a uniform flux BC and mass transfer with a uniform level BC crossbc analogy functions. To define the crossbc analogy functions, I would like to refer to heat transfer with a uniform flux BC and mass transfer with a uniform level. Since a mass transfer experiment with naphthalene provides a uniform level BC, this is often the case in converting mass transfer data to get heat transfer coefficients using the analogy functions. Contrary to the behavior when numerator and denominator had level BC s, crossbc conversions cannot be approximated by Eqn. (3.1.1) or Eqn. (3.1.12). Moreover, line 3/1 (both on the CF6 profile) is not as close to the line 6/4 (both on flat plate) as line2/1 (both on the CF6 profile) is to the line 5/4 (both on flat plate). Therefore, even when the line 6/4 is 29
11 analytically derived, it is not a representative of crossbc analogy functions for cases of nonzero pressure gradient. The importance of this lies in the fact that many heat transfer experiments are done with a uniform flux (a uniform heat flux) /1 6/4 Nu/Sh /1 5/4 F ref x/c Figure 3.2 Analogy functions for the CF6 profile and the corresponding flat plate cases. Re c =171,000 and P/C=0.77 (x/c=1.25 at the trailing edge). F ref corresponds to the value from Eqn. (3.1.1). Case designations are simplified such as 3/1 for CF63/CF Analogy Functions on the GE90 Profile Setup of cases In this section, distributions of analogy functions on the GE90 profile and the corresponding flat plate cases are calculated, using the TEXSTAN program, and discussed. The velocity profile of the GE90 blade is provided in Fig. 3.1, and the cases of the computations are summarized in Table 3.2. The GE90 is a newer engine than the CF6 from General Electric, and its profile has a longlasting acceleration region compared to the CF6 profile, almost one half of the entire surface length. Table 3.2 is essentially the 30
12 same as Table 3.1, except that, where nonzero velocity profiles are implemented, the GE90 replaces the CF6 profile. Therefore, the GE901 case and the CF61 case, for instance, are under the same conditions except for the velocity profiles. The case descriptions in the previous section can still be used, and all the six pairs of analogy functions that were generated in the CF6 case are regenerated for the GE90 case. Table 3.2 Summary of cases for the GE90 profile Case No. Nu or Sh (profile #, fluid, BC ) GE901 Sh ( GE90, Sc=2.28, T w ) GE902 Nu (GE90, Pr=0.707, T w ) GE903 Nu (GE90, Pr=0.707, q ) GE904 Sh (f.p. *, Sc=2.28, T w ) GE905 Nu ( f.p. *, Pr=0.707, T w ) GE906 Nu (f.p. *, Pr=0.707, q ) # freestream velocity profile * flat plate profile (uniform freestream velocity) Results corresponding to the Wang s experiment Figure 3.3 presents four of the six analogy functions generated in this section, and the other two are discussed in the next section. The cases with the nonzero pressure gradient again indicate flow separation near x/c of By this point, the flow has remained attached for a quite a long distance against adverse pressure gradients downstream of the beginning of deceleration near x/c of 0.7. This is remarkably longer than in the CF6 case in which flow separates just after the pressure gradient sign reverses. This may be 31
13 because of differences in the degree of deceleration and thinner boundary layers in the case of the GE90, due to the prolonged strong acceleration. Now, the results in Fig. 3.3 look quite similar to those in Fig. 3.2: lines 2/1 and 5/4 forming one group and lines 3/1 and 6/4 forming the other. The fist group behaves in the same way as the one in the CF6 profile cases. The flat plate pair, 5/4, again confirms the validity of Eqn. (3.1.1), and, together with the line 5/4 on Fig. 3.2, it is shown that the reference value, F ref = 0.66, is not a function of Reynolds number. The GE90 profile pair, 2/1, varies only a little from the reference value, F ref, compared to lines, 3/1 and 6/4. The other group of lines, 6/4 and 3/1, has the crossbc analogy functions. The flat plate function, 6/4, records the value 0.92, the same as the one from the line 6/4 in Fig This shows that the analogy function for crossbc cases with the absence of the pressure gradient may not depend on Reynolds number. A simple relation such as Eqn. (3.1.12) may be possible for crossbc cases. The deviations of lines 3/1 and 2/1 from the lines 6/4 and 5/4, respectively, in Fig. 3.3 seem greater than the corresponding deviations in Fig. 3.2 although line 2/1 still deviates from F ref only slightly. Figures 3.2 and 3.3 are not enough to conclude that the GE90 profile produces larger errors from the corresponding flat plate cases than does the CF6 profile. This is because the GE90 cases are simulated at a greater chord Reynolds number. The next section discusses whether these deviations are actually due to the greater Reynolds number or the difference in the pressure profiles. 32
14 /1 6/4 Nu/Sh /1 F ref 0.4 5/ x/c Figure 3.3 Analogy functions, Nu/Sh, for the GE90 profile and the corresponding flat plate cases. Re c =540,000 and P/C=0.75 (x/c=1.38 at the trailing edge). F ref corresponds to the value from Eqn. (3.1.1). Case designations are simplified, such as 3/1 for GE903/GE Results corresponding to the Chen s chord Reynolds number This section examines the cases with the GE90 profile to which Chen s chordreynolds number is applied, i.e. the Reynolds number used in the section 3.2. The resulting analogy functions are compared with those in the section 3.2 (the results shown in Fig. 3.3 could not be compared with Fig. 3.2 because of the difference in the Reynolds numbers). The results of this section are presented in Fig. 3.4, and comparing with Fig. 3.2, will reveal effects of different pressure profiles. Any difference in the distributions shown in Fig. 3.4 from those in Fig. 3.3 is hard to distinguish. In fact, the two figures look exactly the same. This is expected from the discussions in section 3.1. The effects of Reynolds numbers cancel each other when the numerator and the denominator have the same profile. 33
15 /1 2/1 6/4 Nu/Sh / x/c Figure 3.4 Analogy functions, Nu/Sh, for the GE90 profile and the corresponding flat plate cases. Re c =171,000 and P/C=0.77 (x/c=1.38 at the trailing edge). F ref corresponds to the value from Eqn. (3.1.1). Case designations are simplified such as 3/1 for GE903/GE
16 3.4 Heat/Heat and Mass/Mass Analogy Functions Origins of nonuniform analogy functions In the previous sections, all analyses were based on analogy functions between a fluid with Pr=0.707 (representing air) and a fluid with Sc=2.28 (representing naphthalene), and it was demonstrated that some pairs of processes resulted in rather uniform analogy functions and others do not. This section attempts to further examine different effects that form a nonuniform distribution of the analogy function. One of the most significant effects is the difference in the thermal boundary conditions (BCs) as discussed in the previous section. The first step here is to examine the effect of pressure profiles in cases with a transport property of The second step is to examine the effect of thermal boundary conditions in cases with a transport property of Obviously, a uniform distribution of the analogy function is advantageous, so it is important to know under what circumstances the analogy function is not uniform and how it may behave in such cases. When the function is uniform over a surface such as lines 6/4 and 5/4 in Figs. 3.2, 3.3 and 3.4, a single factor can be applied to the entire surface in order to convert Sherwood numbers to Nusselt numbers, for example. When the function is not uniform, e.g. line 3/1 in Figs. 3.2, 3.3 and 3.4, the conversion factor is dependent on locations on the surface. Even if the variations along the surface cannot possibly be predicted by knowing the effects of different causes, one should be able to determine when the analogy function may behave with large deviations. Pressure profiles may be thought to heavily affect uniformity of the analogy function distribution. However, this is not always true. For example, line 3/1 in Figs. 3.2, 3.3 and 3.4 is a case with nonzero pressure gradient profiles and deviates from line 6/4 which is the identical case, except for the zero pressure gradient profiles. This large deviation is not observed between the pairs 2/1 and 5/4. Therefore, the deviation of line 3/1 has a combined effect of thermal BCs and pressure profiles. Pair 4/1 is chosen to examine the effects of pressure profiles since it is an intermediate case between 3/1 and 35
17 6/4. Pair 2/3 is chosen to examine the effects of thermal boundary conditions since it may become useful in converting fluxbc experimental data to levelbc data The effects of pressure profiles in mass/mass transfer analogy: line 4/1 Since the transport property of 2.28 was assumed to represent Sc of naphthalene, pair 4/1 might be called a mass/mass analogy. Line 4/1 in Figs 3.5, 3.6 and 3.7 is discussed here as an example of a pair with levelbcs and identical transport properties. Looking at each figure, the shape looks exactly like line 3/1 in the previous figures, except near the leading edge. The resulting distributions clearly show that the trends are similar to lines 3/1 and 2/1 in Figs. 3.2, 3.3 and 3.4, except for the magnitudes of deviation. In other words, when line 3/1 has a positive slope, line 2/1 also has one. Therefore, it can be concluded that the shapes of lines 3/1 and 2/1 are due to the pressure gradients, and the BCs are mainly responsible for the magnitudes of the deviations from the corresponding plane wall cases /1 Nu/Sh / x/c Figure 3.5 CF6 Chen cases, Re c =171,000 and P/C=0.77 (x/c=1.25 at the trailing edge) 36
18 For case 1, which assumes nonzero pressure gradients, values of the analogy function in the vicinity of the stagnation point can be analytically calculated using the wedge flow solution (Eckert and Drake 1987). This solution method may be used where velocity in the freestream, U s, can be expressed as: U s m = c x (3.4.1) The exponent, m, is described as follows. x du s m = (3.4.2) U dx s According to Eckert and Drake (1987), the resulting Nusselt number for a boundary condition (BC) of uniform wall temperature is: Nu 1/ 2 1/ 3 x = f (m) Re x Pr (3.4.3) We know, at this point, that the above equation is the same as: Sh 1/ 2 1/ 3 x = f (m) Re x Sc (3.4.4) This equation can now be used for line 4/1. Here, the coefficient, f(m), is a constant with x but which depends on the acceleration parameter, m, in Eqn. (3.4.2), and is tabulated in Kays and Crawford (1993) as the form of f(m) multiplied by Sc 1/3. One can apply Eqn. (3.4.4) to the stagnation flow region (small x/c) of the line 4/1. The numerator is the flat plate case where m = 0, and the stagnation flow is assumed for the denominator, m = 1. Therefore, f(0) = 0.41 and f(1) = 0.72 yield (pp.167, Kays and Crawford 1993). The following results since Sc is the same for the both cases. Sh Sh 4 1 1/ 3 f (0)Sc U s, U s,4 U s,4 = = = 0.57 (3.4.5) 1/ 3 f (1)Sc U 0.72 U U s,1 The numerator of the above equation is for the flat plate case for which m is zero. The denominator is for the case with the nonzero pressure gradients for which stagnation flow with m being 1.0 is assumed near the leading edge since the velocity increase is linear with x. The factor, therefore, is dependent on the ratio of freestream velocities. The ratio theoretically begins with infinity at the leading edge since the velocity at the stagnation point, U s,1, is zero. For this reason, longlasting acceleration, e.g. the GE90 profile, causes a continuous decrease seen until x/c of about 0.3 in Figs. 3.6 and s,1 s,1
19 1.4 Nu/Sh /1 2/ x/c Figure 3.6 GE90 Wang cases, Re c =540,000 and P/C=0.75 (x/c=1.38 at the trailing edge) Once passing the acceleration regions, line 4/1 behaves differently, depending on the pressure profiles. The GE90 profile, with longlasting acceleration, tends to have lower values in this region whereas the CF6 profile jumps from the minimum to a high value. The differences between the figures seem to be greater between different pressure profiles (Fig. 3.5 and Fig. 3.6) than between different chord Reynolds numbers (Fig. 3.6 and Fig. 3.7). The only difference between cases 4 and 1 is the pressure profile, and, in case 1, there is a point (or two) at which pressure gradient, at least locally, is zero. This can be used to check the behavior of line 4/1 in the figures. If both had no pressure gradient, meaning that they are identical cases, the line would remain at Sh/Sh of 1.0 throughout the airfoil. Though the local mass transfer process depends on the local conditions as well as the flow history, one can observe that, when local pressure gradient becomes zero, the Sh/Sh values tend to adjust toward
20 /1 Nu/Sh / x/c Figure 3.7 GE90 profile with Chen s Reynolds number, Re c =171,000 and P/C=0.77 (x/c=1.38 at the trailing edge) For ease, the GE90 profile can be looked at first. According to Fig. 3.1, the GE90 profile has a point at which no acceleration or deceleration is present (x/c of 0.68). At this streamwise position, the Sh/Sh values in Figs. 3.6 and 3.7 are about 0.8, moving toward 1.0. At x/c of 1.0, line 4/1 in Fig. 3.6 crosses the Sh/Sh value of 1.0. This delay of reaching 1.0 seems to be the effect of the flow history, which has suppressed the boundary layers from growing. The flow in the GE90 profile has experienced a long acceleration period when it ends. The boundary layer of such flow is still different from the one having developed on a flat plate. Following the acceleration period in the GE90 profile is the deceleration period. Deceleration seems to strongly change boundary layer characteristics, thereby increasing the Sh/Sh values. Finally, it reaches the maximum value just before the flow separates. The CF6 pressure profile is much more flat than the GE90 profile, as seen in Fig Therefore, the Sh/Sh values in Fig. 3.5 vary but remain close to closer to 1.0. The 39
21 profile has a point of zero gradient just after the stagnation flow region near the leading edge. The Sh/Sh values quickly adjust to near 1.0. From this point on, the profile has a few points at which the gradient becomes zero and the Sh/Sh values tend to converge to 1.0. Regardless of the type of pressure gradient, line 4/1 strongly responds to adverse pressure gradients. Just before the flow separates, it goes beyond 1.0 and even over 1.2 for the GE90 cases. One must note here, however, that the local freestream velocity is not equal to that of the plane wall case, and the normalized local freestream velocity at separation of each pressure profile is also different. Therefore, to conclude that the difference in the pressure profiles caused the GE90 profile to have higher analogy factors at separation may be too hasty The effects of thermal BC in heat/heat transfer analogy: line 2/3 Line 2/3 in Figs. 3.5, 3.6 and 3.7 corresponds to both cases having the same nonzero pressure gradients, the same transport property of (presumably air) but different BCs. To be precise, the numerator, case 2, is with a uniform level BC and the denominator, case 3, with a uniform flux BC. If this analysis of line 2/3 yielded a sufficiently flat profile of the analogy function, the function could be used together with the analogy 2/1 to form the analogy 3/1, which is the analogy between uniform level mass transfer data and uniform flux heat transfer data. When this combined process, 2/3 and 2/1, can be simply expressed, an experimental relationship for the crossbc analogy functions can be found. This is done in the next chapter. Besides different Reynolds numbers, deriving a simple analogy function requires understanding the effects of mismatching BCs. This section addresses the crossbc effect as augmented by the nonzero pressure gradients. Unlike the pair 4 and 1, cases 2 and 3 have the same geometry. Therefore, the flow fields are identical. If, by any means, the uniform level BC generated a similar temperature field as that of the uniform flux BC, the Nu/Nu ratio again would be near
22 However, this is clearly not the case. The Nu/Nu values are confined in the region between 0.6 and 1.0, smaller variations than in the previous study (4/1). In the three figures, some trends can be observed. The distributions always begin with the ratio of 1.0 at the leading edge and quickly decrease, without sudden changes, toward values in the vicinity of 0.7 and 0.8. At the point of separation, each analogy factor reaches the minimum of almost 0.6. Remaining always less than 1.0 is expected because of the earlier discussion regarding the development of Eqn. (3.1.12). In fact, the inverse of the equation can be used to explain the major part of the behavior of line 2/3 in Figs. 3.5, 3.6 and 3.7. Because line 2/3 assumes the same transport property, the ratio is unity. Therefore, Eqn. (3.1.12) is left only with the coefficient 1.36, and its inverse is Originally, the equation is developed for a plane wall case with the Nusselt number assumed to result from uniformflux BC and the Sherwood number from a uniformlevel BC. The only difference from line 2/3 is the pressure profile, besides the inverted ratio. Thus, for a flat plate case, 6/5, we expect a value of 1/1.36 (= 0.735, see also Eqn ). A general trend then is, except near the leading edge, that the local analogy factor is greater than when the flow accelerates and less when decelerating. The flow history seems not to matter much here. When the velocity profiles get flat, the analogy factors seem to quickly adjust to The magnitudes of the deviations from the reference value of seem to be a function of flatness of the velocity profiles; the flatter CF6 profile deviates less than does the lessflat GE90 profile. Finally, whether this analogy function is useful in converting fluxbc heat transfer data to levelbc heat transfer data for laminar flow regions is dependent on the type of pressure profile. 3.5 Considerations on Flow Transition from Laminar to Turbulent As discussed in the next Chapter, the conventional analogy factor for turbulent boundary layers is different from that of laminar boundary layers (compare Eqns. (4.1.2) and 41
23 (3.1.10) ). Therefore, it would be interesting to find how the factors vary in the transition region. One way to do this may rely on experimental data. If there were two identical experiments, except that one was heat transfer experiment and the other mass transfer, the two data sets could be compared to determine analogy factors in the transition region. This is a motivation to the next chapter in which the factors in transition regions are discussed. Another possibility to study variations of analogy factors in transition regions is to extend the TEXSTAN calculations performed in this Chapter. The program has a capacity to simulate transitions and turbulent flows. However, the calculations performed so far had these features disabled so that no transition or turbulence modeling would be necessary. Therefore, the calculations stopped when flows reach separation or the trailing edge, remaining laminar throughout. By implementing transition and turbulence models, the above calculations can be extended to the factors in transition regions and into turbulent boundary layer regions. To do this, however, one must know which transition model is best suited for the flow that is simulated. An option available in TEXSTAN is to provide the program with a momentumthickness Reynolds number as an indicator for the beginning of transition. The Reynolds number, Re m, increases with the streamwise positions, and transition is expected to begin where Re m reaches a transition value. Therefore, with this option, the user of the program must have, at least, an estimate of the transitional Reynolds number. Momentumthickness Reynolds number is a simple indicator to predict the beginning of transition, and it has been discussed quite extensively. McDonald (1973) establishes a relation between displacementthickness Reynolds number and freestream turbulence (Figure 1). Almost twenty years later, Mayle (1991a and 1991b) developed, from more experimental data, an equation for transitional momentumthickness Reynolds number as a function of freestream turbulence intensity. Mayle emphasizes a good agreement between the McDonald s relation, also called AbuGhannam and Shaw relation, and the Mayle s equation, which reads: 42
24 Re m,tr 5/ 8 = 400TI (3.5.1) Both McDonald s and Mayle s relations are plotted in Fig. 3.8, along with momentum thickness Reynolds numbers calculated by TEXSTAN for the CF6 velocity profile. At a first glance of Fig. 3.8, one recognizes that the Re m from TEXSTAN does not reach either of the transition Reynolds numbers, even at the point of separation. Even at this point, the TEXSTAN Re m is much lower than the transition values. This then suggests that the transition take place after flow separation, since we know, from Chung s and Chen s experiments, that the boundary layers near the trailing edge of the CF6 profile are turbulent. This is consistent with Chen s discussions in his study (section 5.3 in Chen, 1988). One reason for the difference in momentum thickness Reynolds numbers between the models and the TEXSTAN Re m is that the models assume no streamwise pressure gradients. The TEXSTAN calculation prescribes adverse pressure gradients toward the trailing edge, which considerably reduce transitional Reynolds numbers. This analysis raises yet another question regarding the analogy function: What is the analogy function in the region of flow separation? This is left for further studies in the analogy function. 43
25 Rem McDonald Mayle TEXSTAN x/c Figure 3.8: Comparison of critical momentum thickness Reynolds numbers for the CF6 velocity profile that is shown in Fig Conclusions The heat/mass transfer analogy function is studied for laminar boundary layers. Transport of heat and sublimation of naphthalene from heated and naphthalenecoated surfaces, respectively, are assumed. Analytical and numerical calculations have resulted in various values and distributions of the analogy function, depending on the combinations of pressure profiles and thermal boundary conditions. Furthermore, to examine the effects of these two, a mass/mass analogy function and a heat/heat analogy function are developed. First, two analogy factors are developed analytically for plane wall cases. The analogy factor, Nu/Sh, of is a conventional relationship which assumes zero pressure gradients and uniformlevel boundary conditions for both heat and mass transfer processes. It is a motivation to the present study to examine how the analogy function 44
26 deviates from this conventional value by changing the boundary conditions and pressure profiles. The other analogy factor developed is (1.36 multiplied by 0.677). This factor assumes zero pressure gradients for both and fluxbc for heat transfer and level BC for mass transfer. The effect is a 36% increase in the analogy factor due to the flux boundary condition assumed in the heat transfer process. Still, the single value of may be applied to an entire surface. Second, the TEXSTAN program is employed to numerically calculate the analogy functions for nonzero pressure gradients, namely the CF6 and GE90 profiles. The above two analytical solutions are verified, and the nonzero gradient cases exhibit deviations from the corresponding plane wall cases. The magnitudes of the deviations are different, depending on the thermal BC assumed in the heat transfer processes. The deviations are larger with a heat flux BC than with a uniform temperature BC. These behaviors are similarly observed in both the CF6 and the GE90 cases. Third, two pairs of processes that are not heat/mass analogies are considered in order to further investigate the effects of pressure gradients and thermal BCs. To see the effects of pressure profiles, mass/mass analogy is developed. The resulting shape of line 4/1 in Figs. 3.5, 3.6 and 3.7 suggests that the shapes of lines 3/1 and 2/1 in Figs. 3.2, 3.3 and 3.4 are due to the pressure profiles, but the pressure profiles may not be responsible for the deviations from the corresponding plane wall cases. A heat/heat analogy is developed to see the effects of thermal boundary conditions. With the only difference being the thermal boundary conditions, this analogy function examines a possibility of a conversion of fluxbc heat transfer data to levelbc heat transfer data for nonzero pressure gradients. If this analogy function happened to be completely a flat distribution, the conversion would be very simple. However, this has not been the case. The deviation from the corresponding plane wall factor of in this case is larger than the deviation of line 2/1 in Figs. 3.2, 3.3 and 3.4 from its corresponding plane wall factor of This implies, for laminar boundary layers, that a mass transfer experiment with naphthalene sublimation is going to be more accurate than a fluxbc heat transfer 45
27 experiment since the boundary condition in an actual gas turbine heat transfer is considered to be a uniform level boundary condition. Finally, a few thoughts are given to the analogy function in the regions of flow separation and transition. It should be interesting and useful to uncover how the analogy function behaves under such conditions. The present study suggests that both numerical and experimental investigations could be done for this purpose, and the experimental approach is pursued in the next chapter. 46
Basic Equations, Boundary Conditions and Dimensionless Parameters
Chapter 2 Basic Equations, Boundary Conditions and Dimensionless Parameters In the foregoing chapter, many basic concepts related to the present investigation and the associated literature survey were
More informationBlasius solution. Chapter 19. 19.1 Boundary layer over a semiinfinite flat plate
Chapter 19 Blasius solution 191 Boundary layer over a semiinfinite flat plate Let us consider a uniform and stationary flow impinging tangentially upon a vertical flat plate of semiinfinite length Fig
More informationModule 2 : Convection. Lecture 20a : Illustrative examples
Module 2 : Convection Lecture 20a : Illustrative examples Objectives In this class: Examples will be taken where the concepts discussed for heat transfer for tubular geometries in earlier classes will
More information3 Numerical Methods for Convection
3 Numerical Methods for Convection The topic of computational fluid dynamics (CFD) could easily occupy an entire semester indeed, we have such courses in our catalog. The objective here is to eamine some
More informationIntroduction to Fluid Mechanics. Chapter 9 External Incompressible Viscous Flow. Pritchard
Introduction to Fluid Mechanics Chapter 9 External Incompressible Viscous Flow Main Topics The BoundaryLayer Concept BoundaryLayer Thicknesses Laminar FlatPlate Boundary Layer: Exact Solution Momentum
More informationHEAT TRANSFER AUGMENTATION IN PLATE FINNED TUBE HEAT EXCHANGERS WITH VORTEX GENERATORS: A COMPARISON OF ROUND AND FLAT TUBES *
IJST, Transactions of Mechanical Engineering, Vol. 37, No. M1, pp 3951 Printed in The Islamic Republic of Iran, 2013 Shiraz University HEAT TRANSFER AUGMENTATION IN PLATE FINNED TUBE HEAT EXCHANGERS WITH
More informationHEAT TRANSFER CODES FOR STUDENTS IN JAVA
Proceedings of the 5th ASME/JSME Thermal Engineering Joint Conference March 1519, 1999, San Diego, California AJTE996229 HEAT TRANSFER CODES FOR STUDENTS IN JAVA W.J. Devenport,* J.A. Schetz** and Yu.
More informationChapter 1. Governing Equations of Fluid Flow and Heat Transfer
Chapter 1 Governing Equations of Fluid Flow and Heat Transfer Following fundamental laws can be used to derive governing differential equations that are solved in a Computational Fluid Dynamics (CFD) study
More informationHEAT TRANSFER ANALYSIS IN A 3D SQUARE CHANNEL LAMINAR FLOW WITH USING BAFFLES 1 Vikram Bishnoi
HEAT TRANSFER ANALYSIS IN A 3D SQUARE CHANNEL LAMINAR FLOW WITH USING BAFFLES 1 Vikram Bishnoi 2 Rajesh Dudi 1 Scholar and 2 Assistant Professor,Department of Mechanical Engineering, OITM, Hisar (Haryana)
More informationHigh Speed Aerodynamics Prof. K. P. Sinhamahapatra Department of Aerospace Engineering Indian Institute of Technology, Kharagpur
High Speed Aerodynamics Prof. K. P. Sinhamahapatra Department of Aerospace Engineering Indian Institute of Technology, Kharagpur Module No. # 01 Lecture No. # 06 Onedimensional Gas Dynamics (Contd.) We
More informationCBE 6333, R. Levicky 1. Potential Flow
CBE 6333, R. Levicky Part I. Theoretical Background. Potential Flow Potential Flow. Potential flow is irrotational flow. Irrotational flows are often characterized by negligible viscosity effects. Viscous
More informationLecture 6  Boundary Conditions. Applied Computational Fluid Dynamics
Lecture 6  Boundary Conditions Applied Computational Fluid Dynamics Instructor: André Bakker http://www.bakker.org André Bakker (20022006) Fluent Inc. (2002) 1 Outline Overview. Inlet and outlet boundaries.
More informationChapter 8 Steady Incompressible Flow in Pressure Conduits
Chapter 8 Steady Incompressible Flow in Pressure Conduits Outline 8.1 Laminar Flow and turbulent flow Reynolds Experiment 8.2 Reynolds number 8.3 Hydraulic Radius 8.4 Friction Head Loss in Conduits of
More informationAA200 Chapter 9  Viscous flow along a wall
AA200 Chapter 9  Viscous flow along a wall 9.1 The noslip condition 9.2 The equations of motion 9.3 Plane, Compressible Couette Flow (Review) 9.4 The viscous boundary layer on a wall 9.5 The laminar
More informationA Guide to Calculate Convection Coefficients for Thermal Problems Application Note
A Guide to Calculate Convection Coefficients for Thermal Problems Application Note Keywords: Thermal analysis, convection coefficients, computational fluid dynamics, free convection, forced convection.
More informationHeat Transfer Prof. Dr. Ale Kumar Ghosal Department of Chemical Engineering Indian Institute of Technology, Guwahati
Heat Transfer Prof. Dr. Ale Kumar Ghosal Department of Chemical Engineering Indian Institute of Technology, Guwahati Module No. # 04 Convective Heat Transfer Lecture No. # 03 Heat Transfer Correlation
More informationFree Convection Film Flows and Heat Transfer
Deyi Shang Free Convection Film Flows and Heat Transfer With 109 Figures and 69 Tables < J Springer Contents 1 Introduction 1 1.1 Scope 1 1.2 Application Backgrounds 1 1.3 Previous Developments 2 1.3.1
More informationNUMERICAL ANALYSIS OF THE EFFECTS OF WIND ON BUILDING STRUCTURES
Vol. XX 2012 No. 4 28 34 J. ŠIMIČEK O. HUBOVÁ NUMERICAL ANALYSIS OF THE EFFECTS OF WIND ON BUILDING STRUCTURES Jozef ŠIMIČEK email: jozef.simicek@stuba.sk Research field: Statics and Dynamics Fluids mechanics
More informationTWODIMENSIONAL FINITE ELEMENT ANALYSIS OF FORCED CONVECTION FLOW AND HEAT TRANSFER IN A LAMINAR CHANNEL FLOW
TWODIMENSIONAL FINITE ELEMENT ANALYSIS OF FORCED CONVECTION FLOW AND HEAT TRANSFER IN A LAMINAR CHANNEL FLOW Rajesh Khatri 1, 1 M.Tech Scholar, Department of Mechanical Engineering, S.A.T.I., vidisha
More informationMass Transfer in Laminar & Turbulent Flow. Mass Transfer Coefficients
Mass Transfer in Laminar & Turbulent Flow Mass Transfer Coefficients 25 MassTransfer.key  January 3, 204 Convective Heat & Mass Transfer T T w T in bulk and T w near wall, with a complicated T profile
More informationChapter 7. External Forced Convection. Multi Energy Transport (MET) Lab. 1 School of Mechanical Engineering
Chapter 7 Eternal Forced Convection 1 School of Mechanical Engineering Contents Chapter 7 71 rag and Heat Transfer in Eternal Flow 3 page 72 Parallel Flow Over Flat Plates 5 page 73 Flow Across Cylinders
More informationInternal Convection: Fully Developed Flow
Internal Convection: Fully Developed Flow Laminar Flow in Circular Tube: Analytical local Nusselt number is constant in fully develop region depends on surface thermal condition constant heat flux Nu D
More informationFluent Software Training TRN Boundary Conditions. Fluent Inc. 2/20/01
Boundary Conditions C1 Overview Inlet and Outlet Boundaries Velocity Outline Profiles Turbulence Parameters Pressure Boundaries and others... Wall, Symmetry, Periodic and Axis Boundaries Internal Cell
More informationUniversity Turbine Systems Research 2012 Fellowship Program Final Report. Prepared for: General Electric Company
University Turbine Systems Research 2012 Fellowship Program Final Report Prepared for: General Electric Company Gas Turbine Aerodynamics Marion Building 300 Garlington Rd Greenville, SC 29615, USA Prepared
More informationPractice Problems on Boundary Layers. Answer(s): D = 107 N D = 152 N. C. Wassgren, Purdue University Page 1 of 17 Last Updated: 2010 Nov 22
BL_01 A thin flat plate 55 by 110 cm is immersed in a 6 m/s stream of SAE 10 oil at 20 C. Compute the total skin friction drag if the stream is parallel to (a) the long side and (b) the short side. D =
More informationHEAT TRANSFER IN BLOCK WALLS
HEAT TRANSFER IN BLOCK WALLS S. Hassid and E. Levinsky Environmental & Water Resources Engineering Department Technion  Israel Institute of Technology Haifa 32  Israel ABSTRACT Combined conductionconvectionradiation
More informationDifferential Relations for Fluid Flow. Acceleration field of a fluid. The differential equation of mass conservation
Differential Relations for Fluid Flow In this approach, we apply our four basic conservation laws to an infinitesimally small control volume. The differential approach provides point by point details of
More informationME 144: Heat Transfer Convection Relations for External Flows. J. M. Meyers
ME 144: Heat Transfer Convection Relations for External Flows Empirical Correlations Generally, convection correlations for external flows are determined experimentally using controlled lab conditions
More informationEffect of Aspect Ratio on Laminar Natural Convection in Partially Heated Enclosure
Universal Journal of Mechanical Engineering (1): 833, 014 DOI: 10.13189/ujme.014.00104 http://www.hrpub.org Effect of Aspect Ratio on Laminar Natural Convection in Partially Heated Enclosure Alireza Falahat
More informationRavi Kumar Singh*, K. B. Sahu**, Thakur Debasis Mishra***
Ravi Kumar Singh, K. B. Sahu, Thakur Debasis Mishra / International Journal of Engineering Research and Applications (IJERA) ISSN: 4896 www.ijera.com Vol. 3, Issue 3, MayJun 3, pp.76677 Analysis of
More informationComparison of Heat Transfer between a Helical and Straight Tube Heat Exchanger
International Journal of Engineering Research and Technology. ISSN 09743154 Volume 6, Number 1 (2013), pp. 3340 International Research Publication House http://www.irphouse.com Comparison of Heat Transfer
More informationNumerical Investigation of Heat Transfer Characteristics in A Square Duct with Internal RIBS
merical Investigation of Heat Transfer Characteristics in A Square Duct with Internal RIBS Abhilash Kumar 1, R. SaravanaSathiyaPrabhahar 2 Mepco Schlenk Engineering College, Sivakasi, Tamilnadu India 1,
More informationNatural Convection. Buoyancy force
Natural Convection In natural convection, the fluid motion occurs by natural means such as buoyancy. Since the fluid velocity associated with natural convection is relatively low, the heat transfer coefficient
More informationModule 1 : Conduction. Lecture 5 : 1D conduction example problems. 2D conduction
Module 1 : Conduction Lecture 5 : 1D conduction example problems. 2D conduction Objectives In this class: An example of optimization for insulation thickness is solved. The 1D conduction is considered
More informationNUMERICAL AND EXPERIMENTAL ANALYSIS OF ICE MELTING IN WATER
0HFiQLFD&RPSXWDFLRQDO9RO;;,SS± 5,GHOVRKQ9(RQ]RJQLDQG$&DUGRQD(GV DQWD)H±3DUDQi$UJHQWLQD2FWREHU NUMERICAL AND EXPERIMENTAL ANALYSIS OF ICE MELTING IN WATER Cristian A. Peña, Marcela A. Cruchaga and Diego
More informationFluid Mechanics Prof. T. I. Eldho Department of Civil Engineering Indian Institute of Technology, Bombay. Lecture No. # 36 Pipe Flow Systems
Fluid Mechanics Prof. T. I. Eldho Department of Civil Engineering Indian Institute of Technology, Bombay Lecture No. # 36 Pipe Flow Systems Welcome back to the video course on Fluid Mechanics. In today
More informationLaminar Flow and Heat Transfer of HerschelBulkley Fluids in a Rectangular Duct; FiniteElement Analysis
Tamkang Journal of Science and Engineering, Vol. 12, No. 1, pp. 99 107 (2009) 99 Laminar Flow and Heat Transfer of HerschelBulkley Fluids in a Rectangular Duct; FiniteElement Analysis M. E. SayedAhmed
More informationDistinguished Professor George Washington University. Graw Hill
Mechanics of Fluids Fourth Edition Irving H. Shames Distinguished Professor George Washington University Graw Hill Boston Burr Ridge, IL Dubuque, IA Madison, Wl New York San Francisco St. Louis Bangkok
More informationDimensional analysis is a method for reducing the number and complexity of experimental variables that affect a given physical phenomena.
Dimensional Analysis and Similarity Dimensional analysis is very useful for planning, presentation, and interpretation of experimental data. As discussed previously, most practical fluid mechanics problems
More informationdu u U 0 U dy y b 0 b
BASIC CONCEPTS/DEFINITIONS OF FLUID MECHANICS (by Marios M. Fyrillas) 1. Density (πυκνότητα) Symbol: 3 Units of measure: kg / m Equation: m ( m mass, V volume) V. Pressure (πίεση) Alternative definition:
More informationNUMERICAL INVESTIGATIONS ON HEAT TRANSFER IN FALLING FILMS AROUND TURBULENCE WIRES
NUMERICAL INVESTIGATIONS ON HEAT TRANSFER IN FALLING FILMS AROUND TURBULENCE WIRES Abstract H. Raach and S. Somasundaram Thermal Process Engineering, University of Paderborn, Paderborn, Germany Turbulence
More information1 The basic equations of fluid dynamics
1 The basic equations of fluid dynamics The main task in fluid dynamics is to find the velocity field describing the flow in a given domain. To do this, one uses the basic equations of fluid flow, which
More informationME 239: Rocket Propulsion. Nozzle Thermodynamics and Isentropic Flow Relations. J. M. Meyers, PhD
ME 39: Rocket Propulsion Nozzle Thermodynamics and Isentropic Flow Relations J. M. Meyers, PhD 1 Assumptions for this Analysis 1. Steady, onedimensional flow No motor start/stopping issues to be concerned
More informationThis chapter describes how you can model solidification and melting in FLUENT. Information is organized into the following sections:
Chapter 21. Melting Modeling Solidification and This chapter describes how you can model solidification and melting in FLUENT. Information is organized into the following sections: Section 21.1: Overview
More informationHeat Transfer From A Heated Vertical Plate
Heat Transfer From A Heated Vertical Plate Mechanical and Environmental Engineering Laboratory Department of Mechanical and Aerospace Engineering University of California at San Diego La Jolla, California
More informationNATURAL/FREE CONVECTION
NATURA/FREE CONVECTION Prabal Talukdar Associate Professor Department of Mechanical Engineering IIT Delhi Email: prabal@mech.iitd.ac.in Natural/free convection P.Talukdar/MechIITD Natural Convection
More informationDimensional Analysis
Dimensional Analysis An Important Example from Fluid Mechanics: Viscous Shear Forces V d t / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / Ƭ = F/A = μ V/d More generally, the viscous
More informationFluid Mechanics Prof. T.I. Eldho Department of Civil Engineering Indian Institute of Technology, Bombay. Lecture  22 Laminar and Turbulent flows
Fluid Mechanics Prof. T.I. Eldho Department of Civil Engineering Indian Institute of Technology, Bombay Lecture  22 Laminar and Turbulent flows Welcome back to the video course on fluid mechanics. So
More informationFLOW ANALYSIS OF EFFECT OF STRUTS IN AN ANNULAR DIFFUSER
FLOW ANALYSIS OF EFFECT OF STRUTS IN AN ANNULAR DIFFUSER 1, 2, 3 Raghul., DANUSHKOTTI., Nanda Gopal. B.E Student, Department of Mechanical Engineering, Velammal Engg College, Chennai ABSTRACT Some recent
More informationChapter 2. Derivation of the Equations of Open Channel Flow. 2.1 General Considerations
Chapter 2. Derivation of the Equations of Open Channel Flow 2.1 General Considerations Of interest is water flowing in a channel with a free surface, which is usually referred to as open channel flow.
More informationHWR 431 / 531 HYDROGEOLOGY LAB SECTION LABORATORY 2 DARCY S LAW
HWR 431 / 531 HYDROGEOLOGY LAB SECTION LABORATORY 2 DARCY S LAW Introduction In 1856, Henry Darcy, a French hydraulic engineer, published a report in which he described a series of experiments he had performed
More informationKeywords: Heat transfer enhancement; staggered arrangement; Triangular Prism, Reynolds Number. 1. Introduction
Heat transfer augmentation in rectangular channel using four triangular prisms arrange in staggered manner Manoj Kumar 1, Sunil Dhingra 2, Gurjeet Singh 3 1 Student, 2,3 Assistant Professor 1.2 Department
More informationEntrance Conditions. Chapter 8. Islamic Azad University
Chapter 8 Convection: Internal Flow Islamic Azad University Karaj Branch Entrance Conditions Must distinguish between entrance and fully developed regions. Hydrodynamic Effects: Assume laminar flow with
More informationPressure Measurements
Pressure Measurements Measurable pressures Absolute pressure Gage pressure Differential pressure Atmospheric/barometric pressure Static pressure Total Pressure Pressure Measurement Mechanical Pressure
More informationGas Turbine Engine Performance Analysis. S. Jan
Gas Turbine Engine Performance Analysis S. Jan Jul. 21 2014 Chapter 1 Basic Definitions Potential & Kinetic Energy PE = mgz/g c KE = mv 2 /2g c Total Energy Operational Envelopes & Standard Atmosphere
More informationAdaptation of General Purpose CFD Code for Fusion MHD Applications*
Adaptation of General Purpose CFD Code for Fusion MHD Applications* Andrei Khodak Princeton Plasma Physics Laboratory P.O. Box 451 Princeton, NJ, 08540 USA akhodak@pppl.gov Abstract Analysis of many fusion
More informationDevelopment of a Model for Wet Scrubbing of Carbon Dioxide by Chilled Ammonia
Development of a Model for Wet Scrubbing of Carbon Dioxide by Chilled Ammonia John Nilsson Department of Chemical Engineering, Lund University, P. O. Box 124, SE221 00 Lund, Sweden In this paper, the
More informationINTRODUCTION TO FLUID MECHANICS
INTRODUCTION TO FLUID MECHANICS SIXTH EDITION ROBERT W. FOX Purdue University ALAN T. MCDONALD Purdue University PHILIP J. PRITCHARD Manhattan College JOHN WILEY & SONS, INC. CONTENTS CHAPTER 1 INTRODUCTION
More informationHEAT TRANSFER AUGMENTATION THROUGH DIFFERENT PASSIVE INTENSIFIER METHODS
HEAT TRANSFER AUGMENTATION THROUGH DIFFERENT PASSIVE INTENSIFIER METHODS P.R.Hatwar 1, Bhojraj N. Kale 2 1, 2 Department of Mechanical Engineering Dr. Babasaheb Ambedkar College of Engineering & Research,
More informationWhat is Needed in Experimental Methods Instruction
What is Needed in Experimental Methods Instruction Perspective from a Government Laboratory Richard Anthony Rolf Sondergaard AFRL/PRTT Air Force Research Laboratory Propulsion Directorate Turbine Branch
More informationFlow Loss in Screens: A Fresh Look at Old Correlation. Ramakumar Venkata Naga Bommisetty, Dhanvantri Shankarananda Joshi and Vighneswara Rao Kollati
Journal of Mechanics Engineering and Automation 3 (013) 934 D DAVID PUBLISHING Ramakumar Venkata Naga Bommisetty, Dhanvantri Shankarananda Joshi and Vighneswara Rao Kollati Engineering Aerospace, MCOE,
More informationBoundary Conditions in Fluid Mechanics
Boundary Conditions in Fluid Mechanics R. Shankar Subramanian Department of Chemical and Biomolecular Engineering Clarkson University The governing equations for the velocity and pressure fields are partial
More informationHEAT TRANSFER ENHANCEMENT AND FRICTION FACTOR ANALYSIS IN TUBE USING CONICAL SPRING INSERT
HEAT TRANSFER ENHANCEMENT AND FRICTION FACTOR ANALYSIS IN TUBE USING CONICAL SPRING INSERT Rahul M. Gupta 1, Bhushan C. Bissa 2 1 Research Scholar, Department of Mechanical Engineering, Shri Ramdeobaba
More informationCommercial CFD Software Modelling
Commercial CFD Software Modelling Dr. Nor Azwadi bin Che Sidik Faculty of Mechanical Engineering Universiti Teknologi Malaysia INSPIRING CREATIVE AND INNOVATIVE MINDS 1 CFD Modeling CFD modeling can be
More informationLaminar flow in a baffled stirred mixer (COMSOL)
AALTO UNIVERSITY School of Chemical Technology CHEME7160 Fluid Flow in Process Units Laminar flow in a baffled stirred mixer (COMSOL) Sanna Hyvönen, 355551 Nelli Jämsä, 223188 Abstract In this simulation
More informationENSC 283 Introduction and Properties of Fluids
ENSC 283 Introduction and Properties of Fluids Spring 2009 Prepared by: M. Bahrami Mechatronics System Engineering, School of Engineering and Sciences, SFU 1 Pressure Pressure is the (compression) force
More informationDynamic Process Modeling. Process Dynamics and Control
Dynamic Process Modeling Process Dynamics and Control 1 Description of process dynamics Classes of models What do we need for control? Modeling for control Mechanical Systems Modeling Electrical circuits
More informationExperiment 3 Pipe Friction
EML 316L Experiment 3 Pipe Friction Laboratory Manual Mechanical and Materials Engineering Department College of Engineering FLORIDA INTERNATIONAL UNIVERSITY Nomenclature Symbol Description Unit A crosssectional
More informationEffect of Pressure Ratio on Film Cooling of Turbine Aerofoil Using CFD
Universal Journal of Mechanical Engineering 1(4): 122127, 2013 DOI: 10.13189/ujme.2013.010403 http://www.hrpub.org Effect of Pressure Ratio on Film Cooling of Turbine Aerofoil Using CFD Vibhor Baghel
More informationWhat is convective heat transfer?
What is convective heat transfer? A Combustion File downloaded from the IFRF Online Combustion Handbook ISSN 16079116 Combustion File No: 276 Version No: 1 Date: 29032004 Author(s): Source(s): Subeditor:
More informationConvective Mass Transfer
Convective Mass Transfer R. Shankar Subramanian Department of Chemical and Biomolecular Engineering Clarkson University We already have encountered the mass transfer coefficient defined in a manner analogous
More informationO.F.Wind Wind Site Assessment Simulation in complex terrain based on OpenFOAM. Darmstadt, 27.06.2012
O.F.Wind Wind Site Assessment Simulation in complex terrain based on OpenFOAM Darmstadt, 27.06.2012 Michael Ehlen IB Fischer CFD+engineering GmbH Lipowskystr. 12 81373 München Tel. 089/74118743 Fax 089/74118749
More informationENHANCEMENT OF HEAT TRANSFER USING WIRE COIL INSERTS WITH CHORD RIBS
ENHANCEMENT OF HEAT TRANSFER USING WIRE COIL INSERTS WITH CHORD RIBS 1 P.S.Desale, 2 N.C.Ghuge 1 PG Student, Heat Power, MCERC, Nasik (India) 2 Asst. Prof., Mech. Dept., MCERC,Nasik(India) ABSTRACT From
More informationChapter 8: Flow in Pipes
Objectives 1. Have a deeper understanding of laminar and turbulent flow in pipes and the analysis of fully developed flow 2. Calculate the major and minor losses associated with pipe flow in piping networks
More informationAbaqus/CFD Sample Problems. Abaqus 6.10
Abaqus/CFD Sample Problems Abaqus 6.10 Contents 1. Oscillatory Laminar Plane Poiseuille Flow 2. Flow in Shear Driven Cavities 3. Buoyancy Driven Flow in Cavities 4. Turbulent Flow in a Rectangular Channel
More informationModeling and Simulation of Axial Fan Using CFD Hemant Kumawat
Modeling and Simulation of Axial Fan Using CFD Hemant Kumawat Abstract Axial flow fans, while incapable of developing high pressures, they are well suitable for handling large volumes of air at relatively
More informationTurbulent Heat Transfer in a Horizontal Helically Coiled Tube
Heat Transfer Asian Research, 28 (5), 1999 Turbulent Heat Transfer in a Horizontal Helically Coiled Tube Bofeng Bai, Liejin Guo, Ziping Feng, and Xuejun Chen State Key Laboratory of Multiphase Flow in
More informationApplied Thermodynamics for Marine Systems Prof. P. K. Das Department of Mechanical Engineering Indian Institute of Technology, Kharagpur
Applied Thermodynamics for Marine Systems Prof. P. K. Das Department of Mechanical Engineering Indian Institute of Technology, Kharagpur Lecture  10 Steam Power Cycle, Steam Nozzle Good afternoon everybody.
More informationFundamentals of Fluid Mechanics
Sixth Edition. Fundamentals of Fluid Mechanics International Student Version BRUCE R. MUNSON DONALD F. YOUNG Department of Aerospace Engineering and Engineering Mechanics THEODORE H. OKIISHI Department
More informationExperimental Study On Heat Transfer Enhancement In A Circular Tube Fitted With U Cut And V Cut Twisted Tape Insert
Experimental Study On Heat Transfer Enhancement In A Circular Tube Fitted With U Cut And V Cut Twisted Tape Insert Premkumar M Abstract Experimental investigation of heat transfer and Reynolds number
More informationFREE CONVECTION FROM OPTIMUM SINUSOIDAL SURFACE EXPOSED TO VERTICAL VIBRATIONS
International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 1, JanFeb 2016, pp. 214224, Article ID: IJMET_07_01_022 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=7&itype=1
More informationFREESTUDY HEAT TRANSFER TUTORIAL 3 ADVANCED STUDIES
FREESTUDY HEAT TRANSFER TUTORIAL ADVANCED STUDIES This is the third tutorial in the series on heat transfer and covers some of the advanced theory of convection. The tutorials are designed to bring the
More informationis the stagnation (or total) pressure, constant along a streamline.
70 Incompressible flow (page 60): Bernoulli s equation (steady, inviscid, incompressible): p 0 is the stagnation (or total) pressure, constant along a streamline. Pressure tapping in a wall parallel to
More informationFLOW MEASUREMENT 2001 INTERNATIONAL CONFERENCE DERIVATION OF AN EXPANSIBILITY FACTOR FOR THE VCONE METER
FLOW MEASUREMENT 200 INTERNATIONAL CONFERENCE DERIVATION OF AN EXPANSIBILITY FACTOR FOR THE VCONE METER Dr D G Stewart, NEL Dr M ReaderHarris, NEL Dr R J W Peters, McCrometer Inc INTRODUCTION The VCone
More information1. (Problem 8.23 in the Book)
1. (Problem 8.23 in the Book) SOLUTION Schematic An experimental nuclear core simulation apparatus consists of a long thinwalled metallic tube of diameter D and length L, which is electrically heated
More informationME19b. SOLUTIONS. Feb. 11, 2010. Due Feb. 18
ME19b. SOLTIONS. Feb. 11, 21. Due Feb. 18 PROBLEM B14 Consider the long thin racing boats used in competitive rowing events. Assume that the major component of resistance to motion is the skin friction
More informationLecture 3 Fluid Dynamics and Balance Equa6ons for Reac6ng Flows
Lecture 3 Fluid Dynamics and Balance Equa6ons for Reac6ng Flows 3. 1 Basics: equations of continuum mechanics  balance equations for mass and momentum  balance equations for the energy and the chemical
More informationTHE EFFECTS OF DUCT SHAPE ON THE NUSSELT NUMBER
Mathematical and Computational pplications, Vol, No, pp 7988, 5 ssociation for Scientific Research THE EFFECTS OF DUCT SHPE ON THE NUSSELT NUMBER M Emin Erdoğan and C Erdem Imrak Faculty of Mechanical
More informationApplication of CFD Simulation in the Design of a Parabolic Winglet on NACA 2412
, July 24, 2014, London, U.K. Application of CFD Simulation in the Design of a Parabolic Winglet on NACA 2412 Arvind Prabhakar, Ayush Ohri Abstract Winglets are angled extensions or vertical projections
More informationExergy Analysis of a Water Heat Storage Tank
Exergy Analysis of a Water Heat Storage Tank F. Dammel *1, J. Winterling 1, K.J. Langeheinecke 3, and P. Stephan 1,2 1 Institute of Technical Thermodynamics, Technische Universität Darmstadt, 2 Center
More informationChapter 6 Energy Equation for a Control Volume
Chapter 6 Energy Equation for a Control Volume Conservation of Mass and the Control Volume Closed systems: The mass of the system remain constant during a process. Control volumes: Mass can cross the boundaries,
More informationViscous flow in pipe
Viscous flow in pipe Henryk Kudela Contents 1 Laminar or turbulent flow 1 2 Balance of Momentum  NavierStokes Equation 2 3 Laminar flow in pipe 2 3.1 Friction factor for laminar flow...........................
More informationHEAT TRANSFER AUGMENTATION IN A PLATEFIN HEAT EXCHANGER: A REVIEW
International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 1, JanFeb 2016, pp. 3741, Article ID: IJMET_07_01_005 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=7&itype=1
More informationA COMPUTATIONAL FLUID DYNAMICS STUDY ON THE ACCURACY OF HEAT TRANSFER FROM A HORIZONTAL CYLINDER INTO QUIESCENT WATER
A COMPUTATIONAL FLUID DYNAMICS STUDY ON THE ACCURACY OF HEAT TRANSFER FROM A HORIZONTAL CYLINDER INTO QUIESCENT WATER William Logie and Elimar Frank Institut für Solartechnik SPF, 8640 Rapperswil (Switzerland)
More informationEffective parameters on second law analysis for semicircular ducts in laminar flow and constant wall heat flux B
International Communications in Heat and Mass Transfer 32 (2005) 266 274 www.elsevier.com/locate/ichmt Effective parameters on second law analysis for semicircular ducts in laminar flow and constant wall
More informationANALYSIS OF FULLY DEVELOPED TURBULENT FLOW IN A PIPE USING COMPUTATIONAL FLUID DYNAMICS D. Bhandari 1, Dr. S. Singh 2
ANALYSIS OF FULLY DEVELOPED TURBULENT FLOW IN A PIPE USING COMPUTATIONAL FLUID DYNAMICS D. Bhandari 1, Dr. S. Singh 2 1 M. Tech Scholar, 2 Associate Professor Department of Mechanical Engineering, Bipin
More informationEffects of mass transfer processes in designing a heterogeneous catalytic reactor
Project Report 2013 MVK160 Heat and Mass Transport May 13, 2013, Lund, Sweden Effects of mass transfer processes in designing a heterogeneous catalytic reactor Maryneth de Roxas Dept. of Energy Sciences,
More informationHeat transfer in Flow Through Conduits
Heat transfer in Flow Through Conduits R. Shankar Suramanian Department of Chemical and Biomolecular Engineering Clarkson University A common situation encountered y the chemical engineer is heat transfer
More informationPrediction of airfoil performance at high Reynolds numbers
Downloaded from orbit.dtu.dk on: Jul 01, 2016 Prediction of airfoil performance at high Reynolds numbers. Sørensen, Niels N.; Zahle, Frederik; Michelsen, Jess Publication date: 2014 Document Version Publisher's
More informationIntegration of a fin experiment into the undergraduate heat transfer laboratory
Integration of a fin experiment into the undergraduate heat transfer laboratory H. I. AbuMulaweh Mechanical Engineering Department, Purdue University at Fort Wayne, Fort Wayne, IN 46805, USA Email: mulaweh@engr.ipfw.edu
More information