Address for Correspondence

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1 Review Article HEAT EXCHANGER USING NANO FLUID Prof. Alpesh Mehta 1*, 2 Dinesh k Tantia, 3 Nilesh M Jha, 4 Nimit M Patel Address for Correspondence *1 Assistant Professor, Government Engineering College, Godhra 2,3,4 Students of 7th Semester Mechanical Government Engineering College, Godhra ABSTRACT This paper shows the research work on heat exchanger using nano fluid. In this paper we are using compact heat exchanger as heat transferring device while Al 2 O 3 as a nano fluid. The effect of the nano fluids on compact heat exchanger is analyzed by using ε NTU rating numerical method on turbo-charged diesel engine of type TBD 232V-12 cross flow compact heat exchanger radiator with unmixed fluids consisting of 644 tubes made of brass and 346 continuous fins made of copper. Comparative study of Al 2 O 3 + water nano fluids as coolant is carried out. KEY WORDS: heat exchanger, nano materials 1. INTRODUCTION Heat exchanger using nano fluid is a device in which the heat transfer takes place by using nano fluid. In this the working fluid is nano fluid. Nano fluid is made by the suspending nano particles in the fluid like water, ethylene glycol and oil, hydrocarbons, fluorocarbons etc. 1.1 Introduction to nano fluid Nano fluids are dilute liquid suspended nano particles which have only one critical dimension smaller than ~100nm. Much research work has been made in the past decade to this new type of material because of its high rated properties and behaviour associated with heat transfer (Masuda et al. 1993; Choi 1995), mass transfer (Krishnamurthy et al. 2006, Olle et al. 2006). The thermal behaviour of nano fluids could provide a basis for an huge innovation for heat transfer, which is a major importance to number of industrial sectors including transportation, power generation, micromanufacturing, thermal therapy for cancer treatment, chemical and metallurgical sectors, as well as heating, cooling, ventilation and air-conditioning. Nano fluids are also important for the production of nano structured materials (Kinloch et al. 2002), for the engineering of complex fluids (Tohver et al. 2001), as well as for cleaning oil from surfaces due to their excellent wetting and spreading behaviour (Wasan & Nikolov 2003) History of nano fluid The twenty-first century is an era of technological development and has already seen many changes in almost every industry. The introduction of nano science and technology is based on the famous phrase "There's Plenty of Room at the Bottom" by the Nobel Prize-winning physicist Richard Feynman in Feynman proposed this concept using a set of conventional-sized robot arms to construct a replica of themselves but one-tenth the original size then using that new set of arms to manufacture a even smaller set until the molecular scale is reached. 1.2 Introduction to heat exchanger Heat exchanger is nothing but a device which transfers the energy from a hot fluid medium to a cold fluid medium with maximum rate, minimum investment and low running costs History of heat exchanger In the 1950s, aluminium heat exchangers made moderate inroad in the automobile industry with the invention of the vacuum brazing technique, large scale production of aluminium-based heat exchangers began to raise and grow resulting from advantages of the controlled atmosphere brazing process (Nocolok brazing process introduced by ALCAN). With increasing years introduction of long life (highly corrosion resistant) alloys further improved performance characteristics of aluminium heat exchangers. Extra demands for aluminium heat exchangers increased mainly due to the growth of automobile air-conditioning systems About heat exchanger The heat transfer in a heat exchanger involves convection on each side of fluid and conduction taking place through the wall which is separating the two fluids. In a heat exchanger, the temperature of fluid keeps on changing as it passes through the tubes and also the temperature of the dividing wall located between the fluids varies along the length of heat exchanger. Examples: Boilers, super heaters, reheaters, airpreheaters. Radiators of an automobile. Oil coolers of heat engine. Refrigeration of gas turbine power plant. In waste heat recovery system. Types: 1. Direct contact type of heat exchanger, 2. Non contact type of heat exchanger. Direction of motion of fluid: 1. Parallel flow, 2. Counter flow 3. Mixed flow. 1.3 Analysis of heat exchanger The thermal analysis of heat exchanger is made by taking outlet temperature of fluid and it is then related to independent parameters as follows, T h,o, T c,o or q = f Six independent and one variable which may be T h,o, T c,o,or q dependent variable as given in the above equation for a given flow arrangement transferred into two independent and one dependent groups which are dimensionless. Nomenclature regarding Heat Exchanger By combining Differential energy conservation equations for the control volume we get dq = q"da = -C h dt h = C c dt c Where, sign depends upon whether dt c is increasing or decreasing with increasing da or dx (i.e cross sectional surface area and length).

2 The overall rate of heat transfer equation on a differential base for the surface area da is dq = q"da = U(T h - T c ) local da = U TdA Integrating the two above equations across the heat exchanger surface area, we get q = C h (T h,i T h,o ) = C c (T c,o - T c,i ) q = UA T m = Where, 3 rd parameter is the actual mean temperature difference that depends upon the exchanger flow arrangement and degree of fluid mixing within each fluid stream. Figure show a rectangular strip through which heat transfer takes place of surface area A in positive x direction, following figure 1 shows the Nomenclature of Heat Exchanger analysis of heat exchanger. Figure 1[27] Nomenclature of Heat Exchanger 1.4 Regarding nano fluid Heat conduction mechanisms in nano fluid Nano fluid is nothing but fluid particles which are less than even a micron(nearly 10-9 times smaller) in diameter and highly reactive and efficient material which can be used to increase factor like rate of reaction, thermal conductivity of any metal or material, they are that much reactive and strong. Keblinski [1] presented four possible methods in nano fluids which may contribute to thermal conduction. (a) Brownian motion of nano particles. (b) Liquid layering at the liquid/particle interface. (c) Ballistic nature of heat transport in nano particles. (d) Nano particle clustering in nano fluids. The Brownian motion of nano particles is too slow to transfer heat through a nano fluid. This mechanism works well only when the particle clustering has both the positive and negative effects of thermal conductivity which is obtained indirectly through convection Preparation of nano fluid The preparation of nano fluid is the first important step in using nano phase particles to change the heat transfer rate of conventional fluids. Nano fluids are mainly made up of metals, oxides, carbides and carbon nano tubes that can easily be dispensed in heat transferring fluids, such as water, ethylene glycol, hydrocarbons and fluorocarbons by addition of stabilizing agents. Nano particles can also be produced from several processes namely gas condensation, mechanical attribution or chemical precipitation. These nanoparticles can also be produced under cleaner conditions and their surface can be protected from unexpected coatings which may occur during the gas condensation process. The main limitation of such method is that the all particles made by this method occur with some incapability to produce pure metallic nano powders. The formation of such a problem can be reduced by using a direct evaporation condensation method [2, 3, and 4]. This method helps in controlling particle size and produces particles for stable nano fluids without surfactants or any electrostatic stabilizers, but has the disadvantage of oxidation of pure metals and low vapor pressure fluids. There are mainly four steps in the process of the direct evaporation - condensation method also known as one step method. 1. A cylinder containing a heat transferring fluid such as water or ethylene glycol is rotated inside so that a thin film of the fluid is constantly ejected out through the top of the chamber. 2. A piece of metallic material is evaporated by heating on a crucible as the source of the nano particles. 3. The fluid is allowed to cool at the bottom of the chamber to prevent any sort of unwanted evaporation. Another method for synthesis of nano fluid is the laser ablation method, which is used to produce alumina nano fluids [5]. Pure chemical synthesis is also an alternative method which has been used by Patel [6] to prepare gold and silver nanofluids. Zhu et al [7] also used one-step pure chemical synthesis method for preparing nanofluids using copper nano particles dispensed in ethylene glycol. There are basically four ways for the synthesis of nano fluids or important factors. They are basically, 1. Dispensing ability of nano particles 2. Stability factor of nano particles 3. Chemical compatibility associated to nano particles 4. Thermal stability of nano fluids Type of nano fluid There are different types of nano fluid; basically Al 2 O 3 + water CuO + water TiO + water CH 3 CH 2 OH + water Out of these we are going to use Al 2 O 3 & water as our nano fluid in heat exchanger Thermal Conductivity of (Al 2 O 3 + water) nano fluid The effect of base fluid on thermal conductivity is shown in Figure 2. The result in Figure 4 demonstrates that the thermal conductivity increment is least for the water-based nano fluids compared with that to of other nano fluids. This result is quite encouraging as heat transfer enhancement is often most required when poorer heat transfer fluids are involved. Figure 2 thus indicates that the thermal conductivity increment for the poorer heat transfer fluids compared to the fluids with better thermal conductivity such as water. Figure 2[28] Effect of temperature on thermal conductivity of Al2O3-based nanofluids

3 1.5.2 Experimental results on thermal conductivity of Al 2 O 3 - based nano fluids Alumina (Al 2 O 3 ) is the most commonly and widely used nano particle by many researchers during their experimental works. Efforts have been made to study the thermal conductivity of nano fluids. The effect of these experimental studies on the thermal conductivity of Al 2 O 3 -based nano fluids is given above in Table 1. Usually, thermal conductivity of Table 1[27] the nano fluids increases with increasing fraction in volume of nano particles; with decreasing particle size, the shape of such particles can also influence the thermal conductivity temperature of nano fluids, Brownian motion of the particle, and with the additives. Table 1 shows the selective summary of the thermal conductivity enhancement in Al 2 O 3 -based nanofluids. 2. LITERATURE REVIEW RELATED TO HEAT EXCHANGER USING NANO FLUID 2.1 Heat exchanger using nano fluid in counter flow direction Here we are using heat exchanger of counter flow direction type.tuckerman and Pease [9] are the first to introduce this idea by using micro channel heat sink (MCHS) as a source for cooling of electronic devices in the year They experimentally narrated the MCHS capability and claimed that they were able to dissipate heat flux at a rate of 790 W/cm 2. They showed that the convective heat transfer of single phase flows could be improved by decreasing the width of the heat sink channels and increasing wetted area by the heat transfer fluid. The experimental and analytical studies by Wang et al. [10], Lee et al. [11], Wang et al. [12] and Koo and Kleinstreuer [13] showed that nanofluid have a higher thermal conductivity than that of pure fluids and therefore has great affinity for heat transfer enhancement. Li and Xuan [14], Xuan and Li [15] and Pak and Cho [16] experimentally showed the convection heat transfer and pressure dropping for nano fluid tube flows. Their results show that heat transfer coefficient was greatly incremented and it depends upon factors like Reynolds number, particle size and shape, and particle volume fraction. They also found that nano particles did not cause an extra pressure drop. Another scientist named Donsheng and Yulog [17] studied practically the convective heat transfer of nanofluid made up of ã-al2o3- water, flowing through a tube made up of copper in the laminar flow region and showed a considerable enhancement of convective heat transfer using the nanofluids. The enhancement was particularly significant in the entrance region as it was higher than that obtained solely due to the enhancement on thermal conduction. Seok and Choi [18] investigated

4 numerically the cooling performance of micro channel heat sink with nanofluids. They showed that the cooling performance of a MCHS with water based nanofluids containing diamond (1% volume fraction and 2 nm) at the fixed pumping power of 2.25 W is enhanced by about 10% compared with that of a MCHS with water. Joescon and Issam [19] performed experiments to explore the micro channel cooling benefits of Al 2 O 3 -water nanofluid. They found that the high thermal conductivity of nano particles enhance the single phase heat transfer coefficient especially for laminar flow. Higher heat transfer coefficient was achieved mostly in the entrance region of the micro channels and the enhancement was weaker in the fully developed region, providing that nano particles have an appreciable effect on thermal boundary layer development. It was also observed that higher concentrations also produced greater sensitivity to heat flux. Mushtaq et al. [20] investigated the effect of channels geometry (the size and shape of channels) on performance of counter flow micro channel heat exchanger and used liquid water as a cooling fluid. They found that the effectiveness of heat exchanger and pressure drop were increased by decreasing the size of channels and claimed depending on the application of which type of heat exchanger is used. Mushtaq I. Hasan [21] numerically investigated the performance of counter flow micro channel heat exchanger with MEPCM suspension as a cooling fluid. He fund that using MEPCM suspension lead to improve thermal performance of CFMCHE but also lead to extra increase in pressure drop and resulting in decreasing the overall performance with using suspension as a cooling medium. For modelling, nano fluid is treated as a single-phase type fluid. This assumption can be used since the particles are ultra fine and they are easily fluidized [14,15]. Also, the particle volume fraction in nano fluid is usually low. Under such conditions the governing equations for the nano fluid flow and heat transfer are simplified and local fluid and particles are in thermal equilibrium. Schematic structure of the studied counter flow micro channel heat exchanger with square channels can be seen in Figure 3. Due to the geometrical and thermal symmetry between hot and cold channels rows, an individual heat exchanger unit consisting of two channels containing hot and cold fluids and a separating wall is considered as shown in Figure 4 will be used as a model figure to represent the complete counter flow micro channel heat exchanger since it gives an adequate indication about the performance and the heat is transferred from hot to cold fluid through a thick wall medium separating both fluids. Figure 3[29] A schematic model of the counter flow MCHE Figure 4[29] Schematic of Heat Exchange Unit 2.2 Compact heat exchanger using nano fluid The necessity of compact heat exchangers (CHEs) has been seen in fields like aerospace, automobile, gas turbine power plant and other industries for the last 50 years and more. This is mainly due to several factors such as packaging constraints, sometimes high performance requirements, low cost and using air or gas as one of the fluids in the exchanger. For nearly twenty years additional driving factors for heat exchangers design have been reducing energy consumption for operation of heat exchangers and process plants, and minimizing their overall capital investment. Figure 5 shows Heat Exchanger area densities and hydraulic diameters; S+THX - Shell and tube heat exchanger; PHE Plate heat exchanger; PFHE Plate fin heat exchanger; PCHE Printed circuit heat exchanger. Figure 5 [22] Heat Exchanger area densities and hydraulic diameters D.A. Reay [22] gives a general picture of the area density and typical hydraulic diameters of a range of conventional and CHE as shown in Fig. 4 and principal features in Table 2. Kays et al.[23] and Shah RK [24] defined CHE as having an area density which is greater than 700 m 2 /m 3 when operating in gas streams, and in excess of 300 m 2 /m 3 while operating in liquid or two phase streams. They gave different geometries surfaces of CHE: Plain fin, Louvered fin, Strip fin, Wavy fin, Pin fin and there designation. Compact Heat exchangers are becoming increasingly more and more important elements in many industrial processes worldwide, both in their original roles as contributors to increase energy efficiency and more recently as the basis for novel intensified unit operations, such as compact reactors based on PCHE fabrication techniques. CHEs, while accounting for 5 to 10% of the $15 billion plus worldwide market for heat exchangers, are seeing their sales increase up about by 10% per annum compared to 1 % for all other types of heat exchangers. Compact heat exchanger offer number of benefits which include: 2 Improved effectiveness 3 Smaller volumes 4 Multi-stream and multi-pass configurations

5 5 Tighter temperature controls 6 Power savings 7 Improved safety means protection Compact heat exchanger also deals with application of Al 2 O 3 + water nano fluid on compact heat exchanger in comparison with conventional coolants Why we use nano fluid The main goal or idea of using nano fluids is to attain highest possible thermal properties at the smallest possible concentrations (preferably<1% by volume) by uniform dispersion and stable suspension of nano particles (preferably<10 nm) in hot fluids. A nano fluid is a mixture of water and suspended metallic nano particles. Since the thermal conductivity of metallic solids are typically orders of magnitude higher than that of fluids it is expected that a solid/fluid mixture will have higher effective thermal conductivity compared to the base fluid. Nano fluids are extremely stable and exhibit no significant settling under static conditions, even after weeks or months Result and Analysis of Heat Exchanger. For the result analysis of heat exchanger there are several formulas related to the heat exchanger and the nano fluid Formula related to heat exchanger: There are basically 3 types for finding the result of heat exchanger that are: -NTU method, LMTD and MTD methods. In the -NTU method, the heat transfer rate from the hot fluid to the cold fluid in the heat exchanger is expressed in form as q= åc min (T h,i T h,o ) The -NTU method is different depending upon whether the shell fluid is the C min or C max fluid in the (stream asymmetric) flow arrangements used for shell-and-tube exchangers mostly. Formula related to LMTD method. LMTD = T 1 = T h,i T c,o, T 2 = T h,o T c,i Following Table 2 shows General Functional Relationships and Dimensionless Groups for å-ntu, P-NTU, and MTD Methods Table 2[27] a Although P,R and NTU 1 are defined on fluid side 1, it must be emphasized that all the result of the P- NTU and MID methods are valid if the definition of P,NTU and R are consistently based on C c, C 2,C k or C. b P and R are defined in P-NTU method Formula related to nano fluid The formula to determine the heat transfer coefficient of the Al 2 O 3 + H 2 O nano fluid in turbulent flow has been developed in previous study by Vasu et al. (25,26) it is found in good agreement with experimental data of standard Deviation 6.4% and Average deviation 5%. h nf = Where, = (Re nf ) 0.8 (Pr nf ) 0.4 for Al 2 O 3 + H 2 O Re nf = Pr nf = =ke m ( ) for Al 2 O 3 + H 2 O. This formula is used to calculate thermal conductivity for nano fluids (Vasu et al.,[26]) which is found to be in good agreement with the experimental data of standard deviation 4% and Average deviation of 2%. The other properties like viscosity, density and specific heat associated with nano fluids are calculated by using the following equations: = f ( ) =(1- ) f + p Cp nf = 3. ABOUT PROJECT WORK Up to now we have gone through Various Types Of heat exchanger from which we have selected Counter flow type with ( Al 2 O 3 + water ) as nano fluids. Although we have othe choice to use ethylene glycol + water, CuO + water, from which we have selected Al 2 O 3 + water. There are basically two types of methods of making nano fluid which is mention above. Our project is based on the nano fluids so our main aim is to find best, sutable and effective nano fluids which have work in any type of heat exchanger. 4. RESULT AND ANALYSIS We are using aluminum oxide with base fluid water, We are going to analysis efficiency and effectiveness by using LMTD method and NTU method. After the analysis we are deciding the cost of the nano fluid and whole manufacturing cost of the heat exchanger using nanofluid. 5. FUTURE SCOPE In Future, the next steps in the nanofluids research are to concentrate on the heat transfer enhancement and its physical mechanisms, taking into consideration such items as the optimum particle size and shape, particle volume concentration, fluid additives, particle coating and base fluid. Better characterization of nanofluids is also important for developing engineering designs based on the work of multiple research groups, and fundamental theory to guide this effort should be improved. Important features for commercialization must be addressed, including particle settling, particle agglomeration, surface erosion, and large scale nanofluid production at acceptable cost. Nanofluids offer challenges related to production, properties, heat transfer, and applications. In this section we highlight some future directions in each of these challenging areas. 1. Development of theoretical equations for thermo physical properties of CuO nanofluids is the grey area to be explored. 2. The effect of nanoparticles size on heat transfer and friction characteristics of nanofluids can be taken up for investigation. 3. Study on heat transfer investigation by changing the relative proportion in the base

6 fluid constituents can be taken up as future work. 4. The research work can be extended by considering the effect of thickness of the twisted tape inserts. 6. CONCLUSION By using the knowledge of making nano fluid and we get from literature review we are going to design and develop a Heat Exchanger by using nanofluids. We are also using design software to design heat exchanger. REFERENCES 1. Keblinst.P, Eastman.J.A and Cahill.D.G, Nano fluids for Thermal Transport Materials Today, 8 (2005), 6, pp Eastman J.A, Choi S.U.S, Li. S, Yu.W and Thompson L.J. Anomalously increased Effective thermal conductivities of ethylene glycol-based nanofluids conducting copper nanoparticles. Applied Physics Letters. 78(2001), 6, pp Das. S.K. Putra.N and Roetzel.W. Pool Boiling Characteristics of Nano fluids. International Journal of Heat and Mass transfer, 46 (2003), 5, pp Eastman.J.A,Cho.S.U.S,Li.S and Thompson.L.J, and Dimelfi.R.J, Thermal properties of Nano structured materials, Journal of Metastable Nano Crystalline Materials, 2 (1998), pp Tran.P.X and Soong.Y, Preparation of nanofluids using laser ablation in liquid technique, ASME Applied Mechanics and Material Conference, Austin, TX Patel.H.E, Das.S.K, Sundarrajan.T, Sreekumaran Nair.A, George.B and Pradeep.T, Thermalconductivities of naked and manolayer protected metal nanoparticle based Nanofluids, Manifestation of anomalous enhancement and chemical effects, Applied Physics Letters, 83(2003), 14, pp Zhu.H, Lin.Y and Yin.Y, A novel one step chemical method for preparation of copper Nanofluids, Journal of Colloid and Interface Science, 277 (2004), 1, pp Yu W, France DM, Routbort JL, Choi SUS: Review and comparison of nanofluid thermal conductivity and heat transfer enhancements. Heat Transfer Eng 2008, 29: D.B.Tuckerman and R.F.W.Pease High performance heat sinking for VLSI IEEE electron device letter. Vol2, Number 5, 1981, pp X. W. Wang, X. F. Xu and S. UConductivity of Nanoparticle-Fluid mixture, Journal of Thermophysics and Heat Transfer, Vol. 13, No. 4, 1999, pp S. Lee, S. U. S. Choi, S. Li and J. A. Estman, Measuring Thermal Conductivity of fluid containing Oxide Nanoparticles, Journal of Heat Transfer, Vol. 121, No. 2, 1999, pp B.-X.Wang, L.-P.Zhou and X.-F. Peng, A Fractal Model for Predicting the Effective Thermal Conductivity Liquid with Suspension of Nanoparticles, International Journal of Heat and Mass Transfer, Vol. 46, No. 14, 2003, pp J. Koo and C. Kleinstreuer, A New Thermal Conductivity Model for Nanofluids, Journal of Nanoparticle Resea Vol. 6, No. 6, 2004, pp Q. Li and Y. M. Xuan, Convective Heat transfer and Flow Characteristics of Cu -Water nanofluid, science in China Series E: Technological Sciences, Vol. 45, No. 4, 2002, pp Y. M. Xuan and Q. Li, Investigation on Convective Heat Transfer and Flow Feartures of Nanofluids, Journal of Heat Transfer, Vol. 125, No. 1, 2003, pp B. C. Pak and Y. I. Cho, Hydrodynamic and Heat Transfer Study of Dispersed Fluids with Submicron Metallic Oxide Particles, Experimental Heat Transfer, Vol. 11, No. 2, 1998, pp D. S. Wen and Y. L. Ding, Experimental Investigation into Convective Heat Transfer of Nanofluids at the Entrance Region under Laminar Flow Conditions, International Journal of Heat and Mass Transfer, Vol. 47, No. 24, 2004, pp S. P. Jang and S. U. S. Choi, Cooling Performance of a Microchannel Heat Sink with Nanofluids, Applied Thermal Engineering, Vol. 26, No , 2006, pp T.-H. Tsai and R. Chein, Performance Analysis of Nano-fluid-Cooled Microchannel Heat Sinks, Internantional Journal of Heat and Fluid Flow, Vol. 28, No. 5, 2007, pp J. Lee and I. Mudawar, Assessment of the Effectiveness of Nanofluids for Single-Phase and Two- Phase Heat Transfer in Micro-Channels, International Journal ofheat and Mass Transfer, Vol. 50, No. 3-4, 2007, pp M. I. Hasan, A. A. Rageb, M. Yaghoubi and H. Homayony, Influence of Channel Geometry on the Performance of Counter Flow Microchannel Heat Exchanger, International Journal of Thermal Sciences, Vol. 48, No. 8, 2009, pp Reay, D.A., Compact heat exchangers, enhancement and heat pump, International Journal of Refrigeration, vol. 25, 2002, pp Kays, W.H. & London, A.L, Compact Heat Exchangers, 3rd edition, 1984, McGrawHil. 24. Shah, R.K., Sekulic, D.P., Fundamentals of Heat Exchanger Design, 1st Edition, 2003, John Wiley & Sons.Inc. 25. Vasu, V., Rama, K.K., Kumar, A.C.S., Analytical prediction of forced convective heat transfer of fluids embedded with nanostructured materials (nanofluids), Pramana Journal of Physics, Vol.69, no.3, 2007, pp Vasu, V., Rama, K.K., Kumar, A.C.S., Empirical Correlations to predict thermophysical and heat transfer characteristics of Nanofluids, Thermal Science Journal, vol.12, no.3, Shah, R.K., Sekulic, D.P., Fundamentals of Heat Exchanger Design, 1st Edition, 2003, John Wiley & Sons.Inc. 28. Journal of Electronics Cooling and Thermal Control, 2012, 2, 35-43