Experimental Performance of a Direct Evaporative Cooler Operating in Kuala Lumpur

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1 Int. J. of Therml & Environmentl Engineering Volume 6, No. 1 (2013) Experimentl Performnce of Direct Evportive Cooler Operting in Kul Lumpur Abdulrhmn Th. Mohmmd,b, Sohif Bin Mt, M.Y. Sulimn, K. Sopin, Abduljlil A. Al-bidi Solr Energy Reserch Institute, University Kebngsn Mlysi, Bngi, Selngor, Mlysi b Dept. of Mechnicl Engineering, Bqubh Technicl Institute, Foundtion of Technicl Eduction, Bghdd, Irq Abstrct The present work presents n experimentl investigtion on the performnce of direct evportive cooler in hot nd humid regions. The experimentl study is bsed on wether dt from Kul Lumpur, Mlysi. The direct evportive cooler consists of cellulose pd with surfce re per unit volume rtio of 100 m 2 /m 3. The performnce of the evportive cooler is evluted using the output temperture, sturtion efficiency, nd cooling cpcity. The output temperture of the ir vries between 27.5 C nd 29.4 C, while the cooling cpcity is between kw nd kw. Keywords: Evportive cooler, Sturtion efficiency, cooling cpcity. 1. Introduction Air conditioning identifies the conditioning of ir for mintining specific conditions of temperture, humidity, nd dust level inside n enclosed spce[1].evportive cooling is widely used in hot nd dry regions. Two common types of evportive cooling systems re the direct nd indirect systems. In the direct evportive cooler (DEC), the ir comes into direct contct with wter. The direct evportive cooling system dds moisture to the cool ir, while n indirect evportive cooling system (IEC) provides only sensible cooling to the processed ir without ny ddition of moisture. Therefore, the indirect evportive system is more ttrctive thn the direct evportive system. However, the cooling effectiveness is generlly low. Mny studies hve delt with the performnce of direct evportive cooling. In Indi, Kulkrni nd Rjput [2] mde theoreticl performnce nlysis of direct evportive cooling. Different mterils were considered in the nlysis; rigid cellulose, high density polythene, spen fiber nd corrugted pper mteril. The results of the nlysis showed tht the spen fiber mteril hd the highest efficiency of 87.5%, while the rigid cellulose mteril hd the lowest efficiency t 77.5%. The outlet temperture nd cooling cpcity vried between 28.8 C nd 26.5 C nd KJ/h nd KJ/h for the two mterils, respectively. Kchhwh nd Suhs [3] designed, fbricted, nd predicted the performnce of n evportive * Corresponding uthor. Tel.: Fx: ; E-mil: bd @gmil.com 2013 Interntionl Assocition for Shring Knowledge nd Sustinbility DOI: /ijtee medium. The pd thickness nd height were chieved for mximum cooling. Chengung nd Agwu[4] evluted the effect of speed nd the dry-bulb temperture of frontl ir, nd the temperture of the incoming wter on cooling performnce of direct evportive cooling combined with wetted medium. The results of the nlysis showed tht direct evportive cooling efficiency decresed with frontl ir velocity nd incoming wter temperture, nd incresed with frontl ir dry-bulb temperture. A simplified mthemticl model ws used by Foud nd Melikyn [5] to discuss the het nd mss trnsfer between the ir nd wter in direct evportive cooler. A comprison between the model results nd the experimentl results ws presented. The results indicte tht during stedy stte condition, the cooling efficiency is decresed by incresing the inlet frontl ir velocity, nd incresed by incresing the pd thickness. This is becuse the contct surfce between wter nd ir is incresed. Moien et l.[6] studied two-stge cooling system tht consisted of nocturnl rditive unit, cooling coil, nd n indirect evportive cooler. The investigtion ws conducted in wether conditions for the city of Tehrn. The results showed tht the first stge of the system incresed the effectiveness of the indirect evportive cooler. Also, the regenertive model provided the best comfort conditions. Di nd Sumthy[7] developed mthemticl model to predict nd discuss the interfce temperture of flling film in cross-flow direct evportive cooler. Anlysis results indicted tht the system performnce could be improved by optimizing the mss flow rtes of the feed wter nd processed ir, s well s the different dimensions of the pd. Wu et l.[8] proposed 15

2 simplified cooling efficiency bsed on the energy blnce nlysis of ir to nlyze the het nd mss trnsfer between ir nd wter film in the direct evportive cooler. The nlysis showed tht the frontl ir velocity nd thickness of the pd module re two key fctors influencing the cooling efficiency of direct evportive cooler. A model of the dew point evportive cooling system ws developed by Ringvilikul nd Kumr [9] to simulte the het nd mss trnsfer processes under vrious inlet ir conditions nd the influence of mjor operting prmeters. The model ws used to optimize the system prmeters nd to investigte the system effectiveness when operting under vrious inlet ir conditions. This pper ims to verify the experimentl results of direct evportive cooling system operting under hot nd humid climte conditions. 2. Experimentl setup The direct evportive cooling unit tht is used for this study consists minly of n exhust fn t the end of the unit nd re-circulting pump to drip wter on the upper side of the pd. As shown in Fig. 1, the ir enters the pd in horizontl configurtion. The evportive cooler is mde of stinless steel sheet; its height, length, nd width re 80 cm, 80 cm, nd 80 cm, respectively, nd it hs sump with dimensions, 66 cm long, 20 cm width, nd 25 cm depth. A cellulose pd is used s the pcking mteril with length of 71 cm, width of 71 cm nd thickness of 5 cm, s shown in Fig.1. The pcking is mde of cellulose sheets with specific surfce re of 100 m 2 /m 3 nd n equivlent dimeter of cm. loction. All these sensors re coupled with PC system to store the dt on computer. An ADAM-4018 dt logger ws used to collect sensor dt. This dt-cquisition system hs cpbility of 2 single-ended (6 differentil) voltge chnnels. Vrious single chnnel input re vilble in ADAM dt cquisition; thermocouple, mv, V, nd ma. The dt cquisition system smples dt every ten minutes from 2 thermocouple sensors, 2 humidity sensors, 1 nemometer nd 1 pyrometer. 4. Performnce prmeters A direct evportive cooler (DEC) is simple ir-conditioning system widely used in dry nd hot regions. The ir nd wter re in direct contct; the hot, dry ir psses over wet pd s surfces; the ir will lose its sensible het, thereby reducing its temperture. The performnce prmeters of DEC re clculted bsed on the following reltion: Sturtion efficiency is the rte between the rel decresing of the dry bulb temperture nd the mximum theoreticl decreses (dry bulb temperture would be equl to the wet bulb temperture of the inlet ir) s seen by Cmrgo et l. [10] nd [11]. ε DEC h = c A 1 exp w m Cp (1) Fig.2 shows the process of evporting cooling on psychometric chrt; this process is seen to be constnt wet bulb temperture process. The dry bulb temperture of the outlet ir cn be clculted s: Wtt nd Brown[12]. T = T ε ( T T ) 2 1 DEC 1 wb1 Cooling cpcity is given by: Q c = m Cp ( T 1 T 2) (2) (3) Fig.1. Photogrph of direct evportive cooling nd its pd 3. Mesurements nd instrumenttion Experimentl tests re crried out to evlute the performnce of the direct evportive cooling unit. To mesure the ir temperture nd reltive humidity t inlet nd outlet points of the evportive cooling unit, two thermocouples of type K with n ccurcy of ±0.1 C nd two humidity sensors (type TR- RH2W) with n ccurcy of ± 3% RH re instlled, respectively. One AM-402 nemometer is instlled t the inlet point of the evportive cooling unit to mesure the ir velocity. The mss flow rte of ir entering the evportive cooling unit is determined by using the ir velocity nd the cross-section re of the inlet duct. One Li-cor-2005Z Pyrometer is used to record the solr rdition in the test Fig. 2. Process of evporting cooling on psychometric chrt 16

3 5. Results nd Discussion The vlues of the experimentl test; dry-bulb temperture of the inlet nd outlet ir, solr rdition, sturtion efficiency, nd cooling cpcity re shown in Tble 1. During experimenttion, the inlet ir conditions were s follows: the dry bulb temperture 29.6 C to 36 C, the ir reltive humidity 42.5% to 81.1%, nd the solr rdition to W/m 2. The experimentl wether dt of Kul Lumpur is presented in Fig. 3. The verge ir velocity during the experiments ws 5.5 m/sec nd the wter mss flow rte ws 10 l/min. Fig. 4 represents the vrition of the dry bulb temperture between inlet ir temperture nd outlet ir temperture, nd it is noticed tht it ws possible to obtin the mximum temperture difference up to 7.6 C t reltive humidity of 42.5 %, nd the minimum temperture difference up to 2.1 C t reltive humidity of 81.1%. The vrition of cooling cpcity with the time of test is shown in Fig. 6. It is seen tht the cooling cpcity vries between 1.3 KW nd 5.3 KW. The mximum cooling cpcity is recorded t the time 1:50 PM, while the minimum cooling cpcity is recorded t the time 8:30 AM. From the results, the cooling cpcity is bsed on the drop in the dry bulb temperture of ir. Therefore it increses with the increse in the difference between the dry bulb tempertures t constnt ir mss flow rte. The outlet dry-bulb temperture hs direct effect on the sturtion efficiency of the evportive cooler. The vrition of sturtion efficiency with time is shown in Fig. 5, the efficiency rnges from 77.3% to 63.5%. The mximum sturtion efficiency ws recorded t the time 11:40 AM, with dry-bulb temperture nd reltive humidity of 34.8 C nd 52.7%, respectively. TIME (MINUTE) T 1 ( O C) Tble 1. Experimentl dt nd the performnce prmeters T WB T 2 ( O C) ( O C) SOLAR RADIATION W/M 2 EFFICIENCY (%) Q C (KW) 8: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : :

4 Fig. 3. Vrition solr rdition, dry-bulb temperture, nd reltive humidity with time Fig. 4. Vrition inlet nd outlet dry-bulb tempertures with time 18

5 Fig. 5. Vrition of sturtion efficiency with time Fig. 6. Vrition of cooling cpcity with time 19

6 6. Conclusions An experimentl study ws crried out to evlute the performnce of direct evportive cooler in humid regions. From the nlysis of the experimentl dt, the following conclusions cn be summrized: Experiments indicte tht dry bulb temperture decrese up to 7.6 C is obtinble by using direct evportive cooling unit in hot nd humid regions. Sturtion efficiency vries from 77.3% to 63.5 % nd cooling cpcity rnges from 1.384KW to KW. A direct evportive cooler my be mde to work in humid plces like Mlysi by drying the ir before the evportive process using the desiccnt dehumidifiction concept. Nomenclture A w Wetted re, m 2 Cp Specific het of ir, J/kg K h c m Q c T 1 T 2 T w1 Het trnsfer coefficient, W/m 2 K Air mss flow rte, kg/sec Cooling cpcity, kw Evportive inlet dry bulb temperture, o C Evportive outlet dry bulb temperture, o C Evportive inlet wet bulb temperture, o C Greek symbols ε Evportive sturtion efficiency (%) DEC Subscripts DEC DBT IEC RH Direct evportive cooler Dry bulb temperture Indirect evportive cooler Reltive humidity Acknowledgement The uthors re grteful to the stff of Solr Energy Reserch Institute/University Kebngsn Mlysi for their help. References [1] Essm E. Khlil. Energy-Efficiency in Air Conditioned Buildings: The Green Buildings Drem. Int. J. of Therml & Environmentl Engineering. 2011; 2: 9-18 [2] R. K. Kulkrni nd S. P.S. Rjput. Comprtive performnce of evportive cooling pds of lterntive mterils. IJAEST.2011; 10: [3] S. S. Kchhwh nd Suhs Prbhkr. Het nd mss trnsfer in direct evportive cooler. J. Sci. Ind. Res.2010; 69: [4] Chengung Sheng nd Agwu Nnnn. Empiricl correltion of cooling efficiency nd trnsport phenomen of direct evportive cooler. Appl. Therm. Eng. 2012; 40: [5] A.Foud nd Z. Melikyn. A simplified model for nlysis of het nd mss trnsfer in direct evportive cooler. Appl. Therm. Eng. 2011; 31: [6] Moien Frmhini, Ghssem Heidrinejd nd Shhrm Delfni. A two-stge system of nocturnl rditive nd indirect evportive cooling for conditions in Tehrn. Energy Build. 2010; 42: [7] Y.J. Di nd K. Sumthy. Theoreticl study on crossflow direct evportive cooler using honeycomb pper s pcking mteril. Appl. Therm. Eng. 2002; 22: [8] J.M. Wu, X. Hung nd H. Zhng. Theoreticl nlysis on het nd mss trnsfer in direct evportive cooler. Appl. Therm. Eng.2009; 29: [9] B. Ringvilikul nd S. Kumr. Numericl study of novel dew point evportive cooling system. Energy Build. 2010; 42: [10] J. R. Cmrgo, C. D. Ebinum nd J. L. Siveri. Experimentl performnce of direct evportive cooler operting during summer in Brzilin city. Int. J. Refrig. 2005; 28: [11] J. R. Cmrgo, E. Godoy Jr. nd C. D. Ebinum, An evportive nd desiccnt cooling system for ir conditioning in humid climtes. J. Brz. Soc. Mech. Sci. & Eng. 2005; XXVII: [12] Wtt R.J. nd Brown W. K. Evportive ir conditioning hnd book, third ed., the Firmne Press Inc.: Liburn GA, 1994; pp