COMPARATIVE STUDY OF THREE DIFFERENT ADSORBENT- ADSORBATE WORKING PAIRS FOR A WASTE HEAT DRIVEN ADSORPTION AIR CONDITIONING SYSTEM BASED ON SIMULATION

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1 COMPARATIVE STUDY OF THREE DIFFERENT ADSORBENT- ADSORBATE WORKING PAIRS FOR A WASTE HEAT DRIVEN ADSORPTION AIR CONDITIONING SYSTEM BASED ON SIMULATION 1 H. R. Ramj, 2 S. L. Leo, 1 I. A. W. Tan & 1 M. O. Abdullah 1 Faculty of Engneerng, Unverst Malaysa Sarawak, Kota Samarahan, East Malaysa 2 Internatonal College of Advanced Technology Sarawak (ICATS), Jalan Canna, Off Jalan Wan Alw, Tabuan Jaya, Kuchng, East Malaysa E-mal: amomar13@gmal.com ; amomar@feng.unmas.my ABSTRACT In a prevous study, a laboratory prototype of a thermal-drven adsorpton ar condtonng system employng actvated carbon as adsorbent and methanol as the rgerant was successfully developed. The expermental results employng the prototype obtaned a COP of 0.19 and coolng capacty Q of around 320 kj. The coolng power P yelded ~ 0.64 kw and t was able to produce chlled ar temperature T chll,out of around 22 C. In the present study, further works are conducted va smulaton to carry out what-f analyss vz. to determne the optmal adsorbentadsorbate workng par based on the prototype. Three types of rgerants, coupled wth actvated carbon, were consdered n ths study, namely (1) methanol (smlar to the expermental works); (2) ammona; and (3) water. The smulaton results obtaned showed that actvated carbon-water par produced the best coolng compared to actvated carbon-methanol and actvated carbon-ammona workng pars, as far as present study s concerned. The methanol and ammona showed a COP of 0.37 and 0.4, respectvely. The average T chll,out produced by methanol was around 15 C whle the temperature produced by ammona was slghtly hgher around 19 C. The coolng capacty P for methanol and ammona showed a value of 0.65 kw and 0.50 kw, respectvely. Actvated carbon-water par smulated to yeld a hgher COP of 0.58 wth Q at 480 kj manly due to hgh heat of evaporaton, whch was able to produce average T chll,out of 12 C wth coolng power of approxmately 1 kw. Keywords: Adsorpton ar condtonng system; Actvated carbon; COP; Coolng power; Smulaton; Waste heat. 1. INTRODUCTION The recent European Unon drectve on moble ar condtonng (MAC) phases out system usng HFC-134a as rgerant on the EU market from 2008 onwards (Reference). Ths leads to other alternatve systems such as adsorpton ar condtonng system. Ar condtonng technology s requred to evolve due to the new envronmental regulatons whch are concernng about the depleton of the ozone layer thus causng global warmng. As a result, ths trend has led to a strong demand for a new ar condtonng technology (see e.g. Leo SL, Abdullah MO, 2009) [1]. As far as automobles are concerned, unfortunately, no workng adsorpton coolng system has been practcally run due to varous restrctons - n partcular due to szng and coolng capacty lmtatons (Abdullah et al, 2011) [2]. There were several prototypes of adsorpton rgeraton systems reported n lterature, most of whch were for ce makng ndustry and others were desgned for ar condtonng purposes. Wang et al. (2001) [3] have revewed an adsorpton rgerator drven wth a heat source temperature of 100 C. The rgerator could obtan specfc rgeraton power for 5.2 kg-ce /day per kg actvated carbon wth SCP of 150 W/kg adsorbent and a COP close to 0.5. In another study done by Wang et al. (2001) [3] on adsorpton solar ce maker, 5-7 kg-ce/day per square meter solar collector could be produced contnuously n well lghted condton, makng use of solar energy. Meanwhle Tso et al. (2012) [4] had developed a chller system powered by waste heat employng actvated carbonsodum slcate/calcum chlorde. The outcome was chlled water temperature of 9 C utlzng waste heat temperature of 85 C as drvng source. A COP and SCP of 0.65 and 380 W/kg-adsorbent were obtaned respectvely n ther study. The correspondng adsorpton-desorpton cycle tme of the operaton showed that one full cycle could be completed optmally n 360 seconds. Xa et al. (2009) [5] had performed an analyss on an adsorpton chller employng slca gel-water par wth a methanol evaporator for coolng purposes. They obtaned a COP of 0.39 wth the heat source temperature of 82.5 C, coolng water temperature of 30.4 C and the temperature of the chlled water produced was 12 C. Meanwhle, Sato et al. (1997) [6] had presented a multple-stage adsorpton ar condtonng system for vehcles. Although the effcency of the multple-stage adsorpton system was mproved, the sze of the system also ncreased 109

2 and ts control system became more complex. Zhang et al. (2000) [7] had descrbed an expermental ntermttent adsorpton coolng system drven by the waste heat of a desel engne. Zeolte 13X-water was used as the workng par and a fnned double-tube heat exchanger was used as the adsorber. The COP and specfc coolng power (SCP) of the system was 0.38 and 25.7 W/kg, respectvely. Wang et al, (2001) [8] had studed an adsorpton ar condtonng for a bus drven by waste heat from exhausted gases. The workng par for ths system was actvated carbon and ammona wth the coolng power of 2.58 kw and a COP of The actvated carbon was pressurzed to a densty of about 900 kg/m 3 to ft addtonal adsorbent nto the adsorber. The total weght of the two adsorbers was about 248 kg and occuped about 1.0 m 2. In another research by Lu et al, (2004) [9] t was presented n expermental studes on the practcal performance of an adsorpton ar condtonng system powered by exhausted heat from a desel locomotve. The system was ncorporated wth one adsorbent bed and utlzed zeolte and water as a workng par to provde chlled water for condtonng the ar n the drver s cab of the locomotve. Ther expermental results showed that the adsorpton system was techncally feasble and could be appled for space ar condtonng. Under typcal runnng condtons, the average rgeraton power rangng from 3.0 to 4.2 kw has been obtaned. However, ths system mght not be sutable for automoble applcaton due to ts sze and hgh regeneratve temperature. Accordng to Leo and Abdullah (2009) [1] for ther research fndngs on automoble adsorpton applcaton, the COP obtaned through expermentaton was approxmately Theoretcally the value was qute small compared to regular ar condtonng avalable n the market. In spte of ths, the value of specfc coolng power recorded was a promsng W/kg. Wth a cycle tme set at 20 mnutes, the average chlled ar produced was around 22.6 C. The prototype operated ntermttently between two adsorbers n order to retan the chlled ar along the 20 C temperature lne. Beng able to produce ths degree of ar condtonng, the coolng col temperatures could fall to a range of 9.5 C to 14.7 C. Now, ths paper s a contnuaton of study by Leo & Abdullah et al, (2009) [1] and Abdullah et al, (2011) [2] on adsorpton coolng system. In prevous papers, the authors had dscussed the basc prototype desgn and conducted several relevant expermentaton works. In ths paper, however, extended smulaton works by CFD are presented; ways to acheve better performance and mnmze unnecessary energy losses are also dscussed herewth. In attanng the specfed condton and coolng performance, subsequently, a comparatve study was carred out based on three workng pars (utlzng actvated carbon as adsorbent) where methanol, ammona, and water were employed as the adsorbate (or rgerant) n the adsorpton ar condtonng system. By varyng these dfferent pars, the correspondng varables such adsorpton rate, heat transfers and operatng cycle tme were obtaned. Subsequently, performance parameters such as coolng power, P; coolng capacty, Q; and COP for all the three workng pars were also modeled, smulated and analyzed. 2. EXPERIMENTAL SYSTEM SETUP AND DESCRIPTIONS In ths laboratory scale settngs, a four stroke Subaru Robn 5.0 Hp powered engne was used to supply hgh temperature fume gas. The exhaust gas produced by ths engne could easly reach temperature of mnmum 150 C. The engne was able to release a range of 150 C 200 C of fume gas temperature. Ths prototype comprsed of two dentcal adsorbers placed sde by sde, a condenser, an evaporator, and three coolng fans. The operaton of the adsorpton ar condtonng system s a perodc successon of adsorpton and desorpton processes. When the adsorbent s heated up n the frst adsorber, the rgerant vapour s desorbed and later condensed n the condenser, and the condensed lqud s then transferred to the evaporator. The rgerant vapour s readsorbed by the adsorbent n the second adsorber n the cool down process. The coolng down process s asssted by three coolng fans placed at ther desgnated locatons. The schematc dagram of the prototype durng operaton s gven n Fgure

3 Fg. 1 The prototype schematc durng operaton [10] In ths prototype, the adsorber was desgned to ntensfy the heat and mass transfer of the adsorbent bed and maxmze the quantty of actvated carbon to be packed. The adsorber had a length of 40 cm, a wdth of 20 cm and a heght of 10 cm. The rgerant flud flew through the nternal channels of the tubes. A total of 1.6 kg of ol palm shell derved granular actvated carbon was packed between the fns of the tubes. The partcle sze of the actvated carbon was <3.0 mm, wth surface area of m 2 /g, total pore volume of cm 3 /g, densty of g/cm 3 and odne number of The heat of adsorpton of the actvated carbon was 1800 kj/kg. Ar fnned tube alumnum heat exchangers were used as the condenser and the evaporator. Though for the evaporator a hangng type was chosen to provde better coolng nstead. These heat exchangers were attached wth a 12V dc fan to ncrease the heat rejecton rate to the surroundng and thus ncreasng the coolng effect. The evaporator that served as the heat absorpton component was used to remove heat from the space and also dehumdfcaton. The mosture contaned n the ar condensed at the evaporator col as the warmer ar travelled through the col. The temperature of the heat exchangng flud was measured at the entrance and the ext of the condenser and evaporator. The temperatures of the overall system and surroundng area were observed through thermal couples and thermal camera. Along sde the temperature, pressures were also measured n the adsorber, condenser and the evaporator. Fgure 2 shows the placement and ntegraton of the components n the prototype, whch conssts of two adsorbers, a blower, an evaporator attached to two blowers, a condenser attached to a fan, an expanson valve, four check valves, three three-way valves, an engne, and several ppe connectors. The detal desgn of the complete system was gven n the work of (Abdullah and Leo 2008) [10]. Fg. 2 The expermental rg [10] 111

4 Ths prototype generally worked n two man phases,.e. desorpton phase and adsorpton phase. Practcally the coolng effect was due to the adsorpton process; whle desorpton on the other hand worked as pre-coolng n the operaton as to prepare the adsorbent for the adsorpton process. Throughout ths process, desorpton and adsorpton had to work contnuously n a sutable tme lmt whch was often erred to as tme cycle. Hence, to acheve ths condton, an ntermttent operaton was desgned whereby two adsorbers of same desgn were used. The dea was that whenever one of the adsorber was undergong adsorpton, the second adsorber would undergo desorpton. Through ths scheme, a contnuous coolng could be provded by ths system. 3. PHYSICAL AND MATHEMATICAL MODEL 3.1 The adsorber The Dubnn-Astakhov (D-A) equaton that relates the concentraton and temperature s represented n the form of (Lu et al. 2004) [9]; n T x x 0 exp k 1 (1) T s Where x, represents the concentraton of methanol adsorbed n bed at the temperature of the adsorpton, T. T s represents the saturated temperature n the adsorber wth gven pressure, P. The saturated adsorpton capacty of the workng par s gven by x o. The parameter k and n are constants that vary wth dfferent workng par. 3.2 Mass and energy balance equaton Adsorpton rate The adsorpton process n ths system could be dvded nto two phases whch were desorpton (regeneraton) phase and also the adsorpton phase. In ths system, these two dentcally desgn adsorbers would be operatng ntermttently wth each other. The cycle tme would rely heavly on the adsorpton and desorpton rate of the system as gven n the equatons by Tso et al. (2012) [4]; Adsorpton: dx ads dt x ads K ( ) ads xads, eq xads (2) xads, eq ( xads, eq xads, o )exp( Kadst) (3) Desorpton: dx des dt x des K des ( x des ) (4) xdes, eq ( xdes, eq xdes, o )exp( Kdest) (5) Condenser and evaporator model In modelng the condenser and evaporator, several assumptons have been consdered as followng, 1. The workng flud was consdered always n thermodynamc equlbrum correspondng to ts saturaton condtons. 2. The saturated temperature depended on the nternal pressure of the workng equpments gven by Antone equaton wth parameter as shown n Table 1 [11]. 3. The rgerant contaned nsde the adsorbent was completely desorbed before shftng to adsorpton phase. 4. the entre rgerant flud flow rate comng from the condenser was nstantly evaporated. There would be no flud lost n between the processes. Every amount of rgerant desorbed n the frst adsorber would be transferred n completon to the next adsorber where adsorpton took place. Ths means; m xdesmac (6) 112

5 Table 1. Antone equaton for gvn rgerants Compounds Temperature range ( o C) A B C Methanol ( ) Ammona (-83-60) Water (0-150) Whle employng the usual energy equaton, the total heat power nput to the system ncludng the condenser and evaporator models can be presented as below: Total heat power nput P m C T T eg Condenser m c Evaporator h m p, eg ( eg, n eg, out ( Tdes Tcond ) hv, m arc p, ) ( T T p, ar out n c ( Tcond Tev ) m arc p, ( T T v, p, ar n out 3.3 System performance parameters Coolng power and coolng capacty The coolng output readngs of the prototype va experment were calculated from measurng the temperature dfference of the nlet and outlet of the chlled ar by ts flow rate and specfc heat (Lu et al. 2004) [9];. P exp m chllcp, art chll, n Tchll, out (10) The total coolng capacty would be: Q c P dt, exp exp (11) Whle n smulaton, coolng power could be obtaned theoretcally by: Qc, theo m qv, c p, T cond Tev (12) Hence, the total coolng capacty could be presented as; m ptheo q v, c p, T cond Tev t cyc1/ 2 Where q v, s the heat of evaporaton for methanol, and t cyc1/2 s the half cycle tme of the whole operaton. ) ) (7) (8) (9) (13) Coeffcent of performance (COP) and specfc coolng power (SCP) The performance of the adsorpton coolng system s commonly evaluated usng two performance factors; the coeffcent of performance (COP) and specfc coolng power (SCP). In general, COP s the amount of coolng produced by an adsorpton coolng system per unt heat suppled [9] as shown: Q COP Q ev n The SCP, on the other hand, s defned as the rato between the coolng producton and the cycle tme per unt of adsorbent weght, as gven below [1]: SCP Q m ev ac Snce SCP relates to both the mass of adsorbent and the coolng power, t lects the sze of the system. For a nomnal coolng load, hgher SCP values ndcate the compactness of the system. (14) (15) 113

6 3.4 Governng equatons In smulaton, flud flow modelng descrbed by Segal and Howel (1992) [12] had been utlzed to solve the classc Naver-Stokes equatons by supermposng thousands of grd cells whch descrbe the physcal geometry of the ar flow and heat transfer, e; d v S (16) dt The transport equatons for mass conservaton, momentum and energy for any system are gven n these generc equatons (Segal and Howel (1992) [12], Abdullah et al. (2006) [13]: Contnuty: d du dt dx 0 Momentum: d v d dt dx v v j Energy: d cpt dt d dx c T dp d j dt dx P d dx k dt dx dp dt dp dx The smultaneous equatons were solved teratvely for each one of the cells to produce a soluton whch satsfed the conservaton law of mass, momentum and energy. In a prevous study, we had consdered double adsorber prototype desgn and reported the assocated smulaton works [16]; whle n the current study, a three dfferent adsober/adsorbent workng pars were beng nvestgated. 4. SIMULATION RESULTS AND ANALYSIS Durng the heatng process, rgerant was desorbed and pressurzed from the adsorber. Smultaneously, the adsorber was ntally prepared to contan 45 %, 26 % and 29 % of methanol, ammona and water, respectvely (n accordance to Eq.(1)). Theoretcally, the more rgerant were desorbed, the more coolng effect could be produced. Equvalently, the ablty of rgerant to be squeezed out of the adsorbent bed would ndcate the effectveness of the heat transfer processes of the system. In Fg. 3 (a), the dagram llustrates the early condton of the adsorber when the actvated carbon and rgerant were at room temperature around 30 C. Once the exhaust gas had entered the area, the heat of the exhaust gas vaporzed the rgerant wthn the actvated carbon. The pressurzed rgerant would be released from the adsorber due to pressure dfference, thus makng ts way to the evaporator. In ths condton the adsorber was n desorpton process. Whle n Fg. 3 (b), the adsorpton process took place at the same tme but on the second adsorber desorpton took place. The dagram shows that the source of heat was from the rgerant and actvated carbon sde. Ths heat was transferred to the cool ar blown by the blower to hasten the cool down process. (17) (18) (19) 114

7 Concentraton (kg/kg) IJRRAS 18 (2) February 2014 a) Refrgerant (l) Desorbed rgerant (v) Actvated Carbon Ambent Heat absorbed Exhaust gas From engne b) Adsorbed rgerant (l) Actvated Carbon rgerant (v) Ambent Hot Ar Heat absorbed Ar From blower Fg. 3 Smplfed (a) desorpton and; (b) adsorpton mechansm that occurs nsde the adsorber. The crcles represent the actvated carbon granular. The shaded regon ndcates the rgerant. The rato between adsorbate and adsorbent n ths system was set accordng to Eq. (1) provde. It was to be noted that an excess amount of adsorbate could cause over saturaton of actvated carbon that could lead to reducton of system performance (e.g. see Leo and Abdullah, 2009) [1]. 4.1 Adsorpton sobar In Fg. 4 the adsorpton sobars for the respectve workng pars are presented. The saturated temperature, T s used were correspondng to the saturated pressure, P s that were utlzed n expermental works by Leo and Abdullah (2009) [1]. In ths result T s mplemented was 45 C. Ths ndcated that the operatng pressure of the adsorber would depend on the adsorbate used. The saturated pressure P s was 0.09, 0.5 and 18 bar for actvated carbon-methanol, actvated carbon-water and actvated carbon-ammona par, respectvely. The parameters for the DA-equaton for each of the workng pars are gven n Table 2 [14]. 0.5 ac met ac ammo 0.25 ac water Temperature ( C) Fg. 4 Adsorpton sobar capacty for respectve workng par (ac= actvated carbon) 115

8 Concentraton (kg/kg) IJRRAS 18 (2) February 2014 Table 2 D-A equaton constant values for apponted workng par [13] Workng par k x 0 n Actvated carbon - methanol Actvated carbon - ammona Actvated carbon - water Adsorbate concentraton, x des aganst tme, t. The graphs n Fg. 5 were plotted to show the relatonshp of rgerant concentraton n the adsorber, x des durng desorpton phase aganst tme, t. In ths partcular smulaton settng, a constant exhaust gas nlet temperature, T eg,n of 200 C was used as the heat energy source. Desorpton temperature; T des was dentfed to be below 150 C throughout the process for all the workng pars. 0.4 ac met ac ammo 0.2 ac water Tme (s) Fg. 5 Concentraton of rgerant durng desorpton phase, x des aganst tme, t for respectve workng par (T eg,n = 200 C) The results showed that actvated carbon-ammona workng par had the shortest desorpton tme (around 420 sec) followed by water (480 sec) and methanol (600 sec). Ths could be explaned by the volatlty of the rgerant used. In comparson, ammona was the most volatle compound used then methanol and water when arranged n decreasng volatlty. Methanol took longer tme than water to be desorbed because of greater ntal concentraton, x o n the adsorber. 4.3 Influence of evaporatng temperature, T ev on chll temperature release, T chll,out and COP Fg. 6 shows the smulated chlled temperature release, T chll,out and COP of the system at dfferent evaporatng temperatures, T ev. Accordng to Fg. 6, T chll,out was lower at hgher T ev and t appled to all the rgerants used. In ths graph, t shows that actvated carbon-water workng par produced the lowest T chll,out n the range of 12 to 13 C. Ths was followed by methanol and ammona that acheved T chll,out of 15 to 17 C and 18 to 20 C, respectvely. Ths mpled that actvated carbon-water provded the best coolng profle. The results obtaned were based on the evaporator parameters gven n Table

9 T chll,out ( C) COP IJRRAS 18 (2) February COP, ac water T, ac ammo 15 T, ac met 0.5 COP, ac ammo 0.4 COP, ac met T, ac water T ev ( C) Fg. 6 Influence of evaporator temperature, T ev on chlled temperature release, T chll,out and coeffcent of performance for the system, COP. Table 3 Evaporator parameters T chll,n C p, ar m ar 30 o C 1.005kJ/kg. o C 0.045kg/s Fg. 6 also shows the effect of T ev on the system COP. The graph ndcated that when the T ev was ncreased, the COP of the system would slghtly ncrease as well. COP of the adsorber depended greatly on the coolng capacty, Q and also the cycle tme, t cyc of the operaton. Based on the graph, actvated carbon-water par yelded the hghest COP of Ths workng par also exhbted only slght changes to COP as a functon of T ev. Smultaneously, actvated carbon-ammona par had a COP of around 0.4 whle actvated carbon-methanol par yelded slghtly lower COP value of Influence of evaporatng temperature, T ev on coolng power, P and coolng capacty, Q. The smulated coolng power, P and coolng capacty, Q wth the nfluence of evaporator temperature, T ev s shown n Fg. 7. The graph depcted that when T ev was low, coolng power and coolng capacty were low as well. These two parameters were drectly proportonal to the T ev of the system. In the results obtaned from the smulaton, actvated carbon-water par produced the hghest P and Q of nearly 1 kw and 480 kj, respectvely. These results showed coherency towards the data obtaned for T chll,out and COP. The lowest P s obtaned from actvated carbonammona par that yelds only around 0.7 kw and Q n the range of 280 to 300 kj. Actvated carbon-methanol par exhbted a nearly equvalent Q but showed hgher value of P that was around 0.8 kw. The dfference was due to the effect of cycle tme, t cyc taken n gettng P values. By usng ammona as rgerant, the cycle tme was shorter than of methanol as shown n Fg. 5 and dscussed n secton 4.2. From the gradent of the graph, t was also shown that actvated carbon-methanol had the greatest effect to the changes of T ev

10 T chll,out ( C) P (kw) Q (kj) IJRRAS 18 (2) February P, ac water Q, ac water P, ac met 400 P, ac ammo Q, ac met 300 Q, ac ammo T ev ( C) Fg. 7 Influence of evaporator temperature, T ev on coolng power, P and coolng capacty, Q. 4.5 Chlled temperature released, T chll,out and coolng power, P of the adsorber aganst tme, t Fg. 8 shows the plot of chlled temperature released, T chll,out by the evaporator as a functon of tme, t. The graph depcted that n comparson of the three rgerants used, water was able to produce the lowest T chll,out. It was consdered here that lower T chll,out was more favorable n ths system. By usng water as rgerant, T chll,out produced could be down to 12 C whereas methanol and ammona could produce T chll,out around 15 C and 19 C, respectvely ac ammo ac met ac water Tme (s) Fg. 8 Chlled temperature release, T chll,out by the evaporator aganst tme, t for respectve workng par. In Fg. 9, the smulated coolng power, P of each workng par s plotted aganst tme, t. It was n coherence wth the results shown n Fg. 8, n whch actvated carbon-water exhbted the hghest P of up to 0.80 kw. It was followed by actvated carbon-methanol par that produced P at around 0.65 kw and actvated carbon-ammona par at 0.50 kw. Based on the results shown n both Fgs 8 and 9, t could be concluded that ths was due to the dfferent values n the heat of vaporzaton of the rgerant, H v. In comparson, water possessed the hghest H v followed by methanol and ammona. 118

11 Coolng Power (kw) IJRRAS 18 (2) February ac water 0.6 ac met 0.4 ac ammo Tme (s) Fg. 9 Coolng power, P aganst tme, t for the respectve workng par. 5. DISCUSSIONS In the adsorpton rgeraton system, workng pars are the most crucal part to be consdered. Accordng to Wang et al. (2010) [15] explanng the basc prncple and workng characterstcs of the adsorpton rgeraton system, the adsorbent should have the characterstcs of; 1. large adsorpton capacty 2. large change of adsorpton capacty wth temperature varaton 3. flat desorpton sotherm 4. good compatblty wth rgerant Smlarly n vapor compresson rgeraton system, rgerant should exhbt the qualty of; 1. large latent heat per volume 2. rght freezng pont and saturaton vapour pressure 3. good thermal stablty Based on the gven crtera, the workng pars for adsorpton system were decded. Currently there are no workng pars that completely meet the requrements mentoned. But the commonly used workng pars closely meet these condtons [15]. Theore, the workng pars such as actvated carbon-methanol, actvated carbon-ammona and actvated carbon-water were tested n the adsorpton system desgned by Leo and Abdullah (2009) [1] for real lfe mplementaton. After caul selecton of the sutable workng pars guded by the prerequste as lsted n the precedng paragraph extracted from Wang et al. (2010) [15], the performance parameters smulated n the present study are now summarzed n Table 4. The results showed that actvated carbon water par had gven the most desrable results wth the best coolng n terms of COP, coolng power, cycle tme and average chlled temperature. Table 4 Comparson of adsorber performance for the three workng pars utlzng dfferent adsorbents Adsorbent/Refrgerant Methanol(Exp) Methanol(Sm) Ammona Water Mass of adsorbent, m (g) Cycle tme, t cyc (s) Average chlled temperature produce, T chll,out ( o C) Coolng power, P (kw) Coolng capacty, Q (kj) Coeffcent of performance, COP

12 6. CONCLUSIONS Based on the smulaton results, t was found that actvated carbon-water workng par would be the perred adsorbent-adsorbate to be utlzed n ths adsorpton ar condtonng system. The actvated carbon-water par produced the optmal coolng compared to methanol and ammona as far as the range of parameters n the study was concerned. The methanol and ammona showed a COP of 0.37 and 0.4, respectvely. T chll,out produced by methanol was around 15 C whle the value produced by ammona was slghtly hgher around 19 C. The coolng capacty, P for methanol and ammona showed a value of 0.65 kw and 0.50 kw, respectvely. Meanwhle, actvated carbonwater par yelded a COP of 0.58 wth Q at 480 kj. Ths system was able to produce T chll,out of 12 C wth coolng power of approxmately 1kW. 7. REFRENCES [1]. S.L. Leo, M.O. Abdullah. Expermental study of an automoble exhaust heat-drven adsorpton arcondtonng laboratory prototype by usng palm actvated carbon-methanol. HVAC&R Res 16(2) (2010) [2]. M.O. Abdullah, I.A.W. Tan, S.L. Leo. Automoble adsorpton ar-condtonng system usng ol palm bomass-based actvated carbon: A revew. Renew. Sust. Energy Rev. 15 (2011) [3]. R.Z. Wang. Adsorpton rgeraton research n Shangha Jao Tong Unversty. Renew Sust. Energy Rev. 5 (2001) 1-37 [4]. C.Y. Tso, C.Y.H. Chao, S.C. Fu. Performance analyss of a waste heat drven actvated carbon composte adsorbent water adsorpton chller usng smulaton model. Int. J. of Heat and Mass Transfer 55 (2012) [5]. Z.Z. Xa, R.Z. Wang, D.C. Wang, Y.L. Lu, J.Y. Wu, C.J. Chen. Development and comparson of two-bed slca gel-water adsorpton chllers drven by low grade heat source, Int. J. Therm. Sc. 48 (2009) [6]. H. Sato, S. Honda, H. Tanaka, T. Terao. Adsorptve type rgeraton apparatus. US patent (1997). [7]. L.Z. Zhang. Desgn and testng of a waste heat adsorpton coolng system. Appl. Therm. Eng. 20(1) (2000) [8]. R.Z. Wang, W. Wang, T.F. Qu. Research and development on waste heat drven adsorpton bus ar condtonng system. Fnal Report SJTU-UTRC Jont Reserch Program, Shangha Jao Tong Unversty (SJTU) and Unted Technologes Research Center (UTRC), Chna (2001) [9]. Y.Z. Lu, R.Z. Wang, M. Zhang, S. Jangzhou. Adsorpton cold storage system system wth zeolte-water workng par used for locomotve ar condtonng. Energy Convers Manage. 44(10) (2003) [10]. M.O. Abdullah, S.L. Leo. Heat drven adsorpton ar-condtonng system for automoble. Malaysan Patent Number: PI ; MY A (2009) [11]. R.M. Felder, R.W. Rousseau. Elementary Prncples of Chemcal Processes, thrd ed., John Wley & Sons, Inc. 2000, pp [12]. R. Segal, J.R. Howel. Thermal Radaton Heat Transfer, thrd ed., Hemspher, New York, 1992 (Chapter 7). [13]. M.O. Abdullah, F.A. Mke, C.Y. Lam. Dryng performance and thermal transent study wth solar radaton supplemented by force-ventlaton. Int. J. of Therm. Sc. 45 (2006) [14]. A.C. Deshpande, R.M. Plla. Adsorpton ar condtonng (AdAC) for automobles usng waste heat recovered from exhaust gases. 2 nd Int. Conference on Emergng Trends n Eng. and Tech. (2009) ICETET-09 IEEE [15]. D.C. Wang, Y.H. L, D. L, Y.Z. Xa, J.P. Zhang. A revew on adsorpton rgeraton technology and adsorpton deteroraton n physcal adsorpton systems. Renew. Sust. Energy Rev. 14 (2010) [16]. HR Ramj, SL Leo, MO Abdullah. Parametrc study and smulaton of a heat-drven adsorber for ar condtonng system employng actvated carbon methanol workng par Appled Energy, 113, , 120

13 NOMENCLATURE A cross sectonal area (m 2 ) A lm log mean area C p specfc heat capacty (Jkg -1 K -1 ) COP coeffcent of performance h convectve coeffcent k constant n Dubnn equaton m mass (kg) P coolng Power (kw) Q coolng capacty (kj) q v vaporzaton heat SCP specfc coolng power T temperature ( C) t tme (s) x concentraton (kgkg -1 ) x o ntal concentraton (kgkg -1 ) Subscrpt ac ads cyc1/2 eg exp des ev o s v Superscrpt n actvated carbon adsorpton half cycle exhaust gas expermental desorpton phase evaporator nsde outsde rgerant (methanol) saturated vaporzaton constant n Dubnn equaton ACKNOWLEDGEMENT Ths present study was supported by the Mnstry of Hgher Educaton, Malaysa under Prototype Development Research Grant Scheme (PRGS), Contract No: PRGS/1/11/TK/UNIMAS/02/01. The authors would lke to thank all staff for ther contnuous encouragements throughout ths project. 121