Analysis on Parameters of Regeneration Subsystem in Liquid Desiccant Dehumidification Systems

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1 Purdue University Purdue e-pubs Interntionl Refrigertion nd Air Conditioning Conference School of Mechnicl Engineering 2014 Anlysis on Prmeters of Regenertion Subsystem in Liquid Desiccnt Dehumidifiction Systems Min Tu Chengqin Ren College of Mechnicl nd Vehicle Engineering, Hunn University, Chin, People's Republic of Hunxin Cheng Shool of Energy nd Power Engineering, Huzhong University of Science nd Technology,Chin, Hiji Lin Refrigertion Institute of Gree Electric Applinces, Inc. of Zhuhi, Chin, People's Republic of Follow this nd dditionl works t: Tu, Min; Ren, Chengqin; Cheng, Hunxin; nd Lin, Hiji, "Anlysis on Prmeters of Regenertion Subsystem in Liquid Desiccnt Dehumidifiction Systems" (2014). Interntionl Refrigertion nd Air Conditioning Conference. Pper This document hs been mde vilble through Purdue e-pubs, service of the Purdue University Librries. Plese contct for dditionl informtion. Complete proceedings my be cquired in print nd on CD-ROM directly from the Ry W. Herrick Lbortories t Herrick/Events/orderlit.html

2 2194, Pge 1 Anlysis on prmeters of regenertion subsystem in liquid desiccnt dehumidifiction systems Min Tu 1,3, Chengqin Ren 2, Hunxin Cheng 3, Hiji Lin 1 1 Refrigertion Institute of Gree Electric Applinces, Inc. of Zhuhi, Jinji West Rd., Zhuhi City, Gungdong Province, P. R. Chin Phone: , Fx: E-mil ddress: tu_iron_min@163.com 2 College of Mechnicl nd Vehicle Engineering, Hunn University, Chngsh City, Hunn Province, P.R. Chin; 3 Shool of Energy nd Power Engineering, Huzhong University of Science nd Technology, Wuhn City, Hubei Province, P. R. Chin ABSTRACT Along with the widely use in industries nd lives, the dehumidifiction systems hve consumed lrge mount of energy. Fortuntely, the ppliction of liquid desiccnt dehumidifiction system cn gretly reduce the consumption of high-grde energy. To improve the dvntges of liquid desiccnt system compred with the conventionl dehumidifiction system, one of the key mesures is to increse the efficiency of the regenertion sub-system. In this study, models for the regenertion tower nd counter-current het exchnger, which re recognized by previous experiments, re employed nd the corresponding VC++ computer progrm modules re used to describe the het nd mss trnsfer processes between the liquid desiccnt solution nd moist ir in the regenertor nd the het trnsfer process in het exchnger respectively. The orthogonl design is used to rrnge the numericl experiment. The results re nlyzed by the method of vrince nlysis to determine the reltive significnce of operting prmeters nd the interctions between them. The nlysis on the influence fctors shows tht for the evportion rte of wter vpor in the regenertor, the importnt prmeters re the inlet temperture nd concentrtion of the solution, the mss flow rtio of dry ir to dehydrted desiccnt, nd the NTU of the regenertor. The nlysis lso shows tht for the regenertion efficiency, the importnt prmeters re the mss flow rtio of dry ir to dehydrted desiccnt, the NTU of the regenertor nd the inlet temperture of solution. There is no interction tht influences the evportion rte of wter vpor nd the regenertion efficiency significntly. 1. INTRODUCTION The dehumidifiction systems hve been widely used in industril nd griculturl production nd people s lives. Every yer lrge quntity of energy is consumed to dehumidify the rw mterils nd end products in industril nd griculturl production (Lowenstein, 2005). Besides, dehumidifiction plys n importnt role in mking helthy nd comfortble environment for work nd life. Unlike the conventionl ir conditioning system, liquid desiccnt dehumidifiction system, bsed on its high ffinity for wter vpor, cn directly dehumidify the moist ir without lowering the ir temperture to its dew point. In this wy, the ppliction of liquid desiccnt dehumidifiction system cn gretly reduce energy consumption. Since the liquid desiccnt dehumidifiction system ws proposed by Löf (1955), this technique hs gone through long-term development. A key mesure to highlight the virtue of this system is to increse the efficiency of its regenertion subsystem. At present, the most widely studied re pcked tower regenertor (Pumo nd Goswmi, 2002; Ani et l., 2005; Sultn et l., 2002; Snjeev et l., 2000; Erts et l., 1994), internl heting regenertor (Yin et l., 2007; Yin et l., 2008) nd solr collector/regenertor (Peng nd Howell, 1984; Li nd Yng, 2008). In these previous literture, the respective influences of vrious system prmeters on the regenertor s performnce re nlyzed, including the system operting prmeters (like the inlet temperture, concentrtion nd mss flow of dilute solution, nd the inlet temperture nd moisture content nd mss flow of regenertion ir) nd the system structure prmeters (like pcking height nd the length of C/R). Among these nlyses, nevertheless, there is none 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

3 2194, Pge 2 tht hs pointed out which prmeter hs the key influence on the evportion rte of wter vpor in regenertor, which prmeter hs the key influence on the regenertion efficiency nd whether there is ny interction mong these prmeters. In this pper, two models, the one-dimensionl model of coupled het nd mss trnsfer in pcked tower verified in experiment (Ren et l., 2006) nd the model of countercurrent het exchnger (Yng nd To, 1998), re dopted to describe respectively the het nd mss trnsfer process of the solution nd ir in regenertion tower nd the process of countercurrent het exchnge in the ir to ir het exchnger. There follows n nlysis of the dt obtined in the numericl experiment by the method of orthogonl design to inspect the importnce of ech fctor nd whether there is interction between them. This nlysis is expected to work s further effort to clrify the reserch ides bout the regenertion subsystem nd thus help reserchers set priorities in both their following experiment nd simultion reserches. 2. MODEL OF REGENERATION SUBSYSTEM 2.1 Model of Regenertion Tower The regenertion subsystem is shown in figure 1. In this subsystem, the model of regenertion tower is described in the one-dimensionl governing equtions of coupled het nd mss trnsfer (Ren et l., 2006), nd the process of het nd mss trnsfer in the smll section of this tower is shown in figure 2. Regenertion tower t Lin, in, m Lin Heter m L, tl, L Solution Interfce d t LI, LI, I m dm, t t, Moist ir d dd d dv HE1 Fn t in, d in, m Solution tnk Solution pump Figure 1: Schemtic of regenertion Figure 2: Schemtic of het nd mss trnsfer process in subsystem smll section of the dehumidifiction tower After trnsforming the prmeters in eqution (2),(11)-(14) in the reference (Ren et l., 2006), governing equtions of the het nd mss trnsfer process in regenertor tower cn be obtined like the eqution (1)-(5) in reference (Tu et l., 2009). These governing equtions re shown s below: dd ( d d )(1/ Le)dNTU (1) el m dm L, t t, L d L L L d L m, t, d Where, d indictes the moisture content of the humid ir, kg/(kg.d.); ir in equilibrium with the solution, kg/(kg.d.); Le indictes Reynolds number; het trnsfer unit in the regenertion tower. m dntu 2 2 2R dw 2R 2R dw R dw 2 del indictes the moisture content of humid dw NTU indictes the number of R d 1.608( d del ) (2) Le In this eqution, indictes mss concentrtion of the solution, %; Rm indictes the molr flow rte rtio of the dry ir nd solute, Rm ( mm d ) /( md M ) ; m nd md indicte respectively the mss flow rte of the ir nd 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

4 2194, Pge 3 solute, kg/s; M nd M d indicte respectively the moleculr weight of the ir nd solute, kg/kmol; R dw indictes moleculr weight rtio of the solute nd wter, Rdw M d M w ; M w indictes the moleculr weight of wter, kg/kmol. dt Le 1.608Rv ( d del ) ( t tl ) dntu (3) Le( d R ) In this eqution, t indictes the ir temperture, o C; t L indictes the solution temperture, o C; R v indictes the rtio of molr specific het t constnt pressure between wter vpor nd dry ir, R M C ) ( M C ) ; C p nd C pv v v ( w pv p indictes respectively the specific het t constnt pressure of dry ir nd wter vpor, kj/(kg o C). dt L ~ C [( t t ) 1.608( h / Le)( d d )]dntu (4) L In this eqution, C indictes the rtio of het cpcities between the ir nd solution; h ~ s indictes the ~ stndrdized het of bsorption, hs ( M whs ) ( M C p ), o C; hs indictes the het of bsorption, kj/kg. Where, dm ml indictes the mss flow rte of the solution, kg/s. The boundry conditions of governing equtions (1)-(5) re shown s below: NTU = NTU 0, tl tlin, in, ml mlin NTU = NTUn, in t t, d din L s el m dd (5) Where, NTU 0 indictes the number of het trnsfer unit t the top of the regenertion tower ( NTU 0 =0 this moment), NTUn indictes the het trnsfer unit number from the top of the tower to its bottom; t Lin, in, mlin indictes the temperture, mss concentrtion nd mss flow rte of the solution when it enters the regenertion tower from the top; t in, d in indictes the temperture nd moisture content of the ir when it enters the regenertion tower from the bottom, nd the subscript in indictes the suction prmeter. 2.2 Model of Het Exchnger In the regenertion subsystem n ir to ir het exchnger is dopted. As is shown in figure 1, the hot nd cold fluid flow direction in het exchnger HE1 re countercurrent, so the method of NTU cn be used to expediently clculte the respective outlet temperture of the hot nd cold fluid. There re two steps of this method: firstly, define the number of het trnsfer unit ( NTU HE ); secondly compre the het cpcity of these two fluids, m hch nd m ccc, nd define the big one s (mc) mx nd the smll one s (mc) min. The efficiency formul of the het exchnger cn be obtined s follow (Yng nd To, 1998): min 1 exp{( NTU HE )[1 ]} mx HE (6) min min 1 exp{( NTU HE )[1 ]} mx mx In this formul, HE indictes the het exchnge efficiency of the het exchnger. The whole het exchnge cpcity in the het exchnge process is s below: Q HE mc) ( t t ) (7) HE ( min hin cin In this formul, tcin nd t hin indicte respectively the inlet temperture of the cold nd hot fluid,. 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

5 2194, Pge 4 The outlet temperture of the hot fluid is: t Q HE hout thin (8) mhch The outlet temperture of the cold fluid is: t cout QHE tcin (9) m C c c Tu et l. (2009) described the model of regenertion tower nd the model of countercurrent ir-ir het exchnger successfully by using the VC++ lnguge simultion modules. These stimultion modules re still dopted in this pper to study the impct of severl relted fctors on the performnce of the regenertion subsystem. 3. EXPERIMENTAL INDEXES AND METHODS 3.1 Experimentl Indexes With reference to relevnt literture (Pumo nd Goswmi, 2002; Yin et l., 2007), the experimentl indexes of the regenertion subsystem in this pper re defined s the wter evportion rte in regenertion tower m nd its regenertive efficiency. Their definition formule re shown s below: m evp out in m d d (10) Where, d out nd d in indicte respectively the ir moisture content of the outlet nd inlet in the regenertion tower, kg/(kg.d.). dout d in (11) d d elin In eqution (11), d elin indictes the moisture content of the humid ir which is in equilibrium with the inlet solution, kg/(kg.d.). in evp 3.2 Experimentl Design nd Anlysis Method Firstly, the numericl experiment in this pper is rrnged by the method of orthogonl design; then the experiment result is nlyzed by the method of vrince nlysis to determine the respective importnce of ech fctor. Orthogonl design is n optimized experimentl design method used in multi-fctor nd multi-level experiment. It is dopted in this pper to choose some representtive ones from ll the tretment combintions for the experiment, thus relieving the burden of doing lrge quntity of multi-fctor comprehensive experiments nd the difficulty in controlling experiment conditions (Liu, 2005). Vrince nlysis is sttisticl method used to determine whether there exists significnt performnce difference mong the levels of fctor. Through dt nlysis by mens of this method, those fctors cn be picked out which ply key influence on the object, the interctions mong them nd the optiml level of ech fctor (Hu nd Wng, 2006). 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

6 2194, Pge 5 4. FACTOR ANALYSIS 4.1 Screening Anlysis of Fctors Before the process of screening, seven influence fctors re picked out. In order to reduce the number of experiments, only two levels of ech of these fctors re chosen. According to the rules, one level is in the centrl position, nd the other is ner the boundry. Fctor level of the centrl position is the optiml vlue bsed on the existing expertise nd experience. The seven fctors nd their levels re shown in Tble 1. Levels Tble 1 The vlues of the two levels for the seven influence fctors Fctors t Lin [ o C] Lin (wt% slt) t in [ o C] d in [kg/kg.d.] m in / md [kg/kg] NTU NTU HE % % Orthogonl tble L 12 (2 11 ) is used to rrnge the orthogonl experiments, nd the rrngement nd results of the selection experiment re shown in figure 2. Through the vrince nlysis of the experimentl dt, P vlue of ech fctor cn be obtined. P vlue is probbility vlue, which shows the error probbility bsed on the belief tht there exists significnt performnce difference mong the levels of fctor. A smll P vlue indictes gret significnce of this fctor nd vice vers. The detiled reltion between P vlue nd the significnce of fctor is s follows: when 0 P vlue 0.01, the fctor is highly significnt nd very importnt; when 0.01<P 0.05, the fctor is significnt nd importnt; when 0.05< P 0.2, the fctor hs wek significnce nd fint influence on the experimentl results; when 0.2<P 1, the fctor is insignificnt nd hs no influence on the experimentl results. Through the vrince nlysis of the experimentl results of the wter evportion rte in the regenertion tower m evp nd its regenertion efficiency Reg, the results re obtined, which re shown in figure 3 nd figure 4 respectively. When the wter evportion rte of the regenertion tower m cts s n experimentl index, from Tble 3 it is obtined tht the P vlue of t Lin is less thn By referring to the reltion between the P vlue nd the significnce of fctors, t is evluted s highly significnt for m evp ; the P vlues of Lin, m / m d, nd Lin NTU rnge from 0.01 to 0.05, which indictes these three fctors re significnt nd cn be vlued s importnt fctors; the P vlues of d in, t in nd NTU HE re ll bove 0.2, which indictes these three fctors re insignificnt nd hve fint influence on the experimentl results. These seven fctors re rrnged in descending order bsed on their respective influence on m evp (or their respective P vlue in scending order) like this: t Lin, m / m d, Lin, NTU, d in, NTU HE, t in. evp 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

7 Tble 2 Arrngement of the orthogonl experiment with L 12 (2 11 ) nd the experiment results 2194, Pge 6 Column number Fctors Experiment number t Lin Lin t in in d md m / NTU NTU HE Results m evp 1 1(50) 1(32%) 1(26.0) 1( ) 1(1.185) 1(1.0) 1(1.0) (50) 1(32%) 1(26.0) 1( ) 1(1.185) 2(3.0) 2(3.0) (50) 1(32%) 2(30.5) 2( ) 2(2.843) 1(1.0) 1(1.0) (50) 2(38%) 1(26.0) 2( ) 2(2.843) 1(1.0) 2(3.0) (50) 2(38%) 2(30.5) 1( ) 2(2.843) 2(3.0) 1(1.0) (50) 2(38%) 2(30.5) 2( ) 1(1.185) 2(3.0) 2(3.0) (70) 1(32%) 2(30.5) 2( ) 1(1.185) 1(1.0) 2(3.0) (70) 1(32%) 2(30.5) 1( ) 2(2.843) 2(3.0) 2(3.0) (70) 1(32%) 1(26.0) 2( ) 2(2.843) 2(3.0) 1(1.0) (70) 2(38%) 2(30.5) 1( ) 1(1.185) 1(1.0) 1(1.0) (70) 2(38%) 1(26.0) 2( ) 1(1.185) 2(3.0) 1(1.0) (70) 2(38%) 1(26.0) 1( ) 2(2.843) 1(1.0) 2(3.0) Tble 3 The vrince nlysis tble when the wter evportion rte of the regenertion tower is regrded s the experimentl index Source DF SS MS F vlue P vlue Totl Error E E-06 t Lin Lin t in E E d in 1 9.5E E m / m d NTU E E NTU HE E E When the regenertion efficiency of the regenertion tower cts s n experimentl index, from Tble 4 it is 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

8 2194, Pge 7 obtined tht the P vlues of both m / m d nd NTU re less thn By referring to the reltion between the P vlue nd the significnce of fctors, they re evluted s highly significnt for nd hving primry influence on ; the P vlue of t Lin rnges from 0.01 to 0.05, which indictes this fctor is significnt nd cn be vlued s n importnt fctor; the P vlue of Lin, t in, d in nd NTU HE re ll bove 0.2, which indictes these four fctors re insignificnt nd hve fint influence on. These seven fctors re rrnged in descending order bsed on their respective influence on m / m d, t Lin, Lin, NTU HE, d in, t in. (or their respective P vlue in scending order) like this: NTU, Tble 4 The vrince nlysis tble when the regenertion efficiency is regrded s the experimentl index Source DF SS MS F vlue P vlue Totl Error t Lin Lin t in E E d in m / m d NTU NTU HE Anlysis of Interctions between Fctors By the method mentioned in section 3.1, we cn lso nlyze the influence of the potentil interctions between fctors on the experimentl indexes. Considering there might be lrge quntity of fctors plus the possible interctions between them, n orthogonl tble L 20 (2 19 ) is used to rrnge these orthogonl experiments. As rrnged, the interctions between the fctors re lso regrded s fctors nd listed on the corresponding lines mong the others on the distribution tble of the interctions exceptionl lines (Chen, 2009). Through the orthogonl numericl experiment nd the vrince nlysis, the P vlues of the possible interctions re obtined s follows: when m cts s n experimentl index, the P vlues of the interctions t Lin NTU, evp Lin NTU, Lin NTU HE, d in NTU, d in NTU HE, m / md NTU HE rnge from 0.05 to 0.2; the P vlues of the other interctions re ll bove 0.2. By referring to the reltion between the P vlue nd the significnce of fctors, finding cn be gined tht the bove six interctions hve fint influence on the evportion rte of the regenertion tower m evp, nd the other interctions hve little influence on m evp. When cts s n experimentl index, the P vlues of the interctions t Lin NTU, in, Lin t m / md, t Lin NTU HE, Lin NTU HE, NTU NTU HE t m / md, d in NTU, d in NTU HE, m / md NTU rnge from 0.05 to 0.2; the P vlues of the other interctions re ll bove 0.2. Therefore these nine interctions hve fint influence on the regenertion efficiency of the regenertion tower. 5. CONCLUSION According to the bove nlysis, severl conclusions re summrized s follows: (1) Bsed on the screening nlysis of the fctors in regenertion subsystem of the liquid desiccnt system, it is found tht when different experimentl indexes re chosen, there is reltively mrked difference in the importnce of seven 15 th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

9 2194, Pge 8 fctors, t Lin, Lin, t in, d in, m / m d, NTU nd NTU HE. When the wter evportion rte of the regenertion tower m evp cts s the experimentl index, t Lin proves to be the most importnt fctor, followed by Lin, m / m d nd NTU, which re lso the importnt fctors. And the other three fctors hve no significnt influence on the experiment. When the regenertion efficiency NTU prove to be the most importnt fctors, followed by Lin four fctors hve little influence on the experiment. t m / m nd cts s the experimentl index, d, which is lso n importnt fctor. And the other (2) Bsed on the further nlysis of the interctions between fctors, it is found tht when m evp cts s the experimentl index, the interctions t Lin NTU, Lin NTU, Lin NTU HE, d in NTU, d in NTU HE, m / md NTU HE hve reltively wek influence on the experiment, nd the other interctions hve no influence on the experiment. When cts s the experimentl index, the interctions t Lin NTU, t Lin m / m d, t Lin NTU HE, Lin NTU HE, NTU NTU HE, t in m / m d, d in NTU, d in NTU HE, m / m d NTU hve wek influence on the experiment, nd the influence of other interctions cn be neglected. (3) There is nother finding bsed on the further nlysis: whether m evp or cts s the experimentl index, t Lin, md m /, NTU re the importnt influence fctors; lthough there is no significnt influence of NTU HE on the two experimentl indexes, it hs wek interctions with mny of the other fctors, which indictes NTU HE hs wide rnge of influence; the two regenertion ir inlet prmeters, t in nd d in, hs little influence on the two experimentl indexes. REFERENCES [1] Ani, F.N., Bdwi, E.M., Knnn, K.S., 2005, The effect of bsorber pcking height on the performnce of hybrid liquid desiccnt system, Renew. Energ., vol. 30: p [2] Erts, A., Gndhidsn, P., Kiris, I., Anderson, E.E., 1994, Experimentl study on the performnce of regenertion tower for vrious climtic conditions, Sol. Energy., vol. 53, no.1: p [3] Li, Y.T., Yng, H.X., 2008, Investigtion on solr desiccnt dehumidifiction process for energy conservtion of centrl ir-conditioning systems, Appl. Therm. Eng., vol. 28: p [4] Peng, C.S.P., Howell, J.R., 1984, The performnce of vrious types of regenertors for liquid desiccnts, J. Sol. Energ-T ASME, vol. 106: p [5] Pumo, N., Goswmi, D.Y., 2002, Study of n queous lithium chloride desiccnt system: ir dehumidifiction nd desiccnt regenertion, Sol. Energy, vol. 72, no.4: p [6] Ren, C.Q., Jing, Y., Zhng, Y.P., 2006, Simplified nlysis of coupled het nd mss trnsfer processes in pcked bed liquid desiccnt-ir contct system, Sol. Energy, vol. 80: p [7] Snjeev, J., Dhr, P.L., Kushik, S.C., 2000, Experimentl studies on the dehumidifier nd regenertor of liquid desiccnt cooling system, Appl. Therm. Eng., vol. 20, no.3: p [8] Sultn, G.I., Hmed, A.M., Sultn, A.A., 2002, The effect of inlet prmeters on the performnce of pcked tower-regenertor, Renew. Energ., vol. 26: p [9] Tu, M., Ren, C.Q., Zhng, L.A., Sho, J,W., 2009, Simultion nd nlysis of novel liquid desiccnt ir-conditioning system, Appl. Therm. Eng., vol. 29, no.11-12: p [10] Yin, Y.G., Zhng, X.S., Chen, Z.Q., 2007, Experimentl study on dehumidifier nd regenertor of liquid desiccnt cooling ir conditioning system, Build. Environ., vol. 42, no.7: p [11] Yin, Y.G., Zhng, X.S., Wng, G., Luo, L., 2008, Experimentl study on new internlly cooled/heted dehumidifier/regenertor of liquid desiccnt systems, Int. J. Refrig., vol. 31, no.5: p [12] Löf, G.O.G., 1955, Cooling with Solr Energy, Congress on Solr Energy: p th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

10 2194, Pge 9 [13] Lowenstein, A., 2005, High efficiency liquid-desiccnt regenertor for ir conditioning nd industril drying, Finl Report: DOE Contrct # DE-FG36-03GO [14] Yng, S.M., To, W.Q., 1998, Het Trnsfer. 3rd ed, Higher eduction press, Beijing, p [15] Liu, W.Q., 2005, Design of Experiments, Tsinghu University Press, Beijing, p [16] Hu, X.B., Wng, L.X., 2006, Probbility nd Mthemticl Sttistics. 2nd ed, Beijing University of Post & Telecommuniction Press, Beijing, p [17] Chen, X.P., 2009, Some notes on interctions of mixed-level orthogonl rrys, Est Chin Techers University, Shnghi: p th Interntionl Refrigertion nd Air Conditioning Conference t Purdue, July 14-17, 2014

New Expansion and Infinite Series

New Expansion and Infinite Series Interntionl Mthemticl Forum, Vol. 9, 204, no. 22, 06-073 HIKARI Ltd, www.m-hikri.com http://dx.doi.org/0.2988/imf.204.4502 New Expnsion nd Infinite Series Diyun Zhng College of Computer Nnjing University