MULTI EFFECT PLANTS AND IONIC LIQUIDS FOR IMPROVED ABSORPTION CHILLERS

Transcription

1 HEFAT th Internatonal Conference on Heat Transfer, Flud Mechancs and Thermodynamcs July 2012 Malta MULTI EFFECT PLANTS AND IONIC LIQUIDS FOR IMPROVED ABSORPTION CHILLERS Weth T.*, Preßnger M., Pöllnger S. and Brüggemann D. *Author for correspondence Zentrum für Energetechnk, Unverstät Bayreuth, Bayreuth, Germany, E-mal: LTTT@un-bayreuth.de ABSTRACT State of the art absorpton chllers usng conventonal workng pars stll suffer from problems lke crystallzaton, corrosveness and a relatvely low effcency. To mprove ths technology, dfferent workng pars as well as plant desgns are nvestgated usng the smulaton tool AspenPlus. The smulaton s valdated by comparng the results of sngle effect absorpton chllers usng the current commercally appled workng pars water/lthum bromde and ammona/water wth lterature data. To ncrease the effcency, double effect absorpton chllers are mplemented and analyzed. The performance of two knds of double effect cycles, seres and parallel, s compared usng the workng par water/lthum bromde. In addton, onc lquds (ILs) are nvestgated as a sorbent n order to mprove the technology. So far, ILs have not been mplemented n AspenPlus yet. Therefore, a gudelne for the mplementaton of ILs n AspenPlus s outlned and the accordant phase equlbra results are valdated wth lterature data. Smulatons of sngle effect cycles usng the ILs 1,3-dmethylmdazolum dmethylphosphate ([MMIM][DMP]) and 1-ethyl-3-methylmdazolum dmethylphosphate ([EMIM][DMP]) n combnaton wth water as a refrgerant are performed and the results are compared to conventonal workng pars. INTRODUCTION Refrgeraton, coolng and ar condtonng have always been mportant ssues. Especally the rapd growth of the world populaton and the ncreasng conformaton of the standard of lvng of developng countres to ndustral natons have led to an enormous ncrease of coolng demand. Ths development wll addtonally be ntensfed by future clmate change. NOMENCLATURE Δ vaph [J/mol] molar heat of vaporzaton C Antone-parameters COP [-] coeffcent of performance c p [J/mol K] specfc heat capacty D DIPPR-parameters [EMIM][DMP] 1-ethyl-3-methylmdazolum dmethylphosphate ENRTL-RK Electrolyte NRTL Redlch-Kwong property method f [-] crculaton rato h [J/mol] molar enthalpy IL [-] onc lqud LBr lthum bromde M [g/mol] molar mass ṁ [kg/s] mass flow [MMIM][DMP] 1,3-dmethylmdazolum dmethylphosphate NH 3 ammona NRTL Non-Random Two-Lqud property method p [N/m²] partal pressure PENG-ROB PSRK Q [W] heat transfer rate T [K] temperature x [-] molar fracton Subscrpts a c DE e g rec ref SE shx Peng-Robnson property method Predctve Soave-Redlch-Kwong property method absorber condenser double effect evaporator generator recuperator reference state sngle effect soluton heat exchanger Superscrpts * pure component g deal gas l lqud phase v vapour phase 834

2 In recent years, conventonal compresson refrgeraton machnes have covered the predomnant part of coolng need. As t requres a hgh amount of electrcal energy to power these systems, lower energy solutons have to be consdered for the future. In ths context, absorpton chllers represent a sutable alternatve to compresson devces. These chllers are manly powered by external heat, whereas the amount of addtonal electrc energy s almost neglgble. Therefore, especally n ndustral coolng applcatons where waste heat can serve as heat source, the applcaton of ths technology can reduce electrc power consumpton [1]. Besde ths advantage, absorpton chllers anyhow suffer from several problems. On the one hand, conventonal plant desgns generally offer low effcences and are lmted by the heat source temperature, on the other hand, the state of the art workng pars water/lthum bromde and ammona/water ental rsks lke crystallzaton and corroson [2]. To overcome these ssues, the present work nvestgates advanced plant desgns as well as new workng pars usng the smulaton tool AspenPlus [3]. In a frst step, the accuracy of our smulaton s valdated by comparng the results of sngle effect plants usng the conventonal workng pars water/lthum bromde and ammona/water wth lterature data. Later on, the advantages of double effect plants are revealed through the comparatve analyss of seres and parallel double effect cycles and conventonal sngle effect systems. Fnally, as a substtuton of conventonal workng pars, the ILs 1,3-dmethylmdazolum dmethylphosphate ([MMIM][DMP]) and 1-ethyl-3- methylmdazolum dmethylphosphate ([EMIM][DMP]) n combnaton wth water as a refrgerant are used n a sngle effect absorpton system. ILs are chosen as sorbent, due to ther generally low vapour pressures and ther ablty of absorbng huge amounts of refrgerant. Furthermore, corroson and crystallzaton problems, as typcal for conventonal workng pars, can be overcome. ILs have not been mplemented n AspenPlus yet. Therefore, the present work outlnes a gudelne for the mplementaton of ILs n ths smulaton tool and valdates the accordant phase equlbra results wth lterature data. Fnally, the performance of ILs n sngle effect absorpton chllers s compared wth conventonal workng pars. MODELS, METHODS AND BOUNDARY CONDITIONS Models of the Investgated Plant Desgns The AspenPlus flow sheet of the nvestgated conventonal sngle effect absorpton chller s represented n Fgure 1. The cycle model s set up accordng to Somers et al. [4] and s realzed as a closed loop. In analogy to compresson refrgeraton systems, the absorpton chller conssts of a condenser (COND), an expanson valve (EXPV), an evaporator (EVAP) and a compresson unt. In contrast to compresson refrgeraton chllers, the compresson s realzed through a socalled thermal compressor through the followng steps: In the absorber (ABS), the refrgerant s absorbed by the sorbent. Then, the pump (PMP) rases the soluton to a hgher pressure level. Before enterng the generator unt (GEN) the soluton passes the soluton heat exchanger (SHX), to reuse a part of the heat ntroduced n the generator. In GEN the sorbent desorbs the refrgerant agan, whch then leaves the generator at hgh pressure. Fgure 1 AspenPlus flow sheet of the sngle effect absorpton chller Fgure 2 shows the generator unt, modelled through a combnaton of dfferent sngle components that account for the thermodynamc processes. It should be noted that ths set-up does not correspond to a real plant assembly. To fulfl the precondton that the temperature of the refrgerant leavng the generator unt s equal to the bolng temperature of the ncomng soluton, the frst heater (GEH1) heats the soluton up to ts bolng temperature and transfers ths value to the heat exchanger (GENX). There, the vapour transfers as much heat to the soluton as requred to reach ts bolng temperature. The flash unt (GENF) separates the evaporated refrgerant and the resdual soluton and the superheated vapour leaves the generator through the heat exchanger. Fgure 2 AspenPlus flow sheet of the generator herarchy The performance of absorpton chllers s expressed as coeffcent of performance (COP). Neglectng the small power consumpton of the pump, t can be calculated n terms of the rato of evaporator and generator duty: COP EVAP EVAP = = (1) GEN GEH1 + GEH 2 The second nvestgated plant desgn s the sngle effect system wth an addtonal rectfcaton as represented n Fgure 3. Ths confguraton has to be chosen n case of ammona/water as a workng par. As the vapour pressure of water s not neglgble compared to that of ammona, the vapour generated n the desorber stll contans a small fracton of water. Hence, for reducng ths amount and rasng the COP, the rectfcaton column has to be added. 835

3 Fgure 3 AspenPlus flow sheet of the sngle effect absorpton chller wth rectfcaton Due to the rectfcaton, the generator possesses an addtonal nflow stream. Therefore, ts model has to be adjusted. The flow sheet n Fgure 4 shows a supplemental mxer (MIX) and flash unt (GEF2). The condensate comng from the flash block RF1 s partly evaporated by the heater RH. In the flash devce RF2 the vapour fracton s then separated from the resdual lqud phase, whch flows back to the generator. In REFMIX the vapour s mxed up wth the vapour comng from the generator. Thereafter, t s partly condensed n RC. Accordng to vapourlqud equlbrum, the content of sorbent n the lqud phase exceeds that n the vapour phase. The purty of the refrgeraton vapour s set by defnng the temperature of RC. Fnally, the condensate s separated n RF1 and reflows through the rectfcaton cycle, whereas the refrgerant-rch vapour leaves the rectfcaton. As the descrbed rectfcaton requres an addtonal heat nput n RH, the COP for the NH 3 /water absorpton chller s redefned as follows: COP = EVAP GEN = GEH1 + EVAP GEH 2 + Next to the descrbed sngle effect plant confguratons, double effect desgns usng water/lbr as a workng par are nvestgated. RH (2) Fgure 4 AspenPlus flow sheet of generator herarchy n case of an addtonal rectfcaton In the mxer, the soluton stream of the soluton heat exchanger, the reflow from the rectfcaton and the lqud phase from GEF2 converge. Vapour stream 3 stll contans small fractons of water. A part of that lqud can already be condensed out n GENX. Ths condensate s then separated n GEF2 and s fed back to GENX by MIX. The modellng of the requred rectfcaton unt n AspenPlus s llustrated n Fgure 5. It conssts of two flash blocks, a mxer, as well as a heater and a cooler. Fgure 5 AspenPlus flow sheet of the rectfcaton herarchy Fgure 6 AspenPlus flow sheet of the seres double effect absorpton chller As n sngle effect plants, consderng water/lbr, no addtonal rectfcaton unt s needed. Double effect plants can be regarded as a combnaton of two sngle effect systems and the resultng COP can be estmated n terms of the sngle effect COP [1]: DE SE 2 SE COP = COP + COP (3) 836

4 The double effect cycle technology dstngushes several varants. These manly vary n the knd of connecton of the two soluton cycles. In ths study, seres and parallel confguratons are nvestgated. The appled model of the seres double effect plant s represented n Fgure 6. In ths plant desgn the second generator GEN2 corresponds to the sngle effect generator shown n Fgure 2. In the frst generator (GEN1) the heat of condensaton of condenser CON2 s used to desorb even more refrgerant. Its AspenPlus realzaton s shown n Fgure 7. Fgure 7 AspenPlus flow sheet of generator herarchy GEN1 of the seres double effect confguraton Fgure 8 presents the double effect plant n parallel confguraton. GEN2 agan equals that of the sngle effect plant, whle GEN1 s modfed by an addtonal spltter. Its herarchy s vsble n Fgure 9. Fgure 9 AspenPlus flow sheet of generator herarchy GEN1 of the parallel double effect confguraton The calculaton of the COP of the double effect cycles follows equaton (1). The generator dutes n the denomnator of ths equaton then correspond to the second generator GEN2. Boundary Condtons In the present study, the refrgerant s fully lquefed (x = 0) n the condenser at a condensaton temperature of 40 C and fully evaporated (x = 1) n case of conventonal workng pars, respectvely evaporated to a vapour fracton of x = n case of ILs, n the evaporator at an evaporaton temperature of 10 C. Settng the evaporator temperature to a fxed value corresponds to the am of achevng a desred coolng temperature. The absorpton temperature s set to 35 C and n the soluton heat exchanger, a pnch pont dfference of 10 C s assumed. Regardng the double effect cycles, the boundary condtons of condenser and generator are related to CON2 and GEN2 respectvely. Property Methods For water/lbr the property model ENRTL-RK s used, as t s desgned for descrbng electrolytes. Ths method s based on the Asymmetrc Electrolyte NRTL property model. It utlzes the Redlch-Kwong equaton of state for vapour phase propertes and the asymmetrc reference state for onc speces (nfnte dluton n aqueous soluton) [5]. In case of the workng par ammona/water, the property model PENG-ROB s appled. For the purpose of comparson, smulatons are carred out by usng the NRTL- and PSRKmodel as well. Regardng ILs, the standard NRTL-model s assumed, whch apples the NRTL actvty coeffcent model for lqud phase and the deal gas equaton of state for vapour phase [5]. Gudelne for the Implementaton of ILs n AspenPlus As mentoned at the begnnng, ILs are not avalable n the AspenPlus databanks. Therefore, a methodology to mplement these fluds had to be developed. The procedure proposed n ths study follows Seler et al. [6]. Fgure 10 shows the major steps together wth the requred nput data. Fgure 8 AspenPlus flow sheet of parallel double effect absorpton chller 837

5 T h ( T ) = h ( T ) + c ( T ) MdT (6) ref The reference enthalpy s determned by the sum of deal gas enthalpy and the departure of the vapour phase from the deal behavour mnus the heat of vaporzaton: h ref *, g Tref *, v p, ( T ) = h + ( h h ) h (7) *, g vap Fgure 10 Gudelne for the mplementaton of ILs n AspenPlus As the NRTL-model s used n our smulaton, the frst step s to generate the NRTL-parameters through data regresson. For ths purpose, several flud propertes are requred. These nclude vapour lqud equlbrum (VLE) data and a data set for the saturaton pressure. The VLE data ponts n form of TPXY values orgnate from He et al. [7] for water/[mmim][dmp] and from Ren et al. [8] n case of water/[emim][dmp], respectvely. The saturaton pressure as a functon of temperature s defned by the extended Antone equaton: C ln = + (4) 2 C7 p C1 + + C4T + C5 lnt C6T T + C3 The coeffcents n ths equaton are estmated under the use of a notonal data set (TPL). Due to the extremely low vapour pressure of ILs these fctve values (0 C / bar and 100 C / bar) do not nfluence the calculatons sgnfcantly. The second step s relevant to determne enthalpes correctly. The standard NRTL model uses the deal gas enthalpy for calculatng lqud phase propertes. For ILs nformaton about the crtcal pont and the deal gas heat capacty s not avalable and, therefore, t s not possble to calculate vapour phase. As a consequence, the routes defnng the calculaton methods n AspenPlus have to be changed so that all relevant propertes are calculated from lqud phase data. Thus, the route for calculatng the lqud molar enthalpy of a mxture HLMX s set to HLMX21 so that t s expressed n terms of the lqud enthalpes of the pure components and ther molar fractons: l h ( T ) = x h ( T ) (5) For the calculaton of lqud enthalpes of pure components the lqud heat capacty s ntegrated from a reference temperature to the actual temperature and a reference enthalpy s added by settng the route HL to HL09: As the devaton from the deal behavour s calculated through the deal gas model t vanshes n equaton (7). The reference enthalpy s a constant value as t s defned at fxed reference temperature. Therefore, calculaton errors just affect absolute enthalpy values. As n these processes only enthalpy dfferences are mportant for energy balances and the COP, the calculaton of the reference enthalpy can be based on pseudo data and parameters for the deal gas heat capacty (CPIG) can be notonal. The Watson model s used for calculatng the heat of vaporzaton. For the reference enthalpy (h ref ) and temperature (T ref ) requred n ths method notonal values are used, too. Fnally, for calculatng the lqud heat capacty of the pure component requred n equaton (6), the DIPPR-model s used: c p, ( T ) = D1 + D2T + D3T + D4T + D5T (8) The coeffcents n ths polynomal (CPLDIP) are ganed by the regresson of expermental data from He and Ren usng MATLAB [9]. The last route that has to be set s that of the excess enthalpy HLXS. The default settng assumes a zero excess enthalpy. The only way to determne the excess enthalpy wthout addtonal flud propertes conssts n HLXS10, whch utlzes the NRTL-model. Next to the descrbed ones, further propertes necessary for the smulaton have to be mplemented. These nclude the molar mass that can be found n data sheets or lterature and crtcal parameters lke T crt, p crt, V crt and z crt, for whch notonal values have to be assumed. In the end, the AspenPlus sheet contanng all the necessary data and calculaton methods s coped n the AspenPlus plant desgn project. Henceforth, smulatons wth ILs as sorbents n absorpton chllers can be performed. VALIDATION Valdaton of the Sngle Effect Cycles To valdate our smulatons, comparsons between our results and Herold et al. [10] have been drawn. Contrary to the boundary condtons descrbed above, condtons were set equal to the reference. The results for water/lbr are presented n Table 1. The generator duty s set fxed. Hence, the values solely vary n the range of the tolerance lodged n AspenPlus. The dutes of condenser and evaporator devate by nearly 4 %. Ths results from an ncreased mass flow n the refrgerant branch rooted n the dfference n calculatng phase equlbra. The devaton n the mass flow s the reason for the decreased crculaton rato, too. Due to the ncreased evaporator duty and the nearly constant generator duty, the COP reaches hgher values n the AspenPlus smulatons. 838

6 Table 1 Comparson of our results for water/lbr wth Herold et al. [10] Herold et al. ths work ε [%] rel Q n kw a Q n kw c Q n kw g Q n kw e Q n kw shx COP f Regardng ammona/water as a workng par, the purty of ammona s set as a fxed condton. Consequently, the mass flow rates n the refrgerant branch are consstent. Table 2 shows the devatons of our smulatons usng PENG-ROB as a property method n comparson to the reference data. Despte the almost equal refrgerant mass flow rate, the values for the condenser duty dffer by around 4.9 %, whereas the evaporator duty does not devate sgnfcantly. Usng other property methods lke the NRTL or PSRK model, dfferent devatons occur. Therefore, as all of them are based on the same plant model, dfferences n phase equlbra calculatons are the reason for these devatons, too. Ths s emphaszed by regardng the dutes of absorber and generator. Especally the duty of the rectfcaton shows wth 26.5 % a hgh devaton. Usng other property methods lke for example the NRTLmodel t dffers by merely 1.14 %. Therefore, t s obvous that agan dfferences n the calculaton of phase equlbra cause ths effect. Notably hgh dfferences also arse at the soluton heat exchanger wth nearly 11 %. The absorber temperature s nearly equal to the lterature value, but the generator temperature s much hgher. Moreover, the heat exchanger effcency s fxed. Hence, the temperature dfference of the refrgerant-poor soluton and therewth the transferred duty s ncreased. It should be noted that n ths case the COP s calculated accordng to equaton (1), as Herold et al. dd so. Hence, the addtonal rectfcaton s not consdered. Table 2 Comparson of our results for NH 3 /water wth Herold et al. [10] Herold et al. ths work ε [%] rel Q n kw a Q n kw c Q n kw g Q n kw e Q n kw shx Q n kw rec COP f Besdes the sngle effect chllers, double effect confguratons have been valdated, too. None of the resultng devatons reaches values above 9 %. Summng up t can be concluded that the developed plant models together wth the property methods chosen provde comparable results to lterature data and are qualfed for further nvestgatons. Valdaton of the Implementaton of ILs To revew the regresson of the NRTL-parameters and, therefore, the correct mplementaton of ILs n AspenPlus, phase equlbra data of the ternary mxture water, ethanol and [EMIM][BF 4 ] are compared to lterature data provded by Seler et al. [6]. As a regresson method the maxmumlkelyhood method s chosen n AspenPlus. Fgure 11 shows the results of our smulaton together wth the expermental and calculated values from Seler et al. at a temperature of 90 C for a molar fracton of the IL of 0.1 and 0.5 respectvely. Fgure 11 y,x-dagram for the system ethanol-water- [EMIM][BF 4 ] It can be seen that our results generated wth AspenPlus correspond well to the results Seler calculated by the use of NRTL-parameters. Consequently, n both cases the devaton from expermental data s almost equal. Next to the correct calculaton of phase equlbra, the effect of the notonal data used durng the mplementaton has been nvestgated. It could be concluded through a smple smulaton of transferrng heat to a mxture of water and [EMIM][BF 4 ] n a flash-devce that the varaton of these values has no sgnfcant nfluence on the results. RESULTS AND DISCUSSION Comparson of Double Effect Cycles Fgure 12 presents the results of the sngle and double effect absorpton chllers usng water/lbr as a workng par. Boundary condtons are set as descrbed n the correspondng sub-chapter and the COP s calculated accordng to equaton (1). 839

7 The dagram shows the varaton of the COP wth rsng generator temperature. Next to the attaned smulaton data, theoretcal values for the double-effect plant calculated by equaton (3) are represented by the hollow symbols. Regardng the sngle-effect ammona/water absorpton chller, operatng temperatures are n the same range as n the nvestgated double effect systems. However, COP-values are far beyond the ones of the double effect plants as shown n Fgure 13. Fgure 12 Influence of the generator temperature on the COP of dfferent plant desgns usng water/lbr as workng par At comparable generator temperatures, a relatvely good concordance between these predcted values and the smulaton data for the double-effect cycles can be notced. Therefore, a COP ncrease of up to about 88 % can be acheved by usng double effect cycles. Comparng seres and parallel confguraton, only small dfferences can be determned. For small generator temperatures, the COP of the seres confguraton exceeds the one of the parallel desgn by maxmal 5 % regardng reasonable generator temperatures. Ths trend changes at a temperature of 152 C, where for the frst tme the parallel cycle s superor to the seres. The parallel one reaches n ths range a COP ncrease of maxmal 0.8 % compared to the seres cycle. In analogy to the results reported by Xu and Da [11] ths change s lkely to depend on the soluton heat exchanger heat-recover effectveness. As the parallel cycle requres more control complexty [10] and COP-values of both confguratons are qute smlar, seres desgns should be favored. Parallel to that, the fgure shows a shft to hgher generator temperatures n case of the double effect cycles. Ths s consstent wth lterature statements that double effect absorpton chllers are employed at hgh heat source temperatures [10; 12]. It has to be mentoned that the above results of water/lbr are qute theoretcal, as they do not consder a possble crystallzaton. Accordng to Herold et al. [10] water/lbr may crystallze at generator temperatures above 100 C under the nvestgated boundary condtons consderng the sngle-effect chller. Farsh et al. [2] report a less rsk of crystallzaton for double effect cycles. They also concluded that parallel confguraton shows the wdest operatng range wthout crystallzaton. Nevertheless, ths rsk has to be kept n mnd when comparng systems contanng water/lbr. Fgure 13 Influence of the generator temperature on the COP of double effect systems usng water/lbr and a sngle effect plant usng ammona/water Effect of ILs as Sorbent The effect of the generator temperature on the COP of the sngle effect plants usng the ILs [MMIM][DMP] and [EMIM][DMP] n combnaton wth water as a workng par s represented n Fgure 14. For the purpose of comparson, the results of the sngle effect confguratons wth conventonal workng pars are llustrated, too. Fgure 14 Influence of the generator temperature on the COP of a sngle effect absorpton chller usng dfferent workng pars 840

8 It can be seen that the workng par ammona/water agan cannot compete wth the others, whereas the COPs of water/lbr are comparable to that of the ILs. Water/[EMIM][DMP] seems to be the most promsng par as t reaches the hghest COP-values wth a maxmum of Smlar results wth regard to ILs have been found by other research groups (Yokosek and Shflett [13]). Next to the ncreased COP, the IL provdes a wder operatng range. Whle t can effcently be used up from a generator temperature of about 75 C, water/lbr needs temperatures above 85 C and ammona/water even around 115 C. Therefore, applyng ths IL allows the use of mnor heat source temperatures. Regardng water/[mmim][dmp] ths range can be enlarged down to a temperature of 65 C, but the maxmal achevable COP value of around 0.71 s below that of water/[emim][dmp] and water/lbr. Agan, regardng water/lbr, the rsk of crystallzaton has to be taken nto account at generator temperatures above 100 C. CONCLUSION Smulatons of varous absorpton chllers have been performed consderng dfferent plant desgn as well as workng pars. The comparson of the results of sngle effect absorpton chllers usng water/lbr and ammona/water wth lterature data revealed good agreement. Based on the correct mplementaton of the processes, double effect cycles have been smulated. The results show that these cycles are sutable for hgh heat source temperatures. Though the COP reaches almost 1.9 tmes the COP of the sngle effect cycle, a more complex plant desgn has to be consdered. Between seres and parallel confguraton only small dfferences can be observed n the COP. Moreover, the superorty of one confguraton changes at a certan generator temperature dependng on the soluton heat exchanger effectveness. Regardng ILs as solvent, ther correct mplementaton n AspenPlus could be verfed. The results of the sngle effect absorpton chller usng ILs showed sgnfcantly hgher COPs compared to ammona/water and smlar ones to water/lbr. [EMIM][DMP] reaches hgher values than water/lbr (up to 0.84), whereas wth a maxmum COP of 0.71 [MMIM][DMP] provdes mnor values. Apart from ths, ILs show a broader operaton range. In case of [MMIM][DMP] an effectve use starts at around 65 C, whereas water/lbr requres temperatures above 85 C and ammona/water even 115 C. As the two nvestgated ILs show dfferent operatng ranges as well as COPs, t s obvous to fnd even more promsng ILs out of the presently over 1500 speces n the future [14]. Summng up t can be concluded that ILs provde wth ther smlar or even hgher COPs and ther broader operatng range a promsng alternatve to the problematc conventonal workng pars n the absorpton refrgeraton technology. Furthermore, double effect systems have been detected as an nstrument to mprove effcency. Therefore, a combnaton of both aspects seems to represent a promsng soluton. Smulatons of ILs n double effect absorpton chllers wll be carred out n the future to further mprove the absorpton refrgeraton technology and make t even more compettve compared to conventonal compresson refrgeraton machnes. Moreover, expermental measurements of propertes of ILs wll provde a proper data base to ncrease the accuracy of the AspenPlus results. REFERENCES [1] Srkhrn P., Aphornratana S., Chungpabulpatana S., A revew of absorpton refrgeraton technologes, Renewable and Sustanable Energy Revews 5 (4), 2001, pp [2] Garous Farsh L., Seyed Mahmoud S.M., Rosen M.A., Analyss of crystallzaton rsk n double effect absorpton refrgeraton systems, Appled Thermal Engneerng 31 (10), 2011, pp [3] Aspen Technology, Incorporaton. Aspen One V 7, Process Optmzaton for Engneerng, Manufacturng, and Supply Chan, Aspen Plus V 7.3., 2011 [4] Somers C., Mortazav A., Hwang Y., Radermacher R., Rodgers P., Al-Hashm S., Modelng water/lthum bromde absorpton chllers n ASPEN Plus, Appled Energy 88 (11), 2011, pp [5] Aspen Technology Inc., Aspen Physcal Property System. Physcal Property Methods. Documentaton to AspenPlus V 7.3, Burlngton, 2011 [6] Seler M., Jork C., Schneder T., Arlt W. (Hg.), Ionc lquds and hyperbranched polymers - promsng new classes of selectve entraners for extractve dstllaton, Proceedngs of the Internatonal Conference on Dstllaton and Absorpton, 2002 [7] He Z., Zhao Z., Zhang X., Feng H., Thermodynamc propertes of new heat pump workng pars, 1,3-Dmethylmdazolum dmethylphosphate and water, ethanol and methanol, Flud Phase Equlbra 298 (1), 2010, pp [8] Ren J., Zhao Z., Zhang X., Vapor pressures, excess enthalpes, and specfc heat capactes of the bnary workng pars contanng the onc lqud 1-ethyl-3-methylmdazolum dmethylphosphate, The Journal of Chemcal Thermodynamcs 43 (4), 2011, pp [9] MathWorks, Inc.: MATLAB R2010b, 2010 [10] Herold K.E., Radermacher R., Klen S.A., Absorpton chllers and heat pumps, Boca Raton, CRC Press, 1996 [11] Xu G.P., Da Y.Q., Theoretcal analyss and optmzaton of a double-effect parallel-flow-type absorpton chller, Appled Thermal Engneerng 17 (2), 1997, pp [12] Arun M.B, Maya M.P, Srnvasa Murthy S., Performance comparson of double-effect parallel-flow and seres flow water lthum bromde absorpton systems, Appled Thermal Engneerng 21 (12), 2001, pp [13] Yokozek A., Shflett M.B., Water Solublty n Ionc Lquds and Applcaton to Absorpton Cycles, Ind. Eng. Chem. Res 49 (19), 2010, pp [14] Freemantle M., An Introducton to Ionc Lquds, Cambrdge, RSC Pub.,