Research Article Performance Analysis of Organic Rankine-vapor Compression Ice Maker Utilizing Food Industry Waste Heat

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1 Advane Journal of Food Siene and Tehnology 8(1): 72-77, 2015 DOI: /ajfst ISSN: ; e-issn: Maxwell Sientifi Publiation Cor. Submitted: November 7, 2014 Aeted: January 21, 2015 Published: May 05, 2015 Researh Artile Performane Analysis of Organi Rankine-vaor Comression Ie Maker Utilizing Food Industry Waste Heat 1, 2 Bing Hu, 1, 2 Yuanshu Cao and 1 Weibin Ma 1 Guangzhou Institute of Energy Conversion, Key Laboratory of Renewable Energy, Chinese Aademy of Sienes, Guangzhou , China 2 University of Chinese Aademy of Sienes, Beijing , China Abstrat: To develo the organi Rankine-vaor omression ie maker driven by food industry exhaust gases and engine ooling water, an organi Rankine-vaor omression yle system was emloyed for ie making and a thermodynami model was develoed and the effets of working fluid tyes, hot water temerature and ondensation temerature on the system erformane were analyzed and the ie making aaity from unit mass hot water and unit ower waste heat were evaluated. The alulated results show that the working fluid tye and the temeratures of heat soure and ondensation have imortant effets on the system erformane. The system an ahieve otimal erformane when use R245fa as ower and refrigeration medium. The ie quantity generated from er ton hot water is kg and the ie-making rate for er kw waste heat is 2.27 kg/h, when the temeratures of hot water and ondensation are resetively 100 and 40 C. A onlusion an be draw by the alulation and analysis that using organi Rankine-vaor omression system for ie making from food industry waste heat is feasible. Keywords: Exander, food industry waste heat, ie maker, organi rankine yle, vaor omression yle INTRODUCTION Modern large food industry is generally equied with mehanial refrigeration, but all of them use fuel oil or eletriity to ahieve refrigeration. While for middle tye and mini-tye food industry with ower in the range of kw, most of them annot arry omressor-ie maker beause of their small horseower of diesel engine (Wang and Wang, 2005; Wang et al., 2004a). For the sake of food reservation, these middle tye and mini-tye food industry have to arry a lot of ie, whih osts muh. At the same time, waste heat disharged from the hot exhaust gases with temerature of 400 C or so in most of the food industry is rejeted to the atmoshere, whih aounts for 30-35% of the energy of a diesel engine. Besides, waste heat disharged from the engine ooling water with temerature of C aounts for about 30% of the burning energy in a diesel engine, whih is also rejeted to the atmoshere (Wang et al., 2006a, 2008). So, making use of these waste heats for ie making for food reservation is of great signifiane. At resent, some effort has been devoted to the utilization of the vast amount of the waste energy for refrigeration. The heat-oerated absortion/adsortion systems an utilize waste heat for refrigeration. Srikhirin et al. (2001) desribed a number of researh otions of absortion refrigeration tehnology and rovided a omarison of the various tyes of absortion refrigeration systems. Meunier (1998) laimed solid sortion is very effetive for low grade ooling, not only for air onditioning but also for dee freezing. Wang and his team (Wang et al., 2004b, 2005; 2006b, ; Lu et al., 2007; Wang and Wu, 2005) had devoted great efforts to researh the adsortion ie maker utilizing waste heat from the food industry and had made a lot of ahievements. Although the adsortion ie maker system has the advantages of simle ontrol, low initial investment and irulating exenditure and less noise, the oeffiient of erformane is generally low. Beause of sustainable develoment requirements, effiient refrigerators driven by low grade thermal energy from different soures have reeived muh more attention in reent years. Currently, the use of thermal energy to oerate an Organi Rankine Cyle-Vaor Comression Cyle (ORC/VCC) for refrigeration has beome the subjet of renewed interest and has been reorted by several investigators. The ORC/VCC system onverts waste heat into a ooling effet, whih is aomlished at the Corresonding Author: Bing Hu, Guangzhou Institute of Energy Conversion, Key Laboratory of Renewable Energy, Chinese Aademy of Sienes, No. 2, Nengyuan Rd, Wushan, Tianhe Distrit, Guangzhou , China, Tel./Fax: This work is liensed under a Creative Commons Attribution 4.0 International Liense (URL: htt://reativeommons.org/lienses/by/4.0/). 72

2 site of the installation by using the organi Rankine yle to generate the shaft work required to drive a vaor omression yle. Ahornratana and Sriveerakul (2010) theoretially analyzed a ombined Rankine vaor-omression refrigeration yle owered by low grade thermal energy. Wang et al. (2011a, b) introdued a novel thermally ativated ooling onet- a ombined yle oules an ORC and a VCC and develoed a rototye with nominal ooling aaity of 5 kw. Demierre et al. (2012) resented the develoment of an ORC-ORC rototye with HFC- 134a as working fluid and heating ower about 20 kw at the ondenser. However, few eole studied ie making using ORC/VCC, eseially ie making utilizing waste heat on food industry. The biggest differene between ie making and air onditioning is that the evaoration temerature for ie making is about -5 C, whih is lower than that for air onditioning, leading to low effiieny and high ressure ratio for omressor used in ie maker. In this study, to utilize the vast amount of waste energy disharged from the exhaust gases and from the engine ooling water in the food industry for ie making, the ORC/VCC system is emloyed and the thermodynami model is develoed and the effets of working fluid tyes, generation temerature, ondensation temerature and evaoration temerature on the system erformane are analyzed in order to demonstrate the feasibility of suh a system for ie making. METHODOLOGY System design: The system of ORC/VCC for ie making in food industry mainly onsists of engine ooling water outlet, engine ooling water inlet, engine exhaust gases outlet, exhaust ort, waste heat boiler, hot water um, generator, exander, omressor, ie maker, throttle valve, ondenser, ooling water um and working fluid um, as shown in Fig. 1. The working rinile of this system is as follows: waste heat olleted from the engine exhaust gases and ooling water rovides energy to heat and vaorize a working fluid with low boiling oint. Energy is extrated from this vaor in an exansion engine that is used to drive a vaor omressor for ie making. Afterwards, the fluid exiting the exander is ondensed and umed bak to generator where it is again vaorized. R134a, R245fa and R600a are, resetively seleted as the working fluid to omare their yle effiieny and to selet the suitable working fluids for ie making. To revent fouling, the exhaust gases do not enter generator diretly and the waste heat boiler is used to reover heat from the exhaust gases. Water is used as the working medium for waste heat boiler and is then umed to generator by hot water um to heat the working fluid. Due to the temerature of exhaust gases about 400 C, the temerature of hot water from Adv. J. Food Si. Tehnol., 8(1): 72-77, Fig. 1: System shemati diagram A: Engine ooling water outlet; B: Engine ooling water inlet; C: Engine exhaust gases outlet; D: Exhaust ort; E: Heat reovery boiler; F: Hot water um; G: Generator; H: Exander; I: Comressor; J: Ie maker; K: Throttle valve; L: Condenser; M: Cooling water um; N: Working fluid um waste heat boiler is generally higher than that of engine ooling water. A vertial generator is used and it is divided into two setions. The hot water from waste heat boiler flows in the uer setion of generator and the engine ooling water flows in the lower setion of generator, as shown in Fig. 1. Counterurrent is alied in generator to imrove the system effiieny. That is, the hot water flows in generator from to to bottom and the working fluid flows from bottom to to in generator. Seawater is an ideal ooling medium for the ORC/VCC system, whih makes the system more omat and more owerful omaring with the system ooled by air. The rogrammable logi ontroller, frequeny onverter and liquid level sensor are suggested to be adoted in the system to automatially ontrol the liquid level of working fluid in generator and ensure the high heat exhange effiieny in generator. Waste heat from the food industry is usually instable beause the engine often works under low load, at idle seed and even is sometimes turned off. Thus, the instable heat soure will seriously imat the erformane of the system. It is an unavoidable roblem when suh a system is ut into ratie. To adat the instability of heat soure, the radial and axial flow exander is emloyed. To imrove the drive effiieny, the omressor and the exander are diretly ouled on the same shaft without gear and ouling. Thermodynami models: To develo the thermodynami models, an assumtion is made that frition and heat losses in the ORC/VCC are negligible.

3 Adv. J. Food Si. Tehnol., 8(1): 72-77, 2015 For ORC: ( ) W = m h h (1) ex 2 3s ex ( h h ) 1s 4 um, w = (2) um, w W m boi ( ) Q = m h h (3) 2 1 W = W W W W (4) net ex um, w um, h um, W net = (5) Qboi T = T T (6) boi h hvh Wum, h mh um, h = (7) v Wum, m um, For VCC: eva = (8) ( ) Q = m h h (9) W i 6 5 ( h h ) 7s 6 om = m (10) i om Wom COP m = W (11) ex Q eva = (12) W om Q eva ie = (13) hie The overall erformane of ORC/VCC is defined as: COP = COP (14) s mie n= 1000 (15) m nr ie h mie = 3600 Q (16) boi RESULTS AND DISCUSSION Considering the instability of hot water from food industry and the temerature variation of seawater in different seasons and laes, the temerature of hot water at generator inlet, T h, is in the range of C and the ondensation temerature is C. For the sake of simlifiation, the evaoration temerature is -5 C and kees invariable and the ower of generator heated by exhaust gases and engine ooling water is 200 kw. The isentroi effiienies for exander, omressor, working fluid um, hot water um and ooling water um are shown in Table 1. Effet of hot water temerature on system erformane: The temeratures of exhaust gases and engine ooling water from food industry vary aording to the oerating onditions of engine, leading to the temerature variation of hot water at generator inlet. As a result, the generation temerature, T boi, varies with T h. Figure 2 and 3 show the system erformane inluding Q eva, n and m ie as a funtion of hot water temerature. In Fig. 2 and 3 and Table 2, the ondensation temerature and evaoration temerature are resetively 40 and -5 C and Q boi is equal to 200 kw and the working fluid for ORC is R245fa and for VCC are resetively R245fa, R134a and R600a. The alulated results show that W ex and inrease with the inreasing T h. This is due to the fat that the ressure, temerature and enthaly at exander inlet inrease with the inrease of T h, resulting in the inrease of enthaly dro between exander inlet and outlet and the inrease of exander ower when the ondensation temerature kees invariable. W ex is 10.36, and kw and is 5, 8.72 and 11.45% when T h is, resetively 80, 120 and 160 C. W om, Q eva and m ie also inrease along with the inreasing W ex. It is obvious from Fig. 2 and 3 that m ie and Q eva deend largely on T h and they inrease with the inrease of T h. Q eva is resetively 37.62, and kw and m ie is resetively 323.5, and kg/h for the working fluid of R245fa, R134a and R600a at T h = 80 C. When T h inreases to 160 C, Q eva inreases to 87.04, and kw and m ie inreases to , and kg/h for the working fluid of R245fa, R134a and R600a, resetively. It is thus lear that there is a great differene in the ie making aability for heat soure with different temerature. There are two main arameters for evaluating the ie making aability of Table 1: Parameter values Parameter ex um, w um, h um, om h ie (kj/kg) Value

4 Adv. J. Food Si. Tehnol., 8(1): 72-77, 2015 Table 2: Relationshi between T h and nr ie T h ( C) nr ie R245fa /kg/kw/h R134a R600a Fig. 2: Effets of heat soure temerature on Q eva and n Fig. 3: Effet of heat soure temerature on m ie hot water, one is the ie yield er ton hot water and the other is the rodution rate of ie er unit ower heat soure and they are resetively reresented by symbols of n and nr ie. In Fig. 2, n is 34.00, and kg/t at T h = 80 C and it inreases to , and kg/t at T h = 160 C for the working fluid of R245fa, R134a and R600a resetively. For the working fluid of R245fa, R134a and R600a, nr ie is 1.62, 1.38 and 1.52 kg/kw/h at T h = 80 C and it inreases to 3.74, 3.20 and 3.53 at T h = 160 C resetively, as shown in Table 2. The above analyses show that T h has an imortant influene on the system erformane and the higher the T h, the greater the nr ie and n. Thus the atual demand of ie for food reservation and aybak eriod should be omrehensively onsidered so as to deide the rated ie making aability during ratial design owing to the invariability of waste heat from food industry. 75 Fig. 4: Effets of ondensation temerature on Q eva and n For a food industry with waste heat ower of 200 kw and R245fa as working fluids for ORC and VCC, nr ie equals to 1.62 and 3.74 kg/ (kw.h) at T h = 80 and 160 C resetively aording to Table 2. That is, the ie making rate, m ie, is resetively 324 and 748 kg/h at T h = 80 and 160 C, whih an omletely meet the demand of ie for food reservation. To simlify the alulation, Q boi is equal to 200 kw and kees invariable in this study. However, Q boi is always variable along with the engine ower outut in ratie and may be greater than or less than 200 kw. If T h and Q boi are 80 C and 100 kw, m ie is 162 kg/h aording to Table 2. m ie inreases to 1122 kg/h if T h and Q boi inrease to 160 C and 300 kw resetively. In Wang et al. (2003) artile, an adsortion ie maker using waste heat from food industry is researhed and ativated arbon-methanol is used as the adsortion working air. The exerimental results show that m ie and nr ie are resetively 15.3 kg/h and 0.45 kg/ (kw.h) when the ower and temerature of waste heat from food industry are 34 kw and 120 C. In Ni et al. (2011) artile, an absortion ie maker with ammonia water as working medium is studied on food industry, m ie and nr ie are resetively 93.1 kg/h and 2.48 kg/ (kw.h) when the exhaust gases temerature and ondensation temerature are 400 and 35 C. When the hot water temerature and ondensation temerature are 120 and 40 C and R245fa is used as the working fluid for ORC and VCC, nr ie equals to 2.83 kg/ (kw.h) in this study, whih is greater than that in Wang et al. (2003) and Ni et al. (2011) artiles. Effet of ondensation temerature on system erformane: The ondensation temerature varies with ambient and the effets of T on Q eva and n are illustrated in Fig. 4. In Fig. 4, the hot water temerature and evaoration temerature are 100 and -5 C and the working fluid for ORC is R245fa and for VCC are, resetively R245fa, R134a and R600a and the ondensation temerature is 20, 30, 40 and 50 C, resetively. The alulated results show that the

5 Adv. J. Food Si. Tehnol., 8(1): 72-77, 2015 Table 3: Comarison of ie making erformane for different medium Working fluid for ORC Working fluid for VCC T h ( C) (%) COP COP s (%) n (kg/t) m ie (kg/h) nr ie (kg/ (kw.h)) R245fa R245fa R245fa R134a R245fa R600a R245fa R245fa R245fa R134a R245fa R600a ressure and enthaly at exander outlet inrease with the inreasing T, leading to the derease of enthaly dro between exander inlet and outlet and the derease of exander ower. The inreasing T also auses the derease of COP and COP s. Observing the rofiles from Fig. 4 it is obvious that Q eva and n deend largely on T and they derease with the inrease of T. For the working fluid of R245fa, R134a and R600a for VCC, Q eva is resetively , and kw at T = 20 C and it dereases to 34.22, and kw resetively at T = 50 C. The temerature of 20 C is a reresentative ondensation temerature at winter in some laes and the temerature of 50 C is a reresentative ondensation temerature at summer in some laes. Taking R600a as working fluid for VCC as an examle, Q eva is kw at winter and it is only kw at summer, indiating that there is a great differene of ie making aability between summer and winter. Thus, the atual demand of ie for food reservation, waste heat ondition and the temerature in winter and summer should be omrehensively onsidered in order to redue the system investment when design an ie maker utilizing waste heat from food industry. Effet of working fluid tyes on system erformane: As evident in Fig. 2 to 4 and Table 2 that the VCC system with R245fa as the working fluid has the otimal system erformane omared with other two working fluids. Table 3 shows the effet of working fluid tyes on the system erformane. In Table 3, the ondensation temerature and evaoration temerature are 40 and -5 C and Q boi equals to 200 kw. The ORC/VCC system with working fluid of R245fa has the maximum of COP, COP s, n, m ie and nr ie omared with two other working fluids. Known from the above analysis, the ORC/VCC system an ahieve otimal erformane when uses R245fa as ORC and VCC working fluid. For the ratial and alied system, if the exander and omressor adot different working fluids, whih uts strit demands on the main shaft seal and gas searating. To sum u, using organi Rankine yle-vaor omression yle for ie making utilizing waste heat from food industry is feasible and the keys are to develo the exander and omressor with high effiieny, eseially the omressor with high ressure ratio. 76 CONCLUSION To effiiently utilize waste heat from food industry exhaust gases and engine ooling water for ie making, the organi Rankine-vaor omression yle system was emloyed and the effets of working fluid tyes, hot water temerature and ondensation temerature on the system erformane were analyzed by develoing the thermodynami models, the following onlusions an be drawn: The ie yield er ton hot water and rodution rate of ie er unit ower waste heat are kg/t and 2.27 kg/ (kw.h) at hot water temerature of 100 C and ondensation temerature of 40 C with R245fa as the working fluid, whih demonstrates the feasibility of using organi Rankine-vaor omression system for ie making from food industry waste heat. The hot water temerature and ondensation temerature have imortant influenes on the system erformane. The ie yield er ton hot water is kg/t at hot water temerature of 100 C and ondensation temerature of 40 C, while it inreases to kg/t at ondensation temerature of 20 C. Thus, the atual demand of ie for food reservation, waste heat ondition and the temerature in winter and summer should be omrehensively onsidered in order to redue the system investment when design an ie maker utilizing waste heat from food industry. NOMENCLATURE COP : Coeffiient of Performane for VCC COP s : Overall Coeffiient of erformane for ORC/VCC h 1 : Enthaly at working fluid um outlet, kj/kg h 1s : Enthaly at working fluid um outlet based on isentroi roess, kj/kg h 2 : Enthaly at exander inlet, kj/kg h 3s : Enthaly at exander outlet based on isentroi roess, kj/kg h 4 : Enthaly at working fluid um inlet, kj/kg h 5 : Enthaly at evaorator inlet, kj/kg h 6 : Enthaly at evaorator outlet, kj/kg h 7s : Enthaly at omressor outlet based on isentroi roess, kj/kg h ie : Phase hange latent heat of hanging water into ie : Mass flow rate for ooling water, kg/se m

6 Adv. J. Food Si. Tehnol., 8(1): 72-77, 2015 m h : Mass flow rate for hot water, kg/se m i : Mass flow rate of working fluid for VCC, kg/se m ie : Ie making rate, kg/se m : Mass flow rate of working fluid for ORC, kg/se n : Ie yields er ton hot water, kg/t nr ie : Prodution rate of ie er unit ower heat soure, kg/ (kw.h) Q boi : Generator heat inut, kw Q eva : Evaorator ower for ie maker, kw T boi : Generation temerature in generator, C T : Condensation temerature, C T h : Hot water temerature at generator inlet, C v : Seifi volume of ooling water, m 3 /kg v h : Seifi volume of hot water, m 3 /kg : Comressor work inut, kw W om W ex : Exander work outut, kw W um, : Cooling water um ower onsumtion, kw W um,h : Hot water um ower onsumtion, kw W um,w : Working fluid um ower onsumtion, kw : Net work outut for ORC, kw : Comressor isentroi effiieny : Exander isentroi effiieny : Organi Rankine yle effiieny : Cooling water um isentroi effiieny : Hot water um isentroi effiieny um,w : Working fluid um isentroi effiieny P : Pressure differene between ooling water um inlet and outlet, kpa W net om ex um, um,h P h : Pressure differene between hot water um inlet and outlet, kpa ACKNOWLEDGMENT The authors gratefully aknowledge the finanial suort from the National Hi-Teh Researh and Develoment Program (863) of China (No. 2012A A053003), the National Natural Siene Foundation of China (No ) and Guangdong Provine and Chinese Aademy of Sienes Comrehensive Strategi Cooeration Projets (2012B ). REFERENCES Ahornratana, S. and T. Sriveerakul, Analysis of a ombined Rankine-vaor-omression refrigeration yle. Energ. Convers. Manage., 51: Demierre, J., S. Henhoz and D. Favrat, Prototye of a thermally driven heat um based on integrated Organi Rankine Cyles (ORC). Energy, 41: Lu, Z.S., R.Z. Wang, T.X. Li, L.W. Wang and C.J. Chen, Exerimental investigation of a novel multifuntion heat ie solid sortion iemaker for food industry using CaCl2/ativated arbon omound ammonia. Int. J. Refrig., 30: Meunier, F., Solid sortion heat owered yles for ooling and heat uming aliations. Al. Therm. Eng., 18: Ni, J., J.H. Gu and J. Shen, Simulation and exerimental investigation of ammonia-water absortion ie-making system for shis. Fluid Mah., 39: Srikhirin, P., S. Ahornratana and S. Chungaibulatana, A review of absortion refrigeration tehnologies. Renew. Sust. Energ. Rev., 5: Wang, D.C. and J.Y. Wu, Influene of intermittent heat soure on adsortion ie maker using waste heat. Energ. Convers. Manage., 46: Wang, S.G. and R.Z. Wang, Reent develoments of refrigeration tehnology in fooding vessels. Renew. Energ., 30: Wang, L.W., J.Y. Wu and R.Z. Wang, Simulation and design of adsortion ie maker for food industry. J. Refrig., 3: Wang, H.L., R. Peterson and T. Herron, 2011a. Design study of onfigurations on system COP for a ombined ORC (organi Rankine yle) and VCC (vaor omression yle). Energy, 36: Wang, H.L., R. Peterson and K. Harada, 2011b. Performane of a ombined organi Rankine yle and vaor omression yle for heat ativated ooling. Energy, 36: Wang, L.W., R.Z. Wang, J.Y. Wu and K. Wang, 2004a. Comound adsorbent for adsortion ie maker on food industry. Int. J. Refrig., 27: Wang, K., J.Y. Wu, R.Z. Wang and L.W. Wang, 2006b. Comosite adsorbent of CaCl2 and exanded grahite for adsortion ie maker on food industry. Int. J. Refrig., 29: Wang, L.W., R.Z. Wang, Z.Z. Xia and J.Y. Wu, Studies on heat ie tye adsortion ie maker for food industry. Int. J. Refrig., 31: Wang, L.W., R.Z. Wang, J.Y. Wu, K. Wang and S.G. Wang, 2004b. Adsortion ie makers for food industry driven by the exhaust heat from diesel engine hoie of adsortion air. Energ. Convers. Manage., 45: Wang, L.W., R.Z. Wang, J.Y. Wu, Z.Z. Xia and K. Wang, A new tye adsorber for adsortion ie maker on food industry. Energ. Convers. Manage., 46: Wang, L.W., R.Z. Wang, Z.S. Lu, Y.X. Xu and J.Y. Wu, 2006a. Slit heat ie tye omound adsortion ie making test unit for food industry. Int. J. Refrig., 29: Wang, L.W., R.Z. Wang, J.Y. Wu, Y.X. Xu and S.G. Wang, Design, simulation and erformane of a waste heat driven adsortion ie maker for food industry. Energy, 31: