Applied Thermal Engineering 24 (2004) 865–872 www.elsevier.com/locate/apthermeng Development of no valve solar ice maker a,* M. Li , C.J. Sun b, R.Z. Wang b, W.D. Cai a a School of Physics and Electronic Information, Yunnan Normal University, Kunming 650092, PR China b Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030, PR China Received 20 February 2003; accepted 5 October 2003Abstract A no valve, ﬂat plate solar ice maker is developed on the basis of previous research achievements of alarge number experiments and theory analysis. There are no valves and measure gauges installed on thisadvanced device, also no moving parts on this device, activated carbon and methanol is used as workingpairs for this no valve solar ice maker. Experimental results under both indoor and outdoor showed thateach subsystem, such as adsorbent bed, condenser, evaporator, demonstrated a good performance onsystem running processes; this no valve solar ice maker prototype is approached to practical application ofmass production from view of cost and techniques. After the successful study of this no valve solar icemaker, two new improved economic solar ice makers are fabricated for mass application in China now. Allthis will accelerate practical application of solid adsorption refrigeration driven by solar energy.Ó 2003 Elsevier Ltd. All rights reserved.Keywords: Solar energy; Ice maker; Advanced development1. Introduction The intermittent solid adsorption refrigeration cycle appears to be logical application for solarcooling, also the activated carbon and methanol seem to be the suitable pair in terms of higherCOP and less expansive than other pairs so far [1,2]. In west China, such as Tibet, a large pro-portion of people live in rural or remote locations where electricity is presently unavailable or farfrom suﬃcient, also the solar radiation is the most suﬃcient in those areas. According to statisticsfrom Tibet, the total sun radiation energy can reach 6000–8000 MJ/m2 per year, and the solar * Corresponding author. Tel.: +86-871-5517093; fax: +86-871-5516058. E-mail address: email@example.com (M. Li).1359-4311/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.doi:10.1016/j.applthermaleng.2003.10.002
866 M. Li et al. / Applied Thermal Engineering 24 (2004) 865–872radiation hours can be about to 1500–3400 h per year. Hence, solar energy resource can be ef-fectively used for solar cooling in food and drugs preservation. Our previous work on solar ice maker has demonstrated the feasibility of the system . Theadsorbent bed was composed in two ﬂat plate collectors, with a total surface area of 1.5 m2 ,activated carbon and methanol was used as working pair. Each subsystem, such as adsorbent bed,condenser, evaporator was connected with valve for ideal operation; also thermocouples andpressure gauges were installed within each subsystem for measuring temperature and pressureparameters of that solar ice maker. The indoor experiments with quartz lamps instead of real solarradiation showed that that solar ice maker can produce 7–10 kg ice when the total insolationaccepted by 1.5 m2 collector was 28–30 MJ. However experiments were not conducted outdoorunder real solar conditions. On the basis of successful experiments, a heat and mass transfermodel of solar ﬂat plate ice maker was established , and the eﬀects of solar collector and en-vironment on the performance of a solar powered solid adsorption refrigerator was analyzedusing this model . Above mentioned experience has helped us in designing a no valve solar icemaker which was tested for the performance in real solar radiation condition. In this paper, wefocus on the design of no valve solar solid adsorption ice maker, also the typical performance ofthe no valve solar ice maker valve was given according to the experiments both under indoor andoutdoor conditions.2. Working principle of the no valve solar ice maker Fig. 1 shows schematic layout of a no valve solar ﬂat plate ice maker. The solar ice makerconsists of a adsorbent bed (2), a condenser (5), an evaporator (7), water tank (8), insulation box(9) as well as connecting pipes. For this system, there are no any reservoirs, connecting valves andthrottling valve, the structure of the system is very simple. The working principle of this no valvesolar ice maker is described as follows. On a sunny day, the adsorbent bed absorbs solar radiation energy, which raises the temperatureof adsorbent bed as well as the pressure of refrigerant in adsorbent bed. When the temperature ofFig. 1. The sketch structure of the no valve solar ice maker: (1) cover plate, (2) adsorbent bed, (3) insulation materials,(4) ice frame, (5) condenser, (6) connecting pipe, (7) evaporator, (8) water tank, (9) insulation box.
M. Li et al. / Applied Thermal Engineering 24 (2004) 865–872 867adsorbent reaches the desorption temperature, the refrigerant begins to evaporate and desorbfrom the bed. The desorbed refrigerant vapor will be condensed into liquid via the condenser andﬂows into the evaporator directly; this desorption process lasts until the temperature of adsorbentreaches the maximum desorption temperature. During night, when the temperature of the ad-sorbent bed reduces, the refrigerant vapor from the evaporator gets adsorbent back in the bed.During this adsorption process, the cooling eﬀect is released from refrigerant evaporation, and theice is formed in the water tank placed inside thermal insulated water box. In general, the performance of solar ice maker are represented in terms of Qref (or ice massgotten in water tank) and the performance eﬃciency COPsolar . They can be expressed as follows: Qref ¼ DxMa Le ð1Þ Dx ¼ xconc À xdil ð2Þwhere xconc is the adsorption capacity before desorption, xdil is the adsorption capacity after de-sorption, Ma is the mass of adsorbent inside adsorbent bed, Le is the latent heat of vaporization. Qref À Qcc COPsolar ¼ R ð3Þ iðtÞ dt RTwhere Qcc ¼ Tce Ma DxCpl dT is the energy used to cool down the refrigerant liquid from con- Rdensing temperature Tc to evaporation temperature Te . iðtÞ dt is the total radiant energy absorbedby the collector during one day operation.3. Construction of no valve solar ice maker3.1. Adsorbent bed Adsorbent bed is the most important part of the solar ice maker and hence the performance ofthe solar ice maker depends highly on the characteristics of the adsorbent bed. Generallyspeaking, a good adsorbent bed must have good heat and mass transfer. Recent research showedthat the aluminum alloy have a stronger catalytic eﬀect on the decomposition reaction under thesolar adsorption refrigeration , therefore stainless steel are used as adsorbent heat transfermetal instead of aluminum alloy although stainless steel has poor heat transfer ability than that ofaluminum alloy. The adsorbent bed is made of ﬂat plate stainless steel box, having surface area1 m2 , also 19 kg adsorbent (activated carbon produced by Hainan province, China) is charged andsealed inside the steel plate box, then selective coating is covered on top surface of the steel platebox. Finally the steel plate box is placed behind two sheets of ﬁbre plastic plates in a thermalinsulated case. The permeability of the ﬁbre plastic plate for solar radiation is about 0.92, which ishigher than that of glass. In order to guarantee better heat transfer between the front side and theadsorbent, many ﬁns (also made of stainless steel) are placed inside the adsorbent bed box incontact with the front side and the activated carbon. The distance between these ﬁns is approx-imately 0.1 m. The thickness of the adsorbent layer is about 0.04 m, the total weight of stainlesssteel metal is about 20 kg, those parameters mentioned above are obtained according to bothprevious experimental results and optimized calculation.
868 M. Li et al. / Applied Thermal Engineering 24 (2004) 865–872Fig. 2. Adsorbent bed (mm): (1) activated carbon, (2) stainless steel plate, (3) heat transfer ﬁns, (4) metallic screen,(5) supporting bar. In order to improve the transfer of methanol vapor through the activated carbon layer, a falsebottom (0.01 m thick in the radial distance) is included in the rear side of the adsorbent bed asmentioned by Pons and Guillemiont . As this ‘‘false bottom’’ is completely open to the cir-culation of vapors, it permits an uniform distribution of methanol in the adsorbent. The schematicdiagram of the adsorbent bed is shown in Fig. 2.3.2. Condenser and evaporator During the process of desorption of methanol, a well designed condenser is needed to reject thedesorption heat. To fulﬁl this condition, the £18 mm copper tubes with £36 mm external alu-minum ﬁns are used as condenser, the total heat transfer areas of the condenser is about 4.5 m2 .The schematic diagram of the condenser is shown in Fig. 3. The evaporator must have suﬃcient volume to collect all the condensed methanol. In order toenhance the heat transfer eﬀect, the heat exchange surface is designed as a series of four trape-zoidal cells shown in Fig. 4, the dimension of the evaporator is 220 mm · 320 mm · 100 mm and Fig. 3. Structure of condenser (mm).
M. Li et al. / Applied Thermal Engineering 24 (2004) 865–872 869 Fig. 4. Sketch of the evaporator (mm).the heat exchange area is about 0.28 m2 . The evaporator is partly immersed in a water tank, whichis made of stainless steel, and both the evaporator and water tank are placed in box covered withinsulation. In this way, it is very simple to remove the ice formed during adsorption cooling in thenight.3.3. Integration of the subsystems The adsorbent bed, condenser, evaporator were checked for vacuum proof and then wereconnected with each other using stainless steel pipe of £19 mm. The whole system was mountedon a frame bracket installed with wheels, so that it can be moved easily when necessary. Only onevalve is installed beside condenser, which helps to vacuumize the whole system as well as to chargethe system with refrigerant. A pressure gauge is installed behind adsorbent bed to check for thepressure conditions in the system. Besides, no any other valves or measured instruments are usedin the system. The photograph of whole system is shown in Fig. 5. Fig. 5. Photograph of the no valve solar ice maker.
870 M. Li et al. / Applied Thermal Engineering 24 (2004) 865–872 In order to ensure that the system can work normally, it is essential that the whole systemshould be vacuum proof. After the system was subjected to 72 h of observation and was certain ofits intactness, about 500 ml methanol was added into this solar ice maker.4. Experimental results Experiments under both indoor simulated with quartz lamp and outdoor conditions werecarried out using above described no valve solar ice maker. Since the system was not instru-mented, the characteristics of solar ice maker is judged only by the ice produced in ice box. TheCOPsolar of solar ice maker can be evaluated as a ration of useful cooling to the total solar incidentradiation. Table 1 shows that 6.0–7.0 kg ice can be obtained under indoor conditions when radiationenergy accepted by collector was about 17–20 MJ/m2 , for these conditions, the COPsolar of thissystem was about 0.13–0.15. The performance of the system in outdoors was demonstrated, thesystem could produce 4.0 kg ice and the COPsolar was about 0.12 when the total insolation energyaccepted by collector was about 16–18 MJ/m2 . Comparing with the typical results carried out byother researchers (shown in Table 2), the performance of the no valve solar ice maker is rea-sonably good both ice mass produced and COPsolar . After experiment in outdoor was being tested for eight months, two new no valve solar icemakers were built again on a factory which traditional refrigeration machine is produced inSeptember 2002. The process of fabrication for these two solar ice makers was progressed ac-cording to procedure standards of the factory, we also made some improving design for theadsorbent bed and condenser. For the adsorbent bed, the thickness of stainless steel plate wasreduced to 0.001 m from previous 0.0015 m, the thickness of adsorbent layer in adsorbent bed boxwas reduced to 0.035 m from previous 0.04 m, the distance between heat transfer ﬁns was 0.05 m.The change mentioned above could add heat transfer eﬀect. The adsorbent was heated in electricstove for 10 h at the temperature of about 200 °C before the adsorbent was charged into ad-sorbent bed box, which will ensure adsorbent having good adsorption or desorption character-Table 1Experimental results of the no valve solar ice maker Experimental Active adsorbed Accepted solar Ice obtained COPsolar Experimental method day collector area radiation energy from solar ice (m2 ) (MJ) maker (kg) 2001/11/08 0.94 19.24 7.0 0.137 Quartz lamp radiation in laboratory 2001/11/15 0.94 17.3 6.0 0.146 Quartz lamp radiation in laboratory 2001/11/18 0.94 16.28 4.0 0.12 Real solar radiation in outdoor 2002/02/28 0.94 17.10 4.5 0.13 Real solar radiation in outdoor
M. Li et al. / Applied Thermal Engineering 24 (2004) 865–872 871Table 2Some typical research results of solar ice maker Research group Working pairs Collector areas Solar radiation COP Ice mass per Reference (m2 ) intensity per day (kg) day (MJ/m2 ) Pons and Activated 6 22 0.12 30–35  Guillemiont carbon–methanol 19 0.10 Headley et al. Activated 2 25 0.02 1.0  carbon–methanol Iloeje CaCI2 and NH3 1.41 12 0.1 1.0 kg/m2  Boubakri et al. Activated 1.0 19.5 0.12 4.0  carbon–methanol Tan et al. Activated 1.1 22 0.09 3 kg  carbon–methanol Lin et al. CaCI2 and NH3 1.6 20 0.08 3.2 kg istics. The thickness of insulation materials was added to 0.05 m for keeping oﬀ heating loss ofadsorbent bed when collector accepts solar radiation. For condenser, eight copper tubes, eachtube having 0.4 m length and diameter of £18 mm, with aluminum ﬁns which has thickness of0.0001 m and about total heat transfer areas of 6.0 m2 are used. The eﬀective collector areas of theimproved no valve solar ice maker is about 1 m2 . The photograph of the improved no valve solarice maker is shown in Fig. 6. The satisfying experimental results were obtained again for these twonew improved no valve solar ice makers. The ice mass produced by each new improved no valvesolar maker is about 5.0 kg per day, the COPsolar is about 0.12–0.14 when the solar ice makerreceives solar radiation about 18–22 MJ/m2 . Fig. 6. Photograph of the improved no valve solar ice maker.
872 M. Li et al. / Applied Thermal Engineering 24 (2004) 865–8725. Conclusions A no valve solar ice maker was built on the basis of the previous research achievements. Thecharacteristics of the no valve solar ice maker appears to be reasonable application in west ofChina, where the solar radiation resource is abundant while the availability of electricity is rel-atively less in most villages. The price of the no valve solar ice maker can be expected no morethan RMB 2000 yun (about US $250) for per solar ice maker with 1 m2 collector. This solar icemaker can produce about ice of 4–5 kg each sunny day under the condition of about 18–22 MJ/m2solar insolation, the no valve solar ice maker is expected to be economical in west of China in nearfuture.Acknowledgements This work was supported by the National Key Fundamental Research Program under thecontract no. G2000026309; the Natural Science Foundation of Educational Ministry of YunnanProvince, China.References  R.E. Critoph, Performance limitations of adsorption cycles for solar cooling, Solar Energy 41 (1988) 21–31.  M. Pons, J.J. Guillemiont, Design of an experimental solar-powered, solid-adsorption ice maker, Trans. ASME, J. Solar Energy Eng. 108 (4) (1986) 332–337.  M. Li, R.Z. Wang, Y.X. Xu, J.Y. Wu, A.O. Dieng, Experimental study on dynamic performance analysis of a ﬂat- plate solar solid-adsorption refrigeration for ice maker, Renew. Energy 27 (2002) 211–221.  M. Li, R.Z. Wang, Heat and mass transfer in a ﬂat plate solar solid adsorption, Renew. Energy 28 (2003) 613–622.  M. Li, R.Z. Wang, A study of the eﬀects of collector and environment parameters on the performance of a solar powered solid adsorption refrigerator, Renew. Energy 27 (2002) 369–382.  E.J. Hu, A study of thermal decomposition of methanol in solar powered adsorption refrigeration systems, Solar Energy 62 (1998) 325–329.  O.S. Headley, A.F. Kohdiwala, I.A. Doom, Charcoal–methanol adsorption refrigerator powered by a compound parabolic concentrating solar collect, Solar Energy 53 (2) (1994) 191–197.  O.C. Iloeje, Quantitative comparison of treated CaCl2 absorbent for solar refrigeration, Solar Energy 37 (4) (1986) 253–260.  J.J. Boubakri, J.J. Guillemiont, Meunier, Adsorptive solar powered ice-maker: experiments and model, Solar Energy 69 (2000) 249–263. Y.-k. Tan, Y. Feng, N.-y. Cui, Study of solar powered adsorption ice maker, Acta Energiae Solaris Sin. 13 (3) (1992) 255–258. G.-p. Lin, X.-g. Yuan, Z.-g. Mei, Solar-powered solid absorption ice maker, Acta Energiae Solaris Sin. 14 (2) (1993) 101–104.