PERFORMANCE EVALUATION OF HYBRID SOLAR AIR- WATER HEATER WITH VARIOUS INLET AIR TEMPERATURE DURING HEATING PROCESS

Transcription

1 Choi Hwi-Ung et al. Speial Issue Vol. 1, Issue 1, pp. 1-5 PERFORMANCE EVAUATION OF HYBRID SOAR AIR- WATER HEATER WITH VARIOUS INET AIR TEMPERATURE DURING HEATING PROCESS Choi Hwi-Ung Graduate Shool of Refrigeration and Air-onditioning Engineering, Pukyong National University, Busan, Republi of Korea, Yoon Jung-In Department of Refrigeration and Air-onditioning Engineering, Pukyong National University, Busan, Republi of Korea, Son Chang-Hyo Department of Refrigeration and Air-onditioning Engineering, Pukyong National University, Busan, Republi of Korea, Choi Kwang-Hwan Department of Refrigeration and Air-onditioning Engineering, Pukyong National University, Busan, Republi of Korea, Abstrat Researh about hybrid solar air-water heater that an heating both air and liquid has been onduted for enhaning the usage of solar thermal energy. In the previous study, thermal effiieny of this olletor was investigated with many operating and external onditions, but all of previous experiment onduted using outdoor air as inlet air of olletor. Thus, in this study, the performane hange of hybrid solar air-water heater was investigated with hange of inlet air temperature during air and liquid were heated simultaneously. As a result, thermal effiieny for liquid heating was inreased with inrement of the inlet air temperature. On the ontrary to this, thermal effiieny for air heating of olletor was dereased with inrement of inlet air temperature. In ase of total thermal effiieny of olletor onsidered air and liquid heat gain, it was also dereased with inrement of inlet air temperature. From these results, it was 1

2 onfirmed that using outdoor air diretly as inlet air of olletor is better for the use of solar energy. However it is hard to onlude that whih is better between using outdoor air and heated air on the perspetive of energy saving of building beause heat storage performane was inreased if the return air or any heated air is used as inlet air of hybrid solar air-water heater when air and liquid was heated simultaneously even air and total thermal effiieny is dereased. Thus, the neessity of more profound study and onsideration about this as a further study was also onfirmed. Keywords Solar thermal energy, Flat plate solar olletor, Heat pump, Energy onservation 1. Introdution With onerns about exhaustion of energy and environmental pollution aused by inrement of fossil fuel usage, many researhes for improving the effiieny of renewable energy have been onduted. As a part of these trends, researh about hybrid solar air-water heater has been onduted for enhaning the use of solar thermal energy. The hybrid solar air-water heater is flat plate solar olletor that an heating air and liquid respetively or simultaneously, while traditional flat plate solar olletor an heating only one of air and liquid. Thus, this olletor an be applied to hot water supply system as well as air-onditioning system in winter. And also it an be used for making heat soure that regenerating liquid desiant of liquid desiant ooling system in summer. So, many previous studies was onduted for developing this olletor with many operating and external onditions(k.h. Choi et al, 2014), (H.W. Choi et al, 2014, 2015), but all of previous experiment onduted using outdoor air as inlet air of olletor. Thus, in this study, performane hange of hybrid solar air-water heater was investigated with hange of inlet air temperature during air and liquid were heated simultaneously and onfirming the effet of inlet air temperature of olletor on thermal effiieny. 2. Experimental apparatus and method Hybrid solar air-water heater is flat plate solar olletor that an heating both air and liquid by installing air hannel beneath absorbing plate. It is omposed of nine air hannels with 2

3 nine liquid pipes and fins are installed in an air hannel for improving heat transfer from absorbing plate to flow air. Absorbing area is approximately 2m 2 and it is loated in Busan, Republi of Korea. Shemati and atual view of hybrid solar air-water heater are shown in Figure 1. (a) (b) Figure 1: Shemati and atual view of hybrid solar air-water heater; (a) shemati of hybrid solar air-water heater (b) atual view Experiment was onduted on onstant liquid and mass flow rate at lear day. Inlet air of olletor was heated by eletri heater and the temperature differene between inlet air and ambient was set as 0ºC, 13 ºC and 23 ºC. As a measuring devies, T-type thermoouple, PT100 were used for air and liquid temperature and testo435, turbine flowmeter were used for air and liquid mass flow rate. In ase of solar irradiane, pyranometer was used. Thermal effiieny of olletor an be defined as the ratio of the useful gain over some speified time period to the inident solar energy over the same time period(duffie J.A. & Bekman W.A., 1991), (M.A. Karim & M.N.A. Hawlader, 2004). Thus, thermal effiieny for air and liquid heating and total thermal effiieny of olletor an be written as equation (1), (2) and (3). Q dt m C p, ( T, out T, in) dt = = (1) GA dt A Gdt. 3

4 Qairdt mair C p, air ( Tair, out Tair, in) dt air = = (2) GA dt A Gdt Qt dt Qairdt + = GA dt A. Qdt t = (3) Gdt 3. Result and disussion Average daily heat gain and thermal effiieny in olletor are shown in Figure 2 with respet to temperature differene between inlet air and ambient. Heat gain of liquid was inreased slightly with inrement of temperature differene on the similar solar irradiane. But, heat gain of air and total heat gain were shown signifiant deline with inrement of temperature differene. In ase of thermal effiieny, thermal effiieny for liquid heating was shown from 10% to 15% and it was inreased with inrement of inlet air temperature similar with heat gain beause heat transfer from liquid to air was dereased. On the ontrary to this, thermal effiieny of air was dereased with inrement of inlet air temperature and it was shown from 15% to 50%. In ase of total thermal effiieny, it was shown from 30% to 60% and it was also dereased with inrement of inlet air temperature similar with thermal effiieny for air heating. (a) (b) Figure 2: Heat gain and thermal effiieny with respet to temperature differene between inlet air and ambient; (a) heat gain (b) thermal effiieny 4

5 4. Conlusions In this study, performane of hybrid solar air-water heater was investigated with hange of inlet air temperature when the air and liquid were heated simultaneously. As a result, thermal effiieny for liquid heating was inreased with inrement of inlet air temperature. But thermal effiieny for air heating and total thermal effiieny of olletor were dereased with inrement of inlet air temperature beause the derement of thermal effiieny for air heating was more than inrement of thermal effiieny for liquid heating. Thus, using outdoor air diretly as inlet air of olletor is onsidered as a better way for the use of solar energy. But it is hard to onlude that whih is better between using outdoor air and heated air on the perspetive of energy saving of building beause heat storage performane was inreased if the return air or any heated air is used as inlet air of hybrid solar air-water heater. So, the neessity of more profound study and onsideration about this as a further study was also onfirmed. REFERENCES K.H. Choi, J.I. Yoon, C.H. Son, H.W. Choi, B.A. Kim, (2014). Journal of the Korean Solar Energy Soiety. Experimental Study for Thermal Performane of Hybrid Air-Water Heater Using Solar Energy during Heating Medium Working Simultaneously, Vol. 34, No. 3, pp H.W. Choi, J.I. Yoon, C.H. Son, K.H. Choi, (2014). Journal of the Korean Solar Energy Soiety. Performane Estimation of Hybrid Solar Air-Water Heater on Single Working of Heating Medium, Vol. 34, No. 6, pp H.W. Choi, Fatkhur Rokhman, J.I. Yoon, C.H. Son, K.H. Choi, (2014). Journal of the Korean Solar Energy Soiety. A Study on the Thermal Storage Performane and Charateristis of Daily Operation of Hybrid Solar Air-Water Heater, Vol. 35, No. 3, pp Duffie J.A., Bekman W.A., (1991). Solar engineering of thermal proesses(p. 252). New York: Wiley. M.A. Karim, M.N.A. Hawlader, (2004). Energy Conversion and Management. Development of solar air olletors for drying appliations, Vol. 45, Issue. 3, pp