Experimental performance investigation of a horizontal ground source compression refrigeration machine

Abstract

SUMMARYIn this paper, the effect of various system parameters on horizontal ground source compression refrigeration machine (CRM) performance is studied experimentally in Bursa, Turkey. A ground heat exchanger (GHE) system connected to CRM in a test room in the air conditioning and refrigeration laboratory of Uludag University has been designed and constructed. This system was tested for space cooling in August and September 2004 and performance tests were performed during this period. Overall, system mainly consists of the GHE (GHE-water circuit) and CRM (CRMrefrigerant circuit). Refrigerant is R134a. Hourly variations of inlet and outlet water temperatures, extracted heat from test room, rejected heat to ground, compression ratio, total power consumption, and coefficient of performance (COP) values for both whole system and only CRM are obtained. Thermal properties of soil are also estimated by using experimental data and theory. Cooling load of test room and rejected heat to ground, and all COP values are also presented. Finally, heat rejection rate to ground with respect to leaving water temperature from GHE is given. The COP of the overall system changes between 2 and 2.5, also CRM COP values are in the range of 3 and 3.86.

Experimental study of horizontal ground source heat pump performance for mild climate in Turkey

“…amortisation factor C I annual investment cost (V) (C OM ) PW present worth of annual operating and maintenance costs (V) COP hp coefficient of performance of the heat pump COP sys overall coefficient of performance of the system c pa air specific heat (J kg À1 K À1 ) c pw water specific heat (J kg À1 K À1 ) C T total annual cost (V) C T temperature matrix T a outdoor temperature ( C) T aci temperature of air at condenser inlet ( C) T aco temperature of air at condenser outlet ( C) (TC OM ) PW total present worth of the costs (V) T r indoor temperature ( C) T ev evaporating temperature ( C) T cd condensing temperature ( C) T ps 1/8 surface temperatures of pipes between inlet and outlet pipes (K) T s soil temperature at a depth of 2 m ( C) T sur surface temperature (K) T wi temperature of antifreeze solution at GHE inlet ( C) T wo temperature of antifreeze solution at GHE outlet ( C) T 1 temperature of refrigerant at evaporator outlet ( C) T 2 temperature of refrigerant at compressor outlet ( C) T 3 temperature of refrigerant at condenser outlet ( C) T 4 temperature of refrigerant at evaporator inlet ( C) …”

“…A water-to-air type GSHP system connected to a test room in the air conditioning and refrigeration laboratory of Uludag University, Bursa, Turkey was designed and constructed first for cooling mode application [1]. This experimental set up was modified to reverse the cycle by adding a four way valve (reversing valve) to the compressor exit, a thermostatic expansion valve and a check valve to the evaporator inlet, and another check valve to the condenser exit.…”

“…In this study moisture and dry density of the soil are estimated as 15% and 1920 kg/m 3 from ASHRAE (1997) [43]. Thermal conductivity of soil was also estimated as 2.0 W/mK, and other estimated thermophysical properties of soil can be found in [1] and not repeated here. But for comparison, another estimate of the soil thermal conductivity was obtained as 1.75 W/mK for 0.17 sand fraction using improved Johansen's method [44,45] in conjunction with Murray and Verhoef's study [46].…”

“…Soil thermal conductivity value is estimated and compared with cooling case [1] for reliability purpose and higher value was used in numerical heat transfer analysis by considering possible moisture increase in the soil due to rainfall amount. As a result of steady-state numerical conduction analysis, thermal interaction can be treated as especially important for first three rows.…”

Performance analysis of a solar-assisted ground source heat pump system in climatic conditions of Turkey

“…Turkey has a great solar energy potential and the use of solar-assisted heat pump (SAGSHP) systems is an important alternative option for more efficient use of RES. However, only a few studies on GSHP systems have been conducted in Turkey [3][4][5][6][7] and only one of them is related to SAGSHP systems [7]. These SAGSHP systems are also known as hybrid systems due to their double sources of heat (soil and Sun).…”