Experimental evaluation of ground source heat pump system under hot climate conditions

The increasing demand to have sustainable cooling systems in hot climates underscores the need to have efficient cooling systems with minimum consumption of electricity. Conventional air source heat pump (ASHP) cannot operate efficiently at high ambient temperature; therefore, they are not appropriate for such localities as Iraq. This paper aimed to solve this disadvantage, a Ground Source Heat Pump (GSHP) system was designed, constructed and then tested in the climatic condition of Baghdad. Originality of work is in creating and experimentally justifying water-cooled vapor compression system that is based on vertical ground heat exchanger (GHE) combined in an actual air conditioning system. The experimental rig comprised 10 m deep, 0.2 m diameter borehole with copper U-tube exchanger connected to 2 kW cooling system serving 4 m × 2 m × 3 m test room. Performance was evaluated for different condenser water flow rates between 1 and 7 L/min. Results showed the maximum heat rejection rate reached 79.7W/m, with a heat pump coefficient of performance (COPhp) of 3.46 and an overall system coefficient of performance (COP) of 1.88 at an optimal flow rate of 3 L/min. The average groundwater temperature remained stable at 17°C, decreasing by 0.37°C per meter depth. The GSHP system recorded high energy saving relative to the air-cooled systems and this justified its usability in hot and dry areas. The given work is the first detailed experimental data about the GSHP functioning under the Iraqi climatic conditions and it proves that ground-coupled systems could significantly increase the cooling efficiency, decrease the electrification, and facilitate the sustainable building energy policies within the same environment.