Viability of an Open-Loop Heat Pump Drying System in South African Climatic Conditions

Solomzi Marco Ngalonkulu () and Zhongjie Huan
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Solomzi Marco Ngalonkulu: Department of Mechanical and Mechatronics Engineering, Tshwane University of Technology, Staatsartillerie Road, Pretoria West, Pretoria 0183, South Africa
Zhongjie Huan: Department of Mechanical and Mechatronics Engineering, Tshwane University of Technology, Staatsartillerie Road, Pretoria West, Pretoria 0183, South Africa

Energies, 2024, vol. 17, issue 10, 1-14

Abstract: Drying agricultural produce consumes a considerable amount of energy. As an energy-efficient system, a heat pump can improve the energy efficiency of the drying process and hence reduce the energy consumption, especially in South Africa, where both sub-tropical and temperate weather conditions dominate. The objective of this research is to experimentally investigate the impacts of weather conditions on the operational conditions and thermal performance of an open-loop air-source heat pump drying system. The experimental investigation was conducted in a climate chamber where the climate conditions were simulated from −10 °C to 20 °C with an interval of 10 °C for the typical temperature range of the harvesting season in South Africa. The findings indicate that ambient temperatures have a significant impact on both the operating conditions and thermal performance of an open-loop heat pump system; the change in ambient temperatures from −10 °C to 20 °C leads to a 141.6% improvement in the suction pressure, a 214.2% increase in the discharge pressure, and 30.1% increase in the compression ratio, as well as a consequent increase of 130.6% in the refrigerant mass flow rate (from 0.0067 to 0.0155 kg/s), resulting in a corresponding increase in the coefficient of performance (COP) of the heat pump drying system by about 42.1%. Therefore, this study suggests that, while using an open-loop air-source heat pump drying system utilising R134a refrigerant is feasible in South Africa, it may be practically limited to regions with warm climates or during warmer seasons.

Keywords: heat pump drying; ambient temperatures; thermal performance; mass flow rate; COP (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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