Vertical closed-loop groun-source heat pump systems have been installed widely in Korea since they can extract a moderate temperature level of geothermal heat in a relatively small area. For a ground heat exchanger, a vertical closed-loop type with brine circulation is mostly preferred since it is simpler and less harmful to the ground environment. However, it requires a secondary loop between the refrigerant in a heat pump and the brine. By adding a geothermal heat exchanger in the secondary heat exchange loop, circulation pumps should be attached and the temperature difference between refrigerant and ground would be increased, which causes performance degradation. In this paper, performances of direct expansion ground-source heat pump were evaluated mathematically as an alternative to the conventional secondary-loop ground-source heat pump.

An ejector is a simple mechanical device that can be integrated with power generation or the refrigeration cycle to enhance their performance. Owing to the complex flow behavior in the ejector, the performance prediction of the ejector is done by numerical simulations. However, to evaluate the performance of an ejector integrated power cycle or refrigeration cycle, the need for simpler and more reliable thermodynamic models to estimate the performance of the ejector persists. This research, therefore, aims at developing a single mathematical correlation that can predict the ejector performance with reasonable accuracy. The proposed correlation relates the entrainment ratio and the pressure rise across the ejector to the area ratio and the mass flow rate of the primary flow. R141b is selected as the ejector refrigerant, and the results obtained through the proposed correlation are validated through numerical solutions. The comparison between the analytical and numerical with experimental results provided an error of less than 8.4% and 4.29%, respectively.