System COP of Ejector-Based Ground-Source Heat Pumps

Abstract

Compared to mechanical compressors, ejector-based refrigeration systems can make direct use of many forms of thermal energy, including waste heat, solar thermal, or biogases. It is known that SE systems have a lower thermal efficiency compared to mechanical compressors because of their lower performance at high compression ratios. In the present work, binary fluid ejector heat pumps with high efficiency are presented based on a proper selection of the binary fluids and the ejector geometry for specific operating conditions of a ground-source heat pump cooling system (GSHP). The existing literature on ejector-based refrigeration systems considers the thermal COP and does not account for many energy losses across the system. In the present paper, the system COP of an ejector-based GSHP that accounts for all energy exchange processes is determined. A method for the calculation of the work done by the boiler feed pump, the refrigeration expansion valve, and the ground loop circulation pump is presented. The influence of the condenser temperature on the entrainment process and the system COP is also discussed. The estimated overall system COP for the three top-ranked binary fluid candidates under various operating conditions was found to range from 1.55 to 3.06.

Numerical and Experimental Investigation of Supersonic Binary Fluid Ejector Performance

“…Therefore, the outcomes of the present study can be useful in refrigerant selection for practical applications. Further analysis on the effect of other system energy exchanges on the system COP was discussed in [15,22].…”

“…It is common practice to utilize RANS-based turbulence models to analyze the performance of ejectors in axisymmetric flows; this provides adequate predictions of the static pressure, the temperature and the entrainment ratio, but it should be noted that the choice of the RANS model for analyzing the flow inside an ejector depends on the operating conditions. Typically, the SST (shear stress transport) k-ω model [13][14][15] or realizable k-ε model [16,17] are commonly used.…”

Interdisciplinary Studies of Jet Systems using Euler Methodology and Computational Fluid Dynamics Technologies

“…In an example where the variable is the critical cross-sectional area at the nozzle, the control is performed by linear movement of the central body [55][56][57]. Ejector systems can directly use many types of energy [58]. There are examples of using several different working fluids in an ejector [59][60][61].…”