Enhancing geothermal heat pump systems with parametric performance analyses

Abstract

Parametric performance analyses and comparison of a basic geothermal heat pump, a heat pump cycle with motor cooling/refrigerant preheating, and a heat pump cycle utilizing an economizer with respect to first law is conducted through simulation. Changing compressor, pump, and motor efficiency, along with condenser pressure, evaporator pressure, degree of subcooling at the condenser exit and degree of superheating at the evaporator exit is investigated. Economizer arrangements yield the highest coefficient of performance and resilience to change in COP with variation in evaporator pressure, and degree of superheating and subcooling. The basic vapor compression and motor cooling/refrigerant preheating systems have the lowest COP throughout and greatest resilience to variation in compressor efficiency, motor efficiency and condenser pressure. Motor cooling/refrigerant preheating and economizers have advantages over basic vapor compression cycles. Motor cooling reduces ground loop heat exchanger length with similar COP, and economizers allow for an increase in COP compared to the basic cycle.