Performance and Reliability of Direct-Expansion Ground-Coupled Heat Pumps

Direct Expansion Ground-Coupled Heat Pumps are potentially the most efficient vapor compression-based air conditioning system, but are not very popular due to the numerous operational and design issues they are plagued with: shortage of field studies, oil return to the compressor, expansion valve hunting, refrigerant flow mal-distribution in parallel loops, high pressure drops and gains in the ground heat exchanger, variable speed operation of the compressor, lack of reliable numerical models of the ground heat exchanger and of the whole system and lack of generalized design guidelines. This seminar discusses these issues and possible solutions to them.