Air-to-water heat pumps using CO2 as a natural refrigerant have been developed and commercialized. They are expected to contribute to energy saving in residential hot water supply. The objective of the research is to analyze the performance of a water heating system composed of a CO2 heat pump...

The cascade refrigeration system has been applied to heat pump water heaters to overcome the problems which arise from the high compression ratio at low ambient temperature. In this study, the performance of a cascade heat pump water heating system is investigated with a quasi-steady state...

In residential applications, an air-to-water CO2 heat pump is used in combination with a domestic hot water storage tank, and the performance of this system is affected significantly not only by instantaneous ambient air and city water temperatures but also by hourly changes of domestic hot...

The objective of this study was to use both field data and a numerical simulation to examine the long-term performance and environmental effects of a large GSHP (ground source heat pump) system that heats and cools industrial greenhouses in a cold region. A large vertical GSHP system was...