23 September 2011

THERMODYNAMIC ANALYSIS OF MODERATE/HIGH TEMPERATURE HEAT PUMP SYSTEM USING WATER AS WORKING FLUID


Water is an environment-friendly, low-cost and harmless natural working fluid, of
which ozone depletion potential (ODP) is zero and global warming potential (GWP) less than
1, and it is a better alternative fluid for moderate/high temperature heat pump. The
thermodynamic performances of moderate/high temperature heat pump system using water
as working fluid are analyzed when the condensation temperature varies from 50 °C to 140 °C.
The results demonstrate that the working fluid of water owns lower operation pressure and
heat capacity per displacement than the others, but higher pressure ratio and discharge
temperature. The coefficient of performance (COP) of the system using water as working fluid
changes almost linearly with the condensation temperature, and is higher than the other fluids
when it keeps more than 95 °C and comparative to others when it is between 70 °C and 95 °C,
lower when it keeps less than 70 °C. Generally, water is a prospective working fluid for
moderate and high temperature heat pump system.