22 May 2008

PROPANE HEAT PUMP WITH LOW REFRIGERANT CHARGE – A SIMULATION BASED DESIGN


In the past the so called flammable refrigerants have already been used in heat
pumps, but due to a low customer acceptance and a lacking support on the part of the
compressor manufacturers most heat pumps have been shifted to conventional refrigerants.
Reduced requirements on deployment for refrigeration cycles and heat pumps with
refrigerant charges less than 150 g and the availability of first samples of cheap compressors
for fridges and freezers with a higher cooling capacity (> 2 kW) made the production of small
heat pumps using propane as refrigerant interesting again.
Based on these conditions an exhaust air heat pump with a heating capacity of 2 kW for
space and tap-water heating has been designed.
To achieve a shorter developmental period the heat pump has initially been set up as a
simulation. Modelica has been chosen as simulation environment using the refrigeration
library TIL. Having a co-simulation with LabVIEW it has even been possible to implement
complex control algorithms.
The test results of a “real” heat pump that has been set up based on simulation results will
be compared to the simulation results of the different levels of development of the
refrigeration library.