30 May 2005


A dual-loop heat pump/air conditioning system for automotive applications is presented in this
article. Conventional automotive heating systems have a continuing problem in cold weather due to
inadequate thermal energy supply to passenger cabin during the initial engine warm-up. The proposed
dual-loop system design may overcome the delayed heating problem, so that the passenger cabin is heated
shortly after engine start-up in winter conditions. Furthermore, using special four-way valves makes it
possible to switch between heating and cooling modes in the dual-loop system for varying outdoor
conditions. Performance of both the system components and the integrated system were tested under
various conditions. The thermo-hydrodynamic performance of the heat exchangers within the system was
previously analyzed by the coauthors. However, the experimental results and the developed heat transfer
and pressure drop correlations are reviewed and presented in this article. For the integrated system,
variation of the coefficient of performance versus system variables are analyzed, plotted, and discussed.
The results of extensive system testing show that the heat pump coefficient of performance varied from 2
to 5 depending on the outdoor air conditions. It appears that, with system optimization, the proposed dualloop
heating/cooling system would be viable for automotive applications.