Potential Coefficient of Performance Improvements Due to Glide Matching With R-470C.
Potential Coefficient of Performance Improvements Due to
Glide Matching With R-470C.
(616 K)
Marques, M. E.; Domanski, P. A.
International Refrigeration Conference at Purdue, 7th.
Proceedings. July 14-17, 1998, West Lafayette, IN,
1998.
Keywords:
alternative refrigerants; air conditioner; coefficient
of performance; glide matching; heat pumps;
refrigerants; thermodynamics; zeotropic mixtures
Abstract:
Potential improvements of the Coefficient of Performance
(COP) were investigated for R-407C at cooling and
heating conditions of a residential heat pump. The
study used CYCLE-11, a semi-theoretical
vapor-compression cycle model, which was upgraded to
simulate cross-flow, counter-flow, and parallel-flow
evaporator and condenser with no restructions on
specifying superheated vapor and subcooled liquid
regions. The COP benefit of using counter-flow heat
exchangers in a low-life air-conditioning application
was found to be 7.1% when compared to a system with a
cross-flow evaporator and condenser. For heating
conditions (high-life application), the predicted
benefit was 3.6%. These results are representative of a
water-to-water system, where counter-flow heat
exchangers are suitable for implementing glide matching.
Since air-to-refrigerant heat exchangers are not
counter flow but rather cross-counter flow (in the best
case), the potential to improve COP in a practical air
conditioner is lower. The COP penalty caused by glide
mismatch (parallel flow) is approximately twice as
severe as the benefit that can be realized from glide
matching.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899