Performance of a Residential Heat Pump Operating in the Cooling Mode With Single Faults Imposed.
Performance of a Residential Heat Pump Operating in the
Cooling Mode With Single Faults Imposed.
Kim, M.; Payne, W. V.; Domanski, P. A.; Hermes, C. J. L.
NISTIR 7350; 173 p. September 2006.
heat pumps; cooling; refrigerants; leakage; air flow;
experiments; steady state; evaluation
System behavior of a R4l0A residential unitary split
heat pump system was investigated. The system was
operated in cooling mode and used a thermostatic
expansion valve (TXV) as the refrigerant expansion
device. Seven artificial faults were tested:
compressor/reversing valve leakage, improper outdoor air
flow, improper indoor air flow, liquid line restriction,
refrigerant undercharge, refrigerant overcharge, and
presence of non-condensable gas in the refrigerant. The
no-fault test results were correlated to produce a
reference model of 2nd order multivariate regressive
polynomials. The reference model used three independent
variables, outdoor air temperature, indoor air
temperature, and indoor dew point temperature, to
correlate all other heat pump features. Standard
deviations of liquid line refrigerant subcooling and
evaporator exit refrigerant superheat were used as the
main indicators for a steady-state detector algorithm.
From the no-fault reference model, heat pump feature
residuals were derived. Since the system was controlled
by a TXV, the system could adapt itself to considerable
external variation. Thus faulty behavior was not as
detectable as it would have been with an orifice
expansion device equipped system. The distinctiveness of
a fault depended on the TXV status. Heat exchanger
faults' effects upon performance depend on the sizing of
the heat exchanger. From the dynamic tests, the system
showed that the most influential factor for dynamic
behavior was the change of the evaporator refrigerant