Laboratory evaluation of the heating capacity and efficiency of a high-efficiency, air-to-air heat pump with emphasis on frosting/defrosting operation

Technical Report · Wed Dec 01 00:00:00 EST 1982

OSTI ID:6601752

Miller, W A

A high-efficiency, air-to-air split-system residential heat pump of nominal 3-ton capacity was instrumented and tested in the heating mode under laboratory conditions. Performance of the system was measured during steady-state, dehumidifying, and frosting-defrosting conditions, with major emphasis placed on the dynamic frosting operation of the system. The study encompassed an evaluation of system and component performance for ambient temperature levels betwen 8.3 and -8.3/sup 0/C (47 and 17/sup 0/F respectively) and for discrete humidity levels ranging from 50 to 90%. The heat pump coefficient of performance (COP) and capacity, measured at 4.4/sup 0/C (40/sup 0/F) as a function of time after system start-up, decreased with time because of frost accumulation on the outdoor heat exchanger but increased with increasing ambient relative humidity. At ambient temperatures less than 4.4/sup 0/C (40/sup 0/F), the COP and capacity degradations caused by frost formation increased with increasing relative humidity because of greater frost accumulation of the outdoor heat exchanger. Experimental results revealed that both unnecessary and late defrosting operations occur when a time-and-temperature defrosting control is used. Concepts of advanced defrosting controls that could feasibly reduce both frosting and defrosting losses were developed from experimental data. Frosting caused greater degradation of heating capacity than defrosting did. Cumulative frosting loss coefficients were calculated as a function of time, temperature, and relative humidity and are applicable to modeling of frosting losses calculated in a seasonal performance program.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 6601752
• Report Number(s): ORNL/CON-69; ON: DE83005168
• Resource Relation: Other Information: Portions of document are illegible. Printed copy available until stock is exhausted
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
AIR SOURCE HEAT PUMPS
DEFROSTING
PERFORMANCE TESTING
AMBIENT TEMPERATURE
CAPACITY
COEFFICIENT OF PERFORMANCE
DATA PROCESSING
DEHUMIDIFICATION
EFFICIENCY
EXPERIMENTAL DATA
FLOW RATE
FROST
REFRIGERANTS
SENSITIVITY ANALYSIS
STEADY-STATE CONDITIONS
TEST FACILITIES
DATA
FLUIDS
HEAT PUMPS
ICE
INFORMATION
NUMERICAL DATA
PROCESSING
TESTING
WORKING FLUIDS
320101* - Energy Conservation
Consumption
& Utilization- Residential Buildings- (-1987)