Study of heat pump operating parameters related to controls and performance including variable speed and transient effects
Abstract
A parametric investigation of compressor speed, indoor unit air flow rate, refrigerant charge amount, and thermostatic expansion valve static superheat setting was conducted in relation to variable speed and transient operation of residential heat pump systems. Cooling mode operation was examined experimentally and heating mode operation was investigated numerically. Single and variable speed seasonal performance was computed and compared. For one system, little advantage in variable speed seasonal energy efficiency ratio (SEER) was found, and there was no seasonal energy consumption advantage. For a second system, some cooling mode advantage to operating in variable speed mode was found (SEER benefit approximately 5%, and the seasonal energy consumption savings approximately 2%) but no advantage to operating in variable speed mode in the heating mode was found. The systems studied had reciprocating compressors driven with electronic inverter speed drives. Parameters such as compressor efficiency and heat exchanger effectiveness were examined, as well as the influence of indoor air flow rate and charge amount, in conjunction with variable compressor speed operation. A detailed computer model was modified and used to investigate the influence of operating parameters on performance and the program was found to be an accurate tool useful for control studies. A simplified steady-state model was explored for use in fast predictions of control effects and for possible use on "on-board" microprocessors. Similarly, a simplified transient system model was developed and was verified with experimental system start-up data. The simplified transient model was found to be capable of tracking the effect of charge on system start-up response. The computational speed and reasonable accuracy of the simplified model illustrated its potential for further study of control effects and possible on-board use with microprocessor based controls.
Degree
Ph.D.
Advisors
Goldschmidt, Purdue University.
Subject Area
Mechanical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.