|Title:||Designing and Optimizing Systems for Compressor Rapid Cycling
|Author(s):||Uribe, T.; Bullard, C.W.; Hrnjak, P.S.
|Abstract:||The purpose of this project is to explore the system design implications of compressor rapid cycling. An
earlier project yielded promising results for a typical 2-ton residential split system. It showed that cycle periods as
long as 10-25 seconds should be able to produce COP’s comparable to those achievable with variable speed
compressors. This project builds on those results and aims to develop ways of designing heat exchangers and other
components to fully capitalize on this technology.
Even though the experimental program only includes residential systems, most findings all are also relevant
for automotive applications where clutch-cycled open compressors are used. This project assumes that rapid cycling
is possible by many means, some of them already in the market, and some still to be developed.
Earlier work identified the four most important factors that account for the difference between cycle
efficiencies of systems with continuous (variable speed) and rapid-cycling compressors: 1) refrigerant-side
temperature difference (heat transfer resistance); 2) refrigerant-side pressure drop; 3) heat exchangers thermal
capacitance; and 4) refrigerant backflow through the compressor during off-cycle. Results suggested that
microchannel heat exchangers may offer significant advantages for rapid cycling systems This project was designed
to test that hypothesis.
Several system configurations were conceived and tested, namely: 1) direct expansion (DX); 2) flash gas
bypass (FGB) 3) high side receiver and 4) high side receiver with suction line heat exchanger (SLHX) all with a
microchannel evaporator. Also different alternatives for minimizing each of the loss terms have been analyzed,
analytically and experimentally. The results of those experiments and analyses are the subject of this report.
|Publisher:||Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
|Series/Report:||Air Conditioning and Refrigeration Center TR-220
|Sponsor:||Air Conditioning and Refrigeration Project 134
|Date Available in IDEALS:||2009-06-12