Testing and modeling of compressors for low-lift cooling applications

In this thesis, an inverter-driven variable speed scroll compressor is tested on a de-superheater test stand to determine its performance in areas of low-lift and low compressor speed. The goal is to adapt this test stand so that it could be used to test a reciprocating compressor in this region. A control program is written to maintain a constant saturated suction temperature, suction temperature, and saturated discharge temperature. The program was able to maintain control with errors of ±0.2 °C at most points. At each test point, refrigerant mass flow rate, compressor input power, and discharge temperature is monitored. The amount of heat removed by the condenser was within 7% of the compressor input power and the inverter efficiency was within 5% of the compressor input power for all test points. The inverter efficiency is lowest at low speed. The isentropic efficiency is found to drop off significantly for low pressure ratios. A similar drop off is not expected for reciprocating compressors, so a model for reciprocating compressors is developed. The model is able to predict refrigerant mass flow rate and compressor input power as a function of shaft speed as well as suction and discharge pressures and temperatures. The model is able to accurately predict the mass flow rate with an RMS error within 0.5% and for the power model, the RMS errors are within 3.6%. The mass flow model is found to perform well when extrapolated into lower speed ranges with RMS errors remaining below 0.5%.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Willingham, Ryan Alexander

Advisor dc:contributor.advisor

• Leslie K. Norford.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/50560

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/50560