A/C/R Compressors That Work With CO2

September 30, 2000
/ Print / Reprints /
ShareMore
/ Text Size+
WEST LAFAYETTE, IN — Talk continues about the possibility of CO2 being used as a refrigerant in place of HFCs. But as the talk increases, so too do questions.

One set of concerns centers on making compressors work with the natural refrigerant. Some studies were reported on at the Inter-national Institute of Refrigeration’s Gustav Lorentzen Conference on Natural Working Fluids at Purdue University here.

Employees of Sanyo Electric Co. reported on the company’s development of a CO2 hermetic compressor for practical use. They reported that the compressor, with two rolling pistons, operates with two-stage compression and two cylinders for pressure deference.

“In the first stage, the suction gas is raised to about 5 to 6 Mpa (intermediate pressure). And inner pressure of the shell case is intermediate pressure to minimize gas leakage between compressing rooms and the inner space of the shell case.”

The researchers stated that the compressor “achieved high efficiency and high reliability. This could facilitate the development of environmentally friendly home-use refrigerators and air conditioners.”



Reciprocating Units

Next, engineers at Shizuoka University looked at CO2 in reciprocating compressors. They assembled a prototype and noted that piston rings “functioned well as a means of sealing in the CO2 under high-pressure operation.

“However, some leakage flowing backward through the valves existed, and it affected performance of the compressor with a relatively small stroke volume.” So, “some oil was mixed into the suction vapor intentionally. The oil was supplied from an oil reservoir having a function of oil separator in the discharge line of the compressor.”

While such a compressor does work, the researchers said it is necessary “to take great care of the estimation of the clearance volume and the valve leakage.”

Scroll Prototype

There was also research done by Matsushita with hermetic scrolls using CO2. The company built a prototype similar to a medium-capacity scroll. Displace-ment volume was set to obtain a capacity range of 2.5 to 5.0 kW when operated by a 30- to 60-Hz ac inverter.

The company reduced the “wrap height in proportion to the displacement volume. The volume ratio was modified by changing the number of wrap windings to take into consideration the smaller compression ratio” of CO2 vs. R-410A refrigerant.

A key finding: “The volumetric efficiency and the compressor efficiency were improved as operating speed increased. Although the volumetric efficiency of a CO2 scroll compressor was expected to be substantially lower than that of an R-410A compressor due to the large pressure difference between suction and discharge, the difference in fact remained extremely small.”



Semi-Hermetic Research

Finally, there was research on two-stage semi-hermetics done by SINTEF Energy Research in Norway. The researchers developed a series of single- and two-stage compressors with two cylinders running at nominal speeds of 2,900 rpm.

According to a report, “Measurements on the two-stage CO2 compressors show that very good efficiencies can be achieved at low-temperature applications compared to a one-stage compressor.

“Using a two-stage compressor also increases the flexibility in the overall system design.”

Publication date: 10/02/2000

Did you enjoy this article? Click here to subscribe to The NEWS Magazine

Recent Articles by Peter Powell

You must login or register in order to post a comment.

Multimedia

Videos

Image Galleries

2014 MCAA Annual Convention

Scenes from the 2014 MCAA Annual Convention in Scottsdale, Ariz.

Podcasts

NEWSmakers: Julian Scadden

Training is an ongoing process. Julian will discuss how you can generate maximum return on time and energy invested training by following a three part process. Listen to this podcast to get expert tips on training, tracking and follow up. 

More Podcasts

THE MAGAZINE

ACHRNEWS

NEWS 04-14-14 cover

2014 April 14

Check out the weekly edition of The NEWS today!

Table Of Contents Subscribe

SERVICE CALLS POLL

Which statement on service calls best applies to your business?
View Results Poll Archive

HVACR INDUSTRY STORE

plumbing-hvac.gif
2014 National Plumbing & HVAC Estimator

Every plumbing and HVAC estimator can use the cost estimates in this practical manual!

More Products

Clear Seas Research

 

Clear Seas ResearchWith access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

DON'T MISS A THING

Magazine image
 
Register today for complete access to ACHRNews.com. Get full access to the latest features, Extra Edition, and more.

STAY CONNECTED

facebook icontwitter iconyoutube iconLinkedIn i con