Researchers tackle problems with POEs

August 10, 2000
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WEST LAFAYETTE, IN — Problems with POEs? “Duh,” say the contractors and service technicians who encounter them on a daily basis in the field.

You’ve been bugged about them because of their hygroscopy and high cost, to name just two concerns. Then there’s the sludge that shows up in some systems, clogging TXVs and other components.

But you have to use POEs (polyolesters) with the new HFC refrigerants, right?

Researchers, engineers, and scientists are looking for ways to help you with some of your POE-related problems. Several of them made presentations at the most recent International Refrigeration Conference here at Purdue University.

Split-system heat pump test

Researchers from Elf Atochem reported that they have conducted experiments in a split-system heat pump using HCFC-22 with mineral oil and HFC-407C with three different lubricants: POE, alkylbenzene, and mineral oil.

“Test results indicated that the liquid level in the compressor with immiscible lubricants [such as alkylbenzene and mineral oil] was slightly lower than that with miscible lubricants [POEs],” it was noted in a research paper.

“However, the oil level with immiscible lubricants held steady and within acceptable levels, indicating more oil in circulation in the system,” the paper continues. “The difference in both capacity and COP [coefficient of performance] when R-407C was used in any of the three lubricants were small.”

The report did caution that “It is necessary to determine what the limiting cases are.”

Improving performance: The 'acid catchers'

Other researchers reported on ways to make POEs work better.

Copeland Corp., for example, looked at ways to use what it called an “acid catcher” to “improve the hydrolytic stability of ester lubricants.”

The researchers garnered chemicals (with tongue-twisting names) from several chemical companies, and conducted experiments in sealed, evacuated glass empoules.

One finding was that “The addition of the acid catcher to an ester lubricant significantly improves the hydrolytic stability by removing acids as they are formed.”

The approached noted by Mitsubishi was with the development of a “catcher capable of capturing the sludge dissolved in oil, which is difficult to remove by filtering.”

The experimental apparatus “has a mixing tube, in which the oil and the liquid refrigerant are mixed continuously. It also has a mix-promoting tube in which the flow velocity is increased, and a sludge catcher in which the deposited sludge is captured while moving downstream.”

One finding was that “The capture rate increased almost linearly as the concentration of sludge increased.”

A reliable oil return when using HFC-410A and alkylbenzene oil was the goal of the University of Maryland. Part of the lab setup called for “two oil loops to be installed parallel to the refrigeration cycle. The first oil loop returns directly to the compressor. Oil leaving the compressor in the discharge line is separated by two oil separators connected in series, and then returns to the suction line.

“The second oil loop consists of a syringe pump, suction line oil separators, and an oil storage tank. It provides oil in the test section for the return oil test.”

With this technology, “The refrigerant provides enough sheer force to transport the oil upward.”

Hopefully these modifications will reduce the amount of service these products require — and reduce the number of aspirins technians need to swallow when dealing with them.

Sidebar: NATE updating cd-rom reference guide

The North American Technician Excellence, Inc. (NATE) is looking to release the second edition of its CD HVACR Textbook Reference on CD-Rom for early winter.

The new CD-ROM will work as a searchable database and will cross-reference NATE ACE test topics to specific industry textbooks and reference manuals.

Before the software is released, NATE is soliciting changes or updates to the previous edition. Publishers, manufacturers, and associations in the industry with training materials are being asked to contribute to the CD-ROM. Organizations who participated in the first version are being asked to either add new material or update any old material to keep the next edition current.

NATE will send a recordable CD to anyone interested. The changes can then be made on the CD and sent back to NATE. There is no charge and everyone is welcome to participate, but NATE asks that individuals act fast in order to get the CD out by winter.

For more information, call Joel Kinsch, NATE’s Director of Technology, at 918-443-2660, or send e-mail to yjk@ionet.net.

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