Although the screw compressor offers advantages for refrigeration applications, it also presented an obstacle that Delta Heat Transfer Inc., Flowery Branch, GA, wanted to overcome.

A unique situation with screw compressors, noted Tim Henderson, market development manager, Parker Hannifin Corp., Atlanta, GA is that “they move a lot of oil and this oil gets hot. So you have to keep it cool.”

However, it’s hard to keep this volume of oil cool. Screw compressors generally use “big air-cooled oil coolers, and you have to run lots of copper lines, and you have to exhaust the hot air somewhere,” said Henderson.

“Even though screws have a lot of benefits, that was the biggest drawback.”

Delta, a subsidiary of Bitzer, designs and builds refrigeration systems using the Bitzer screw compressor. What Delta did, Henderson explained, is come up with a “thermosiphon system.”

The company takes liquid refrigerant from the condenser and runs it through a heat exchanger to cool the oil. Then the liquid refrigerant is sent back to the condenser, “basically using the condenser as an oil cooler,” stated Henderson.

Better feed needed

However, “the problem was feeding that liquid at a controlled rate through the heat exchanger,” he continued.

Delta originally used a motorized ball valve. “It wasn’t terribly reliable and it didn’t control very well,” he said. “It was slow to move and react.”

What Delta and Parker did is adapt Parker’s Ana-Loid™ valve technology, and came up with an electronic feed control.

The Ana-Loid is a linear-proportional solenoid control valve that incorporates a magnetic circuit which provides a force that is proportional to the level of dc current, over a finite stroke. It uses a frictionless plunger combined with a pressure-balanced valve mechanism, says the company.

Parker had been working to try to adapt the Ana-Loid to its line of regulators, and when Henderson mentioned this in conversation with Dave Laird, president of Delta, Laird told Henderson that he could apply it. Laird got some test pieces and worked on it, and came up with a solution to his control problem, which Delta calls the Jet Kool® system.

Under control

In adapting the Ana-Loid valve for his application, Laird noted, “We have to have a valve that gives us fairly good control with a very small pressure drop, which this valve does.

“The motorized ball valve, because of the cycling, just couldn’t handle the application. It would leak after about six or eight months.”

With the Jet Kool system, said Laird, “We’re controlling the amount of refrigerant flow into the heat exchanger based upon the discharge temperature of the rack system. We did a lot of R&D with Parker to get our sizing right and basically work out the bugs in the system.”

He added, “We’re probably one of the first companies to utilize” the Ana-Loid valve.

The patented Jet Kool system can be mounted on the rack. “It doesn’t need any special field installation,” Laird said.

The Jet Kool has been out in the field about three years. The first year the Ana-Loid wasn’t available. Once Delta switched over to the Ana-Loid, they started with three installations initially, two Winn-Dixies and an A&P supermarket.

Laird related that approximately 80% to 85% of Delta’s installations have been in supermarkets. The company currently has a total of 125 to 130 supermarket installations.

Because the new system with the Ana-Loid valve worked so well, said Laird, to avoid any problems, “We went back and retrofitted every ball valve we had out there.”

User response

Supermarket users agree that the Jet Kool is working well for them. Fred Prekel, corporate engineer for A&P, Patterson, NJ, started out using a couple Jet Kools on an experimental basis about two years ago. He’s now using it in a dozen stores. He has two dozen units installed on low- and medium-temperature racks.

The advantages of the Jet Kool design, Prekel said, are, “One, it limits the amount of oil; two, it’s more consistent with the oil temperature; three, it’s less bother and more compact.”

There were some “teething problems” at first, said Prekel, but those problems have been addressed and, “It looks very good right now.”

Prekel also pointed out the problems he’s not having with the Jet Kool as opposed to his previous oil coolers. “I’m not having leaky oil coolers. I’m not having noisy fans on the oil coolers. I don’t have all that additional line going to an oil cooler on the roof. I don’t have the additional 10 gallons of oil required to fill up the oil cooler and the line.”

Terry Wetzel, maintenance construction manager for Winn-Dixie’s Atlanta Division, remarked that about three years ago his firm was using the rooftop oil cooler system, “which was detrimental, as far as I was concerned, not only from a maintenance point of view, but also as far as the roof warranty,” if an oil leak should develop and possibly void the warranty.

He did a prototype test store with Delta to try out the new Jet Kool system. “It worked out better than we expected,” said Wetzel.

“We then started buying all of our new racks with the Jet Kool system installed. And we went back to a couple stores and retrofitted.”

He’s using the system in eight to 10 stores now, and has had “no problems whatsoever.”

Tony Coppola, facility maintenance manager for Big Y, Springfield, MA, said that about two years ago, he retrofitted a store. He has since retrofitted the low-temperature racks in 10 stores.

The Jet Kool, he remarked, “runs fine. It’s simple. It eliminated the need for those big oil coolers.”

He continued, “It’s headache-free. We never had an issue with them.” It was an “easy changeover.”

Coppola had some oil coolers that were developing leaks. Eliminating the oil coolers and putting in the Jet Kool, he said, eliminated the oil leaks.

“The operation of it is simple. There’s just a couple controls on it and that’s it.”

For more information on the Ana-Loid valve, contact the company at 216-896-3000; 216-896-4008 (fax). For more information on the Jet Kool system, contact the company at 770-967-0030; 770-967-0032 (fax).