Using Liquid To Cool Grocery Cases Saves Energy, Helps Environment

April 08, 1998

CHAMPAIGN, Ill. -- Refrigerants leaking from systems that chill supermarket display cases are a leading source of environmental pollution. Recent tests by a team of University of Illinois researchers indicate that an alternate method of refrigeration can reduce leakage and save money.

"There are approximately 30,000 large supermarkets in the United States, and the typical supermarket leaks about 1,500 pounds of refrigerants annually," said Predrag Hrnjak, a professor of mechanical and industrial engineering and a researcher at the university's air conditioning and refrigeration center. "This is a huge problem. In fact, supermarkets are second only to automotive air-conditioning systems in polluting the atmosphere with refrigerants."

One potential solution is to replace the high-pressure gas used in conventional refrigeration systems with a low-pressure liquid, Hrnjak said. "Circulating a liquid refrigerant ­ a technique called secondary cooling ­ can increase energy efficiency, reduce refrigerant leakage, and utilize a centralized refrigeration unit that is more reliable and less expensive to operate."

While thousands of European supermarkets have switched to the secondary cooling technology, the idea has been slow to catch on in other parts of the world. In the United States, for example, about 100 supermarkets have been converted.

One reason for the slow acceptance, Hrnjak said, is that "few tests have been performed to determine which system is actually more efficient. Nor do we know which fluid is the best one to use."

To answer such questions, Hrnjak, research engineer Yanhui Mao and graduate research assistant Wilson Terrell Jr., compared the performance of a typical supermarket display case operating with a conventional refrigerant (R404A) and with two different secondary coolants (potassium formate and potassium acetate). The researchers placed a display case, filled with simulated food packages, in an environmental chamber and monitored package temperatures as a function of refrigerant temperature.

"We found that the display case performed better with potassium formate as a secondary coolant than with the conventional refrigerant," Hrnjak said. "Our tests showed that the same product temperature could be achieved with a higher operating temperature of secondary coolant.

"For example, to maintain frozen foods at the proper temperature, the R404A refrigerant must have an inlet temperature of -32.5 degrees Centigrade," Hrnjak said. "The same product temperature, however, could be achieved with potassium formate at an inlet temperature of only -26.5 degrees Centigrade. This is a significant difference in temperature and the amount of refrigeration required."

The preliminary results "indicate that secondary cooling is a cost-effective and energy-efficient alternative to conventional refrigeration. And it's better for the environment," Hrnjak said.

The researchers presented their findings at the International Institute for Refrigeration conference, held in Cambridge, England, March 29-April 1.
-end-


University of Illinois at Urbana-Champaign

Related Temperature Articles from Brightsurf:

History of temperature changes in the Universe revealed
How hot is the Universe today? How hot was it before?

A drop in temperature
In the nearly two centuries since German physician Carl Wunderlich established 98.6°F as the standard ''normal'' body temperature, it has been used by parents and doctors alike as the measure by which fevers -- and often the severity of illness -- have been assessed.

Kitchen temperature supercurrents from stacked 2D materials
A 'stack' of 2D materials could allow for supercurrents at ground-breakingly warm temperatures, easily achievable in the household kitchen.

Get diamonds, take temperature
Measuring the temperature of objects at a nanometer-scale has been a long challenge, especially in living biological samples, because of the lack of precise and reliable nanothermometers.

Chemical thermometers take temperature to the nanometric scale
Scientists from the Coordination Chemistry Laboratory and Laboratory for Analysis and Architecture of Systems, both of the CNRS, recently developed molecular films that can measure the operating temperature of electronic components on a nanometric scale.

How reliable are the reconstructions and models for past temperature changes?
Understanding of climate changes during the past millennia is crucial for the scientific attribution of the current warming and the accurate prediction of the future climate change.

New method measures temperature within 3D objects
University of Wisconsin-Madison engineers have made it possible to remotely determine the temperature beneath the surface of certain materials using a new technique they call depth thermography.

Who takes the temperature in our cells?
The conditions in the environment are subject to large fluctuations.

Taking the temperature of dark matter
Warm, cold, just right? Physicists at UC Davis are using gravitational lensing to take the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.

Thermal siphon effect: heat flows from low temperature to high temperature
In this work, researchers study (both thermal and electric) energy transport in physical networks that rewired from 2D regular lattices.

Read More: Temperature News and Temperature Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.