Environmentally Friendly Refrigeration System Developed For NASA Has Commercial Applications

A new, environmentally friendly refrigeration system, developed for NASA to use aboard its Space Shuttles and International Space Station, is finding applications here on earth.

Working for NASA’s Marshall Space Flight Center in Huntsville, Ala., William G. Dean of Dean Applied Technology, Inc., has invented a pulse-tube refrigeration unit that offers a viable alternative to units that use ozone-destroying chlorofluorocarbon (CFC) and hydrochloroflurocarbon (HCFC) refrigerant fluids. The pulse-tube refrigerators use helium, non-toxic to humans and harmless to the environment, as the working fluid.

Pulse-tube refrigerators can operate over a wide range of temperatures. The technology can be used in food refrigerators/freezers, laboratory freezers, and freeze dryers. Pulse-tube refrigerators also can be used to cool electronic devices and detectors. It is the first unit applied to the temperature range and load level needed for typical food and laboratory freezers.

The pulse-tube refrigerator unit’s design is based on the orifice pulse-tube concept. In this, the gas is compressed in the compressor, then it flows through the compressor after-cooler where the heat is rejected to a water-cooling loop. Then the helium flows through the regenerator, which is essentially an economizer, conserving cooling from one cycle to the next. The gas then enters the cold-end heat exchanger where heat is added to the gas from the surroundings. In the final stage, the gas enters the pulse tube, orifice and reservoir which, together, produce the phase shift of the mass flow and pressure necessary for cooling. The gas moves repeatedly between the hot and cold ends rather than circulating continuously around a loop as is found in some other types of refrigeration systems. Heat is lifted and rejected at the hot-end heat exchanger, which is also water-cooled.

The new unit’s compressor uses dual-opposed pistons displaced 180 degrees out of phase to minimize vibration. This is of great importance to NASA as vibrations can affect sensitive experiments being performed aboard the Space Shuttle and the International Space Station.

Pulse-tube refrigerators offer commercial users increased reliability, fewer moving parts, and much lower cold-end vibration than designs previously used on spacecraft or commercially. For more information on pulse-tube refrigerator units, contact Dean Applied Technology, Inc. at 1580 Sparkman Dr., Suite 103, Huntsville, AL 35816 or phone (256) 721-9550.