Gas is compressed in the compressor. Helium then flows through the regenerator, which is essentially an economizer, conserving cooling from one cycle to the other. Next, the gas enters the cold-end heat exchanger, in which 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 between 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 cooled by water.
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 because vibrations can affect sensitive experiments being performed aboard the Space Shuttle and the International Space Station. For more information, contact Bob Lessels at Marshall Space Flight Center. The nontoxic, environmentally friendly working fluid in this pulse-tube refrigeration system offers more commercial applications than previous designs used in space and on Earth.