To address the growing environmental and logistical burden posed by continued use of Class I ozone depleting chemicals (ODCs), this co-funded Environmental Security Technology Certification Program (ESTCP) and United States Air Force (USAF) Science and Technology project sought to develop a heating/cooling system using a pulse tube refrigerator with helium (a non-ODC gas) as the refrigerant. Currently, the USAF relies on fluorocarbons, such as R- 22, to act as the refrigerant in the environmental control units (ECUs) used to heat and cool fixed, low-volume enclosures on military installations and mobile enclosures for military deployments. Expanded provisions and expedited implementation of the Montreal Protocol as well as ISO 14000 will compromise the future use of Class I ODCs and the subsequent mission readiness of U.S. military forces if the military continues to rely on conventional heat pumps. In addition to reducing ODC use, project goals included a reduction in the weight of mobile ECUs and an increase in their efficiency. Air Force Air Expeditionary Force (AEF) deployments are accomplished by moving a large quantity of equipment and material to various remote locations. A typical AEF kit that sustains an 1100-man force requires shipment of 4.23 million pounds of material with 91 C141 sorties. Reductions in the size and weight of the mobile ECUs transported during AEF deployments would promote military mobility. Increased efficiency of heating, ventilating and air conditioning (HVAC) equipment can reduce deployment costs through decreases in electrical power requirements and fuel consumption. The pulse tube refrigerator is the simplest mechanical gas-cycle refrigerator suitable for application in a commercial heat pump.
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