General Comments and Comparisons of Air Cycle Systems with Vapor Cycle Systems

1. Closed vapor cycle refrigeration systems possess much higher coefficients of performance than open or closed air cycle systems
2. Air cycle systems tend to be lighter in weight.
3. High ratios of fresh air-to-recirculation air dictate air cycle cooling, whereas vapor cycle systems are generally best for low fresh air-to-recirculation air ratios.
4. Vapor cycles permit centralized refrigeration systems with intermediate transport media to various compartments or pieces of equipment being cooled.
5. Vapor cycles are recommended where full recirculation (no fresh air supply) is required and water or ram air heat sinks are available.
6. Vapor cycles possess large capacity ground cooling and pulldown capabilities.
7. Air cycle systems possess the fundamental advantage of direct supply of air for both cooling requirements and pressurization control.
8. Air cycle units are characterized by high specific output from compact units.
9. When requirements dictate a high fresh air supply quantity, an open circuit basic  bootstrap system provides the most latitude both functionally and in cooling capacity over a wide speed range.