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Compact, lightweight unitary-type air conditioner using transcritical R744 designed for energy efficient operation in hot climates.

Author(s) : ELBEL S., MANZIONE J. A., COLLIER S. J., et al.

Summary

Transcritical R744 technology was used to design a compact, lightweight unitary-type air conditioner for military shelter cooling. In the past, US Army has funded a series of research projects aimed at converting existing environmental control units (ECUs) that use H/C/FC refrigerants to transcritical R744. However, for the nominal cooling capacity of 35 kW no baseline system that uses a conventional refrigerant exists. Therefore, this trailer-mounted R744 ECU air conditioner had to be designed and built from ground up. This made it possible to focus the design considerations on achieving high energy efficiencies during operation in hot ambient temperatures. High performance prototype components were used to realize the target performance of 35 kW at the high ambient temperature rating condition (outdoor: 51.7°C, indoor: 32.2°C-50% RH). Valuable insights were derived from comparing the performance of this new R744 air-conditioning system to experimental results that are available for comparable ECUs of lower capacity. It was found that the COP of this new R744 ECU is approximately 30% higher than that of a comparable R134a ECU and approximately 20% higher than that of a comparable R410A ECU (based on manufacturer data). ECU compactness was determined by calculating cooling output per ECU weight and volume. The new 35 kW R744 ECU was found to be 60% (cooling per weight ratio) and 40% (cooling per volume ratio) more compact than comparable R134a technology. The compactness levels of R744 and R410A technology were found to be approximately equal.

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Pages: 2010-2

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Details

  • Original title: Compact, lightweight unitary-type air conditioner using transcritical R744 designed for energy efficient operation in hot climates.
  • Record ID : 2010-0906
  • Languages: English
  • Source: 9th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2010). Proceedings. Sydney, Australia, April 12-14, 2010.
  • Publication date: 2010/04/12

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