Share

Carnot-equivalent air cycle heat pump leveraging isentropic and isothermal compression and expansion principles – a theoretical analysis.

Number: 2157

Author(s) : BACELLAR D., TSITAKA S., RADERMACHER R.

Summary

Air cycle heat pumps (ACHP) have great potential for tackling HVAC&R contributions to climate change, social-economic gaps worldwide and ventilation concerns enhanced by the COVID-19 Pandemic. Air has no global warming potential (GWP), it is available everywhere, and could result in less complex - and possibly lower cost - systems. Conventional air cycles near ambient temperatures, however, have lower COP compared to conventional vapor compression cycles (VCC) using higher GWP refrigerants, since they operate too far from the saturation region (large “superheat horns”). Despite the progress shown in the literature, all of the proposed ACHP configurations are still limited by the compression and expansion processes which are at best done isentropically. A better alternative is the isothermal compression/expansion which can be achieved by coupling the work and heat exchange processes together. Isothermal compression/expansion of air is often used for energy storage and power generation. An overlooked opportunity is using such concepts in heat pumps. In this paper, we present a theoretical analysis on a proposed Carnot-Equivalent Air Cycle (CAC) as a heat pump leveraging both isentropic and isothermal compression/expansion principles. The key lessons are: isothermal compression/expansion eliminate the temperature “horns”; and it is a function of its ability to transfer heat, i.e., the component’s UA; CAC temperature lift is decoupled from the pressure lift; CAC COP is very sensitive to the isothermal efficiency and in the ideal case is approximately 5 times greater than the reversed Brayton Cycle; the isothermal compression/expansion need to be at least 90% in order for the system to become truly competitive against conventional VCC; the volumetric flow rates for the same capacity are an order of magnitude larger for CAC compared to VCC, which will result in larger compressors/expanders.

Available documents

Format PDF

Pages: 10 p.

Available

Free

Download

Details

  • Original title: Carnot-equivalent air cycle heat pump leveraging isentropic and isothermal compression and expansion principles – a theoretical analysis.
  • Record ID : 30030498
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022/07/10

Links


See other articles from the proceedings (224)
See the conference proceedings

Indexing