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A centrally heated, externally cooled air-coupled adsorption system for waste heat recovery.

Number: pap. n. 123

Author(s) : ROBBINS T. R., GARIMELLA S.

Summary

A novel adsorbent bed is described, modeled, and tested at a lab scale. The adsorbent bed is of a centrally heated, externally cooled (CHEC) design. This bed concept eliminates the need for cooling liquid lines and controls to the adsorbent bed, reducing system complexity and allowing adsorption systems to be used over a large range of thermal inputs. The reduction in complexity is achieved by using the external surface of the bed to directly transfer heat to the surrounding air. The heat transfer rate is improved through cooling fins and a novel bed geometry that increases the area available for cooling. Heat is transferred into the bed using a heat transfer fluid flowing through channels with adsorbent material packed around the channels. The heat transfer into the system is faster than heat removal, due to differences in convection coefficient. Such a system is ideal for small-scale waste heat utilization where a chiller tower or dedicated radiator for adsorbent cooling is cost or space prohibitive. It is of particular interest for use with automotive air-conditioning applications with heat from the engine driving the system and air flow over the beds effectively cooling the bed. Activated-carbon/ammonia working pair is chosen for evaluation of the concept. System performance is modeled for a range of waste heat temperature sources. Coefficients of performance (COP) of 0.01-0.1 and Specific Cooling Capacities (SCC) of 4-80 W kg-1 are predicted for small-scale systems delivering 100 watts of cooling or less. Performance is expected to improve dramatically at larger system scales. A small-scale prototype is used to test the concept for a single adsorbent bed system using the CHEC bed design. The experimental results confirm conclusions from system modeling. The CHEC concept trades system efficiency for reduced system complexity. It should also improve system reliability and reduce system cost by eliminating valves and pumps required for the cooling system.

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Pages: 11 p.

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Details

  • Original title: A centrally heated, externally cooled air-coupled adsorption system for waste heat recovery.
  • Record ID : 30013674
  • Languages: English
  • Source: International sorption heat pump conference (ISHPC2014), College Park, United States, March 31-April 2, 2014.
  • Publication date: 2014/03/02

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