A centrally heated, air-coupled adsorption cooling system driven by waste heat

Abstract

• Centrally heated, externally cooled adsorbent bed design presented. • Small-scale adsorption chiller with cooling duty < 100 W demonstrated. • COP of up to 0.1 and SCC of 4-80 W kg -1 predicted and experimentally demonstrated. A novel centrally heated, externally cooled (CHEC) adsorbent bed is conceptualized, modeled, and tested at a lab scale. It eliminates the need for cooling liquid lines and controls to the adsorbent bed, reducing system complexity and allowing the system 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. Such a system is ideal for small-scale waste heat utilization where a chiller tower cost or space prohibitive. The activated-carbon/ammonia working pair is chosen and system performance modeled over a range of waste heat temperatures. Coefficients of performance (COP) of up to 0.1 and Specific Cooling Capacities (SCC) of 4-80 W kg -1 are predicted and demonstrated experimentally for small-scale systems delivering 100 watts of cooling or less. Performance is expected to improve dramatically at larger system scales due to the larger bed-to-auxiliary thermal mass ratios. This 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.