An experimental investigation of a jet-pump thermal (ice) storage system powered by low-grade heat

This paper reports an investigation carried out on novel combination of a heat driven refrigeration cycle and a thermal (ice) storage (TIS) system. A hydroscopic polymer was used to suspend liquid-water in a gel in an evaporator/ice store, and a jet-pump was used to induce sublimation freezing of the gel. The gel underwent 2 °C of supercooling before nucleation and ice formation was observed. The COP of the jet-pump under sublimation freezing conditions was between 0.2 and 0.3. Results were compared to evaporative freezing using the same test rig, and it was found that COP was 50% greater. 40% was due to the use of an over-expanded nozzle, but 10% was due to transfer of the heat of sublimation. The COP is low compared to other cycles, but it is simple, has low maintenance costs and can utilise low-grade heat. It has great potential to reduce pollution attributable to building air-conditioning systems, whether used alone or in conjunction with other systems.