Investigation of Ethanol/metal organic frameworks for low temperature adsorption cooling applications

Adsorption cooling is a promising technology that can effectively utilize waste heat from many industrial processes for refrigeration and air conditioning. Commercially available adsorption systems are based on silica gel/water, zeolites/water and activated carbon/ammonia pairs. These suffer from various limitations including: achieving cooling below zero for refrigeration applications and the use of highly poisonous refrigerant like the ammonia. Metal Organic Framework materials (MOFs) are new micro-porous materials with exceptionally high porosity and large surface area that can be used as adsorbents. Ethanol is a natural non-toxic refrigerant with low environmental impact that can operate at temperatures below zero. This paper experimentally investigates the Ethanol adsorption characteristics of six MOF materials compared to that of silica gel as a conventional adsorbent material that is widely used in commercial adsorption systems. Results revealed that MIL-101Cr have shown superior performance with uptake value of 1.2kg_ref/kg_ads. Also, MIL-101Cr proves to be stable through 20 successive cycles at 25°C. Results from theoretical modeling of a two bed adsorption system with heat and mass recovery have shown that using MIL-101Cr/Ethanol pair can achieve evaporator temperature close to -15°C and propylene glycol outlet temperature of -7°C. These results highlight the potential of MOF/Ethanol in low temperature cooling applications, in particular MIL-101Cr MOF.