Refrigerant-adsorbent pairs

Critoph, R.E., Evaluation of alternative refrigerant - adsorbent pairs for refrigeration cycles. Applied Thermal Engineering, 1996,16(11), 891 900. 

The applieation of aetivated earbons in adsorption heat pumps and refrigerators is diseussed in Chapter 10. Sueh arrangements offer the potential for inereased efficiency because they utilize a primary fuel source for heat, rather than use electrieity, which must first be generated and transmitted to a device to provide mechanical energy. The basic adsorption cycle is analyzed and reviewed, and the ehoiee of refrigerant-adsorbent pairs discussed. Potential improvements in eost effeetiveness are detailed, including the use of improved adsorbent carbons, advanced cycles, and improved heat transfer in the granular adsorbent earbon beds. 

In order to understand the operation of the cycle and the ideas put foi"ward later it is useful to look at the essential properties of adsorbent-adsorbate pairs and the way that they are used in the solar refrigerator. 

The best sub-atmospheric refrigerant is water. Unfortunately it is not strongly adsorbed by carbons, but refrigerators and heat pumps based on water - zeolite pairs have been built and tested in research laboratories. Methanol is adsorbed well by carbons and a solar refrigerator based on a carbon - methanol pair was marketed by Brissoneau et Lotz Marine in France. Methanol is environmentally friendly, but deeomposes at temperatures around 150°C and so camiot be used for very high temperature cycles. 

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