The development of more competitive absorption refrigeration systems could reduce primary energy use and energy costs and allow use of natural gas for cooling. Absorption cycle efficiency approaches theoretical cycle limits, but the fluids used limit the range of operating temperatures and pressures. Problems with conventional lithium bromide (LiBr)-water and water-ammonia systems also include corrosivity and toxicity, crystallization, and fluid volatility. Mixtures of glycols and polymers as the adsorbent, with either water or methanol as the refrigerant, will be tested as absorption cycle fluids. Used alone, the low water capacities of pure glycols at low water pressures result in unacceptably low absorption cycle coefficients of performance (COPs). However, it has been shown that adding certain polymers to glycols results in a threefold capacity improvement at low water vapor pressures. Glycol-polymerwater systems have the potential for cooling COPs similar to LiBr-water and for operating over a wider range of conditions without crystallization. They are also non-corrosive. Glycol-polymermethanol systems could be used for both heat pump and cooling applications, would have lower distillation energy requirements and higher COPS, and would be less toxic than water-ammonia. Thermodynamic relationships of the glycolpolymer system with water and methanol refrigerants will be determined during Phase I using a Sartorius microbalance. The data will be used to design improved absorption cycles.Anticipated Results/Potentiat Commercial Applications as described by the awardee:Phase II will develop detailed thermodynamic data on the most promising system, and use this data to design, construct, and operate a subscale single-stage cycle. This prototype will provide a proof of concept and technical data on heat and mass transfer in the adsorber. Incorporation of improved absorption fluids into advanced cycles could result in thermally driven heating and cooling systems that are competitive with vapor compression systems and that reduce energy use and costs. The absorption fluids also could be used to replace those in current liquid based air dehydration systems.
