Full Description

The absorption cycle is one of the alternatives for use with solar and other sources of thermal input such as geothermal and waste heat. The double-effect absorption cycle, because of its enhanced COP, is a competitor to proposed Rankine cycle solar cooling systems. While the Rankine cycle has the advantage of mechanical output, the double-effect absorption cycle appears to have a better COP when operating purely in the cooling mode. The double-effect cycle has been available for several years. However, there has not been a significant interest in it for application in solar cooling systems, and it is surprising that there has not been more application of it in recent years in conventional steam-fired cooling systems. Auh provides an excellent overview of absorption cooling.'

A preliminary assessment of the potential of double-effect water-lithium bromide absorption cooling systems is presented by Vliet and Saiidi. The first prototype double-effect unit was developed by3Ythwest Research Institute in 1956-58 under funding from the American Gas Association. Later, the Iron Fireman Company of Cleveland, OH, purchased the manufacturing rights and began production of the "Iron Fireman" unit in 1963, a nominal 15-ton, gas-fired unit with a gross COP of 0.9 to 1.0 and a net COP of 1.2 to 1.3 near its design capacity. Only a few units were manufactured and sold, and it is no longer in production. In 1973 a U S. fir introduced a line of steamfired double-effect absorption units, which are still marketed. They have a capacity range of 385 to 1060 tons and a COP range of 0.9 to 1.0 near design capacity. One Japanese firm has announced the introduction of a 20-ton gas-fired unit. Although double-effect units have been and still are available, they do not appear to have captured their share of the market, possibly because they were designed during the availability of cheap energy and are not as efficient as they potentially might be.

The major objectives of this project were to develop a comprehensive computer code to dynamically simulate the water-lithium bromide double-effect absorption cooling cycle and to use the code to investigate the influence of the several design and operational variables on the cycle performance (coefficient of performance and capacity). Ultimately, it is hoped these results and/or the computer model would be used by manufacturers for improving the design of future systems.

Citation: Symposium, ASHRAE Transactions, Volume 88, Part 1, Houston, TX