Nasiru I. Ibrahim

Performance enhancement of a vapor compression system by condensate

Air-conditioning systems consume large amount of energy and generate considerable amount of condensate when operated in hot and humid climates. This study considers utilizing the generated condensate to pre-cool the air entering evaporators to improve systems performance. Experimental and analytical investigations are carried out by using an air-conditioning system of 4.75 kW (16207 BTU/h) cooling capacity incorporated with an air pre-cooler and a condensate tank that acts as a thermal storage. During the pre-cooling-on period, the air inlet temperature of the evaporator is decreased by 5.7°C (10.3°F) and the compressor power consumption is reduced by 5.1% because of the decrease in discharge pressure. The coefficient of performance increases by 30.7% and second-law efficiency by 24.2%. The air pre-cooling is practical for 4–5 hours daily during the daytime if a 450–1000 kg of condensate cold thermal storage is employed. The deviation is 6.7% between the analytical and experimental results.

Recent Developments in Liquid Desiccant-Based Cooling Systems

The conventional vapor compression air conditioning systems remove moisture from the air by cooling to a very low temperature. This dehumidified air is then reheated to an appropriate supply temperature for occupants comfort. These two processes of excessive cooling and reheating of process air remarkably increase the air conditioning load. To avoid the excessive waste of energy an alternative way to achieve desired moisture reduction is the use of liquid desiccant dehumidification system in which a desiccant material absorbs moisture from the humid air. Thermal energy is used to regenerate the desiccant material and cycle continues. A good desiccant should have better moisture absorption capability and lower temperature of regeneration. Different types of new desiccant materials with high dehumidification performance have been proposed in past few years. These materials have the potential to improve the performance of liquid desiccant cooling systems because of lower heat input required for regeneration. In this article, liquid desiccant cooling systems have been discussed from variety of aspects including the need of liquid desiccant technology as an alternative way of cooling, working of liquid desiccant cycle, as well as developments of this technology. The research indicated that the technology of liquid desiccant cooling has a great potential of energy saving and providing human thermal comfort conditions in hot and humid climatic conditions with the utilization of alternative energy resources.