Heat Rejection Systems

This technical appraisal outlines the results of research into the costs involved in operating wet and dry heat rejection systems.

The research was prompted by concerns over design/replacement decisions which are being forced by worries about legionnaires' disease.

This work is concerned with indicating the more common methods employed for the rejection of heat from refrigeration systems used in air conditioning, and to illustrate aspects of the operating costs associated with some of these systems.

The results are based on a sponsored research project.

The objective of the research project entitled "Cooling System Operating Costs" was to provide information for selection/replacement decisions regarding cooling towers and dry coolers/air-cooled condensers based on a limited number of case studies.

It must be borne in mind that with the limited number of case studies (three wet and three dry systems), the results whilst in themselves are robust, may not translate to all other potential applications. The first major UK outbreak of legionnaires' disease associated with an air conditioning system was at Stafford District General Hospital in April 1985 where the cooling towers were to blame.

Some seven years on this is believed to be the first time actual operating costs of the two alternate methods of heat rejection have been published.

During this time water treatment methods have changed considerably, urged on by safety legislation.

Advances in refrigeration system design and components have produced energy efficiencey improvements.

The project results indicate there is still room for improvement in terms of reducing energy costs through improved plant control and utilization.

Reduction in water treatment costs may also be possible.