Performance analysis of a low approach low temperature direct cooling tower for high-temperature building cooling systems

Abstract

For certain temperate climate types, cooling towers have the potential to produce high temperature chilled water, which when used in conjunction with radiant and displacement cooling technologies, have prompted interest in this concept as a potential approach for the conditioning of buildings. The feasibility of the proposed system depends largely, on achieving low approach water temperatures within an appropriately designed cooling tower, at acceptable levels of energy performance. Using a validated mathematical model, the current paper examines the performance of such a cooling tower for four different temperate climate conditions. The current assessment shows for building water return temperature of 22°C, for temperate climates that are considered warm and humid, the limitations on cooling tower operation are when ambient conditions exceed 25°C and 75% RH. Two strategies were investigated to allow the smallest practicable approach to the wet bulb temperature to be achieved: (i) increasing the tower air flowrate, (ii) decreasing the tower water flowrate. For a temperate climate that is warm and humid, operating the cooling tower with an approach of 1.0K was found to be not practicable for all encountered weather conditions, but use of a 2.0K approach was found to be practicable for all conditions.