Evaluation of Cooling Load of a Building Envelope in Owerri, Nigeria to Support the Optimized Design of a Suitable Sub-Wet-Bulb Evaporative Cooling System

Abstract

The work focuses on designing a comfort-cooling evaporative system for a pilot building in Owerri, using data derived from the building’s thermal conditions. The initial step involved estimating the building cooling load by identifying key design parameters, namely ambient climatic data for the location and the target indoor comfort parameters that the proposed system must deliver. In this case, the primary inlet air (dry-bulb) was assumed to be 36 °C with 40-60% relative humidity, reflecting the local climate, while the target indoor conditions were set to a dry-bulb of 24.5-27 °C and 50-60% RH, appropriate for tropical air-conditioning. For the office space located at latitude 5°29′ N, longitude 7°0′ E, the cooling load was calculated to be 1 kW (with a 10% safety factor), equivalent to approximately 0.3 tons of refrigeration. Using this load, the system components were sized from first principles and design guidelines, arriving at a heat-exchanger area of 0.7 m², fan and pump power in the range of 300-370 W, working air ratio of 0.3, a 10-litre water reservoir and locally sourced poorly weaved fibrous fabric. The deployment of these design parameters enabled the production of an innovative, energy-efficient, eco-friendly sub-wet-bulb evaporative cooling solution for buildings in Owerri, Nigeria.