A Novel Air Conditioning System: Membrane Air Drying and Evaporative Cooling

Abstract

Anovel system for air conditioning is proposed which combines membrane air-drying and an indirect/direct evaporative cooling (M/ID) system. This combination extends the operating range of the evaporative cooler for small differences of dry and wet bulb temperatures. The study investigates the feasibility of operating the proposed system for the cooling of ambient air to an outlet temperature of 19°C and a relative humidity of 90%. The analysis is performed for the summer weather data of Kuwait, which varies from extremely hot and dry conditions (50°C and less than 20% relative humidity) to warm and humid conditions (35°C and more than 60% relative humidity). System analysis shows limitations imposed on air cooling by the direct evaporative cooler (DEC), the indirect evaporative cooler (IEC), and the indirect/direct evaporative cooler (ID). For ambient temperatures above 35°C, operation of the ID system requires relative humidity values below 30%. Operation of the DEC or the IEC systems is limited to temperatures below 30°C and relative humidity below 50%. The ID system operates at temperatures above 45°C and relative humidity below 50%. The M/ID operation covers a relative humidity range between 30–100% and a temperature range between 25–45°C. Energy consumption for various cooling combinations, including mechanical vapour compression (MVC), is evaluated by the energy efficiency rating (EER). The M/ID system shows savings of up to 86.2% of the energy consumed by the stand-alone MVC system. Also, the combined systems of MVC/IEC and the MVC/ID show savings of 49.8 and 58.9% over the conventional MVC.