Design Assessment of a Locally Fabricable Air-to-Air Plate Heat Exchanger for Indirect-Direct Evaporative Cooling

Abstract

This study examines a locally fabricable air-to-air plate heat exchanger used as the indirect stage of an indirect-direct evaporative cooling (IDEC) system. The work uses the TRNSYS 18.0 system model and the HTRI Xchanger Suite 7.3.2 plate heat-exchanger specification reported for a low-cost solar-assisted evaporative cooling system. The selected core is a 65-plate SS304 air-to-air exchanger with 327 mm plate length, 249 mm plate height, 0.6 mm plate thickness, 4.5 mm nominal gap, 101.6 mm port diameter, 32 hotair channels, 32 cold-air channels, countercurrent flow arrangement and 0.33 m² effective heat-transfer area per plate. The direct evaporative cooling (DEC) outlet temperature varied from 17.90 °C to 30.35 °C over the reported daily period, while the IDEC outlet temperature remained within 19.15-19.32 °C. The mean cooled-air temperature was 24.75 °C for DEC and 19.23 °C for IDEC, with corresponding mean cooling efficiencies of 64.05% and 91.30%. These results show that the plate exchanger can provide useful sensible pre-cooling and a steadier supply-air condition under warm-humid conditions in South-South Nigeria. Leakage, pressure drop, flow distribution and heat-transfer effectiveness still require prototype measurement.