Evaluating coefficient of performance and rate of moisture loss of some biomass humidifiers materials with a developed simple direct stand-alone evaporative cooling system for farmers

•A low cost stand-alone low energy evaporative cooler (EVC) was developed for preservation /cooling of fruits.•Palm fruit mesocarp fibre and Jute fibre biomass showed good humidifying ability for the EVC.•Moisture loss rate was lowest in Jute fiber and palm fruit mesocarp fibre biomass humidifier.•Maximum COP of up to 78 and humidifying efficiency of 78.62% was achieved. The purpose of this study was to investigate the feasibility of deploying a direct evaporative cooler with Jute fibre, palm fruit mesocarp fibre and wooden charcoal as a humidifier in Nigeria. The high cost of imported evaporative coolers and humidifiers can discourage farmers and limit the adoption of evaporative cooling technology. For this purpose, an experimental direct evaporative cooling test rig was developed and assembled in southwestern Nigeria with a biomass humidifier. The evaluation parameters were the humidifying efficiency, the rate of moisture loss, coefficient of performance and sensible heat ratio. The humidifier presented average cooling efficiency of 55.9 to 78.62%, an average rate of moisture loss of 1.37 × 10 −3 to 2.61 × 10 −3 kg/s, an average COP of 8.48 to 23.42 (EER of 11 to 78) and an average sensible heat ratio of 1.28 × 10 −4 to 4.06 × 10 −4 for the air velocity of 3.0 to 4.5 m/s. The obtained performance can be better in a dryer month or nearly impossible in a very wet month as the humidifying efficiency of direct evaporative coolers is found to diminish at high humidity. To avoid casting doubt on the effectiveness of direct evaporative coolers by farmers, they should only serve as stop-gap preservation equipment and be deployed during favourable weather conditions especially during the winter when the air is dry. These can be identified from the metrological charts of the chosen location.