Effect of Air Velocity on the Performance of a Four-Coil Evaporator Atmospheric Water Harvester

Abstract

The increasing demand for clean water has driven the development of various technologies, including seawater reverse osmosis (SWRO), rainwater harvesting, and atmospheric water harvesting systems. Among these, atmospheric water harvesters operate using a vapor-compression refrigeration cycle to condense water vapor from ambient air. This study investigates the effect of air velocity on water production and heat transfer performance in a four-coil evaporator atmospheric water harvester. An experimental approach was employed using R134a as the working fluid and a 1 PK rotary compressor. The system was equipped with four coil-type evaporators, each with a tube diameter of 6.35 mm, 26 turns, and a coil diameter of 80 mm. Air velocity was varied at 4 m/s, 5 m/s, and 6 m/s. The results show that the highest water yield of 0.733 kg was obtained at an air velocity of 6 m/s over 7 hours of operation. The maximum heat transfer rate from air to the evaporator reached 290.778 J/s at an air velocity of 5 m/s. Meanwhile, the highest coefficient of performance (COPrev​) of 9.21 was achieved under no-airflow conditions (0 m/s). These findings indicate that air velocity significantly affects water production, heat transfer, and overall system performance, with optimal conditions depending on the desired performance parameter.

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