Modeling and Simulation of Condensation on Plastic Condenser Cooling under Night Sky

Abstract

The Kutch region of north-west India is hot and semiarid, chronically short of drinking water. Dew forms frequently in the areas near the coast, over a span of eight-month (October- May) coinciding with the entire dry part of the year. Dew water is potable and safe. Dew harvest systems - devices to condense and collect dew - have been developed which could be installed on building roofs (condenser-on-roof), open ground (condenser-on-ground) and on frames (condenser-on-frames). The key component is the condenser, made of thin plastic film insulated underneath, which cools at night by radiative exchange with cloud-free sky. Condensation occurs when the film cools to or below the dew point of the surrounding air and humidity level is high - upwards of 85%. Over the season of eight months, 15 – 20 mm of dew water can be harvested. In this region where rainfall is very erratic and in normal years only 300 mm, harvested dew water can be an appreciable supplement. It can also be a small but critical supply for plants in nurseries. Design principle of efficient dew condenser is discussed and dew water collection in some recently installed working systems reported.