POROSITY AND PERMEABILITY ANALYSIS OF RIVER-BED SAND FOR EVAPORATIVE COOLING STRUCTURE
Publication Date : 01/08/2012
This paper reports an analysis of riverbed sand as heat exchange medium for use in evaporative cooling storage system in different climate characteristics. Evaporative cooling operates using water and air as working fluids. It consists in water evaporation, through the removal of water moisture from the skin outer wall surface of the structure by the adjacent dry air (flowing or stationary), thus decreasing the air temperature that is in immediate contact with the structure. It was found that sand with larger grading (size) discharges less amount of water and that the granulated limestone has the largest grading of between 0.3 mm and 5.0 mm and discharges less amount of water. This shows that the particles are much more compacted than for other sands tested. The fine sand range (0.063mm to 0.6 mm) registered large flow rate or discharge. It therefore has a high permeability, the highest concentration time of 265 seconds and is the best type of sand to be used. From thermal properties tables for sand, finer sands have less density than the sandstone (Challawa type) and lime stones of the same volume. This is an important parameter for design purposes. This system has a great potential to provide storage facilities for fruits and vegetables especially in places where air humidity is low or during periods of low humidity. This type of climatic condition is obtainable in most parts of Northern Nigeria.
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