Influence of orientation on thermal performance of shell and tube latent heat storage unit

An experimental investigation is reported to establish the influence of orientation on thermal behaviour of phase change material (PCM) in a shell and tube type Latent Heat Storage Unit (LHSU). An angle adjuster is provided in the experimental test facility to orient the LHSU at different angles. Stearic acid is used as PCM (melting point - 55.7 to 56.6 degrees C) and water is used as a heat transfer fluid (HTF). Total 45 thermocouples are embedded in the annulus to measure the PCM temperature in axial, radial and angular direction. Comparison of melting behaviour of PCM for different orientation is reported in terms of radial, axial and average temperature distribution. It is observed that half of the PCM mass melts rapidly for horizontal orientation (theta = 0 degrees) of LHSU owing to strong natural convection in the upper half of the horizontal diametric plane. It is also established that for the case when the LHSU is oriented at theta = 45 degrees, the average PCM temperature is higher compared to other inclinations fox the same HTF inlet condition. Hence the melting time required is the lowest for this orientation. Energy storage rate which decides the use of LHSU in large scale solar thermal applications, is significantly influenced by orientation.