Experimental and numerical investigations of latent heat storage and its application in solar adsorption cooling systems

Abstract

The intermittent nature of solar insolation severely affects the performance of solar Vapour Adsorption Cooling systems (VAC). A feasible solution to this problem is to employ a Latent Heat Storage (LHS) unit, which reduces the intermittency of energy input and simultaneously extends the operational period of solar VAC. However, the LHS unit faces the issue of low thermal response, resulting in prolonged charging time. In addition, it is necessary to reduce the size of the storage module, which in turn helps to compact the whole solar VAC system. The current study attempts to design an LHS unit by employing improved heat transfer augmentation features and a better materials selection strategy. newlineThe design of latent heat storage system necessitates the use of an appropriate Phase Change Material (PCM). In the current study a systematic selection of the PCM is performed using a multi-criteria decision-making technique, and the commercial PCM, savE-HS89, has been identified as the best candidate. The same technique is employed to select nanomaterials, which are introduced in this study to enhance the thermal conductivity of the base PCM. A hybrid nanomaterial combination of nAl2O3 and GnP is proposed to mitigate the unfavorable characteristics of GnP alone. The study evaluates the impact of nanomaterial through experimental characterization of the composite PCM, leading to the development of empirical correlations for its thermophysical properties. newlineIn addition to the hybrid nanoPCM composite, fins are provided in the LHS unit as another passive heat transfer augmentation technique. For vertically oriented LHS units, a tapered fin design is implemented to address the slow-melting characteristics observed in the bottom region. Subsequent to a numerical analysis, the actual performance of the LHS unit employed with tapered fins is assessed experimentally. Experimental investigation revealed the importance of tapered fins as they individually reduce the melting time by 46% and together with the hybrid nanoPCM combination