Experimental Investigation and Analysis of Compact PCM filled Thin Tube Latent Heat Solar Water Heater

Abstract

Energy storage leads to saving premium fuels and makes the system more cost effective by reducing the wastage of energy. In most systems, there is a mismatch between the energy supply and consumption of energy. The energy storage systems can overcome the imbalanced system and thereby helps in saving capital costs. It is desirable for more effective and environmentally benign energy use. A variety of thermal energy storage techniques have been developed over the past four to five decades. Solar energy is a major renewable energy resource, the intermittent nature and its effective utilization is in part dependent on efficient and effective energy storage systems. Latent Heat Thermal Energy Storage (LHTES) system has always been closely associated with solar installations, including both industrial solar heating and domestic heating. The use of a latent heat storage system using phase change materials is an effective way of storing thermal energy and has the advantages of high energy storage density and the isothermal nature of the storage processes. Hence LHTES is a high density of energy storage system, comparing with the conventional Solar Water Heating systems (SWHS). newlineIn the present research work on LHTES system, the thermal energy storage tanks are insulated by glass wools and Poly Urethene Foam (PUF) in order to minimize the heat losses from the tank. In the thermal storage tank, totally 90 copper tubes are used and phase change materials are filled up in each tube. After the well-focused way of analyzing the varieties of phase change material (PCM), the suitable PCM are identified and used for the thermal storage system. In order to store the heat energy in the tanks, copper tubes are filled with three different paraffin wax with three different phase change temperatures are separately filled in three set of packs are used and accordingly the LHTES system is designed and fabricated. newlineLarge quantity of heat energy is absorbed by LHTES system in the day time in the form of Latent heat and little Sensible heat in the water. During the newlinevi newlinecharging process the heat energy is stored in the PCM filled copper tube as latent heat and the same heat is recovered during the discharging process using cold water. The PCM enhances the heat storage capacity of the conventional solar tanks used in domestic solar water heaters. The tank is instrumented for measuring inlet and outlet water temperatures and also flow meters are used to vary mass flow rate. The tank is continuously monitored and various readings are noted at regular interval of time and also graphs have been plotted. The temperature distribution in Heat Tranfer Fluid (HTF) and PCMs are analyzed by computational fluid dynamics (CFD) at steady state and transient conditions.The phase change material is a substance which melts and solidifies at certain temperature with a high heat of fusion capable of storing and releasing large amount of energy during phase change. PCM is considered as one of the major heat storage material in industrial thermal applications. newlinePCM being compact heat storage material is used in different thermal storage system but during encapsulation in different containers, because of its high co-efficient of thermal expansion during its phase change, it is difficult to design the containers. This work is emphasized on the study of co-efficient of thermal expansion and contraction during its phase change. newlineThere are more system failures happening in the PCM based thermal storage systems because of the pressure built up inside the PCM containers during the expansion and contraction. This research was intended to nullify or to ensure that there are fewer failures due to PCM leakages that happen during the pressure built-in due to high temperature. To ensure this, a separate and parallel research work was under taken to calculate the exact free space left inside the encapsulated vessels and also the entire working system for its safer working. newlineThe experimental and CFD analytical results reveals that, the conformity between the two results during charging and discharging process of PCM filled thins tubes, and also the thin tubes are enhancing thermal conductivity even during discharging process. newline