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Augmentation of the charging/discharging rate of the latent heat storage unit (LHSU) is one of the challenges in the design and development of the energy storage unit. Natural convection plays a pivotal role in this aspect which gets influenced by the inclination at which LHSU is placed. Employing radial fins enhance the heat transfer rate but there is a possibility of suppressing the natural convection. Providing perforations on the fins could assist the melted PCM to flow freely upwards and hence can overcome the issue of attenuation of natural convection. However, the orientation of LHSU may alter the influence of perforations. Hence in the current study, a comparative analysis on the thermal performance of a LHSU with solid and perforated fins at different orientations is presented. Experiments are carried out for both melting and solidification processes. It is observed that irrespective of the type of fin, orientation has a significant effect on the melting process. Regardless to the type of fin, total melting time is found to be 48% lesser in the vertical configuration in comparison with horizontal configuration. The considered design of perforations is found to be more effective in a vertical configuration as they increased the energy storage rate in the initial stages of melting. At other orientations, perforations do not have an ample effect. Fin effectiveness is observed to be 5% more in the case of solid fins in comparison with perforated fins at all the orientations. For the solidification process, orientation and perforations have negligible effect as the discharging process is conduction dominant. Exergy efficiency is noticed to be higher for vertically oriented LHSU in both the types fins during the charging process. During solidification of PCM, exergy efficiency is noticed to be same at all the orientations irrespective of the type of fin. [ABSTRACT FROM AUTHOR]

In this study, pure beeswax and its novel composite with expanded graphite (10% wt.) were tested for thermal storage efficiency in a rectangular shell and helical tube storage unit. Low thermal conductivity of beeswax is improved by adding expanded graphite of 10% wt. Thermal characterization of beeswax and its composite was performed using differential scanning calorimetry and thermogravimetric analysis. Effect of hot fluid flow rates (0.25 liter per minute [LPM], 0.5 LPM, and 1.0 LPM) and inlet temperatures (60ºC, 70ºC, and 80ºC) on the charging time of beeswax and its composite was studied and compared. Charging time of beeswax and its composite reduced with an increase in fluid flow rate and inlet temperature. At 0.5 LPM flow rate and 80°C inlet fluid temperature, the charging time of composite was reduced by 630 min as compared to pure beeswax. Smaller charging time, improved thermal conductivity, and better thermal storage efficiency of composite material suggest it as a useful storage material for a wider range of applications. [ABSTRACT FROM AUTHOR]

Thermal storage plays a vital role in improving the overall efficiency of a waste heat recovery system. A phase change storage system exhibits high energy storage density and isothermal behavior during the charging and discharging processes. In the present work, the cascading arrangement of the phase change storage system is studied to analyze the improvement in the efficiency of the storage system during the charging process, and to compared it with a single storage tank system. The performance parameters, such as the amount of heat recovered, the heat lost, charging rate, charging efficiency, and the percentage of energy saved, are investigated in detail. [ABSTRACT FROM PUBLISHER]

A ventilated cooling ceiling with phase change material (PCM) was installed and measured in a 20 m2test room. The PCM used was DELTA®-COOL 24, a salt hydrate from the company Dörken with a melting range of 22–28°C. The PCM was encapsulated in polycarbonate containers which were laid on top of the bearing for the plaster boards. The amount of PCM installed was 9 kg/m2. The ceiling was rear ventilated to improve heat transfer between the PCM and the room air. During the cooling mode, the ventilation was purely in circulating operation with a volume flow rate of 97 m3/h (air exchange rate of 2/h). To regenerate the PCM, cooled air was inserted into the ceiling with a volume flow rate of 140 m3/h (air exchange rate of 3/h). Different positions for the containers were tested. The PCM in the ceiling delayed the rise in the room air temperature significantly. The PCM stayed active for 12–16 h, depending on the position of the containers. While the cooling power of the air flow alone was very small (30–40 W for the 20 m2test room), a significant amount of heat was transferred directly through the plaster boards of the ceiling. [ABSTRACT FROM AUTHOR]

A prototype of a solar chimney with a built-in latent heat storage system for prolonging ventilation system operation until evening/night or even 24 hours was designed and developed. Sodium Sulfate Decahydrate "Na2SO4.10H2O" (melting point 32°C, latent heat of fusion 126 kJ/kg) was used as a Phase Change Material (PCM) for latent heat storage. Experiments have been carried out with the air gap of 0.20 m and 45 degree inclination angle of solar chimney. Results showed that integration of PCM storage inside the solar chimney is positive and supplies a constant airflow rate of 155 m3/h in evening and night periods. Description of the fabricated prototype solar chimney with PCM storage, thermal analysis to predict the air flow rate, and temperatures of the component of the system with experimental results are presented. [ABSTRACT FROM AUTHOR]

With rising energy costs and an increasing demand for renewable energy sources, thermal energy storage (TES) systems are becoming an interesting option. TES is a key component of any successful thermal system and a good TES should allow minimum thermal energy losses. In this study, various ways of thermal conservation are outlined and discussed, both theoretical and experimental. In this respect, the TES systems and their practical applications and some selection criteria have also been given. [ABSTRACT FROM AUTHOR]