Papers by Keyword: PCM

Abstract: This work numerically studies the thermal management of a Li-ion battery pack using Phase Change Materials (PCMs) with two different modelling approaches. Specifically, the results obtained with the Enthalpy-Porosity method, implemented in the tool STAR-CCM+, are compared with those yielded by the Apparent Heat Capacity formulation, employed by COMSOL Multiphysics. Both models are first validated against benchmark cases found in the literature. The study then focuses on the thermal behaviour of a battery pack composed of four 21700 Li-ion battery cells, cooled using the paraffinic PCM RT35. The numerical results show that, while natural convection in the liquid PCM accelerates the melting process, it leads to a non-uniform temperature distribution, particularly disadvantageous for cells located in the upper part of the battery pack. In addition, although both numerical approaches show good agreement between their results, especially in capturing the overall thermal behaviour, some minor differences in the temperature profiles during the PCM phase change still emerge.

Abstract: This work presents results of a study of the influence assessment based on the recorded acoustic emission (AE) parameters of thermo-oxidative aging conditions on the destruction process of a polymer composite material (PCM). The objects of the study were specimens cut from a fiberglass reinforced plastic (FGRP) plate. The plate was made by vacuum infusion technique using Derakane 411-350 resin and 9 layers of St-62004 glass fabric. Specimens aging were done by holding in a muffle furnace for 96 hours at temperatures of 60, 100, 120, and 200 ° C. Mechanical test was the three-point static bending method. For the AE recording was used a hardware-software complex developed at KnASU. The AE signal Fourier spectra were two-stage clustered with the self-organizing Kohonen map according to the technique previously developed and tested by the authors. The types of the PCM structure damage were characterized by the obtained clusters centroids. The fracture process kinetics is described depending on the conditions of thermo-oxidative aging and based on the accumulation of clusters during mechanical tests. The negative influence of high temperatures on the polymer matrix degradation, leading to a decrease in the ability of the matrix to effectively distribute internal stresses over the PCM volume due to the adhesion corruption with the reinforcing material, has been established.

Abstract: In its use, reefer containers require a lot of energy to operate to cool the cargo inside. Because the cooling system in the reefer container must operate continuously to maintain the temperature in the container. To reduce the operation of the cooling system, reefer containers are equipped with PCM (phase change material) as thermal energy storage which can store heat energy longer to create a lag time for the operation of the cooling system. In previous research, the use of PCM in cold storage can save the cost of using cold storage. From this research, the use of PCM in reefer containers was developed. The eutectic mixture used as PCM is NaCl-H2O with additional ingredients is propylene glycol. Before being applied to the reefer container, the mixture was tested using the cooling chamber methods to determine its thermophysics. The presence of additives in the PCM eutectic mixture is expected to reduce the supercooling phenomenon, reduce corrosive properties and increase the use of PCM based on NaCl-H2O.

Abstract: The paper presents the results of the study of registered acoustic emission (AE) parameters during static deformation and damaging of polymer composite materials (PCM). Mechanical tests were done by a static tension and a static three-point bend, accompanied by an acoustic emission method. The assessment of the loading rate effect on defects formation processes was done by additional static tension test at rate equal half of recommended by the standard and static three-point bend test at rate ten times lower than that calculated by the standard. Clustering by frequency components of the recorded AE signals with a self-organizing Kohonen map was performed. The characteristics of the types of PCM structure damage by the centroids of the obtained clusters are given. Based on the clusters accumulation during mechanical tests, the stages of damage formation for static tension and static three-point bend, the loading rate effect on the process of damage formation are described.

Abstract: Solar thermal energy is one of the promising renewable and sustainable energy that have gain research interest. However, the nature of intermittent solar irradiation limits the usage of this energy. Phase change material (PCM) are substance that has the property of absorbing and releasing thermal energy through phase transformation. Combination of graphene foam/PCM composite will be able to absorb heat from solar thermal energy and sustain energy release to thermoelectric generator (TEG) for electrical conversion. Two different PCM material were tested which are petroleum-based paraffin wax and bio-based PCM beeswax. Thermal properties of both materials were measured using DSC and heat absorption were tested under real solar irradiation. This solar-thermal converter showed that graphene/paraffin/beeswax composite is more effective than the paraffin wax or beeswax alone. The recorded results also showed that combination of these petroleum based and bio-based PCM with added graphene foam could retain longer heat than graphene/paraffin wax and individual PCM. The longer heat can be stored in solar-thermal converter device may sustain electricity generation even with absence of solar energy.

Abstract: A TRNSYS model of a novel PCM heat storage, utilizing stable supercooling of Sodium Acetate Trihydrate (SAT), is presented. To achieve high solar fractions in heat supply of single family houses, the necessary integration of big water volumes is challenging. To evaluate its functionality, a system model of a solar thermal combisystem for space heating and domestic hot water supply for dynamic system simulation was built. The key component is a PCM volume for long term heat storage. While conventional heat storage concepts with SAT release the latent heat a few degrees below the melting temperature, with the concept of stable supercooling latent heat can be stored for long periods of time at ambient temperature. This allows the design of a partly loss-free storage. Solar fractions were evaluated for simulation runs with two building variations. Annual specific space heating demands of 15 and 30 kWh/(m2a) and a domestic hot water demand of a typical single family house were considered. A sensitivity analysis on solar fractions of domestic heat supply was performed by variation of the collector field and the PCM volume. While the increase of the PCM volume from 4.5 m³ to 9 m³ shows moderate effects in all simulation runs, an increase of the collector area has substantial effects on the share of solar heat on the total energy demand of the building.

Abstract: This work presents a numerical study of the phase change process of PCM (Phase Change Materials) stored in spherical cavities. The numerical model is two-dimensional and it is composed by the equations of conservation of mass, momentum, energy and volumetric fraction, which are modeled using the enthalpy-porosity technique. The computational mesh is tetrahedral, with refinements on regions that have large thermic and fluid dynamic gradients. The numeric model was validated with result from literature. It was studied the melting process of PCM RT35, RT 55 and RT 82 in spherical cavity with constant wall temperature. Four diameters of spheres D were used (40, 60, 80 and 100 mm) and three temperature differences ΔT (10, 20 and 30 oC) between the wall temperature and the melting temperature of the PCM. Liquid fraction results from the 36 cases studied are presented. It was observed that the time required to reach a certain liquid fraction increases with the diameter and reduces with the increment of ΔT, being possible to predict the fusion time by knowing the characteristic length of the sphere. The largest percentage reduction of the fusion time was obtained with ΔT = 10 oC – 20 oC for all the D considered. The shortest fusion time was obtained with the largest ΔT combined with the smallest D. It is possible to see the dependence of the liquid fraction results in relation with the PCM properties and the its independence in relation its melting temperature, since all the PCM studied presented equal fusion time for the same ΔT and D.

Abstract: The present work numerically investigates for a latent heat thermal storage (LHTS) unit, the effect of key design parameters such as the inlet temperature of the heat transfer fluid (HTF), initial and melting temperatures of the PCM, thermophysical parameters such as specific heat, thermal conductivity etc., on its performance. A numerical model has been developed considering the discharging mode of operation and solved employing finite difference technique. The parametric study reveals that the effect of HTF inlet temperature on the unit's thermal response is more compared to initial temperature of the PCM and the influence of thermal conductivity of the PCM is very strong compared to specific heat capacity of the solid PCM

Abstract: This paper deals with an optimal design solar tower power plant. Special attention is focused on the central receiver system and heat storage materials. In order to get an effective power plant, a simple mathematical model to calculate the solar energy, concentrated on the solar receiver during one year, is developed. The model can predict the delivered energy in dependence on the arrangement of the heliostats and the height of the solar receiver. By using an optimizer, a plant of 5 MW power is optimized in order to produce a maximum of electrical energy during the year on the prescribed area. On the basis of analysis of heat storage materials, KNO₃, acting as phase change material (PCM), is shown to be suitable for heat storage from the thermal, physical, kinetic, chemical, and economic point of view.

Abstract: Abundant availability of solar energy and fast depleting fossil fuel reserves have necessitated deployment of large scale solar thermal systems for meeting the space heating, process heating and drying requirements. Researchers worldwide have focused on developing energy efficient dryer capable of enhancing product quality, reduced drying time, high throughput, minimal pre-treatments prior to drying with less energy loss in cost effective way. The present paper surveys literature on performance enhancement studies on solar dryer with a thrust on energy efficiency improvements in solar air collector and a multipurpose solar drying system. The effect of adoption of absorber plate with different types of fins, design modifications, CFD based optimization techniques and incorporation of storage materials have been reviewed. A dual-purpose solar water heating and drying system with phase change material (PCM) is suggested for effective harnessing of solar energy.