The problems of heat and mass transfer in PHASE CHANGE MATERIALS are of great engineering interest. The absorption and storage of energy in the form of latent heat makes it possible to use them in the construction industry to smooth out the effects of temperature transitions in the environment. This work is devoted to the study of heat transfer in a building block with paraffin inserts under unsteady external conditions. The influence of the geometric dimensions of the block and the volume fraction of the PHASE CHANGE material on the effect of restraining external temperature fluctuations was studied. The unsteady conjugate melting problem was solved in a closed rectangular region with two cavities filled with PCM. The temperature of the environment on the left boundary CHANGEs in harmonic law. Thermal distributions were obtained at various points in time.

Increasing energy consumption in today's world and the resulting major environmental problems have made efforts to develop renewable energy and reduce energy consumption as an effort to improve environmental issues, especially global warming, become a major concern in modern world research. It is predicted that by 2050, energy consumption and environmental damage will increase by 1. 8% annually. In addition, with the sharp increase in cooling and heating needs in various industries, and especially the need for thermal energy around the world, the need for appropriate technology that improves thermal performance in various systems, is very important. The result of these restrictions has been a move towards renewable energy and a reduction in fossil fuel consumption. On the other hand, new technologies such as batteries and drugs are highly dependent on temperature CHANGEs. The use of PHASE CHANGE MATERIALS (PCMs) to store thermal energy in various industries can solve energy shortage problems. This article provides an overview of energy management practices using PCMs. The background of PCMs in different industries was also examined. The application of PCMs in construction, batteries, home water heating systems and other applications was investigated. A summary of the PCMs used is also provided.

PHASE CHANGE MATERIALS are substances that absorb and release thermal energy during the process of melting and freezing. This characteristic makes PHASE CHANGE material (PCM) a favourite choice to integrate it in buildings. Stephan problem including melting and solidification in PMC MATERIALS is an practical problem in many engineering processes. The position of the moving boundary, its velocity and the temperature distribution within the domain are important for these applications. Well known numerical techniques have difficulties with time-dependent boundary conditions. Therefore, fine mesh and small time steps are needed to obtain accurate solutions. There are two main approaches to solve the Stefan problem: front-tacking and variable grid method. The most existing methods are not applicable to all situations and they cannot be easily implemeted in two-dimensional or threedimensional geometries and all boundary conditions. In this paper, we proposed an algorithm to solve one-dimensional Stefan problem in all kind of boundary condition; also it can be easily extended for 2D and 3D Stephan problems using finite difference method. For validation, the results are compared with exact solution of constant boundary condition. Afterward, periodic boundary condition is considered. The results showed significant relationship between numerical and exact solution, and the maximum error was approximately 0. 4%.

Environmental concerns and the scarcity of fossil fuels have led to the rapid development of rechargeable battery technologies. It has been proven that the performance of lithium-ion batteries is susceptible to temperature, and temperature significantly affects the capacity and power of batteries. Therefore, it is necessary to build an efficient battery thermal management system to maintain the battery's operating temperature in a safe range. Utilizing PCM. s can be an exciting option in thermal management systems of lithium-ion batteries, and several studies have been conducted about them. The biggest challenge in PCM-based BTMS systems is to overcome the problems related to the poor thermal conductivity of PCMs. Many researchers in this field proposed different types of metal fins (pinned fins, circular fins, longitudinal fins, and triangular fins), metal foams (aluminum, copper, and nickel foam), metal meshes, and carbon-based nanoMATERIALS to increase the thermal conductivity in PCM-based BTMS systems. Some proposed carbon-based composite nanoMATERIALS are expanded graphite, carbon nanotubes, and carbon fiber. In this article, recent developments and new methods of thermal management and performance optimization of lithium-ion batteries have been reviewed.

In this paper, the effect of buoyancy force on the temperature CHANGE of the PHASE CHANGE MATERIALS which has been encapsulated in two pipes in a channel, is simulated numerically using Boussinesq approximation. An application of this topic is in air-conditioning, which uses ice in the pipes as PCM for coolant and the aim is calculating the PCM discharging time. The unsteady governing equations including continuity, momentum and energy in the fluid flow and PHASE CHANGE material for laminar flow regime, have been solved by the well-known SIMPLE method. The needed time to PHASE CHANGE material reach the inlet temperature of the fluid flow has been obtained and compared to the results of the lumped temperature assumption. The results show that the discharging time is 4,000 for Gr=5,000 and 70,000 for Gr=200,000. It is 25,000 for kr=0.5 and 34,000 for kr=1.5. Also, it is 11,000 for Cpr=103 and 28,000 for Cpr=104. Finally, it has been concluded that due to the fine mixing of PCM because of buoyancy force, the results are so closed to the results of the lumped temperature assumption for PCM.

One of the main problems of crops dryers is their high cost, high energy consumption, and the associated higher cost of operation. The solution proposed for this problem is use of the free and clean solar energy. In this study, a solar dryer was developed, which consisted of a solar collector that innovatively is made of discarded waste MATERIALS such as cold drinks metal cans. Also PHASE CHANGE MATERIALS (PCM), was included in the dryer chamber for energy storage, and was tested under laboratory conditions, and air flow rate, temperatureand radiation intensity were measured. According to the results, the temperature of the absorber plate of the innovatively solar collector increased up to 111 º C and the temperature of the exhust air had a difference of 50 to 60 º C compaed to the ambient temperature. Highest tempratur increase was obtained with air velocity of 0. 5 m/s at 2-3 PM in test days. The PHASE CHANGE temperature of the MATERIALS occurred at 51 to 53 º C. When the chamber temperature exceeded 53 º C, the material’ s PHASE CHANGEd and the stored heat was directed to dryer in order to compensate for the tempratuer drop in the plenum. . As result, the temperature loss of the drying chamber occurred less severly under the PHASE CHANGE material conditions, because it slightly prevented temperature loss. Finally, mintdrying test was carried out. The mint with an initial miostuer content of 86 percent, lost 86g of its moisture and reached final moister content of 12 percent during the product test in 273 minutes, under mean chamber temperature of 44. 3 º C and air velocity of 0. 5 m/s.

The energy crises of the current century, led humans to ponder new energy sources. One of the interesting methods is the application of PHASE CHANGE MATERIALS (PCMs), which is not only used for the purpose of storing heat energy but also is used for the purpose of heat insulation. Besides their advantages, PCMs may have some limitations such as leaking problems and low thermal conduction coefficient. Thus, adding metallic nanoparticles and shell-core structures can improve their thermal properties. In this research, N-octadecane is chosen as core and methyl methacrylate as a shell to synthesize nanoscale MATERIALS with core-shell structure. In this work, instruments including SEM, DSC, TEM, and sonicator have been used. The results of the experiments showed that synthesized PHASE CHANGE MATERIALS have a mean 79 nm diameter and have a core-shell structure. On the other hand, slurry nanoPHASE CHANGE MATERIALS have maintained their thermal properties after many cycles and this can be considered as the main advantage in thermal management of different systems. In summary, it is revealed that PCMs and their composites possess advantages in thermal applications. These MATERIALS can have a critical and valuable role in thermal management.

The energy crisis in recent years has to lead us to think about new sources of energy. PHASE CHANGE MATERIALS are one of these efficient sources. They can be used as thermal insulators besides their heat storage applications. Also, implementing these MATERIALS has erased our need for immunization of energy consumption systems. Despite all the benefits, PHASE CHANGE MATERIALS have some limitations such as leaking problems and low thermal conductivity coefficient. Nanoparticles are therefore can improve their properties. In this study, the melting process of paraffin wax comprising nanoparticles of Al2O3, Fe2O3, SiO2 and ZnO (with weight fraction percentage 2% and 8%) in a rectangular container is simulated by Comsol software. Influence of nanoparticles with different weight fractions on temperature, velocity distribution, density, thermal conductivity coefficient and liquefy process are subsequently investigated. The results presented a 12. 5% increase in the thermal conductivity coefficient by adding 8wt% nanoparticles. The rate of melting process in 8wt% nanoparticles is bigger than that of 2wt% nanoparticles and pure paraffin with similar initial and boundary conditions for all states, which indicates that adding nanoparticles to paraffin for increasing the melting rate can be useful in various thermal management purposes such as storing energy.