Numerical simulation effect of PCM storage on flat storage on flat plate solar heater in different kinds of weather conditions

Abstract

Abstract It can be concluded that by using phase change materials, a large amount of solar energy is prevented from being wasted. In other words, with the right choice of phase change materials, solar energy can be used to the maximum. At night and in cloudy weather, the amount of solar heat decreases, and the need to transfer heat from phase change materials to water is very significant. Certain groups of materials due to their good properties such as high latent heat, suitable phase change temperature, and small volume change during phase change are used for thermal management (temperature control of heating systems) in some thermal processes. These materials are called phase change materials. Therefore, most phase change materials are materials that store energy during the process of changing from solid to liquid and use chemical bonds to store and release thermal energy. Phase change materials, without the use of mechanical equipment and in a completely intelligent way and only through the innate tendency to change phase, naturally adapt to environmental fluctuations and reduce energy consumption. In recent years, due to the increasing demand for energy for industrial use on the one hand and the depletion of underground energy sources such as oil and coal on the other hands has led to the discussion of thermal storage systems based on phase change materials (PCM) in thermal storage. Based on phase change materials, large associations such as the World Heat Transfer Association and the Renewable Energy Association should be considered as an important issue. Due to this issue, the use of phase change materials in recent years, as an important and fundamental issue has been considered by many researchers and researchers. Water heaters and solar air heaters are used to heat the climate, respectively. A group of solar collectors known as dual collectors can heat the climate at the same time. The work done in this study was to investigate the effect of using a phase-change material in a dual-purpose collector. Below the adsorbent plate of the collector was a commercial paraffin wax. These phase change materials can be charged by the temperature of the absorber plate. The connection of the water heater to the collector was in the form of a thermosyphon, in the form of an inlet and an outlet, and the air heater was forced to work. This experiment was compared with another similar experiment but without the use of a modifier. The results showed that after reducing the radiation or lack of solar radiation, the collector reduced the stored heat and the heat transfer to the air heater of the collector was able to keep the air heater temperature significantly higher than the state without the use of alternating material. The aim of this study was to investigate the use of a PCM tank in a flat-panel solar collector. So far, many studies have been done on the use of phase change materials in a solar water heater, but so far, no study has been done to investigate the effect of different weather conditions on the performance of solar water heaters with PCM tank. The following figure shows the changes in heat flux during a sunny, cloudy day and partly cloudy day. The purpose of this study is partly cloudy. That is, when the solar flux suddenly decreases, which reduces the heat flux received and the water outlet temperature. In this study, using PCM, we intend to keep the water outlet temperature constant by storing thermal energy in clear climates and releasing the thermal energy stored in PCM. As can be seen in the pictures, the solar heat flux received during a completely sunny day has been steadily increasing until noon, while for a mostly cloudy day, the heat flux has been steadily increasing until the clouds arrive. With the arrival of the clouds, the heat flux suddenly decreased by about 20%, and after the clouds passed (about an hour), the heat flux increased again to the maximum value. Due to the increase in sunlight on a completely sunny day during the day, the amount of heat flux should increase and reach a maximum around 12 o’clock. But on a partly cloudy day with a sudden drop in flux at 12:30, the outlet temperature drops dramatically. So that in less than 8 min, the temperature drops by 10°, and this temperature drop continues until the end of the period (13:00). This indicates that the energy stored in the absorber plate prevents a sudden drop, although the rate of heat loss is high, but occurs within 8 min. After the start of the solar flux process (13:00), the heat flux increases again and reaches the normal value, and within 4 min, the output temperature returns to its maximum value. According to the obtained results, it shows that on partly cloudy days, the amount of drop and decrease in heat flux reaches 20%. Also, the fan can be used to increase the contact surface with PCM. As a result, the amount of melted PCM increases and the heat transfer time from PCM to water (at night) increases, and the efficiency increases.