Using the lattice Boltzmann technique, the mixed convection of nanofluid inside an inclined trapezoidal cavity in the presence of a multidirectional magnetic field is investigated. The sides of the trapezoidal hollow are adiabatic, with the upper moveable wall being cold and the lower wall being sinusoidally heated. In simulations, the temperature and flow distribution functions are utilized to determine all parameters related to the temperature and flow fields. On the hot wall, the effects of various Rayleigh numbers (Ra = 103, 104, and 105), inclined cavity angles (θ= 0°-90°), volume fractions of nanoparticles (ϕ== 0-3 percent), magnetic field intensity (Ha = 0-100), and applied magnetic field angle (= 0°-90°) were studied. According to the research, raising the Rayleigh number enhances heat transfer. Moreover, when all other parameters are held equal, raising the nanoparticle volume fraction enhances the average Nusselt number. Increasing the Hartmann number reduces the flow velocity inside the cavity, hence reducing heat transmission. Changes in the cavity's slope and the angle of the applied magnetic field have an effect on the flow and heat transfer as well. Manuscript profile

Nowadays, the use of phase change materials is very important to reduce energy consumption in buildings and industry structures. The use of phase change materials in the structure of buildings will be widely used in the near future. Because the presence of these materials in the building structure, such as the use in water heater cultures, will reduce the consumption of fossil energy.Phase change materials (PCM) store thermal energy in the latent heat method. These materials have a high thermal storage density and with small temperature changes, they provide an important role in saving energy and thermal insulation in the building. Materials naturally delay the transfer of heat to the building by several hours due to the reduction of indoor air temperature fluctuations and the room air temperature remaining close to the desired room temperature for a longer period of time. In order to recover heat or cold, the storage method is used. In general, there are two types of thermal energy storage systems during physical processes:1- Storage of sensible thermal energy ,2- Latent thermal energy storage. In this article, we investigated the use of phase change materials in the solar collector installed in the building. In this article, Ansys Fluent software is used for simulation. The amount of solar radiation in Iran is estimated between 1800 and 2200 kilowatt hours per square meter per year, which is higher than the world average. Manuscript profile

Phase change materials in the structure of buildings reduce energy consumption and increase the storage of renewable energies .In this study, in order to investigate the effect of phase change materials on the performance of a solar collector in unstable weather conditions (cloudy weather) in Tehran, numerical simulation of the collector was carried out using Ansys Fluent software. For this purpose, four scenarios were examined and numerically simulated. In the first scenario, the performance of the solar collector was investigated in the stable weather conditions of Tehran city without the use of phase change material. The results showed that the desired solar collector can raise the water temperature to 38 degrees Celsius. In the second scenario, to investigate the effect of air instability and cloudiness on the performance of the collector, it was assumed that the solar radiation will decrease. The results showed that the temperature of the outlet water of the collector decreases from 38 degrees Celsius to 35 degrees with the reduction of sunlight. In the third scenario, the effect of using phase change materials on the performance of the collector in stable weather conditions was investigated. The results showed that the use of phase change material in the collector causes heat storage and increases the water temperature when the solar radiation decreases to 37 degrees Celsius. Also, the use of phase change materials in unstable weather conditions caused the water temperature to increase to 41 degrees Celsius. Manuscript profile