| With the improvement of living standards in our country,the requirements of Chinese residents for heating in winter are increasing.The method of electric heating has been widely concerned,compared with the traditional centralized heating,because of its rapid hot start,high thermoelectric conversion efficiency,environmental protection and cleanliness.At the same time,many regions have introduced a time-phase electricity price policy to address the large difference between the peak and valley of the grid load in recent years,which provides policy support for the wide application of electric heating.This paper proposes a heating scheme that combines a carbon fiber heater with a porous medium heat storage material,in the context of the power grid cutting peaks and valleys.This paper studies the thermal characteristics of heat storage electric heaters,as well as the temperature and flow field characteristics of heated rooms,through experimental and numerical simulation methods.The specific work of the thesis is as follows:In the aspect of numerical simulation,the physical model of electric heater made of the thermal storage porous medium and carbon fiber and the room physical model were established respectively on the platform of commercial software Fluent.This paper analyzes the variation of temperature field and velocity field in the heated room,and then the room heating effect is studied in the thickness and porosity of different porous medium heat storage structures.The results show that there are three typical stages in the process of heat storage heating: heating delay phase,warming and heat storage phase,and heat storage working phase,so the temperature changes are different in each phase.The data shows that the overall temperature distribution of the room temperature is the warm upper part and the cold lower part,specifically the temperature difference within 3°C,and the air flow rate no more than 0.4m/s.In addition,both the extreme values of temperature and flow rate appear above the heater and near the outer wall.In the experimental research,two kinds of electric heater experimental devices of direct heating type and thermal storage type were established,then the heating/heat dissipation experiments were carried out separately.The influence of the porous medium heat storage layer is analyzed on the temperature field inside and outside the electric heater.The overall temperature field in the process of direct heating heater shows that the upper temperature is greater than the lower temperature and the intermediate temperature is greater than the edge temperature.The temperature distribution is more uniform of the heating plate of the thermal storage electric heater,and the cooling rate of the thermal storage process is significantly lower than the direct heating process.The smaller diameter of the ball,the slower temperature changes of the heating plate.In addition,the maximum temperature on the shell of the thermal storage heater is lower than the direct heating heater.In order to analyze the thermal comfort of the heating room,this paper makes a reasonable evaluation on the thermal environment of the room in the heating process based on the predicted average-expected dissatisfaction percentage(PMV-PDD)model.The model discusses the thermal comfort of the heated room by calculating the PMV values in all directions.The results show that the temperature of the environment in the room reaches the ideal standard after 50 minutes of operation of the thermal storage electric heater,and the effective heating time of the electric thermal storage heating can reach 2.05 hours.In addition,near the electric heater,the PMV value is close to the ideal value,and the thermal comfort is better than other areas;near the outer wall and the ground,the PMV value deviates greatly from the near ideal value and the thermal comfort is worse. |
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