| In recent years, with the rapid development of China’s construction industry, building energy consumption continues to grow rapidly. Higher requirements for building energy efficiency should be put forward. Energy for heating and cooling is dominant in building energy consumption. It’s important to minimize energy consumption when a comfortable indoor environment is achieved in the built environment. The advance in new energy-saving technology allows for low-temperature heating and cooling systems, such as low-temperature radiant floor heating technology, capillary tube radiant heating and etc. which are increasingly adopted in the heating and cooling system in the building. Radiant heating and cooling load is essential for the radiant heating and cooling system design. However, the development of innovative design requires modification of existing methods for radiation load estimation. Moreover, new method should be proposed since heating and cooling from radiation of the system is emphasized in the emerging radiant heating and cooling modes, local heating radiant heating and cooling and diverse personalized radiation end. Based on thermal balance and the natural convection, a new approach for radiant heating and cooling load index calculation is proposed to meet the requirement of system design.First, three rooms with different floor areas(15m2,24m2 and 35m2) are selected to calculate the view factor of each wall with different occupant postures, respectively. Three methods, including the direct integration method(human body is simplified to the ball model and the rectangular model), contour integral method and photogrammetry, are adopted in the caculation. The results show that the view factor calculation methods, occupant postures and room areas have a significant impact on view factor. The influence of calculation method on the radiation view factor is greatest and followed by body posture. The floor area of the room has the lightest impact.Secondly, experiment and CFD-Fluent simulation are conducted to investigate the average intorier wall temperature and indoor air temperature with different radiation laying position(floor, ceiling, wall), radiation area ratios(50%, 100%) and different surface temperatures(heating 25℃, 30℃, 35℃; cooling 22℃, 20℃, 18℃). The total load index of radiation system is consisted of radiant load and convection load. Under steady-state conditions, the operating temperature is studied and the radiant heating and cooling thermal equilibrium equation is established to obtain the radiant load index. While, convection exchange load index is calculated based on the natural convection thoery. Then the relationship between the total load index and the operating temperature for engineering application guidance can be established. The floor heating and the ceiling cooling turn out to be most effective design.Finally, using the same load calculation method, the influence of the shade on effects of the floor heating and floor cooling is analyzed. Shade has significant impact on radiation. The increase of shadow area leads to the decrease of radiation heating and cooling and decrease percentage reduces in the process. |
