| The level of economic development grows rapidly, a large area of urbanization carries on in the country. In this context, the improving of living environment has become an urgent requirement. Air-conditioning system is an important means to create a good indoor thermal environment. Traditional air-conditioning system is based on the entire air-conditioned room for adjustment object. That consumes large amounts of energy and is difficult to ensure the effect of the adjustment. In such cases, it is very important to study new air-conditioning system for HVAC air conditioning professional.Radiant floor cooling and displacement ventilation are as the new air-conditioned widely applied. Both reflect advantage that the traditional air-conditioning methods cannot match in energy efficiency. But it exposed inadequate in creating a indoor thermal environment. Displacement ventilation can ensure the freshness of the indoor air, but cooling capacity per unit area is small. The surface of flooring radiant cooling easily to condensation, cannot guarantee the quality of indoor air. The air-conditioning system of floor cooling in displacement ventilation conditions has unique advantages in many aspects. The coexistence of convective heat transfer and radioactive heat transfer is the heat transfer characteristics of such air-conditioning systems. The radioactive heat transfer heat evenly, room temperature gradient is small. The radiation heat is in a large proportion of this air-conditioning system, there are great advantages in terms of the effect of heat transfer. In the using of refrigerant, it does not require low temperature chilled water. This created the conditions for the using of low-grade energy. It overcome the shortcomings of condensation by using displacement ventilation system, and at the same time provides fresh air to the indoor. It solves the "hot" problem of floor radiant cooling.This paper first introduces working principle and characteristics of the air-conditioning system of floor cooling and displacement ventilation. By reference to the current specification and international general standards, further elaborate on the evaluation standards of the indoor thermal environment of displacement ventilation and floor radiant cooling comfort, it provides beneficial theoretical basis for the use of this new type of air-conditioning system.When rating internal environment according to the international general ISO7730standard and index PMV/PPD, a separate use of floor radiant cooling with displacement ventilation system can’t satisfy the thermal comfort requirements. The floor radiant cooling air-conditioning system and displacement ventilation air-conditioning system are separated simulated, selecting parameters and to establish a reasonable system model room, setting the model boundary condition, using CFD software simulation verify the limitations of a single air-conditioning system.Finally, on the basis of reasonable simplification a physical model of an office through simplification is established. The using radiant floor cooling system, displacement ventilation system and the replacement composite floor radiant cooling ventilation air-conditioning systems corresponding physical model in the specific boundary conditions. The model by CFD software to simulate the three systems in the summer cooling season of indoor temperature field, velocity and relative humidity field distribution, through the use of internationally accepted evaluation of indoor thermal environment PMV-PPD criteria analysis to find form of air-conditioning systems to meet the requirements of indoor thermal environment, come to the interests of the working parameters of the air conditioning system to achieve the best operating conditions, to provide technical reference for system design and operation.The results show that the composite displacement ventilation, radiant floor cooling air-conditioning system to create a good indoor thermal environment。The floor surface temperature and supply air temperature are the important factors to form the indoor thermal environment. The floor surface temperature lower than supply air temperature is good for form good indoor thermal environment.. |
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