CFD Numerical Simulation Of Air Distribution And Analysis Of Thermal Comfortablity On Delaminated Air-conditioning System In A Large Space Building

Stratified air-conditioning technology is widely used in large space building. Proper air flow is used to air-condition in the lower part of building, and there is no air-conditioning or only ventilation and exhausting heat in the upper part of building. It results in lowing air-conditional cooling load, decreasing air-conditioning equipment capacity, saving air-conditioning device investment and operation cost. It can save the fourteen to fifty percent of the total energy.In this dissertation, one hall is taken as a research object. Based on computational fluid dynamics and heat transfer, physical and mathematical models have been built up after analysis, abstract and simplification of the hall. FLUENT, the commercial computational fluid dynamics software is used to simulate the three-dimension distribution of temperature and velocity in the hall. The k-εturbulence model modified by buoyancy was used to solve equations. The SIMPLE scheme was used for numerical discretization. When dealing with the boundary condition in the area near the wall, the wall function is adopted. After numerical solution of velocity and temperature distribution in the hall space obtained, the result of numerical simulation can be visualizated by post-processing module of FLUENT and TECPLOCT software. Distribution of temperature, velocity and effective temperature difference(ΔET) value on some typical section or area can be obtained also. The result of numerical simulation related is tested by practical measure. When air distribution evaluated, air diffusion performance index(ADPI) is regarded as the most important index, and non-uniform coefficient of Temperature and velocity distribution as auxiliary indexes.When numerical simulating, velocity, temperature andΔET distribution of designed working condition are calculated at first, then the air flow is evaluated, and designed working condition is taken as reference condition, when supplying air velocity, temperature, height and air inlet type chang, how air flow numerical simulation affect on air flow distribution and evaluation index is analysized respectively. When the affection of air inlet type on air flow distribution and evaluation index is studied, air supplying cooling load in unit time from inlet is set to constant, and air inlet type is changed, affection on air flow distribution and evaluation index is discussed individually in the condition of air supplying velocity is unchanged while supply air temperature difference is changed and air supplying velocity is changed while supply air temperature difference is unchanged. Conclusions of the dissertation are as following: with air supplying velocity increasing, supplying air cooling load in unit time is increasing, and average velocity of occupant zone decreasing, velocity non-uniform coefficient are increasing, average temperature, temperature non-uniform coefficient and averageΔET value are decreasing. With supplying air temperature difference increasing, average velocity of occupant zone is decreasing; velocity non-uniform coefficient is increasing, average temperature decreasing, temperature non-uniform coefficient increasing, averageΔET value are decreasing. At the range of a certain height, with air supplying height increasing, main body of jet flow moves upword, and average velocity, velocity non-uniform coefficient of occupant zone, average temperature and temperature non-uniform coefficient are decreasing, and averageΔET is increasing. When the cooling load in unit time and temperature difference of supplying air are unchanged, with the height of supplying air inlet increasing, air supplying velocity and average velocity in occupant zone are decreasing, the velocity non-uniform coefficient and averageΔET value are increasing, the temperature remains unchanged. When the cooling load in unit time and air supplying velocity is unchanged, with the height of supplying air inlet increasing, air supplying volume and average velocity of occupant zone are increasing, velocity non-uniform coefficient, air supplying temperature difference and averageΔET are decreasing, temperature remains unchanged. ADPI value is related toΔET value in occupant zone. After those analysis above and evaluation indexes comprehensively balanced., designed working condition is considered suitable for the air-condition system. And from discussion above, some meaningful conclusion that guide the running, design and modification of stratified air-conditioning is drawn.