局部顶送风冷射流与面源羽流相向作用下的混合对流流场特性研究

发布时间：2018-11-13 17:50

【摘要】：随着经济的快速发展,工业建筑室内污染问题日益突出。工业生产过程中散发的各种有害物以及余热余湿,使得工人的作业环境十分恶劣,严重危害操作人员的健康。局部送风是一种节能的通风方式,对于操作岗位固定的高大工业建筑,尤为适宜采用局部送风方式对工人工作区进行重点控制,可有效改善工作区的局部微环境、降低能耗。在工业建筑中,经常存在高强度热源,由热源引起的自然对流、人的热羽流以及局部送风强迫对流耦合作用下的气流规律特性尚不明晰,限制了局部送风系统在工业建筑中的应用。为了提高局部送风系统的性能、降低能耗,有待于对此混合对流的流动机理及混合对流的流动特性和热特性进行深入地研究与探讨。论文研究有高温热源时,顶送风方式下的工作区局部微环境控制。首先,研究了送风射流与面源羽流相向作用下的的混合对流流动规律。通过实验与数值模拟的方法研究了射流送风速度、送风温度,热源强度、热源尺寸,背景温度对混合对流流场的影响。发现了混合对流的流动特征:射流与羽流的“相斥”现象,即射流与羽流相互排斥并远离;射流向羽流方向偏转;在高强度羽流作用时射流失效(不能覆盖工作区)。揭示了其相应的流动机理:(1)射流较弱时,射流与羽流相向流动,在共同作用区,速度下降,压强增加;而射流与羽流另一侧,由于卷吸使得其外侧速度增加,压强降低;从而产生导致相斥流动的压强差。射流较强时,射流冲击地面后射流动量转向,进而推挤羽流。(2)射流向羽流方向偏转是由于无质量流羽流的卷吸作用。(3)射流失效是由于热源的次生辐射作用,减弱了送风射流动量,从而不能完全覆盖工作区,并给出了送风射流失效的条件Ard0.23。基于研究结果,指出了对工作区优化控制的方向。其次,人体会对混合对流流场产生重要影响。人体的存在使得送风射流发生偏转、热源羽流贴附人体,造成人体局部微环境流动特性与热特性的剧烈变化,基于数值模拟的方法研究了送风射流速度、温度,热源强度、尺寸,背景温度对人体热特性及热源特性的影响。最后,基于研究结果,采用数值模拟的方法对工作区控制的优化方向进行了验证。通过降低屋顶温度,可降低次生辐射对送风射流的影响,进而增大送风射流的有效性。通过研究得出自地面至0.45m处人体表面辐射最大,因此在热源与人体之间增设0.45m高的防辐射隔热板,可有效减小热源对人体表面的辐射得热量,并研究了降低辐射板温度对人体热特性的影响。
[Abstract]:With the rapid development of economy, indoor pollution of industrial buildings is becoming more and more serious. All kinds of harmful substances and residual heat and moisture in the industrial production process make the working environment of workers very bad and seriously endanger the health of operators. Local air supply is a kind of energy saving ventilation method. For large industrial buildings with fixed operation position, it is especially suitable to use local air supply mode to control the workers' working area, which can effectively improve the local micro-environment of the working area and reduce the energy consumption. In industrial buildings, there are often high intensity heat sources. The natural convection caused by heat sources, the characteristics of human heat plume and the characteristics of air flow under the coupling of local forced convection are not clear. The application of local air supply system in industrial buildings is limited. In order to improve the performance of local air supply system and reduce energy consumption, the flow mechanism of mixed convection, the flow characteristics and thermal characteristics of mixed convection need to be deeply studied and discussed. In this paper, the local microenvironment control of the working area with high temperature heat source is studied. Firstly, the mixed convective flow of the air jet and the surface plume is studied. The effects of jet velocity, air temperature, heat source intensity, heat source size and background temperature on the mixed flow field were studied by means of experiments and numerical simulation. The characteristics of mixed convection flow are found: the "exclusion" of jet and plume, that is, the mutual exclusion of jet and plume, the deflection of jet to the direction of feather flow, and the failure of jet (which can not cover the working area) under the action of high intensity plume. The corresponding flow mechanism is revealed as follows: (1) when the jet is weak, the velocity decreases and the pressure increases in the interaction zone, while on the other side of the jet and plume, the velocity increases and the pressure decreases due to entrainment. Thus, the pressure difference that leads to the repulsive flow is produced. When the jet is strong, the jet impinges on the ground and the ejection momentum turns to push the plume. (2) the jet deflects toward the feather stream because of the entrainment of the mass flow plume. (3) the jet failure is caused by the secondary radiation of the heat source. The flow momentum of the supply air jet is weakened, so that the working area can not be completely covered, and the condition of the failure of the supply air jet Ard0.23. is given. Based on the research results, the direction of optimal control of the working area is pointed out. Secondly, the human body will have an important effect on the mixed convection flow field. The existence of human body causes the air jet to deflect and the heat source plume to attach to the human body, resulting in drastic changes in the flow characteristics and thermal characteristics of the local microenvironment of human body. Based on the numerical simulation method, the velocity, temperature, and heat source intensity of the air jet are studied. The effect of the size and background temperature on the thermal characteristics and heat source characteristics of the human body. Finally, based on the research results, the optimization direction of the work area control is verified by numerical simulation. By reducing the roof temperature, the influence of secondary radiation on the air jet can be reduced, and the effectiveness of the air jet can be increased. From the ground to 0.45m, the maximum radiation of human body surface is obtained. Therefore, the addition of 0.45m high anti-radiation insulation board between the heat source and the human body can effectively reduce the radiation from the heat source to the human body surface. The effect of reducing the radiation plate temperature on the thermal characteristics of human body is also studied.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU83

【参考文献】