【作者】 张文武；

【导师】 刘京；

【作者基本信息】 哈尔滨工业大学 ， 供热、供燃气、通风及空调工程， 2008， 硕士

【摘要】 城市不透水表面长时间暴露在随时间不断随机变化的环境条件下,与大气之间的对流换热过程受到室外温度、相对湿度、风速、风向以及太阳辐射等各种因素的影响,是一个复杂的动态过程,从而使得城市不透水表面对流换热系数难以准确测量或推算得到。到目前为止建筑墙体外表面对流换热系数还没有得到系统的研究。对于这样的一个重要领域,目前国内外关于对流换热方面的实测数据严重缺乏,在现有的空调负荷计算方法中,一直采用经验值,且取值各异,更没有较好的确定方法,从而给建筑热工、室内采暖空调负荷、建筑能耗分析及计算带来很大的误差。研究表明,表面对流换热系数15%的不确定量可以导致建筑围护结构预测热流15～20%的不确定量。针对传统实测方法设备复杂、精度难于把握,而模型实验又缺乏相似性的问题,本课题在前人工作的基础上,以热质比拟基本原理为基础,针对室外环境特点,开发出适用于城市不透水表面对流换热的萘升华技术,使该技术可以在室外环境中应用。通过热平衡法与萘升华技术法对建筑外水平表面同时进行实测研究,来验证萘升华技术法的可靠性和准确性。在萘升华技术法的可靠性和准确性得到保证后,利用该技术对建筑群外表面、城市街道路面进行多点的室外实测,来考察表面形状与尺寸、测点空间位置、建筑高度与密度、风速、风向及温差等因素对对流换热的影响。以传热学边界层湍流对流换热理论为理论基础,利用实测数据建立城市不透水表面对流换热的数学模型。通过CFD计算模型的耦合计算,研究在不同的建筑工况及气象条件下建筑外表面对流换热系数、对流换热量及建筑墙体传热量的静态分布规律。本课题以建筑热工学、传热学相关理论为基础,研究城市不透水表面的对流换热特性,在城市气候学研究中具有创新意义。为准确预测建筑负荷、研究城市冠层内的热动力特性,解决城市高温化和热岛效应等城市热气候问题提供理论依据。更多还原

【Abstract】 The urban waterproof surface exposes to the condition which changes continuously and randomly with time. The convective heat transfer with the atmosphere eache other influenced by the outdoor temperature, relative humidity, wind speed, wind direction, solar radiation and so on is an intricate and dynamic process. So it is difficult to measure or calculate the convective heat transfer coefficient of the urban waterproof surface correctly. So far the convective heat transfer coefficient of the building wall’s exterior surface has not been studied systematically. There is a serious lack of the test data about the convective heat transfer in this important domain. The experience value has been using in the existing calculation method of the air conditioning load, and that values obtained are different, and what’s more, there is not a good determinate method at present, which brings big error to the building thermal technique, indoor heating and air-conditioning load and building energy consumption analysis and calculation. The results show that 15% indefinite quantities of convective heat transfer on the surface can lead to 15～20% indefinite quantities of building envelopes when estimating heat flux.There are many disadvantages in the traditional experiment method. For instance, equipments are too complex. It is difficult to control the precision, and there is lack of comparability in model experiments. So based on previous researches, this paper gives out a new method of researching on convective heat transfer coefficient of the urban waterproof surface by naphthalene sublimation. It uses the heat-mass transfer analogy method in view of outdoor environment characteristics, and makes this technology possible to be applied in the outdoor environment. Field experimental study has been done in building’s horizontal roof by heat balance method and heat and mass transfer analogy method. It also verifies the reliability and accuracy of naphthalene sublimation technique. After that, multi-point measurements are done in building group’s external surfaces and city’s road surfaces using this method. Then we can know how the following factors influence the convective heat transfer. These factors include the shape and size on surfaces, measuring points’spatial location, height and density of buildings, wind speed, wind direction, temperature difference and so on. Based on the boundary layer turbulence convective heat transfer theory in heat transfer, we establish the mathematical model of convective heat transfer on the urban waterproof surface. Then the computational model in CFD is used to calculate by coupling method. The static distribution law of the convective heat transfer flux, convective heat transfer coefficient and wall’s heat transfer flux on the surface of building is studied under different building location and meteorological conditions through coupling method in CFD.Based on some theory in the building thermal technology and heat transfer, this paper studies convective heat transfer characteristic. This result has an innovative significance on urban climatology’s researches. It also provides the theory basis for the research on the problems which are caused by urban warm climate, such as previewing building load accurately, studying the urban canopy’s thermodynamic characteristics and solving urban heat island effect.更多还原