【作者】 于俊；

【导师】 徐玉党；

【作者基本信息】 华中科技大学 ， 供热、供燃气、通风及空调工程， 2007， 硕士

【摘要】 随着国民经济持续、稳定、高速的发展和人民生活水平的不断提高,冬天需要热源、夏天需要冷源的空调技术使用愈来愈普遍。空调的广泛使用加大了对电力的需求,也是造成电网峰谷负荷差的主要原因之一,电力供应高峰不足而低谷过剩的矛盾随着经济和社会的发展而日益突出。把蓄冷技术应用到家用空调器等小型空调设备上,它们所起到的移峰填谷作用将是很可观的,有着很大的经济效益和社会效益。在小型冰蓄冷空调系统中,两器(蒸发器与冷凝器)是主要的热交换设备,其中,蓄冰槽又是系统中的关键设备,它的结构直接影响到空调系统的工作效率。前人已经将直管和螺旋管进行了比较分析,结果表明:螺旋管是一种有效的传热强化管,换热性能优于直管;结构紧凑,在单位空间内可布置更大的换热面积。螺旋管内两相流除两相流本身的复杂性外,由于受离心力和扭转力的作用,比直管中的流动要复杂得多。本文在理论分析的指导下,利用数值模拟方法,对水平螺旋盘管内制冷剂R134a的饱和沸腾进行了三维数值模拟。在热流密度一定的条件下,对不同的流动形式(曲率半径与螺旋管径的比值Dc/D)及不同的质量流量下流体的换热系数进行比较计算,并分析了沿流动方向气体含气率、流体温度、流体流速的变化规律。计算结果与理论分析的结果吻合较好。可为以后研究两相流动的饱和沸腾换热传热的研究及小型冰蓄冷空调蓄冰槽中蒸发管的设计提供参考。更多还原

【Abstract】 With the sustaining, steady, high-speed development of national economy and the improvement of the living standard, it is popular to utilize air conditioner to supply heat in winter and cool in summer. The widely usage of AC which aggravate the burden of power grid is a main cause of the load difference between on-peaks and off-peaks. So, the contradiction between power supply on-peaks and off-peaks becomes increasingly prominent with the economic and social development. However, the application of cool storage technology in small-sized air conditioner, such as residential, will play a considerable role in economic and social benefits.The evaporator and condenser are the main heat exchange devices in small-sized cool storage air conditioning. Ice container whose frame will affect the performance coefficient of air conditioner greatly is the key facility thereof. Some comparative experiments between straight tubes and helical tubes have been taken. It indicates that helical tube is a kind of more effective enhanced heat exchanger than straight tube. Besides, more heat exchange area can be disposed in constant space because of the compact framework. The two-phase flow is very complicated not only for the complication of itself, but also the effects of centrifugal force and torsion torque.Based on the theory guidance, this paper presents a three-dimensional model for the saturated boiling flow of R134a in a helically coiled tube using the numerical simulation. In the condition of constant heat flux, I made a comparative computation of heat exchange coefficient in different flow forms and mass flow rates. In addition, it presents the analysis on the transformation rules of vapor volume fraction, fluid temperature and fluid velocity. The results are well closed to the theory analysis. Therefore, the results can be used as a reference both for the two-phase flow research on boiling heat transfer and the design for evaporating tubes within small-sized ice storage air conditioners.更多还原