【作者】 雷进波；

【导师】 钟建立；

【作者基本信息】 浙江大学 ， 农业机械化工程， 2004， 硕士

【摘要】 本文利用FLUENT计算和实验相结合，揭示了全玻璃太阳能真空集热管测试状态下的流场和温度场的规律，分析了太阳能真空集热管流场和温度场的影响因素，对结构设计和国家检测标准做出了评价。主要研究内容和研究成果如下： 1．根据太阳能真空集热管的物理模型和FLUENT的建模要求，建立了太阳能真空集热管的FLUENT计算模型，根据太阳能真空集热管在闷晒、空晒和散热状态下的工作条件，设置FLUENT计算的边界条件，对三种工况下的流场和温度场进行计算，计算结果与实验测试结果非常吻合； 2．通过FLUENT计算，清楚地观察到太阳能真空集热管壁面和中心部分，顶部、中部和底部在各种工况下的流场分布均不相同；得出了各种工况下的温度-时间变化曲线，沿轴线方向的温度梯度；同时还计算了各部分热损的传热流量； 3．分析了各种因素对太阳能真空集热管流场和温度场的影响。直径越大，热效率越高，但升温能力弱；长度对热效率影响不大；倾斜角度大于30°后，自然对流已经能够充分进行，考虑以能够吸收到最大太阳辐射为主；真空度和发射率对热效率和温度场影响很大，尤其是在介质温度与环境温度差异比较大时；水垢对传热影响较小但由于水质的问题应该被3～5年清洗一次；太阳辐射强度越大，介质温度与环境温度差异越大，热损失越大，效率越低； 4．对太阳能真空集热管的国家检测标准做出了评价。用空晒性能参数和闷晒性能参数来评价太阳能真空集热管的好坏即可，取消平均热损系数指标，空晒性能参数反映高温能力，闷晒性能参数反映正常工作时的升温能力。两者用统一的指标和测试条件来计算，规定初始温度和测试时间，规定一定范围的太阳辐照度和环境温度，用温度升高值除以辐照强度得到评价值。 5.对太阳能真空集热管结构设计优化.在不影响安装和增加成本的情况下，应适当增加太阳能真空集热管的长度;根据当地的气候条件和使用要求来综合考虑选择直径;国标规定的真空度必须达到5 x10’zPa，发射率小于0.1是合理的;弹簧卡子不要选用很宽、很大的尺寸，尽量减少接触热损;吸气剂并非越多越好，只要能够吸收残余气体，保证一定的真空度即可。更多还原

【Abstract】 The article discloses the principle of all-glass evacuated solar collector tube’ flow field and temperature field in the testing state, analyzes the influence of many factors, makes the estimation of Mechanical design and testing standards. The following is the major content and study results:1. Build the compute model of all-glass evacuated solar collector tube in FLUENT according to the physical model and the interface of FLUENT, Set the boundary conditions on the basis of the fact of three different states of air stagnation, water stagnation and heat loss. The calculation results have a good match with the test results.2. In FLUENT, the flow field of the tube wall, center, top, middle and bottom of the evacuated solar collector tube can be observed, the temperature-time curve and radial temperature gradient can be obtained, the heat loss of different part can be directly captured.3. All kinds of effect factors of the flow field and temperature field have been analyzed. The bigger the diameter, the high the heat efficiency, but the weak the temperature increasing ability, length has less effect on the heat efficiency, tilt angle has less effect on the flow field and temperature field while it is larger than 30 degree, vacuum degree and emissivity have great effect on the flow field and temperature field while there is a great temperature difference between the liquid in the tube and the surroundings, the furring has less effect on the heat transfer but should be cleaned up in 3-5 years because of poor water quality, The higher the solar flux or the more the temperature difference between the liquid and the surrounding, the more the heat loss and the lower the heat efficiency.4. The inspection standard has been appraised. The air stagnation parameter and water stagnation parameter are enough to evaluate the quality of evacuated solar tube and the heat loss co-efficiency can be cancelled. The parameter should be united into the ratio of the radiance flux and the temperature difference between the liquid (water or air) and the surrounding under the definite imitative temperature, test time and reasonable radiance flux range, surrounding temperature range.5. The design of solar evacuated tube can be optimized. The length shouldbe added if the cost isn’t increased and the installation is convenient, the diameter should be chose by the local weather condition and the using requirement; the gas pressure should be not higher than 5 X 10-2Pa and the emissivity should be less than 0.1, the spring should be small and narrow in order to decrease the heat loss, the gas absorbed getter should not be too many as long as it can absorb the residual gas and keep the vacuum degree.更多还原