The Study Of The Flow Field And Temperature Field In The All-glass Evacuated Solar Collector Tube

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.