查看更多>>摘要：Processes of steam condensation in the presence of air, as non-condensable gas, was studied in experiments with the models of plate heat exchanger (PHE) channels formed by plates with corrugations of different geometry. Validity of the developed mathematical model for the calculation of local process parameters is confirmed, and it is used to facilitate the analysis of experimental results. Sets of experiments were performed on five samples modelling PHE channel main corrugated field. The corrugations angle to plate vertical axis in three experimental samples was 30 degrees, 45 degrees and 60 degrees at the same corrugations' height of 5 mm. Another two samples had corrugations height 7.5 mm and 10 mm at the same corrugations angle 60 degrees. Various effects of plate sizes and geometrical parameters of corrugations on the performance of PHE as a condenser for steam-air mixture and local process parameters profiles are discussed. Presented analysis shows that the specified process conditions on temperature and pressure drop in PHE can be satisfied by varying corrugations angle and channel spacing at plates of different lengths. To maintain the same temperature program with a decrease of plates corrugation angle from 60 degrees to 30 degrees require the plates with a length bigger from 2 to 2.6 times, depending on specific process conditions. These plate parameters are recommended for use as variables in solving the problem of PHE plate geometry optimisation with the use of the proposed mathematical model.
查看更多>>摘要：Thermal contact resistances are detrimental to the heat transfer of a radiant cooling panel with the pipe-plate structure, thereby reducing its cooling capacity. Therefore, the pipe-plate structure of traditional radiant cooling panels is reconsidered in this study. Being analogous to the structures of liquid cooling plates, the radiant cooling panels with integrated flow channels are constructed. The effects of panel materials, flow channels, and dimensions on the thermal and hydraulic performance of the reconstructed radiant cooling panels are detailedly discussed based on numerical calculations. The relationship between temperature uniformity, cooling capacity, and condensation prevention of radiant cooling panels is described. The numerical results show that the inlet temperature of cold water of the restructured radiant cooling panels can be increased by about 4 degrees C compared to that of a traditional one with the pipe-plate structure when the same 80.1 W/m2 cooling capacity is provided. This study is conducive to a better understanding of radiant cooling panels.
查看更多>>摘要：In this study, a thermal model of sintering Polytetrafluoroethylene (PTFE) billet was established. Temperature, which determines the success of the sintering process, was predicted and validated by experiments with less than a 2% error rate. The maximum tensile stress could be increased from 27.9 to 31.6 MPa, and average elongation was also enhanced from 444.12% to 525.27% under controlled crystallization temperature; besides, the tensile stress on the specimen was uniform. Effects of height and diameter ratio on gradient temperature, which reflect on residual stress, were considered, and control temperature and holding time for crystallization were also analyzed. The results reveal that the thermal model can be used for quickly determining appropriate parameters for the sintering process.
NSTL
Elsevier