Nonuniform heat transfer model and performance of parabolic trough solar receiver

The nonuniform heat transfer model and performance of parabolic trough solar receiver are theoretically investigated due to the energy balances between the heat transfer fluid, absorber tube, glass envelope and surroundings. The absorber tube and glass envelope are both divided into two regions for uneven solar radiation and wall temperature distribution, and then a nonuniform heat transfer model of solar receiver is established. According to the calculation results, the heat loss of solar receiver from the nonuniform model is a little higher than that from the uniform model, and the heat transfer inside the vacuum glass envelope is mainly dependent upon the radiation, while the convection and radiation both play important roles in the heat loss outside the glass envelope. Under offsun condition, the heat transfer of receiver is almost uniform with little differences of wall temperature and heat loss. Under onsun condition, the heat transfer of receiver is apparently nonuniform for higher wall temperature and heat loss in the positive region of glass envelope and absorber tube. As a conclusion, the heat transfer performances of parabolic trough solar receiver are better to be calculated by nonuniform model especially under onsun condition. (C) 2013 Elsevier Ltd. All rights reserved.