Analysis of heat transfer performance of the absorber tube with convergent-divergent structure for parabolic trough collector

In order to effectually improve the performance of parabolic trough solar collector system and homogenize the temperature distribution on the absorber tube, an innovative convergent-divergent tube was designed as the absorber tube of PTR. The finite volume method (FVM) and the Monte Carlo ray tracing method (MCRT) are combined to simulate the heat transfer process in parabolic trough collector. The average relative error between the numerical results and the experimental results conducted in the Spanish DISS test facility is 1.103%, which confirms the reliability of the simulation results in this paper. The heat transfer characteristics and flow characteristics of PTR and convergent-divergent PTR are compared in the inlet velocity range of 0.05-0.75m/s, and the effect of the number of zoom sections(N) for CD-PTR performance is also studied. The simulation results show that the parabolic trough collector with convergent-divergent tube has significantly enhanced heat transfer capability. The average Nu of CD-PTR increases as the number of zoom sections increases, and is always higher than that of PTR. When Re=86400 and N=25, the average Nu increased by 66%.