Study On Characteristics Of Steam Generation System Of Trough Solar Cavity Absorber

The parabolic trough solar collector is occupying the dominant position in the mid-high temperature solar heat utilization. Application of parabolic trough solar collector to replace traditional energy generated mid-high temperature steam for industrial and domestic demand, is a hot topic of research in solar heat utilization. The traditional glass-metal heat pipe of high efficiency and low heat loss, but its fragile and expensive greatly limits the development of parabolic trough solar collector. Therefore this paper presents a new absorber for generating middle-high temperature steam.In this paper, V type cavity absorber of parabolic trough solar collector for direct steam generation system was designed and built. And focus on researched and discussed the concentrating characteristics of concentrator, as well as the influence of various factors on the performance of it; internal flow characteristics, heat transfer characteristics, external heat collection, heat loss characteristics of the cavity absorber; the heat efficiency of the steam generation system, the influence of external objective factors. The concrete research content is as follows:1. With the help of Origin, basic geometrical optics theory and linear sun models to analyze the influence of energy flux of focal plane with the thickness of the glass, and compare the results of the simulation with TracePro. Calculation and simulation results show that the thickness of glass to deflect the sun’s rays have a great effect, resulting in decreased the energy flux of the focal plane. This paper presents a cold bend forming 2 mm thick semi-tempered glass reflector, modeling analysis the surface shape error and installation error, the energy flow distribution and optical efficiency of the focus plane.2. Uses the 2 mm thick cold bending forming glass reflector, sun light modeld and the incident light radiation is 850W/m2, the optics efficiency of the absorber in the focal distance place is 80.2%, the average energy flux is 13184W/m2.but actually, the energy flux distribution of the V-receiving surface assumes the M shape,the light mainly gathers in underneath the both sides of the absorber receiving surface, the energy flux peak value achieves 25000W/m2, the energy flux of middle area is minimum and its minimum valueis 1000W/m2. With the focus offset negative increase, the optical efficiency and energy flux of receiving surface of absorber increases gradually, focal offset is-6 mm maximum,with optical efficiency is 81.15%, the energy flux of 13388W/m2 current density; With the increase of focus offset optical efficiency decreases.3. Theory analysis on internal pipe flow and heat transfer of single-phase and two-phase of cavity absorber, the establishment of thermal equilibrium model and thermal network and heat loss model and Nusselt number obtained under different inclination of cavity absorber. The angle of incidence of sunlight and cosine loss and end loss significantly affected by seasonal changes.4. This paper established V-type cavity absorber of parabolic trough solar collectors direct generation steam system, experimental study that the impact of seasonal changes and irradiance changes and wind speed and mirror cleanliness and other objective factors on system performance. Research shows that the thermal efficiency in April is highest,in December is the lowest; direct irradiance below 450W/m2 the system unable to produce steam, is 850W/m2 has the highest efficiency. The actual heat loss of cavity absorber is larger than the theoretical value, the effects of the heat preservation layer directly restricts the heat loss of the absorber. Compared with the vacuum tube the overall efficiency of cavity absorber is lower than 4%.