INVESTIGATION OF HEAT LOSSES FROM THE TRAPEZOIDAL CAVITY RECEIVER FOR LINEAR FRESNEL REFLECTOR SOLAR POWER SYSTEM

摘要

Medium and high temperature heat can be produced by using concentrating solar power (CSP) technologies. Among CSP technologies, linear Fresnel reflector (LFR) system is simple in design and cost effective technology for medium temperature (400 °C) applications. In this article, the numerical investigation of the receiver for LFR system is carried out to estimate the combined convective and radiative heat losses. The 2-D numerical simulation of trapezoidal cavity receiver is carried out using commercial CFD package, Fluent - 6.3. The cavity receiver surface absorbs maximum amount of reflected solar radiation with minimum heat losses. At steady state conditions, the cavity receiver surface will attain almost uniform temperature; therefore, an isothermal boundary condition and also Boussinesq approximation are considered in the numerical simulations. To account the radiation exchange between the surfaces, the surface-to-surface model is used. The heat loss analyses are carried out for various receiver geometric and operating parameters viz. aspect ratio (ratio of receiver aperture to receiver width), cavity depth and width, operating temperature and wind speed. Based on the numerical analysis of the receiver, an optimum configuration of the receiver is found at insulation thickness of 300 mm, cavity depth of 300 mm with an aspect ratio of 2. The total heat loss varies from 614.32 W/m to 968.8 W/m for absorber width of 300 mm to 800 mm at 500 °C receiver temperature, 0.5 cavity cover emissivity and 2.5 m/s wind velocity. The effect of cavity cover emissivity on total heat loss is found to be less significant when compared to that of other cavity parameters. The optimum configuration of the inverted trapezoidal cavity receiver is arrived based on the heat loss analysis of the receiver.