Ray-Thermal-Structural Coupled Analysis of Parabolic Trough Solar Collector System

Abstract

An effective approach to sustainable energy is the utilization of solar energy. The parabolic trough collector with central receiver is one of the most suitable systems for solar power generation. A type of concentrating solar collector that uses U-shaped troughs to concentrate sunlight onto a receiver tube, containing a working fluid such as water or oil, which is positioned along the focal line of the trough. Sometimes a transparent glass tube envelops the receiver tube to reduce heat loss. Parabolic troughs often use single-axis or dual-axis tracking. Temperatures at the receiver can reach 400°C. The heated working fluid may be used for medium temperature space or process heat, or to operate a steam turbine for power or electricity generation. As designed to operate with concentrated heat fluxes, the receiver will be subjected to the high thermal stresses which may cause the failure of receivers. The thermal stress of receiver or tube heat exchangers has drawn many researchers’ attention. Numerous studies have been carried out to investigate the temperature distributions and thermal stress fields of receiver or tube heat exchangers. A numerical analysis had been conducted by Chen [1] to study the effect on temperature distributions of using porous material for the receiver. Experiments were conducted by Fend [2] to research the temperature distributions on the volumetric receivers used two novel porous materials. A finite element analysis was conducted by Islamoglu [3] to study the temperature distribution and the thermal stress fields on the tube heat exchanger using the SiC material. To reduce the thermal stresses, Agrafiotis [4] employed porous monolithic multi-channeled SiC honeycombs as the material for an open volumetric receiver. Low cycle fatigue test of the receiver materials was conducted at different temperatures by Lata et al. [5], the results showed that the high nickel alloys had excellent thermo-mechanical properties compared to the austenitic stainless steel. Almanza and Flores [6, 7] proposed a bimetallic Cu-Fe type receiver, and the experimental test results showed that, when operated at low pressure, the bimetallic Cu-Fe type receiver had a lower thermal gradient and less thermal stress strain than the steel receiver. In Steven’s study [8], the receiver is divided into 16 sections, and the average solar radiation heat flux of each section is calculated. The average heat flux is used as boundary condition for each corresponding section in the thermal analysis model. This method is fairly straightforward and simple, but the deviations generated during the heat flux transformation process are enormous.