Thermal-hydraulic performance analysis of a novel parabolic trough receiver with double tube for solar cascade heat collection

Abstract

The utilization of solar energy is of great significance to alleviate energy shortage and environmental problems. In view of the different thermal grade requirements of electricity production and water desalination in remote arid areas as well as to improve the performance of the parabolic trough receiver (PTR), a novel solar cascade heat collection system based on a PTR with double tube and two heat transfer fluids (HTF) is proposed in this paper. A three-dimensional model is developed to simulate and investigate the temperature distribution, heat transfer and flow characteristics and heat collecting performance of the novel system. Moreover, the effects of the operating parameters on the performance are studied in details. The temperatures of the absorber tube are significantly reduced over the plain PTR, and the heat transfer coefficient on the absorber inner surface is enhanced about 50% with 2.5–6.8 times increment in total pumping work. In addition, the heat loss reduced up to 43.1%, thus, the maximum improvement of the total thermal efficiency reaches up to 1.5%. Within the parameters considered in this study, the proportions of the high and low temperature heat gains are ranged in 39.01–62.92% and 28.37–8.86% of the incident solar energy, respectively.