Thermal-Hydraulic Investigation of the Delta–Nabla Channel Arrangement in a Solar Collector

Abstract A novel solar collector consisting of a delta–nabla configuration of flow channels is investigated in the present study. In the proposed design, triangular channels connected in series act as an absorber having more exposed area to the sunlight with an ability to store 21 L of water inside it that serves as a sensible energy storage to mitigate the intermittency issues. At the stage of proof of concept, the effectiveness of the novel collector design is not known. Moreover, its performance comparison with the existing solar thermal collector configurations is yet to be explored. Hence, there is a need to develop a comprehensive numerical model that can be used as a design template to predict the performance of the proposed collector configuration in a range of climatic conditions. Therefore, the present study is an attempt to investigate the thermal-hydraulic performance of the proposed collector, and transient numerical simulations are conducted. For accurate prediction, the effects of flowrate, inlet temperature, and irradiative flux on the outlet temperature are analyzed through a parametric study using the real-time data of ambient temperature and solar irradiative flux. The results of the numerical study are used to calculate the derived parameters such as Nusselt number, heat losses, and collector thermal efficiency by varying the water flowrate. The study shows that the heat transfer characteristics increase with an increase in flowrate and the collector can operate up to overall efficiencies between 29% and 62% at flowrates ranging from 0.1 to 0.8 L/min in winter. Moreover, the numerical model has predicted improved thermal performance of the proposed delta–nabla configurations when compared with a conventional solar collector design.