Optimising the thickness of the water layer in a triangle solar thermal collector

Novel triangle solar thermal collectors with colored absorbers were developed to improve the solar thermal facades architectural acceptance. Besides their nonconventional shape and colors, the collectors have an internal cavity instead of pipes to support the water flow. After indoor testing in standard conditions (water, 0.001 kg/s, 1000 W/m(2)) the collectors showed color dependent nominal efficiencies ranging between 35 and 55%. To improve this efficiency, an optimization process is developed based on CFD simulations considering the mass flow rate and the thickness of the water layer as parameters. Thus, 3D models of the triangle collector with 20,10 and 5 mm water layer thicknesses were prototyped using SolidWorks and transferred in Ansys Fluent where CFD simulations were performed. For each thickness, mass flow rates within the range 0.0005 ... 0.05 kg/s were considered. The simulation model is experimentally validated on a collector having a water layer thickness of 20 mm in standard testing conditions. The simulation results show how the nominal efficiency can be increased from 55.74%, obtained for a standard mass flow rate and 20 mm water layer thickness, up to 66.12% for 0.01 kg/s mass flow rate and 5 mm water layer thickness. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Novel triangle solar thermal collectors with colored absorbers were developed to improve architectural acceptance. An optimization process based on CFD simulations was used to increase efficiency, demonstrating potential ways to enhance nominal efficiency.