Effects of Design Parameters on the Fluid Flow and the Efficiency of Single Ended Evacuated Tubular Solar Thermal Collectors via FEM Modelling and Experimentation
Keywords:Tubular solar thermal collector, thermosyphon, solar heater efficiency, COMSOL simulation.
This work is about assessment of the single-ended evacuated tubular solar thermal collectors which are widely used in solar heating applications. Exchange and transfer of heat are accomplished by a thermosyphon process. The flow pattern of the working fluid within the collector is determined by a combination of gravity forces and the fluid's buoyancy forces which are due to varying density at varying temperature. This paper reports on a finite element method (FEM) based numerical study of the dependence of the working fluid flow pattern on the collector's design parameters such as inclination angles and collector length-to-diameter ratio. This fluid flow pattern determines the heat exchange between the working fluid and the selective coating and thus the efficiency of the collector. A model of this process has been implemented in a simulator built via COMSOL FEM software package. A physical solar water heating system made with five commercial evacuated tubular collectors was also built and tested to verify the simulation results. Public access to the simulator is provided here.
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