Abstract
The flow through a forced circulation Z-type flat plate solar collector was investigated by means of combined experimental measurements and numerical simulations. The efficient operation of such collectors depends on the uniformity of the flow rate distribution among their riser tubes, while low pumping power demand is also sought. Mass flow rate measurements in the riser tubes were performed, utilizing a specially adapted ultrasound instrument for various values of total flow rates in the collector. By means of a commercial Computational Fluid Dynamics (CFD) code, laminar and turbulent flow models in different computational grids were tested and validated against the experiments. Appropriate metrics were introduced to quantify flow rate distribution non-uniformity among the risers, and pressure drop through the manifold was calculated. Parametric studies for flow conditions outside the experimental window were performed utilizing the CFD method in order to assess the effect of the Reynolds number in the flow distribution among the riser tubes. Furthermore, aiming to enhance flow rate uniformity, a methodology based on modifying the diameter of each riser tube was applied and successfully demonstrated. The proposed method can be employed in large solar collector arrays, either as stand-alone systems or as belonging to hybrid alternative sources of energy (ASE) systems, aiming to optimize their overall efficiency.
Highlights
The household sector accounts for about 25% of final energy consumption or 17.4% of gross inland energy consumption in the European Union EU, making it one of the largest contributors of GreenHouse Gas (GHG) emissions in the atmosphere
Simple thermosyphon-type systems employing naturally driven fluid circulation are used for water heating, while larger systems employing forced circulation are used for both water and space heating
In light of the above, the present paper presents a study of the flow characteristics in the manifold manifold ofsolar a Z-type solarBoth collector
Summary
The household sector accounts for about 25% of final energy consumption or 17.4% of gross inland energy consumption in the European Union EU, making it one of the largest contributors of Green. In light of the above, the present paper presents a study of the flow characteristics in the manifold manifold ofsolar a Z-type solarBoth collector Both experimental measurements and simulations numerical simulations of a Z-type collector. The basis for the selection of the cases examined in the present study is the ISO 9806:2017 standard [11], which is currently the standard followed by certification laboratories for the testing of solar thermal collectors According to the latter, the recommendation for pressure drop measurements is to perform them over a range of flow rates from 0.005 kg/s to 0.03 kg/s per square meter of collector gross area.
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