Effect of Perforated Tube Insert on Thermal Behavior of Flat-Plate Solar Water Collector

Abstract

AbstractThe thermal output of the flat-plate solar water collector (FPSWC) is lower owing to higher heat loss and poor heat removal by the heat transfer fluid. Converting a laminar into a turbulent flow does not require a significant investment than other methods which need to study further for higher thermal output. In this work, the contribution of perforated and plain tube inserts to improving the thermal output of FPSWC is studied and compared with plain riser tubes at 0.0167 kg/s. The perforation provided along the tube insert improved the fluid mixing between hot and cold fluid zones and enhanced the heat transfer coefficient (HTC). Further, the tube inserts act as extended heat surfaces by their frictional contact at the top and bottom inside the riser tube. The collector’s maximum and average instantaneous thermal efficiencies are 78.4 and 57.7% with a perforated insert, where the average thermal efficiency is 40 and 15.9% higher than using a collector with plain riser tubes and with plain tube inserts. The exergy efficiencies of the collector with perforated tube insert, plain tube insert, and without inserts are 3.9%, 3.3%, and 2.5%, respectively. The average exergy efficiency of a perforated inserted absorber is 31.25 and 90.9% higher than the collector with plain tube inserts and without the insert. The convective HTC has reached a maximum of 5.79 W/m2 K for the perforated insert, which is higher than the other two collectors.KeywordsSolar collectorHeat transferEnergy efficiencyFlow insertHeat transfer coefficient