Effect of Scaling on Energy Efficiency of Solar Flat Plate Water Heaters

摘要

Component malfunctioning and system performance degradation in solar water heaters due to scaling are common in areas where hard water is used. Scaling effects on energy efficiency indicators like pressure drop, overall heat loss coefficient, instantaneous efficiency and annual efficiency are quantified by the Hottel-Whillier-Bliss (H-W-B) equation in case of thermosyphon and forced circulation systems. The effects of mass flow and heat transfer rate for both the thermosyphon and forced circulation systems are quantified. It is seen that scaling altered mass flow rate affects energy efficiency much more than scaling altered heat transfer rate. However, the effect due to scaling is more dominant in case of thermosyphon system. The effect of scaling has been simulated through the perceived uniform reduction in the flow area of the risers.