Experimental and economic analysis of concrete absorber collector solar water heater with use of dimpled tube

To increase the usage of solar water heaters in India, a low-cost solar collector made of concrete is exper- imentally investigated in Pune. The concrete slab consisting metal fibers is placed in a wooden box, with immersed serpentine copper tube and provided with glazing on top. With an objective of improving the efficiency of the collector, a heat transfer augmentation technique (dimple) is fabricated on water carry- ing serpentine tube. Testing is carried out in rainy, winter and summer seasons for different water flow rates to understand the working of collector throughout the year. Testing results show that average water temperature collected per day is 59 °C–69 °C. Further, to find the exact effect of dimples on outlet water temperature, two completely identical concrete plate collectors–one with a dimpled tube and other with a smooth tube, are designed, fabricated and tested simultaneously. The effect of dimples is observed up to 2.5 °C. Also, a detailed economic analysis and environmental benefits of concrete collector solar water heater for India are investigated in this paper.