Thermal augmentation in parabolic trough collector solar water heater using rings attached twisted tapes

Many techniques have been implemented to improve the thermal performance of solar water heating systems. Among that, Twisted tapes is one of the effective heat transfer enhancement technique. Experiment was conducted for empty tube, conventional twisted tape, Rings attached twisted tape and modified Rings attached twisted tape. Rings attached twisted tapes shows higher heat transfer rate than empty tube and conventional twisted tapes condition but it also augment the pressure drop. So modifications were made in the Rings attached twisted tapes by increasing its twist ratio and centre cut. Results were improved with this modification. (C) 2019 Elsevier Ltd. All rights reserved.