Investigation of turbulent flow of water through converge and diverge pipes with twisted tapes inserted

In most cases, convective heat transfer can normally be improved by active or passive methods. The former (active methods) utilize power external to the system to cause enhancement, whereas an external power source is not utilized by the latter. The passive method is almost centered upon the hypothesis that a decrease in the thermal boundary layer (TBL) thickness will undoubtedly create an increase in the rate of convective heat transfer. Some of the passive techniques are: geometry modification, e.g., inserting a twisted tape in the pipe, converging pipe, corrugated pipe, helically coil tube, and wavy channel. For geometry modification to increase convective heat transfer, twisted tape insert is more preferable since it possesses a relatively high thermal enhancement compared to other modified geometry designs explored so far. Following is a summary of recent research on heat transfer efficiency and EPR in twisted tape inserts for pipes.