A Review Study on Modifying Vortex Generators to Improve Thermal Performance in Single- and Two-Phase Flow in Circular Tubes

The literature about various modifications to the vortex generators as passive techniques and some combined techniques was discussed numerically and experimentally. In general, all vortex generators have a good coefficient of thermal performance compared to a plain tube. Most vortex generators don’t consume any amount of energy to perform their function, so can be considered a good tool to enhance the thermal performance coefficient in industrial applications, but they have the disadvantage of high pressure drop. When using vortex generators in two phase flow accelerated the process of transition between phases pattern in addition to increasing heat transfer. The inserted twisted tapes have a low pressure drop and good heat transfer efficiency, resulting in a thermal performance factor of 1.6.In addition, the easier to manufacture where can be changed in size and shape in proportion to the place of use inside the tubes also having a low cost, and do not consume any amount of energy to perform its function, the hybrid methods can be used with it, such as a twisted tape with nonfluids, which had proven effective in thermal performance coefficients, but their disadvantages include the high cost and risk of dealing with these materials ,bubble injectors can also be used, despite the fact that they require energy to operate. So, the twisted tapes inserted can be considered a best tool to be used in enhancing the thermal performance coefficient in various Industrial fields.Based on the reviewed literature, it was determined that the following research is limited and could garner more attention in the future: multiple coaxial cross-twisted tapes with different perforations, and twisted tapes with variable cross-section, typical twisted tapes with regular wavy edge, hybrid methods such as nanofluids and twisted tape can be used in multiphase flow.