Frontiers in Heat and Mass Transfer (FHMT), 12, 26 (2019) DOI: 10.5098/hmt.12.26 Global Digital Central ISSN: 2151-8629 1 HYDRODYNAMIC AND THERMAL PERFORMANCE OF TWISTED TAPE INSERT PROVIDED IN HEAT EXCHANGER TUBES: A REVIEW Ravi Datt a,b , Anil Kumar c , Mangal Singh Bhist d , Alok Darshan Kothiyal e , Rajesh Maithani f a Department of Applied Sciences, Chitkara University, Solan, Himachal Pradesh, 174103, India b Uttarakhand Technical University, Dehradun, Uttarakhand, 248007, India c School of Mechanical and Civil Engineering, Shoolini University, Solan, Himachal Pradesh, 173229, India d Department of Mathematics, GBPEC, Pauri Garhwal, Uttarakhand, 246001, India e Department of Basic Science, BFIT, Dehradun, Uttarakhand, 248007, India f Department of Mechanical Engineering, DIT University, Dehradun, Uttarakhand, 248009, India ABSTRACT This work presents a review of the research recent results concerning the augmentation of hydrodynamic and thermal performance of various twisted tape inserts in heat exchanger tubes. The thermal and hydrodynamic correlations for various twisted tape elements have been summarized. A comparative study of thermal and hydrodynamic performance of numerous twisted elements has also been reported to understand the result of applications of twisted tape inserts in heat exchanger tubes. The literature review found that multiple twisted tapes heat exchanger tube shape enhanced hydrodynamic and thermal performance than other comparable twisted tape inserts heat exchanger tube shapes. The review of twisted tape inserts techniques existing in this paper will be helpful to the investigators working in this field. Keywords: Heat transfer; heat exchangers; passive techniques; fluid flow.  Corresponding Author: E-mail addresses: anilkumar88242@gmail.com 1. INTRODUCTION Energy is a primary need to live our daily life at expenses of some valuable things such as environment degradation by using fossil fuels. Heat exchangers play a heating/cooling role in various fields like electric power, metallurgy, chemical engineering, refrigeration, and air- conditioning etc by Sunil et al. (2019), Singh Suri et al. (2017) and Kumar & Kim (2016). Circular tubes are widely used in heat exchange equipment’s because of the ease of production and its capability of withstanding a high pressure Kumar et al. (2017) and Singh et al. (2018). Insertion of twisted tapes into a tube provides a simple passive technique for enhancing the heat transfer by introducing vortex generator into the bulk flow by breaking laminar sub layer at the tube wall due to repeated changes in the surface geometry. While insert technology is employed for augmented heat transfer, pressure drop would be improved by inserting in twisted tape in a tube Kumar et al. (2017), Singh et al.(2018), Yashwant Singh et al. (2018) and Maithani et al. (2019). Twisted tapes with various shapes were proposed and utilized by various researchers. Numerous investigations have carried out the investigators in twisted tape inserts and thus, there is need to review the past and current research so that the further research scopes can be identified and implemented. The present article is thus aimed with following objectives:  To review the augmentation in heat transfer and pressure drop in heat exchanger tubes equipped with various twisted tape inserts.  To arrange the heat transfer and pressure drop correlations of a variety of twisted tape inserts in heat exchanger tubes.  To carry out comparative study of heat transfer and pressure drop of heat exchanger tubes equipped with twisted tape insert. In order to achieve the desired objectives, the article is structured batch wise for each objective clearly addressed and explained in their respective context. 2. LITERATURE REVIEW ON TWISTED TAPE INSERT IN HEAT EXCHANGER TUBES Efforts for improving the thermal and hydrodynamic performance of heat exchangers have directed the investigation in the direction of disturbing the viscous sub layer by proving twisted tape inserts. Many investigations have been carried out to analysis the flow field characteristics of thermal and hydrodynamic of twisted tape insert tubes. Singh et al. (2017) examined the efficiency factor of twisted tape round tube for stable heat flux. The Reynolds number covered in the range of 6300 to 22500 for co-twist arrangements in the turbulent flow of air in the round tube. Kongkaitpaiboon et al. (2010) experimentally investigated the augmentation of thermal hydrodynamic performance in circular tube equipped with perforated conical rings. It was concluded that the augmentation in thermal and hydraulic performance achieved was 3.67 and 2.89 times more than plain circular tube, respectively. Li and Guo (2009) carried out experimental and numerical investigation of turbulent heat transfer and stream resistance in an improved round tube equipped with twisted tape inserts. Promvonge (2008) experimentally studied the thermal and hydrodynamic performance of circular HET fitted with wire coiled inserts. The maximum value of thermal and hydrodynamic performance has been found to be 2.13 within the range of the parameters examined. Zhang and Zhang and Liu (2013) carried out numerical analysis of 3D turbulence fluid flow to study heat transfer and fluid flow Frontiers in Heat and Mass Transfer Available at www.ThermalFluidsCentral.org