Numerical Study of Heat Transfer Enhancement of Internal Flow Using Double-Sided Delta-Winglet Tape Insert

Abstract

A numerical study was performed to investigate the thermal performance characteristics of an enhanced tube heat exchanger fitted with punched delta-winglet vortex generators. Computational fluid dynamics modeling was applied using the k–ε renormalized group turbulence model. Benchmarking was performed using the results of the experimental study for a similar geometry. Attack angles of 30°, 50°, and 70° were used to investigate the heat transfer and pressure drop characteristics of the enhanced tube. Flow conditions were considered in the turbulent region in the Reynolds number range of 9100 to 17,400. A smooth tube was employed for evaluating the increment in the Nusselt number and the friction factor characteristics of the enhanced tube. The results show that the Nusselt number, friction factor, and thermal performance factor have a similar tendency. The presence of this insert offers a higher thermal performance factor as compared to that obtained with a plain tube. Vortex development in the flow structure aids in generating a vortex flow, which increases convective heat transfer. In addition, as the angle is varied, it is observed that the largest attack angle provides the highest thermal performance factor. The greatest increase in the Nusselt number and friction factor, respectively, was found to be approximately 3.7 and 10 times greater than those of a smooth tube. Through numerical simulations with the present simulation condition, it is revealed that the thermal performance factor approaches the value of 1.1. Moreover, the numerical and experimental values agree well although they tend to be different at high Reynolds number conditions. The numerical and experimental values both show similar trends in the Nusselt number, friction factor, and thermal performance factor.

Internal Flow in an Enhanced Tube Having Square-cut Twisted Tape Insert

“…The hot water and cold water are transported through the inner and outer tubes, respectively. The thermo-physical properties of water [15], which are considered as the inlet values during the calculation, are listed in Table 1. Table 1.…”

“…Table 1. Thermo-physical properties of the hot and cold water at inner and outer tube inlets [15]. as shown in Figure 1, and the boundary condition to be applied in the domain was decided.…”

“…Table 1. Thermo-physical properties of the hot and cold water at inner and outer tube inlets [15]. Based on the thermo-physical properties of the working fluid (density, velocity, and viscosity) and the inner diameter of the inner tube, Re can be estimated as:…”

“…Numerous research studies have been performed on heat exchangers, to enhance the heat transfer, in order to achieve a higher heat exchange performance [1,2]. For this purpose, the following efforts have been reported in our previous works: a direct contact system for adsorption cycle [3][4][5], using nanofluid as the working fluid [6,7]; improvement of maldistribution inside the distributor of heat exchangers [8][9][10]; using inserts inside the tubes [11][12][13][14][15]. Based on the published reports, it is known that the investigations on passive heat transfer enhancement methods using various inserts do not consider the existing problems.…”

Influence of Geometric Parameters of Alternate Axis Twisted Baffles on the Local Heat Transfer Distribution and Pressure Drop in a Rectangular Channel Using a Transient Liquid Crystal Technique

“…Heat transfer equipment efficiently use energy. Therefore, it is necessary to develop advanced heat transfer equipment that is needed in various industries for efficiency and cost-effective energy use [1,2]. Liu and Sakr [3] classified convection heat transfer modes into three categories: passive techniques, active techniques, and a combination of the two.…”