Influence of Wired Twisted Tape on Heat Transfer Enhancement, Friction Factor and Thermal Performance Behaviors in a Heat Exchanger Tube

Heat transfer enhancement by multiple twisted tape inserts and TiO2/water nanofluid

3-D Numerical simulation of swirling flow and convective heat transfer in a circular tube induced by means of loose-fit twisted tapes

Heat transfer enhancement by twisted tapes with alternate-axes and triangular, rectangular and trapezoidal wings

Enhancement of heat transfer using CuO/water nanofluid and twisted tape with alternate axis

Thermohydraulics of Turbulent Flow Through Heat Exchanger Tubes Fitted with Circular-rings and Twisted Tapes

The thermal performance parameters of an improved heat exchanger tube fitted with various vortex generator inserts were investigated using numerical and experimental methods. The governing equations have been solved numerically by a Finite Volume approach employing the turbulence model (κ−ε). Two twisted tape types, which being inserted across a circular pipe (plain twisted tape) and (Double V-cut twisted tape), have been achieved. The hybrid nanofluid is prepared by using metal oxide [Al2O3+CuO] with distilled water at volume fraction range (0.6%, 1.2% and 1.8%), Reynolds number range (3560–8320) at twisted ratio (9.25). The experimental data for a plain tube, plain twisted tapes and double v-cut twisted tape are validated using the standard correlations available in the literature. The effect of such variables upon the average Nusselt number, friction factor, and thermal performance factor have been investigated and compared with a plain tube at the same conditions. As compared to plain twisted tape, the tube equipped with a double V-cut twisted tape with hybrid nanofluid displayed increased thermal performance. The greater vortex flow induced by the V-cuts results in more active thermal boundary layer disturbance, resulting in a greater heat transfer rate. The results show that thermal performance factor for hybrid nanofluid in plain circular tube at (∅=1.8%) and Reynolds number (8320) is about (1.068), when the plain twisted tape and double v-cut twisted tape inserted with hybrid nanofluid the thermal performance factor increased to (1.33) and (1.37), respectively. The results show a similar trend for both numerical and experimental cases. The comparison between the experimental and numerical results have maximum error was (9.7)%.

Heat transfer augmentation is an important concern due to the increase in heat management problems in thermal systems. There are many techniques for enhancement of heat transfer, by active and passive techniques. A commonly used passive technique to enhance heat transfer is by inserting twisted tapes in tubes. This work presents a numerical study on Nusselt number, friction factor, and thermal performance characteristics through a circular pipe built-in with/without dimples on twisted tape. The analysis results for a turbulent flow range of 4500≤Re≤20000 are obtained with a twist ratio of the strip is 3.0. The analysis is carried for full-length tape with constant heat flux. The governing equations are numerically solved by a finite volume method using the RNG κ–ε model. The simulation results of Nusselt number versus Reynolds number of the plain, plain twisted tape and dimple twisted tape tube with the experimental data give a variation of 4.15%, 3.89%, and 7.65%. The friction factor of the dimple twisted tape tube is 60 to 70% higher than that of the plain twisted tube at different Reynolds numbers. The thermal performance factor of the dimple twisted tape and plain twisted tape tube is 30 to 35% respectively higher than that of the plain tube. Due to thermal performance factor is above unity yields a promising heat transfer enhancement. By the present study, an optimum geometrical parameter can be selected for use in heat exchangers.

Thermal performances of tubular flows enhanced by ribbed spiky twist tapes with and without edge notches

Performance assessment in a heat exchanger tube with alternate clockwise and counter-clockwise twisted-tape inserts

Thermohydraulic investigation of turbulent flow through a round tube equipped with twisted tapes consisting of centre wings and alternate-axes

In the present work influence of different type of twisted tapes on the Nusselt number(Nu),Reynolds number(Re),Heat Transfer Coefficient (HTC), friction factor in the circular tube has been studied experimentally and air is consider as working fluid. A copper tube of 28 mm internal diameter, 33 mm external diameter, and 1000 mm test section length was used. Different twisted tape of aluminum was inserted in simple plain tube with constant twist ratio (y/w) 3.6. In this experiment swirling flow was created by using simple twisted tapes (STT) and alternate axis twisted tape (AATT). Reynold no. range 2500 to 8500 under uniform heat flux condition and it was created by the wrapping nichrome bend heater around the test section and asbestos as insulator over the nichrome. The experiment carried out under the similar operation test condition, for comparison. The experimental result indicates that tube with various types of tapes provides considerable improvement of the heat transfer rate in term of Nusselt number over the plain tube. Heat transfer rate increase by 23% for simple twisted tape 49% for alternate axis twisted tape as compare to plain tube with the loss of pressure drop. Keywords- Heat transfer enhancement, simple twisted tapes (STT), Alternate Axis Twisted Tape (AATT), Pressure drop, friction factor.

The thermo-hydraulic properties of circular tubes with a twisted tape inside (used accordingly to induce turbulence and enhance heat transfer through the tube wall) are described for Reynolds Numbers ranging from 830 to 1990. Tapes twisted with the three distinct twist ratios are considered, namely, 6, 4.4 and 3. Air is used as the working fluid in several tests. For the sake of comparison, the standard tube with no insert is also examined. It is shown that in the presence of the twisted tape, the ‘frictional factor’, ‘Nusselt Number’ and the ‘thermal performance factor’ are much higher than those obtained for the plain tube. Moreover, the tapes having the lowest twist ratio, i.e., 3, are more effective than the others in terms of heat transfer augmentation. The ‘thermal performance factor’ is greater than one for all the twisted tapes used in the experiments, which confirms the enhanced performances of the heat exchanger and the related savings in terms of total energy.

Thermal characteristics in a heat exchanger tube fitted with dual twisted tape elements in tandem

Influence of perforated triple twisted tape on thermal performance characteristics of a tube heat exchanger

Convective heat transfer enhancement using Ag-water nanofluid in a micro-fin tube combined with non-uniform twisted tape