Perforated Twisted Tapes Research Articles

Thermal-hydraulic performance of turbulent flows across a heated round tube installed through several perforated twisted tapes

PurposeThe purpose of this study is to advance turbulent thermal convection inside the constant heat-flux round tube inserted by multiple perforated twisted tapes.Design/methodology/approachThe novel design of this study is accomplished by inserting several twisted tapes and drilling some circular perforations near the tape edge (C1, C3, C5: solid tapes; C2, C4, C6: perforated tapes). The turbulence flow appearances and thermal convective features are examined for various Reynolds numbers (8,000–14,000) using the renormalization group (RNG) κ−ε turbulent model and Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm.FindingsThe simulated outcomes reveal that inserting more perforated-twisted tapes into the heated round tube promotes turbulent thermal convection effectively. A swirling flow caused by the twisted tapes to produce the secondary flow jets between two reverse-spin tapes can combine with the main flow passing through the perforations at the outer edge to enhance the vortex flow. The primary factors are the quantity of twisted tapes and with/without perforations, as the perforation ratio remains at 2.5 in this numerical work. Weighing friction along the tube, C6 (four reverse-spin perforated-twisted tapes) brings the uppermost thermal-hydraulic performance of 1.23 under Re = 8,000.Research limitations/implicationsThe constant thermo-hydraulic attributes of liquid water and the steady Newtonian fluid are research limitations for this simulated work.Practical implicationsThe simulated outcomes will avail the inner-pipe design of a heat exchanger inserted by multiple perforated twisted tapes to enhance superior heat transfer.Originality/valueThese twisted tapes form tiny circular perforations along the tape edge to introduce the fluid flow through these bores and combine with the secondary flow induced between two reverse-spin tapes. This scheme enhances the swirling flow, turbulence intensity and fluid mixing to advance thermal convection since larger perforations cannot produce large jet velocity or the position of perforations is too far from the tape edge to generate a separated flow. Consequently, this work contributes a valuable cooling mechanism toward thermal engineering.

A comprehensive analysis of heat transfer in a heat exchanger with simple and perforated twisted tapes based on numerical simulations

One of the most important methods to promote heat transfer (HT) in a heat exchanger (HE) is to use a twisted tape (TT) inside tubes. Therefore, in this paper, the result of the effect of TTs on the Nusselt number (Nu), and the performance coefficient of HEs in a laminar flow are investigated. plain tube (PT), simple TTs and perforated twisted tapes (PTTs) at 3 torsion ratio, blade numbers (N) 2, 4, 6 and 8 in the Reynolds numbers (Re) from 200 to 1000 are investigated. Ansys-Fluent computing software is used for this simulation. The findings indicate a positive correlation between the number of blades and both the Nu and the friction factor. It is important to acknowledge that the objective is to enhance the efficiency of the higher HE. Additionally, since there is an undesirable ratio between the rise of the Nu and the boost of the friction factor, so the HE coefficient decreases as the number of blades in TTs increases, from 6 to 8. The PTT with 6 blades provides the best performance coefficient. Compared to the simple TT, in the PTT, the Nu increases to 15.24%, the friction factor decreases to 22.26%, and the coefficient of thermal performance grows to 18.07%.

Heat transfer enhancement of the f-MWCNT- Fe2O3/Water hybrid nanofluid with the combined effect of wire coil with twisted tape and perforated twisted tape

The impact of various variables on thermal conductivity and rheological behavior, such as nano particle weight concentration and temperature, and also the cumulative effects of coil ratio (CR = 3, 4) of wire coil insert and twist ratio (TR = 3, 4 and 5) of twisted tape (TT) and perforated twisted tape (PTT) on heat transfer coefficient and friction factor characteristics is explored. Nanofluids containing particles with weight percentages of 0.01%, 0.02%, and 0.03% were produced by dispersing functionalized multi-walled carbon nanotubes (f-MWCNTs) 60% by weight and Fe2O3 nanoparticles 40% by weight in distilled water and stabilizing them with an ultrasonic probe. The KD-2 Pro thermal analyzer and Rheometer are used to measure the thermal conductivity and viscosity of the hybrid nanofluids. The impact of various factors on the heat transfer and pressure drop is investigated, including Reynolds number, nanoparticle concentration, TR and CR of TT, PTT and WC. The findings clearly show that higher content of nanoparticles increases heat transfer as well as pressure drop. In contrast to the base coolant, the enhancement in heat transfer and friction factor is 21.66%–31.66% and 1.14 times, respectively. In comparison to a plain tube passing through 0.03 wt % hybrid nanofluid, the enhancements in heat transfer and friction are 32.31%–94.03%, 43.94%–141.07%, and 1.09 times, 1.13 times for the combined effect of TT and PTT having wire insert at ratio's of twist and coil are 3, respectively. Furthermore, UV–vis spectroscopy is being used to assess the stability of the prepared nanofluids, which is found to be acceptable. FESEM is used to determine the detailed surface properties.

Modeling and optimizing perforated twisted tape for heat transfer enhancement

Previous studies on twisted tapes based on empirical design may overlook some structures having exceptional performance. To further develop the design flexibility, we propose a parametric modeling method for perforated twisted tapes (PTTs) in conjunction with multi-objective optimization to achieve heat transfer enhancement within the flow channel. This method considers the influence of structures on hydrothermal performance more thoroughly, and accelerates the development process. The control coefficients in the mathematical descriptions of the geometric characteristics expressed by Bernstein–Bézier functions were specified as the design variables. Two types of PTTs, full-width and half-width, were presented based on the variable ranges of width optimization. In the optimization, the observed objectives were the average temperature, root mean square temperature, and friction factor. A three-dimensional computational fluid dynamics model was employed to analyze the heat transfer and flow behaviors under three friction factor weight coefficients (0.1, 0.3, and 0.5) and was validated against experimental data. The numerical results showed that the maximum decrease in the average temperature and root mean square temperature of the heat source could attain 18.58 K (5.46%) and 2.92 K (72.64%), respectively. The friction factor was reduced by a maximum of 3.59 (57.35%) at the weight coefficient of 0.5 compared to 0.1. Furthermore, according to the performance evaluation criterion (PEC), the half-width PTTs generate less flow resistance and exhibit superior overall performance. The proposed method elaborates on the potential design space and provides a framework for the creation of efficient convective heat transfer devices.

RETRACTED ARTICLE: Augmentations of solar collector performance with involve of nanomaterial and perforated twisted tape

Perforated tape with obstacle was applied inside the absorber pipe filled with nanomaterial to intensify the efficiency of current solar collector. Simulations were done via ANSYS FLUENT with incorporating K–ε for turbulent flow and homogenous model for nanomaterial. To reduce the computation price, optimized size of grid has been selected and verification based on previous published data show the nice accuracy. Height of obstacle and number of revolutions were assumed as variables in simulations. Insert of turbulator makes the residence time to augment and stronger interaction with wall makes the outer wall become colder. Although the insert of tape makes convection to increase, the resistance with wall augments, too. Therefore, in current article, perforated shape of tape was utilized and to intensify the rotational velocity, obstacles over the tape were utilized. Augment of height and revolution can enhance the velocity about 4.58% and 7.04%. The temperature diminishes around 0.11% and 2.1% with elevate of N and Re.

Performance evaluation of solar parabolic trough receiver using multiple twisted tapes with circular perforation and delta winglet

A parabolic trough collector (PTC) is one of the concentrating types of a solar collector working in the medium range of temperature from 100–400 °C, for this reason, the efficiency of the solar parabolic trough is less than other types of concentrating solar collector (Point focusing types) in terms of solar to thermal energy conversion, the improvement in efficiency is achieved by various passive heat augmentation techniques in the receiver tube. One of the promising passive techniques is twisted tape inserts used in the receiver due to its simplicity in design and the various possibility of geometric modification. This paper deals with the performance evaluation of the solar parabolic trough receiver system by using passive techniques in the receiver. The testing of the receiver of PTC was done by using multiple perforated twisted tapes with winglets having different perforation ratios ([Formula: see text]) of 0.05, 0.15, 0.25, twist ratios ([Formula: see text]) of 3, 4, 5 and wing depth ratios ([Formula: see text]) of 0.1, 0.2 and 0.3. The number of twisted tapes was fixed at 4. The examination was conducted for Reynolds numbers ([Formula: see text]) varying from 3000–21,000 using air as working fluid. The outcome shows that the use of perforation and winglet in twisted tapes augment the Nusselt number as compared to that of smooth twisted tapes. The maximum thermohydraulic performance ([Formula: see text]) of 2.40 is received by using multiple twisted tapes with perforation and winglet having [Formula: see text] = 0.3, [Formula: see text] = 3, and [Formula: see text] = 0.05 at the Re = 21,000. The correlations for Nusselt number ([Formula: see text]) and friction factor ([Formula: see text]) are also developed with ± 8.5% and ± 8.3% accuracy, respectively.

Experimental Study of Parabolic Trough Receiver with Perforated Twisted Tape Insert Using Fuzzy Model Analysis

A solar water heating system has been fabricated and tested to analyze the thermal performance of Parabolic Trough Solar Collector (PTSC) using twisted tape insert inside absorber tube with twisted ratio about TR=y/w=1.33. The performance of PTSC system was evaluated by using three main important indicators: water outlet temperature (Tout), useful energy and thermal efficiency (ηth) under the effect of mass flow rate (ṁ) ranges between 0.02 and 0.04 Kg/s with the corresponding of Reynolds number (Re) range (2000 to 4000). In a parallel, a fuzzy-logic model was proposed to predict the thermal efficiency (ηth) and Nusselt number (Nu) of PTSC depending on the experimental results. The fuzzy model consists of five input and two output parameters. The input parameters include: solar intensity (I), receiver temperature (Tr), water inlet temperature (Tin), water outlet temperature (Tout) and water mass flow ( ) while, the output include the thermal efficiency (ηth) and Nu. The final results indicate that, owing to the mixture of the swirling flow of the perforated twisted-tape insert, the perforated twist tape insert enhances the heat transfer characteristics and the thermal efficiency of the PTSC system. More specifically, the use of perforate twist tape inserts enhanced the thermal efficiency by 4% to 4.5% higher than smooth absorber tube. Also, the predicted values were found to be in close agreement with the experimental counterparts with accuracy of ~92 %. So, the suggested Fuzzy model system would have high validity and precision in forecasting the success of a PTSC system compared to that of the traditional model. Pace, versatility, and the use of expert knowledge for estimation relative to those of the traditional model are the advantages of this approach

Investigation on thermal performance of different wire coil twisted tape inserts in a tube circulated with water

This study gives the combined outcome of twisted tapes (TT) and perforated twisted tapes (PTT) with twist ratios of (TRS) 3, 4 and 5 and wire coils (WC) coil ratios (CR) of 3 and 4 in a circular tube, where water has been circulated as the working fluid. The convective heat transfer coefficient (h) and friction factor (f) characteristics are examined in the turbulent flow regime (3000 ≤ Re ≤ 16,000) in order to obtain the thermal performance. These characteristics obtained with the combined effect of TT and PTT associated with WC in a plain tube are 65.06%–101.13%, 75.67%–177.81% and 2.75%–30%, 9%–28% respectively when compared with the circular tube. These enhancements are due to reversed flow caused by wire coils with swirling and impinging flow from the twisted tapes. In addition, high turbulence is created while the fluid is passing through the perforations of PTT. With the wire coil at TR = 3 and CR = 3, the maximum thermal enhancement factor at stable pumping power is 2.03 and 2.66 for TT and PTT, respectively. For all wire coils, twisted tapes and plain tubes, the correlations of Nusselt number and friction factor are established.

THERMO-HYDRAULIC PERFORMANCE ANALYSIS OF PARABOLIC CONCENTRATING SOLAR WATER HEATER

This paper concerns the thermo-hydraulic performance analysis of a PCSWH (parabolic concentrating solar water heater) with placing the PTT (perforated twisted tape) in the absorber tube. The experiments are performed using water as testing fluid. In this analysis, the mass flow rate changes from 0.0326 kg/s to 0.0667 kg/s and Reynolds number ranges from 2100 to 4250 respectively. The analysis is based on the effect of porosity of the PTT and mass flow rate over the pressure drop and heat transfer enhancement during the flow into the absorber tube of the PCSWH. At last to guess the increment in pressure drop and enhancement of heat transfer the empirical correlations for friction factor and the Nusselt number have been formulated considering the turbulent effect caused by PTT inside the absorber tube. The major observations of this analysis are that PTT enhances the pressure drop and heat transfer and also both enhances with increasing porosity of the PTT.

Experimental investigation of perforated twisted tapes turbulator on thermal performance in double pipe heat exchangers

In this paper, the experimental effect of the continuous and discontinuous twisted tapes turbulator (perforated and non-perforated) on the inner side of the internal tube in the double heat exchangers on heat transfer, the friction coefficient, and thermal performance have been discussed. On discontinuous twisted tapes turbulator, 9 holes with different geometries, such as triangular, square, rectangular, circular, and diamond with the triangular arrangement, have been created on turbulator flat surfaces. The Reynolds range is investigated at 5500–10000, and working fluids are on the side of the inner tube and annular space is hot and cold water, respectively. Experimental results have shown that discontinuous turbulator has a better effect on heat transfer and pressure drop than continuous turbulator. As the discontinuous turbulator without a hole has an increase in heat transfer of 8.2 % and a reduction of 9.8 % in the pressure drop coefficient compared to the continuous turbulator. Then the effect of perforation on discontinuous twisted tapes turbulator was investigated. Experimental results show that perforated discontinuous turbulator with circular, square, rectangular, diamond and triangular perforation with the same hydraulic diameter as for discontinuous turbulator without perforation was 20.8 %, 15 %, 11 %, 8.7 %, 5 % increase in heat transfer and 27.7 %, 22.8 %, 17.3 %, 12.1 %, 5.5 % decrease in the coefficient of pressure drop, respectively. Therefore, according to the results, the best thermal performance was related to the perforated of perforated discontinuous twisted turbulator, discontinuous twisted turbulator, and continuously twisted turbulator were respectively.

Thermal characteristics of perforated self-rotating twisted tapes in a double-pipe heat exchanger

The present study experimentally investigated thermal characteristics of a double-pipe heat exchanger fitted with perforated self-rotating twisted tapes with six perforation ratios of 0%, 1.16%, 3.63%, 6.46%, 10.1% and 14.49%. The experimental results showed that perforation ratio significantly affects the initial stage of rotation behavior and rotational speed. Perforated self-rotating twisted tapes were experimentally shown to perform greater thermal performance than perforated stationary twisted tapes. In addition, the increase in perforation ratios raised the Nusselt number and pressure drop. Higher thermal performance factor of PR = 10.1% than PR = 14.49% under rotating condition could be found. When the self-rotating twisted tapes varied from stationary to rotating condition, it is observed that thermal performance factor increased from 0.862 to 0.924, 0.987 to 1.025, 1.04 to 1.078, 1.084 to 1.101, and 1.042 to 1.055, for perforation ratios of 0%, 1.16%, 3.63%, 6.46%, and 10.1%, respectively. Finally, some correlations associated with perforation ratios were established to predict Nusselt number and friction factor, and perforated self-rotating twisted tapes were compared with perforated twisted tapes in terms of thermal performance factor. The optimal design of perforated self-rotating twisted tapes with proper perforated ratio could be offered for industrial application based on thermal performance evaluation.

Study of Entropy Generation in Heat Exchanger Tube With Multiple V Cuts in Perforated Twisted Tape Insert

The present work deals with the study of entropy generation in circular tube fitted with perforated twisted tape (PTT) insert with multiple V cuts. Experimental data pertaining to heat transfer and frictional losses are collected for solid twisted tape (STT), PTT, double V cut PTT, and PTT with multiple V cuts by varying the twist ratio in the range of 2–6 for the Reynolds number range of 2000–25,000. The entropy generation rate of heated tube with insert is found to be less than the smooth tube in most of the cases under similar operating conditions. The minimum value of entropy generation number corresponds to the PTT having twist ratio of 3.

Proposing a method for combining monitored multilayered perceptron (MLP) and self-organizing map (SOM) neural networks in prediction of heat transfer parameters in a double pipe heat exchanger with nanofluid

The purpose of this study was to investigate the efficiency of using magnesium oxide nanoparticles, twisted tapes with different and modified twist ratios, and the different rotation velocity of perforated twisted tapes in the evaluation of Nusselt number, overall heat transfer coefficient and pressure drop in a double pipe heat exchanger. Subsequently, the results obtained from the experimental tests of Nusselt number, overall heat transfer coefficient and pressure drop using a modified twisted tape in a double pipe heat exchanger and a back propagation artificial neural network with a multilayered perceptron structure show the existence of a relationship between heat transfer parameters and input data such as cold and hot fluid temperatures, volume fractions of nanofluid, twisted tapes of different twist ratios, the rotation velocity of twisted tapes, Reynolds number of hot and cold fluids, viscosity and thermal conductivity of the nanofluid. Also, the non-monitored artificial neural network selected 33 neurons for use in the multilayered perceptron neural network. The network included the sigmoid function in the hidden layer and the Levenberg–Marquardt training algorithm with a three-layer topology of 9–33-1 with the correlation coefficients of 0.9987, 0.9933 and 0.9944 and the mean squared error of 0.66535, 4547.68 and 0.008768. This network was best for predicting heat transfer parameters such as Nusselt number, overall heat transfer coefficient and pressure drop.

A Comparative Study on Heat Transfer and Friction Factor Characteristics of Silicon Carbide-water Nanofluids in a Circular Tube Fitted

The effect of perforated twisted tapes with alternate axis (PATT), perforated twisted tapes (PTT) and regular twisted tapes (TT) with twist ratios (TR) of 3 are compared by an experimental investigation in a circular tube with Silicon carbide (SiC)-water nanofluid flowing in it under constant heat flux condition. Using 0.1 wt. % concentration of the SiC nanofluid containing SiC nanoparticles obtained after 5 h of ball milling as the testing fluid, experiments are conducted within the Reynolds number range of 3000 – 16000. The heat transfer rates in the tube fitted with TT, PTT and PATT at TR = 3 are respectively improved up to 9.59 %, 18 % and 19.51 % of that in the plain tube. Similarly, the increase in friction factor for TT, PTT and PATT at a TR = 3 is 22.5 %, 24 % and 28.9 % respectively, compared to that of the plain tube. As PATT is giving maximum heat transfer enhancement, the empirical correlations were established for its Nusselt number and friction factor at different twist ratios and the obtained correlations are fitted with the experimental data. Hence, the passive elements when employed along with the nanofluid gives better energy efficiency along with lower operating cost and is therefore suggested for commercial heat transfer applications.

A comparative study on the thermal performance of water in a circular tube with twisted tapes, perforated twisted tapes and perforated twisted tapes with alternate axis

The effect of perforated twisted tapes with alternate axis (PATT), perforated twisted tapes (PTT) and regular twisted tapes (TT) with twist ratios (TR) of 3,4 and 5 are compared by experimental investigation in a circular tube under constant heat flux condition. Using water as the testing fluid, experiments are conducted within the Reynolds number range of 3000–16000. The heat transfer rates in the tube fitted with PATT, PTT and TT are respectively improved up to 48.12%, 44.3% and 33% of that in the plain tube. Similarly, the increase in friction factor for PATT, PTT and TT is 19.1%, 17.6% and 15.85% respectively, compared to that of the plain tube. For all inserts, the empirical correlations were established for Nusselt number and friction factor along with plain tube and the obtained correlations are fitted with the experimental data. At constant pumping power, the maximum thermal performance factor obtained is 1.433, 1.396 and 1.24 respectively for PATT, PTT and TT. Hence, the passive element which gives better energy efficiency along with lower operating cost is suggested for practical heat transfer applications.

Effect of V cut in perforated twisted tape insert on heat transfer and fluid flow behavior of tube flow: An experimental study

ABSTRACTPresent study investigates the heat transfer and friction characteristics of heat exchanger tube fitted with perforated twisted tape (PTT) insert having V cuts. A copper tube of 1 m length and 0.032 m inner diameter is used as test section to collect the experimental data by varying the twist ratio of PTT from 2 to 6 for the Reynolds number range of 2,700–23,400. V cuts are introduced in the PTT and the V-cut relative pitch ratio is varied from 1 to 2. The maximum thermo-hydraulic performance parameter is found to be 1.58.

Optimization of heat transfer and pressure drop in a tube with loose-fit perforated twisted tapes by Taguchi method and grey relational analysis

This work introduces the determination of the optimum values of the design parameters in a tube with loose-fit perforated twisted tapes. The effects of the design parameters such as twist ratio (y/D), width ratio (W/D), hole diameter ratio (d/D) and Reynolds number (Re) on heat transfer (i.e. Nusselt number) and pressure drop (i.e. friction factor) were analyzed by Taguchi method (TM) and grey relational analysis (GRA). The Nusselt number and friction factor were taken into account as performance parameters. Taguchi Method is based on analysis of variances and implements the orthogonal arrays for experimental design. L16 orthogonal array was selected as experimental plan. Firstly, each performance parameter was optimized, independently. Then, all the performance parameters were optimized together by TM and GRA. According to the experimental plan results, the most important factor for both Nusselt number and friction factor is Reynolds number, while the least significant factors are twist ratio (y/D) and width ratio (W/D).

Experimental determination of enhancement of heat transfer in a multiple square perforated twisted tape inserts heat exchanger tube

ABSTRACTThis paper presents an experimental determination of Nusselt number and friction factor of heat exchanger tube with multiple square perforated twisted tape inserts. The effect of geometrical parameters, especially, perforation width ratio and twist ratio, has been investigated. The perforation width ratio and twist ratio have been varied from 0.083 to 0.333 and 2.0 to 3.5, respectively. The optimum values of parameters for multiple square perforated twisted tape inserts arrangement have been obtained and discussed. The effect of multiple square perforated twist tape inserts has been investigated for the range of Reynolds number from 5,000 to 27,000. The effect of important parameters on the and has been discussed, and the results are compared with the results of without square perforated multiple twisted tape inserts and smooth surface heat exchanger tube under similar flow conditions. The optimum values of parameters for multiple square perforated twisted tape inserts heat exchanger tube arrangement have been obtained and discussed. The maximum enhancement is observed at a of 0.250 and of 2.5, respectively.

Study the effect of axially perforated twisted tapes on the thermal performance enhancement factor of a double tube heat exchanger

The main objective of this numerical study is to investigate the ways to reduce the pressure drop and consequently increase thermal performance enhancement factor (TEF) of a heat exchanger equipped with twisted tapes. For this purpose, axial perforated twisted tapes (PTTs) with various hole diameters are used instead of simple twisted tapes (STTs). Moreover, the variations of the effectiveness with number of transfer units (NTU) for different heat capacity ratios (Cr) were presented. The numerical model was well validated with the available experimental results. The results indicated that the use of perforated twisted tape leads to a reduction in pressure drop and heat transfer rate, subsequently; a significant increase in TEF was seen compared to simple twisted tapes. In addition, some correlations were formulated to present the numerical results.

Effect of square wings in multiple square perforated twisted tapes on fluid flow and heat transfer of heat exchanger tube

This work presents, an experimental study on Nusselt number (Nurs) and friction factor (frs) of heat exchanger circular tube fitted with multiple square perforated with square wing twisted tape inserts. The experimental determination encompassed the geometrical parameters namely, wing depth ratio (Wd/WT) of 0.042–0.167, perforation width ratio (a/WT) of 0.250, twist ratio (TL/WT) of 2.5, and number of twisted tapes (NT) of 4.0. The effect of multiple square perforated twisted tape with square wing has been investigated for the range of Reynolds number (Ren) varied from 5000 to 27,000. The maximum enhancement in Nurs and frs is observed to be 6.96 and 8.34 times of that of the plain circular tube, respectively. Correlations of Nurs, frs and ηp are established in term of Ren and geometrical parameters of wings twisted tape which can be used to predict the values of Nurs, frs and ηp with considerably good accuracy.