Tape Inserts Research Articles

Numerical simulation of solar parabolic trough collector with twisted tape insertion shielded within inner cylindrical tube

ABSTRACT In this study, the effects of variations in geometrical parameters of shielded twisted tape within the inner cylinder of the absorber tube on the performance enhancement of the parabolic trough collector (PTC) have been investigated. The objective is based on the prediction of the optimized value of geometrical parameters for the modified parabolic trough collector (MPTC) showing the best thermal performance among them. Numerical simulation techniques with Ansys-Aim2020R1 have been used for this investigation. It is desired to determine whether it is advantageous to use inner shielding around the inserts within the absorber tube; and if so, which geometrical parameter plays a crucial character in the prediction of the best possible thermal performance of the system. It was found that with a twisted tape thickness of 0.002 m, twisted tape gap of 0.001 m, inner cylinder center distance of 0.020 m, and the number of twists of the twisted tape of 50 turns the PTC has shown the best possible performance of the system. These findings reflect optimized geometrical parameters of the twisted tape insert shielded by an inner cylindrical tube. The thermal efficiency (η) of the MPTC was found to be 86.5% and approximately 2.063 times that of the conventional PTC. It is a novel endeavor regarding the approach of utilizing the shielding around the inserts within the absorber tube.

Heat Transfer Enhancement in Laminar Pipe Flow Using Al2O3–Water Nanofluid and Twisted Tape Inserts

Abstract In this study, an attempt has been made to carry out a numerical investigation using water-based Al2O3 nanofluid, flowing through a circular tube under constant inlet temperature and constant heat flux conditions in the laminar flow regime. The water-based Al2O3 nanofluid is used in a circular plain tube first, and then, this process is repeated for the same tube fitted with twisted tape inserts of twist ratio 1.85 at Reynolds numbers ranging from 680 to 2030. For the numerical analysis, ANSYS FLUENT is used to solve three-dimensional conservation equations of mass, momentum, and energy. The simulated results indicate that when twisted tape is used, heat transfer rates increase significantly with the use of nanofluid. In the case of nanofluid with the plain tube, only 10–24% enhancement in heat transfer rate is noted. On the other hand, almost 27–45% increase in heat transfer is observed compared to that with only water when twisted tape is inserted into it. Also, the friction factor increases as the nanoparticle volume fraction increases. However, the effect on the heat transfer rate is more significant than that on the friction factor. The best thermohydraulic performance factor achieved is 2.1 using nanofluids with a 5% volume fraction of the nanoparticles at a high Reynolds number when twisted tape is also inserted.

Optimization of thermohydraulic performance of tube heat exchanger with L twisted tape

A numerical investigation was conducted to explore the heat transfer optimization effect of circular tube heat exchanger with L-shaped twisted tape insert and to find the optimal parameter design in this paper. For better thermohydraulic performance, the effects of twist pitch (P), inner diameter (D), tape width (W) and number of tape (N) were studied with Reynolds number ranged from 1875 to 3750. Moreover, response surface method (RSM) was employed to indicate the relationship between the Nusselt number (Nu) and these parameters. With the analysis of flow structure inside the tube, it was conducted that the twisted tape insert was helpful to transform the axial velocity of fluid to radial velocity, forming vortex in the L region. The numerical results showed that the Nu and friction factor (f) of the tube fitted with L-shaped twisted tape insert gained an 199% to 208% increase and 674% to 696% when compared with that of smooth tube respectively. Besides, an optimal parameters set was obtained with P = 65.59 mm, W = 0.95 mm, D = 8.80 mm, in which the Nu and f were increased by 204% and 704% respectively as the results of response surface method.

Thermohydraulic performance of a semi-alternated twisted tape insert and cylindrical baffles in a tube with ternary nanofluid under sinusoidal wall temperature

This study numerically evaluates the thermohydraulic performance of a circular tube consisting of semi-alternated twisted tape mounted with cylindrical baffles and ternary nanofluid (SiO2 + ZnO + CaO) as a working fluid. The circular tube wall was exposed to a sinusoidal temperature that axially varied along the wall. The investigation was performed in the laminar flow regime over the Reynolds number 500–2000 and for nanofluid volume fraction 0.01%-0.05%. The semi-alternated twisted tape has pitch ratio 1.77–5.77, width ratio 0.38–0.68 and thickness ratio 0.019–0.033. The performance was analyzed for Nusselt number, pressure drop, thermal performance factor and pumping power. The results indicate, no significant pressure drop increment with volume fraction of the ternary nanofluid. For a fixed volume fraction of 0.01%, width ratio of 0.48 and thickness ratio of 0.019, there is an improvement in Nusselt number by 35–107%, pressure drop increased from 0.26 Pa to 3.5 Pa, pumping power was found to increase by 40%, and thermal performance factor by 1.35–1.67 times that of the smooth tube, when the pitch ratio decreases from 5.77 to 1.77. For a fixed pitch ratio of 1.77 and width ratio 0.38–0.68, the Nusselt number increased by 50–114%, pressure drop increased from 0.207 Pa to 11.1 Pa and thermal performance factor by 1.18–1.76 times as compared with smooth tube. The Nusselt number increased by 100–115% and thermal performance factor increased from 1.08 to 1.16 times the performance of the smooth tube when the thickness ratio was increased from 0.019 to 0.033.

Photovoltaic-thermal system combined with wavy tubes, twisted tape inserts and a novel coolant fluid: energy and exergy analysis

To create a highly efficient photovoltaic-thermal (PV-T) system and maximise the energy and exergy efficiency, this study aims to propose an innovative configuration of a PV-T system comprising wavy tubes with twisted-tape inserts. Following the validation of a numerical model, a parametric study has been conducted to assess the geometrical effects of twisted tape and wavy tubes, as well as the coolant fluid type and velocity, on the overall performance of a PV-T system, located in Shiraz, Iran. It is found that employing twisted tape improves the energy and exergy efficiency by approx. 6.3%. The best configuration yields 12.4% and 16.8% increase in energy and exergy efficiency compared to conventional PV systems. This is achieved at 15% volumetric concentration of microencapsulated phase change material slurry. The monthly variation of global horizontal irradiance in Shiraz highly affected the energy and exergy efficiency of PV-T, with July and October exhibiting the most efficient months, corresponding to 90% and 11.3%, respectively.

Study of thermal performance of double pipe heat exchanger using W-cut twisted tape

ABSTRACT An experimental analysis was carried out to estimate Nusselt number and friction factor behavior in a double pipe heat exchanger for W-cut twisted tape, in which Reynolds numbers ranging from 5500 to 16,000 are used, and the depth of W-cut to width of twisted tape ratio are 0.2, 0.4, and 0.6 in twisted tape of 10 mm width and 1 mm thickness. Effects of twist ratio are also analyzed by varying twist ratio 5, 10 and 15. It has been found that using twisted tape inserts causes turbulence and flow separation, resulting in better fluid mixing. Due to augmentation in turbulence, an enhancement in heat transfer and TPF was observed. Validation of test section done with predefined correlation and experimental results. It has been found that peak enhancement in Nusselt number and friction factor observed at Reynolds number 5500 for depth of W-cut 6 mm and twist ratio of 5 is\\\\are 105.47% and 301% respectively. Maximum TPF and friction factor were seen under the same circumstances. For the current analysis, the maximum TPF observed is 1.35.

Experimental evaluation and thermal performance analysis of a twisted tape with dimple configuration in a heat exchanger

This contemporary experiment examines heat transfer and friction factor of liquid (water) going in a double pipe heat exchanger with twisted tape (TT) insert. Effect of twisted tape in DPHE inserts dimple configuration by providing a dimple protrusion surface only on the front face with a hole configuration placed adjacent to it over the tube length of 1500 mm and diverse dimple diameter (D) and dimple diameter-to-depth ratio (D/H) proceeding heat transfer and friction factor(f) characteristics are analysed in this work. Twist ratio for all cases is 5.5 for each twist, range of Reynolds number (Re) 6000–14,000, D of 2, 4, and 6 mm and (D/H) of 1.5, 3 and 4.5. Six twisted tapes with dimples were tested, and their performance was compared to that of twist with plain tube. It is discovered that the Nusselt number is the deviance with respect to Reynolds number of a plain tube (without twisted tape and dimples) with an inner tube diameter of d = 16 mm. It is evident from the plot that there is an increase in the rate of Nusselt number with a subsequent increase in the value of Reynolds number. Through experimental analysis conducted, Therefore, Optimum value for higher Nusselt number is standard for discussion at D/H = 3 for different diameter as it 111 (for Re = 13987) and 58 (for Re = 6180) using D = 4 mm. As a result of the investigation, it is determined that the depth and diameter of the dimple is directly proportional to the friction factor. Therefore, optimum value for lower friction factor is benchmarked for discussion at D/H = 4.5 for different diameter as it 0.1033 (for Re = 13987) and 0.1437 (for Re = 6180).

Study of Twisted Tape Inserts Segmental Application in Low-Concentrated Solar Parabolic Trough Collectors

This article presents the results of an analysis of heat enhancement intensification using twisted tapes in linear absorbers for low-concentration parabolic trough collectors, a technology frequently considered as a supplementary energy source for industrial heat production. This contribution proposes a segmented application of different twisted tapes to intensify heat absorption. A 33.7 mm tubular absorber placed in the collector focal point with an aperture of 1.8 m was selected. The temperature range of the heat transfer fluid was chosen at 60–250 °C. The impact of inserts with twisted ratios of 1, 2 and 4 on system operation was analysed using the Ansys Fluent and mathematical model. The models used were validated based on experimental results from a parabolic trough collector with solar simulator test bench. The results indicated that for the range of mass flow between 0.15–0.3 kg/s, the most optimal is applying twisted ratio 1, except for the highest-temperature section. In this section, it is more optimal to use an insert with a twisted ratio 2, due to the lower need for pumping and the higher efficiency increment. The long-term analysis for the case study plant indicated that the proposed approach increased power gain by 0.27%.

The optimal geometric design of a v-corrugated absorber solar air heater integrated with twisted tape insert

The proper design of a solar air heater depends on the highest thermal performance of the solar collector. In the present paper, proposed a method to find an optimal dimension of V-corrugated absorber solar air heater (VSAH) combined with a twisted tape insert (TTI). The design variables of the VSAH-TTI are length, width, number of channels, and twisted tape ratio. The effect of each design variable is examined and studied under various ranges of Reynolds number (Re). Given the complexity in changing design variables of solar collector having a V-corrugated absorbing plate with twisted tape insert (VSAH -TTI) to find the highest thermal performances, the multi-objective function genetic algorithm is used to find the optimal dimensions of VSAH-TTI based on maximizing the heat gain, thermal and effective efficiency as well as minimizing the pressure drop on solar collector. The range of each design variable of the VSAH-TTI by means of length (1 – 2.5 m), width (0.5 – 1.5 m), number of channels (4 – 14), and twisted tape ratio (1 – 8) are specified in paper based on the most common practical values of the solar collector. The results showed for the case under study that each design variable of VSAH-TTI affect the thermal performance and the optimized geometry by using a genetic algorithm (Ga) can find the optimal geometric dimensions of VSAH-TTI. The optimal dimension by using Ga can increase the heat gain by more than 8% and increase the effective and thermal efficiency of more than 7% for the original geometry. Furthermore, the optimized geometry can reduce more than 29% for the original geometry. These improvements in optimized geometry for VSAH- TTI without introducing any additional items.

Entropy generation and thermohydraulics of mixed convection of hybrid-nanofluid in a vertical tube fitted with elliptical‑cut twisted tape inserts - a computational study

ABSTRACT A numerical investigation is carried out to study the mixed convection of Al2O3-Cu/water hybrid-nanofluid in a vertical tube fitted with elliptical-cut twisted tape inserts (TECT). Thermodynamic irreversibilities are evaluated by calculating the Bejan number, as well as the system’s local and total entropy generation. Heat transfer, friction factor, thermal performance factor, and entropy generation analyses are conducted for a range of volumetric concentrations of nanoparticles and flow Reynolds numbers between 7000 and 15,000. The realizable k- model is employed to simulate the turbulent and heat transferring flow computationally. The results clearly demonstrate the influence of mixed convection on heat transfer and entropy generation. In particular, mixed convection simulations predict greater Nusselt number, friction factor, and thermal performance factor than the corresponding forced convection simulations. Further, it is shown that the Nusselt number and the thermal performance factor for mixed convection are 4.6% and 5.5% higher than those for forced convection, respectively. The results also reveal that at Reynolds numbers of 7000, 9000, and 11,000, the thermal entropy production dominates the total irreversibility of the system. Likewise, frictional entropy production is the dominant mode of total irreversibility in the system at high Reynolds numbers of 13,000 and 15,000.

Heat transfer enhancement in a tube with a twisted tape inserted for various length ratios

ABSTRACT Energy efficiency is a major concern in pipe systems, particularly in applications where heat transfer is significant. Twisted tape insertion is used to enhance heat transfer in pipes. In this numerical study, twisted tapes with various length ratios (LR) (30–100%) were inserted into a tube filled with water. The tube surface was subjected to a uniform heat flux. The Nusselt number (Nu) and friction factor (f) variations were investigated for several Reynolds number values (Re) (2500–10,000) under hydrodynamically developed and thermally developing flow conditions between laminar and turbulent flows in the transition and low-turbulent regime. The results are validated with the available theoretical results and experiments. The maximum Nu enhancement is observed at an LR of 90% based on a factor of 1.55; an LR of 70% demonstrated a similar factor of ~1.5 and a friction factor 3.7 times more than that of plain tubes. This ratio provides the best results for the enhancement factor, which is 1.2 times higher at the maximum level. Consequently, an LR of 70% is considered to be sufficient to obtain an optimum combination of maximum heat transfer and minimum friction combination, and this combination is preferred over completely filling the tube with twisted tape.

Thermal and Flow Analysis of TiO2 Nanofluid Flow in Circular and Square Ducts with Multiple Twisted Tape Inserts

A numerical study is conducted to observe the thermal and flow performance of TiO2 nanofluid in the circular and square ducts with different twisted tape arrangements. The presence of the twisted tape in the tube induces swirl flow, which aids in the heat transfer, but at the penalty of a higher friction factor. The results also reveal that the maximum Nusselt number enhancement is obtained in the circular tube when the counter-triple twisted tape arrangement (C-TTs) is adopted while it is co-triple twisted tape arrangement (Co-TTs) for the case of square duct. Besides, the highest friction factor is observed for the Co-TTs for both circular and square ducts. The heat transfer and friction factor in the circular duct are greater than that of the square duct. The highest thermal performance factor of 1.286 is obtained when the single twisted tape and 1.5% nanofluid are used in the circular tube. However, multiple twisted tape inserts in the square duct contributes to improved thermal performance at a relatively lower friction factor when compared to the circular tube. Therefore, it is recommended to implement the square duct with multiple inserts for compact or microchannel heat exchanger for heat transfer application.

Intensified convective energy tapping in modified tubes using Azadirachta indica brewed zinc oxide as potential thermo-fluids

Reusing certain types of decomposed tree leaves is beneficial for biosynthesizing nanoparticles for nanofluids to meet energy sustainability and conservation. Encapsulating and reductant agents in Azadirachta indica (neem) help with fluid stability besides providing higher thermal transport properties. Sol-gel technique was adopted to prepare zinc oxide (ZnO) nanoparticles with neem solution to obtain neem-doped zinc oxide (ZnOneem) particles. According to the Debye-Scherrer relation, the size of ZnOneem was 36 nm. Optimal fluid stirring and sonication parameters were identified to synthesize and stabilize 0.05, 0.2, and 0.6% concentrated nanofluids with aqua-antifreeze (50:50) without surfactant. While the optimal stirring speed and time of 0.05, 0.2, and 0.6% nanofluids were 322 rpm and 36 min, 329 rpm and 33 min, and 334 rpm and 29 min, respectively, the optimal sonication time were 39 min, 34 min, and 32 min, respectively. However, sodium dodecyl sulphate (SDS) at a dispersion fraction of 0.6 ensured 35 months of good suspension. Pumping these turbulent fluids (Re = 5000–10000) through a microfin tube snug-fit with twisted tape inserts (twist pitch, y = 63, 84, and 105 mm) ensured the best outcomes with all the fluid samples. The Nusselt number ratio of 2.114 is the best at a penalty of 2.228 friction factor ratio with 0.6% concentrated nanofluid at Re = 10,000 circulating within the tube fit with Y = 6 tape. For this case, the Bejan number was 0.72, with the maximum Performance Evaluation Factor (PEF) and the Entropy Performance Evaluation Factor (EPEF) being 1.619 and 154.02, respectively.

The influence of different twisted tape inserts configurations on thermo-hydraulic performance and enhancement of heat transfer in the 3D circular tube

The influence of different twisted tape inserts configurations on thermo-hydraulic performance and enhancement of heat transfer in the 3D circular tube

Numerical investigation of heat transfer augmentation and frictional loss characteristics in heat exchanger tube with the use of novel perforated rectangular cut twisted tape

ABSTRACT This paper focuses on augmentation of heat transfer and thermal performance factor of tubular heat exchanger by using a novel Perforated Rectangular Cut Twisted Tape (PRCTT) and comparison was made with Plain Tube (PT), Simple Twisted Tape (STT) and Rectangular Cut Twisted Tape (RCTT). Analysis of Nusselt number and friction factor for the twisted tape insert having twist ratio (TR) of 3, rectangular cuts of 2 mm width and 1 mm depth is done. Rectangular cuts of different pitch, that is, 3 mm, 5 mm and 7 mm is used for the analysis. To reduce the friction factor, further analysis has been done with perforation of circular hole in the same RCTT with perforation ratio (d/w) of 0.55 in the core of insert. Numerical analysis shows that in turbulent zone (4000<Re > 16000), highest enhancement in Nusselt number is 2.3 times and highest enhancement of friction factor by 3.2 times with comparison to plain tube when reducing the pitch of rectangular cuts. Perforation further decreases the friction factor by 20%. Highest thermal performance factor is observed 1.48 with the use of Perforated Rectangular Twisted Tape (PRCTT) at Re = 4000.

Thermohydraulic performance investigation of a heat exchanger with combined effect of ribbed insert and Therminol55/MXene+ Al2O3 nanofluid: A numerical two-phase approach

MXene-based nanofluids are novel trends with improved dispersion stability and thermophysical characteristics over previously established nanofluids. In the present work, the thermohydraulic characteristics of a double pipe heat exchanger (DPHEX) with a Therminol55(TH55)/MXene + Al2O3 nanofluid and various geometrically shaped (triangular, rectangular) ribbed twisted tape (TT) inserts are numerically investigated using the ANSYS Fluent interface. A counter flow arrangement with three different types of inserts (RRTT, TRTT, TT) and TH55/MXene + Al2O3 nanofluid at 0.20 wt% are studied inside the heat exchanger. Adding ribbed inserts to the conventional TT insert enhances the turbulence intensity by creating extra vortices. The thermal boundary layer grows thinner due to increased axial and radial velocity. Due to the substantial flow obstruction, adding ribs increases the overall pressure drop between the inlet and outlet. The maximum increase in Nu is 11.04 % using nanofluid instead of water, whereas the combination of insert and nanofluid exhibited up to 105 % enhancement for rectangular-ribbed TT compared to the plain tube. Nevertheless, the pressure decrease is found to be maximum in rectangular-ribbed TT because of significant flow disruption. This was likewise true with triangular-ribbed TT and TT insert. According to the PEC assessment, the RRTT insert had a maximum PEC value of 1.67 greater than TRTT and traditional TT for both TH55 and nanofluid flowing inside the tube. To summarize, the combination of TH55/MXene + Al2O3 RRTT insert may be a promising choice for improving heat exchanger performance in a new generation efficient thermal system.

Thermohydraulic performance of DPHE affected by triangular and semi-circular cut size on insert: IoT-based experimentation

The present experimental investigation quantify the combined effect of triangular cut and semicircular cuts on twisted tape inserts (TSCTT) of DPHE in turbulent regime (4000 ≤ Re ≤ 18000). Triangular cut (B/Y = 0.5, 0.8, and 1.1) on the neutral axis along with semicircular cut on the edges have been made on the insert used. The semicircular cut diameter taken 4 mm, 6 mm, and 8 mm on the twisted tape of twist ratios(x/b) of 4.5, 5.5, and 6.5. To minimize error and to promote automation the internet of things approach has been utilized to measure additional input and output characteristics, as well as cold and hot flow rates. It has been found that IoT approach provides more reliable results due to decrease in human interface. The outcomes reveals substantial enhancement in the thermohydraulic performance metrics with the specified modification in the twisted tape. In comparison to other complex type of cut, TSCTT with x/b = 4.5, φ = 8 mm and B/Y = 1.1 achieves the competitive augmentation in the Nusselt number and friction factor. The highest TPF observed within the investigation's range is 1.57.

Hydrodynamic and thermal entrance region assessment of turbulent flow through a circular tube with a tight-fit twisted tape insert, considering multifarious operating conditions and pitch ratios

Hydrodynamic and thermal entrance region assessment of turbulent flow through a circular tube with a tight-fit twisted tape insert, considering multifarious operating conditions and pitch ratios

Heat transfer enhancement in heat exchangers with V-cut twisted tape inserts: A review

Heat transfer enhancement in heat exchangers with V-cut twisted tape inserts: A review

Numerical Study of New Small-twist Tape Insert on Heat Transfer and Pressure Drop for Laminar Flow Inside Circular Pipe

In this study, thermal performance of the laminar flow inside pipe with proposed small twisted tape insert is studied numerically by using computational fluid dynamic software. The proposed insert consists of three- and five-small twisted tapes insert that are arranged in radially symmetry pattern. These group of inserts are then arranged along the pipe with gap spacing to generate continuous flow disturbance. The inserts are proposed to be modelled as zero-thickness layer to reduce the computational cost. The proposed zero-thickness model is validated by compare the with the results of 1mm-model and reference experimental results. The zero-thickness model is then implemented on the proposed insert design for numerical study. Compare with plain twisted tape insert, Nusselt number of the new design is increases by the range of approximately 0.07-42.7% for three-small tapes design, and 4.7-48.0% for five-small tapes design. Performance evaluation criteria (PEC) of present design ranging from 2.2-3.7 for three-small tapes design, and 2.65-3.65 for five-small tapes design. The proposed insert is found to have more advantage over plain twisted tape at lower Reynolds number, reflected by more significant increase in PEC at lower Reynolds number. From the result of friction factor and PEC, the optimum gap distance of insert group is found to be .