Twisted Tube Heat Exchanger Research Articles

Investigation of the hydraulic performance heat improvement in 3D pipe by variable of novel twisted tape configurations based on CFD and DoE analysis methods

Enhancing heat transfer is a key area that is closely related to economically efficient systems in various forms of energy saving. The insert of twisted are regarded as thermal method. Goal of the current study was to thoroughly assess how using several approaches at the same time affected the tube heat exchanger’s thermal flow, and thermal enhancement. Different twisted configurations were used such as twisted width, thickness of twisted, turn numbers, and thickness of inward are the modified geometrical parameters. Design of the experiments approach is used to investigate how different geometrical parameters affect the improvement of heat and hydraulic thermofluid pattern in twisted tube heat exchangers as the output variables. The Response Surface technique was also used to investigate and identify various outcome models. Taguchi analysis was applied to optimize the experimental design by investigating changes and executing orthogonal arrays. Additionally, the experimental study design was the orthogonal array L16. The performance parameter was optimized separately, and then the DoE methodology was combined with Taguchi method (TM) and response surface methodology (RMS) to optimize all parameters. In this work, the ideal twisted tape design is discovered through the application of CFD numerical approach in conjunction with RSM and TM. Compared results to traditional pipe, improvement in heat is roughly 42.81 % and 42.72 % for temperature differentials and heat transfer rate performance, respectively.

Numerical investigation of thermal-hydraulic performance enhancement in helical coil heat exchangers with twisted tube geometries

This numerical study examines the thermal-hydraulic performance of helical coil heat exchangers (HCHEs) using twisted tubes versus conventional circular tubes. The effects of Reynolds number (Re = 10,000 to 100,000), pitch length (11, 7.2, 5.5, 3.6 mm), and twisted tube orientation (co-current, counter-current) on heat transfer efficiency and pressure drop were investigated. The results show that higher Reynolds numbers can reduce the Resistance factor by approximately 25 % and improve heat transfer by approximately 35 %. An optimal pitch length of 5.5 mm was found to balance enhanced heat transfer and manageable pumping costs. Twisted tubes demonstrate significant performance advantages at lower Re, with 20–33 % higher Performance Evaluation Criterion (PEC) values compared to circular tubes. However, the benefit diminishes at higher Re, with less than 10 % PEC increase. Implementing counter-current twisted tube configurations leads to approximately 13 % higher Nusselt number and 11 % higher Resistance factor, resulting in a 10 % overall PEC improvement. These findings highlight the superior thermal-hydraulic performance of twisted tubes in HCHE applications, especially at lower Reynolds numbers. Future work could explore different fluids, advanced optimization, energy analysis, cost assessment, and additional geometric parameters to further enhance twisted tube heat exchanger design and performance.

A Computational Study for Evaluating the Performance of Twisted Double Tube Heat Exchangers Fitted with Twisted Tape

Twisted double-tube heat exchangers are promising in improving the heat transfer efficiency on the tube side, decreasing the pressure drop on the shell side, and reducing the size of the equipment. Although offering immense potential, examining heat transfer enhancement techniques inside a heat exchanger. In this study, The thermal-hydraulic characteristics of twisted double-tube heat exchangers fitted with twisted tape inserted have been numerically studied. The Naiver-stokes, energy, and turbulence equations were used to model the fluid flow and heat transfer while the turbulence was with a k- ε model. ANSYS Fluent 23.1 was used to solve the governing equations. The effect of major design elements such as mass flow rate, varied pitches of twisted double tubes and twisted tape inserts was investigated. The hot water was used in the inner tube and the cold water in the outer tube to create a counter-flow apparatus. The Length of the heat exchanger was 1 meter, and the outer and inner diameter was 0.054 and 0.018 m respectively. The thickness of the two tubes was 0.004 m. The twisted ratio of the tubes was tested for =5, 10, and 15 while the twist ratio of the tape was 4, 6, and 8. The findings demonstrated that the utilization of a double twisted tube heat exchanger with a twisted tape insert resulted in enhanced heat transfer in comparison to a plain tube heat exchanger. The numerical analysis revealed that as the twisting ratio drops, the Nusselt number, pressure drop, and overall heat transfer coefficient increase.

Thermal Performance Investigation of Twisted Tube Heat Exchanger

Thermal Performance Investigation of Twisted Tube Heat Exchanger

A Review Study for a Twisted Tube Heat Exchanger

They are considering the increasing demand and urgent need in different industries and the importance of heat exchangers imposed the development of heat exchangers to increase heat transfer and increase general performance, reducing volume and cost. The essential heat exchanger used in many industries is the double tube heat exchanger. This type has been distinguished by its simplicity and wide use in recent years. Several improvement methods have been applied, including passive, active, and compound techniques. Passive technologies change the geometry of heat exchangers and are one of the most effective processes to increase overall heat performance. Besides, the hybridization of flow liquids is one of the most critical approaches to increase heat transfer as nanofluids. This review discusses and analyzes the evolution of heat exchangers and methods for improving passive heat transmission. In addition, experimental and numerical research that used nanofluids in heat exchangers was discussed. Moreover, different twisted shapes of the heat exchanger tubes (elliptical and oval, square, and triangle) were studied, which generated secondary eddy flow that increases the intensity of turbulence and mixing, thus improving heat transfer. Also, additives inside heat exchanger tubes include twisted tapes, ribs, and conical rings. The engagement between the Nusselt number and the coefficient of friction was also offered.

Study on Flow and Heat Transfer Performance of Molten Salt Based Nanofluids in Shell and Twisted Tube Heat Exchanger with Shutter Baffle

Study on Flow and Heat Transfer Performance of Molten Salt Based Nanofluids in Shell and Twisted Tube Heat Exchanger with Shutter Baffle

Improved heat recovery using twisted tube exchanger technology

The geometrical features of twisted tube exchangers enhance the thermo-hydraulic performance for the same fluid velocity compared to conventional heat exchangers. The benefit of its use becomes evident in design as the required heat duty is transferred with smaller surface area for even lower pressure drop compared with conventional exchangers. This work introduces the development of a thermohydraulic model for the twisted tube geometry that relates pressure drop and heat transfer coefficient. Aspect ratio and twist pitch are the parameters that most influence the thermo-hydraulic performance of these exchangers. An alternative sizing approach using the concept of full use of pressure drop step is presented. The application to high viscosity fluids is discussed. The results show a reduction in surface area compared to conventional shell and tube exchangers of up to 45% and a pressure drop reduction of 15%. • An alternative sizing methodology for twisted tube heat exchangers is introduced. • Design approach based on full use of available pressure drop. • Thermo-hydraulic model that relates heat transfer and pressure drop is developed. • Reduced size and pressure drop compared with conventional exchangers.

Design, Fabrication and Performance of Twisted Tube Heat Exchanger

Abstract: Heat exchangers are very much essential industrial as well as domestic equipment usedeveryday. The fundamental basis for this statistic is shell and tube technology is a cost effective, proven solution for a wide variety of heat transfer requirements. There are various limitations with technology which include inefficient usage of shell side pressure drop, dead or low flow zones around the baffles where fouling and corrosion can occur, and flow induced tube vibration, which can ultimately result in equipment failure. This paper presents a recent innovation and development of a latest heat exchanger technology, known as Twisted Tube Technology, which has been able to overcome the limitations of conventional technology. This technology provides solution to almost all mentioned problems and provide good overall heat transfer coefficients through tube side enhancements. This paper primarily focuses on thermal analysis on twisted tube Heat exchangers. Keywords: Heat exchangers, Twisted tube technology, conventional technology, thermal analysis

Flow and heat transfer characteristics of liquid metal and supercritical CO2 in a twisted tube heat exchanger

The Lead-cooled Fast Reactors (LFRs) are fast neutron spectrum reactors cooled by molten lead or lead alloys, which are recommended as one of candidates for the next generation of nuclear reactors due to high performance in sustainability, thermal-hydraulics, and security features. As the critical equipment linking the primary circuit and secondary circuit in LFR, the performance of the main heat exchanger plays a significant role in the operating efficiency of the reactor. In order to improve the heat transfer efficiency and optimize the temperature distribution between the coolant in the primary circuit and secondary circuit of LFR, the flow and heat transfer characteristics of fluids in twisted elliptical tube are investigated in the present study, since the specific spiral cross flow is expected occurring in both inside of the tubes and the interfering area outside the tubes. Theoretical calculation is conducted firstly based on the periodical unit model of the twisted tube heat exchanger. Then the numerical simulation is carried out to study the characteristics of fluid and heat transfer in both shell and tube sides. The results show that the cross flow in twisted tubes improves the overall heat transfer performance of the heat exchanger by strengthening the mixing and turbulence of working fluid. Compared with straight tubes, the entire performance evaluating factor of twisted tubes is around 1.596 times. The theoretical and numerical studies are helpful to the design of the main heat exchanger in LFR.

Investigation of thermal flow structure and performance heat transfer in three‐dimensional circular pipe using twisted tape based on Taguchi method analysis

AbstractIn the current investigation, the twisted tape inserts are considered as the augmentation thermal technique, the influence of a variety of twisted tape configurations on pressure drop characteristics, temperature differences, thermal performance of fluid flow structure, heat transfer improvement, and friction factor are numerically evaluated. The changed geometrical parameters employed for this study comprise twisted tape width, twisted tape thickness, number of turns, and inward thickness are the input parameters. Design of experiments method is applied to analyze the influence of latter various types of geometrical parameters on hydraulic thermofluid pattern and heat transfer improvement in the twisted tube heat exchanger as the output variables. For the experimental design optimization Taguchi analysis is based on investigate of alterations and performs the orthogonal arrays (OA). Moreover, the OA L16 is chosen as the plan of experimental study. It is found the best design of twisted tape in this study by using computational fluid dynamics numerical methodology complained with Taguchi method the enhancement in heat transfer and hence the overall performance evaluation factor is higher than 1.2.

A Numerical Study for a Double Twisted Tube Heat Exchanger

The thermal and fluid physiognomies of a double twisted tube heat exchanger was examined numerically. Twisted engineering is a wide-use method to improve heat transfer in heat exchangers. A counter-flow mode utilizing hot water in the inner tube and cold air in the outer tube was considered. This study aims to progress the thermal performance of the double tube heat exchanger by using twisted tubes instead of plane tubes. The heat exchanger was (1m) length, outer diameter (0.05m) and inner diameter (0.025m), both with a thickness (0.004m). It was tested for different values of twist ratios (Tr= 5, 10, and 15 respectively) and Reynolds numbers (Re=5000 to 30000). The Navier - Stockes and energy equations besides the turbulence model in demand for modelling this physical problem. ANSYS Fluent code was used for the numerical simulation. The results showed that the twisted tube heat exchanger showed increasing heat transfer compared with a plain tube heat exchanger. It was found that the cold outlet temperature, pressure drop and effectiveness are increased as the twist ratio increases.

Experimental research on heat transfer and flow resistance properties in spiral twisted tube heat exchanger

An experiment was conducted to gain the heat transfer and flow resistance characteristics of a high-viscosity thermal oil and water in spiral twisted tube heat exchanger. Experimental parameters covered the oil and water mass fluxes of 1000–3000 kg·m−2·s−1, 160–1200 kg·m−2·s−1, respectively; The water and oil inlet temperature of 15℃/60℃, respectively; And shell-side Re < 2050 and tube-side 12,000 < Re < 45,000. In addition, the heat transfer and flow resistance properties of the spiral twisted tube heat exchanger was compared with that of tube-shell heat exchangers of the ordinary and spiral-groove tube. The experimental results suggested that the spiral twisted tube heat exchanger demonstrates an obvious heat transfer enhancement effect in both laminar and turbulent flows than that of two tube-shell heat exchanger. And the experimental data of the heat transfer and flow resistance properties of the spiral twisted tube were compared to the classical and references correlations. Finally, the fitting heat transfer correlation of spiral twisted tube heat exchanger was gained within a deviation of ±10%.

Development of heat transfer and pressure drop correlations in twisted tube heat exchangers

Heat transfer in concentric twisted tubes exchangers has several applications in the chemical and food industry mainly due to its compact structure and high transport coefficients, however, its use has been limited as a consequence of drop pressure. This study reports Nusselt number and friction factor correlations as a function of the dimensionless Dean number as well as Prandtl number, and a torsional step parameter. Simulations were carried out using ANSYS CFX® V16.0 software at workstations belonging to Grupo de Investigación en Materiales Avanzados y Energía of Instituto Tecnológico Metropolitano. Six geometries were developed with SolidEdge® ST9 academic license. Geometry modification, cleanup, and repair were made although DesignModeler® 2019 academic license. Finally Meshing® for discretization. The mesh size independence, and incidence of the turbulence model, and twisting step validated the computational tools use. Correlation numerically showed an increase of 60% average respect to smooth bending tube.

Evaluation of the minimum required length to study improved heat exchangers via computational fluid dynamics

Heat exchangers are fundamental for energy plants and the operation of industrial processes. As a result, active and passive techniques are needed to increase heat transfer and develop efficient and reliable designs. The design of heat exchangers has been based on iterative methods that require experimentation to be validated. These circumstances, added to the development of powerful microprocessors, promote the use of numerical methods to study flow distribution and pressure drop, as well as thermal analyses applying different turbulence models and several coupling speed-pressure schemes. This paper examines flow development through curved and twisted tube heat exchanger by means of a computational fluid dynamics numerical model developed in ANSYS® in order to establish the minimum length required to infer conclusions for the complete exchanger. This work tries to reduce the computational cost while maintaining the balance between desired accuracy and available computational resources. Finally, this study shows that the flow can be considered fully developed after it has traveled 360° inside the helix; after that point, secondary flows and re-circulation regions improve the heat transference in these devices can be verified.

Calculation of Friction Factors and Nusselt Numbers for Twisted Elliptical Tube Heat Exchangers Using Nek5000

Twisted elliptical tube geometries for heat exchanger design are expected to offer significant enhancement in heat transfer with a marginal increase in frictional losses. The presented work focuses on computational fluid dynamics (CFD) simulations of heated molten salt flows through twisted elliptical tube geometries at low modified Froude numbers. The objectives of this work are to evaluate the available correlations at low Froude numbers and to determine the impact of using a small gap to resolve contact points. The spectral element CFD code Nek5000 was used for all simulations, which were performed in periodic domains of triangular and square unit cells surrounding a single tube through a complete twist using an explicit filtering large eddy simulation (LES) method. The simulation methodology was validated by comparing to the experimental data of Tan et al. Excellent agreement was observed for this comparison. The Dzyubenko correlation for transitional flow was evaluated for a range of Froude numbers. This correlation demonstrated good agreement with LES results at high modified Froude number. As Froude number was decreased toward the bounds of the correlation, the agreement worsened. Cases were then simulated at low Froude number, testing the effects of tube spacing. It was determined that the laminar case for the square unit cell is the most affected by increasing gap size, which should be minimized to mitigate the effect. In the triangular unit cell, the laminar flow regime is also more significantly impacted by increasing gap size compared to the turbulent flow regime which was only marginally impacted.

Numerical analysis on performances of shell side in segmental baffles, helical baffles and novel clamping anti-vibration baffles with square twisted tubes shell and tube heat exchangers

Segmental baffles are used in the conventional shell and tube heat exchanger (STHX). Helical baffles can be used in place of segmental baffles, which increase the heat transfer efficiency and lessen the pressure losses. To avoid flow induced vibrations and eliminate stagnant recirculation zones, a new type of clamping anti-vibration baffle is proposed. Three dimensional CFD simulations, have been performed on ANSYS FLUENT to study and compare the pressure drop and heat transfer coefficient between the newly designed clamping anti-vibration baffles with square twisted tubes, helical baffles with cylindrical tubes and conventional segmental baffle with cylindrical tubes. For the numerical comparison whole heat exchangers are modeled, the numerical model shows the thermo-hydraulic performance with good accuracy by comparing it with Kern and Esso methods for single segmental baffles. It is then used to compare the performance of the same heat exchanger with clamping anti-vibration baffles with square twisted tubes (CBSTT-STHX) and helical baffles with cylindrical tubes (HBCT-STHX). CBSTT-STHX has a higher heat transfer coefficient than segmental baffles with cylindrical tubes (SGCT-STHX) and less pressure drop than both helical baffle with cylindrical tube (HBCT-STHX) and segmental baffle with cylindrical tubes (SGCT-STHX), while its comprehensive performance is higher than SGCT-STHX and slightly less than HBCT-STHX.

Numerical study of heat transfer and flow characteristic of twisted tube with different cross section shapes

In the present work, three dimensional numerical study is conducted to investigate the heat transfer and flow characteristics of twisted tubes of different cross section shapes with the Reynolds number ranging from 50 to 2000. The constant wall temperature condition is used in the simulation analysis. The numerical results of twisted square tube are compared with the available previous experimental data. The results indicate that the heat transfer performance of twisted tube is enhanced compared with the smooth tube, while the pressure drop increases as well. One of the key findings is that the transition point of twisted square tube from laminar flow to turbulent flow is identified and located at Re = 500. It is also found that the cross section shape has little effect on the heat transfer of twisted tubes, while it has great influence on the flow pattern. The results also reveal that the twist pitch has remarkable effects on the heat transfer performance of twisted tubes. In addition, the maximum value of PEC of 2.69 is obtained in twisted pentagon tube with twist pitch ratio of 0.17, and the Reynolds number of 350. These results are significant because it will contribute to the development of compact twisted tube heat exchangers.

Axial Stiffness Analysis of Twisted Tubes

In this study, finite element analysis was performed to calculate the axial stiffness of twisted tubes. Experiments were carried out to verify the calculation. Effects of the twist ratio, lead and thickness on the axial stiffness are investigated. It is found that with increasing the twist ratio or decreasing the lead, the axial stiffness of the twisted tube is decreased. A so-called stiffness reduction coefficient for the twisted tubes is given based on the numerical results. With the stiffness reduction coefficient, the twisted tube heat exchangers could be more accurately designed.

3D numerical simulation on the shell side heat transfer and pressure drop performances of twisted oval tube heat exchanger

Twisted oval tube heat exchanger has been widely used in chemical industry field. In the present study, fluid flow and heat transfer characteristics in the shell side of this type of heat exchanger are studied numerically with Realized k–ε model. Influence of the geometrical parameters including twisted pitch length P and aspect ratio A/B on the performance of the shell side are analyzed. Results reflect that Nusselt number and friction factor both increase with the increasing of P and A/B. Their influence on the shell side overall heat transfer performance h/ΔP is also analyzed. It is concluded that the overall heat transfer performance of the shell side increase with the increasing of A/B. But on the aspect of the influence of P, it firstly increases with the increasing of P and then decreases with the increasing of P. Velocity and temperature distributions, stream traces and secondary flow distributions are presented to make the fluid flow and heat transfer characteristics in the shell side clear at the end of the present work. The magnitudes of the total velocity at the self-supporting points are found to be lower and the temperatures are found to be higher than their neighborhoods. Spiral flow can be found in the shell side especially for the cases with A=14mm, B=5mm. The intensity of the spiral flow becomes more and more drastic with the increasing of A/B and the decreasing of P. Analysis of the secondary shows that the magnitude of the secondary flow increases with the increasing of A/B and decreases with the increasing of P. Irregular secondary flow can also be found around the helixes which are formed by the twisting of the oval sections.

Experimental Study of Fouling Resistance in Twisted Tube Heat Exchanger

This paper discusses fouling of a twisted tube heat exchanger under different conditions of fluid velocity and heat input. The fluid velocity was varied from 0.5 to 2.0 m/s, whereas the heat input to the heat exchanger was varied from 200 to 800 W. The experimental results show that for low fluid velocity of 0.5 m/s, the fouling resistance showed noticeable variation with respect to heat input, whereas for high velocity ranges, that is, 1.0–2 m/s, the variation in fouling resistance is less. The fouling in twisted tube steadily increases with time for different values of heat input from 1000 min onward for fluid velocity in the range from 1.0 to 2.0 m/s. It is also observed that fouling resistance curves overlap for various values of heat input. During the initial 1000 min of the test duration, the maximum fouling in a twisted tube heat exchanger decreases with increase in fluid velocity from 1.0 to 2.0 m/s. This behavior of the fouling rate can be attributed to the fact that at higher fluid velocity, flow becomes turbulent, and this in turn flushes the fouling particles. The time-series correlations for the fouling resistance are found to be logarithmic in nature.