Wire Coil Inserts Research Articles

An in-depth numerical and experimental analysis of wire coil inserts: enhancing thermal performance and fluid flow characteristics in double pipe heat exchangers

An in-depth numerical and experimental analysis of wire coil inserts: enhancing thermal performance and fluid flow characteristics in double pipe heat exchangers

Intensification in Convective Heat Transfer by using Wire Coil Insert

Intensification in Convective Heat Transfer by using Wire Coil Insert

Review on enhancement of heat transfer using coiled wire insert

review on enhancement of heat transfer using coiled wire insert

Experimental Analysis of the Improvement of Heat Transfer in Tube Heat Exchangers via Passive Flow Generators Using Wire Coil Inserts

Abstract Due to their high performance and low-cost demands, internally treated tube heat exchanger surfaces are one of the passive heat transfer enhancements that have caught the industry's attention. At bulk temperatures of 30 °C, an experiment for the insertion of 1 mm and 0.5 mm wire coils with a constant pitch length of 8 mm was carried out in this study. The results on the improvement of heat transfer, including the velocity profile, Nusselt number, friction factor, and thermal enhancement efficiency, were significant. Based on a lower surface temperature recorded beyond the uncertainty value, the results demonstrated an improvement in heat transfer for smaller diameters of wire coil inserts. Interestingly, this improvement is concentrated at low Reynolds numbers, indicating that there may be a point at which an increase in wire thickness does not necessarily result in an equivalent improvement in heat transfer. For both wire thicknesses, a Nusselt number increase of up to 5 times was observed. The friction factor penalty, however, varies depending on the wire thickness, with a higher magnitude (3.2-fold increase) obtained for 1mm as opposed to a 1.8-fold increase for the lower counterpart. This distinction results in the 0.5 mm coil insert gaining better overall performance with an average of 2.2 for the thermal performance ratio, further solidifying the advantage of this technique for enhancing heat transfer in conduits.

ANALISA PERFORMA HEAT EXCHANGER DENGAN PENAMBAHAN VORTEX GENERATOR TIPE WIRECOIL GUNA MENCEGAH ICING PADA KARBURATOR

This study aims to evaluate the influence of vortex wirecoil generators with different pitch variations on heat transfer coefficients, pressure drop, and heat exchanger effectiveness. The method involves experiments with a prototype heat exchanger simulation utilizing exhaust gas from a genset engine to address carburetor freezing issues in aircraft with piston engines, with a parallel flow configuration. The solution proposed involves using vortex generators and shell-and-tube heat exchangers. Shell and tube heat exchangers aim to improve heat exchange efficiency because the fluid flow in the pipes bends, creating significant secondary flow and enhancing heat transfer. This study involves various tools and components, including steel wire as the vortex wirecoil generator with size variations of 1.5, 2.5, and 3.5 cm. Other components consist of galvanized iron cells and copper tubes, as per the research plan. The research results indicate that pitch variations of wirecoil inserts in concentric pipes create turbulent flow that maximizes heat transfer to the air inside the cell. The 3.5 cm wirecoil yields the highest heat transfer coefficient U0 with an average value of 10.4. Additionally, adding variations of vortex wirecoil generators in concentric pipes increases the heat release from the hot fluid in the exhaust gas, enhancing heat exchanger effectiveness. The best effectiveness performance is achieved with a 2.5 cm wirecoil with an average value of 70.09.However, adding pitch variations of wirecoil inserts also disrupts the flow, changing it from laminar to turbulent, with the highest pressure drop occurring with the 3.5 cm wirecoil, with an average value of 17.89 Pa. These findings provide insights into improving efficiency and altering flow in heat exchangers through vortex wirecoil generator variations.

Experimental Investigation of Heat Transfer and Pressure Drop Performance of a Circular Tube with Coiled Wire Inserts

This paper evaluates the thermo-hydraulic performance of a coiled wire passive insert for internal turbulent flow through a circular copper tube test section in an in-tube exchanger. Experiments were carried out using water as the working fluid with Reynolds number ranging from 8000 to 32000. The experimental setup was validated for Nusselt number and friction factor with well-established equations for plain tubes. The average Nusselt number ratios (Nua/Nup) and the friction factor ratios (fa/fp) for the augmented tube case over the plain tube case are reported to range from 1.55 to 1.38 and from 1.513 to 1.583, respectively. The average performance ratios considering equal pumping power criteria are also reported and found in the range of 0.846 to 0.921. The study concludes that coiled wire inserts are suitable for heat transfer augmentation applications where pumping power is of minor concern.

Investigating heat exchanger tube performance: second law efficiency analysis of a novel combination of two heat transfer enhancement techniques

AbstractIn the study, the focus was on evaluating the second law efficiency of a heat exchanger tube operating under continuous heat flux and turbulent flow conditions. The evaluation involved the use of a hybrid GnP and Fe3O4 and modified coiled wire as passive heat transfer enhancement techniques. The primary objective was to investigate the impact of these combined techniques on thermal and hydraulic performance, entropy generation number, Bejan number and second law efficiency. To achieve this, different mass fractions of GnP and Fe3O4 nanoparticles were used in the hybrid nanofluid, along with two forms of modified coiled wire: barrel type and hourglass type. The experimental results indicated that the utilization of hybrid nanofluids and modified helical inserts led to a noticeable improvement in the second law efficiency of the heat exchanger tube. However, it was observed that the differences in entropy generation number and Bejan number between the barrel and hourglass types were not significant, mainly due to higher frictional losses associated with the latter. The highest recorded second law efficiency was 0.416, while the lowest entropy generation number was 0.118. These values were achieved through the combined use of GnP and Fe3O4 with a mass fraction of 0.4% and a barrel-type coiled wire insert with a pitch ratio of 0.5.

Thermal performance enhancement in a double tube heat exchanger using combination of bubble injection and helical coiled wire insert

In this experimental study, a novel approach combining a helical coiled wire (HCW) turbulator and bubble injection (BI) method has been employed to synergistically improve the heat transfer efficiency of double tube heat exchanger. The thermal-frictional characteristics were evaluated by investigating different parameters, including the bubble injection flow rate ranging from 2 to 5 l/min and HCW pitch ranging from 2.5 to 10 mm. For all cases, the thermal enhancement factor (TEF) is employed to determine the optimal configurations. The experimental findings indicate that the introduction of bubble injection, the implementation of the HCW turbulator, and the simultaneous utilization of both methods result in an enhancement of heat transfer by 66 %, 78 %, and 156 % respectively. However, it should be noted that the usage of these methods also leads to an increase in pressure drop. Also, the findings indicate that the integration of two methods yields favorable outcomes in terms of thermal performance when compared to their individual functions. In the optimal scenario, the TEF has the potential to reach a maximum value of 1.28. Furthermore, in order to obtain a more precise comprehension of the relationship between TEF and the parameters under investigation, an empirical equation have been derived and presented.

Energy, exergy, environment and techno-economic analysis of parabolic trough collector: A comprehensive review

Inexhaustible energy sources are the focus of the energy industry for meeting the increased need for energy and reducing carbon emissions. Among various alternatives, harnessing solar energy has become a promising choice around the world. Parabolic trough collectors (PTCs) are an effective way to transform radiant energy into thermal energy, as well as electricity. However, these collectors can be improved by refining their design and tweaking the parameters related to thermal behavior. This may be done either by enhancing the surface area or improving the heat transfer coefficient of the heat carrying medium. These kinds of improvements could be achieved by making the use of nanofluids and by using inserts or fins within the collector tube. The current study provides an extensive review of PTCs from the points of view of their design, along with their thermal characteristics. Different types of nanofluids as the working liquid are investigated and discussed to achieve better PTC performance. Inserts within the collector tube and various design approaches, including fins, twisted tubes, U-shaped tubes, coiled wire inserts, and porous twisted tape inserts, are reviewed and discussed in detail. Finally, based on this review, challenges of PTC applications are described and future research recommendations are proposed.

Experimental study of the thermal characteristic of a double tube heat exchanger with tapered wire coil inserts using PCM-dispersed mono/hybrid nanofluids

ABSTRACT An experimental study involving tapered wire coil inserts in a double-tube heat exchanger using water-based phase change material (PCM)-dispersed mono/hybrid nanofluids is conducted. The effects of the wire coils (WC) with nanofluids on the hydrothermal performance of this system are studied for different coil arrangements: converging wire coils (CWC), diverging wire coils (DWC), and converging-diverging wire coils (CDWC) and different Reynolds numbers. The experimental results indicate that among all the tested coil arrangements, the DWC presents a higher thermal performance factor (TPF) than the other arrangements. Using the DWC, the TPF of the Al2O3+PCM hybrid nanofluid is augmented by 3.98%, 9.61%, and 3.04% as compared to that for the plain wire coil (PWC), CWC, and CDWC, respectively. Besides, the DWC configuration exhibits the minimum entropy generation among all arrangements. For the Al2O3+PCM hybrid nanofluid using the DWC, the entropy generation is decreased by approximately 13.36%, 9.78%, and 5.78% as compared to that of the PWC, CWC, and CDWC at a volumetric flow rate of 15 lpm.

Experimental study of refrigerant condensation heat transfer and pressure drop in horizontal tubes with full and partial coiled wire inserts (CWIs)

The condensation heat transfer coefficient (HTC) and pressure loss in the horizontal smooth and wire-inserted tubes were investigated experimentally. Three different coiled wire inserts (CWIs) of the full length of 1000 mm and partial lengths of 100 mm and 200 mm with 0.8 mm wire thickness and 9.5 mm pitch were studied. The main condenser was a heat exchanger of double pipe type with an 8 mm inner diameter for the refrigerant and an active length of 1 m cooled by water circulating in the annulus. The experiments were conducted for different refrigerant mass velocities within 90–400 kg/m2s and low vapor mass fraction (x < 0.3). The findings revealed that using 1000 mm (full-length), 200 mm, and 100 mm length CWIs improved the HTC by 95%, 40%, and 18%, respectively, over the smooth tube. The HTC per unit pressure drop was also evaluated to assess the performance of full and partial CWIs. The results showed that the HTC per unit pressure loss decreases for all tubes as the mass velocity increases. In addition, the performance of the tubes with CWIs approached that of the smooth tube at higher mass velocities. The ratios of HTC per unit pressure drop at higher mass fluxes for full-length, 200 mm, and 100 mm length CWIs to that of the smooth tube were about 0.4, 0.78, and 0.9, respectively. Although the pressure drop increased almost linearly with the partial CWI length, the HTC increased sharply for the small inserts and gradually for the larger insert lengths. The results obtained for the condensation HTC in smooth and full wire-inserted tubes were also compared with the estimations of well-known correlations in the literature. Furthermore, three new correlations were developed to predict condensation HTC in smooth tubes and tubes with full and partial CWIs. It was shown that the new correlations are more accurate than the available ones.

Hydrothermal and energy-saving performances in a mini-channel heat sink under different wire coil inserts induced swirling flow

Energy conservation and emission reduction are crucial international policies. For micro/mini-channel heat exchangers, improving their thermal performances while consuming as little energy as possible is essential for implementing these policies. Swirling flow stands out as one of the most effective methods for heat transfer enhancement in channel. The wire coil insert, known as an effective swirling flow device, has been widely applied in traditional heat exchangers. However, the effects of different wire coil inserts on hydrothermal and energy-saving performances in the square micro/mini-channel remain unclear. Actually, some wonderful swirling flow generators achieve excellent thermal performance at the cost of sacrificing flow performance and energy conservation. This violates the primary intention of energy conservation and emission reduction. Therefore, this study designs several wire coil inserts with various shapes (square, circle, obverse or reverse trapezoidal, observe or reserve triangular, and hexagonal cross-section shapes) and different pitches (p=3–10.5 mm). Also, a numerical investigation on effects of these wire coil inserts on performances in mini-channels (a single mini-channel with 2×2 mm2 cross-section) at Reynolds number (Re) of 523–1120 is conducted. The results show that the square wire coil insert yields the best heat transfer and comprehensive thermal performance. This is attributed to the fact that wire coil inserts induce swirling flow, which promotes the separation and redevelopment of the flow and thermal boundary layers. Based on this, the effect of wire coil pitch is analyzed thoroughly. Increasing the pitch leads to an increasing first and then decreasing tendency in the comprehensive thermal performance. Overall, the mini-channel with a square wire coil insert at p=6 mm obtains the optimal comprehensive thermal performance factor (∼2.0) for Re = 1120. Moreover, it also presents an acceptable energy-saving performance. In addition, the comparison of this study and several other studies suggests that, square coil insert has great potential to improve comprehensive performance of mini-channel heat exchanger at higher Reynolds number.

Hydrothermal performance of a turbulent nanofluid with different nanoparticle shapes in a duct fitted with various configurations of coiled-wire inserts

This paper examines the turbulent hydrothermal performance of boehmite/water–ethylene glycol (upgamma -mathrm{AlO}(mathrm{OH})/{mathrm{H}}_{2}mathrm{O}-mathrm{EG}) nanofluid flowing through a square duct fitted with various coiled-wire inserts (CWIs) using the finite volume method. The turbulent flow of upgamma -mathrm{AlO}(mathrm{OH})/{mathrm{H}}_{2}mathrm{O}-mathrm{EG} nanofluid is modeled using single-phase and k-varepsilon model. A parametric study is carried out on the effect of Reynolds number (5.0times {10}^{3}le mathrm{Re}le 4.0times {10}^{4}), the geometry of wire (circular, triangular, square, square-diamond, hexagon, octagon, and decagon), nanoparticle volume ratio (0le varphi le 4%), and nanoparticle shapes (blade, brick, cylinder, platelet, and oblate-spheroid) on hydrodynamic and convective heat transfer performance (CHTP). The results showed that the combination between CWI and nanofluid enhances hydrothermal performance. For instance, among the geometries of CWI considered at mathrm{Re}=5.0times {10}^{3}, the square CWI has the highest normalized {mathrm{Nu}}^{mathrm{G}} (referencing empty channel) of 2.58, while the decagon has the lowest value of 1.78. Furthermore, regarding the nanoparticle shapes, the platelet shape has a maximum normalized {mathrm{Nu}}^{mathrm{N}} (referencing base fluid) of 1.53, while the oblate-spheroid has a minimum value of 0.93. Lastly, in terms of application, square and octagon wire-fitted channels are better than empty channel at low mathrm{Re}, as the values of their hydrothermal performance evaluation criteria are greater than unity.

Mixed convection phenomena in tubes with wire coil inserts

A numerical investigation of the flow and heat transfer in a helical coil in laminar and transitional flow regime under mixed convection conditions is presented. The continuous separation and reattachment of the boundary layer caused by the wire coil, that interrupts the flow near the tube all, and the swirl induced by the helical shape of the insert, are identified as the mechanism for heat transfer enhancement. Simulations in the Reynolds number range 200<Re<1500 show the role of mixed convection on heat transfer, as the flow dynamics is sensitive to the buoyancy forced induced by the tube wall heating. The interaction of the secondary swirl flow with the buoyancy motion is investigated in this work, with the aim of clarifying the range where heat transfer could be worsened by the presence of the helical coil. The investigation has been undertaken considering a helical coil of geometrical characteristics e/D=0.071 and p/D=1.5 and water as working fluid. Validation with experimental results of friction factor and Nusselt number is also presented.

Experimental and CFD investigation on heat transfer enhancement in evacuated tube solar collector with coiled wire inserts

ABSTRACT This article presents a novel design of a modified evacuated tube collector fabricated for air heating applications by fixing helical coiled inserts in the vacuum tube. The investigations on modified evacuated tube collector (ETSC-HI) were conducted experimentally and using Computational Fluid Dynamics (CFD) and assessed with the unmodified ETC solar air heater under analogous conditions. The working of the modified evacuated tube collector (ETSC-HI) has been scrutinized under different modes, geometrical parameters, flow parameters and different operating conditions. Experimentally, the influence of these variables on outlet air and thermal efficiency of the modified collector have been studied in detail. The CFD findings have been visualized by plotting graphical contours, vectors and streamlines for various cases. Optimal geometrical parameters for maximum heat transfer coefficient were calculated from the CFD investigations and were considered for further experimental analysis by fixing the coiled wire on the vacuum pipe. It was seen that ETSC-HIperforms better contrasted to the unmodified ETC, registering Nusselt number enhancement of 3.23 times corresponding to P/Dh = 1.5 e/Dh = 0.074 at m = 0.015 kg/s. The highest thermal efficiency for ETSC-HI and unmodified collector are obtained as 70.99% and 64.86% respectively showing significant improvement in the performance. On average, the enhancement of 5.85% in daily average efficiency was seen for the modified ETSC-HI.

Validation of a new methodological approach for the selection of wire-coil inserts in thermal equipment

• New methodology to select wire coils for thermal equipment enhancement. • The estimation of TSP for a given insert categorizes its hydraulic performance. • Method experimentally validated for heat transfer enhancement in a solar collector. • 4 wire-coils selected with differentiated behaviours in their friction factor curves. • Pressure drop and heat transfer tests were performed in collectors with wire coils. The use of wire-coils is especially relevant at low Reynolds numbers (below the critical number to turbulent flow in smooth tubes) according to its inherent positive features such as the advance of transition onset and, if they present suitable geometric characteristics, the establishment of an extended transitional flow in a critical Reynolds number interval [ Re CL - Re CT ], with a predictable friction coefficient and Nusselt number. This paper presents the experimental validation of a new methodology based on the evaluation of a non-dimensional geometry-based parameter: the TSP (Transition Shape Parameter) that allows to predict the friction coefficient evolution with wire-coil inserts and enables to compute the extension of the transitional flow region. The close relationship between hydraulic and thermal performance of wire-coil inserts makes this methodology a valuable tool for selecting the most appropriate wire-coil geometry for a given tubular heat exchanger. It is observed that to promote an increase in heat transfer, the value of the Re CL of the wire coil must be less than the operating Reynolds number range of the equipment. Thus, the Re CL - Re CT interval of the insert should fall into this range. In order to validate the methodological approach, an application to harp-type solar thermal collectors with typical Reynolds number range [40-6000] is presented. Four representative wire-coils, with a wide geometrical range characterized by TSP values of 759, 196, 35.3 and 3.1 (exhibiting significant differentiated behaviours in their friction factor curves and critical Reynolds numbers) were inserted inside the risers of a modified solar collector and experimentally tested at laboratory conditions. Static temperature at different locations at the absorber plate, and pressure drop were measured to obtain friction factor and Nusselt number inside riser covering the laminar, transitional and low-turbulent regions. For a general application with friction factor constraints the most suitable wire-coil geometry is the TSP W 02 = 196 with a range of critical Reynolds number of Re CL = 663 and Re CT = 2286 and Nu ¯ w 02 / Nu ¯ s = 2.21 for Re = 300 - 3000 with f ¯ w 02 / f ¯ s = 3 , 82 . However, for the case study presented (a harp-type solar collector) it is feasible to insert the third wire-coil geometry TSP W 03 = 35.3 due to its early transition, with a range of critical Reynolds number of Re CL = 364 and Re CT = 2324 , and Nu w / Nu s = 1.35 for Re = 300 with a high friction factor augmentation f ¯ w 03 / f ¯ s = 18.84 . This geometry also promotes the highest absorber temperature reduction. The greatest temperature reduction is observed in the range of Reynolds numbers [700-2000], reaching approximately 6 °C, which represents approximately 15%.

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.

Wire-coil insert optimization for high-heat-load/flux synchrotron components

Many synchrotron components require high levels of internal-flow, forced-convection heat transfer to minimize surface temperatures, thermal gradients, and thermally induced stress on high-power beam-interacting surfaces. Wire-coil inserts, physically similar to a common spring, are mechanically fitted inside of component cooling passages to optimize heat transfer performance. They are routinely used in Advanced Photon Source (APS) front end and beamline high-heat-load/flux components to significantly enhance convection heat transfer—up to 400% compared to plain open passages. This has the additional benefit of greatly reducing coolant flow requirements for these components. Using several cooling passage sizes, five different wire sizes, and a range of pitch values, an experimental investigation conducted at the APS has determined the average heat transfer coefficient and resulting pressure loss as a function of water flow rate for 65 different wire-coil inserts. Data from this study have been non-dimensionalized and generalized to yield relationships that can be used to determine the heat transfer performance and resulting pressure loss for any given wire-coil insert that may be used at the APS. Through data reduction, the wire-coil insert characteristic dimensions have also been optimized to yield the highest heat transfer enhancement while minimizing the coolant flow requirements. These generalized expressions for wire-coil inserts will be presented, and they can be used by scientists and engineers during the component design process to evaluate achievable heat transfer performance and associated pressure loss, aiding in the establishment of optimized operating parameters and cooling passage flow distribution schemes.

Investigating thermal performance of combined use of SiO2-water nanofluid and newly designed conical wire inserts

BackgroundThe combined use of augmentation methods plays a significant role to enhance the thermohydraulic performance of thermal systems. This experimental study explores the thermohydraulic performance of a heat exchanger tube with the combined use of SiO2-water nanofluids and newly designed conical wire inserts. MethodsIn this study, a new wire coil insert with different properties from those previously proposed was created. The newly designed inserts were placed in a tube at five distances ranging from 0 to 33.6 mm and SiO2-water nanofluids were used at four volume concentrations (0.5–1.25%). The two step method was used to prepare nanofluids and the experiments were conducted in turbulent flow. Significant findings: The highest heat transfer performance was obtained in the conical wire inserts with pitch ratio of 0, and the least friction loss was obtained in the conical wire inserts with pitch ratio of 4. The best Performance Evaluation criteria was 1.75 at Reynolds number of 3338 and volume concentration of 1.25% for conical wire inserts with pitch ratio of 0. Moreover, the use of nanofluids provided a remarkable heat transfer rate with increased Reynolds number at high volume concentrations, whereas nanofluids at low volume concentrations slightly affected the heat transfer rate and pressure drop. The combination of two techniques presented a promising option for improving the hydrothermal qualities of the heat exchanger.

Exergetic Performance Analysis of Energy Storage Unit Fitted With Wire Coil Inserts

Abstract In a sensible storage system, energy is stored based on the distribution of energy and exergy at the specified conditions. It is believed that the least temperature gradient leads to a higher exergy availability and lower entropy generation in a storage system. An energy storage unit with multiple passages fitted with wire coil inserts is evaluated in the present work by assessing the exergy stored and the entropy generation number for heat transfer fluid (HTF) inlet temperature range of 45–75 °C and HTF flowrate of 0.022–0.029 kg/s. The wire coil inserts have a (p/d) ratio in the range of 0.25–0.75. The maximum exergy storage rate in the energy storage unit is found to be 55.43 W corresponding to an energy storage unit having wire coil insert (p/d = 0.25) at the HTF inlet temperature of 75 °C and HTF flowrate of 0.029 kg/s. Entropy generation number of the system with wire coil inserts (p/d = 0.5), compared to smooth HTF passage, is found to be 42.32% at HTF flowrate and inlet temperature of 0.026 kg/s and 45 °C, respectively.