Heat Transfer and Fluid Flow Characteristics for Newtonian and Non-Newtonian Fluids in a Tube-in-Tube Helical Coil Heat Exchanger

Kushwaha, Naveen; Kumawat, Tara Chand; Nigam, K.D.P.; Kumar, Vimal

doi:10.1021/acs.iecr.9b07044

Cited by 20 publications

(10 citation statements)

References 44 publications

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“…The coiled tubes heat exchangers and steam generators have many applications in different industries, including air conditioning 1 , 2 , chemical processes 3 – 5 , refrigeration 6 , nuclear 7 , 8 , and others. The main reason for using this type of heat exchanger is to improve the heat transfer coefficient due to the effects of centrifugal forces without additional energy sources.…”

Section: Introductionmentioning

confidence: 99%

Robust and universal predictive models for frictional pressure drop during two-phase flow in smooth helically coiled tube heat exchangers

Moradkhani

Hosseini

Mansouri

et al. 2021

Sci Rep

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There is a lack of well-verified models in the literature for the prediction of the frictional pressure drop (FPD) in the helically coiled tubes at different conditions/orientations. In this study, the robust and universal models for estimating two-phase FPD in smooth coiled tubes with different orientations were developed using several intelligent approaches. For this reason, a databank comprising 1267 experimental data samples was collected from 12 independent studies, which covers a broad range of fluids, tube diameters, coil diameters, coil axis inclinations, mass fluxes, saturation temperatures, and vapor qualities. The earlier models for straight and coiled tubes were examined using the collected database, which showed absolute average relative error (AARE) higher than 21%. The most relevant dimensionless groups were used as models’ inputs, and the neural network approach of multilayer perceptron and radial basis functions (RBF) were developed based on the homogenous equilibrium method. Although both intelligent models exhibited excellent accuracy, the RBF model predicted the best results with AARE 4.73% for the testing process. In addition, an explicit FPD model was developed by the genetic programming (GP), which showed the AARE of 14.97% for all data points. Capabilities of the proposed models under different conditions were described and, the sensitivity analyses were performed.

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Section: Introductionmentioning

confidence: 99%

Robust and universal predictive models for frictional pressure drop during two-phase flow in smooth helically coiled tube heat exchangers

Moradkhani

Hosseini

Mansouri

et al. 2021

Sci Rep

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“…This increases heat and mass transfer and leads to narrower residence time distributions. Although numerous studies were previously conducted to investigate the influence of different parameters on the advantages of helical pipes concerning heat and mass transfer (Gelfgat et al 2003;Kockmann 2020;Kurt et al 2015a, b;Kushwaha et al 2020;Liu et al 2005;Mei et al 2020;Mori and Nakayama 1965;Moulin et al 1996;Naphon and Wongwises 2006;Rainieri et al 2012;Rennie and Raghavan 2005;Schmidt 1967;Sedahmed et al 1985;Tohidi et al 2015;Yasuo and Wataru 1965), the characterization of pure mixing of miscible liquids in such apparatus, which is the fundament of the aforementioned transfer processes, has rarely been undertaken. The group of Nigam (Kumar et al 2006;Sharma et al 2017) investigated experimentally and numerically the influence of Reynolds number Re = (u ⋅ d ⋅ )∕ , Schmidt number Sc = ∕( ⋅ ab ) , and curvature ratio on the mixing performances of different coiled geometries, by determination of the residence time.…”

Section: Introductionmentioning

confidence: 99%

Mixing characterization in different helically coiled configurations by laser-induced fluorescence

et al. 2020

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Flow Mixing of two miscible liquids has been characterized experimentally in three different helically coiled reactor configurations of two different lengths in the laminar flow regime at Re = 50…1000. A straight helical coil, a coiled flow inverter, and a new coiled flow reverser have been built, each in a 3-turn and a 6-turn configuration. Laser-induced fluorescence of resorufin has been used to visualize and quantify mixing in cross-sections throughout the reactors. A mixing coefficient is derived from the fluorescence images to allow for a quantitative measure and comparison of the six configurations. It becomes obvious from these experimental results, that an early flow redirection in the helical configuration is beneficial to mixing. The 3-turn reactors achieve nearly the same mixing coefficients as the 6-turn reactors with the double length. This can be explained by the stabilizing effect of the Dean vortices in the helix, which develop during the first two turns. After that, the liquid is trapped inside the vortices and further mixing is inhibited. Accordingly, the coiled flow inverter and coiled flow reverser configurations lead to much higher mixing coefficients than the straight helical coil. The results of these measurements are now used for validation of numerical simulations, which reproduce the geometrical and flow conditions of the experiments. Some exemplary results of these calculations are also shown in this article. Graphic abstract Mass fractions of tracer fluid at Re = 500 in the six examined helix configurations.

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“…The results revealed that pipe curvature, which creates a secondary flow, has a significant impact on flow amounts, whereas the torsion effect is smaller. Kushwaha et al [11] examined the heat transfer and fluid flow properties of Newtonian and non-Newtonian fluids in helical coil heat exchangers computationally. The results demonstrated that in helical coil heat exchanger with baffles in the annulus, f and Nu are greater than in a helix coil heat exchanger without baffles.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the baffles have a substantial impact on heat transport at low Prandtl numbers. [11] Kurnia et al [12] found that adding twisted tape insert in helical heat exchanger can enhance heat transfer performance by up to four times as compared to traditional straight tube heat exchanger. The results of other practical experiments also indicated the possibility of increasing the heat transfer through the heat exchanger by inserting baffle in the heat exchanger shell-type coil [13].…”

Section: Introductionmentioning

confidence: 99%

Effect of Using A Double Coil Tube with Modified Pitch on The Overall Heat Transfer Rate

Najm

Jumaah

Karim

2022

DJES

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The goal of this work was to design a simple and cost-effective technique for improving the performance of heat exchangers, and the emphasis was on the experimental side while not neglecting the necessity of validating our findings with theoretical results using CFD. A new method was used to enhance the heat transfer inside the heat exchanger by using a coil with modified steps, as the published papers did not previously address this method, which proved its effectiveness. For varied coil pitches, the numerical findings were in good agreement with the experimentally obtained results, with an error rate of less than 8%. To compare results and confirm effective correlation between pitch changes, a double coil tube is manufactured with a fixed pitch and a double coil tube with modified pitches, while maintaining the basic design parameters of tube diameter ( ), shell diameter ( ), height of shell ( ), and coil height ( ) in order to try to increase the overall heat transfer coefficient and heat transfer. This new design enhanced heat transfer and total heat transfer coefficient at Reynolds number (400< <2000), with a 22% improvement in overall heat transfer coefficient. The new design of the coil (modified pitch) also gave an improvement in the flow distribution, which generated a higher secondary flow than the traditional pitch coil.

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Heat Transfer and Fluid Flow Characteristics for Newtonian and Non-Newtonian Fluids in a Tube-in-Tube Helical Coil Heat Exchanger

Cited by 20 publications

References 44 publications

Robust and universal predictive models for frictional pressure drop during two-phase flow in smooth helically coiled tube heat exchangers

Robust and universal predictive models for frictional pressure drop during two-phase flow in smooth helically coiled tube heat exchangers

Mixing characterization in different helically coiled configurations by laser-induced fluorescence

Effect of Using A Double Coil Tube with Modified Pitch on The Overall Heat Transfer Rate

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