Local heat transfer coefficient in helical coils with single phase flow

Hardik, B.K.; Baburajan, P.K.; Prabhu, S.V.

doi:10.1016/j.ijheatmasstransfer.2015.05.069

Cited by 135 publications

(23 citation statements)

References 26 publications

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“…Mostly, the slinky coil has a curvature between 1.6 and 2.5 m −1 which is considered as low curvature [20]. A low-curvature coil has similar characteristics to the straight tube in thermaland hydrodynamics [21,22]. Modification of the pipe surface results in a more turbulent flow structure besides increasing the heat transfer area [23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Thermal Characteristics of Slinky-Coil Ground Heat Exchanger with Discrete Double Inclined Ribs

Ariwibowo

Miyara

2020

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The slinky ground heat exchanger (GHE) is the most widely utilized horizontal-type GHE, however, this GHE has a low curvature coil. The GHE has poor thermal mixing, especially at a low flowrate. At this flowrate, the coil heat exchanger has similar performance to a straight tube heat exchanger. Discrete double-inclined ribs (DDIR) are well known for their good thermal mixing by generating a vortex in straight tubes. In this paper, a numerical analysis of thermal performance for the plain coil and DDIR coil is discussed. It was found that the thermal performance of the DDIR coil was slightly higher than that of the plain coil in laminar flow. In turbulent flow, the DDIR coil was superior to the plain coil only in the first 149-min operation. The first 60-min analysis shows that in laminar flow, the average heat transfer rate in the plain coil is 59 W/m and in the DDIR coil is 60.1 W/m. In turbulent flow, the average heat transfer rate is 62 W/m, and the plain coil is 62.3 W/m. The copper DDIR coil material produced a better heat transfer rate than that of the composite and High-Density Polyethylene (HDPE). Sandy clay has the highest heat transfer rate. The influence of ground thermal conductivity on the performance of the GHE is more dominant than convection in the DDIR coil.

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Section: Introductionmentioning

confidence: 99%

Thermal Characteristics of Slinky-Coil Ground Heat Exchanger with Discrete Double Inclined Ribs

Ariwibowo

Miyara

2020

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“…Heat transfer augmentation in active technique requires an external power source, which leads to an increase in the overall cost. Conversely, the passive method involves some enhancement techniques like geometrical variations, insertion of different geometrical shapes, extended surfaces like fins, the addition of nanoparticles to the heat-carrying fluid, etc [3][4][5]. Many investigators follow a line of investigation to improve the heat exchanger performance by using several passive augmentation approaches in coil-in-shell heat exchangers (CSHE).…”

Section: Introductionmentioning

confidence: 99%

Thermal performance enhancement studies on a circular finned coil-in-shell heat exchanger using graphene oxide nanofluid

Rai¹,

Hegde²

2020

SN Appl. Sci.

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The objective of this study is to investigate the effect on heat transfer augmentation by the combined effect of circular fins directly attached to the helical surface of the coil in two different orientations (45° and 90°) and Graphene Oxide nanofluid as a heat transport agent, in a coil-in-shell heat exchanger. The attached circular fins not only act as turbulators on the shell side but could also add to heat transfer from the hot side to the cold side, by a combined mechanism of conduction and convection. The experiment is conducted at constant heat flux, with the cold nanofluid in the coil side and hot air in the shell side. Test runs are taken by varying hot air velocities from 1 m/s to 5 m/s, keeping fixed volume concentration of nanofluid (0.05-0.15%) and flow rate (500 ≤ Re ≤ 5500) one at a time. Experimental results indicated significant enhancement in heat transfer performance for the finned configuration. For 90º and 45º fin orientation-0.15% volume concentration of nanofluid, the maximum heat transfer increase is by 78.46%, and 82.22%, Nusselt number increase is by 32.57%, 60.79% respectively, at a hot air velocity of 3 m/s. The coil side pressure drop and friction factor increased to 32.72% and 24.64% for 0.15% GO nanofluid when compared to pure water at the maximum flow rate. The thermal-hydraulic performance improvement is nearly twofold with 45º fin orientation-GO nanofluid combination.

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“…Hardik et al [12] consequence the effect of helical coil curvature on Reynolds number, Prandtl number, friction coefficient, and Nusselt number. In this study, water was used as a working fluid.…”

Section: Introductionmentioning

confidence: 99%

“…Parameters for considered model at various helix pitches Three different geometrical parameters including coil pitch, coil diameter and coil height are investigated numerically which are shown as models(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in the present study Helix diameter (D C ) is the free parameter which means that in order to keep constant the heat transfer area, by changing the main parameter (like coil pitch, coil diameter or coil height), the free parameter will be changed In order to compare the models in each part, [models (1-4), models (5-8), models (9-12)], the heat transfer area is kept constant, separately…”

mentioning

confidence: 99%

Effects of geometrical and operational parameters on heat transfer and fluid flow of three various water based nanofluids in a shell and coil tube heat exchanger

et al. 2019

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Heating and cooling of a system by heat exchanger Plays an important role in various industries. Improvement of heat transfer in heat exchangers resulted in reducing the size of heat exchanger, and utilizing more compressed heat exchangers with higher efficiency. Using helical/spiral tube is a passive method for improving the performance of heat exchangers due to its low geometry and high heat transfer coefficient. Also, in heat exchangers, one of the most important methods is additives such nanoparticles for liquids and classified as a passive method which does not need any external power like in active methods. The objective of this study is to investigate efficient operational and geometrical parameters. The considered geometrical parameters include helix pitch, coil diameter, and helix height. Also, the effect of using Al 2 O 3 , CuO, SiO 2 nanofluids on thermal performance of the heat exchanger is investigated numerically. The results show that the geometric parameters of the coil have a significant effect on the heat exchangers of the shell and coil.

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Local heat transfer coefficient in helical coils with single phase flow

Cited by 135 publications

References 26 publications

Thermal Characteristics of Slinky-Coil Ground Heat Exchanger with Discrete Double Inclined Ribs

Thermal Characteristics of Slinky-Coil Ground Heat Exchanger with Discrete Double Inclined Ribs

Thermal performance enhancement studies on a circular finned coil-in-shell heat exchanger using graphene oxide nanofluid

Effects of geometrical and operational parameters on heat transfer and fluid flow of three various water based nanofluids in a shell and coil tube heat exchanger

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