Boiling Heat Transfer on Small Diameter Tube Bundle

An experimental study has been carried out using a tube bank representing a section of a tube bundle. The bank comprised 3 columns each of 10 stainless steel electrically heated tubes of 3mm outside diameter with pitch to diameter ratio of 1.5 in an in-line arrangement. Flow rate through the test section was controlled. Each tube in the central column was instrumented to permit determination of the tube temperature and heat flux, hence permitting calculation of the heat transfer coefficient. These tests were carried out using distilled water at nominal atmospheric pressure over a range of heat fluxes between 6 - 21 kW/m2. Results of the heat transfer tests are presented and compared with correlations used for conventionally sized bundles. Correlations developed for large tube bundle overestimate the experimental results.

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Comparison of the Three–Zone Evaporation Model with Boiling Heat Transfer in a Compact Tube Bundle

International Journal of Engineering Research in Africa ◽

10.4028/www.scientific.net/jera.5.53 ◽

2011 ◽

Vol 5 ◽

pp. 53-63

Author(s):

Ebenezer Adom ◽

Peter Kew ◽

Keith Cornwell

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Tube Bundle ◽

Small Diameter ◽

Heat Fluxes ◽

Evaporation Model ◽

Mass Fluxes ◽

Micro Channels ◽

Three State Model ◽

Outside Diameter

The recent interest in boiling heat transfer in small diameter tubes has led to the study of boiling heat transfer outside a compact tube bundle of diameter 3mm. The bank comprised 3 columns each of 10 stainless steel electrically heated tubes of 3mm outside diameter, with pitch to diameter ratio of 1.5 in an in-line arrangement. These tests were carried out using distilled water and R113 at nominal atmospheric pressure over a range of heat fluxes between 4-21 kW/m2 for mass fluxes from G=5.6 - 32.8 kg/m2s. The recent three-zone evaporation model developed by Thome, Dupont and Jacobi for boiling inside micro channels was used to compare with experimental results as photographic study showed that bubbles confined within the bundle were responsible for the heat transfer enhancement observed. It was observed that the three state model was promising in its application to the bundle arrangement as the confinement number Co for bundle has been shown to be in the order of 0.63

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Measurement of Condensation Curves for Dropwise Condensation of Steam at Atmospheric Pressure

Journal of Heat Transfer ◽

10.1115/1.3245632 ◽

1983 ◽

Vol 105 (3) ◽

pp. 633-638 ◽

Cited By ~ 23

Author(s):

I. Tanasawa ◽

Y. Utaka

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Atmospheric Pressure ◽

Heat Fluxes ◽

Dropwise Condensation ◽

Maximum Heat ◽

Transfer Block ◽

Peak Heat Flux ◽

The One ◽

The Heat Transfer Coefficient

Condensation curves for dropwise condensation of steam at atmospheric pressure were measured for the range of surface subcooling between 0.5 and 180 K using a heat transfer block having a concave spherical condensing surface. The heat transfer coefficient remained constant with the increase of surface subcooling up to about 10 K, and then it decreased. The maximum heat fluxes were found to be between 9.3 and 12.2 MW/m2. Dropwise condensation could be observed at a surface subcooling larger than the one corresponding to the peak heat flux, but shortly the mode of condensation shifted to pseudo-film or on-ice condensation.

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Systematic heat transfer measurements in highly viscous binary fluids

Heat and Mass Transfer ◽

10.1007/s00231-021-03087-w ◽

2021 ◽

Author(s):

Ann-Christin Fleer ◽

Markus Richter ◽

Roland Span

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Volatile Component ◽

Test Tube ◽

Heat Fluxes ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Low Viscosity ◽

The Heat Transfer Coefficient

AbstractInvestigations of flow boiling in highly viscous fluids show that heat transfer mechanisms in such fluids are different from those in fluids of low viscosity like refrigerants or water. To gain a better understanding, a modified standard apparatus was developed; it was specifically designed for fluids of high viscosity up to 1000 Pa∙s and enables heat transfer measurements with a single horizontal test tube over a wide range of heat fluxes. Here, we present measurements of the heat transfer coefficient at pool boiling conditions in highly viscous binary mixtures of three different polydimethylsiloxanes (PDMS) and n-pentane, which is the volatile component in the mixture. Systematic measurements were carried out to investigate pool boiling in mixtures with a focus on the temperature, the viscosity of the non-volatile component and the fraction of the volatile component on the heat transfer coefficient. Furthermore, copper test tubes with polished and sanded surfaces were used to evaluate the influence of the surface structure on the heat transfer coefficient. The results show that viscosity and composition of the mixture have the strongest effect on the heat transfer coefficient in highly viscous mixtures, whereby the viscosity of the mixture depends on the base viscosity of the used PDMS, on the concentration of n-pentane in the mixture, and on the temperature. For nucleate boiling, the influence of the surface structure of the test tube is less pronounced than observed in boiling experiments with pure fluids of low viscosity, but the relative enhancement of the heat transfer coefficient is still significant. In particular for mixtures with high concentrations of the volatile component and at high pool temperature, heat transfer coefficients increase with heat flux until they reach a maximum. At further increased heat fluxes the heat transfer coefficients decrease again. Observed temperature differences between heating surface and pool are much larger than for boiling fluids with low viscosity. Temperature differences up to 137 K (for a mixture containing 5% n-pentane by mass at a heat flux of 13.6 kW/m2) were measured.

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Heat Transfer to Supercritical Water in Vertical Annular Channel and 3-Rod Bundle

Volume 3: Thermal Hydraulics; Current Advanced Reactors: Plant Design, Construction, Workforce and Public Acceptance ◽

10.1115/icone17-75212 ◽

2009 ◽

Cited By ~ 6

Author(s):

V. G. Razumovskiy ◽

Eu. N. Pis’mennyy ◽

A. Eu. Koloskov ◽

I. L. Pioro

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Supercritical Water ◽

Annular Channel ◽

Heat Fluxes ◽

Inlet Temperature ◽

Outlet Temperature ◽

Rod Bundle ◽

Temperature Regimes ◽

Outside Diameter

The results of heat transfer to supercritical water flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of the tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 800 to 3000 kg/m2·s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2 (heat flux rate up to 2.5 kJ/kg). Temperature regimes of the annular channel and 3-rod bundle were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of fuel bundles.

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Effect of Open Micro-Channels on External Condensation Heat Transfer

ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2016-8062 ◽

2016 ◽

Author(s):

Brandon Hulet ◽

Andres Martinez ◽

Melanie Derby ◽

Amy Rachel Betz

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Film Thickness ◽

Transfer Coefficient ◽

Heat Fluxes ◽

Condensation Heat Transfer ◽

Dropwise Condensation ◽

Micro Channels ◽

Lower Heat ◽

The Heat Transfer Coefficient

This research experimentally investigates the heat transfer performance of open-micro channels under filmwise condensation conditions. Filmwise condensation is an important factor in the design of steam condensers used in thermoelectric power generation, desalination, and other industrial applications. Filmwise condensation averages five times lower heat transfer coefficients than those present in dropwise condensation, and filmwise condensation is the dominant condensation regime in the steam condensers due to a lack of a durable dropwise condensation surface. Film thickness is also of concern because it is directly proportional to the condenser’s overall thermal resistance. This research focuses on optimizing the channel size to inhibit the creation of a water film and/or to reduce its overall thickness in order to maximize the heat transfer coefficient of the surface. Condensation heat transfer was measured in three square channels and a plane surface as a control. The sizes of the square fins were 0.25 mm; 0.5 mm; and 1 mm, and tests were done at a constant pressure of 6.2 kPa. At lower heat fluxes, the 0.25mm fins perform better, whereas at larger heat fluxes a smooth surface offers better performance. At lower heat fluxes, droplets are swept away by gravity before the channels are flooded. Whereas, at higher heat fluxes, the channels are flooded increasing the total film thickness, thereby reducing the heat transfer coefficient.

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Thermal Analysis and Design Applications of the Spiral Groove Tubes in Condensers

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1070-1072.1705 ◽

2014 ◽

Vol 1070-1072 ◽

pp. 1705-1708

Author(s):

Xiao Lu Wang ◽

Da Yu Huang

Keyword(s):

Heat Transfer ◽

Thermal Analysis ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Thermal Performance ◽

Tube Bundle ◽

Spiral Groove ◽

Analysis And Design ◽

Grooved Tube ◽

The Heat Transfer Coefficient

In this paper, condensation mechanism of the Freon refrigerants outside spiral grooved tube is discussed. The heat transfer coefficient of Freon refrigerants condensation outside spiral grooved tube is obtained. A calculation example of heat transfer coefficient on the tube bundle of condenser with baffle bars is presented. It shows the excellent thermal performance of the spiral groove tubes compared to smooth tubes.

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