Improving the heat transfer in annular channels

1972 ◽  
Vol 23 (1) ◽  
pp. 815-817 ◽  
Author(s):  
�. K. Kalinin ◽  
G. A. Dreitser ◽  
V. A. Kuz'minov
Keyword(s):  
Heat Transfer ◽  
Annular Channels

Electrohydrodynamic (EHD) Flow and Convective Boiling Augmentation in Single-Component Horizontal Annular Channels

2000 ◽  
Author(s):  
James S. Cotton ◽  
JenShih Chang ◽  
Mamdouh Shoukri ◽  
Tracey Smith-Pollard
Keyword(s):  
Heat Transfer ◽  
Heat Fluxes ◽  
Electrode Position ◽  
Convective Boiling ◽  
Annular Channels ◽  
Mass Fluxes ◽  
Hfc 134A ◽  
Order Of Magnitude ◽  
Flow Configurations ◽  
Visualization Experiments

Abstract In order to explore the mechanics of EHD induced flow and heat transfer augmentation, an experimental study of the tube-side boiling heat transfer of refrigerant HFC-134a has been conducted in a single-pass, counter-flow heat exchanger. The electrode position was arranged concentric to the tube. Experiments are conducted for inlet qualities of 0% to 60%, mass fluxes from 100 kg/m2s to 500 kg/m2s, heat fluxes of 10 kW/m2 and 20 kW/m2, and applied voltage from 0 kV to 8 kV DC. The threshold of EHD effects were analysed by a proposed dimensional analysis which predicts that the EHD forces become significant when the Dielectric Electric Rayleigh number is of the same order of magnitude as the square of the liquid Reynolds number, Eℓε ≈ Re ℓ 2 . This criterion is supported by experimental evidence. Flow visualization experiments have shown that, when the proposed dimensionless criterion is satisfied, EHD body forces may have a strong influence on the liquid-phase and consequently the flow pattern within the channel. The various flow configurations clearly affect heat transfer and pressure loss and need to be considered in any attempt to identify the effects of an applied electric field.

Heat Transfer in Annular Channel With Continuous Flow Twisting

2010 ◽  
Author(s):  
S. E. Tarasevich ◽  
A. B. Yakovlev
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Boiling ◽  
Annular Channel ◽  
Equivalent Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Diameter ◽  
Subcooled Flow Boiling ◽  
Annular Channels

In paper the experimental results on a heat transfer in annular channels with continuous twisting at length at one- and two-phase flows are observed. For a flow twisting the wire was spirally coiled on the central body of the annular channel (diameter of a wire is equal to annular gap altitude). Results of experimental data of a heat transfer of authors and various researchers at a single phase flow in annular channels with a continuous twisting are analyzed. Sampling of diagnostic variables (equivalent diameter and velocity) is spent and generalizing associations for heat transfer calculation on the concave and convex surfaces in a single-phase phase are offered. Also the technique of definition of temperature of the subcooled flow boiling beginning on surfaces of annular channels with a twisting is offered. Features of boiling, origination of heat transfer crisis and results of visualization of a two-phase flow structure in annular channels with twisting are described.

Numerical Simulations on Turbulent Heat Transfer Characteristics of Supercritical Pressure Fluids

2009 ◽  
Author(s):  
Toru Nakatsuka ◽  
Kazuyuki Takase ◽  
Hiroyuki Yoshida ◽  
Takeharu Misawa
Keyword(s):  
Heat Transfer ◽  
Prediction Accuracy ◽  
Experimental Studies ◽  
Supercritical Pressure ◽  
Turbulent Heat Transfer ◽  
High Heat Flux ◽  
Turbulent Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Annular Channels

As one of next generation nuclear reactors, development of a supercritical pressure water reactor (SCWR) has been performed. In order to design the SCWR, it is necessary to investigate thermal-hydraulic characteristics in the SCWR core precisely. As for those characteristics, many experimental studies have been conducted from the former in each country using circular tubes, annular channels, and the simulated fuel bundles. An objective of this study is to clarify the prediction accuracy of the turbulent heat transfer characteristics in the supercritical pressure fluids for the SCWR design. From the experimental results of the supercritical pressure fluids flowing upward in a vertical circular tube, it was confirmed that the turbulent heat transfer coefficient suddenly decreases under the high heat flux condition. Although many numerical studies have been done in order to confirm the deterioration of turbulent heat transfer in supercritical pressure fluids, it is important to choose a suitable turbulence model to obtain high prediction accuracy. Then, the present study was performed to investigate numerically the effect of turbulent models on the deteriorated turbulent heat transfer.

Investigations on post-dryout heat transfer in bilaterally heated annular channels

2006 ◽  
Vol 33 (2) ◽  
pp. 189-197 ◽  
Author(s):  
W.X. Tian ◽  
S.Z. Qiu ◽  
D.N. Jia
Keyword(s):  
Heat Transfer ◽  
Annular Channels

Experiment of Heat Transfer to Supercritical Water Flowing in Vertical Annular Channels

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Zhendong Yang ◽  
Qincheng Bi ◽  
Han Wang ◽  
Gang Wu ◽  
Richa Hu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Supercritical Water ◽  
Experimental Parameter ◽  
Outer Diameter ◽  
Buoyancy Effect ◽  
Upward Flow ◽  
Downward Flow ◽  
Annular Channels

An experimental study of heat transfer to supercritical water has been performed at Xi'an Jiaotong University with a vertical annular tube. The annular test sections were constructed with an annular gap of 2 mm and an internal heater of 8 mm outer diameter. Experimental parameter covered pressures of 23 and 25 MPa, mass fluxes of 700 and 1000 kg/m2s, and heat fluxes of 200–1000 kW/m2. Experimental data were acquired from downward flow and upward flow, respectively. There were differences of heat-transfer characteristics between the two flow directions. Compared to upward flow, the heat-transfer coefficient increased at downward flow. A strong effect of spacer on heat transfer is observed at locations downstream of the device in the annuli regardless of flow direction. The spacer effect impaired the buoyancy effect at low heat flux, but not for large heat flux. Complex of forced convection and mixed convection in supercritical water is due to various thermophysical properties and the gravity. The affected zone of the spacer effect depends on the flow conditions. The buoyancy effect was analyzed qualitatively in this study and the criterion Gr¯/Re2.7<10-5 for negligible heat-transfer impairment was discussed. Four correlations were compared with the experimental data; the Swenson correlation predicted nearly the experimental data but overpredicted slightly the heat-transfer coefficients.

Experimental and Numerical Investigation of Heat Transfer in Annular Channels With Flow Twisting

2012 ◽  
Author(s):  
S. E. Tarasevich ◽  
V. L. Fedyaev ◽  
A. B. Yakovlev ◽  
I. V. Morenko
Keyword(s):  
Heat Transfer ◽  
Convex Surface ◽  
Annular Channel ◽  
Concave Surface ◽  
Channel Diameter ◽  
Convex Surfaces ◽  
Annular Channels ◽  
Annular Gap ◽  
Phase Water ◽  
Gap Height

In paper the experimental and numerical modeling results of a heat transfer in annular channels with continuous twisting at one-phase water flow are presented. For a flow twisting the wire was spirally coiled on the central body of an annular channel (diameter of a wire is equal to annular gap height). The generalizing associations for heat transfer calculation on the concave and convex surfaces in a single-phase phase are presented. The analysis of features of velocity profiles and temperatures on the concave and convex surfaces are carried out. The heat transfer on a convex surface of an annular channel with a twisting considerably above than the heat transfer on a concave surface. It’s caused by increase of displacement of a maximum of a velocity profile to a concave surface under the influence of mass forces with growth of a twisting extent.

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