The Pressure Drop and Heat Transfer of Flow in Zigzag Micro-Channel With Micro-Orifice

2010 ◽  
Author(s):  
Chengyun Wu ◽  
Hongbo Xu ◽  
Changqing Tian
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Micro Channel ◽  
Two Phase ◽  
Boiling Flow ◽  
Phase Liquid

In this paper, the experimental investigation on friction factor and heat transfer of single phase liquid flow and two-phase boiling flow in single zigzag micro-channel with micro-orifice at inlet has been conducted. The dimension of the micro-orifice is 1mm×0.227mm×0.25mm. The experiment was conducted in copper rectangle zigzag micro-channel with the hydraulic diameter of 0.321mm and the length of 29 mm. The experimental results of friction factor and heat transfer coefficient were provided and the effect of the micro-orifice was discussed. It was found that the friction factor of flow in zigzag micro-channel deviated largely from the predictive value in the laminar flow, while it coincided well with the correlation for turbulent flow. In addition, the variation of local heat transfer coefficient showed that the inlet restrictor has significant effect on heat transfer of boiling flow in micro-channel.

scholarly journals Experimental analysis of the evaporation of a thin liquid film deposited on a capillary heated tube: estimation of the local heat transfer coefficient

2021 ◽  
Vol 2116 (1) ◽  
pp. 012110
Author(s):  
L Cattani ◽  
F Bozzoli ◽  
V Ayel ◽  
C Romestant ◽  
Y Bertin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Heat Conduction Problem ◽  
Thin Liquid Film ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Inverse Heat Conduction Problem ◽  
Two Phase

Abstract The aim of this work is to estimate the local heat flux and heat transfer coefficient for the case of evaporation of thin liquid film deposited on capillary heated channel: it plays a fundamental role in the two-phase heat transfer processes inside mini-channels. In the present analysis it is investigated a semi-infinite slug flow (one liquid slug followed by one single vapour bubble) in a heated capillary copper tube. The estimation procedure here adopted is based on the solution of the inverse heat conduction problem within the wall domain adopting, as input data, the temperature field on the external tube wall acquired by means of infrared thermography.

scholarly journals ENHANCEMENT THE HEAT TRANSFER FOR TWO-PHASE FLOW THROUGH A RECTANGULAR RIBBED VERTICAL CHANNEL

2018 ◽  
Vol 18 (1) ◽  
pp. 92-109
Author(s):  
Riyadh S Al-Turaihi ◽  
Doaa F Kareem
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Two Phase Flow ◽  
Vertical Channel ◽  
Numerical Data ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Two Phase

 The heat transfer coefficient and temperature distribution of two phase flow (water, air)in rectangular ribbed vertical channel was investigated experimentally and numerically inthis work for different values of water and air superficial velocities (0.0421, 0.0842, 0.1158,0.1474 and 0.1684 m/s) and (1.0964, 1.425, 1.644, 1.864 and 2.193 m/s), respectively, atconstant heat flux (120 W). The distribution of temperature along the channel wasphotographed using thermal camera and compared with images for the correspondingcontours which found numerically. The experimental results of heat transfer coefficientcompared with computational fluid dynamics model simulated by Ansys fluent 15.0. Agood agreement has been found between the experimental and numerical data, where thepercentage deviation between the experimental and the numerical results is (1% - 6% ). Theresults showed that, the local heat transfer coefficient increased by adding ribs, it alsoincreased as the velocity of the flow increased.

ENHANCEMENT THE HEAT TRANSFER FOR TWO-PHASE FLOW THROUGH A RECTANGULAR RIBBED VERTICAL CHANNEL

2018 ◽  
Vol 18 (1) ◽  
pp. 92-109
Author(s):  
Riyadh S Al-Turaihi ◽  
Doaa F Kareem
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Two Phase Flow ◽  
Vertical Channel ◽  
Numerical Data ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Two Phase

The heat transfer coefficient and temperature distribution of two phase flow (water, air)in rectangular ribbed vertical channel was investigated experimentally and numerically inthis work for different values of water and air superficial velocities (0.0421, 0.0842, 0.1158,0.1474 and 0.1684 m/s) and (1.0964, 1.425, 1.644, 1.864 and 2.193 m/s), respectively, atconstant heat flux (120 W). The distribution of temperature along the channel wasphotographed using thermal camera and compared with images for the correspondingcontours which found numerically. The experimental results of heat transfer coefficientcompared with computational fluid dynamics model simulated by Ansys fluent 15.0. Agood agreement has been found between the experimental and numerical data, where thepercentage deviation between the experimental and the numerical results is (1% - 6% ). Theresults showed that, the local heat transfer coefficient increased by adding ribs, it alsoincreased as the velocity of the flow increased.

scholarly journals Testing of Heat Transfer Coefficients and Frictional Losses in Internally Ribbed Tubes and Verification of Results through CFD Modelling

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 207
Author(s):  
Sławomir Grądziel ◽  
Karol Majewski ◽  
Marek Majdak ◽  
Łukasz Mika ◽  
Karol Sztekler ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Department Of Energy ◽  
Transfer Coefficients ◽  
Cfd Modelling ◽  
Heat Transfer Coefficients

This paper presents experimental determination of the heat transfer coefficient and the friction factor in an internally rifled tube. The experiment was carried out on a laboratory stand constructed in the Department of Energy of the Cracow University of Technology. The tested tube is used in a Polish power plant in a supercritical circulating fluidized bed (CFB) boiler with the power capacity of 460 MW. Local heat transfer coefficients were determined for Reynolds numbers included in the range from ~6000 to ~50,000, and for three levels of the heating element power. Using the obtained experimental data, a relation was developed that makes it possible to determine the dimensionless Chilton–Colburn factor. The friction factor was also determined as a function of the Reynolds number ranging from 20,000 to 90,000, and a new correlation was developed that represents the friction factor in internally ribbed tubes. The local heat transfer coefficient and the friction factor obtained during the testing were compared with the CFD modelling results. The modelling was performed using the Ansys Workbench application. The k-ω, the k-ε and the transition SST (Share Stress Transport) turbulence models were applied.

Local Heat Transfer Measurements in Turbulent Flow Around a 180-deg Pipe Bend

1987 ◽  
Vol 109 (1) ◽  
pp. 43-48 ◽  
Author(s):  
J. W. Baughn ◽  
H. Iacovides ◽  
D. C. Jackson ◽  
B. E. Launder
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Secondary Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Pipe Bend ◽  
Streamline Curvature

The paper reports extensive connective heat transfer data for turbulent flow of air around a U-bend with a ratio of bend radius:pipe diameter of 3.375:1. Experiments cover Reynolds numbers from 2 × 104 to 1.1 × 105. Measurements of local heat transfer coefficient are made at six stations and at five circumferential positions at each station. At Re = 6 × 104 a detailed mapping of the temperature field within the air is made at the same stations. The experiment duplicates the flow configuration for which Azzola and Humphrey [3] have recently reported laser-Doppler measurements of the mean and turbulent velocity field. The measurements show a strong augmentation of heat transfer coefficient on the outside of the bend and relatively low levels on the inside associated with the combined effects of secondary flow and the amplification/suppression of turbulent mixing by streamline curvature. The peak level of Nu occurs halfway around the bend at which position the heat transfer coefficient on the outside is about three times that on the inside. Another feature of interest is that a strongly nonuniform Nu persists six diameters downstream of the bend even though secondary flow and streamline curvature are negligible there. At the entry to the bend there are signs of partial laminarization on the inside of the bend, an effect that is more pronounced at lower Reynolds numbers.

An Experimental Study of High Rayleigh Number Mixed Convection in a Rectangular Enclosure With Restricted Inlet and Outlet Openings

1987 ◽  
Vol 109 (2) ◽  
pp. 446-453 ◽  
Author(s):  
L. Neiswanger ◽  
G. A. Johnson ◽  
V. P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Rayleigh Number ◽  
Mixed Convection ◽  
Transfer Coefficient ◽  
Heated Surface ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Fluid ◽  
Rectangular Enclosure

Measured local heat transfer data and the results of flow visualization studies are reported for cross-flow mixed convection in a rectangular enclosure with restricted inlet and outlet openings at high Rayleigh number. In this study, experiments using water as the test fluid were conducted in a small-scale test section with uniformly heated vertical side walls and an adiabatic top and bottom. As the flow rate through the enclosure increased, the enhancement of heat transfer, above that for natural convection alone, also increased. The variation of the local heat transfer coefficient over the heated surface was found to be strongly affected by the recirculation of portions of the forced flow within the enclosure. Mean heat transfer coefficients are also presented which were calculated by averaging the measured local values over the heated surface. A correlation for the mean heat transfer coefficient is also proposed which agrees very well with the experimentally determined values. A method of predicting the flow regime in this geometry for specified heating and flow conditions is also discussed.

Local and Average Heat Transfer Characteristics for a Disk Situated Perpendicular to a Uniform Flow

1985 ◽  
Vol 107 (2) ◽  
pp. 321-326 ◽  
Author(s):  
E. M. Sparrow ◽  
G. T. Geiger
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stagnation Point ◽  
Radial Distance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Average Heat ◽  
Radial Profiles

Wind tunnel experiments were performed to determine both the average heat transfer coefficient and the radial distribution of the local heat transfer coefficient for a circular disk facing a uniform oncoming flow. The experiments covered the range of Reynolds numbers Re from 5000 to 50,000 and were performed using the naphthalene sublimation technique. To complement the experiments, an analysis incorporating both potential flow theory and boundary layer theory was used to predict the stagnation point heat transfer. The measured average Nusselt numbers definitively resolved a deep disparity between information from the literature and yielded the correlation Nu = 1.05 Pr0.36 Re1/2. The radial distributions of the local heat transfer coefficient were found to be congruent when they were normalized by Re1/2. Furthermore, the radial profiles showed that the local coefficient takes on its minimum value at the stagnation point and increases with increasing radial distance from the center of the disk. At the outer edge of the disk, the coefficient is more than twice as large as that at the stagnation point. The theoretical predictions of the stagnation point heat transfer exceeded the experimental values by about 6 percent. This overprediction is similar to that which occurs for cylinders and spheres in crossflow.

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