ANN-Based Correlation for Heat Transfer Coefficient of Gas-Liquid Flow for Different Flow Patterns in Horizontal Pipes

2015 ◽  
Vol 45 (8) ◽  
pp. 815-831
Author(s):  
Karimi Hajir ◽  
Najmeh Sobhanifar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Liquid Flow ◽  
Flow Patterns ◽  
Horizontal Pipes ◽  
Gas Liquid Flow

Numerical Investigation on Bubbly Flow and Heat Transfer Characters in a Liquid-Reactor

2008 ◽  
Author(s):  
Lixin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Liquid Flow ◽  
Nuclear Reactor ◽  
Research Work ◽  
Diameter Distribution ◽  
Flow And Heat Transfer ◽  
Cooling Coils ◽  
Gas Liquid Flow

Gas-liquid flow and heat transfer in a nuclear reactor were investigated by the CFD simulation. The MUSIG model and the mono-disperse model are applied to model the multiphase flow and heat transfer. The comparison with experimental data indicates that the gas-liquid flow and heat transfer in the nuclear reactor could be well captured by the suggested numerical model. The temperature distribution, velocity distribution, bubble diameter distribution in the nuclear reactor and heat transfer coefficient of the cooling coils were analyzed. In addition, the effect of gas generation rate on heat transfer coefficient of the cooling coils was discussed. This research work has provided fundamental understanding of gas-liquid flow and heat transfer in the nuclear reactor as well as the design guidance of the cooling coils.

Experiments on Hydrodynamic and Thermal Behaviors of Thin Liquid Films

2003 ◽  
Author(s):  
B. Ozar ◽  
B. M. Cetegen ◽  
A. Faghri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Liquid Flow ◽  
Local Heat Transfer ◽  
Disk Surface ◽  
Local Heat ◽  
Liquid Films ◽  
Local Heat Transfer Coefficient ◽  
Flow Rates

An experimental study of heat transfer into a thin film of liquid water on a rotating disk is described. The film was introduced from a flow collar at the center of a heated, horizontal disk at a fixed initial film thickness with a uniform radial velocity. Radial distribution of the disk surface temperatures was measured using a thermocouple / slip ring arrangement. Experiments were performed for a range of liquid flow rates between 3.0 lpm and 15.0 lpm corresponding to Reynolds numbers (based on the liquid inlet gap height and velocity) between 238 and 1188. The angular speed of the disk was varied from 0 rpm to 500 rpm. The local heat transfer coefficient was determined based on the heat flux supplied to the disk and the temperature difference between the measured disk surface temperature and the entrance temperature of the liquid onto the disk. The local heat transfer coefficient was seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer was largest for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates. Semi-empirical correlations are presented in this study for the local and average Nusselt numbers. In addition to the heat transfer characterization, the thickness of the liquid film on the disk surface was measured by an optical method, including the characteristics of the hydraulic jump and the subcritical and supercritical flow regions.

Influence of the Surface Treatment of Tubes on the Heat Transfer in Low Pressure Atmosphere

2013 ◽  
Vol 592-593 ◽  
pp. 525-528
Author(s):  
Ladislav Šnajdárek ◽  
Petr Kracík ◽  
Jiří Pospíšil
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Surface Treatment ◽  
Liquid Flow ◽  
Thermal Gradient ◽  
Tube Bundle ◽  
Low Pressure ◽  
Vacuum Pump ◽  
The Heat Transfer Coefficient

This paper presents the current research on heat transfer at a sprinkled tube bundle consisting of smooth tubes and located in a chamber inside of which a low pressure is created by a liquid vacuum pump. It also monitors the changes of the heat transfer coefficient in relation to the speed of sprinkled and sprinkling liquid flow, thermal gradient.

Flow Boiling Heat Transfer and Flow Pattern in Rectangular Channel of Mini-Gap

2004 ◽  
Author(s):  
Yang Yang ◽  
Yasunobu Fujita
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Annular Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Gap Size ◽  
Vapor Quality ◽  
Micro Channels ◽  
Mini Channels

Flow boiling in micro- and mini-channels has attracted much attention in recent years. But the phenomena is such confined channels have not been fully understood and explained. Some conclusions reached by different authors are even contradictory. The present research is trying to study some aspects of flow boiling in mini- and micro-channels. In the present paper boiling heat transfer and two-phase flow patterns in rectangular narrow channels were studied. The gap size of the channel was varied as 2, 1, 0.5 and 0.2 mm with the channel width and length being kept at 20 mm and 100 mm, respectively. In the present mini- and micro-channels, four flow patterns were identified; bubbly, intermittent, wavy and annular flow. They can be also divided into several sub-flow patterns. Flow patterns showed strong channel gap size dependence. Smaller gap size deleted bubbly flow, thus induced simpler flow patterns to shift the annular flow at lower vapor quality. The channels can be divided into two groups depending on the gap size; the larger gap group of 2 and 1 mm, and the smaller gap group of 0.5 and 0.2 mm. The larger gap group showed similar heat transfer behavior as conventional size of tubes. The smaller gap group indicated some peculiar phenomena. Heat transfer coefficient in the smaller gap group was relatively high in the low quality region. Then heat transfer coefficient decreased monotonously with increasing vapor quality. This behavior was considered attributable to the micro-bubble generation in the channel corners and an early partial dryout of thin liquid film. Thus the relationship between heat transfer coefficient and flow pattern should be carefully pursued in micro- and mini-channels to develop heat transfer correlations based on flow patterns.

scholarly journals Friction factor and heat transfer coefficient of R134a liquid flow in mini-channels

2002 ◽  
Vol 22 (16) ◽  
pp. 1821-1834 ◽  
Author(s):  
Bruno Agostini ◽  
Barbara Watel ◽  
André Bontemps ◽  
Bernard Thonon
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Liquid Flow ◽  
Mini Channels

Flow Boiling in Minichannels Under Normal, Hyper and Microgravity: Frictional Pressure Loss and Flow Patterns

2007 ◽  
Author(s):  
D. Brutin ◽  
S. Luciani ◽  
O. Rahli ◽  
Ch. LeNiliot ◽  
L. Tadrist
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pressure Loss ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Flow Patterns ◽  
Local Heat Transfer Coefficient ◽  
Parabolic Flights

We present in this paper, flow boiling results obtained during parabolic flights campaigns. The experimental aim is to obtain the local heat transfer coefficient and the influence of gravity on HFE-7100 flow boiling in minichannels. The hydraulic diameter investigated is: 0.84 mm. The influence of hypergravity and microgravity solely on the frictional pressure loss is evidenced in this paper, and explained using the flow patterns.

Vertical Falling Film Evaporation of Pure Refrigerant HCFC123 in a Plate-Fin Heat Exchanger

2013 ◽  
Author(s):  
Junichi Ohara ◽  
Shigeru Koyama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Patterns ◽  
Falling Film ◽  
Fin Efficiency ◽  
Film Evaporation ◽  
Evaporation Heat ◽  
Falling Film Evaporation ◽  
The Heat Transfer Coefficient

The characteristics of heat transfer and flow patterns are investigated experimentally for the vertical falling film evaporation of pure refrigerant HCFC123 in a rectangular minichannels consisting of offset strip fins. The refrigerant liquid is uniformly supplied to the channel through a distributor. The liquid flowing down vertically is heated electrically from the rear wall of the channel and evaporated. To observe the flow patterns during the evaporation process directly, a transparent vinyl chloride resin plate is placed as the front wall. The experimental parameters are as follows: the mass velocity G = 28∼70 kg/(m2s), the heat flux q = 20∼50 kW/m2 and the pressure P ≈ 100 kPa. It is clarified that the heat transfer coefficient α depends on G and q in the region of vapor quality x ≥ 0.3 while there is little influence of G and q in the region x ≤ 0.3. From the direct observation using a high speed video camera and a digital still camera, flow patterns are classified into five types. Then the empirical correlation equations for evaporation heat transfer coefficient on a vertical falling film plate fin evaporator with minichannels are proposed. From the physical model to evaluate the heat transfer coefficient of the minichannel surface with fins, the characteristics of fin efficiency is clarified that the average value of fin efficiency is about 0.6 and the distributive characteristics of fin efficiency is roughly inverse of heat transfer coefficient characteristics.

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