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.

Numerical modeling of the influence of bubbles on flow and heat transfer in the descending gas-liquid flow in a pipe

2012 ◽  
Vol 9 (1) ◽  
pp. 131-135
Author(s):  
M.A. Pakhomov
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Liquid Flow ◽  
Bubble Diameter ◽  
Gas Content ◽  
Two Phase ◽  
Eulerian Description ◽  
Flow And Heat Transfer ◽  
Gas Liquid Flow ◽  
The Mathematical Model

The paper presents the results of modeling the dynamics of flow, friction and heat transfer in a descending gas-liquid flow in the pipe. The mathematical model is based on the use of the Eulerian description for both phases. The effect of a change in the degree of dispersion of the gas phase at the input, flow rate, initial liquid temperature and its friction and heat transfer rate in a two-phase flow. Addition of the gas phase causes an increase in heat transfer and friction on the wall, and these effects become more noticeable with increasing gas content and bubble diameter.

Flow and Heat Transfer of Supercritical Co2 in a Vertical Tube Under Ocean Rolling Motion

2021 ◽  
Author(s):  
Dechao Liu ◽  
Shulei Li ◽  
Gongnan Xie ◽  
Youqian Chen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Waste Heat ◽  
Static Condition ◽  
Vertical Tube ◽  
Rolling Motion ◽  
Flow And Heat Transfer ◽  
Maximum Improvement

Abstract In order to explore the fluid flow and heat transfer features of supercritical fluids used in Brayton cycle for waste-heat utilization of marine gas turbines, the effects of ocean rolling motion on thermo-fluidic characteristics of supercritical carbon dioxide (SCO2) in a circular tube are computationally investigated based on a verified turbulence model. It can be found that at a given rolling period, compared to that under static condition, the time-averaged heat transfer capacity is improved by 7.9%, but the onset of the heat transfer recovery is delayed so that the range of the heat transfer deterioration becomes widened. Under the action of the inertial forces, the heat exchange between cooler/denser and warmer/lighter fluids is enhanced, a secondary circulation formed at t/tc = 0.325 and the maximum improvement of section-averaged heat transfer coefficient is 71% at this time. For various periods, the variation trend of time-averaged heat transfer coefficient for SCO2 shows a parabolic, which is distinguishing from conventional fluids. A polarization phenomenon for instantaneous thermal performance can be observed under severe rolling. With rise of the layout height, the time-average heat transfer performance of tube increases monotonously, and the maximum increment is 10.64% in study range.

Fluid Flow and Heat Transfer Analysis of Automotive Radiator Using CFD Tools

2005 ◽  
Author(s):  
V. P. Malapure ◽  
A. Bhattacharya ◽  
Sushanta K. Mitra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Temperature Drop ◽  
Three Dimensional ◽  
Heat Transfer Analysis ◽  
Coolant Temperature ◽  
Flow And Heat Transfer ◽  
Optimization Study

This paper presents a three-dimensional numerical analysis of flow and heat transfer over plate fins in a compact heat exchanger used as a radiator in the automotive industry. The aim of this study is to predict the heat transfer and pressure drop in the radiator. FLUENT 6.1 is used for simulation. Several cases are simulated in order to investigate the coolant temperature drop, heat transfer coefficient for the coolant and the air side along with the corresponding pressure drop. It is observed that the heat transfer and pressure drop fairly agree with experimental data. It is also found that the fin temperature depends on the frontal air velocity and the coolant side heat transfer coefficient is in good agreement with classical Dittus–Boelter correlation. It is also found that the specific dissipation increases with the coolant and the air flow rates. This work can further be extended to perform optimization study for radiator design.

Dynamic Response Analysis of Start-Up Transient in Air Conditioning System

2013 ◽  
Vol 423-426 ◽  
pp. 1577-1588
Author(s):  
Prakob Surawattanawan ◽  
Surasit Polpun
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Parameter Identification ◽  
Transfer Coefficient ◽  
Air Conditioning ◽  
Dynamic Models ◽  
Research Work ◽  
Fault Detection And Diagnosis ◽  
Response Analysis ◽  
Transient Model

Dynamic models of the heating, ventilation and air-conditioning (HVAC) systems in a temperature controlled room are very useful for controller design, commissioning, and fault detection and diagnosis. A transient model is a set of time differential equations in mass, energy and momentum balances. These transient equations contain parameter values for validation. The parameter such as thermal capacitances of the room chamber, heat transfer coefficient of room panel, heat transfer coefficient of evaporator are difficult to determine because they are related to unsteady condition and have to be considered to account for room energy storage. Many researchers have been studied the transient model for HVAC system by setting an assumption that there parameters are already known. None of them has been investigated into the parameter identification. This research work focused into the parameter identification technique to determine the thermal capacitances of the room chamber, heat transfer coefficient of room panel, and heat transfer coefficient of evaporator. The transient model of a refrigeration unit for an air-conditioned room was analyzed. Block diagram technique along with computer simulation technique were applied for the task. Experimental tests were setup to validate this model.

Numerical and experimental analysis of microchannel heat transfer for nanoliquid coolant using different shapes and geometries

2014 ◽  
Vol 229 (11) ◽  
pp. 2056-2065 ◽  
Author(s):  
Harry Garg ◽  
Vipender Singh Negi ◽  
Nidhi Garg ◽  
AK Lall
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Transfer Coefficient ◽  
Experimental Analysis ◽  
High Heat ◽  
Heat Transfer Analysis ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
High Heat Transfer Coefficient

As part of the liquid cooling, most of the work has been done on fluid flow and heat transfer analysis for flow field. In the present work, the experimental and numerical studies of the microchannel the fluid flow and heat transfer analysis using nanoliquid coolant have been discussed. The practical aspects for increasing the high heat transfer coefficient from conventional studies and the different geometries and shapes of the microchannel are studied. The Aspect Ratio has significant effect on the microchannels and has been varied from AR 2, 4 and 8 to choose the optimum one. Three different fluids, i.e. de-ionized water, ethylene glycol, and a custom nanofluid are chosen for study. The proposed nanofluid almost interacts as another solid and has reduced thermal resistance, friction effect, and thus it almost vanishes high hot spots. Experimental analysis shows that the proposed nanofluid is excellent fluid for high rate heat removals. Moreover, the performance of the overall system is excellent in terms of high heat transfer coefficient, high thermal conductivity, and high capacity of the fluid. It has been reported that the heat transfer coefficient can be increased to 2.5 times of the water or any other fluid. It was also reported that the AR 4 rectangular-shaped channels are the optimum geometry in the Reynolds number ranging from 50 to 800 considering laminar flow. Examination and identification is based upon the practical result that includes fabrication constraints, commercial application, sealing of the system, ease of operation, and so on.

Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet

2003 ◽  
Author(s):  
Arun K. Saha ◽  
Sumanta Acharya ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Leakage Flow ◽  
Pressure Side ◽  
Average Heat Transfer Coefficient ◽  
Tip Leakage Flow ◽  
Average Heat ◽  
Flow And Heat Transfer ◽  
Blade Tip

A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure side winglet exhibits a significant reduction in the leakage flow strength and an associated reduction in the aerodynamic loss. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. The winglet reduces the average heat transfer coefficient by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and only a 0.5% reduction in the pressure ratio is achieved with the winglet with virtually no reduction in the average heat transfer coefficient.

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.

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