Numerical Simulation of Fluid Flow and Heat Transfer Under Flow Fluctuation Condition in Horizontal Tube

2010 ◽  
Author(s):  
Yusheng Liu ◽  
Puzhen Gao ◽  
Dianchuan Xing
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Nuclear Power ◽  
Cfd Simulation ◽  
Horizontal Tube ◽  
Heat Fluxes ◽  
Practical Significance ◽  
Flow And Heat Transfer ◽  
Flow Fluctuation ◽  
Computational Fluid Dynamics Cfd

Fluctuating flow is widely presented in nuclear power plant operating procedure. When the fluctuating flow occurs in the loop, the fluid flow and heat transfer in the core will be affected, which makes the study of flow fluctuation have more practical significance. With computational fluid dynamics (CFD), characteristics of fluid flow and heat transfer are numerically simulated in a horizontal tube under periodical fluctuating flow. The influences of different factors on the fluid flow and heat transfer are analyzed. The simulation results of steady flow and heat transfer in horizontal tube agree with the traditional empirical correlations’ results, which validates the feasibility of doing this research using CFD simulation. The horizontal tube fluctuation flow and heat transfer with different flow fluctuation periods, fluctuation relative amplitudes and heat fluxes are numerically simulated. The results show that the smaller the flow fluctuation period is, the larger the flow fluctuation relative amplitude we get, and the more evident influence of flow fluctuation on fluid flow and heat transfer can be found. The larger the heat flux is, the larger amplitude of temperature fluctuation of fluid will be. What is more, there is a lag in phase between friction coefficient and velocity, which is not presented between heat transfer coefficient and velocity.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

scholarly journals Numerical analysis of heat transfer in air-water heat exchanger with microchannel coil

2019 ◽  
Vol 95 ◽  
pp. 02004
Author(s):  
Vladimir Glazar ◽  
Anica Trp ◽  
Kristian Lenic ◽  
Fran Torbarina
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Numerical Analysis ◽  
Flow Direction ◽  
Heat Fluxes ◽  
Experimental Investigations ◽  
Flow And Heat Transfer ◽  
Working Parameters

This paper presents numerical analysis of fluid flow and heat transfer in the heat exchanger with microchannel coil (MCHX). In accordance with previously published experimental results, 3D mathematical model has been defined and appropriate numerical simulation of heat transfer has been performed. Geometry and working parameters of cross-flow air-water heat exchanger with microchannel coil, installed in an open circuit wind tunnel and used in experimental investigations, have been applied in numerical analysis in order to validate the mathematical model. 3D model with air and water fluid flow and heat transfer domains has been used, as it gives more precise results compared to models that assume constant temperatures or constant heat fluxes on the pipe walls. Developed model comprised full length of air and water flows in the heat exchanger. Due to limitations of computational capacity, domain has been divided in multiple computational blocks in the water flow direction and then solved successively using CFD solver Fluent. Good agreement between experimentally measured and numerically calculated results has been obtained. The influence of various working parameters on heat transfer in air-water heat exchanger has been studied numerically, followed with discussion and final conclusions.

A Comparative Study of Flow Boiling in a Microchannel With Piranha Pin Fins

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
X. Yu ◽  
C. Woodcock ◽  
Y. Wang ◽  
J. Plawsky ◽  
Y. Peles
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Flow Conditions ◽  
Pressure Drops ◽  
Flow And Heat Transfer ◽  
Pin Fins

In this paper, we report on the recent development of an advanced microscale heat sink, termed as piranha pin fin (PPF). A 200 μm deep microchannel embedded with PPFs was fabricated and tested. Fluid flow and heat transfer performance were evaluated with HFE7000 as the working fluid. The surface temperature, pressure drop, heat transfer coefficient, and critical heat flux (CHF) conditions were experimentally obtained and discussed. A 676 W/cm2 CHF was achieved based on the heater area and at an inlet mass flux of 2460 kg/m2 s. Microchannels with different PPF configurations were investigated and studied for different flow conditions. It was found that a microchannel with PPFs can dissipate high heat fluxes with reasonable pressure drops. Flow conditions and PPF configuration played important roles for both fluid flow and heat transfer performances. These studies extended knowledge and provided useful reference for further PPF design in microchannel for flow boiling.

CFD Simulation of Supercritical LNG Heat Transfer in a Horizontal Tube of an Intermediate Fluid Vaporizer

2017 ◽  
Author(s):  
Shuangqing Xu ◽  
Xuedong Chen ◽  
Zhichao Fan
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Horizontal Tube ◽  
Small Mass ◽  
Maximum Deviation ◽  
Average Deviation ◽  
Flow And Heat Transfer ◽  
Reliable Design

A three-dimensional computational fluid dynamics (CFD) model has been established for the simulations of supercritical LNG heat transfer in a horizontal tube of an intermediate fluid vaporizer (IFV). The influences of inlet pressure and mass flux on heat transfer have been studied. The predictive capabilities of different heat transfer coefficient (HTC) correlations, which is vital for the economic and reliable design of an IFV, have been evaluated. The results indicate that the Jackson correlation gives more accurate HTC predictions for supercritical LNG at the relatively small mass flux, with a maximum deviation of 10% and an average deviation of 6%; while for the cases with larger mass flux, a modification to the Jackson-Hall correlation works well. Detailed flow and heat transfer characteristics and buoyancy effect have also been analyzed. The reported findings would provide insight into the supercritical LNG vaporization process and give guidance to the design optimization of an IFV.

Conjugate Heat Transfer in Two Partial Enclosures Connected by Refrigerator/Heater

2013 ◽  
Vol 860-863 ◽  
pp. 1451-1457
Author(s):  
Di Liu ◽  
Fu Yun Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Volumetric Flow Rate ◽  
Heat Transfer Process ◽  
Heat Fluxes ◽  
Thermal Conductivity Ratio ◽  
Extreme Temperatures ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers ◽  
Heat And Fluid Flow

Natural convection conjugated by two partial enclosures, connected by refrigerator/heater, has been numerically studied. Thick walls facing the opening are heated in one zone and cooled in the other zone respectively by constant heat fluxes. The isothermals, streamlines and heatlines are presented for varied governing parameters, Rayleigh numbers, Ra from 103 to 107, solid thick walls to fluid thermal conductivity ratio λS from 0.01 to 10.0, cavity aspect ratio, Ar from 1.0 to 8.0, and refrigeration coefficient, COR from 0.1 to 10.0. The streamlines and heatlines visualize the real fluid flow and heat transfer process or structures. Anti-clock streamlines are generated in both zones. Variations of extreme temperatures, Tmax or Tmin and dimensionless volumetric flow rate on the opening, M, along with these governing parameters are also presented in tables or figures. Correlations of extreme temperatures with Ra, λS and COR are given for varied Ar. At last, the unified correlations of with those parameters also are presented and analyzed. The results show that the common trends and characteristics of heat and fluid flow independent of Ar for both zones are summarized, though the convection is amplified with increased Ar.

A Parametric Numerical Study of Fluid Flow and Heat Transfer in a Computer Chassis

2015 ◽  
Vol 9 (3) ◽  
pp. 242 ◽  
Author(s):  
Efstathios Kaloudis ◽  
Dimitris Siachos ◽  
Konstantinos Stefanos Nikas
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Study ◽  
Flow And Heat Transfer
Sign in / Sign up

Export Citation Format

Share Document