The study of heat transfer coefficient while flow unsaturated liquid through the tube at pressure below critical

2020 ◽  
Vol 34 (27) ◽  
pp. 2050299
Author(s):  
J. R. Mammadova ◽  
A. P. Abdullayev ◽  
R. M. Rzayev ◽  
S. H. Mammadova ◽  
R. A. Sultanov
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Free Convection ◽  
Transfer Coefficient ◽  
Temperature Regime ◽  
Vertical Tube ◽  
Criterion Equation

This work studies the temperature regime of the wall while up and down moving of the unsaturated liquid in the vertical tube at pressure below critical and influence of free convection on the heat transfer. The boundary of influence free convection on heat transfer is determined and summarized as a criterion equation.

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.

scholarly journals Computational analysis of convective heat transfer across a vertical tube

2021 ◽  
Vol 49 (4) ◽  
pp. 932-940
Author(s):  
Jashanpreet Singh ◽  
Chanpreet Singh
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Computational Analysis ◽  
Numerical Data ◽  
Vertical Tube ◽  
Steady State Condition ◽  
Convective Mode ◽  
Good Agreement

This paper deals with the numerical investigation of the convective mode of heat transfer across a vertical tube. Experiments were carried out using air as a fluid in a closed room by achieving a steady-state condition. Implicit scheme of finite difference method was adopted to numerically simulate the free convection phenomenon across vertical tube using LINUX based UBUNTU package. Numerical data were collected in the form of velocity, temperature profiles, boundary layer thickness, Nusselt number (Nu), Rayleigh's number (Ra), and heat transfer coefficient. The results of the Nusselt number showed a good agreement with the previous studies. Results data of heat transfer coefficient indicate that there were some minor heat losses due to radiation of brass tube and curvature of the tube.

Influence of Overweight Acceleration on Heat Transfer of Hydrocarbon Fuel in a Vertical Tube at Supercritical Pressures

2019 ◽  
Author(s):  
Lulu Lv ◽  
Yanchen Fu ◽  
Bensi Dong ◽  
Jie Wen ◽  
Guoqiang Xu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Buoyancy Force ◽  
Hydrocarbon Fuel ◽  
High Heat ◽  
Vertical Tube ◽  
High Heat Flux ◽  
Gravitational Acceleration

Abstract The presented study numerically investigated the heat transfer characteristics of supercritical hydrocarbon fuel RP-3 in a vertical tube under overweight conditions with gravitational accelerations from 1g to 5g. The model was simplified as a vertical tube with the diameter of 1.8mm and the length of 250mm. Constant heat flux was applied to the wall, varying from 200kW/m2 to 700kW/m2. Variations of wall temperature and heat transfer coefficient under overweight conditions were obtained by simulation. The dimensionless buoyancy and thermal acceleration under different conditions were analyzed. The results show that the heat transfer is normal at low heat flux, while two types of heat transfer deterioration were observed in both upward and downward supercritical flow at high heat flux. The heat transfer coefficient of downward flow is generally higher than upward flow, and the difference between them becomes larger with the increase of gravitational acceleration. At high heat flux, when bulk temperature reaches the pseudo-critical temperature, the thermal acceleration will increase by 50% leading to the deterioration of heat transfer. However, after the pseudo-critical point, both buoyancy force and thermal acceleration decrease to negligible. The rise in gravitational acceleration enhances buoyancy force, but has no impact on the thermal acceleration. Based on the numerical analysis, two different criterion, Bo* and Kv, for supercritical RP-3 are obtained to present the influence of buoyancy and thermal acceleration.

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