Free Convection Effects on Laminar Forced Convective Heat Transfer in a Horizontal Isothermal Tube

1982 ◽  
Vol 104 (1) ◽  
pp. 145-152 ◽  
Author(s):  
W. W. Yousef ◽  
J. D. Tarasuk
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Free Convection ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Temperature Difference ◽  
Reynolds Numbers ◽  
Transfer Data ◽  
Forced Convective Heat Transfer ◽  
Nusselt Numbers

The influence of free convection due to buoyancy on forced laminar flow of air in the entrance region of a horizontal isothermal tube was investigated. The Graetz numbers ranged form 2.5 to 110.0, the Reynolds numbers ranged from 120 to 1200, the Grashof numbers ranged from 0.8 × 104 to 8.7 × 104, and the ratio L/D was varied from 6 up to 46. The average Nusselt numbers based on the log-mean temperature difference, ranged from 2.0 to 25.9. The heat transfer data were correlated according to the influence of free convection which was found to have a significant effect at points close to the entrance to the tube.

Combined Natural and Forced Convective Heat Transfer In Spherical Annuli

1984 ◽  
Vol 106 (4) ◽  
pp. 811-816 ◽  
Author(s):  
S. Ramadhyani ◽  
M. Zenouzi ◽  
K. N. Astill
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Outer Sphere ◽  
Reynolds Numbers ◽  
Numerical Work ◽  
Low Reynolds Numbers ◽  
Forced Convective Heat Transfer ◽  
Nusselt Numbers ◽  
Different Temperatures

This paper presents numerical finite difference solutions of combined natural and forced convective heat transfer in spherical annuli. The flow is assumed to enter the annulus through a port in the bottom of the outer sphere and exit through a diametrically opposite port. The spheres are isothermal and at different temperatures. The governing conservation equations are reduced to dimensionless form and the nondimensional parameters of the problem are identified. The influence of these parameters of the problem are identified. The influence of these parameters on the solution is studied. Details of the flow field and temperature field are presented by means of velocity vector and isotherm maps. Circumferential average and local Nusselt numbers are presented and compared with earlier numerical work in which the effects of natural convection were ignored. It is shown that the buoyancy effects can have a very significant impact on the heat transfer and fluid flow, particularly at low Reynolds numbers.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

2019 ◽  
Author(s):  
Yantao Li ◽  
Yulong Ji ◽  
Katsuya Fukuda ◽  
Qiusheng Liu ◽  
Hongbin Ma
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Inlet Temperature ◽  
Experiment Data ◽  
Forced Convective Heat Transfer ◽  
Nusselt Numbers ◽  
Mini Channels ◽  
Heat Transfer Correlations

Abstract In this paper, the forced convective heat transfer of FC-72 was experimentally investigated for various of parameters like velocity, inlet temperature, tube size, and exponential period of heat generation rate. Circular tubes with different inner diameters (1, 1.8 and 2.8 mm) and heated lengths (30–50 mm) were used in this study. The experiment data suggest that the single-phase heat transfer coefficient increases with increasing flow velocity as well as decreasing tube diameter and ratio of heated length to inner diameter. The experiment data were nondimensionalized to study the effect of Reynolds number (Red) on forced convection heat transfer. The results indicate that the relation between Nusselt numbers (Nud) and Red for d = 2.8 mm show the same trend as the conventional correlations. However, the Nud for d = 1 and 1. 8 mm depend on Red in a different manner. The conventional heat transfer correlations are not adequate for prediction of forced convective heat transfer in mini channels. The heat transfer correlations for FC-72 in vertical small tubes with diameters of 1, 1.8 and 2.8 mm were developed separately based on the experiment data. The differences between experimental and predicted Nud are within ±15%.

scholarly journals Experimental Investigation into the Forced Convective Heat Transfer of Aqueous Fe3O4 Nanofluids under Transition Region

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Jie Ma ◽  
Yinchen Xu ◽  
Wenlie Li ◽  
Jiantao Zhao ◽  
Shuping Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Transition Region ◽  
Convective Heat ◽  
Reynolds Numbers ◽  
Axial Distance ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Initial Expectation

The forced convective heat transfer (FCHT) properties of nanofluids, made of Fe3O4 nanomaterials and deionized water, are firstly measured by a self-made forced convective heat transfer apparatus. The nanofluid flows through a horizontal copper tube in the transition region with Reynolds numbers in the range of 2500–5000. Some parameters including Reynolds number, axial distance, and mass concentration are also investigated. The preliminary results are firstly presented that the heat transfer coefficients of Fe3O4 nanofluids systematically decrease with increasing concentration of nanoparticles under transition region which contradicts the initial expectation.

scholarly journals Three-dimensional computational fluid dynamics modeling of TiO2/R134a nanorefrigerant

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 175-186 ◽  
Author(s):  
Kamil Arslan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Laminar Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Reynolds Numbers ◽  
Nanoparticle Volume Fraction ◽  
Steady State Condition ◽  
Volume Fractions

In this study, numerical investigations were carried out for R134a based TiO2 nanorefrigerants. Forced laminar flow and heat transfer of nanorefrigerants in a horizontal smooth circular cross-sectioned duct were investigated under steady-state condition. The nanorefrigerants consist of TiO2 nanoparticles suspended in R134a as a base fluid with four particle volume fractions of 0.8, 2.0 and 4.0%. Numerical studies were performed under laminar flow conditions where Reynolds numbers range from 8?102 to 2.2?103. Flow is flowing in the duct with hydrodynamically and thermally developing (simultaneously developing flow) condition. The uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition was applied on the duct wall. Commercial CFD software, Ansys Fluent 14.5, was used to carry out the numerical study. Effect of nanoparticle volume fraction on the average convective heat transfer coefficient and average Darcy friction factor were analyzed. It is obtained in this study that increasing nanoparticle volume fraction of nanorefrigerant increases the convective heat transfer in the duct; however, increasing nanoparticle volume fraction does not influence the pressure drop in the duct. The velocity and temperature distribution in the duct for different Reynolds numbers and nanoparticle volume fractions were presented.

Subcooled-Boiling and Convective Heat Transfer for Heptane Flowing Inside an Annulus and Past a Coiled Wire: Part II—Correlation of Data

1986 ◽  
Vol 108 (4) ◽  
pp. 928-933 ◽  
Author(s):  
H. Mu¨ller-Steinhagen ◽  
N. Epstein ◽  
A. P. Watkinson
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Subcooled Boiling ◽  
Transfer Data ◽  
Satisfactory Accuracy ◽  
Flow Past

In Part I of this paper, the authors reported an extensive series of heat transfer data for subcooled boiling of heptane in turbulent flow in an annulus, and in laminar flow past a coiled wire. These data plus some new measurements for laminar flow in the annulus were compared to the predictions of some 12 correlations from the literature. The applicability of these correlations to the present data is determined and a combination of correlations proposed to predict heat transfer with satisfactory accuracy.

Entrance effects on forced convective heat transfer in laminar flow through short hexagonal channels: Experimental and CFD study

2021 ◽  
Vol 405 ◽  
pp. 126635 ◽  
Author(s):  
Marzena Iwaniszyn ◽  
Przemysław J. Jodłowski ◽  
Katarzyna Sindera ◽  
Anna Gancarczyk ◽  
Mateusz Korpyś ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Forced Convective Heat Transfer ◽  
Flow Through
Sign in / Sign up

Export Citation Format

Share Document