On the Conjugate Problem of Laminar Combined Free and Forced Convection through Vertical Non-Circular Ducts

1972 ◽  
Vol 94 (1) ◽  
pp. 52-56 ◽  
Author(s):  
M. Iqbal ◽  
B. D. Aggarwala ◽  
A. K. Khatry
Keyword(s):  
Heat Conduction ◽  
Laminar Flow ◽  
Forced Convection ◽  
Small Variation ◽  
Conjugate Problem ◽  
Momentum Equation ◽  
Variational Technique ◽  
Fluid Properties ◽  
Free And Forced Convection ◽  
Axial Heat

The present analysis deals with the conjugate problem of combined free and forced convection through vertical non-circular ducts. The equations coupling heat conduction in the walls with the convection inside the fluid are solved to establish the influence of peripheral wall conduction, using variational technique. Fully developed laminar flow with uniform axial heat input and constant fluid properties, except for the small variation of density in the buoyancy term of the momentum equation, is assumed. The problem has been solved in a generalized way and the results have been presented for rectangular ducts. It is found that large values of the free convection effects and/or of the conduction parameter tend to minimize the asymmetries in circumferential wall temperature.

Axial Heat Conduction Effects in Unsteady Forced Convection Along a Cylinder

1987 ◽  
Vol 109 (3) ◽  
pp. 787-791
Author(s):  
C. D. Surma Devi ◽  
M. Nagaraj ◽  
G. Nath
Keyword(s):  
Heat Conduction ◽  
Forced Convection ◽  
Axial Heat ◽  
Axial Heat Conduction

Combined Free and Forced Convection Heat Transfer for Laminar Flow in Horizontal Tubes

1965 ◽  
Vol 7 (4) ◽  
pp. 440-448 ◽  
Author(s):  
A. R. Brown ◽  
M. A. Thomas
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Laminar Flow ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Horizontal Tubes ◽  
New Correlation ◽  
Free And Forced Convection

This paper describes an investigation into combined free and forced convection heat transfer for laminar water flow in horizontal tubes. The experimental data obtained do not agree with existing correlations, which relate mainly to oils. A new correlation has been derived which fits the water data to within ±8 per cent.

Transient, Laminar, Combined Free and Forced Convection in a Duct

1962 ◽  
Vol 84 (2) ◽  
pp. 141-148 ◽  
Author(s):  
S. L. Zeiberg ◽  
W. K. Mueller
Keyword(s):  
Steady State ◽  
Forced Convection ◽  
Wall Temperature ◽  
Axial Direction ◽  
Transient Heating ◽  
Fully Developed Flow ◽  
Fluid Properties ◽  
Free And Forced Convection ◽  
Approach To Steady State ◽  
Rayleigh Numbers

Transient, laminar, combined free and forced convection in a duct is analyzed under the assumptions of constant fluid properties, and fully developed flow. The transient heating is taken to be a result of wall temperature variations; the wall temperatures vary linearly with the axial co-ordinate of the duct (this is shown to be the only permissible axial dependence, other than no wall temperature variation in the axial direction). Numerical results show that for certain combinations of the Prandtl and Rayleigh numbers, an oscillatory approach to steady state exists. This phenomenon can induce a large reduction of the Nusselt number (compared to steady state) during the transient period.

Viscous Dissipation Effects on Combined Free and Forced Convection Through Vertical Circular Tubes

1970 ◽  
Vol 37 (4) ◽  
pp. 931-935 ◽  
Author(s):  
M. Iqbal ◽  
B. D. Aggarwala ◽  
M. S. Rokerya
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Viscous Dissipation ◽  
Transfer Rate ◽  
Circular Duct ◽  
Circular Tubes ◽  
Nusselt Numbers ◽  
Fluid Properties ◽  
Flow Phenomena ◽  
Free And Forced Convection

The effect of viscous dissipation on the flow phenomena and heat transfer rate in a vertical circular duct is analyzed for combined free and forced convection. All fluid properties are considered constant, except variation of density in the buoyancy term. It is noted that effect of viscous dissipation is to reduce the temperature differences in the system which in turn counteract the buoyancy effects. Therefore the viscous dissipation reduces the flow velocity near the wall and increases it near the tube center. Viscous dissipation effects reduce the Nusselt numbers. The reduction in Nusselt numbers is about six percent at the high values of the buoyancy rate (Rayleigh number = 1000) and the dissipation effect Eckert number/Reynolds number = 0.0005 was used in the present study.

Study of the Heat Transfer in the Wellbore During Acid/Hydraulic Fracturing Using a Semianalytical Transient Model

SPE Journal ◽  
2019 ◽  
Vol 24 (02) ◽  
pp. 877-890 ◽  
Author(s):  
Yu Peng ◽  
Jinzhou Zhao ◽  
Kamy Sepehrnoori ◽  
Yibo Li ◽  
Wei Yu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Low Temperature ◽  
Laminar Flow ◽  
Hydraulic Fracturing ◽  
Forced Convection ◽  
Rock Type ◽  
Transient Heat Conduction ◽  
Fracturing Fluid ◽  
Cement Sheath

Summary Bottomhole-temperature variations have a significant influence on the rheological properties of fracturing fluid and the reaction rates of rock and acid in the operations of acid/hydraulic fracturing. In this work, a semianalytical model is developed for calculating the heat transfer in a wellbore under transient state. In the model, transient heat conduction in the cement sheath and forced convection in the tubing under different flow regimes are considered. Also in this model, calculation methods of heat-transfer coefficients of forced convection in the tubing and natural convection in the annulus are improved in relation to the existing methods. The semianalytical model is verified by monitoring the data of acid and hydraulic fracturing; it is accurate enough to estimate the physical properties of the fracturing fluid and perform simulations in the reservoirs. We studied transient heat conduction in a cement sheath, the influence of flow regimes on tubing, the variation of thermal properties in the wellbore, and the influence of vertical variations of rock type. Simulation results show that the influence of different heat-transfer states of the cement sheath on bottomhole temperature is much more significant under the injection rate of fracturing. Laminar flow is activated by extremely low injection velocity or low temperature in shallow layers. However, such low velocity can never be attained in the fracturing operation. Also, the high heat resistance caused by laminar flow in shallow layers cannot affect the bottomhole temperature significantly because of the low temperature difference between fracturing fluid and formation rock. We also found that the complex vertical variation of rock type and shale and sandstone interbedding could be approximated by the average temperature of simple models that are computationally faster and have an acceptable range of errors.

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