Heat Transfer in Pipe Flow

2008 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Temperature Distribution ◽  
Laminar Flow ◽  
Pipe Flow ◽  
Simple Procedure ◽  
Internal Flow ◽  
Uniform Heat Flux ◽  
Flux Boundary Conditions

A simple procedure using spreadsheets is presented where the temperature distribution for laminar flow in a circular pipe is determined from the entrance of the pipe up to the fully developed region is calculated numerically. The results are then used to show the different features of internal flow like constancy of Nusselt number. The solution is presented for both isothermal and uniform heat flux boundary conditions and are then compared with available correlations.

Oscillatory Heat Transfer in a Pipe Subjected to a Laminar Reciprocating Flow

1996 ◽  
Vol 118 (3) ◽  
pp. 592-597 ◽  
Author(s):  
T. S. Zhao ◽  
P. Cheng
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Nusselt Number ◽  
Numerical Study ◽  
Temperature Cycle ◽  
Uniform Heat Flux ◽  
Fluid Temperature ◽  
Cycle Space ◽  
Reciprocating Flow

An experimental and numerical study has been carried out for laminar forced convection in a long pipe heated by uniform heat flux and subjected to a reciprocating flow of air. Transient fluid temperature variations in the two mixing chambers connected to both ends of the heated section were measured. These measurements were used as the thermal boundary conditions for the numerical simulation of the hydrodynamically and thermally developing reciprocating flow in the heated pipe. The coupled governing equations for time-dependent convective heat transfer in the fluid flow and conduction in the wall of the heated tube were solved numerically. The numerical results for time-resolved centerline fuid temperature, cycle-averaged wall temperature, and the space-cycle averaged Nusselt number are shown to be in good agreement with the experimental data. Based on the experimental data, a correlation equation is obtained for the cycle-space averaged Nusselt number in terms of appropriate dimensionless parameters for a laminar reciprocating flow of air in a long pipe with constant heat flux.

Theoretical Analysis of High Prandtl Number Heat Transfer in Non-Isothermal Pipe Flow

2005 ◽  
Author(s):  
Huajun Chen ◽  
Yitung Chen ◽  
Hsuan-Tsung Hsieh ◽  
Taide Tan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Distribution ◽  
Analytical Solution ◽  
Prandtl Number ◽  
Pipe Flow ◽  
Fourier Expansion ◽  
Mathematical Expressions ◽  
High Prandtl Number ◽  
Turbulent Wall

Based on Fourier expansion, an analytical solution is developed for the high Prandtl number heat transfer in both fully developed laminar and turbulent non-isothermal pipe flow. Both of the mathematical expressions of the temperature distribution and the local Nusselt number have been obtained. A parametric study illustrates the characteristics of high Prandtl number heat transfer in non-isothermal pipe flow in detailed. The solutions obtained can be used for the numerical construction of the solution to the more general problems of heat transfer in the developed turbulent wall-bounded shear flows.

Heat Transfer and Pressure Drop Characteristics of Laminar Flow Through a Circular Tube With Longitudinal Strip Inserts Under Uniform Wall Heat Flux

2002 ◽  
Vol 124 (3) ◽  
pp. 421-432 ◽  
Author(s):  
S. K. Saha ◽  
P. Langille
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Friction Factor ◽  
Test Section ◽  
Circular Tube ◽  
Short Length ◽  
Full Length

Heat transfer and pressure drop characteristics in a circular tube fitted with full-length strip, short-length strip, and regularly spaced strip elements connected by thin circular rods have been investigated experimentally. The strips have been rectangular, square and crossed in cross-section with different aspect ratio. Laminar flow of water and other viscous liquids was considered. The rod diameter and length of the strip-rod assembly and the length of the strips were varied. Isothermal friction factor data has been generated. The heat transfer test section was heated electrically imposing axially and circumferentially constant wall heat flux (UWHF) boundary condition. Reynolds number, Prandtl number, strip length, strip ratio, space ratio, and rod-diameter govern the characteristics. Smaller rod-diameter in the strip-rod assembly or “pinching” of the strips in place rather than connecting the strip elements by rods performs better thermohydraulically. Short-length strips (upto a limited fraction of the test section tube length) perform better than the full-length strip. The friction factor correlation and the correlation for Nusselt number under UWHF condition for full-length strip have been modified to make them suitable for short-length strip as well as regularly-spaced strip elements. Thermal entrance length in the correlations is represented by Graetz number. Friction factor and Nusselt number correlations for short-length strips as well as regularly-spaced strip elements, in the limit, reduce to their full-length counterparts.

Experimental Study of Fully Developed Convection in a Copper Horizontal Tube With Uniform Heat Flux Using Nanofluids

2009 ◽  
Author(s):  
Naser Zarezadeh ◽  
Majid Saffar-Avval
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Horizontal Tube ◽  
Continuous Phase ◽  
Constant Heat Flux ◽  
Uniform Heat Flux

The term of nanofluid refers to a solid-liquid mixture with a continuous phase which is a nanometer sized nanoparticle dispersed in conventional base fluids. Recent investigations on nanofluids indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension. There are less published articles on deriving the forced convective heat transfer of nanofluids than articles on the effective thermal conductivity of nanofluids. Fully developed turbulent flow and heat transfer of two different nanofluids (Al2O3 and TiO2) in water flowing through a circular tube under constant heat flux condition have been experimentally studied. The results showed enhancement of convective heat transfer using the nanofluids. The Nusselt numbers of nanofluids were obtained for different nanoparticle concentrations as well as various Reynolds numbers. Experimental results emphasize the enhancement of heat transfer due to the nanoparticles presence in the fluid. Nusselt number increases by increasing the concentration of nanoparticles in nanofluid. And values of Nusselt number were calculated and these results have been introduced by experimental correlations for turbulent flow.

Nonuniform Temperature Distribution in Electronic Devices Cooled by Flow in Parallel Microchannels

2000 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Distribution ◽  
High Speed ◽  
Flow Boiling ◽  
Convection Heat Transfer ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Two Phase ◽  
Parallel Microchannels

Abstract We fabricated a novel thermal microsystems (simulating a computer chip) consisting of a heater, microchannels, inlet and outlet plena and we studied the effect of the geometry on the flow and heat transfer. The vapor - water two-phase flow patterns were observed in the parallel microchannels through a microscope and high-speed video camera. It was observed that hydraulic instabilities occur. Existence of a periodic annular flow was also observed, which consist of a symmetrically distributed liquid ring surrounding the vapor core. Along the microchannel axis, the periodic dry zone appears and develops. The thermal visualization and temperature measurements of the heated device were carried out using infrared thermography. As long as the flow was single phase liquid, the forced convection heat transfer resulted in a moderate irregularity on the heated chip. These temperature differences do not cause damage to the device. The steady-state heat transfer for different types of microchannels has been studied also at the range of heat flux where phase change of the working fluid from liquid to vapor took place. Under conditions of flow boiling in microchannels, a significant enhancement of heat transfer was established. In the case of uniform heat flux the hydraulic instabilities lead to irregularity of temperature distribution on the heated chip. In the case of nonuniform heat flux the irregularity increased drastically.

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