scholarly journals Transient Heat Transfer Through a Thin Circular Pipe Due to Unsteady Flow in the Pipe

1965 ◽  
Vol 87 (4) ◽  
pp. 513-520 ◽  
Author(s):  
N. Hayasi ◽  
K. Inouye
Keyword(s):  
Heat Transfer ◽  
Incompressible Fluid ◽  
Outer Surface ◽  
Circular Tube ◽  
Initial Period ◽  
Transient Heat Transfer ◽  
Insulating Material ◽  
Metallic Tube ◽  
Inner Surface ◽  
The Difference

An analysis of the transient heat transfer between a thin circular tube and the incompressible fluid moving through the tube is made for the case where the temperature of the inlet fluid is kept constant. Both radial conduction of heat in the wall and the heat loss at the outer surface of the cylinder are taken into consideration. It is shown to be especially easy to calculate temperature of both fluid and tube in the initial period by means of the figures. So far, it is common to use the temperature of the wall calculated by the assumption that it is constant radially. It is shown that for the insulated tube in the initial period such temperature is equal to the temperature of the outer surface of the tube. The temperature of the inner surface of the tube may be appreciably different from such temperature even for the metallic tube. The difference is extremely large for the tube made from insulating material.

Transient Heat Transfer of a Hollow Cylinder Subjected to Periodic Boundary Conditions

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Yujia Sun ◽  
Xiaobing Zhang
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Hollow Cylinder ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Transient Heat Transfer ◽  
Maximum Temperature ◽  
Water Cooling ◽  
Chromium Plating ◽  
Inner Surface

The purpose of this paper is to study the transient temperature responses of a hollow cylinder subjected to periodic boundary conditions, which comprises with a short heating period (a few milliseconds) and a relative long cooling period (a few seconds). During the heating process, the inner surface is under complex convection heat transfer condition, which is not so easy to approximate. This paper first calculated the gas temperature history and the convective heat transfer coefficient history between the gas flow and the inner surface and then they were applied to the inner surface as boundary conditions. Finite element analysis was used to solve the transient heat transfer equations of the hollow cylinder. Results show that the inner surface is under strong thermal impact and large temperature gradient occurs in the region adjacent to the inner surface. Sometimes chromium plating and water cooling are used to relief the thermal shock of a tube under such thermal conditions. The effects of these methods are analyzed, and it indicates that the chromium plating can reduce the maximum temperature of the inner surface for the first cycle during periodic heating and the water cooling method can reduce the growth trend of the maximum temperature for sustained conditions. We also investigate the effects of different parameters on the maximum temperature of the inner surface, like chromium thickness, water velocity, channel diameter, and number of cooling channels.

Investigation of Luminous/Nonluminous Radiation in a Vortex Engine

2007 ◽  
Author(s):  
M. H. Saidi ◽  
M. Kargar ◽  
A. Ghafourian
Keyword(s):  
Heat Transfer ◽  
Outer Surface ◽  
Direct Contact ◽  
Radiative Heat ◽  
Radiation Heat Transfer ◽  
Axial Flow ◽  
Chamber Wall ◽  
Radiation Heat ◽  
Insulating Material ◽  
Quartz Window

Investigation of radiation heat transfer In vortex engine is an important and new phenomenon in combustion for scientists and combustion researchers. In this research some parts of the combustion chamber wall are insulated using Blanket as a high insulating material. The rate of radiative heat transfer to the chamber wall is calculated using temperature difference between inner and outer surface of chamber. In the experiments this parts are protected from direct contact with hot combustion media using quartz window. The luminous radiative transfer per volume of chamber and also volume of flame in a vortex engine are compared with that in a similar axial flow type engine. A detector sensitive to emission from C2* excited radically is utilized for the measurement of chemiluminescence emission at the centerline of chamber along all axial positions. The filtered photographs of flame are used to compare total C2* emission from flame.

Increase in ovality of uranium tubes due to creep under external pressure

1968 ◽  
Vol 3 (3) ◽  
pp. 226-231
Author(s):  
W S Blackburn ◽  
J Percy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Creep Rate ◽  
Temperature Gradient ◽  
Outer Surface ◽  
External Pressure ◽  
Radial Temperature Gradient ◽  
Radial Temperature ◽  
Principal Axes ◽  
Inner Surface

The increase in ellipticity of a concentric slightly elliptical tube is theoretically investigated for the case of external pressure and radial temperature gradient when the creep rate is proportional to the stress and the constant of proportionality varies slightly between the principal axes. The presence of a radial temperature gradient accelerates the increase in ovality due to initial ovality on the outer surface and that due to circumferential variation of strength (except after very small collapses) and decreases that due to initial inner ovality. Further allowance for circumferential variation in temperature, due to an insulated inner surface and to a uniform heat-transfer coefficient to a gas at constant temperature around the outer surface, reduces the increase in all cases.

An Experimental Study on Flow Boiling Heat Transfer Outside Horizontal Enhanced Tubes

2020 ◽  
Author(s):  
Liangxiang Ma ◽  
Jianghui Zhang ◽  
Xiang Ma ◽  
Zongbao Gu ◽  
Yan He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Outer Surface ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Smooth Tube ◽  
Flow Boiling Heat Transfer ◽  
Enhanced Tubes ◽  
Inner Surface

Abstract A flow boiling heat transfer experimental investigation on the shell-side of a smooth tube and two enhanced tubes (C-EHT, P-EHT) was performed using R410A as working fluid. The outer surface of the C-EHT tube is covered with special fins having a salient height, and the inner surface has a thread structure with the same distribution density. The outer surface of the P-EHT tube has lots of tiny pits formed by high-strength sandblasting and smooth inner surface. The inlet and outlet vapor quality is 0.2 and 0.8 at a saturation temperature of 279K. The flow boiling experimental results show that the evaporation heat transfer coefficient of C-EHT tube is the largest among the tested tubes. However, for the P-EHT tube, its heat transfer coefficient is lower than that of smooth tube. C-EHT tube with special fins has higher heat transfer area, which can also intensify the interfacial turbulence with increasing fins. The reason why the flow boiling heat transfer coefficient of the P-EHT tube is lower than that of the smooth tube is that the diameter of the pit on P-EHT tube is too small to form the nucleation cites, which results in bubble retention under the condition of low mass flux and deteriorates the flow boiling heat transfer performance.

The Solution of a Heat Transfer Problem With Change of State Inside a Spherical Shell

2012 ◽  
Author(s):  
Danillo Silva de Oliveira ◽  
Fernando Brenha Ribeiro
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Spherical Shell ◽  
Outer Surface ◽  
Transfer Problem ◽  
Freezing Temperature ◽  
Liquid Interface ◽  
Inner Surface ◽  
Solid Liquid Interface ◽  
Solid Liquid

The heat transfer problem is solved for the case of cooling, below the freezing temperature, an initially liquid material inside a spherical shell. The shell is limited by a fixed inner surface and by an outer surface, free to radially expand or contract. As boundary conditions it is imposed that the inner surface is kept constant below the freezing temperature of the liquid and the outer surface is maintained constant above it. The solution represents the formation of a solidified layer that expands outward, separated from the liquid by a spherical surface kept constant at the freezing temperature. The problem is solved in the form of two closed form solutions, written in non-dimensional variables: one for the heat conduction equation in the solid layer and the second for the heat conduction – advection equation in the liquid layer. The solutions formally depend of and are linked by the time dependent radius of the spherical solid–liquid interface and its time derivate, which are, at first, unknown. A differential equation describing the solid–liquid interface radius as function of time is obtained imposing the conservation of energy through the interface during the heat exchange process. This equation is non-linear and has to be numerically solved. Substitution of the interface radius and its time derivate for a particular instant in the heat transfer equations solutions furnishes the temperature distribution inside the spherical shell at that moment. The solution is illustrated with numerical examples.

scholarly journals Temperature Difference Effect between Two Samples Ends on the Inception of Thermal Sensitivity

2019 ◽  
Vol 27 (2) ◽  
pp. 183-193
Author(s):  
Ridha Hameed Majeed
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Temperature Difference ◽  
Thermal Sensitivity ◽  
Convection Heat Transfer ◽  
The Body ◽  
The Other ◽  
Transient Heat Transfer ◽  
Two Samples ◽  
The Difference

This paper examined the effect of the difference between the temperature of the two end of the body exposed to transient conduction heat transfer on the inception of thermal sensitivity and at different distances from the hot end of the sample. The study was based on the selection of a sample with a length of 15 cm and a fixed height of 1 cm. Four materials with different thermal properties were selected. One end of the model was exposed to three different temperatures (75, 125, and 175) oC. The other end of the sample was placed under a convection heat transfer at 25 oC. To adopt an inception indicator of thermal sensitivity of the sample when exposed to transient heat transfer, (26) oC was used because it is the nearest temperature to the initial condition of the sample. Four points were selected on different distance from hot end along the sample. The hot end temperature was also adopted as an indicator to measure the effect of the temperature difference for two body ends as the other end is subject to constant transient heat transfer.   Determine the effect of the temperature difference   between two body ends exposed to transient heat transfer on the inception of thermal sensitivity is study target. The  results of this study showed  the reverse effect of the temperature difference   between two body ends  exposed to transient heat transfer on the inception of thermal sensitivity, this effect increases by increasing the distance from  hot sample end   and depressing of thermal diffusivity. The results also showed that the values of the Thermal sensitivity inception ranged between (0.43-17845) seconds according to the    distance from the hot end, its temperature, and the thermal diffusivity of sample materials for each case.

Sign in / Sign up

Export Citation Format

Share Document