Closure to “Discussion of ‘Two-Dimensional Transient Solutions for Crossflow Heat Exchangers With Neither Gas Mixed’ and ‘Transient Temperature Fields in Crossflow Heat Exchangers With Finite Wall Capacitance’” (1993, ASME J. Heat Transfer, 115, p. 1082)

1993 ◽  
Vol 115 (4) ◽  
pp. 1082-1082
Author(s):  
G. Spiga ◽  
M. Spiga
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Two Dimensional ◽  
Transient Solutions

Transient Temperature Response of Variable Flow Heat Exchangers in a Marnoch Heat Engine

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
P. Saneipoor ◽  
G. F. Naterer ◽  
I. Dincer
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Heat Engine ◽  
Heat Transfer Model ◽  
Transient Temperature ◽  
Transfer Model ◽  
Gas Temperature ◽  
Variable Flow ◽  
Flow Heat ◽  
Shell And Tube

Within a Marnoch heat engine (MHE), a water/glycol mixture transfers heat from the heat source into a set of variable flow heat exchangers and removes heat from adjoining cold heat exchangers. The compressed dry air is used as the working medium in this heat engine. The MHE has four shell and tube heat exchangers, which operate transient and variable flow conditions. A new transient heat transfer model is developed to predict this transient behavior of the heat exchangers for different flow regimes and temperatures. The results from the model are validated against experimental results from an MHE prototype. The heat transfer model shows 85% agreement with measured data from the MHE prototype for the individual heat exchangers. This model can be used for similar shell and tube heat exchangers with straight or U-shaped tubes. The heat transfer model predicts the gas temperature on the shell side, when a step change is imposed on the liquid entering the tubes.

scholarly journals SOLVING TRANSIENT INVERSE HEAT TRANSFER PROBLEMS IN COMPLEX GEOMETRIES USING PHYSICS-GUIDED NEURAL NETWORKS (PGNN)

2021 ◽  
Vol 2021 (3) ◽  
pp. 4540-4547
Author(s):  
D. Emonts ◽  
◽  
J. Yang ◽  
R. H. Schmitt ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Input Parameter ◽  
Temperature Fields ◽  
Elastic Behavior ◽  
Transient Temperature ◽  
Complex Geometries ◽  
Inverse Heat Transfer ◽  
Geometric Inspection ◽  
Transfer Problems

Temporally and spatially unstable thermal conditions lead to transient or inhomogeneous thermo-elastic behavior of workpieces during manufacturing or geometric inspection. Temperature monitoring by means of sensors consign transient temperature fields, but do not yield information about the heat flow acting as thermal boundary condition, which is a relevant input parameter for nearly any thermal simulation. Addressing the need for efficient methods, the authors propose an approach to solve inverse heat transfer problems in complex geometries. In the presented study, locally acting heat loads are experimentally investigated based on virtual demonstrators running in FEM. The conducted method shows high potential for transient heat flow modelling in terms of accuracy and computational efficiency.

scholarly journals Analytic transient solutions of a cylindrical heat equation

Filomat ◽  
2021 ◽  
Vol 35 (8) ◽  
pp. 2617-2628
Author(s):  
K.Y. Kung ◽  
Man-Feng Gong ◽  
H.M. Srivastava ◽  
Shy-Der Lin
Keyword(s):  
Heat Transfer ◽  
Differential Equation ◽  
Partial Differential Equation ◽  
Heat Conduction ◽  
Heat Equation ◽  
Heat Conduction Equation ◽  
Separation Of Variables ◽  
Transient Heat Conduction ◽  
Transient Temperature ◽  
Transient Solutions

The principles of superposition and separation of variables are used here in order to investigate the analytical solutions of a certain transient heat conduction equation. The structure of the transient temperature appropriations and the heat-transfer distributions are summed up for a straight mix of the results by means of the Fourier-Bessel arrangement of the exponential type for the investigated partial differential equation.

scholarly journals Laser interferometry - Report #HT-01-2017

2021 ◽  
Author(s):  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Light Beam ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Laser Interferometry ◽  
Local Heat ◽  
Temperature Fields ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Transfer Rates

An introduction is given to the optical setup and principle of operation of classical and holographic interferometers that are used for convective he at transfer measurements. The equations for the evaluation of the temperature field are derived and methods of analysis are discussed for both two-dimensional and three-dimensional temperature fields. Emphasis is given to techniques for measuring local heat transfer rates. For two-dimensional fields, a method is presented for measuring the surface temperature gradient directly from a finite (wedge) fringe interferogram. This “direct gradient method” is shown to be most useful for the measurement of low convective heat transfer rates. For three-dimensional fields, the equations for calculating the beam-averaged local heat flux are presented. The measurement of the fluid temperature averaged along the light beam is shown to be approximate. However, an analysis is presented showing that for most cases the error associated with temperature variations in the light beam direction is small. Digital image analysis of interferograms to obtain fringe spacings is also discussed briefly.

Bifurcations of Numerically Simulated Marangoni Flows in Floating Zones

1997 ◽  
Vol 07 (06) ◽  
pp. 1295-1305
Author(s):  
C. Menke
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Marangoni Number ◽  
Control Parameter ◽  
Thermocapillary Convection ◽  
Period Doubling ◽  
Time Dependent ◽  
Temperature Fields ◽  
Two Dimensional ◽  
Period Doubling Bifurcations

Marangoni or thermocapillary convection in a two-dimensional cylindrical half zone configuration under microgravity is studied numerically. The time-dependent simulations take into account convection and conduction in the melt, heat transfer between the melt and the ambient, and deformations of the free melt/gas surface of the half zone. A modified Marker and Cell (MAC) method is used to compute the flow and the temperature fields. The algorithm is applied especially to silicon melts. Above a critical temperature difference in the melt, the steady state becomes unstable and oscillatory thermocapillary convection occurs. The relevant control parameter for the onset of oscillations is the Marangoni number. As the Marangoni number increases, the phenomenon of period doubling is observed in the simulations. After a sequence of period doubling bifurcations, the flow becomes turbulent.

Transient Behavior of Crossflow Heat Exchangers With Longitudinal Conduction and Axial Dispersion

2004 ◽  
Vol 126 (3) ◽  
pp. 425-433 ◽  
Author(s):  
Manish Mishra ◽  
P. K. Das ◽  
Sunil Sarangi
Keyword(s):  
Heat Transport ◽  
Heat Exchangers ◽  
Temperature Response ◽  
Transient Behavior ◽  
Axial Dispersion ◽  
Transient Temperature ◽  
Inlet Temperature ◽  
Conductive Heat ◽  
Two Dimensional ◽  
Transient Temperature Response

Transient temperature response of the crossflow heat exchangers with finite wall capacitance and both fluids unmixed is investigated numerically for step, ramp and exponential perturbations provided in hot fluid inlet temperature. Effect of two-dimensional longitudinal conduction in separating sheet and axial dispersion in fluids on the transient response has been investigated. Conductive heat transport due to presence of axial dispersion in fluids have been analyzed in detail and shown that presence of axial dispersion in both of the fluid streams neutralizes the total conductive heat transport during the energy balance. It has also been shown that the presence of axial dispersion of high order reduces the effect of longitudinal conduction.

Heat Transfer in Friction Stir Welding—Experimental and Numerical Studies

2003 ◽  
Vol 125 (1) ◽  
pp. 138-145 ◽  
Author(s):  
Yuh J. Chao ◽  
X. Qi ◽  
W. Tang
Keyword(s):  
Heat Transfer ◽  
Friction Stir Welding ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Friction Stir ◽  
Heat Flows ◽  
Numerical Studies ◽  
Weld Residual Stress ◽  
Joining Process

In the friction stir welding (FSW) process, heat is generated by friction between the tool and the workpiece. This heat flows into the workpiece as well as the tool. The amount of heat conducted into the workpiece determines the quality of the weld, residual stress and distortion of the workpiece. The amount of the heat that flows to the tool dictates the life of the tool and the capability of the tool for the joining process. In this paper, we formulate the heat transfer of the FSW process into two boundary value problems (BVP)—a steady state BVP for the tool and a transient BVP for the workpiece. To quantify the physical values of the process the temperatures in the workpiece and the tool are measured during FSW. Using the measured transient temperature fields finite element numerical analyses were performed to determine the heat flux generated from the friction to the workpiece and the tool. Detailed temperature distributions in the workpiece and the tool are presented. Discussions relative to the FSW process are then given. In particular, the results show that (1) the majority of the heat generated from the friction, i.e., about 95%, is transferred into the workpiece and only 5% flows into the tool and (2) the fraction of the rate of plastic work dissipated as heat is about 80%.

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