scholarly journals Performance analysis and optimization of rectangular fin arrays used in plate-fin heat exchangers

2020 ◽  
pp. 213-213
Author(s):  
Weicheng Wu ◽  
Hassan Soliman
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Performance Analysis ◽  
Aspect Ratio ◽  
Analytical Solutions ◽  
Heat Exchangers ◽  
Two Dimensional ◽  
One Dimensional ◽  
Independent Parameters

This paper deals with longitudinal rectangular fin arrays used in plate-fin heat exchangers. The temperature distribution and rate of heat transfer were obtained using one dimensional (1-D) and two-dimensional (2-D) solutions. The ranges of independent parameters within which the 1-D solution was within 1% from the 2-D solution were determined. Simple analytical solutions were determined for the rate of heat transfer, fin effectiveness, and augmentation factor. The aspect ratio at which the rate of heat transfer reached a maximum was determined, as well as the corresponding effectiveness and augmentation factor.

Numerical Analysis for Heat and Mass Transfer of Granular Flow in a Duct by the Discrete Particle Simulation

2009 ◽  
Author(s):  
Tomohiko Yamaguchi ◽  
Kuniyasu Kanemaru ◽  
Satoru Momoki ◽  
Toru Shigechi ◽  
Ryo Fujiwara
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Energy Equation ◽  
Continuous Phase ◽  
Particle Simulation ◽  
Two Dimensional ◽  
Discrete Particle ◽  
One Dimensional ◽  
Discrete Particle Simulation ◽  
Dimensional Simulation

The solid-gas or liquid-gas two phase flow has many industrial applications such as spray drying, pollution control, transport systems, fluidized beds, energy conversion and propulsion, material processing, and so on. Though the solid-gas multiphase flow has been studied experimentally and numerically, the transport phenomena have not been cleared due to its complexity, computational time and economical costs for the hardware. In this study the heat and mass transfer of solid-gas collision dominated flow is analyzed by the Discrete Particle Simulation (DPS), a kind of the Dispersed Element Method (DEM)[1]. This method describes the discrete phase and the continuous phase by Lagrange and Euler methods respectively, and has been used to simulate the multiphase flow of various geometrical systems. In order to analyze the thermal field we took account of the energy equation and heat conduction between colliding particles. The heat transfer rate is summation of conductive heat transfer and convective heat transfer. Furthermore, the fluid flow has a two dimensional velocity profile, because the void fractions are analyzed as two dimensions. But momentum space has not been resolved by the two dimensional simulation. We call this method, the quasi two-dimensional simulation in this paper. To obtain the temperature distribution of the continuous phase the energy equation is solved in addition to the momentum equations. We treated the interaction between continuous and discrete phases as one and two way couplings. The positions, the momentum and the temperature information of particles and the velocity and the temperature distribution of the fluid were obtained as functions of time from results of these numerical simulations. When the hot air that is suspending small glass particles flows in a duct from bottom up, we traced the particles and got the temperature distribution of fluid and compared with the former results of one-dimensional flow. At the beginning, the cooler particles decrease the fluid temperature near the bottom of the vessel. The temperature profile of the particles obtained by the one-dimensional simulation is as same as quasi two-dimensional simulation. After 0.5 second the particles cool the downstream air. At 1.2 second, particles do not decrease the air temperature because the temperatures of particles are close to the inlet temperature of the air.

Numerical Analysis of Heat Exchangers Used in a Liquid Piston Compressor Using a One-Dimensional Model With an Embedded Two-Dimensional Submodel

2014 ◽  
Author(s):  
Chao Zhang ◽  
Jacob Wieberdink ◽  
Terrence W. Simon ◽  
Perry Y. Li ◽  
James Van de Ven ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Conduction ◽  
Heat Exchangers ◽  
Piston Compressor ◽  
Two Dimensional ◽  
Dimensional Model ◽  
One Dimensional ◽  
Temperature Distributions ◽  
Liquid Piston

The present study presents a one-dimensional liquid-piston compressor model with an embedded two-dimensional submodel. The submodel is for calculating heat conduction across a representative internal plate of a porous heat exchanger matrix within the compression space. The liquid-piston compressor is used for Compressed Air Energy Storage (CAES). Porous-media-type heat exchangers are inserted in the compressor to absorb heat from air as it is compressed. Compression without heat transfer typically results in a temperature rise of a gas and a drop in efficiency, for the elevated temperature leads to wasted thermal energy, due to cooling during subsequent cooling back to ambient temperature. The use of heat exchangers can reduce the air temperature rise during the compression period. A typical numerical model of a heat exchanger is a one-dimensional simplification of the two-energy-equation porous media model. The present authors proposed a one-dimensional model that incorporates the Volume of Fluid (VOF) method for application to the two-phase flow, liquid piston compressor with exchanger inserts. Important to calculating temperature distributions in both the solid and fluid components of the mixture is heat transfer between the two, which depends on the local temperature values, geometry, and the velocity of fluid through the matrix. In the one-dimensional model, although the axial temperatures vary, the solid is treated as having a uniform temperature distribution across the plate at any axial location. This may be in line with the physics of flow in most heat exchangers, especially when the exchangers are made of metal with high thermal conductivity. However, it must be noted that for application to CAES, the gas temperature in the compression chamber rises rapidly during compression and the core of the solid wall may heat up to a different temperature than that of the surface, depending on the geometry, solid material of the exchanger and fluid flow situation. Therefore, a new, one-dimensional model with embedded two-dimensional submodel is developed to consider two-dimensional heat conduction in a representative solid plate. The VOF concept is used in the model to handle the moving liquid-gas interface (liquid piston). The model gives accurate solutions of temperature distributions in the liquid piston compression chamber. Six different heat exchangers with different length scales and different materials are simulated and compared.

scholarly journals Some numerical experiments on firn ventilation with heat transfer

1993 ◽  
Vol 18 ◽  
pp. 161-165 ◽  
Author(s):  
M.R. Albert
Keyword(s):  
Heat Transfer ◽  
Surface Pressure ◽  
Thermal Effects ◽  
Numerical Experiments ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Two Dimensional ◽  
One Dimensional ◽  
Thermal Signature ◽  
Spatially Varying

Preliminary estimates of the thermal signature of ventilation in polar firn are obtained from two-dimensional numerical calculations. The simulations show that spatially varying surface pressure can induce airflow velocities of 10−5m s−1at 1.5 m depth in uniform firn, and higher velocities closer to the surface. The two-dimensional heat-transfer results generally agree with our earlier one-dimensional conclusions that the thermal effects of ventilation tend to decrease the temperature gradient in the top portions of the pack. Field observations of ventilation through temperature measurements are most likely to be observed when the firn temperature at depths on the order of 10 m is close to the air temperature, since steep temperature gradients can mask the thermal effects of ventilation. Preliminary indications are that, as long as surface-pressure amplitude is sufficient to move the air about in the top tens of centimeters in the snow, the resulting temperature profile during ventilation is fairly insensitive to the frequency of the surface-pressure forcing for pressure frequencies in the range 0.1–10.0 Hz.

Effect of Wall Conduction on Combined Free and Forced Laminar Convection in Horizontal Rectangular Channels

1987 ◽  
Vol 109 (4) ◽  
pp. 936-942 ◽  
Author(s):  
G. J. Hwang ◽  
F. C. Chou
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Distribution ◽  
Finite Difference ◽  
Aspect Ratio ◽  
Finite Difference Method ◽  
Numerical Study ◽  
Fully Developed Flow ◽  
Rectangular Channels ◽  
Laminar Convection

This paper presents a numerical study of the effect of peripheral wall conduction on combined free and forced laminar convection in hydrodynamically and thermally fully developed flow in horizontal rectangular channels with uniform heat input axially, In addition to the Prandtl number, the Grashof number Gr+, and the aspect ratio γ, a parameter Kp indicating the significance of wall conduction plays an important role in heat transfer. A finite-difference method utilizing a power-law scheme is employed to solve the system of governing partial differential equations coupled with the equation for wall conduction. The numerical solution covers the parameters: Pr = 7.2 and 0.73, γ = 0.5, 1, and 2, Kp = 10−4–104, and Gr+ = 0–1.37×105. The flow patterns and isotherms, the wall temperature distribution, the friction factor, and the Nusselt number are presented. The results show a significant effect of the conduction parameter Kp.

Quasi-Steady-State Temperature Distribution in Periodically Contacting Finite Regions

1981 ◽  
Vol 103 (4) ◽  
pp. 739-744 ◽  
Author(s):  
B. Vick ◽  
M. N. O¨zis¸ik
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Distribution ◽  
Interface Temperature ◽  
Quasi Steady State ◽  
Exact Analytical Solutions ◽  
One Dimensional ◽  
Steady State Temperature ◽  
Regular Cycle

Heat transfer across two surfaces which make and break contact periodically according to a continuous regular cycle is investigated theoretically and exact analytical solutions are developed for the quasi-steady-state temperature distribution for a two-region, one-dimensional, periodically contacting model. The effects of the Biot number, the thermal conductivity and thermal diffusivity of the materials and the duration of contact and break periods on the interface temperature and the temperature distribution within the solids are illustrated with representative temperature charts.

scholarly journals MATHEMATICAL MODELS OF HEAT TRANSFER IN ELEMENTS OF TURBO GENERATORS (CONTINUED)

2020 ◽  
Vol 2 (1) ◽  
pp. 21-28
Author(s):  
V. I. Havrysh ◽  
◽  
B. O. Bilinskyi ◽  
O. S. Korol ◽  
R. R. Shkrab ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Mathematical Models ◽  
Half Space ◽  
Analytical Solutions ◽  
Internal Heat ◽  
Normal Operation ◽  
Cylindrical Shape ◽  
Temperature Regimes

Previously developed [8] and presented new mathematical models for the analysis of temperature regimes in individual elements of turbo generators, which are geometrically described by isotropic half-space and space with an internal heat source of cylindrical shape. Cases are also considered for half-space, when the fuel-releasing cylinder is thin, and for space, when it is heat-sensitive. For this purpose, using the theory of generalized functions, the initial differential equations of thermal conductivity with boundary conditions are written in a convenient form. To solve the obtained boundary value problems of thermal conductivity, the integral Hankel transformation was used, and as a result, analytical solutions in the images were obtained. The inverse Hankel integral transformation was applied to these solutions, which made it possible to obtain the final analytical solutions of the initial problems. The obtained analytical solutions are presented in the form of improper convergent integrals. Computational programs have been developed to determine the numerical values ​​of temperature in the above structures, as well as to analyze the heat transfer in the elements of turbo generators due to different temperature regimes due to heating by internal heat sources concentrated in the cylinder volume. Using these programs, graphs are presented that show the behavior of curves constructed using numerical values ​​of the temperature distribution depending on the spatial radial and axial coordinates. The obtained numerical values ​​of temperature indicate the correspondence of the given mathematical models for determining the temperature distribution to the real physical process. The software also allows you to analyze media with internal heating, concentrated in the spatial figures of the correct geometric shape, in terms of their heat resistance. As a result, it becomes possible to increase it, to determine the allowable temperatures of normal operation of turbo generators, to protect them from overheating, which can cause the destruction of not only individual elements but also the entire structure.

scholarly journals Screw thermal characteristics analysis and error prediction considering the two-dimensional heat transfer structure

2021 ◽  
Author(s):  
Yu Chen ◽  
Jihong Chen ◽  
guangda xu
Keyword(s):  
Heat Transfer ◽  
Optimal Parameter ◽  
Thermal Characteristic ◽  
Thermal Characteristics ◽  
Thermal Error ◽  
Local Optimum ◽  
Two Dimensional ◽  
Feed System ◽  
One Dimensional ◽  
Transfer Structure

Abstract Thermal error is a common problem in machine tool processing. It is usually proposed to take the screw as one-dimensional rod heat transfer system to solve the thermal error of screw by establishing thermal characteristic equation. This method regards the temperature on the nut as the temperature of the screw contact surface without considering the heat transfer distance between screw and the mounting point on the nut. To solve this problem, this paper takes the screw-nut feed system as a two-dimensional heat transfer structure considering both screw and nut. In addition, to solve the low convergence speed and easy fall into local optimum problem in optimal parameter identification. The improved particle swarm optimization algorithm (IPSOA) is proposed to identify the boundary parameters of thermal characteristics equations. Finally, the temperature and thermal error of the screw-nut feed system is calculated by the identified results. Experiments under different working condition show that the maximum prediction residual error of the two-dimensional method (TDM) is less than 7.2 um and the simulating prediction accuracy can reach 86.2%. Besides, compared with one-dimensional model (ODM), TDM has a higher predict accuracy which verifies the effectiveness of the proposed method.

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