Fin Temperature Research Articles

Effect of domain boundary set on natural convection heat transfer characteristics for vertical annular finned tube heat exchanger

The main purpose of this study is to use the three-dimensional commercial package along with experimental data and the inverse result of the heat transfer coefficient to investigate the effect of the computational domain boundary set on the natural convection heat transfer and fluid flow characteristics of single-tube vertical annular fin and tube heat exchanger in a box with an upward opening. Various flow models are introduced. The air temperature and velocity profiles, fin temperature and heat transfer coefficient on the fins are determined by the commercial package. More accurate numerical results and an appropriate flow model can be obtained if the resulting heat transfer coefficient and the fin temperature are close to the inverse result and experimental fin temperature data, respectively. However, differences in boundary condition set at the side walls of the box can affect air velocity and temperature profiles. The choice of the appropriate flow model can also be related to the boundary set of the computational domain. Thus, the suitability of the boundary condition set must be checked at the side walls of the box.

Numerical and experimental study of natural convection heat transfer characteristics for vertical annular finned tube heat exchanger

This study uses three-dimensional computational fluid dynamics (CFD) commercial package along with the inverse method and experimental data to investigate the natural convection heat transfer and fluid flow characteristics of the single-tube vertical annular finned tube heat exchanger for various values of fin spacing and tube diameter. The air temperature and velocity distributions, the fin surface temperature and the heat transfer coefficient on the fins are determined by the FLUENT along with various flow models in the box with the upward opening. The inverse method along with the finite difference method and the experimental temperature data is applied to determine the fin temperature and heat transfer coefficient for the smaller tube. More accurate results are obtained by the appropriate flow model, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. The fin temperature obtained at the selected measurement locations coincides with the experimental data. The results show that the zero-equation turbulence model is more suitable for this problem than laminar and RNG k-ε turbulence models. The grid independence assumption cannot be appropriate. The proposed correlations between the Nusselt number and the Rayleigh number are close to FLUENT and inverse results.

Machine-Thermal Coupling Stresses Analysis of the Fin-Type Structural Thermoelectric Generator

The design structure and heat-transfer mechanism of a thermoelectric generator (TEG) determine its body temperature state. Thermal stress and thermal deformation generated by the temperature variation directly affect the stress state of thermoelectric modules (TEMs). Therefore, the rated temperature and pressing force of TEMs are important parameters in TEG design. Here, the relationships between structural of a fin-type TEG (FTEG) and these parameters are studied by modeling and “machine-thermal” coupling simulation. An indirect calculation method is adopted in the coupling simulation. First, numerical heat transfer calculations of a three-dimensional FTEG model are conducted according to an orthogonal simulation table. The influences of structural parameters for heat transfer in the channel and outer fin temperature distribution are analyzed. The optimal structural parameters are obtained and used to simulate temperature field of the outer fins. Second, taking the thermal calculation results as the initial condition, the thermal-solid coupling calculation is adopted. The thermal stresses of outer fin, mechanical force of spring-angle pressing mechanism, and clamping force on a TEM are analyzed. The simulation results show that the heat transfer area of the inner fin and the physical parameters of the metal materials are the keys to determining the FTEG temperature field. The pressing mechanism’s mechanical force can be reduced by reducing the outer fin angle. In addition, a corrugated cooling water pipe, which has cooling and spring functionality, is conducive to establishing an adaptable clamping force to avoid the TEMs being crushed by the thermal stresses in the body.

Thermal performance of stratospheric airship with photovoltaic array

The increase of airship applications makes it necessary for a comprehensive understanding of the thermal performance of stratospheric airships. A numerical model was proposed to simulate the thermal performance of a stratospheric airship with photovoltaic array, an analysis code was developed based on the thermal model and was verified by experimental data. A further inspection into the temperature field and flow field distribution of the airship was analyzed in detail. The simulation results suggest that solar radiation can exert great influence on the thermal performance of the airship. The higher temperature Helium was gathered in the upper part inside of the airship, the flow of Helium was regular at nighttime but was chaotic in the middle and upper part of the airship at daytime. The temperature and velocity performance of fin was different from that of the hull and other fins due to the shadow of hull and other fins.

Numerical study of mixed convection heat transfer of various fin arrangements in a horizontal channel

The mixed convection of a three-dimensional square duct with various arrangements of fins in both laminar and turbulent flow is numerically characterized and studied. This study focuses on the ability of fin arrangements to enhance a heat transfer while flow is incompressible and the fluid is air. In our models, the lower duct wall is defined with a constant heat flux condition while the two side walls and upper wall are insulated. The finite volume method with the SIMPLE (Semi Implicit Method for Pressure Linked Equations) algorithm is used for handling the pressure–velocity coupling. The numerical results are validated with experimental data and show good agreement. The computations confirm that fin arrangement significantly changes the temperature distribution and cooling performance of the fins. This study focuses on the new arrangements of the fins that are not presented in previous studies. These arrangements have 3 Models with two angles (30 and 45°). According to the results, heat transfer highly improves (approximately 40–50% in the laminar flow stream and 15–20% in turbulent flow in comparison to base plate heat transfer) as the simple fin arrangement is replaced by inclined fins. Moreover, the influence of limited heat flux on temperature distribution is extensively investigated. It is notable that the temperature of fins significantly reduces as the best arrangement of the fins is presented in the air flow stream. Therefore, an enhanced cooling zone occurs when the fin arrangement is adjusted according to the location of the source of the heat flux on the base plate.

Investigation of Heat Transfer in Rectangular Porous Fins $$(\mathrm{Si}_3 \mathrm{N}_4 )$$ ( Si 3 N 4 ) with Temperature-Dependent Internal Heat Generation by Galerkin’s Method (GM) and Akbari-Ganji’s Method (AGM)

In this paper, heat transfer in rectangular porous fins with temperature-dependent internal heat generation, is investigated and Darcy’s model for passage velocity is applied. Heat transfer governing equation is solved by two simple and accurate methods, Galerkin’s Method (GM) and Akbari-Ganji’s Method (AGM). AGM is a simple and innovative approach can be applied for many linear and nonlinear problems and in this case by this method can reach solutions faster in comparison with other methods. Results indicate that GM and AGM are very accurate and effective in comparison with the numerical results. Porous fin is made from \(\mathrm{Si}_3 \mathrm{N}_4\). Effects of Darcy number and Rayleigh number on temperature distribution are investigated. As a main outcome, the heat generation rate is very effective in fin temperatures. When heat generation rate increases, fin temperatures increase since more amount of heat is dissipated to the surrounding.

Conjugated heat transfer from a uniformly heated plate and a plate fin with uniform base heat flux

The relationship between maximum temperature and heating rate is determined for an internally heated flat plate, which is cooled on both sides by either forced or natural convection. Convection heat transfer is calculated using the energy integral boundary layer equations instead of solving governing partial differential equations numerically. The results are presented in simple analytical correlations.Solutions to a heated plate were used in the study of a plate fin with a uniform heat flux at the base in cases of forced and natural convection. New simple analytical equations for the maximum fin temperature were derived using the result on the heated plate. Solutions to a fin with uniform base heat flux include also those to a uniform fin base temperature as limiting cases. The validity of the simple new solutions to an internally heated plate and a fin with a uniform heat flux at the base were verified by comparing results to numerically obtained conjugated heat transfer solutions, analytical solutions, and to some experimental data for a heated plate.

Insights from modeling dynamics of water sorption in spherical particles for adsorption heat pumps

The coupled heat and mass transport in porous adsorbents, shaped as spherical particles is simulated in the context of finned heat exchangers for thermally-driven heat pumps. Water vapor sorption behavior triggered by a step change in fin temperature, representative for the isobaric stages of a thermodynamic cooling cycle, is modeled for two different particle diameters, both in mono- and multi-layer configurations. Numerical results confirm the experimental observations for adsorption and desorption, with faster dynamics for smaller particles in monolayer configurations. Simulations show that contact between particles influences heat transfer in the particle ensemble to a different extent, dependent on particle diameter. The characteristic time required to reach 80% of the equilibrium amount of moisture uptake is only slightly affected by the particle packing configuration for the studied cases. Parametric evaluations of heat and mass transport properties of the adsorbent are carried out for an operational scenario typical for air-conditioning using low grade heat. The aim is to identify the critical factors for improving the specific cooling power of the adsorbent. Sorption dynamics and the corresponding specific cooling power are mostly affected by the heat transfer parameters of the adsorbent-heat exchanger system. Results indicate that further increasing the effective diffusivity within the material does not improve the specific cooling power, while a lower effective diffusivity dramatically decreases performance. This effect is more pronounced for larger particles in fewer layers.

Estimate of Mixed Convection Heat Transfer and Fluid Flow Characteristics of Plate-fin Heat Sinks in the Opening of the Enclosure

This study uses an inverse method and commercial package FLUENT along with the experimental data to obtain heat transfer and fluid flow characteristics of plate-fin heat sinks placed in a rectangular enclosure with two openings. A cooling fan placed on the top of the fins is blown downward. Another fan is placed on the outside of the opening in order to extract the air inside the enclosure. The inverse method along with the experimental temperature data is applied to estimate the heat transfer coefficient on the fins. Afterward, a commercial package FLUENT along with the zero-equation turbulence model, experimental temperature data and the resulting heat transfer coefficient is used to obtain heat transfer and fluid flow characteristics of plate-fin heat sinks within a rectangular enclosure with openings. The resulting heat transfer coefficient and fin temperature at the selected measurement locations are close to inverse results and the experimental temperature data, respectively. Thus, the zero-equation turbulence model is suitable for this problem.

Heat spreading and heat transfer coefficient with fin heat sink

Compact high powered semiconductor chips require greater heat dissipation and more effective thermal cooling systems have to be devised such as incorporating vapor chambers and thermoelectric. As a first step, the performance of two conventional fin heat sinks with flat metal base and an array of cooling fins on top are determined under force and natural convection air cooling and with various heating power input. Fin temperatures and heat transfer coefficients were determined for different size heating elements producing different area aspect ratios. This paper reports on the effect of thermal heat spreading effect and determination of the thermal heat spreading resistance. Heat spreading and contact resistances are small compared to the thermal resistance of the FHS itself.

Analysis of convective longitudinal fin with temperature-dependent thermal conductivity and internal heat generation

In this study, analysis of heat transfer in a longitudinal rectangular fin with temperature-dependent thermal conductivity and internal heat generation was carried out using finite difference method. The developed systems of non-linear equations that resulted from the discretization using finite difference scheme were solved with the aid of MATLAB using fsolve. The numerical solution was validated with the exact solution for the linear problem. The developed heat transfer models were used to investigate the effects of thermo-geometric parameters, coefficient of heat transfer and thermal conductivity (non-linear) parameters on the temperature distribution, heat transfer and thermal performance of the longitudinal rectangular fin. From the results, it shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric parameters of the fin. Also, for the solution to be thermally stable, the fin thermo-geometric parameter must not exceed a specific value. However, it was established that the increase in temperature-dependent properties and internal heat generation values increases the thermal stability range of the thermo-geometric parameter. The results obtained in this analysis serve as basis for comparison of any other method of analysis of the problem.

A Theoretical Study of Steady State and Transient Condensation on Axisymmetric Fins Under Combined Capillary and Gravitational Forces

The present work attempts to model the case of combined gravitational and capillary motion of condensate for an axisymmetric fin under steady and transient fin operation conditions. The focus here is to examine the structure of the mathematical problem and to develop suitable numerical techniques rather than yield information on the macroscopic condensate flow rate and fin efficiency. The problem is formulated starting from general conditions and is simplified step by step by introducing corresponding assumptions. The particular fin shape of a paraboloid from revolution is chosen and the equations are properly non-dimensionalized. A vast reduction of the number of problem parameters is achieved in this way. The cases of isothermal fin, steady state operation and dynamic operation are treated separately using specialized numerical solution techniques developed for each case in order to improve computational efficiency and accuracy. Typical results of fin temperature and condensate film thickness are presented and discussed.

Numerical and experimental study of natural convection heat transfer characteristics for vertical plate fin and tube heat exchangers with various tube diameters

This study uses three-dimensional computational fluid dynamics commercial package along with experimental data and various flow models to investigate the natural convection heat transfer and fluid flow characteristics of a single-tube vertical plate fin and tube heat exchangers for various values of fin spacing and tube diameter. Temperature and velocity distributions of air between the two fins, fin temperature and heat transfer coefficient on the fins are determined using FLUENT along with various flow models. The inverse method in conjunction with the finite difference method and the experimental temperature data is applied to determine the fin temperature and heat transfer coefficient for the smaller tube. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. The numerical results of the fin temperature at the selected measurement locations also coincide with the experimental temperature data. The results show that RNG k–ε turbulence model is more suitable for this problem than laminar flow model. Three proposed new correlations between the Nusselt number and the Rayleigh number are in good agreement with the inverse results and numerical results obtained.

Adomian decomposition sumudu transform method for solving a solid and porous fin with temperature dependent internal heat generation.

In this paper, Adomian decomposition sumudu transform method is introduced and used to solve the temperature distribution in a solid and porous fin with the temperature dependent internal heat generation for a fractional order energy balance equation. In this study, we assume heat generation as a variable of fin temperature for solid and porous fin and the heat transfer through porous media is simulated by using Darcy’s model. The results are presented for the temperature distribution for the range of values of parameters appeared in the mathematical formulation and also compared with numerical solutions in order to verify the accuracy of the proposed method. It is found that the proposed method is in good agreement with direct numerical solution.

Study of Heat Transfer and Fluid Flow in Heat Exchanger and Improve Their Energy Efficiency

In this study, two rows of fins from a fin-tube plate recuperator heat exchanger with two different materials, ceramic and steel, have been simulated by cfx software. First, by using experimental data that are in access, the independency from network and the confirmation of pattern authenticity have been checked. Equations from the equations of steady-state (SST) model k–ω have been used for applying turbulence terms in dominant. After network stabilization in greatest Reynolds number, the flow in the recuperator heat exchanger has been studied for two other Reynolds numbers. From the simulations, it is concluded that by increasing Reynolds number the temperature of fins' surfaces, outlet fluid temperature, and the temperature of tubes' surfaces will be increased, but totally the amount of overall heat transfer in time unit will be increased by the increase in Reynolds number. Also, it is observed that changing the material from steel to ceramic does not have that much difference for heat transfer in flow in low temperatures but the temperature of fins' surfaces for different materials and similar boundary status is different.

Spectral collocation method for radiative–conductive porous fin with temperature dependent properties

In this work, spectral collocation method is presented to predict the thermal performance of convective–radiative porous fin with temperature dependent convective heat transfer coefficient, fin surface emissivity and internal heat generation. In this approach, the dimensionless fin temperature distribution is approximated by Lagrange interpolation polynomials at spectral collocation points. The differential form of the governing equation is formulated by the Darcy model, and is transformed to a matrix form of algebraic equation. The accuracy of the SCM is verified by compared with numerical results by the homotopy perturbation method and the finite volume method. The node convergence rate of the SCM approximately follows an exponential law, and the computational time of the SCM do not significantly increase with the increasing of collocation points. The effects of various geometric and thermo-physical parameters on the dimensionless fin temperature, fin efficiency and heat transfer rate are comprehensively analyzed. In addition, optimum design analysis is also carried out.

Effects of psychrometric properties on fin performances of minimum envelope shape of wet fins

A method based on the variational principle is used to determine a minimum shape of wet fins for effective transfer of heat in fins. In many air-cooling applications, fin surface becomes wet as the surface is lower than the dewpoint temperature of the surrounding air. On the wet surface, both the sensible and latent heat transfer take place due to an existence of respective driving forces. The fin temperature is also dependent upon the latent heat released on its surface from the condensed moisture. The humidity ratio of air adjacent to the fin surface for the latent heat transfer is a psychrometric function with temperature. Due to this, the analysis of wet fins is always difficult as the governing fin equation is complex in nature. A simple model based on a linearity function between humidity ratio and temperature has been an alternative approximate model. The present analysis is attempted to estimate an envelope shape of wet fins by minimising fin volume for a constraint heat transfer rate for an actual variation of humidity ratio with temperature. The effect of psychrometric properties of air on the minimum shape of wet fins has been studied in the present work. The fin performance for the least envelope shape of wet fins is proposed with the variation of thermo-psychrometric parameters. A comparison of results for the variation of linear and nonlinear humidity ratio with temperature on the analysis of the minimum envelope shape has been systematically investigated. This study is also highlighted errors in connection with the linear model to determine the least fin shape for efficient heat transfer. This analysis may be extremely important in those augmentation heat transfer apparatuses where a gain in weight creates always an excessive overburden. Due to this, the selection of the function of humidity ratio as a fin surface temperature may be extremely important for calculating minimum weight of a fin for the same heat transfer duty.

Determination of Temperature Distributions of Fully Wet Rectangular, Triangular, and Parabolic Straight Fins

A numerical simulation is performed to determine the temperature distribution along fully wet fins of different geometric profiles under different relative humidity and surrounding temperature conditions. Four straight fin profiles are considered in this study: rectangular, triangular, concave parabolic, and convex parabolic. The same base thickness and length are used for consistency. The current work extends equations formulated in previous studies and applies them to the different fins to characterize their temperature distributions. The impact of the variation in the operating conditions on the fin tips and temperature distributions along the fin profiles is investigated. The simulation results confirm that increasing the surrounding temperature and relative humidity levels increases the temperature along the fins for all profiles. In addition, parametric studies indicate that the assumption of fully wet fins may be violated depending on the operating conditions. This is an important deviation from previous works that may have not considered the fully wet fin assumption.

Thermal analysis of longitudinal fin with temperature-dependent properties and internal heat generation using Galerkin's method of weighted residual

In this study, heat transfer in a longitudinal rectangular fin with temperature-dependent thermal properties and internal heat generation is analysed using Galerkin's method of weighted residual. The simple, but highly accurate solution was validated by the exact solution for the linear problem, and also by numerical method and differential transformation method in the case of the non-linear problem. The developed heat transfer models were used to investigate the effects of thermo-geometric parameters, coefficient of heat transfer and thermal conductivity (non-linear) parameters on the temperature distribution, heat transfer and thermal performance of the longitudinal rectangular fin. From the results, it shows that the fin temperature distribution, the total heat transfer, the fin effectiveness, and the fin efficiency are significantly affected by the thermo-geometric and thermal parameters of the fin. The analysis revealed that the operational parameters must be carefully chosen to ensure that the fin retains its primary purpose of removing heat from the primary surface. Therefore, the results obtained in this analysis serve as basis for comparison of any other method of analysis of the problem, and they also provide a platform for improvement in fin design of fin in heat transfer equipment.

Predication of nonlinear heat transfer in a convective-radiative fin with temperature-dependent properties by the collocation spectral method

ABSTRACTThe applicability of the collocation spectral method (CSM) for solving nonlinear heat transfer problems is demonstrated in a convective-radiative fin with temperature-dependent properties. In this method, the fin temperature distribution is approximated by Lagrange interpolation polynomials at spectral collocation points. The differential form of the energy equation is transformed to a matrix form of algebraic equations. The computational convergence of the CSM approximately follows an exponential decaying law; and thus, it is a very simple and effective approach for a rapid assessment of nonlinear physical problems. The effects of temperature-dependent properties such as thermal conductivity, surface emissivity, heat transfer coefficient, convection-conduction parameter, and radiation-conduction parameter on the fin temperature distribution and efficiency are discussed.