Fin Temperature Research Articles

Optimal profile of heat transfer pin fins under technological constraints

Direct optimal control methods are used. The pin fin's volume is minimized for given heat flux value. Schmidt's criterion is not adopted. The optimal pin fin profile is neither parabolic nor circular. It consists of two regions. In the first region, close to the basis, the pin thickness decreases linearly. In the second region the pin thickness is constant or may decrease, depending on thermal loads and operation. The optimal control solution is usually singular but may be approximated by a bang–bang solution. The Schmidt criterion works better at larger heat flux values. Results obtained for specific assumptions adopted in the paper (fluid temperature 300 K, transverse Biot number ranging between 0.00041 and 0.041) are summarized next. For very small values of the heat flux (=0.1 W) the reduced minimum pin fin volume (i.e. the ratio between pin fin volume and the volume of a cylinder of similar length) is about one tenth. The technology and design constraints have important effects on the optimal pin fin's profile. The reduced minimum pin fin volume decreases from 0.30 to 0.20 when the maximum slope of the pin fin profile increases from 1 to 100. The reduced pin fin volume is a minimum minimorum for a maximum allowable pin fin temperature ranging between two and three times the fluid temperature.

Determination of relative positions and phase angle of dual piezoelectric fans for maximum heat dissipation of fin surface

A three-dimensional computational model for dual piezoelectric fans on the bounded plane has been built using the commercial code CFD-ACE+, and the Levenberg–Marquardt Method (LMM) was used to estimate the optimal relative positions and phase angle of fans for minimizing the average temperature of the fin surface. The dual piezoelectric fans are originally placed in seven different positions (cases 1–7), and the LMM is then utilized to estimate the optimal relative positions and phase angle for increasing the thermal performance of dual piezoelectric fans. The simulations of numerical computations show that for each of the seven original fan arrangements, the optimal relative positions and phase angle of the dual fan are achieved using a singular arrangement in which both fans are located 0.95mm below the center line of the fin and the in-phase operational condition is used. Finally, the temperature distributions of the fin for the original designs of cases 1 and 2 and for the optimal design of case 1 are measured using a thermal camera and are compared with the numerical solutions. The results indicate that the relative errors between numerical and experimental average fin temperatures at 600s for original case 1, original case 2 and optimal case 1 are 0.68%, 0.52% and 0.68%, respectively, thereby validating the estimation method used herein to determine the optimal relative positions and phase angle of dual piezoelectric fans.

Analysis of laminar film condensation over vertical permeable hollow short fins

Laminar falling film condensation over vertical short fin is analyzed. The fin is considered to be hollow and permeable in order to account for condensate suction towards its inner core. The present work accounts for the shear stress at the interface caused by the large velocity of the saturated vapor. The continuity, momentum, and energy equations for the film condensate are solved using an iterative and implicit finite-difference method. The condensate flow rate inside the fin is obtained using the conservation of mass principle and the Poiseuille flow equations. The one-dimensional fin equation model is used to relate the fin temperature to the condensate flow convection heat transfer coefficient. Various computational and numerical methods techniques such as advanced linearization and generations of best-fit correlations are implemented. This is to reduce significantly the number of iterations required for solution convergence as all of the aforementioned equations are coupled. It is found that the dimensionless total mass transfer rate increases slightly as vapor Reynolds number increases. It increases apparently as both suction Reynolds number and dimensionless suction length increase. For both large suction Reynolds number and large dimensionless suction length, the flow rate of the condensate in the falling film can be neglected compared to the total suction condensate flow rate. The fin thermal length increases as Reynolds number, dimensionless suction length, and Grashof number increase. This study shows that significant condensation mass flow rate enhancement ratios are obtainable (can be 18 folds) due to suction through a hollow super conductive fin.

A computational study of mixed convective heat and mass transfer from a shrouded vertical non-isothermal fin array during dehumidification process

A computational study is made on simultaneous heat and mass transfer from a shrouded vertical non-isothermal finite thickness fin array representing dehumidification process undergoing mixed convection. Governing equations involve number of parameters, namely, dimensionless fin spacing (0.1⩽S∗⩽0.5), dimensionless clearance (0⩽tc∗⩽0.2), non-dimensional fin conductance parameter (2830.18⩽Ω⩽5660.37), thermal Grashof number (1.04×105⩽Grt⩽4.82×105), mass Grashof number (2.9×104⩽Grm⩽1.36×105), and dimensionless inlet mixed convection velocities (1123⩽Win,mix⩽2879). Induced velocity is decoupled from the mixed convection velocity and correlated with the governing parameters. Fin temperature distribution shows significant variation along the fin height as well as along the axial direction, especially near the entrance. Local thermal Nusselt number and local condensing Nusselt number show monotonic decreasing trend along the axial direction. Finally induced velocity, pressure drop, overall thermal Nusselt number, and overall condensing Nusselt number is correlated with the governing parameters.

Effects of Geometrical Parameters to the Performance of Louvered Fin Heat Exchangers

Numerical study using ANSYS Fluent is conducted to investigate the effects of louver angle on pressure drop and heat transfer of a heat exchanger. Flow simulations are conducted on 3D modeling of multi stacks louvered fins at three different parameters of louver angles which are 22.0o, 25.5o and 29.0o with Reynolds number ranging from 200 to 1000. These Reynolds numbers are based on louver pitch and fin pitch. The flow temperature is set at 300K which is the room temperature, while temperature of louver fin is set at 400K. The results show that Reynolds number based on fin pitch 2.02 mm and louver angle of 22.0o generate higher performance of heat exchanger compared to louver pitch of 1.40 mm and the other louver angles. Therefore, configuration of Reynolds number based on fin pitch 2.02 mm and louver angle 22.0o is preferred to be adopted in the design process of heat exchanger.

Numerical estimation of heat transfer characteristics for two-row plate-finned tube heat exchangers with experimental data

This study applies a three-dimensional computational fluid dynamics commercial software in conjunction with various flow models to estimate the heat transfer and fluid flow characteristics of the two-row plate-finned tube heat exchanger in staggered arrangement. The effect of air speed and fin spacing on the results obtained is investigated. Temperature and velocity distributions of air between the two fins and heat transfer coefficient on the fins are determined using the laminar flow and RNG k-e turbulence models. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. Furthermore, the fin temperature measured at the selected locations also coincides with the experimental temperature data. The results obtained using the RNG k-e turbulence model are more accurate than those using the laminar flow model. An interesting finding is the number of grid points may also need to change with fin spacing and air speed.

Heat transfer study on convective–radiative semi-spherical fins with temperature-dependent properties and heat generation using efficient computational methods

In this study, heat transfer and temperature distribution equations for semi-spherical convective–radiative porous fins are presented. Temperature-dependent heat generation, convection and radiation effects are considered and after deriving the governing equation, Least Square Method (LSM), Collocation Method (CM) and fourth order Runge-Kutta method (NUM) are applied for predicting the temperature distribution in the described fins. Results reveal that LSM has excellent agreement with numerical method, so can be suitable analytical method for solving the problem. Also, the effect of some physical parameters which are appeared in the mathematical formulation on fin surface temperature is investigated to show the effect of radiation and heat generation in a solid fin temperature.

Periodic Heat Transfer in Convective Fins Based on Dual-Phase-Lag Theory

Heat transfer enhancement through extended surfaces is crucial in modern engineering applications such as microelectromechanical systems and electronic components. Conduction heat transfer is the only way to achieve this objective when the mixing augmentation is not possible. This paper investigates the effects of non-Fourier thermal conduction in convective straight fins with arbitrary constant cross section under periodic boundary conditions by introducing the exact analytical solution for the dual-phase-lag heat conduction. The corresponding analytical approach is developed through the Laplace transform method and inversion theorem. To help advance the understanding of fin thermophysical behavior, a generalized model of conduction heat transfer equation is used for studying all of the interpretations to Fourier-based model, namely, parabolic thermal diffusion, hyperbolic thermal wave, and dual-phase-lag models. Heat flux and temperature gradient relaxation times are the characteristics of the dual-phase-lag model, and the simulation results are strictly a function of these two parameters. Therefore, fin temperature distributions are presented for flux precedence and gradient precedence heat flow regimes. Calculations are performed to investigate the influence of temperature gradient relaxation time on the hyperbolic heat conduction characteristics of non-Fourier fins.

A New Forward Model Approach for a Mild Steel Fin under Natural Convection Heat Transfer

This paper reports the correlation for temperature of the mild steel fin which is subjected to heat flux at its base. The study is performed on a two dimensional, steady state and laminar flow model. The numerical model is restricted to natural convection and the fluid under consideration is air. A rectangular mild steel fin (250mm x 150mm x 6mm), aluminium base plate (250mm x 150mm x 8mm) and an extended geometry representing the ambient air condition is modelled and simulated using ANSYS 14.5. Grid independence study is carried out to fix the number of grids in order to find the optimum number of nodes for carrying out simulations. The heat flux (q) at the bottom of the base plate is varied to study temperature distribution, surface heat transfer coefficient (h) and velocity profile of the flow in the boundary layer around the fin. All these parameters are studied by inclining the model at various angles. A multiple regression analysis is carried out to obtain correlation for the temperature in terms of angle of inclination and the heat flux. The main objective of the work is, proposing a model for the estimation of heat flux or heat transfer coefficient from the fin thereby reducing the computational cost of the forward model in the field of inverse heat transfer.

Artificial neural network-based temperature prediction in heat sinks with cross cuts fins

Soft computing techniques are predominantly used in varied sectors of research for accurate prediction and optimisation. Recent advancements in artificial neural network ANN and its capability to predict the data have increased its range of applications including heat transfer problems. The present paper aims to predict base plate temperature of cross cut fins of variable height 5-15 mm, fin spacing 5.85-32 mm, number of crosscuts 0-5, heat duty 20-100 W for constant fin thickness 3 mm and base plate dimensions 180 × 250 mm. A neural network model is designed for a rectangular heat sink with cross cut fins. The model is developed using the data from numerical heat transfer calculation carried out in ANSYS FLUENT©. The numerical model is validated with similar experimental results available in literature. The simulated data are used to train several neural-network configurations and the best neural-network model is used for prediction. The ANN model is used to predict the base plate temperatures of cross cut fins. The results reveal the ability of using ANN for accurate prediction of base plate temperature.

단일진공관 태양열집열기의 형상변화 및 접촉저항에 따른 집열효율 연구

The use of solar energy among renewable energy tends to increase because of its infinity and cleanness of resources. Even though the consumption rate of solar energy in our country is still low, however, in recent years, the research for solar energy have been widely conducted due to policy support of government. This study was performed to investigate the efficiency of heat collection using solar collector with single evacuated tube-type. As the results, the temperature of radiation fin for solar collector with single evacuated tube-type was lower in spite of high temperature of heat pipe compared that of double evacuated tube-type. In order to increase the efficiency of heat collection, it was confirmed that the loss of heat collection due to contact resistance as well as performance improvement for solar collector should be decreased.

Heat transfer study on solid and porous convective fins with temperature-dependent heat generation using efficient analytical method

A simple and highly accurate semi-analytical method, called the differential transformation method (DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with temperature dependent internal heat generation. The problem was solved for two main cases. In the first case, heat generation was assumed variable by fin temperature for a solid fin and in second heat generation varied with temperature for a porous fin. Results are presented for the temperature distribution for a range of values of parameters appearing in the mathematical formulation (e.g. N, ɛ G , and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results in comparison to numerical methods.

A decomposition method for convective–radiative fin with heat generation

Abstract This work is aimed at studying the effect of environmental temperature such as radiation sink temperature, convection sink temperature and heat generation number on the temperature distribution and efficiency of a convective–radiative stationary fin. The Adomian Decomposition Method (ADM) being one of the efficient numerical methods for highly non linear equations, the local temperature field and efficiencies are obtained using ADM in which Newton–Rapson method is used to estimate the fin temperature for insulated boundary conditions. It is found that the present ADM results are good agreement with the results available in literature using Galerkin Method (GM) and Boundary Value problem Method (BVP).

An improved approximate method for determining the temperature and efficiency of the nonlinear convective-radiative-generating fin: effect of environmental temperatures

Efficiency and temperature distributions of rectangular convective-radiative-generating fin are evaluated when thermal conductivity and internal heat generation are temperature dependent. It demonstrates that the proposed method can be treated sequentially the nonlinear fin problem with three nonlinearities. Predicted results are found accurate within 4 % of the tip fin temperature and 5 % for the efficiencies. For practical used fins, the fin efficiency is strongly sensitive to convective and radiation environmental temperatures.

Thermal analysis of convective fin with temperature-dependent thermal conductivity and heat generation

In this study, a simple and highly accurate semi-analytical method called the Differential Transformation Method (DTM) is used for solving the nonlinear temperature distribution equation in a longitudinal fin with temperature dependent internal heat generation and thermal conductivity. The problem is solved for two main cases. In the first case, heat generation is assumed variable by fin temperature and in the second case, both thermal conductivity and heat generation vary with temperature. Results are presented for the temperature distribution for a range of values of parameters appeared in the mathematical formulation (e.g. N, εG, and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results compared to numerical methods.

Efficiency of heat and mass transfer in fully wet porous fins: Exponential fins versus straight fins

The combined heat and mass transfer mechanisms owing to the temperature and humidity ratio differences and their influence on the efficiency of different exponential type porous fin configurations are analyzed in this paper. The closed-form temperature solutions for an exponential impermeable dry fin as obtained in an earlier publication (Turkyilmazoglu, 2012) are extended here to the case where the surface of the fin is fully wet and porous. A comparison with the traditional straight porous fins proves that the fin tip temperature and efficiency of the exponential porous wet fins are much better than those of corresponding to the straight porous wet fins.

Experimental investigation of dredging thermal protection system of hypersonic vehicle leading edge

According to the characteristics of dredging thermal protection system (DTPS) of hypersonic vehicle leading edge, both the structure of embedded high conductivity materials and that of integrative plate of heat pipe are designed to complete the two kinds of comparative experiments so as to prove the feasibility of the DTPS. As a source of radiation heating, the spherical short arc xenon lamp is simulated for aerodynamic heating. The pure steel leading edge, the embedded copper leading edge, the plate pure steel leading edge, and the integrative plate for heat pipe leading edge are heated respectively. Temperature variations of stagnation point region and tail fins are measured. Experimental results show that DTPS of the embedded high conductivity materials can reduce the temperature of stagnation point region and increase the temperature of the tail fins. It also can achieve the aim of thermal protection of leading edge. The DTPS of integrative plate heat pipe whose working fluid is pure water also can protect the leading edge under the condition of low heat flux. At the huge pressure of vapor, DTPS of the integrative plate of heat pipe may be broken at high heat flux. It is shown that the working fluid of heat pipe can play a key role in the application range for the thermal protection effect.

Investigation of refrigeration efficiency for fully wet circular porous fins with variable sections by combined heat and mass transfer analysis

Temperature distribution equation and refrigeration efficiency for fully wet circular porous fins with variable sections are introduced in this study by a new modified wet fin parameter presented by Sharqawy and Zubair. This parameter can be calculated without knowing the fin tip condition by considering the temperature and humidity ratio differences for the driving forces of heat and mass transfer, respectively. It's assumed that heat and mass convective coefficients vary with fin temperature and heat transfer through porous media is simulated using passage velocity from the Darcy's model. After presenting the governing equation, Least Square Method (LSM) and fourth order Runge-Kutta method (NUM) are applied for predicting the temperature distribution in the sample aluminum porous fins. After that, effects of porosity, Darcy number, Rayleigh number, Lewis number and etc. on fin efficiency are examined. As a main outcome, for reaching to high values of fin efficiency, rectangular fin should be used instead of convex and triangular sections.

On Solution of Natural Convection and Radiation Heat Transfer Problem in a Moving Porous Fin

Thermal analysis of simultaneous natural convection and radiation in moving porous fin is conducted. Homotopy analysis method (HAM) is applied to solve energy equation considering two types of boundary conditions. The accuracy of HAM is validated through comparison with the numerical results. The effects of embedding parameters on the dimensionless temperature and heat transfer rate are studied. The results show that the fin temperature reaches quickly to the surrounding temperature for two types of fins when the value of porous parameter increases. It is observed that the temperature along the length of fin decreases for both infinite and finite fins when the values of C T and Rd increase. Further, a slowdown in the heat transfer rate at the fin tip is found with the increased value of Peclet number.

A numerical study of the deposition characteristics of sulfuric acid vapor on heat exchanger surfaces

Accurate predictions of the sulfuric acid condensation behavior on the surfaces of heat exchangers are crucial for understanding the local low-temperature corrosion characteristics of heat exchangers and designing them. In this paper, a new numerical model has been developed to predict the condensation rate of sulfuric acid and condensate acidic solution concentration on heat exchanger surfaces. By correlating the vapor–liquid equilibrium (VLE) data of H2SO4–H2O solutions from experiments and in conjunction with multi-component diffusion theory, the proposed model obtains numerical solutions of condensation heat transfer under the conditions of a coupled wall and fluid boundary condition and a multi-component mixture of flue gas and the sulfuric acid solution (saturated partial pressure of sulfuric acid and water vapor). The numerical model has been validated by a comparison of the simulation results with available experimental data, and applied to an analysis of the H-type finned tube heat exchanger, which has been widely used in the field of waste heat recovery. The distributions of the condensation rate and condensate concentration on the fin surface are also calculated. The results show that the three dimensional distribution of acid solution concentration is consistent with the fin temperature. An increase in water vapor could result in a sharp reduction of the acid solution concentration and an increase in deposition, which may indicate a serious risk for low-temperature corrosion. In contrast, increasing the flue gas temperature will reduce the corrosion risk by reducing the condensation rate and increasing the acid concentration.