Fin Temperature Research Articles

Exact solution of the nonlinear fin problem with exponentially temperature-dependent thermal conductivity and heat transfer coefficient

This article studies a class of fin problems with two nonlinear terms arising from thermal conductivity and convection heat transfer coefficient. A one-dimensional convective straight fin is analysed for exponentially temperature-dependent thermal conductivity and exponentially temperature-dependent heat transfer coefficient. The exact fin temperature excess, heat transfer rate and fin efficiency are obtained and presented graphically. The obtained results show the strong influences of exponent indexes of thermal conductivity and convection transfer coefficient as well as thermogeometric fin parameter on the fin efficiency and heat flow.

Augmentation of natural convection heat sink via using displacement design

Miniaturization of electronic devices demands an effective thermal management system for efficient cooling. Still, many electronic industries use natural convection cooling techniques like plate-fin heat sinks as far as no moving part (noise) and reliability is concerned. In this study, the widely-used plate fin heat sink is augmented by a novel fin displacement amid fin array. Yet the effect of fin displacement between alternate fins is experimentally and numerically investigated under natural convection condition. In the meantime, the effects of fin spacing, length, height, and heat flux on the heat sink performance subject to fin displacement is also studied. For the smaller fin pacing, introducing the fin displacement will delay the merging of boundary layers, and reduce the length of fully developed region accordingly. Smaller fin spacing can also entrain the outside air into the fin array at the upper portion of heat sink for offering additional enhancement. The fin displacement is especially effective for a smaller fin spacing. This is because fully developed flow prevails at a smaller fin spacing. On the other hand, the fin displacement may impair the performance when a very wide fin spacing is used. Similarly, the increase in the fin length also enhances the heat transfer performance under the fin displacement conditions. It is also found that the effect of fin height on the thermal performance is small and the effect of heat flux is negligible. The maximum reduction in the thermal resistance is 56% by adopting the displacement design. A drop in fin temperature at the upper portion with the displacement design may lead to a reduction in heat transfer coefficient. For the comparison containing the fixed volume, the heat sink with fin displacement offers a 30% heat transfer enhancement ratio, 28.7% reduction in total mass, and 27.4 % reduction in surface area when compared to the conventional heat sinks.

Hava Soğutmalı PVT Panellerde Panel Yüzey Sıcaklığını Etkileyen Kontrol Parametrelerinin Optimizasyonu

Panel yüzey sıcaklığı PV panelin performans parametreleri üzerinde çok önemli etkiye sahiptir. Özellikle yaz aylarında görülen panel yüzey sıcaklığındaki aşırı yükselme panel veriminde ciddi düşüşlere neden olur. Bu olumsuz durum panel yüzeyi soğutularak minimize edilebilir. Bu çalışmada, hava soğutmalı PVT sistemine kanatçıklar eklendi. Kontrol parametrelerinin (panelin arka yüzey sıcaklığı, fan hızı, kanal derinliği, kanatçık konfigürasyonu, kanatçık malzemesi) panel yüzey sıcaklığına, kanatçık sıcaklığına ve çıkış sıcaklığına etkisi Taguchi Yöntemi kullanılarak incelendi ve en uygun tasarım kombinasyonu belirlendi. Ayrıca ANSYS FLUENT analizi ile elde edilen görüntüler analiz edildi. Çalışmamızda monokristal panel kullanıldı. Bakır, alüminyum ve pirinç malzemelerden yapılmış kanatçıkların sık ve seyrek konfigürasyonları için deneyler yapıldı. Panel yüzey sıcaklığı, kanatçık sıcaklığı ve çıkış sıcaklığı için en etkili parametrelerin kanatçık konfigürasyonu, fan hızı ve kanal derinliği olduğu görüldü. Optimal tasarım kombinasyonu, panel yüzey sıcaklığı için A2-B3-C2-D3-E2 olduğu, kanatçık sıcaklığı için A1-B1-C3-D2-E2 olduğu, çıkış sıcaklığı için A1-B1-C3-D2-E3 olduğu bulundu.

Numerical simulation research of influencing factors of fin temperature in finned tube heat exchanger

In the using process of the finned tube, the temperature on the top of the windward face of the fin in the first and second row of finned tube is the highest temperature of finned tube. It restricts and determines the high temperature conditions and application fields of finned tube heat exchanger. This paper establishes the research model of the first row and second row finned tube, to carry out the numerical simulation calculation of the fluid flow and heat transfer of high temperature air flowing through the finned tube and exchanging heat with cooled liquid water, and to research the influence of different tube transverse spacing, fin spacing and other factors on the fluid flow and heat transfer characteristics of finned tube and the highest fin temperature. The air outlet temperature, heat exchange capacity, Nu number, pressure drop and maximum fin temperature are obtained in the conditions of different tube transverse spacing and fin spacing, and the variation characteristic, mechanism and law of temperature field and velocity vector for the finned tube are also gained.

Structural parameters study on stainless-steel flat-tube heat exchangers with corrugated fins

A stainless steel corrugated fins and flat-tube heat exchanger is designed, which has a plate-fin structure. To optimize the structural parameters of this exchanger, including corrugation angle, corrugation pitch and fin length, 3-D simulation model and test were proposed. The numerical results indicated that the corrugation angle significantly affects both on heat transfer performance and pressure drop. The fin with angle, A = 0~20?, have demonstrated the higher heat transfer efficiency, lesser gas condensation, lower pressure drop, higher outlet flue gas temperature in low T region, and no exceeding the distortion temperature in high T region. Corrugation pitch and fin length influence thermal and hydraulic characteristics, outlet flue gas temperature, and fin temperature. To improve heat transfer performance, and reduce the fin temperature in high T region and ease gas condensation in low T region, smaller corrugation pitch and shorter fin length were recommended in the low T region, whereas higher values were more reasonable in high T region. Noticeably, the heat transfer and flow characteristics were better in the high T region than the low T region. Therefore, higher priority should be given to the structural optimization in the high T region in order to in-crease the heat transfer enhancement

The impact of square shape perforations on the enhanced heat transfer from fins: Experimental and numerical study

Heat sinks are widely adopted as heat transfer boosters for their role in promoting heat transfer surface area. To enhance the thermal behaviour of heat sinks under forced convection heat transfer, perforated fins are utilized. In the present investigation, the effect of utilizing the square perforation technique has been experimentally and numerically investigated. The study was conducted for different numbers of perforations, i.e. 4, 6, 9, 12, and 15; heat supplied rates of 1730, 2200, 2680, and 3150 W; and airflow velocities of 0.4, 0.7, 1.1, 1.4, and 1.8 m/s. The present numerical results were validated against the present experimental results and available data in the literature, and excellent agreements were found. Our results indicated that the perforated fin with square perforations has shown a reduction in the fin temperature up to 16 °C compared to the non–perforated one. Moreover, by increasing the number of perforations, higher heat rates were dissipated because of the rise in the flow turbulence level and the reduction in the thermal resistance between the fin surface and its surroundings. In addition, the existence of perforations reduced the friction factor around the fin and sequentially reducing the required flow pumping power, which adds another merit to the aforementioned perforation technique. Using square perforations showed a 5.9% reduction in average friction factor compared to circular perforations.

Numerical Simulation of Dual-Phase-Lag Model and Inverse Fractional Single-Phase-Lag Problem for the Non-Fourier Heat Conduction in a Straight Fin

In recent years, many studies have been done on heat transfer in the fin under unsteady boundary conditions using Fourier and non-Fourier models. In this paper, unsteady non-Fourier heat transfer in a straight fin having an internal heat source under periodic temperature at the base was investigated by solving numerically Dual-Phase-Lag and Fractional Single-Phase-Lag models. In this way, the governing equations of these models were presented for heat conduction analysis in the fin, and their results of the temperature distribution were validated using the theoretical results of Single and Dual-Phase-Lag models. After that, for the first time the order of fractional derivation and heat flux relaxation time of the fractional model were obtained for the straight fin problem under periodic temperature at the base using Levenberg-Marquardt parameter estimation method. To solve the inverse fractional heat conduction problem, the numerical results of Dual-Phase-Lag model were used as the inputs. The results obtained from Fractional Single-Phase-Lag model could predict the fin temperature distribution at unsteady boundary condition at the base as well as the Dual-Phase-Lag model could.

Geometric optimization of a highly conductive insert intruding an annular fin

Annular fins are abundantly applied in industry, especially for cooling curved surfaces such as the tube wall. However, it is well-known that the fin conductive resistance reduces the total cooling performance. Therefore, in this paper, geometric optimization is carried out to reach the maximum cooling performance of an annular fin intruded by a pathway of highly conductive materials (‘insert’). The optimization objective is to reach the minimum peak temperature of the annular fin that extracts heat with constant heat flux at the fin base. The fixed total volume of the fin, as well as the fixed total volume of insert, are considered as a constraint. The optimization process is in conjunction with a numerical solution to obtain the temperature field in the fin. The results show that the optimized insert results in considerable elevation of the fin performance by reducing the peak temperature (thermal resistance) of the fin. Finally, the effects of several parameters such as the conductance ratio and the Biot number on the optimal results are reported. It has been proved that increasing the conductance ratio and Biot number reduces the peak temperature.

Exact solution of a nonlinear fin problem of temperature-dependent thermal conductivity and heat transfer coefficient

This paper studies a class of nonlinear problems of convective longitudinal fins with temperature-dependent thermal conductivity and heat transfer coefficient. For thermal conductivity and heat transfer coefficient dominated by power-law nonlinearity, the exact temperature distribution is obtained analytically in an implicit form. In particular, the explicit expressions of the fin temperature distribution are derived explicitly for some special cases. An analytical expression for fin efficiency is given as a function of a thermogeometric parameter. The influences of the nonlinearity and the thermogeometric parameter on the temperature and thermal performance are analyzed. The temperature distribution and the fin efficiency exhibit completely different behaviors when the power-law exponent of the heat transfer coefficient is more or less than negative unity.

Numerical and Galerkin’s methods for thermal performance analysis of circular porous fins with various profiles when the surface temperature is higher/lower than the air temperature

ABSTRACT The main objective of this research is to analyze the optimization and the thermal performance of circular porous fins with three different profiles: rectangular, convex, and triangular under dry surface conditions. In this research, when the surface temperature of fin is higher or lower than the air temperature was studied. Also, modeling is assumed one-dimensional and the temperature changes only in the direction of the radius of the fin. Moreover, the thermal conductivity and heat transfer coefficient are a function of porosity and temperature, respectively. The governing equations are solved using the finite difference method and the Galerkin’s method. In this study, the effect of different parameters including porous parameter (SH) and porosity, fin efficiency, and fin effectiveness on temperature distribution were investigated. In both cases, the results showed that the fin temperature distribution should be decreased by increasing the porous parameter (SH) and porosity. In addition, in both cases, the results demonstrated that the efficiency and effectiveness for the rectangular profile are higher than other profiles. In this study, the total average absolute deviation percentage was calculated and its magnitude was 1 to 2.35%.

Theoretical modeling and optimization of fin-based enhancement of heat transfer into a phase change material

Phase change heat transfer is used commonly for enhanced thermal management and energy storage in several engineering applications. The rate of heat transfer from a heat source into a phase change material (PCM) is limited by thermal properties and geometry, due to which, the use of metal fins protruding into the PCM has been investigated. This paper derives and solves the governing energy conservation equations to determine the transient temperature distribution in the PCM due to the presence of a Cartesian fin. A perturbation method based solution for the Stefan problem with time-dependent temperature boundary condition is used to derive an equation for the fin temperature distribution. Results show that for a given total time available for heat transfer into the fin, the presence of a fin results in two competing effects – enhanced heat transfer into the PCM through the fin and reduced heat transfer into the PCM due to lower area of direct contact between PCM and heat source. This results in a non-monotonic dependence of total heat flow into the PCM on the fin size, and shows that a fin larger than a certain optimal size may actually impede overall heat flow into the PCM. For a given total time, the optimal fin size is shown to be a function of the fin thermal conductivity. The impact of thermal properties of PCM and fin on the rate of heat transfer is also examined. The theoretical work in this paper extends the well-known governing equation for a fin in a single-phase medium to a fin in a phase change material, which is a much more complicated, transient problem. In addition to extending the theoretical understanding of extended surfaces and phase change, this work also provides practical guidelines for the optimized design of phase change based energy storage and thermal management systems.

Coupled simulation of a thermoelectric generator applied in diesel engine exhaust waste heat recovery

This work develops a heat transfer model of a thermoelectric generator to explore the coupled relationship between high temperature exhaust flows, structure, and the external cooling air. The coupled heat transfer results showed that the fins reached a uniform high temperature, for the rated speed, the average temperature is 474 K. The coupled design scheme of the thermoelectric generator tested by installing it in a 4-cylinder turbocharged Diesel engine exhaust system. Comparison of the test and simulation results showed that as engine speed in-creased, the inlet and outlet exhaust temperatures of the thermoelectric generator exhibited a parabolic trend increase. The cooling water outlet temperature and the top, middle, and bottom fin temperatures increased linearly, and the coupled model was verified. From idle speed to rated speed, the top, middle, and bottom fin temperatures increased from 458 K to 476 K, 417 K to 463 K, and 406 K to 449 K, respectively; the cooling water outlet temperature increased from 293.6 K to approximately 303 K. Hence, the thermoelectric components installed in fins can experience temperature differences of over 100 K, the heat transfer efficiency can increase which ensures consistent output performance of the thermoelectric generator based on coupled design between the heat exchanger and thermoelectric modules array column.

Experimental study on convective boiling flow and heat transfer in a microgap enhanced with a staggered arrangement of nucleated micro-pin-fins

The boiling flow and heat transfer of FC-72 in a microgap channel are experimentally addressed. The heated surface of the microgap with a test area of 10 mm × 10 mm was enhanced using a staggered array of 613 columnar micro pin fins. Inside the micro pin-fins are nucleated with a 60 μm pore and opening of 45 μm. The test surface of the channel is a square of 10 mm, and the height of the channel is 100 μm. The saturation working temperatures of FC-72 is 50 °C, the surface heat flux was up to 60 kW/m2, and the mass flux was selected in the range of 94–275 kg/m2 s. The on nucleated boiling temperatures (ONB), convective heat transfer coefficient, outlet dryness, and pressure drop are measured and reported. The boiling behavior of FC-72 is also recorded using an image capturing device and reported. A comparison between the superheat temperature of nucleated pin fins and plane pin fins (with no nucleation) shows that nucleation of pin fins reduces the superheat temperature. The outcomes reveal that for a high mass flux, 196–275 kg/m2 s, the superheat temperature is high, and the degree of superheat increases as the surface heat flux increases. When the surface heat flux is high (q″ > 30 kW/m2), the convective heat transfer is almost independent of mass flux. At the initiation flow boiling, a notable jump in the pressure drops can be seen. After that, the pressure drop increases gradually by the increase in surface heat flux. The boiling images reveal that the boiling flow initiated inside the nucleation pores of micro pin-fins.

Non-Linear Model for a Spiral Porous Fin Subjected to Darcy Flow

In this study, the temperature distribution equation for a spiral porous fin is presented. Based on Darcy’s model, a mathematical equation of the energy is derived and a suitable dimensionless form is outlined to highlight some characteristic parameters, namely, the spiral fin pitch, the porosity, and the modified Rayleigh number. The behavior of the solution is analyzed for two cases of interest, taking into account the temperature-dependent thermal conductivity of the fin encountered in a hostile environment. A Numerical method is applied to solve this non-linear problem. It is found that the thermal transfer is not affected by the change of the spiral fin pitch, whereas increasing the porosity or the parameter β* makes higher fin temperature and improve the fin efficiency.

Thermal Performance of Phase Change Material Based Heat Sink for Solar Photovoltaic Cooling

Solar photovoltaic panels can receive only eighty percent of total incident solar radiation. A small amount of incident energy is transformed into electrical energy based on the efficiency of the photovoltaic (PV) cell. The remaining energy leads to an increase in photovoltaic cell operating temperature which affects its life and power output. Cooling of PV panel is the best way to improve the efficiency either by passive or active cooling methods. PV cooling by Phase change materials (PCM) is the best effective technique. Paraffin wax is a non toxic material having high latent heat of fusion used for many thermal applications. In this study, paraffin wax is taken as phase change material in aluminum heat sink with fins. Using DSC, the melting point of paraffin wax is analysed. The flat plate heater is used instead of solar PV panel. Different wattages are used for the experiments. Different inclinations such as horizontal (00), vertical (900) and intermediate (450) were taken in to consideration. The melting starts at 50oC and complete melting occurs at a temperature around 60oC for the paraffin based heat sink. The heat sink surface temperatures, fin temperatures and PCM temperatures are measured. The transient temperature distribution of heat sink, PCM is analysed at different wattage inputs. The total thermal performance of this paraffin PCM based heat sink was analysed experimentally. This infers that the cooling of high temperature of PV panels can be done by using paraffin based PCM to increase the efficiency and life of the panels.

Experimental and numerical investigation of heat transfer augmentation in heat sinks using perforation technique

Extended surfaces are commonly adopted as a thermal management technique for heat transfer augmentation owing to their ability to facilitate an increment in the available surface area, and hence, the total heat dissipation. This study aims at experimentally and numerically evaluating the performance of fins with and without perforated geometry under forced convection heat transfer. The effect of the circular perforations at different perforation number and size, airflow velocity, and different input powers on the thermal and hydraulic performance of those fins, at a constant perforation area of 24 cm2, has been examined. An excellent agreement has been observed between the experimental and numerical results. The findings of this investigation show that the thermal performance of the perforated fins is superior over the non-perforated ones with a reduction in fin temperature up to 8.5 °C. Further, increasing the size and number of perforations promotes the convective heat transfer process. On the other hand, the perforated fins offer an outstanding hydraulic performance compared to the solid ones since the flow friction factor and the required pumping power will be less, particularly with the increased number of perforations. Adopting the perforation technique has been discussed in detail, as well as significant experimental and numerical information has been reported in this article.

An analytical study of entropy generation in rectangular natural convective porous fins

Although, there are many studies on the second law analysis of solid fins, there are not enough investigations on the second law analysis and entropy generation of porous fins. The aim of this study is to establish a thermal analysis and to evaluate the performance of porous fins using the second law of thermodynamics. For this purpose, an analytical procedure is presented to obtain the entropy generation in two rectangular natural convective blades including very long and insulated-tip porous fins. One-dimensional heat transfer equation, the first and second laws of thermodynamics, were used to obtain two dimensionless nonlinear equations for the calculation of local temperature and entropy generation in the porous fins. The results of solving these equations showed that the entropy generation number is a function of SH, temperature ratio and non-dimensional local temperature of the porous fin. The results also indicated that, for both long and insulated porous fins, at given values of SH and the temperature ratio, the maximum entropy production occurs at the base of the fins with the maximum values of temperature difference. Moreover, based on the results of the study, two equations were proposed to estimate the average entropy generation number in long and insulated-tip porous fins. The effects of SH and temperature ratio on the local and average entropy generation number have been also investigated.

Approximate solutions and conservation laws of the periodic base temperature of convective longitudinal fins in thermal conductivity

In this paper, the residual power series method is used to study the numerical approximations of a model of oscillating base temperature processes occurring in a convective rectangular fin with variable thermal conductivity. It is shown that the residual power series method is efficient for examining numerical behavior of non-linear models. Further, the conservation of heat is studied using the multiplier method.

Numerical study on the natural convection from horizontal finned tubes with small and large fin temperature variations

This study numerically investigates the thermal performance of horizontal tube with circular fins under natural convection. The natural convection from horizontal finned-tube heat sink has been understood in an average sense since most previous studies were experiment-based. The present study reveals the flow and heat transfer characteristics in details with numerical analysis. The parameters include fin diameter (D), fin spacing (b), fin material, and tube diameter (d), under a fixed fin thickness of 0.5 mm and temperature difference of 50 K between the tube and the ambience. The distributions of fin temperature and heat transfer coefficients are calculated for stainless-steel (SS) and aluminum (Al) fins under various conditions. For Al fins with small fin temperature variations, decreasing tube diameter leads to higher heat transfer rates due to the larger fin surface areas; but for SS fins with large fin temperature variations, increasing tube diameter enlarges heat transfer rates. On large SS fins, negative local heat transfer coefficients may exist above the tube as the hot plume generated by the horizontal tube transfers heat back to the fin. A larger d leads to a slightly larger optimum fin spacing bopt. In addition, various existing empirical bopt formulae are examined for their reliability with respect to different D/d ratios and Al and SS fins, respectively with small and large fin temperature variations.

Analysis of unsteady heat transfer of specific longitudinal fins with Temperature-dependent thermal coefficients by DTM

Nowadays, with the development of heat transfer in various industrial fields, like as electrical and mechanical fields, we see the more effect of fins in this improvement. The computational price is hidden term of optimizing that can be included of CPU time and material optimizing can be included to modify the profile of fins. So in this paper have been investigated the heat transfer of fins with different profile (Convex, Concave, Triangular, Rectangular) in unsteady condition. The differential transform method (DTM) has been employed to solve this problem due in addition investigation of differences of temperature in fins, computational space become lesser. The boundary conditions are insulated tip with limited length and the thermal functions have been assumed for coefficient of heat transfer and conductivity. Then has been investigated the effect of relationship parameters like as (ε,β,θ,M). In unsteady condition these parameters are limited to one number that is useful in making optimum number. When β are increasing the temperate plot going in the upper level that show the efficiency going upper. In unsteady condition this parameter is limited to one number that it is very important for optimization by to build fins.