Radiative Fin Research Articles

Improving Heat Transfer Enables Durable Perovskite Solar Cells

AbstractSpecial attention should be devoted to the thermal stability of hybrid perovskite solar cells (PSCs), because they are often operated at elevated temperatures. However, effective strategies are lacking for manipulation of heat flow in PSCs to improve their thermal stability. Here, a holistic solution is reported for the rapid removal of dissipated heat within the absorber by introducing hexagonal boron nitride (h‐BN) inside and radiator fin outside of the device. This strategy significantly improves the thermal conductivity of perovskite and speeds up the heat transfer of device, which effectively reduces the cell temperature under illumination of simulated AM 1.5G standard spectrum by ≈6.5 °C. Regardless of device configurations, the corresponding PSCs exhibit prolonged lifetimes aged at different temperatures, continuously operated under white light‐emitting diode (LED) lamp or full‐spectrum illumination. Of particular note, the optimized h‐BN/Cu device with n–i–p structure keeps 88% and 93% of its initial PCE after 1776 h of 85 °C thermal aging and 2451 h of maximum power point (MPP) tracking, respectively, and the device with p–i–n structure maintains 96% and 92% of its original PCE after 1704 h of 85 °C thermal aging and 2164 h of MPP tracking.

Investigation of Heat Transfer from Convective and Radiative Stretching/Shrinking Rectangular Fins

We study the efficiency of shrinking/stretching radiative fins to improve heat transfer rate. To evaluate the competence of suggested fins, the influence of shrinking/stretching, thermogeometric parameters, surface temperature, convection conduction, radiation conduction, and Peclet number is investigated. The problem is solved numerically using a shooting method. To validate the numerical solution, the results are compared with the solution of a differential transform method. Temperature distribution increases with a rise in convection and radiation conduction parameters when Peclet number, stretching/shrinking, ambience, and surface temperatures are raised. The temperature of the fin’s tip increases as ambient temperature, Peclet number, and surface temperature increase, and decreases for enhanced radiation and convection conduction parameters. Radiation and convection cause the efficiency of the fin to increase for shrinking and decrease for stretching, which shows an important role in heat transfer analysis in mechanical engineering. The formulated model is also studied analytically, and the result is compared to numerical solution, which shows qualitatively good agreement.

The Characterization Analysis of the Oil-Immersed Transformers Obtained by Area Elimination Method Design

This study used the Area Elimination Method (AEM) of transformer design with transformer characteristic simulation. The multidimensional variable of physical parameters such as magnetic density, current density, voltage and coil turn was performed. This method was used in designing the 8000 kVA 22,000–3300/1905 V oil-type large distribution transformer. The result from a design found that the objective function tries to reduce the material to be used, and less core steel, less conductors, less transformer oil or less transformer tanks may cause an increasing load loss or increasing temperature rise, but we have calculated the temperature in the winding and design the radiator fins at the same time. After designing the transformer with AEM and it being manufactured in the production process, the transformer was tested according to IEC standards. It was confirmed that the power loss tests with no load yielded lower power loss than the standard value. In addition, the transformer passed the satisfaction test and the results of this design were built and tested with IEC 60076 standards. The information from the design using the Area Elimination Method could be a guarantee of standardized accuracy for oil distribution transformers. This also saves time and increases design efficiency for transformer designers.

A Novel Learning Approach for Different Profile Shapes of Convecting–Radiating Fins Based on Shifted Gegenbauer LSSVM

The purpose of this paper is to introduce a novel learning approach to solve the heat transfer problem from convecting-radiating fin model. This model is a nonlinear differential equation in which different boundary conditions cause different profile shapes including rectangular, triangular, trapezoidal and concave parabolic. We consider one-dimensional, steady conduction in the fin and neglect radiative exchange between adjacent fins and between the fin and its primary surface. Our method is based on using the quasilinearization method to linearize the nonlinear models and applying shifted Gegenbauer polynomials as new kernel in least squares support vector machines method. The results of fin efficiency and heat transfer rate of the problems which compared with available previous results indicate better efficiency and accuracy of the proposed approach.

Influence of Drainage and Tilt on Heat Transfer Performance of Array Pulsating Cold End Heat Pipe

Abstract To meet the heat dissipation of a horizontally mounted chip with high heat flow density, a new type of array pulsating cold end heat pipe was proposed, which consists of a T-shaped hot end and an array pulsating cold end. The special structure is available to drain the hot end of the heat pipe, and the installation method of the cold end has an important influence on heat transfer. For this reason, a detailed experimental study of heat transfer performance was carried out in this paper. It is found that: there is a capillary lifting force at the cold end interface, which prevents the condensate returning to the hot end; therefore, the hot end has to be drained; the drainage methods are divided into hot-end liquid drainage and hot-end capillary drainage, the latter is significantly better than the former; for liquid drainage, the appropriate increase of the filling rate can improve the drainage effect; according to the cold end installation method of the new heat pipe, it can be divided into two kinds of inclined heat pipe and vertical heat pipe, the heat transfer performance of both heat pipes are quite excellent, of which the inclined heat pipe has slightly better drainage and heat transfer performance than the vertical heat pipe, but the gap between the two gradually becomes smaller with the increase of power. Under the same operating conditions, the average temperature of the heat source of the inclined heat pipe with capillary drainage is lower than that of the aluminum fin radiator by 5.79%−10.78%, and the decreasing amplitude increases with the increase of the heating power.

Modeling and Performance Optimization of Louvered Fin Radiators in Negative Gauge Pressure Condition

AbstractThe purpose of this paper is to study the effect of the structural parameters of louvered fin radiators on its thermal‐hydraulic performance, optimize its structural parameters, and improve the performance of louvered fin radiators in negative gauge pressure condition. The thermal calculation model of louvered fin radiator in negative gauge pressure is established. Then, the effects of design variables on thermal‐hydraulic characteristics are investigated. The second generation of nondominated sorting genetic algorithm (NSGA‐II) is applied to optimize the louvered fin heat exchanger in negative gauge pressure environment. Technique for order preference by similarity to an ideal solution is applied to choose the final optimal solution. Numerical simulation of the solution is conducted and the result is compared with literature in order to verify the optimization method. The optimal structural parameters are obtained under constraints. Compared with the original test piece, the heat transfer rate of optimal solution is increased by 7.7%, and total annual cost is reduced by 24.8%. The present paper establishes optimization method of louvered fin radiators in negative gauge pressure condition, the optimization result is superior to the original radiator. The optimization method can be used in the design of radiators operating in negative gauge pressure conditions.

Effect of electromagnetic field on the thermal performance of longitudinal trapezoidal porous fin using DTM–Pade approximant

AbstractThe heat transfer and thermal distribution through porous fins have gotten a lot of attention in recent years due to their extensive applications in the manufacturing and engineering field. In porous fins, the impact of magnetic field aids in improved heat transfer enhancement. Also, the combination of an electric effect and a magnetic field considerably enhances heat transfer. In this direction, the thermal distribution through a convective–radiative longitudinal trapezoidal porous fin with the impact of an internal heat source and an electromagnetic field is discussed in the present analysis. The governing heat equation is nondimensionalized with nondimensional terms, and the transformed nonlinear ordinary differential equation is solved analytically using the DTM–Pade approximant algorithm. Furthermore, the graphical discussion is presented to explore the impact of various nondimensional parameters, such as convection‐conduction parameter, fin taper ratio, thermomagnetic field, radiation–conduction parameter, internal heat generation parameter, and thermoelectrical field on the temperature gradient of the fin. The investigation's key findings disclose that as the magnitude of the convection–conduction parameter, fin taper ratio, and radiation–conduction parameter increase, the thermal distribution through the fin reduces. The thermal distribution inside the fin increases for the heat‐generating parameter, thermoelectric, and thermomagnetic fields.

Improving design and operating parameters of the recuperator for waste heat recovery from rotary kilns

Depending on their applications, heat losses from the shells of rotary kilns account for 3-25% of the total heat input. Over the hottest zone of the kiln shell, an annular duct with a variable diameter is formed. Two air streams entering the annulus at both ends flow to a common extraction point to receive the thermal power equal to the ambient heat loss of the bare kiln. The design does not require airtightness, utilizes the entire heat loss, and by the variation of the air-flow can be used over the kilns with variable operating parameters (?20% heat loss), which show similar surface temperature patterns. The main disadvantage of the design is the approaching of the surfaces of the kiln and the recuperator at the outlet of preheated air. This means that for a given heat loss and a surface temperature pattern, the rotational eccentricity of the kiln shell is the most influencing parameter that defines the air preheating temperature and the efficiency of the recuperator. To solve the problem, four redesigns with: double annuluses, the usage of radiation fins, air addition, and a combination of two basic designs are analyzed by the use of analytical and CFD models. From the listed redesigns: first could be used only to prevent overheating, second has a modest positive effect, third should be applied in combination with fourth.

Two-Dimensional numerical parametric modeling of the capillary microgripper cooling system with unsteady fluid flow

The paper presents a parametric analysis of a 2D model of a fluid cooling system for the hot side of a Peltier element of a capillary microgripper. An unsteady flow of coolant in the cooling chamber is considered. The cooling efficiency is studied for three chamber geometries with different radiator locations: monolithic, located on the Peltier element; with one or three ribs. Mathematical models are built: fluid flow through the microgripper chamber; heating the radiator with the hot side of the Peltier element; heat transfer from the radiator to fluid and the removal of the heated fluid from the chamber. The simulation is carried out in the FreeFem++ program until the average change in the temperature of the radiator over the period of fluid oscillations reaches saturation (microgripper operating mode). Using the method of orthogonal central compositional planning, analytical dependences of response functions (maximum temperature on the radiator, amplitude of temperature change on the radiator, and time to establish the operating mode) on model factors (average coolant velocity, heat transfer coefficient, frequency and amplitude of fluid velocity oscillations) are obtained. For each considered geometry and response function, leading and insignificant factors are determined. A parametric analysis of the influence of the physical parameters of the system on the operation of the cooling system was carried out. The simulation results show that the geometry that provides a high degree of cooling and a faster exit to the operating mode (radiator with three fins) has a large amplitude of temperature fluctuations on the radiator and can be used in technical devices that are less sensitive to temperature fluctuations on the radiator. The single fin radiator geometry provides the least radiator temperature fluctuation and can be used to cool capillary microgripper.

Enhanced Heat Dissipation Performance of Automotive LED Lamps Using Graphene Coatings.

Graphene heat-dissipating coating (GNHC) of 0.6 wt % GN concentration is utilized to promote the cooling performance of automotive light-emitting diode (LED) lamps. Three cases are studied as follows: Case 0 is the original automotive LED lamp as the baseline. Case 1 is to apply GNHC to reduce the thermal resistance of the junction surfaces between the components of automotive LED lamps. The aluminum fin radiator of Case 1 is further coated with GNHC on the surface that becomes Case 2. The spectrum, illuminance, power consumption, and surface temperature are measured at different ambient temperatures (Ta) to fully evaluate the feasibility of applying GNHC to improve cooling performance and the impacts on the related characteristics of automotive LED lamps. The results show that the maximum illuminance efficacy of Case 1 and Case 2 with high beam, irradiation angle of 0 degrees, and Ta of 80 °C is 11.03% and 8.70% higher than that of Case 0, respectively. The minimum temperature difference of heat dissipation path of Case 1 and Case 2 with high beam, irradiation angle of 90 degrees, and Ta of 80 °C is 6.41% and 5.33% lower than that of Case 0, respectively, indicating GNHC as a promising coating material for improving the cooling performance of automotive LED lamps.

Joint Dependence of Longwave Feedback on Surface Temperature and Relative Humidity

AbstractVarious studies have suggested that Earth's clear‐sky outgoing longwave radiation (OLR) varies linearly with surface temperature, with a longwave clear‐sky feedback that is, independent of surface temperature and relative humidity. However, this uniformity conflicts with the notion that humidity controls tropical stability (e.g., the “furnace” and “radiator fins” of Pierrehumbert (1995, https://doi.org/10.1175/1520-0469(1995)052%3C1784:TRFATL%3E2.0.CO;2)). Here, we use a column model to explore the dependence of longwave clear‐sky feedback on both surface temperature and relative humidity. We find that a strong humidity dependence in the feedback emerges above 275 K, which stems from the closing of the O window, and that the furnace and radiator fins are consequences of this dependence. We then clarify that radiator fins are better characterized by tropical variations in clear‐sky feedback than OLR. Finally, we construct a simple model for estimating the all‐sky feedback and find that although clouds lower the magnitude of longwave feedback, the humidity‐dependence persists.

Optimal design and analysis of airfoil radiator fins based on weakly compressible turbulence

In order to further improve the heat dissipation performance of the forced air-cooled radiator in the simplest and most efficient way, this paper firstly proposes an airfoil optimization design of radiator fin structure. Then, based on the weakly compressible turbulence theory, a multi-physics coupling finite element model (FEM) that can highly restore actual phenomena is constructed. The temperature field, velocity field, and pressure field in the radiator are analyzed and verified qualitatively and quantitatively by this FEM. Finally, a comprehensive comparative analysis of the cooling power, average pressure loss, and cooling power per unit volume of traditional radiators and airfoil radiators are carried out in terms of the number of fins and the airflow rate. The results show that the performance of the airfoil radiator is significantly better than the traditional radiator: the cooling power is increased by at least 8.14%, the average pressure loss is greatly reduced, at least 31.15%, and the cooling power per unit volume is steadily increased by 15.92%. It can be seen that the optimized design can take into account both efficiency and practicality. The analysis methods and conclusions presented in the article have not only direct guiding significance for solving practical problems, but also have universal reference value for future research.

Optimal Design and Analysis of Airfoil Radiator Fins Based on Weakly Compressible Turbulence

Optimal Design and Analysis of Airfoil Radiator Fins Based on Weakly Compressible Turbulence

Study of the influence of the housing on the cooling efficiency of the piezoceramic electroacoustic Langevin-type transducer

The object of research is thermal processes in Langevin-type piezoceramic electroacoustic transducers (PET), taking into account the housing. The piezoceramic electroacoustic transducers heat up during operation. Overheating of the converter leads to negative consequences, accompanied by a change in the parameters, characteristics of the device, as well as the failure of the converter. Or limitation on the duration and mode of operation, output power, current, amplitude and speed of oscillation of the converter. The paper investigates the effect of the housing on the temperature field of a Langevin-type PET by the finite element method, using modeling in SolidWorks. The results of temperature reduction of such cooling methods are shown: – filling the housing cavity with electrical insulating liquid, gas, a mixture of thermal paste; – use of holes in the housing; – changing the shape of the rear cover to have radiator side fins, vertical radiator fins, cylindrical radiator fins; – heat-resistant layer; – use of active air cooling at three different speeds. The most efficient 53 % and a uniform temperature field were found when filling with a mixture of thermal paste, but this solution is accompanied by additional experiments and a preparatory stage with the mixture. The cooling efficiency of 47 % was provided by active cooling – blowing with air, and this method requires additional equipment. Filling with insulating liquid gave a cooling efficiency of 27 % – an optimal result that does not require expensive investments. Slow blowing of the housing or adding only holes resulted in a decrease in the maximum heating temperature from 10 to 20 %, therefore, if the PET design allows the presence of holes, then it is necessary to rationally place them. Changing the shape of the back plate, heat-absorbing element, filling the housing with gas gave an efficiency decrease in the maximum temperature by 6–8 % compared to a closed housing with air. The research results make it possible to choose the optimal option for reducing the heating temperature of the Langevin-type PET to increase its efficiency and long-term trouble-free operation.

Optimization of Air Cooling System Using Adjoint Solver Technique

Air cooling systems are currently the most popular and least expensive solutions to maintain a safe temperature in electronic devices. Heat sinks have been widely used in this area, allowing for an increase in the effective heat transfer surface area. The main objective of this study was to optimise the shape of the heat sink geometric model using the Adjoint Solver technique. The optimised shape in the context of minimal temperature value behind the heat sink is proposed. The effect of radiation and trapezoidal fin shape on the maximum temperature in the cooling system is also investigated. Simulation studies were performed in Ansys Fluent software using the Reynolds—averaged Navier–Stokes technique. As a result of the simulation, it turned out that not taking into account the radiation leads to an overestimation of temperatures in the system—even by 14 ∘C. It was found that as the angle and height of the fins increases, the temperature value behind the heat sink decreases and the heat source temperature increases. The best design in the context of minimal temperature value behind the heat sink from all analysed cases is obtained for heat sink with deformed fins according to iteration 14. The temperature reduction behind the heat sink by as much as 25 ∘C, with minor changes in heat source temperature, has been achieved.

Design and experimental research of test platform for characterizing a thermoelectric generator based on STM32

In order to solve the problem of low utilization rate of industrial low-grade thermal energy and actively implement the national policy of energy conservation and emission reduction, a low-temperature differential Thermoelectric generator device is designed and implemented based on the thermoelectric effect. According to the basic heat flow method of thermodynamics, the vertical installation sequence of the instrument is determined, and the simulated heat source is carried out in the laboratory. DJR-G type silicon rubber heater is used as the heating device, the fin radiator is used as the radiator and combined with the insulation layer to build the Thermoelectric generator test platform. STM32 microcontroller is the main control core of the instrument; tec1-12708t200 thermoelectric module is the power generation carrier; the main output characteristic parameters of the instrument are displayed on LCD in real time, and the change curve of the output parameters is monitored on the upper computer in real time. The experimental data show that when the load resistance is 2.5 Ω, it matches the equivalent resistance, and its output power reaches the maximum value; when the cold end of the Thermoelectric generator device is effectively cooled, its output power will increase by 0.1W. The conclusion shows that the instrument can effectively realize the Thermoelectric generator function and improve the utilization rate of low-grade thermal energy.

Thermal Management Techniques for Novel Single-Stage Collector of THz Folded Waveguide TWT

Folded waveguide traveling wave tubes (FW-TWTs) exhibit maximum potential in sub-THz to THz regime than its counterparts with respect to power and bandwidth, thereby facilitating its application in high data rate 6G communication systems. However, at high frequency, for synchronous and efficient interaction between electron beam and RF wave, FW-TWTs have to be operated at considerably high beam voltages. Furthermore, it has been reported that the interaction efficiency of FW-TWT is very poor; thus, most of the beam energy remains unspent. The efficiency of such devices may be increased by recovering the unspent beam energy in the collector. A corrugated single-stage collector has been designed with multiple periodic corrugations for an FW-TWT considering the size constraints. This geometry modification has resulted in self-trapping of secondary electrons and increased surface area yielding in >84% collector efficiency (~6% improvement in collector efficiency as compared with conventional collector). Detailed thermal and structural analyses of this collector have been carried out for different electrode materials, namely, copper and graphite. Various thermal management techniques have been employed to improve the thermal dissipation which includes forced air cooling, axial grooves on the outer envelope, and radiator fins. Simulation results reveal that a percentage reduction in the maximum temperature of 32.68%, 22.63%, and 72.59% has been achieved using forced air cooling, axial grooves, and radiator fins respectively. Further simulations also show a percentage decrease of 57.14% and 81.41% in the maximum collector temperature by using forced air cooling in combination with axial grooves and radiator fins, respectively. Based on the thermal and structural results, recommendations for the optimum thermal management technique have also been provided.

A method for evaluating the heat rejection efficiency in a Lunar power plant consisting of a free-piston Stirling engine (FPSE)

A method for evaluating the heat rejection efficiency in a Lunar power plant consisting of a free-piston Stirling engine FPSE is proposed. The waste heat from the FPSE is absorbed by the refrigerant circulating in a closed pumped loop and then rejected through a radiator into space. The magnitude of the heat flux rejected through the radiator is determined by the temperature difference between the radiator fins and surrounding environment, as well as the surface areas of the radiator and the emissivity coefficient. The method developed is used to qualitatively evaluate the refrigerant efficiency based on calculating the average temperature of the radiator fin which is established during the heat exchange process in the radiator. The method allowed us to determine the most efficient refrigerant in terms of maximum heat rejection at a given operating temperature range without the need of detailed calculations like in the previous works of the authors. Computational studies in a two-dimensional formulation of the radiator, using helium or liquid ammonia as a refrigerant, to determine the quantitative characteristics of the heat rejection process and overall dimensions of the radiator were performed, and a comparative analysis of the results is presented.

Thermal Analysis of Conductive-Convective-Radiative Heat Exchangers With Temperature Dependent Thermal Conductivity

In this paper, one dimensional mathematical model of convective-conductive-radiative fins is presented with thermal conductivity depending on temperature. The temperature field with insulated tip is determined for a fin in convective, conductive and radiative environments. Moreover, an intelligent soft computing paradigm named as the LeNN-WOA-NM algorithm is designed to analyze the mathematical model for the temperature field of convective-conductive-radiative fins. The proposed algorithm uses function approximating ability of Legendre polynomials based on artificial neural networks (ANN’s), global search optimization ability of Whale optimization algorithm (WOA), and local search convergence of Nelder-Mead algorithm. The proposed algorithm is applied to illustrate the effect of variations in coefficients of convection, radiation heat losses, and dimensionless parameter of thermal conductivity on temperature distribution of conductive-convective and radiative fins in convective and radiative environments. The experimental data establishes the effectiveness of the design scheme when compared with techniques in the latest literature. It can be observed that accuracy of approximate temperature increases with lower values of Nc and Nr while decreases with increase in λ. The quality of solutions obtained by LeNN-WOA-NM algorithm are validated through performance indicators including absolute errors, MAD, TIC, and ENSE.

Study on the air-side flow and heat transfer characteristics of corrugated fin under low-pressure environment

ABSTRACT Many troubles appear when vehicles work in the plateau region, and the main reason is that the heat-transfer capability of radiator in the vehicle cooling system reduces under the plateau low air pressure environment. Hence, the research on the flow and heat transfer characteristics of radiators in plateau low air pressure environment is necessary. In this paper, the experimental study on the thermal-hydraulic characteristics of corrugated fin radiator is conducted on a wind tunnel test-bed with low pressure function. The results illustrate that the air-side convective heat transfer coefficient of the corrugated fins decreases with the decrease of the ambient pressure, and the Colburn factor (j) and Friction factor (f) increase simultaneously. When the gauge pressure is −44 kPa, the air-side convective heat transfer coefficient is 34% lower than that under normal pressure on average, and the Colburn factor and Friction factor increase by an average of 21.1% and 55.6%, respectively. On this basis, the entransy dissipation and field synergy angle distribution of the corrugated fin radiator under low-pressure environment are studied. It is showed that the entransy dissipation number at −44 kPa gauge pressure reduces by 65% on average. The air-side field synergy angle increases with the decrease of the ambient pressure. Finally, the experimental correlations of the Colburn factor and Friction factor are performed, and the average deviations of the calculated results are 2.8% and 3.3%, respectively.