Search

Indoor heating with an electrical heating cable, which has no harmful emissions to the environment, is an attractive way for radiant floor heating. To improve the heat transfer efficiency, a novel structure of the heating cable was designed by proposing the concept of the aluminum finned sheath. The transient heat transfer model from the embedded heating cables to the floor is established to validate the feasibility of this novel cable. The effects of the fin number and shape on the cable's temperature and heat flux distribution were analyzed. The results show that, with the specific volume of the sheath, increasing the number of fins can enhance the thermal diffusion capacity of the heating cable and reduce its temperature. Rectangular fins exhibit higher performance for heat dissipation than triangular fins due to their larger surface area. The simulation result shows that the floor temperature above the cable rises from 5°C to 22.5°C after a 2-h heating process, which was validated with experimental results. The results and suggestions can provide reference to guide the design of the heating cable. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) units featuring phase change materials (PCMs) have a crucial impact on efficient energy management. Since energy demands keep changing, and the world increasingly relies on sustainable energy sources, innovation is continuously required. New technologies, materials, and methods for energy storage must be developed to meet these shifting needs effectively. In this study, a triplex-tube heat exchanger (TTHE) was employed as a TES medium, utilizing PCM within the middle tube. Because of its high thermal energy storage capacity, RT50 was selected as the PCM. Four innovative arc-shaped fins were strategically integrated within the PCM space to accelerate heat release. The system was subjected to rotational speeds of 0.1, 0.3, 0.5, 1, and 1.5 rpm. The investigation was carried out in two stages: initially, the impact of varying rotational speeds on the discharging process of the PCM in a finless TTHE was explored; subsequently, the influence of the same speeds on the solidification behavior of the finned TTHE was analyzed. Natural convection and PCM’s solidification process were examined through the enthalpy-porosity method. The findings represented that in the absence of fins, the device’s rotation had a more noticeable impact on the solidification behavior; however, incorporating fins was much more influential. Up to 2850 s, all the finned systems had solidified entirely in the presence or absence of the rotational mechanism, while in the finless system with a rotational speed of 1.5, 30.52 % of the material was still unsolidified until this time. Finally, the influence of three key structural parameters of the fins: α (outer fins arc angle), β (inner fins arc angle), and S (space between fins) on the discharging time of the PCM was analyzed using an artificial neural network (ANN) model. The study offered critical insights for optimizing fin configuration by systematically varying these parameters within defined ranges. An ANN predictive model was also proposed to assist TES system manufacturers and developers in future design and optimization efforts. The results demonstrated that the optimal setting of the TTHE (with the parameters of α = 60°, β = 60°, S = 10 mm) achieved the liquid fraction of 0.1, 80.33 % faster than the finless system.

Efficient heat transfer is important for metal hydride hydrogen storage tank to charge or discharge rapidly. In this work, three heat transfer fin structures were built and they are "Inner-Fin", "Outer-Fin", and "Inter-Fin", respectively. The impacts of fin structures on temperature evolution and hydrogen absorption performance of metal hydride hydrogen storage tank were studied and then optimized by establishing mathematic models and using finite element method for numerical simulation. Compared with the traditional Inner-Fin structure, the Inter-Fin and the Outer-Fin structures can increase the heat transfer efficiency by 16.9% and 38.5%, respectively and increase the hydrogen absorption efficiency by 20% and 40%, respectively. The novel fin structures proposed in this work is efficient to improve the heat transfer performances of the hydrogen storage tank and is relatively simple and easy to manufacture, which is suitable for practical application. This work provides a reference for the structure design of metal hydride hydrogen storage tanks. [Display omitted] • Inner-Fin, Inter-Fin, and Outer-Fin were built and installed in the tank. • Fins greatly enhances the heat transfer and hydrogen absorption of tank. • Tank with Outer-Fin exhibits the best hydrogen storage performances. • Larger fin length and denser fin distribution are beneficial to the heat transfer. • Fin structures proposed in this work is efficient and easy to manufacture. [ABSTRACT FROM AUTHOR]

Abstract The study of the heat exchangers in the trapezoidal channels and the rectangular channels were carried out. The trapezoidal channel has smaller friction resistance than the rectangular channel with equal section, and the friction factor (f) decreases gradually with the increase of inclination angle, when β= 25 °, the f is the smallest, which is reduced by nearly 22.6% compared to the rectangular channel with equal cross-section; when , the heat transfer factor (j) and comprehensive heat transfer performance of the trapezoidal channel are greater than those of the rectangular channel with the same section, and when , those increase by 8% and 20%, respectively. The height and length of fins have a significant impact on heat transfer performance, increased by 17.65% and 20.85% respectively; By analyzing the comprehensive performance of the trapezoidal channel, the # 8 structure (Fh=10.5mm, β=5°, Sf=3mm, Lf=45mm, tf=0.3mm) has the optimal performance. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) are incorporated with higher energy density batteries to improve the driving range and performance. The lithium-ion batteries with higher energy density generate a larger amount of heat which deteriorates their efficiency and operating life. The currently commercially employed cooling techniques are not able to achieve the effective thermal management of batteries with increasing energy density. Direct liquid cooling offers enhanced thermal management of battery packs at high discharging rates compared to all other cooling techniques. However, the flow distribution of coolant around the battery module needs to be maintained to achieve the superior performance of direct liquid cooling. The objective of the present work is to investigate the heat transfer characteristics of the lithium-ion battery pack with dielectric fluid immersion cooling for different fin structures. The base structure without fins, circular, rectangular and triangular fin structures are compared for heat transfer characteristics of maximum temperature, temperature difference, average temperature, Nusselt number, pressure drop and performance evaluation criteria (PEC). Furthermore, the heat transfer characteristics are evaluated for various fin dimensions of the best fin structure. The heat transfer characteristics of the battery pack with dielectric fluid immersion cooling according to considered fin structures and dimensions are simulated using ANSYS Fluent commercial code. The results reveal that the symmetrical temperature distribution and temperature uniformity of the battery pack are achieved in the case of all fin structures. The maximum temperature of the battery pack is lower by 2.41%, 2.57% and 4.45% for circular, rectangular, and triangular fin structures, respectively, compared to the base structure. The triangular fin structure shows higher values of Nusselt number and pressure drop with a maximum value of PEC compared to other fin structures. The triangular fin structure is the best fin structure with optimum heat transfer characteristics of the battery pack with dielectric fluid immersion cooling. The heat transfer characteristics of a battery pack with dielectric fluid immersion cooling are further improved for triangular fin structures with a base length -to -height ratio (A/B) of 4.304. The research outputs from the present work could be referred to as a database to commercialize the dielectric fluid immersion cooling for the efficient battery thermal management system at fast and higher charging/discharging rates. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage (LHTES) has received more and more attention in the thermal energy storage field due to the large heat storage density and nearly constant temperature during phase change process. However, the low thermal conductivity of phase change material (PCM) leads to poor performance of the LHTES system. In this paper, the research about heat transfer enhancement of PCM using fin tubes is summarized. Different kinds of fins, such as rectangular fin, annular fin, spiral fin, etc., are discussed and compared based on the shape of the fins. It is found that the longitudinal rectangular fins have excellent heat transfer performance and are easy to manufacture. The effect of fins on heat transfer enhancement is closely related to the number of fins and its geometric parameters. [ABSTRACT FROM AUTHOR]

In this paper, the thermal management of missile-borne components in a flight state is studied. Avoiding excessive component temperatures under the high-temperature circumstances brought by aerodynamic heat is a requirement to guarantee the equipment's safe and reliable operation. In this work, we designed four finned shell constructions for a phase change module using the phase change temperature control method and then studied their effects on the module's ability to dissipate heat using an experimental approach. Three sizes of 30 mm, 40 mm, and 50 mm heating pads were used to replicate heat sources with various heat flux densities and heat dissipation regions, with reference to the heating characteristics of various chips. The results demonstrated that the square-shaped fin had the best heat dissipation effect after operating for 10 min under the power of 10 W and 20 W, while the strip-shaped fins exhibited the highest performance under the power of 30 W. The square-shaped fins had the best heat dissipation effect when reducing working time to 5 min. This paper proposes the optimal fin scheme under different power densities, as well as an enhanced heat dissipation idea for the melting process of the phase change materials based on the test results. [ABSTRACT FROM AUTHOR]

Copyright of Transactions the Japan Society of Refrigerating & Air Conditioning Engineers is the property of Japan Society of Refrigerating & Air Conditioning Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present the design, fabrication, and characterization of suspended arrays of small volume, high quality factor (Q) silicon nitride photonic crystal nanobeam (PCNB) cavities with lateral nanorod fin structures. By controlling the alignment position of the fins with respect to the air holes, the resonance wavelength and Q-factor of the PCNB cavities can be tuned to realize the desired performance. Measured tunable range of 2 × 104 and 10 nm is achieved for Q-factor and resonance wavelength, respectively, with the highest Q-factor measured at 2.5 × 104. Incorporating such nanorod fins into the nanobeam cavity is demonstrated to provide improved mechanical support, thermal transport, and channels of lateral carrier injection for the suspended PCNB. The proposed PCNB cavities with lateral fins are advantageous for energy efficient, ultra-compact lasers, modulators, filters, and sensors.

The automotive lighting industry is changing at a rapid pace, thanks to advances in technology. Automotive lighting equipment is produced with more functionality and higher performance. However, with the increase in performance, undesirable heat generation also increases. Automotive headlights fail or perform poorly when exposed to high heat; therefore, unwanted heat has to be removed. This is accomplished with heat sinks. In this study, four different automotive light-emitting diode (LED) headlights have been designed as channelless, 4-channel, 8-channel, and 12-channel. The designed models were tested numerically at different LED powers (8,10,12,14, and 16W). Thus, the impact of heat sink fin structures on the thermal performance of automotive LED headlights was investigated numerically. The heat dissipation performances of the designs were analyzed using the computational fluid dynamics software SolidWorks Flow Simulation. The simulation results showed that the designed products can be used as LED headlights. As the applied heat power increased, maximum temperatures also increased. While a continuous increase in performance was achieved in designs up to 8-channel, slight performance degradation was observed when the number of channels reached 12. As the applied heat power increased, the average temperatures increase whereas thermal resistance (Rth) decreased. From channelless design to 12-channel design, Rth values decreased from 6.8 °C/W to 5.31 °C/W. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage (LHTES) based on phase change materials is one of the key technologies to improve energy utilization efficiency and alleviate the mismatch between energy supply and demand. Heat storage capacity and charging/discharging rate are two core factors that determine the comprehensive performance of LHTES units. So a bi-objective transient topology optimization(TO) model is established to freely evolve the optimal structure and volume fraction of LHTES fins to maximize the heat transfer rate based on ensuring high storage capacity. The bi-objective optimization function coupling storage capacity and heat transfer rate is constructed by normalized SAW model. The TO model is formulated using variable density-based design variables of grid cells in physical governing equations, objective functions and constraints. Helmholtz PDE filtering and hyperbolic tangent projection methods are employed to achieve high-precision optimization solutions. Complex transient multi-physics field and bi-objective iterative calculations are performed using the transient adjoint-based sensitivity analysis method and GCMMA algorithm. Results demonstrate that the physical field dynamics response of the design variables at each iteration can more clearly exhibit the evolutionary direction and mechanism of seeking optimal structures. The Pareto frontier indicates TO model responds significantly to the changes in the bi-objective weight ratio ω 1 : ω 2 , which also reveals the physical mechanism of the trade-off game among fin topology formation, state parameters distribution and objective changes. Optimal configurations and its performance parameters change regularly with ω 1 : ω 2 decreasing, and has an demonstrable performance mutations occurring at ω 1 = 0.65(ω 2 = 0.35). The scattered distribution and uniform multi-branch structure of TO fins are key factors in regulating the physical field state. Therefore, TO-fins LHTES exhibits extremely high heat transfer rate, and the charging/discharging time of traditional trapezoid fin LHTES is approximately three times longer than that of TO-fins LHTES under ω 1 : ω 2 = 0.65:0.35. • A bi-objective transient topology optimization model is proposed for LHTES design. • Modified algorithms and convection effect are applied in mathematical model. • Reveal the influence law of weight factors on optimal structures and performance. • Melting and solidification of optimized LHTES structure are greatly enhanced. [ABSTRACT FROM AUTHOR]

A water evaporator is a phase change heat exchanger, as a heat sink, especially for high-speed flight vehicles. It is composed of internal channels for convective cooling and external fins for boiling. In this paper, six water evaporators, Hex0–Hex5, are designed with five different internal channels and two different external fins. The VOF simulation models are built to investigate their boiling heat transfer performances in a sub-atmospheric environment. Experimental studies were carried out to verify the accuracy of the numerical model of water evaporator. The simulation results show that the structures of the internal channel and external fin both have an impact on the heat transfer performance. For the internal channels, their height change has much more obvious effect than their structural continuity. For the external fins, the increase of the fin bulge structure helps to improve the heat transfer performance. For the aircraft, the optimal design structure of water evaporator is Hex4 and its heat transfer performance can be improved by 13.31% compared with Hex0.

In this paper, the thermal management of missile-borne components in a flight state is studied. Avoiding excessive component temperatures under the high-temperature circumstances brought by aerodynamic heat is a requirement to guarantee the equipment’s safe and reliable operation. In this work, we designed four finned shell constructions for a phase change module using the phase change temperature control method and then studied their effects on the module’s ability to dissipate heat using an experimental approach. Three sizes of 30 mm, 40 mm, and 50 mm heating pads were used to replicate heat sources with various heat flux densities and heat dissipation regions, with reference to the heating characteristics of various chips. The results demonstrated that the square-shaped fin had the best heat dissipation effect after operating for 10 min under the power of 10 W and 20 W, while the strip-shaped fins exhibited the highest performance under the power of 30 W. The square-shaped fins had the best heat dissipation effect when reducing working time to 5 min. This paper proposes the optimal fin scheme under different power densities, as well as an enhanced heat dissipation idea for the melting process of the phase change materials based on the test results.

Condensation of refrigerant R-134a is experimentally investigated on a paraffin-coated copper surface and compared to condensation on a plain copper surface. Heat transfer and visualization experiments are conducted for vertical-plate samples and for two different fin structures at various degrees of subcooling. A one-dimensional heat conduction model is used to interpret the condensation heat transfer measurements, while liquid retention behavior is quantified with the aid of image processing. The experimental results on vertical plates show that the heat transfer is enhanced on the coated surface with a maximum increase of 27% in the condensing heat transfer coefficient. On fin structures, the liquid retention was reduced by up to 28% on a coated surface. The heat transfer and retention behavior vary with surface material, degree of subcooling, and fin geometry. [ABSTRACT FROM AUTHOR]

With the incremental power of construction machinery diesel engines, the power performance of diesel engines and the pollutant emissions from the exhaust gas have imposed increasingly stringent requirements on the intake cooling system of diesel engines. This paper compared the j/f evaluation factors for fin unit bodies of water-cooled intercooler (including straight fins and rectangular misaligned fins) by means of CFD simulation, and found that the rectangular misaligned fins had an 8% advantage in comprehensive performance. With the rectangular staggered fin intercooler, it was found that under the same conditions, the cooling efficiency of the dual-pass water-cooled intercooler is higher than that of the single-pass water-cooled intercooler, and the uniformity factor of the temperature difference field of the dual-pass water-cooled intercooler is 1.5% higher than that of the latter. The accuracy of the overall simulation of the intercooler is verified by the field test. The dual-pass and single-pass water-cooled intercooler both can maintain heat balance under working conditions, and its average air inlet temperature is 10 °C lower than that of the original air-cooled intercooler, which provides support for further reducing the engine air inlet temperature. The results provide a theoretical basis for the performance improvement of water-cooled intercoolers.

In order to save heating energy and reduce carbon emission intensity, a floor heating room with built-in finned Trombe wall in Xining, Qinghai, a severe cold area, was taken as the research object. And ANSYS 2021 R1 was used to numerically investigate the effects of several major factors, such as fin height, fin transverse distance, fin longitudinal distance, fin inclined angle, fin shape, perforated shape and perforation ratio of perforated fin, on the average heat transfer coefficient (h) between the absorptive surface and the air in the interlayer. The results show that for fins with low heights, the enhancement effect of horizontal fins on the convective heat transfer of the absorptive surface of Trombe wall is greater than that of vertical fins. The enhancement effect of vertical fins on the convective heat transfer of the absorptive surface is more affected by fin transverse distance, while the enhancement effect of horizontal fins on the convective heat transfer of the absorptive surface is more affected by fin longitudinal distance. Besides, h shows a trend of first increasing and then decreasing with the increase of fin inclined angle, and reaches its maximum value of 5.89 W/(m2·K) at 45°. The fins with different shapes are equilateral triangular fins, semicircular fins, isosceles triangular fins and rectangular fins in descending order of their enhancement effect on the heat transfer of wall. Compared with solid fins, fins with circular holes can obtain a better convective heat transfer effect only when the open area ratio is 1:6. While fins with equilateral triangular holes can obtain better convective heat transfer effect as long as the open area ratio is greater than 1:7. Fins with elliptical holes do not significantly improve the heat transfer effect. On the basis of optimizing the fin layout and structure, the thermal performance of the improved Trombe wall during the 8:00∼16:00 period and its impact on indoor thermal comfort of the building were studied, and the energy-saving performance of the plan was discussed. Compared with the Trombe wall room with no fins, the improved Trombe wall can improve the heat teransfer efficiency and the building energy saving rate by 68.50 % and 53.57 %, respectively. The improved Trombe wall can only ensure the indoor thermal comfort in limited several hours, in the rest of time, the residents should add clothing to keep warm. These conclusions have an important effect of engineering guidance and great realistic meanings for promoting the process of solar building integration and achieving the "carbon peak and carbon neutrality" target. [ABSTRACT FROM AUTHOR]

Realizing conversion between fluid power and mechanical energy, the closed circuit axial piston transmission (CCAPT) plays a vital and indispensable role in miscellaneous industries. The frictional loss and leakage loss inside the system give rise to the inevitable temperature rise. In order to prolong the life of the device, a cooling structure on the outside of the CCAPT is designed for promoting heat dissipation. Based on the relevant heat transfer law and the temperature distribution of internal machinery elements, a spiral fin structure is designed at the shell side. With the help of numerical simulation, the effects of fin height, fin pitch, and fin thickness on the thermal performance are studied. The flow field and temperature field on the outside of the fin structure are obtained as a guidance for enhancing heat dissipation effect. Results indicate that the area of rotating elements tend to accumulate heat, where more attention should be paid for a better cooling effect. In addition to this, a moderate increase of fin height, fin pitch and fin thickness has a positive effect on heat transfer enhancement. The peak value of Nusselt number is obtained with a fin height of 7.5 mm, which is about 2.09 times that of the condition without the fin structure. An increase in fin pitch improves both heat transfer performance and comprehensive performance at the same. When fin pitch is 30 mm, Nusselt numberincreases 104% over the original condition.

A buried gate fin p‐body insulated gate bipolar transistor (BG‐Fin‐P IGBT) is proposed to achieve ultralow on‐state voltage drop (VCE(sat)) and good short‐circuit (SC) ruggedness simultaneously. A buried gate is introduced at the bottom part of the fin structure, forming a local region with the nanoscale mesa width, which enhances the conductivity modulation effectively. Meanwhile, a relatively wide mesa width (>0.5 μm) can be adopted at the main fin structure to maintain a good SC capability. Compared to the previously reported ultra‐narrow‐mesas fin p‐body IGBT, simulation results reveal that the VCE(sat) of the BG‐Fin‐P IGBT is reduced from 1.39 to 1.03 V at the current density of 100 A/cm2 without SC ability degradation. Meanwhile, more than 10 μs short circuit withstand time is enabled at the junction temperature of 423 K for all structures. Moreover, the proposed structure can avoid a fabrication difficulty of the emitter contact when a very narrow mesa width (∼30 nm) is required to achieve the ultralow VCE(sat), which brings design freedom on the device's structure. [ABSTRACT FROM AUTHOR]

Highlights • Falling film flow mode transition on 2D finned tubes is studied experimentally. • Large tube spacing delayed the appearance of sheet mode under increasing flow rate. • Large tube spacing prolonged the sheet mode under decreasing flow rate. • The hysteresis in mode transition was enhanced by the increase in h /(p − t). • New correlations for flow mode transition on 2D finned tubes were proposed. Abstract This study proposed a correlation of Reynolds number (Re) for falling film mode transitions on horizontal enhanced tubes with 2D integral fins on the basis of an analysis of experimental data from current and previous studies considering the effect of tube spacing and fin structures. Transitional Re for flow mode transitions are analyzed on the basis of observing water falling film flow on four types of 2D finned tubes (ranges of fin height h , fin pitch p , and fin tip t of these tubes are 0.503–1.050 mm, 1.04–2.80 mm, and 0.31–1.27 mm) and smooth tubes under various tube spacings (s , including 6, 10, and 15 mm). Results show that large tube spacing delayed the appearance of sheet mode under increasing flow rate but prolonged the sheet mode under decreasing flow rate. This hysteresis phenomenon was enhanced by the increase in h /(p − t). The proposed correlation, which linked the transitional Re with three dimensionless groups (i.e., Galileo number (Ga), s / ξ and h /(p − t)) and a constant, predicted seven groups of transitional Re for the column–sheet and sheet within ±14.7%. This correlation could be applicable to the 2D finned tubes with 19 ≤ Ga 1/4 ≤ 407, 2.19 ≤ s / ξ ≤ 5.49, and 0.33 ≤ h /(p − t) ≤ 27.67. [ABSTRACT FROM AUTHOR]

• The optimization parameters have important influence on the topology structure. • With different volume ratios, the topological structures are clear and complete, and all have good radial extensibility. • The heat transfer area is larger and the heat transfer path is more reasonable, which is conducive to heat transfer. • The topology structure has good heat transfer characteristics. In the latent heat storage (LHS) system, topology optimization was applied to the design of the fin structure, and the material variable density interpolation method was adopted. Given the effect of natural convection heat transfer on heat transfer characteristics, the buoyancy source term and resistance source term were introduced in the momentum conservation equation to establish a mathematical model of heat transfer and topology of the heat storage system. To obtain a reasonable topology, we analyzed the effects of optimization parameters such as penalty factor, filter radius, steepness factor and threshold value on the topology. Then, four typical topologies were selected for heat transfer and flow analysis. The results show that at 500 s, Case 1 is nearly half melted, while Case 4 is almost completely melted. It can be seen that more branch structures and radial extension in Case 4 provide a larger heat transfer area and a more reasonable heat transfer path, which improves the uniformity of the temperature field and significantly increases the heat transfer rate. This study can provide a theoretical basis for topology optimization in the structural distribution of fins in the LHS system. [ABSTRACT FROM AUTHOR]

• The heat transfer performance of two fin structures, namely regular and modified fins, was experimentally studied in a pool boiling facility. • An artificial nucleation site was fabricated on the heated surface to enhance the heat transfer performance. • The modified fin with the artificial nucleation site showed higher heat transfer performance than the regular fin. • A multilayer perceptron artificial neural network is applied for modeling the bubble departure diameter in boiling. Boiling heat transfer associated with phase change is perhaps one of the most efficient cooling methodologies to manage extreme heat flux due to its large latent heat. Fin structures are used to further increase the magnitude of boiling heat transfer from the heated surface and have shown better performance than flat surface heat sinks. This work aims to experimentally investigate the heat transfer performance of two fin structures, namely regular and modified fins, in a pool boiling facility. The modified hollow fin structure is designed to enhance the regular fin's heat transfer performance by adding an artificial nucleation site. Heat transfer rates and heat transfer coefficients of the two fin structures are estimated in atmospheric pressure conditions using deionized water and compared with the literature. The results show that the regular fin heat sink shows a better heat transfer rate than the plane surface, while the modified fin structure shows higher heat transfer performance than the regular fin. This is attributed to the additional nucleation sites on the hollow fin, a better rewetting phenomenon, and therefore a favorable bubble growth and release mechanism. Also, a multilayer perceptron artificial neural network with a back-propagation training algorithm is applied for modeling the bubble departure diameter concerning wall superheat and subcooling level to predict the bubble behavior from the artificial nucleation site. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper involves an exhaust gas waste heat recovery system for vehicles, which uses thermoelectric modules and a heat exchanger to produce electric power. Based on summarizing the latest research of vehicle exhaust thermoelectric generator, it presents two new fin structures for the cylindrical heat exchanger in a thermoelectric generator system. It mainly studies the thermal performance of two kinds of 3-D cylindrical heat exchanger models including spiral-fin heat exchanger with variable pitch in a CFD simulation environment. In terms of interface temperature and thermal uniformity and based on an evaluation method of the temperature uniformity for the heat exchangers, the thermal characteristics of heat exchangers with different pitch angle of the twisted fins, pitch of spiral fin, fin thickness, and fin height are discussed. Two new fin structures are feasible to enhance the heat transfer performance of heat exchanger. [ABSTRACT FROM AUTHOR]

The thermal behavior of the cylindrical battery was examined with composite paraffin and fin structure through experimental measurements and benchmarking with other thermal management techniques. The mock-up cylindrical battery, made of aluminum, had vertical straight fins as enlarged heat transfer area to submerge in the paraffin wax as phase change material (PCM) with a maximum melting temperature of 44 °C. For the pure PCM case, the melting process could be divided into AB segment with battery temperature ramp-up, BC segment with a clear-cut temperature plateau, and CE segment to reach complete melting, which is also basically represented in the evolutionary trend for the battery top to bottom temperature variation. The instantaneous Nusselt number would increase around the CE segment with a small portion of unmelted PCM as visualized by the numerical analysis, but the battery temperature would ramp up from the plateau in spite of the incomplete melt. Thermal enhancement with the PCM-fin cases was examined experimentally and the logarithmic dependence of the time-averaged Nusselt number is correlated with the heat transfer area ratio. In addition, the effective thermal control point C is found to relate to the melting front intersecting the bottom of the metal housing, and the corresponding thermal resistance is used to benchmark the thermal performance of PCM based thermal management systems. Independent of heating power, such a parameter can be correlated with the melting temperature to the ambient temperature difference for existing thermal management systems. It is found that the present composite PCM-fin system had the advantages of good thermal performance with prolonged work time. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• PCM melting in a finned cold thermal energy storage tank is studied. • Geometric structures of fins can significantly affect the melting process. • Increasing fin height is more effective than increasing fin number to reduce melt time. • Mean power with new stratified fin design is 156.3% higher than that without fins. Cold thermal energy storage (CTES) is of great importance for the enduring decrease in fossil fuel energy consumption. Moreover, CTES with phase change materials (PCMs) can be an effective measure to accumulate the heat or cooling energy for overcoming the mismatch between the supply and demand of air conditioning loads, augmenting system dependability and flexibility in operations of power grids. This paper numerically and experimentally examines the melting characteristics of PCM inside a CTES tank with the installation of interior fins. The computational fluid dynamics (CFD) software ANSYS/Fluent® is applied to predict the time sequences of liquid fraction contours and temperatures in comparison with the photographed images of ice-liquid water interface and measurement data in the CTES tank to verify the accuracy of CFD predictions. The simulations by the validated CFD model are extended to evaluate the influences of fin height and total number of longitudinal fins on the heat transfer outcomes in the storage tank. The present study further proposes a novel design adopting stratified fins to enhance the melting performance of the CTES device. The estimated mean power with the new stratified fin design is notably greater than that without fins by 156.3%, achieving the effectively liquefaction enhancement of ice for guiding the development of finned cold thermal energy storage. [ABSTRACT FROM AUTHOR]

The adipose fin of salmonids, once widely regarded as vestigial and lacking in function, was shown to be important to swimming efficiency in juvenile brown trout Salmo trutta. Examination with confocal microscopy of adipose fins of S. trutta stained with various antibodies targeting the nervous system revealed several large nerves entering the fin and anastomosing throughout its length. The branching nerves form a plexus with specific patterns of fine terminal branches in the leading and trailing edges. A network of astrocyte-like cells ( ALCs) that is linked through cell processes to nerves and structural collagen reacted positively with antibodies to glial cells. No other fish fins, including other adipose fins, have been shown to exhibit this type of neural architecture. Many vertebrate mechanoreceptors rely on collagen deformation to stimulate responses in afferent nerves; similarly, the adipose fin also may function as a mechanosensor, where passive mechanical deflection by water currents stimulates afferent nerves. [ABSTRACT FROM AUTHOR]

The influence of fin structure and density on the condensation heat transfer of refrigerant 1,1,1,2-tetrafluoroethane (R134a) is investigated on single finned tubes and in corresponding bundles. Experiments have been performed on standard and enhanced finned tubes with 39, 48, and 56 fins per inch (FPI) and different fin heights. The enhanced finned tubes are based on the standard ones, and are characterized by a non-uniform fin structure. The condensation heat transfer coefficient (HTC) is determined for single tubes as well as for each row of the tube bundles and compared with predictions from analytical models. In the single tube measurements, the enhanced finned tubes showed distinctly higher HTCs than the standard finned tubes. Different condensation flow modes have been observed during the tube bundle experiments where the additional structures on the fin flank of the enhanced finned tubes promote sheet mode condensation. It has been demonstrated that the standard finned tubes show a lower decrease in the condensation HTC with increasing tube row number in the bundle than the enhanced finned tubes. Among the standard finned tubes, the one with 48 FPI and larger fin height exhibits the highest HTCs for single tube and tube bundle experiments. The increase in the fin height seems to delay the formation of sheet mode condensation and thus to increase the condensation HTC. Among the enhanced finned tubes, the tube with 39 FPI yields the highest HTCs for both single tube and tube bundle measurements. Low fin density and large fin height obviously tend to keep the insulating effect of retained condensate in the fin channels low. [ABSTRACT FROM AUTHOR]

This work experimentally studied the single-phase flow and heat transfer characteristics of a type of multiport microchannel flat tube (MMFT) with a sawtooth fin structure. This MMFT consisted of numerous parallel rectangular microchannels and is widely used in industry as the heat transfer unit of a heat exchanger. Three samples with different dimensions and varied fin sizes were used as test sections to perform the experiment with water as a working fluid. The Reynolds number was varied from 110 to 6100 to cover the laminar, transition, and early fully developed turbulent regions. Moreover, a smooth MMFT of the same dimension as one of the three samples with a fin structure was tested as the control experiment. The experimental results show that the fin structure can enhance the heat transfer at the expense of increasing the pressure drop and earlier induction of the laminar-turbulent transition. The degree of heat transfer enhancement and the pressure drop increase both depend on the raised degree of the fin structure. Finally, the performance evaluation criterion (PEC) was calculated to comprehensively assess the performance of the MMFT with fins. The values of the PEC indicate that the MMFT with fins improves the heat transfer performance. [ABSTRACT FROM AUTHOR]

Abstract: Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED''s lifetime at a given photometric flux. Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable junction temperature for a given lifetime. The goal of this study is to improve the thermal characteristics of high-power LED package by using phase change heat sink. The heat-release characteristics of high-power LED package are analyzed and a novel phase change heat sink with 3D integral-fin boiling structures for high-power LED is developed. Two different fin structures were obtained in grooves formed with chopping-ploughing-extrusion compound forming technology and observed by scanning electron microscope (SEM). [Copyright &y& Elsevier]

In this paper, after a short review of the heat exchangers (HEX) types and applications with different technologies was presented, a lot of parameters which mainly affect the thermal-hydraulic performance of heat exchangers have been offered to characterize the optimal design of HEX. It can be seen that the presence of a fin in a smooth channel or tube provides the best overall performance of HEX. Furthermore, the use of a vortex generator, which is considered prominent passive method, significantly increases the rate of heat transfer and reduces the pressure drop. Finally, the current review provides some recommendations for future studies to enhance the performance of HEX. • A brief overview of heat exchangers design and structure parameters is investigated. • Using fins is more acceptable than other techniques. [ABSTRACT FROM AUTHOR]

With the incremental power of construction machinery diesel engines, the power performance of diesel engines and the pollutant emissions from the exhaust gas have imposed increasingly stringent requirements on the intake cooling system of diesel engines. This paper compared the j/f evaluation factors for fin unit bodies of water-cooled intercooler (including straight fins and rectangular misaligned fins) by means of CFD simulation, and found that the rectangular misaligned fins had an 8% advantage in comprehensive performance. With the rectangular staggered fin intercooler, it was found that under the same conditions, the cooling efficiency of the dual-pass water-cooled intercooler is higher than that of the single-pass water-cooled intercooler, and the uniformity factor of the temperature difference field of the dual-pass water-cooled intercooler is 1.5% higher than that of the latter. The accuracy of the overall simulation of the intercooler is verified by the field test. The dual-pass and single-pass water-cooled intercooler both can maintain heat balance under working conditions, and its average air inlet temperature is 10 °C lower than that of the original air-cooled intercooler, which provides support for further reducing the engine air inlet temperature. The results provide a theoretical basis for the performance improvement of water-cooled intercoolers. [ABSTRACT FROM AUTHOR]

Fin electromagnetic wave absorbers are proposed in which the sintered ferrite plates are placed in the direction perpendicular to the electric field of the incident electromagnetic field. By numerical calculations, it is shown that this structure has a broadband reflection suppressing characteristic. The characteristics of the absorbers in terms of the structural parameters of the absorber and ferrite permeability are shown, and it is found that the optimum structure of the absorber for a broadband operation depends on the permeability of the ferrite. Further, by means of the model experiment, the broadband characteristics of the proposed absorber are demonstrated. [ABSTRACT FROM AUTHOR]

Realizing conversion between fluid power and mechanical energy, the closed circuit axial piston transmission (CCAPT) plays a vital and indispensable role in miscellaneous industries. The frictional loss and leakage loss inside the system give rise to the inevitable temperature rise. In order to prolong the life of the device, a cooling structure on the outside of the CCAPT is designed for promoting heat dissipation. Based on the relevant heat transfer law and the temperature distribution of internal machinery elements, a spiral fin structure is designed at the shell side. With the help of numerical simulation, the effects of fin height, fin pitch, and fin thickness on the thermal performance are studied. The flow field and temperature field on the outside of the fin structure are obtained as a guidance for enhancing heat dissipation effect. Results indicate that the area of rotating elements tend to accumulate heat, where more attention should be paid for a better cooling effect. In addition to this, a moderate increase of fin height, fin pitch and fin thickness has a positive effect on heat transfer enhancement. The peak value of Nusselt number is obtained with a fin height of 7.5 mm, which is about 2.09 times that of the condition without the fin structure. An increase in fin pitch improves both heat transfer performance and comprehensive performance at the same. When fin pitch is 30 mm, Nusselt numberincreases 104% over the original condition. [ABSTRACT FROM AUTHOR]