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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]

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]

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]

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• 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]

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]

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]

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]