Serrated Fins Research Articles

Using fins to enhance heat transfer of cylindrical lithium-ion batteries immersed in electrical insulating oil

This work focused on designing the heat dissipation fins for cylindrical lithium-ion batteries to quickly transfer the heat generated inside the battery to the surrounding immersed insulating oil. The measured instantaneous heat generation rate of a single battery at the discharge rates of 1.0C and 1.5C was adopted as the internal heat source to simulate the surface temperature field of two series and two parallel (2S2P) battery modules immersed in insulating oil in three-dimensional space, respectively. The numerical simulation method has been validated by experimental results, indicating that the scheme of using this internal heat source is feasible. Then, this method was continued to be used to simulate the temperature rise characteristics during higher rate 2.5C discharge processes when the heat transfer was enhanced by circular or serrated fins. The cooling effects of three heat exchange enhancement methods (no fins, circular fins, and serrated fins) were compared under the operating conditions of 25 °C ambient temperature, and 1 g·s−1 rated insulation oil circulation mass flow rate. The maximum temperatures of the batteries in the module were 40.3 °C, 38.4 °C, and 37.5 °C, respectively. The maximum temperature differences between the batteries in the module were 1.63 °C, 1.59 °C, and 1.51 °C, respectively. Therefore, the serrated fins had the best thermal management effect. The orthogonal method was used to analyze the influence of the external structure and quantity of fins, as well as the insulation oil circulation mass flow rate, on heat transfer efficiency, and it was determined that the most significant factor is the mass flow rate of insulation oil. The final optimal parameters suitable for the 2S2P battery module were obtained, which were 16 serrated fins for each battery, with a fin height of 6 mm, a fin width of 3 mm, and a mass flow rate of 7 g·s−1.

Enhancing plate-fin heat exchanger hydraulic thermal performance through air-side fin optimization based on pseudo-3D topology optimization

With the expansion of the New Energy Vehicles (NEVs) market, the demand for efficient thermal management systems is increasingly pressing. Topology optimization (TO) methodology is an important way to improve the performance of heat exchangers (HE) in many use scenarios. This study focuses on enhancing the design of air-side fins within plate-fin HE, which are vital components in NEVs thermal management systems. By employing the TO methodology, our research aims to enhance the hydraulic thermal performance of these HE. A pseudo-three-dimensional (3D) flow heat transfer model is used to improve the hydraulic thermal performance of HE by variable density method. An optimization function considering thermal resistance and dissipated power is proposed in this study. The investigation rigorously assesses the effects of different controlling parameters on the results of TO. Following the optimization, a 3D model of the optimized fin configuration is elaborated to analyze the localized fluid dynamics and thermal characteristics. Furthermore, the study evaluates the hydraulic thermal performance of the TO fins under diverse inlet velocities, revealing significant alterations in vortex patterns with velocity increments, which substantially impact heat transfer in the cooling channel. Under varying inlet velocities, the TO fin design exhibits the optimal hydraulic thermal characteristics, demonstrating an enhancement of 9.53% to 22.82% in the comprehensive performance factor (JF) compared to the conventional serrated fin. This research contributes innovative strategies for radiator optimization in thermal management systems of NEVs, fostering advancements in heat exchange efficiency and radiator lightweight.

Optimization investigation for heat transfer enhancement of fins for plate-fin heat exchangers in cryogenic helium systems

In order to further improve heat transfer performance and high compactness of plate-fin heat exchangers (PFHEs) in cryogenic helium systems, a new type of perforated-serrated fins is proposed by combining traditional serrated and perforated fins. In this paper, the flow and heat transfer characteristics of helium in perforated-serrated fins and serrated fins channels at low-temperature are investigated using numerical simulations. The numerical model invokes the properties of low-temperature helium by NIST-Real-Gas-Model. Meanwhile, Colburn factor j, friction factor f and JF factor are qualitatively evaluated for pressure drop, heat transfer performance and thermo-hydraulic performance, respectively. The results show that new perforated-serrated fins have better heat transfer performance. The j factor of the new fins increases by 32.58% to 15.63% compared with serrated fins. The flow performance of perforated-serrated fins is slightly worse than that of serrated fins, but the overall thermo-hydraulic performance is better, especially at low Reynolds number. Compared with serrated fins, the JF factor of perforated-serrated fins is significantly higher and increase by 25.95% to 10.86%. The optimizing method of fins structure can be used in the actual design of PFHEs in cryogenic helium systems.

A Study of the Influence of Fin Parameters on Porous-Medium Approximation

The porous-medium approximation (PM) approach is extensively employed in large-quantity grid simulations of heat exchangers, providing a time-saving approach in engineering applications. To further investigate the influence of different geometries on the implementation of the PM approach, we reviewed existing experimental conditions and performed numerical simulations on both straight fins and serrated fins. Equivalent flow and heat-transfer factors were obtained from the actual model, and computational errors in flow and heat transfer were compared between the actual model and its PM model counterpart. This exploration involved parameters such as aspect ratio (a*), specific surface area (Asf), and porosity (γ) to evaluate the influence of various geometric structures on the PM approach. Whether in laminar or turbulent-flow regimes, when the aspect ratio a* of straight fins is 0.98, the flow error (δf) utilizing the PM approach exceeds 45%, while the error remains within 5% when a* is 0.05. Similarly, for serrated fins, the flow error peaks (δf > 25%) at higher aspect ratios (a* = 0.61) with the PM method and reaches a minimum (δf < 5%) at lower aspect ratios (a* = 0.19). Under the same Reynolds numbers (Re), employing the PM approach results in an increased heat-transfer error (δh)with rising porosity (γ) and decreasing specific surface area (Asf), both of which remained under 10% within the range of this study. At lower aspect ratios (a*), the fin structure becomes more compact, resulting in a larger specific surface area (Asf) and smaller porosity (γ). This promotes more uniform flow and heat transfer within the model, which is closer to the characteristics of PM. In summary, for straight fins at 0 < a* < 0.17 in the laminar regime (200 < Re < 1000) and in the turbulent regime (1200 < Re < 5000) and for serrated fins at 0 < a* < 0.28 in the laminar regime (400 < Re < 1000) or 0 < a* < 0.32, in the turbulent regime (2000 < Re < 5000), the flow and heat-transfer errors are less than 15%.

Numerical investigation on the performance of a new type of perforated-serrated fins for plate-fin heat exchangers in cryogenic helium systems

Plate-fin heat exchangers (PFHEs) with serrated fins are commonly employed in cryogenic helium systems. To further improve the heat transfer performance and compactness of PFHEs, traditional serrated fins structure is optimized and a new type of perforated-serrated fins is proposed with each serrated fin perforated. Numerical simulations considering the influence of cryogenic conditions, using well-validated 3D models, are carried out. The results show that the heat transfer performance of optimized fins is improved. Compared with traditional serrated fins, Colburn j factor of perforated-serrated fins increases by 30.61–12.61 % at 20 K and by 16.71–2.9 % at 77 K. Although the flow performance of perforated-serrated fins is somewhat inferior, overall thermo-hydraulic performance is superior, particularly at low Reynolds numbers. The JF factor of perforated-serrated fins increases by 23.75–9.34 % at 20 K and by 11.04–3.3 % at 77 K. In addition, the effects of perforated position and fin porosity on thermo-hydraulic characteristics of perforated-serrated fins are obtained. For the design below 80 K PFHEs used in cryogenic helium systems, replacing traditional serrated fins with perforated-serrated fins may be worth considering to further improve overall thermo-hydraulic performance.

Experimental investigating the thermal and hydraulic performance of heat exchangers with helix wire finned tube

In this study, the helix wire finned tube is introduced as a novel design to increase the performance, reduce weight, and manufacturing price of the heat exchangers. The helix wire fin can make turbulence in the fin-side flow, creates a larger contact surface, more flow trapping and increment in the residence time for enhancement of the heat transfer. The effect of Reynolds number inside and outside of the finned tube and inter-tube distance on the thermo-hydraulic performance of the heat exchanger has been investigated experimentally. The results show that increasing the Reynolds outside the finned tube causes an 80% enhancement in the performance evaluation criterion of the heat exchanger. Also, helix wire finned tubes provide a maximum of 65% and 57% better thermal performance compared to spiral and serrated fins. Increasing the Reynolds number of the outside and inside tube flow causes a 40% and 50% enhancement in the Nusselt number of the fin-side flow, respectively. Moreover, increasing the longitudinal distance between the tube rows reduces the Nusselt number and friction factor of the fin-side flow by 20% and 45%, respectively. Finally, an experimental correlation is derived to calculate the Nusselt number of the air-side flow.

Numerical simulation on flow and heat transfer performances of serrated and wavy fins in plate-fin heat exchanger for hydrogen liquefaction

In order to test the applicability of the existing correlations of the flow and heat transfer performances (FHTPs) of the high-efficiency fins to the plate-fin heat exchanger (PFHE) for hydrogen liquefaction, a numerical model is established to investigate the FHTPs of hydrogen in the serrated fin (SF) and wavy fin (WF). The results show that the existing correlations can be applied to the conditions of the low-pressure hydrogen in 30–300 K and the high-pressure hydrogen in 40–300 K. However, the FHTPs of the high-pressure hydrogen in 30–40 K are obviously different from the existing correlations and need the new correlations for calculation. The high-pressure and low-temperature condition leads the low velocity in the fin channel, resulting in that the serrated locations of the SF and the wave crest and wave trough of the WF are the keys to affect the FHTPs. On the basis, a series of data points reflecting the relationships between the FHTPs and the operational and structural parameters are extracted from the response surfaces to establish the new correlations. For the SF, the new correlations of the Colburn heat transfer factor (j) and the Fanning friction factor (f) have a good consistency with the original data, with the fitting goodness of 96.4% and 92.4% and the average relative deviations of 8.3% and 9.7% respectively. And the fitting goodness and average relative deviations of the new correlations of the WF are 96.5% and 99.0%, and 7.9% and 9.3% respectively. The new correlations of the SF and WF can be used to guide the design of the PFHE in 30–40 K for hydrogen liquefaction.

Heat transfer and flow resistance performance of nonuniform distributed serrated fins

This article numerically investigates the behavior of nonuniform distributed serrated fins including equaled, shortened, lengthened, short on both sides, and long on both sides. In outputs, not only the temperature field and velocity contour but also the synergy field were examined. The results show significant advantages of nonuniform fins, having certain characteristics, in improving the overall heat transfer performance. At the near entrance of nonuniform fin type, heat transfer can be improved by increasing fin length gradually, while it becomes worsened by decreasing fin length. The length of the first fin in the near inlet region has a great influence on the distribution of the temperature field. For the best array compared with the uniform case, the Colburn j factor increased by 9.1 − 16.8%. Either uniform or nonuniform fin type deteriorates the flow resistance while heat transfer capability is enhanced. From the perspective of synergy between temperature gradient and velocity, the local field synergy angle at the near inlet region, and the windward side of the fin has a decisive effect on the heat transfer performance.

Nonlinear thermal analysis of serrated fins by using homotopy perturbation method

Nonlinear thermal analysis of serrated fins by using homotopy perturbation method

Numerical and experimental performance investigation of a heat exchanger designed using topologically optimized fins

Topology optimization for thermal-fluid problems has been successfully used to improve performance of small structures used for heat transfer. Optimization of full heat exchangers, due to analysis method limitations and computational costs, has not been able to produce manufacturable designs complex enough to satisfy heat exchanger specifications. The goal of this study is determining if a practical heat exchanger design can be obtained by the use of topology optimization. By considering a plate-fin heat exchanger, topology optimization is used to obtain a locally optimized fin pattern which is extended to form a heat exchanger core. A modification of the Number of transfer units method is presented to deal with the unique topology obtained by optimization and evaluate the performance of the exchanger. The performance, when compared to traditional serrated fin designs, show that optimization improvements extend beyond the optimized region onto the entire exchanger. The results show that the optimized design is an improvement outside optimization flow parameters. However, the limitations in 3D printer technology result in slight deviation of experiment results compared to the analysis, and prevent the manufacturing of designs with comparable total performance values to heat exchangers manufactured through traditional methods. • Design procedure obtains a heat exchanger core by localized topology optimization. • NTU method is modified to evaluate results of topology optimization. • Modified NTU, CFD and experimental evaluations are in good agreement with each other. • Performance improvements are maintained outside optimization flow parameters.

A numerical study for solid and serrated annular finned tube bundles

Annular finned tube bundles are commonly used for heat recovery systems. Nowadays, heat recovery systems are important in the energy economy. Cross-flow heat exchangers, one of the heat exchanger types are suitable for waste heat recovery systems. Annular fins are utilized in cross-flow heat exchangers for a long time. In this study, two types of annular fin geometry, namely solid and serrated fins, were studied numerically in the cross-flow heat exchangers. All numerical analyses are performed in ANSYA-FLUENT program and the fin geometries are designed in 3-D geometry. Numerical results obtained for two different geometry fins are validated separately with the literature. It is seen that analysis results are found to be compatible with the literature. In numerical analyses, five different Reynolds Numbers and six different geometric parameters are studied. Effects of these parameters are investigated to determine the flow and thermal performance. According to analysis results, the thermal performance of the serrated annular fin geometry is about 8.2% higher than the solid fin geometry, while the flow performance decreases by 7.5%.

Numerical Analysis of the Effect of Serrated Fin to the Heat Transfer in the Condenser

Condenser is one of the most important components in the power generation industry, which serves to condense the output steam from low-pressure turbine for boiler feed water. Several ways can be used to improve the performance of the condenser, one way is to add a serrated fin on the outer tube to lower the temperature of the outlet. A serrated fin that is used has 0° and 30 segments per period, which is installed on the tube with the diameter of the outer of 0.03175 m. This research was carried out by using the numerical method of CFD 2D to compare the performance of the heat transfer on the tube without and with a serrated fin on the variation speed of 7 m/s and 9 m/s. By inputting the parameters of the inlet of 350.15 °K, the resulting value of the outlet serrated fin tube temperature which is lower than the annular tube (tube without the serrated fin). On the simulation of the serrated fin tube with an inlet velocity of 7 m/s resulting outlet temperature of 343.2 °K, lower than in the simulation on the annular tube which produces the outlet temperature of 344.53 °K.

A comprehensive design, optimization and development methodology of a wasted heat recovery boiler using serrated fins and extensive surface in a bulky CCPP

This paper describes the requirements and the difficulty encountered in preparing the data for the consumption calculations of a waste heat recovery boiler (WHRB). The study is performed based on continuous monitoring of the operating data by considering the extensive thermal surfaces and a large number of small-serrated fins. The recovery boiler efficiency improved using optimization of temperature profile by better surface arrangement. Then, the suggested designed waste heat recovery boiler is accessible and conducted in a real combined cycle power plant (CCPP). The CCPP optimization is performed based on the new WHRB with and without optimal saturation temperature, and the recovery boiler optimal temperature is obtained based on the objective function. The founded values of the CCPP at different temperatures are verified and compared to the regular operation. The important findings include four categories. First, the gas temperature of the recovery boiler will decrease slightly while the efficiency will increase by increasing the load changes. Second, the dependency of the decision parameters of the CCPP to the ambient temperature is effectively high, and any changes in the efficiency depending on the ambient temperature. Third, the exergy efficiency increment without affecting the total exergy can be performed by using the low-pressure saturation temperature as a decision-making parameter. Forth, 17.9% improvement in the entire cycle efficiency and a 2.14% increase in WHRB exergy are observed after incrementing the cost by 14.48%.

Multi-parameter optimization of serrated fins in plate-fin heat exchanger based on fluid-structure interaction

The comprehensive performance of serrated fins in plate-fin heat exchanger (PFHE) under cryogenic condition is analyzed based on fluid-structure interaction (FSI). On the foundation of response surface methodology (RSM) and sobol sensitivity analysis, the effects and interaction effects of fin height, fin space, fin thickness and fin interrupted length on flow resistance, heat transfer and stress are analyzed quantitatively. The contour results show that, compared with the pressure stress, the thermal stress is very low and the high stress mainly locates in the regions of keen-edged geometric structure, and the highest stress is in the regions connecting two rows of fins. The sensitivity analysis results show that the effect of fin interrupted length on j factor is the most significant and the interaction effect of fin space and fin interrupted length is the most obvious. The effect of fin thickness on f factor or the maximum stress is the most significant and the interaction effect of fin thickness and fin space is the most obvious. By implementing Multi-Objective Genetic Algorithm (MOGA), the serrated fin structure is optimized comprehensively and a set of Pareto-optimal points are obtained. Compared with the original structure, the JF factor of optimized structure 1, 2 and 3 increases by 8.8%, 4.4% and 9.6%, and the maximum stress decreases by 29.6%, 42.3% and 21.1%, respectively. The MOGA based on RSM offers theoretical guidance for design optimization of PFHE.

Research on gas side performance of staggered fin-tube bundles with different serrated fin geometries

This investigation conducted experiments on the gas-side performance of serrated spiral fin-and-tube heat exchanger with staggered layouts. The number of tube rows is 10 under the Reynolds numbers of 6000 to 12,000. The influences of varied water vapor content and fin geometry were explored. The results showed that the increase of water vapor content leads to an increase in the Nusselt number of the serrated fin and twisted serrated fin, and the effect on serrated fin was more significant. Besides, the decrease in the Euler number of both fin tube was observed with the water vapor content increasing. The twisting in the top of segment fin corresponded to a significant increase in the Nusselt and Euler numbers. Finally, the comparison of overall performance between the two types of fin tube was performed, and the results showed that the twisted serrated fin has better performance in the current experimental range.

Thermal Management of Flat Photovolatic Panels using Serrated Fins to Increase Electrical Output

The electrical power output of photovoltaic (PV) cell depends on its operating temperature during its absorption of solar radiation and conversion of solar energy to electrical energy. The increase in PV panel temperature due to overheating negates its electrical yield and efficiency. In addition, overheating causes hot spots, failure of adhesive seals and delamination. An effective way to combat this problem is to reduce the operating temperature of PV panel by cooling. In the present work, a novel thermal management technique for improved cooling of flat PV panel is proposed with the use of serrated fins rather than straight fins. For this reason, the thermal and electrical performance of the flat PV panel with cooling system consisting of duct, brushless DC cooling fan, a plate fin and serrated fins of varying angles (30o, 45o and 60o) made up of aluminium were investigated experimentally. Experiments were conducted at constant wind velocity (1 m/s) with the developed technique in the location of Tiruchirappalli (78.6 E to 10.8 N), Tamil Nadu, India with flat 10 W PV panel. By using serrated fins of varying angles of 30o, 45o, 60o and plate fin (90°), the temperature of the PV panel decreased by a maximum of 4oC, 7oC, 6oC and 3oC respectively. Similarly the PV power increased in the range of 15.38%, 61.53%, 41.53% and 7.69% for 30o, 45o, 60o and plate fin (90°) respectively. It is concluded that 45o angled serrated fin is more efficient in providing the cooling effect than the other angles of serrated fins considered.

Effect of fin types and Prandtl number on performance of plate-fin heat exchanger: Experimental and numerical assessment

An experimental investigation is performed using liquid R113 to study the thermohydraulic characteristics of plate-fin heat exchanger with plain, serrated and perforated fins. Meanwhile, three performance evaluation criteria j/f, j/f1/2 and j/f1/3 are used to qualitative compare their comprehensive performance. Further, to study the effects of heating condition and Prandtl number on heat transfer, a numerical model of serrated fins is carried out. The fin channels with a uniform heat flux at bottom end or at both bottom and upper ends are studied as two types of heating conditions, namely, single-fold and two-fold modes. Besides, using air (Pr = 0.744), R113 (Pr = 9.02) and ethylene glycol (Pr = 51.65) aqueous solution as working media, the Prandtl number effect is discussed. The results reveal that the comprehensive performance of serrated fins is the best. Colburn factor j of single-fold mode is lower than that of two-fold mode. The Colburn factor j decreases as the Prandtl number increases in laminar flow and it is independent of Prandtl number in turbulent flow. A modified Colburn factor j based on the Manglik & Bergles correlation is proposed as functions of (Pr/Prair)−0.04827 in laminar flow. The conclusions provide the guidance on the design of plate fin heat exchanger.

Numerical investigation of serrated fins on natural convection from concentric and eccentric annuli with different cross sections

In this paper, the effect of internal serrated fins and eccentricity on natural convection heat transfer between annular spaces with the equivalent circular, square, and triangular cross sections has been studied numerically using control volume method. The annuli’s inner and outer walls were maintained at different uniform temperatures of 373 and 327 K, respectively, and Rayleigh number ranges were 105 ≤ Ra ≤ 108. According to the results, although heat transfer coefficient was reduced between the space of fins, fins increased the total heat transfer of both inner and outer walls of annuli. The best heat transfer rate belongs to reverse triangular annulus when fins were mounted on the inner wall. As an example, heat transfer of inner wall of reverse triangular annulus was, respectively, increased about 31 and 10% at Ra = 105 and 108, when serrated fins were mounted on the inner wall. In addition, fin efficiency of inner and outer walls was decreased with the increase in Rayleigh number. Nevertheless, thermal efficiency of reverse triangular annulus was uppermost at all Rayleigh numbers compared to other ones. In addition, eccentric annuli showed better heat transfer rate than concentric ones, in which cases 3.5 and 6.7% thermal improvements have been obtained for 0.6 and 1 mm downward movement of the inner wall at Ra = 108, respectively.

Numerical analysis on interactions between fluid flow and structure deformation in plate-fin heat exchanger by Galerkin method

The fluid-structure interaction performance of plate-fin heat exchanger (PFHE) with serrated fins in large scale air-separation equipment was investigated in this paper. The stress and deformation of fins were analyzed, besides, the interaction equations were deduced by Galerkin method. The governing equations of fluid flow and heat transfer in PFHE were deduced by finite volume method (FVM). The distribution of strain and stress were calculated in large scale air separation equipment and the coupling situation of serrated fins under laminar situation was analyzed. The results indicated that the interactions between fins and fluid flow in the exchanger have significant impacts on heat transfer enhancement, meanwhile, the strain and stress of fins includes dynamic pressure of the sealing head and flow impact with the increase of flow velocity. The impacts are especially significant at the conjunction of two fins because of the non-alignment fins. It can be concluded that the soldering process and channel width led to structure deformation of fins in the exchanger, and degraded heat transfer efficiency.

Experimental study of boiling heat transfer and flow characteristics in fin channels with variable cross section

The object of this work is to investigate the boiling heat transfer performance of transverse serrated fin (TSF) channel and triangle perforated fin (TPF) channel in compact plate-fin heat exchanger. A series of boiling heat transfer performance tests are carried out for volume flow rate range of 0.03–0.3m3/h and heat flux of 10–20kW/m2. The local and average heat transfer coefficient of TSF channel and TPF channel are examined. It indicates that both local and average boiling heat transfer coefficient of TSF channel was higher than that of TPF channel. The boiling heat transfer occurs in TSF channel at lower wall superheat. The growth rate of wall temperature significant declines significantly when heat flux is up to ONB point, which means the boiling heat transfer has happened. The rising rate of average boiling heat transfer coefficient have is smaller than that of the local boiling heat transfer coefficient hout.