Wavy Plate-fin Research Articles

Structural optimization design of sinusoidal wavy plate fin heat sink with crosscut by Bayesian optimization

• Develop an intelligent optimization scheme based on Bayesian Optimization algorithm. • Optimum design is performed by integrating the structure modeling, meshing, and evaluation. • Bayesian Optimization algorithm demonstrates a great advantage over evolutionary algorithms in efficiency. • The comprehensive thermal performance factor of the heat sink with the optimal structure increases by 17.6%. • The enhancement is explained by the reduction of the synergy angle between the velocity and the pressure gradient. The optimal structure of a sinusoidal wavy plate fin heat sink with crosscut (SWHS-WC) is determined by an efficient intelligent optimization method based on Bayesian Optimization (BO) algorithm. The comprehensive thermal performance factor (TPF) is the objective function, which is associated with the heat transfer and the pressure drop. The parametric modeling, meshing, and numerical calculation are integrated to optimize three structural parameters, including the fin amplitude, period, and phase shift angle of the heat sink, in an iterative and automated way. The result shows that the TPF of the SWHS-WC with the optimized structure is increased by 17.6%, due to the significant reduction in the pressure drop penalty, and the corresponding synergy angle between the pressure gradient and the velocity decreases by about 6.2°. Compared to the evolutionary algorithms, the BO algorithm demonstrates a great advantage in calculation efficiency, which can be used to find the global optimum design at a much smaller computational cost.

Structural Optimization Design of Sinusoidal Wavy Plate Fin Heat Sink with Crosscut by Bayesian Optimization

Structural Optimization Design of Sinusoidal Wavy Plate Fin Heat Sink with Crosscut by Bayesian Optimization

A Three-Dimensional Numerical and Multi-Objective Optimal Design of Wavy Plate-Fins Heat Exchangers

This paper presents a method for optimizing wavy plate-fin heat exchangers accurately and efficiently. It combines CFD simulation, Radical Basis Functions (RBF) with multi-objective optimization to improve the performance. The optimization of the Colburn factor j and the friction coefficient f is regarded as a multi-objective optimization problem, due to the existence of two contradictory goals. The approximation model was obtained by Radical Basis Functions, and the shape of the heat exchanger was optimized by multi-objective genetic algorithm (MOGA). The optimization results showed that j increased by 17.62% and f decreased by 20.76%, indicating that the heat exchange efficiency was significantly enhanced and the fluid structure resistance reduced. Then, from the aspects of field synergy and tubulence energy, the performance advantage of the optimized structure was further confirmed.

Characterization and Scaling of Forced Convective Swirl in Sinusoidal Wavy-Plate-Fin Cores of Compact Heat Exchangers

Abstract The characterization and scaling of the thermal-hydraulic performance in wavy plate-fin compact heat exchanger cores, based on the understanding of the physical phenomena and heat transfer enhancement mechanism is delineated. Experimental data are presented for forced convection in air (Pr = 0.71) with flow rates in the range 50 ≤ Re ≤ 4000. A variety of wavy-fin cores that span viable applications, with geometrical attributes described by the cross section aspect ratio α (ratio of fin spacing to height), fin corrugation aspect ratio γ (ratio of 2× corrugation amplitude to wave pitch), and fin spacing ratio ζ (ratio of fin spacing to wave pitch), are considered. To characterize and correlate the vortex-flow mixing in interfin spaces, a Swirl number Sw is introduced from the balance of viscous, inertial and centrifugal forces. It is shown that the laminar, transitional and turbulent flow regimes can be explicitly identified by this Swirl number. Based on the experimental results and extended analysis, new correlations for Fanning friction factor f and Colburn factor j are developed with Sw, α, γ, and ζ as scaling parameters. Requisite expressions are devised by a superposition of both enhancement components due to the corrugated surface area enlargement and induced swirl flow field, and they are combined to cover the laminar, transitional and turbulent regimes by the method of asymptotic matching. The resulting generalized correlations are further shown to predict all available experimental data for f and j factors to within ±20% and ±15%, respectively.

Heat transfer and flow characteristics of sinusoidal wavy plate fin heat sink with and without crosscut flow control

This article presents new experimental data on the influence of phase shift, air velocity, heat sink base surface temperature on heat transfer coefficient, and pressure drop of airflow through sinusoidal wavy plate fin heat sinks (SW-PFHS) and crosscut sinusoidal wavy plate fin heat sinks (CCSW-PFHS). Sinusoidal wavy plate fins with a wave length of 18.68 mm, amplitude of 2.0 mm, and phase shift of 0°, 90°, and 180° are used. For CCSW-PFHS, the sinusoidal wavy plate fin is cut transversely at crests and troughs with a 2 mm length. The test runs are performed at an air velocity ranging between 1 and 5 m/s and a heat sink base surface temperature of 70 °C, 90 °C, and 110 °C. The results show that the higher phase shift and air velocity lead to the enhancement of the heat transfer coefficient and pressure drop. Conversely, the heat sink base surface temperature has a slight effect on the heat transfer coefficient and pressure drop. The heat transfer coefficient of SW-PFHS is enhanced when increasing the phase shift compared with a phase shift of 0°. Under the same phase shift, the Nusselt number of CCSW-PFHS is higher than that of SW-PFHS by about 5.9–19.1%. The CCSW-PFHS with a phase shift of 180° yields the highest TPF.

On the Heat Transfer Enhancement of Plate Fin Heat Exchanger

The plate fin heat exchanger is a compact heat exchanger applied in many industries because of its high thermal performance. To enhance the heat transfer of plate fin heat exchanger further, three new kinds of wavy plate fins, namely perforated wavy fin, staggered wavy fin and discontinuous wavy fin, are proposed and investigated by computational fluid dynamics (CFD) simulations. The effects of key design parameters, including that of waviness aspect ratios, perforation diameters, staggered ratios and breaking distance are investigated, respectively, with Reynolds number changes from 500 to 4500. It is found that due to the swirl flow and efficient mixing of the fluid, the proposed heat transfer enhancement techniques all have advantages over the traditional wavy fin. At the same time, serration is beneficial to reduce the friction factor, and the breaking technique can reduce heat transfer area. Through the performance evaluation criteria, the staggered wavy fin has an advantage over the small waviness aspect ratio; with increasing waviness aspect ratio, this predominance is gradually surpassed by the perforated wavy fin, and the advantage of the discontinuous fin is the smallest and almost invariable. A maximum performance evaluation criteria (PEC) as high as 1.24 can be obtained for the perforated wavy fin at the waviness aspect ratio γ = 0.45.

Analytic solutions of the friction factor and the Nusselt number for the low-Reynolds number flow between two wavy plate fins

Analytic solutions of the Fanning friction factor and the Nusselt number for the low-Reynolds number flow between two wavy plate fins are obtained. The geometric features of the wavy plate fins are described by a sinusoidal variation with three parameters: fin spacing 2H, amplitude of waviness a, and period length L. The fluid flow between two wavy plate fins is assumed to be a 2-D flow. The coordinate transformation in conjunction with the perturbation method is used to solve the governing equations. The results from the analytic solutions are shown to be in close agreement with those obtained from numerical simulations using a commercial code, FLUENT. The applicable range of the present solutions is as follows: a/H⩽0.5, H/L⩽0.33, Pe⩽100. The value of fRe monotonically increases as the dimensionless waviness (a/L) increases and the increment is proportional to the square of a/L. On the other hand, the Nusselt number increases to the peak value and then decreases as H/L increases. Based on the analytic solution, a correlation of (H/L)max for which the Nusselt number attains a maximum is presented.

Effects of delta winglets on performance of wavy plate-fin in PFHEs

In the current experimental study, the use of delta winglets to enhance heat transfer in wavy plate-fins (WPFs) is proposed in presence of Al2O3/water nanofluid. Impacts of the most effective parameters, including waviness aspect ratio (γ = 0.33, 0.42, and 0.51), winglets height (h = 2, 4, and 6 mm), nanoparticles mass fraction (0–0.4%), and Reynolds number (4500–11,500), are examined. In order to prepare the nanofluids, a two-step method is adopted, alpha aluminum oxide nanoparticles as additive and deionized water as base fluid. The results depict that the use of proposed geometries leads to a considerable heat transfer enhancement in plate-fin heat exchangers, especially at the highest values of waviness aspect ratio and winglets height. However, optimum thermal–hydraulic performance is detected for a specific geometry of WPF with γ = 0.42 and h = 6 mm. To evaluate the performance of WPFs with prepared nanofluids, variations of heat transfer coefficient and pressure drop are reported regarding to the based fluid. The maximum heat transfer enhancement of 11.3% is observed for 0.4% nanofluid flow over the WPF with γ = 0.51 and h = 6 mm.

Thermal–hydraulic performance of wavy plate-fin heat exchanger using passive techniques: Perforations, winglets, and nanofluids

Wavy plate-fins (WPFs) are commonly used in plate-fin heat exchangers in order to improve the performance and reduce the size. The purpose of this paper is to investigate the influences of using three passive heat transfer enhancement (HTE) techniques, namely perforations, winglets, and nanofluids, on heat transfer and flow specifications of the WPFs. The waviness aspect ratios are 0.33, 0.42, and 51, the diameter of the perforation is 5mm, the width/height of the winglets is 5mm, and Reynolds number changes from 3900 to 11,400. It is detected that due to the efficient mixing of the working fluid by the winglets, the heat transfer performance of the winged WPFs is always significantly superior to that of the other WPFs; at the same time, the friction factor of the winged WPFs is very high. Hence, an overall performance factor is defined to compare different HTE techniques at the same operating conditions. The maximum performance factor of 1.26 is obtained for the winged WPF compared to the typical WPF at the lowest Reynolds number and the highest waviness aspect ratio. Therefore, the winged WPF can be used as a high-quality interrupted surface in the fabrication of plate-fin heat exchangers.

A review on the thermal hydraulic characteristics of the air-cooled heat exchangers in forced convection

In this paper, a review is presented on the experimental investigations and the numerical simulations performed to analyze the thermal-hydraulic performance of the air-cooled heat exchangers. The air-cooled heat exchangers mostly consist of the finned-tube bundles. The primary role of the extended surfaces (fins) is to provide more heat transfer area to enhance the rate of heat transfer on the air side. The secondary role of the fins is to generate vortices, which help in enhancing the mixing and the heat transfer coefficient. In this study, the annular and plate fins are considered, the annular fins are further divided into four categories: (1) plane annular fins, (2) serrated fins, (3) crimped spiral fins, (4) perforated fins, and similarly for the plate fins, the fin types are: (1) plain plate fins, (2) wavy plate fins, (3) plate fins with DWP, and (4) slit and strip fins. In Section 4, the performance of the various types of fins is presented with respect to the parameters: (1) Reynolds number, (2) fin pitch, (3) fin height, (4) fin thickness, (5) tube diameter, (6) tube pitch, (7) tube type, (8) number of tube rows, and (9) effect of dehumidifying conditions. In Section 5, the conclusions and the recommendations for the future work have been given.

Comments on “New correlations for wavy plate-fin heat exchangers: different working fluids”

Comments on “New correlations for wavy plate-fin heat exchangers: different working fluids”

New correlations for wavy plate-fin heat exchangers: different working fluids

Purpose– The main purpose of this paper is the generation of the heat transfer and pressure drop correlations by considering three working fluids, namely air, water, and ethylene glycol, for the wavy plate-fin heat exchangers (PFHEs).Design/methodology/approach– In order to present the general correlations, various models with different geometrical parameters should be tested. Because of the problems, such as difficult, long time, and costly fabrication of the wavy fins in experimental tests, computational fluid dynamics (CFD) calculations can be a useful method for the generation of the heat transfer and pressure drop correlations with eliminating the experimental problems. Hence, the effective design parameters of the wavy plate-fin, including fin pitch, fin height, wave length, fin thickness, wave amplitude, and fin length, and also their levels were recognized from the literature. The Taguchi method was applied to formulate the CFD simulation work.Findings– The simulation results were compared and validated with an available experimental data. The mean deviations of the Colburn factor,j, and Fanning friction factor,f, values between the simulation results and the experimental data were 3.74 and 9.07 percent, respectively. The presented air correlations and experimental data were in a good agreement, so that approximately 95 percent of the experimental data were correlated within ±12 percent. The j factor values varied for the different working fluids, while the f factor values did not sensibly change.Practical implications– The presented correlations can be used to estimate the thermal-hydraulic characteristics and to design of the compact PFHE with the wavy channels.Originality/value– This manuscript presents the new correlations for the compact PFHEs with the way channels by considering all the geometrical parameters and the working fluids with the different Prandtl numbers, 0.7, 7, and 150.

Foam Heat Exchangers: A Technology Assessment

Open-cell porous metal foams have received attention for use in compact heat exchangers due to their increasing availability and improved thermal performance. In recent years, considerable research has been conducted on use of metallic and nonmetallic foams to further improve performance of state-of-the-art heat exchangers. In this paper, we report preliminary results from fabrication, development and experimental investigation of thermal-hydraulic performance of high-temperature metal foam heat exchangers for automotive exhaust gas recirculation (EGR) system. A brief review of nickel–chromium and stainless-steel foam heat exchanger technology and of recent efforts on their manufacturing techniques for a liquid-to-air heat exchange application is presented. Measured heat transfer and pressure drop data for foam heat exchangers and their comparison with performance of a conventional wavy plate-fin heat exchanger are discussed. Technical challenges and risks associated with foam heat exchangers are discussed, along with recommendations for future development.

Studies on Fanning Friction (f) and Colburn (j) Factors of Offset and Wavy Fins Compact Plate Fin Heat Exchanger–A CFD Approach

The objective of this work is to address the uncertainties in the estimation of the Fanning friction (f) and Colburn (j) factors in a compact offset plate fin heat exchanger, and the generation of flow friction and heat transfer correlations in the form of f and j for compact wavy plate fin heat exchangers. A typical offset fin has been analyzed using FLUENT software (a general purpose computational fluid dynamics (CFD) simulation tool) for estimation of f and j data. These results are compared with the results of the available correlations in the literature and in-house experimental results. Uncertainties in estimation of f and j data are reviewed and the variations in the results are highlighted. In the case of wavy fin configuration, very limited correlations are available in the literature. Hence, with the objective of developing correlations, 18 different types of wavy fins geometries have been analyzed using a CFD tool to find out the f and j data in the laminar and turbulent regions. Multiple regression analysis has been carried out on the set of data to generate the correlations for f and j. These correlations have been compared with the experimental results of wavy fin reported in the literature.

Heat sinks with fluted and wavy plate fins in natural and low-velocity forced convection

The effect on heat transfer of geometrically rearranging the surface area of a finned heat sink is investigated. Novel heat sinks with fluted and wavy plate fin configurations are designed and fabricated together with conventional longitudinal-plate and pin fin heat sinks. The experimental apparatus, consisting of the guard heater assembly, isolation chamber, wind tunnel, and data acquisition instrumentation, is described. The thermal performance of the novel and conventional heat sinks is measured and compared for the horizontal and vertical base plate orientations under natural and low-velocity forced convection conditions. Results, presented as the Nusselt number against the Rayleigh or Reynolds numbers, reveal that the pin fin heat sink generally outperforms the other heat sinks, when the heat sink surface area is held constant. A significant effect on heat transfer of the orientation of the forced flow with respect to the buoyancy flow is observed. Overall, the novel heat sink designs do not yield significantly better thermal performance than an optimized conventional longitudinal-plate heat sink.