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An innovative tetramerous heat blade device for double pipe heat exchangers: An experimental study

APPLIED THERMAL ENGINEERING 2024年 257卷

作者： Jafari, Mohammad Lorestan Univ Fac Engn Mech Engn Dept POB 465 Khorramabad Iran

Heat pipes are renowned for their exceptional ability to efficiently conduct heat energy. In this study, we leverage this inherent capability to create an innovative flow turbulator aimed at enhancing the convection rate within a double pipe heat exchanger. We prioritized the simplicity of the turbulator and its flexibility to be redesigned for different sizes of heat exchange pipes, thereby extending its practical applications. The proposed device comprises four mini-sized rectangular heat pipes, named "heat blades" due to their shape. Each heat blade consists of a hollow copper shell containing two pieces of copper foam, serving as the wick. Acetone is employed as the base fluid within the heat blades. These heat blades are meticulously soldered around a copper base-ring. We manufactured and investigated devices with three different blade angles (0, 45, and 90). Four devices of each blade type were strategically soldered onto the inner pipe of the double pipe heat exchanger. We explored two distinct configurations: the + -form and x -form arrangements. The proposed turbulator significantly impacts the heat exchanger's thermal behavior, enhancing the overall heat transfer rate by up to 50%. This results in a thermal performance criterion ranging from 1.18 to 1.3, varying with different parameters. Comparing turbulators with different blade angles reveals that devices with a 90 degrees blade angle offer the best convection enhancement. However, considering the associated increase in pressure drops, the device with a 45(degrees) blade angle demonstrated the best overall performance. It is observed that the + -form configuration slightly outperformed the x -form configuration.

关键词： Heat Pipe Heat Blade Double-Pipe Heat Exchanger Metal Foam Energy Efficiency logarithmic mean temperature difference Heat Transfer Enhancement

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Liquid Cooling Systems for Batteries of Electric Vertical Takeoff and Landing Aircraft

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JOURNAL OF AIRCRAFT 2024年第3期61卷 667-683页

作者： Zhao, Chunrong Clarke, Matthew Kellermann, Hagen Verstraete, Dries Univ Sydney Sch Aerosp Mech & Mechatron Engn Sydney NSW 2006 Australia MIT Dept Aeronaut & Astronaut Cambridge MA 02139 USA Univ Illinois Grainger Coll Engn Urbana IL 61801 USA Bauhaus Luftfahrt Dept Aeronaut & Astronaut D-82024 Taufkirchen Germany Bauhaus Luftfahrt e V Munich Germany

Batteries are the lynchpin of electric vertical takeoff and landing (eVTOL) aircraft, and the high discharge rates pose a critical challenge to the battery thermal management system (BTMS). This work presents a channeled liquid cooling technology-based BTMS for eVTOL aircraft. During the flight, the heat generated from the batteries is partly extracted by circulating liquid coolant within a wavy channel (WC) attached firmly to the battery cells. The heat is then transported into a plate-fin compact heat exchanger (HEX), where all the heat is dissipated into the atmosphere. We report sensitivity analyses of the HEX model to shed light on the impact of the relevant design parameters on the BTMS size, weight, and power. We also examine critical parameters of the coupled WC-HEX BTMS in a one-dimensional off-design analysis. We demonstrate that the liquid cooling system can maintain the battery operating temperature within acceptable levels with a mass of less than 20% of the battery pack mass. Battery degradation using the liquid cooling system is reduced by over three times compared to an air-cooled system for both tilt-wing and lift+cruise eVTOL aircraft.

关键词： Newton's Law of Cooling Energy Storage and Batteries Thermal Control and Protection logarithmic mean temperature difference Battery Degradation Thermal Management System Electric Vertical Take-off and Landing Sensitivity Analysis Plate Fin Heat Exchanger Electric Aircraft

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Fluid Friction Effects on the Thermodynamic Performance of Spiral Plate Heat Exchangers

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2022年第3期36卷 466-484页

作者： Shirazi, Amir Hossein Sabouri Ghodrat, Maryam Behnia, Masud Univ New South Wales Canberra Sch Engn & Informat Technol Canberra ACT 2612 Australia Macquarie Univ Sydney NSW 2109 Australia

This paper presents a detailed analysis of the thermodynamic performance of spiral plate heat exchangers (SPHEs) and their channels by considering the fluid friction effect and no heat leakage to the environment. An optimal design algorithm for SPHEs is developed to find higher compactness and the overall heat transfer coefficient by increasing channels pressure drops, maintaining the geometric aspect ratio, and minimizing total costs. To determine the internal temperature distributions and the rates of heat transfer, a mathematical model is proposed. Fluid friction effects are examined as viscous heating;for this purpose, new parameters of the viscous heating entransy number and viscous heating entransy resistance are defined. Finally, various single-phase countercurrent SPHEs assuming a constant heat transfer rate, are modeled and compared in terms of energy, entropy generation, and entransy criteria. The results show the fluid friction effects as pressure drop effects in entropy generation are insignificant when compared to those caused by heat transfer. However, fluid effects as viscous heating in entransy analysis show that these effects can be rather significant in SPHEs with large spiral turn numbers or small values of heat capacity rate ratios. The obtained data suggest the significant role of entransy methods and their reliability to entropy generation methods in thermodynamic performance evaluation of SPHEs.

关键词： Fluid Friction Plate Heat Exchanger logarithmic mean temperature difference Entropy Generation Rate temperature Distribution Aspect Ratio Mathematical Models Thermal Performance Specific Heat Capacity Cold Stream

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Optimized Design of Delta-Wing Tapes for Target Thermal Performance Factor

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2022年第1期36卷 89-101页

作者： Huang, Cheng-Hung Lien, Jia-Ching Natl Cheng Kung Univ Dept Syst & Naval Mechatron Engn 1 Univ Rd Tainan 701 Taiwan

A three-dimensional double-sided delta-wing (D-T-W) shape design problem is studied in the present work to estimate the optimal wing-width ratio w/W, height-pitch ratio c/P, and attack angle alpha of D-T-Ws in a double-pipe heat exchanger for the target thermal performance factor using the Levenberg-Marquardt method and CFD-ACE+ software package. Our solutions indicate that a reasonable discrepancy exists between the numerical and experimental values of Nu and f because they are always within +/- 5% and +/- 9% errors, respectively. Then, three design cases, A, B, and C, based on a design template with L=100mm, are conducted numerically, and the resultant eta s are justified by comparing them with the plain tube (i.e., no inserts), longitudinal strip insert, and D-T-W tape insert design heat exchangers. The results reveal that considering w/W, c/P, and alpha as the design variables can indeed improve thermal performance factor eta. Finally, the optimal geometries of D-T-W tape inserts for cases A and B are used on a regular length L=2000mm. The results illustrate that design B with w/W=0.65, c/P=0.51, and alpha=72.90deg is considered as the optimized design of this work;its thermal performance factors can be further improved by 4.6%, 2.5%, and 3.3% for Re=5569, 10,630, and 14,540, respectively.

关键词： Thermal Performance Delta Wing Tube Heat Exchanger logarithmic mean temperature difference Angle of Attack Vortex Generators Vortices Heat Dissipation Specific Heat Capacity Friction Factor

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Enhancement of the Hydrothermal Characteristics of Fin-and-Tube Heat Exchangers by Vortex Generators

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2021年第1期35卷 152-163页

作者： Sahel, Djamel Ameur, Houari Alem, Karima Univ Amar Telidji Laghouat Dept Tech Sci Laghouat 00003 Algeria Univ Ctr Naama Dept Technol POB 66 Naama 45000 Algeria Univ Sci & Technol Oran 31000 Algeria Univ Sci & Technol Oran Mohamed Boudiaf Fac Mech Engn 1505 El Mnaouar Oran Algeria

Geometrical configurations of tubes and vortex generators have been optimized in order to improve the hydrothermal characteristics of fin-and-tube heat exchangers. The work is divided into two parts: the first part concerns the effects of the inclination angle of the oval tube (alpha=0, 10, 20, 30, 40, 50, 60, 70, 80, and 90 degrees);in the second part, the best case resulting from the first part is optimized by using the insertion of flat vortex generators. In this last part, the optimization is investigated by changing the number and position of flat vortex generators on the upper side of the tubes (cases 1 to 7). The obtained results have shown in the first part that the case of alpha=20 degrees ensures an enhancement in the heat transfer coefficient by 1-4% compared with the baseline case (alpha=0 degrees). In comparison with the case of alpha=20 degrees, further enhancement in heat transfer coefficient by about 62.53% has been achieved from the insertion of flat vortex generators. An optimal thermal performance factor of 3.58 has been obtained with the new suggested design (referred to case 7 in this paper).

关键词： Plain Fin and Tube Heat Exchanger Vortex Generators logarithmic mean temperature difference Thermal Diffusivity Friction Factor Turbulence Kinetic Energy Numerical Simulation Vortices Flow Characteristics Turbulence Models

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Performance evaluation of air-source heat pump based on a pressure drop embedded model

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HELIYON 2024年第4期10卷 e24634页

作者： Koopman, Tim Zhu, Tingting Rohlfs, Wilko Univ Twente Fac Engn Technol ET Dept Thermal & Fluid Engn NL-7522 NB Enschede Netherlands

An air-source heat pump simulation model, accounting for evaporator and condenser pressure drop, has been developed. The model is capable of computing the heat pump's coefficient of performance (COP) under different ambient temperatures and relative humidities above frosting conditions. This research extends an existing iterative simulation method that relies on the equalization of logarithmic mean temperature differences (LMTDs) calculated through two different approaches by adding a pressure drop simulation. Frictional and acceleration pressure drop is considered, computed iteratively. Simulation results for three different refrigerants, R410A, R32 and R290, are compared. The model's accuracy is validated by comparing simulated COP values with measured COP values from the reference heat pump datasheet. The model closely replicates the measured COP values above frosting conditions, with only a slight underestimation of approximately 1.5%. Results show a substantial impact of ambient temperature on the COP. For instance, an ambient temperature of 20 C-degrees, compared to 7 C-degrees, results in a COP increase of up to 35%, while an ambient temperature of -10 C leads to a 26% reduction in COP. Relative humidity enhances the COP if air moisture condensation becomes possible. Higher condenser capacities negatively affect the COP. The study highlights the differences in pressure drop characteristics between the condenser and the evaporator for the modeled heat pump, with maximum pressure drops of 220 kPa and 50 kPa for the condenser and evaporator, respectively. Additionally, the choice of refrigerant significantly influences pressure drop, with R32 displaying the lowest pressure drop, R410A showing the highest condenser pressure drop, and R290 causing the highest evaporator pressure drop.

关键词： Air-source heat pump Coefficient of performance Pressure drop logarithmic mean temperature difference Algorithm optimization

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Investigation of Heat Transfer to a Pulsating Flow in Plate Heat Exchangers

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2021年第2期35卷 421-427页

作者： Wang, Fei Zhang, Xiaobing Yang, Junyun Nanjing Univ Sci & Technol Sch Energy & Power Engn Nanjing 210000 Jiangsu Peoples R China

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Evaluating the Thermal Performance of Steam Condenser Heat Exchanger in a Coal Fired

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INTERNATIONAL JOURNAL OF HEAT AND TECHNOLOGY 2023年第1期41卷 179-186页

作者： Abdulateef, Ammar M. Bilad Alrafidain Univ Coll Dept Aeronaut Tech Engn Diyala 32001 Iraq

Steam condenser plays a vital role in the metabolism of a coal fired power plant used for generating the energy, which employed in various fields. The aim of this research is to determine the relationship between various parameters, such as heat transfer coefficient by convection (h), Condenser Pressure (CP), Cold Water Flow (CWF) rate and Cold Water temperature (CWT) towards evaluating the thermal performance of steam condenser unit. Experimental work is employed by four series based on condensate mass flow rate (Gcond), included G = 75 t/h, G = 50 t/h, G = 63 t/h and G = 89 t/h, respectively. The effect of condenser back pressure on power output from the turbine (N) and CWToutlet, as well as the effect of exhaust steam temperature (Texh) on h are investigated. logarithmic mean temperature difference (LMTD) is the major non-invasive method used for simulating this work by general heat transfer equations. The results obtained present the main characteristics of input and output parameters in addition to compression of the effect of CWTinlet on CP and h, respectively. The heat load via effectiveness as a function of CWF rate have also been reported. Ultimately, the findings obtained from CWT, CWF rate, CP and h of steam condenser have been validated. The water steam condenser has a number of important implications for further future practice to enhance the thermal power cycle of a coal fired power plant.

关键词： steam condenser back pressure turbine power output cold water temperature Cold Water Flow rate convection heat transfer coefficient logarithmic mean temperature difference

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Reduced-Order Computational-Fluid-Dynamics-Based Analysis of Aviation Heat Exchangers

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2020年第4期34卷 696-715页

作者： Ladeinde, Foluso SUNY Stony Brook Dept Mech Engn Nichols Rd Stony Brook NY 11794 USA

The goal envisioned for the Reduced-Order Computational Fluid Dynamics and Heat Transfer (ROM-CFDHT) procedure is obtaining fast turnaround in simulation time so that computational fluid dynamics can form a component of a system-level design tool. To accomplish this, a set of finite-element schemes is proposed, including the choice of the quadratic interpolation functions, the penalty approach, an intelligent error-control capability, a continuation method, a restart procedure that restores the integrity of the error-control scheme when the procedure encounters difficulties, and the consistent flux method. It is shown that for a natural convection problem simulation using fewer than 20 elements produces Nusselt number Nu results that agree with models using thousands of elements, with simulation time in seconds rather than hours. Forced convection over an asymmetrically laidout bank of tubes is simulated as another test of the proposed procedure. Three values of the Reynolds number, Re=10, 100, 1000 are investigated using two grids with significantly different levels of resolution and quality. The local distributions of Nu show some differences between the grids, but the mean results are comparable. The coarse grid could not calculate the Re=1000 case due to poor resolution and grid quality. A combination of grid resolution and choice of schemes enables successful simulation.

关键词： Computational Fluid Dynamics Heat Exchangers Aviation logarithmic mean temperature difference Natural Convection Galerkin Finite Element Method Reynolds Number Two Dimensional Flow Thermal Diffusivity Kinematic Viscosity

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Dyn2Heat – MILP Heat Exchanger Network Design for Batch Processes via Dynamic Optimization

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Computers & Chemical Engineering 2025年 200卷

作者： Dörthe Franzisca Hagedorn Laura Kuper Mats Zoellmann Christiane Reinert Niklas von der Assen Institute of Technical Thermodynamics RWTH Aachen University Schinkelstr. 8 52062 Aachen Germany

Nowadays, the energy efficiency of batch processes is getting increasing attention. Heat integration is an established approach to increase energy efficiency. However, compared to continuous processes, the temporally dynamic behaviour of batch processes introduces additional complexity to the heat exchanger network design problem. Furthermore, including investment costs of heat exchangers in the economic optimization problem requires spatial modelling of the heat exchangers. The spatial modelling usually leads to nonlinearities, which can lead to computational intractability. In our work, we demonstrate that both, the temporal and the spatial temperature profiles in a heat exchanger network for batch processes, can be modelled efficiently by differential equations. We introduce the Dyn2Heat model, a dynamic optimization model for heat exchanger network design for batch processes. The Dyn2Heat model considers the economic trade-off between process duration, investment costs for heat exchangers and operational costs for utility supply. At the same time, the dynamic formulation makes the model computationally efficient in comparison to a nonlinear algebraic formulation and applicable to complex systems involving several possible heat exchangers.

关键词： Energy Efficiency Heat Integration Pinch Method logarithmic mean temperature difference Dynamic Processes Ordinary Differential Equations

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