A review of metal foam and metal matrix composites for heat exchangers and heat Sinks

Recent advances in manufacturing methods open the possibility for broader use of metal foams and metal matrix composites (MMCs) for heat exchangers, and these materials can have tailored material properties. Metal foams in particular combine a number of interesting properties from a heat exchanger's point of view. In this paper, the material properties of metal foams and MMCs are surveyed, and the current state of the art is reviewed for heat exchanger applications. Four different applications are considered: liquid-liquid, liquid-gas, and gas-gas heat exchangers and heat sinks. Manufacturing and implementation issues are identified and discussed, and it is concluded that these materials hold promise both for heat exchangers and heat sinks, but that some key issues still need to be solved before broad-scale application is possible

Computational Modeling of Vehicle Radiators Using Porous Medium Approach

A common tool for the determination of thermal characteristics of vehicle radiators is the experimental testing. However, experimental testing may not be feasible considering the cost and labor-time. Basic understanding of the past experimental data and analytical/computational modeling can significantly enhance the effectiveness of the design and development phase. One such computational modeling technique is the utilization of computational fluid dynamics (CFD) analysis to predict the thermal characteristics of a vehicle radiator. However, CFD models are also not suitable to be used as a design tool since considerable amount of computational power and time is required due to the multiple length scales involved in the problem, especially the small-scale geometric details associated with the fins. Although fins introduce a significant complexity for the problem, the repetitive and/or regular structure of the fins enables the porous medium based modeling. By porous modeling, a memory and time efficient computational model can be developed and implemented as an efficient design tool for radiators. In this work, a computational methodology is described to obtain the hydrodynamic and thermal characteristics of a vehicle radiator. Although the proposed methodology is discussed in the context of a vehicle radiator, the proposed methodology can be implemented to any compact heat exchanger with repetitive fin structures which is an important problem for many industrial applications

Steam Coil Air Heater (SCAH) Modelling as Porous Medium to Analyze Flow Characteristic and Reduce Self Energy Usage in Gresik Unit 1 Steam Power Plant

This study deals with flow and heat transfer characteristic in a Heat Exchanger if its tube modules completely or partially dismantled. The heat exchanger is a Steam Coil Air Heater (SCAH) Installed in Gresik unit 1 Steam Turbine Power Plant. Nowadays the power plant operate mostly utilized natural gas as a fuel. When it utilized natural gas SCAH are not give benefit and only give flow resistance for combustion air flow. This study use numerical simulation model with commercial Computational Fluid Dynamic (CFD) software. The simulation on 3D model with steady state flow condition. The model use energy model, Heat Exchanger Model, realizable k-Epsilon for turbulence viscous model and SCAH model as Porous Medium (PM). Modelling SCAH as a PM will avoid time consuming mesh generation and simulations with high CPU usage. Fives scenarios of tube module dismantling simulated in 100% load. This study result both quantitative and qualitative data coresspond with flow and heat transfer characteristic. The model with original scenarios give good result in terms of pressure and outlet temperature with commisioning data. The contour data results show there are several secondary flow due to enlargement of flow area. Numerical results of variation S1,S2,S3,S4 are indicated decreasing total pressure drop about 32.27%, 51.29%, 47.04%, 65.25% respectively. And temperature rise for each schenario will decrease to 29.29% (S1), 46.51% (S2) , 47.92% (S3), 68.28% (S4) respectively,except for S5 have no pressure drop and temperature rise since all module are dismantled

Heat exchanger/reactors (HEX reactors): Concepts, technologies: State-of-the-art

Process intensification is a chemical engineering field which has truly emerged in the past few years and is currently rapidly growing. It consists in looking for safer operating conditions, lower waste in terms of costs and energy and higher productivity; and away to reach such objectives is to develop multifunctional devices such as heat exchanger/reactors for instance. This review is focused on the latter and makes a point on heat exchanger/reactors. After a brief presentation of requirements due to transposition from batch to continuous apparatuses, heat exchangers/reactors at industrial or pilot scales and their applications are described

Enhancement of the Hydrodynamic Characteristics in Shell-and-Tube Heat Exchangers by Using W-Baffle Vortex Generators

Improving the hydrodynamic characteristics of STHECs (Shell-and-Tube Heat Exchanger Channels) by using BVGs (Baffle-type Vortex Generators) is among the common passive methods due to their proved efficiency. In this computational investigation, the same method is used to enhance the hydrodynamic behavior of STHECs, by inserting W-shaped Baffle-type Vortex Generators. The numerical model represented by the computational FVM (Finite Volume Method) is used to simulate and analyzed the considered physical model. The fluid used is air, its thermal physical properties are constant, turbulent, incompressible, and its temperature is 300 K at the inlet section of the STHEC. The flow velocity ( Uin ) and atmospheric pressure ( Patm ) are considered as boundary conditions at the entrance (x = 0) and exit (x = L) of the channel, respectively. The results showed that the friction coefficients were related to the pressure, velocity, and Reynolds number values. High values of Re yielded an acceleration of the fluid, resulting thus in increased pressure on the solid walls and augmented friction values

Numerical investigation on various heat exchanger performances to determine an optimum configuration for charge air cooler, oil and water radiators in F1 sidepods

The present work focuses on a three-dimensional CFD approach to predict the performance of various heat exchangers in conjunction with non-isothermal transitional flows for motorsport applications. The objective of this study is to determine the heat transfer, pressure drop and inhomogeneous flow behaviour for distinct heat exchangers to identify an optimum configuration for the charge air cooler, water and oil radiators placed in the sidepods of a formula one (F1) car. Therefore, a comprehensive analysis of various heat exchanger configurations has been carried out in this work. In order to assess the reliability of the obtained results, a mesh sensitivity study along with additional parametric investigations have been performed to provide numerical parameters predicting accurately (a) the heat transfer rate at the fluid-solid interface and (b) the sporadic separation. As a result of the performed validation procedure in this study, the aerodynamic- and thermal boundary layer development along with the convective characteristics of the air flow have been captured accurately near to the heated surface. The characterization of a heat exchanger core and a core configuration in a closed domain is also possible with this procedure. The presented three-dimensional CFD approach could overcome the difficulties of macroscopic heat exchanger and porous media methods for F1 applications, because it can be used to predict the heat transfer and pressure drop related to the mass flow rate correlation curves. The contribution of fins to the total heat transfer rate has been predicted theoretically, and application benchmark test cases have been presented to analyze five different heat exchanger configurations in accordance with the 2014 formula one technical regulations. The numerical data extracted directly from three-dimensional CFD simulations can be used in the sidepod design process of the external cooling system of F1 engines

Three-dimensional numerical simulation of fluid flow and heat transfer in fin-and-tube heat exchangers at different flow regimes

This thesis aims at unifying two distinct branches of work within the Heat Transfer Technological Center (CTTC). On one side, extensive experimental work has been done during the past years by the researchers of the laboratory. This experimental work has been complemented with numerical models for the calculation of fin and tube heat exchangers thermal and fluid dynamic behavior. Such numerical models can be referred to as fast numerical tool which can be used for industrial rating and design purposes. On the other hand, the scientists working at the research center have successfully developed a general purpose multi-physics Computational Fluid Dynamics (CFD) code (TermoFluids). This high performance CFD solver has been extensively used by the co-workers of the group mainly to predict complex flows of great academic interest. The idea of bringing together this two branches, comes from the necessity of a reliable numerical platform with detailed local data of the flow and heat transfer on diverse heat exchanger applications. Being able to use local heat transfer coefficients as an input on the rating and design tool will lead to affordable and accurate prediction of industrial devices performance, by which the center can propose enhanced alternatives to its industrial partners. To accomplish these goals, several contributions have been made to the existing TermoFluids software which is in continuous evolution in order to meet the competitive requirements. The most significant problematics to adequately attack this problem are analyzed and quite interesting recommendations are given. Some of the challenging arising issues involve the generation of suitable and affordable meshes, the implementation and validation of three dimensional periodic boundary condition and coupling of different domains with important adjustments for the study of cases with different flow physics like time steps and thermal development. Turbulence is present in most of engineering flows, and refrigeration evaporator heat exchangers are not an exception. The presence of many tubes (acting like bluff bodies for the flow) arranged in different configurations and the fact that the flow is also confined by fins, create complex three dimensional flow features that have usually turbulent or transition to turbulent regime. Therefore, three dimensional turbulent forced convection in a matrix of wall-bounded pins is analyzed. Large Eddy Simulations (LES) are performed in order to assess the performance of three different subgrid-scale models, namely WALE, QR and VMS. The Reynolds numbers of the study were set to 3000, 10000 and 30000. Some of the main results included are the pressure coefficient around the cylinders, the averaged Nusselt number at the endwalls and vorticity of the flow. The final part of the thesis is devoted to study the three dimensional fluid flow and conjugated heat transfer parameters encountered in a plate fin and tube heat exchanger used for no-frost refrigeration. The numerical code and post processing tools are validated with a very similar but smaller case of a heat exchanger with two rows of tubes at low Reynolds for which experimental data is available. The next analysis presented is a typical configuration for no-frost evaporators with double fin spacing (for which very few numerical data is reported in the scientific literature). Conjugated convective heat transfer in the flow field and heat conduction in the fins are coupled and considered. The influence of some geometrical and flow regime parameters is analyzed for design purposes. In conclusion, the implementations and general contributions of the present thesis together with the previous existent multi-physics computational code, has proved to be capable to perform successful top edge three dimensional simulations of the flow features and heat transfer mechanisms observed on heat exchanger devices.Esta tesis tiene como objetivo unificar dos ramas de trabajo dentro del Centro Tecnológico de Transferencia de Calor (CTTC). Por un lado, se ha realizado un amplio trabajo experimental durante los últimos años. Este trabajo experimental se ha complementado con modelos numéricos para el estudio de intercambiadores de calor de tipo aleta-tubo. Tales modelos numéricos pueden considerarse una herramienta numérica de bajo coste empleada con propósitos de diseño principalmente. Por otro lado, los científicos que trabajan en el centro han desarrollado con éxito un código de Dinámica de Fluidos Computacionales (TermoFluids). Este código de alto rendimiento ha sido ampliamente utilizado principalmente para predecir flujos complejos de gran interés académico. La idea de unir a estas dos ramas, proviene de la necesidad de una plataforma numérica fiable con datos locales propios del flujo y de la transferencia de calor en diversas aplicaciones de intercambiadores de calor. Ser capaz de generar coeficientes locales de transferencia de calor para abastecer con datos propios los modelos existentes de bajo coste, permitirá la correcta predicción del rendimiento de dichos dispositivos. Para lograr estos objetivos, se han hecho varias contribuciones al código TermoFluids que está en continua evolución. Algunas de las mayores cuestiones que se plantean implican la generación de mallas adecuadas y asequibles, la implementación y validación de la condición de contorno periódica tridimensional y el acoplamiento de los diferentes dominios para el estudio de casos con diferentes comportamientos físicos, como desarrollo transitorio e inercia térmica. La turbulencia está presente en la mayoría de los flujos de ingeniería, y los intercambiadores de calor de evaporadores para refrigeración no son una excepción. La presencia de muchos tubos (que actúan como obstáculos para el fluido) colocados en diferentes configuraciones y el hecho de que el flujo también está confinado por aletas, crean características de flujo tridimensionales complejas que tienen generalmente régimen turbulento o en transición. Por lo tanto, se analiza la convección forzada turbulenta en una matriz de pines delimitados por paredes. simulando las grandes escalas de turbulencia y modelando las pequeñas (LES) con el fin de evaluar el desempeño de los tres modelos seleccionados, a saber WALE, QR y VMS. Los números de Reynolds establecidos para el estudio son 3000, 10000 y 30000. Algunos de los principales resultados que se incluyen son el coeficiente de presión alrededor los cilindros, el número de Nusselt promedio en las paredes y la vorticidad del flujo. La parte final de la tesis se dedica a estudiar el flujo tridimensional y los parámetros de transferencia de calor encontrados en un intercambiador de calor de tipo aleta-tubo utilizado para la refrigeración doméstica en equipos de 'no-escarcha'. Las implementaciones del código y el postproceso numéricos se validan en un caso muy similar para un intercambiador de calor con dos filas de tubos a bajos Reynolds para el cual se dispone de datos experimentales. El siguiente análisis que se presenta es una configuración típica para evaporadores 'no-escarcha' con paso de aleta doble (para el que se tiene muy poca información numérica en la literatura). Se considera el acoplamiento conjugado de la transferencia de calor convectiva entre fluido y sólido y conductiva dentro de la aleta. La influencia de algunos parámetros geométricos y de régimen de flujo se analizan con propósitos de diseño. En conclusión, las contribuciones generales de esta tesis junto con el código computacional ya existente, ha demostrado ser capaz de realizar con éxito simulaciones tridimensionales para predecir las características del flujo y los mecanismos responsables de la transferencia de calor en intercambiadores de calor de tipo aleta-tuboPostprint (published version

A detailed hydrothermal investigation of a helical micro double-tube heat exchanger for a wide range of helix pitch length

The present study was numerically inquired the heat transfer performance and fluid flow characteristic of a helical micro double-tube heat exchanger (HMDTHX) using the finite volume method. The tube length was considered to be constantly equal to 30 mm, and 12 different configurations were modeled by changing in turn number and pitch length (P) for Reynolds numbers of 50, 100, 150, and 200. The findings indicated that the heat transfer would enhance by applying any helix angle in the straight tube. However, it had an optimum point which varied by Reynolds number (Re). Rising Re caused overall heat transfer coefficient (OHTC), pressure drop, and pumping power augment for all cases. Increasing P in overall reduced OHTC, pressure drop, and pumping power which had different maximum points between P = 0.5 to 3. Maximum overall heat transfer coefficient (OHTC) enhancement was equal to 45% for Re = 200 and P = 2. Also, maximum effectiveness was 11.5% for P = 2 and Re = 200. Moreover, a 42% maximum increment was achieved for pressure drop, pumping power, and friction factor at Re = 200 and P = 2. Shear stress for Re = 100 to 200 showed that the values are almost the same for P = 0.5 and 1. Then by increasing P, the shear stress decreases. While, for Re = 50, a maximum is seen at P = 2. The temperature distribution was indicated that the maximum temperature of the straight tube and helical tube are the same, but the difference is in the average temperature, which was 3.2 K between straight and helical tubes. Finally, by investigating the velocity contour, it was determined that a secondary flow through the HMDTHX, affected by centrifugal force, was existed, enhancing the fluid flow turbulency and heat transfer rate

A macroscopic particle modelling approach for non-isothermal solid-gas and solid-liquid flows through porous media

© 2019 Elsevier Ltd The complexity of multiphase flows in many engineering systems such as heat exchangers signify the need to develop new and advanced numerical models to analyse the interactions the working fluid and unwanted solid foulants. Fouling is present in a myriad of industrial and domestic processes and it has a negative impact on the economy and the environment. The mechanisms that govern non-isothermal solid-fluid flow through porous metal foam heat exchangers are complex and poorly understood. In this research, a coupled finite volume method (FVM) and macroscopic particle model (MPM) is developed and implemented in ANSYS Fluent to examine the transient evolution of a non-isothermal multiphase solid-fluid flow and the interaction between coupled interactions of solid particles, fluid, and porous media. The maximum particle temperature is dependent on the fluid and solid particle thermo-physical properties in addition to the temperature of the cylindrical ligaments of the porous media. The present results show that the smallest solid particles reach the highest temperatures in the porous heat exchanger and at low inlet velocities, the highest particle temperatures are realized. The results pertaining to maximum particle temperatures are prevalent in many industrial processes and acquiring knowledge of the maximum particle temperature serves as a steppingstone for comprehending complex multiphase solid-fluid flows such as the cohesiveness between the particles and the particle adhesion with the walls. The results of these studies could potentially be used in the future to optimize metal foam heat exchanger designs