Automotive grade 3 electronic components are expected to meet their functional, performance and thermal safety requirements within the ambient temperature range from −40-degree C to +85-degree C. In this study, CFD and thermal analysis of electronic control circuitry of a power steering wheel column adjustment system is performed. It consists of 6 MOSFETs (Metal Oxide Semi-Conductor Field Effect Transistor) packaged in 3 Dual package MOSFET casings (Q6, Q7 and Q8) that are arranged in two H-bridge configurations for dependent control of the two motors. Two of these MOSFETs cause thermal power dissipation during the normal operation of the system. There are also other thermally significant devices such as a reverse polarity protection MOSFET (Q1), two inductors used in a low pass filter and one current sense resistor. Because of cost and packaging limitations, there are no external heat sinks to enhance heat transfer. The components will rely on the Printed Circuit Board (PCB) and plated-through-holes/thermal vias for heat transfer to maintain operation within the thermal safety limits. The inherent transient nature of operation of the power steering wheel column adjustment system causes the circuit to draw high current for a short duration of time. This necessitates temperature dependent heat source formulation. In this study, an initial CFD study was performed to assess the thermal safety of all the electronic components in the control circuitry. It was found that the electronic components such as MOSFETs and inductors were below the maximum operating junction temperature under the hot limit condition (+85degree C) for the entire duration of operation. However, under the cold limit condition (−40-degree C), both the MOSFETs and the inductors were significantly hotter than the maximum junction temperature. Based on CFD results, the sizing and placement of thermal vias may be optimized. Further, a comparative analysis was performed to assess the different levels of fidelity offered by lumped PCB model, multi-layer PCB model and explicit modeling of thermal vias in PCB.

Ferrofluid channel flows have been used for many non-invasive flow manipulation applications, including drug-delivery, heat transfer enhancement, mixing enhancement, etc. Heat transfer enhancement is one of the most coveted outcomes from novel cooling systems employed for electronic cooling. While using Ferrofluids for heat transfer enhancement, the external magnetic field usually induces Kelvin Body Force, which causes the ferrofluid to swirl or ‘mix’. This mixing process causes extra convection over what is induced through fluid inertia and is responsible for heat transfer enhancement. In order to understand the phenomenon of heat transfer enhancement, it would be logical to view it from the perspective of mixing enhancement. Moreover, channel flows are most common in liquid cooling of electronics equipment, and hence such a fundamental understanding of synergies between mixing and heat transfer enhancement can help pose design rules for advanced cooling configuration for electronics cooling. In this work, a Ferrofluid channel flow is analyzed in the presence of an external magnetic field. A 2-D 90° bend channel ferrofluid flow is considered, with a significant length scale of 0.01 m, where two external current-carrying wires provide an external magnetic field. An external inward heat flux of 1000 W/m 2 is applied on the walls of the channel. The channel flow is studied numerically by varying different parameters relating to the external magnetic field and flow conditions. The ferrofluid used is considered magnetite based on water as the carrier fluid, and the properties of which are modeled using appropriate mixture models for nanofluids. The mixing induced in the flow is characterized by using two different mixing numbers based on the flow velocity. This type of characterization is analogous to characterizing flow turbulence. The heat transfer enhancement is characterized using Nusselt numbers. These non-dimensional numbers (mixing) are studied in congruence with the Nusselt number to understand the relationship between the mixing and heat transfer and draw comparative inferences with flow conditions without heat transfer enhancement. Finally, conclusions are drawn between the mixing & heat transfer intensification at local and global levels and choosing the apposite mixing numbers to characterize heat transfer enhancement.

Extruded radial fin heat sinks are typically used in power electronics for temperature management. The goal of this study is to compare the temperature predictions of LPTN (Lumped Parameter Thermal Network), Finite element based thermal analysis (using ANSYS Mechanical) and Finite volume based CFD (Computational Fluid Dynamics) & thermal analysis in power electronics hardware. The power electronics hardware under study is used for control of compressors / heaters used in a medical thermal management device. The hardware consists of 2 SCRs (Silicon Controlled Rectifiers) and 2 TRIACs (TRIodes for Alternating Current) arranged in straight in-line configuration with the TRIACs having a higher internal heat generation (1.643E7 W/m 3 ) than the SCRs (4.53E6 W/m 3 ). Each of these four devices is bolted to a separate anodized aluminum heat sink using a TIM (Thermal Interface Material). It was found that CFD based Conjugate Heat Transfer (CHT) analysis with S2S (Surface to Surface) Radiation transfer gave the most accurate thermal predictions (within 6°C). These were comparable to the predictions from 3-D Solid energy equation with uniform convection and S2S radiation. Depending on the availability of computational time and resources, either full CHT study or 3-D Solid energy equation based thermal analysis with uniform convection and S2S radiation is recommended for initial design study.

In this article, investigations of the dynamic behaviors of a single bubble flowing across a mesh-based structure domain was conducted using the volume of fluid (VOF) model. The study was investigated in various mesh structure sizes, including hole size and gap distance. The fundamental behavior of bubble deformation and the effects of gap sizes were analyzed. Subsequently, the predicted dynamics of the deforming bubble area and the effect of the surface tension were examined inside the mesh holes. The discharging bubbles from the mesh structure resulted in a slight difference in the physical features from the original bubble dynamics before entering the mesh (flow restriction). This drafted the bubbles in different trajectories and led to behave differently based on the mesh characteristics. The complex interactions and the subsequent deformations were observed between different mesh sizes. For the validation of the bubble dynamics, the results of computational fluid dynamics (CFD) simulation were tested under different mesh sizes detailing the velocity field, exiting trajectory, bubbles deformation, and residence time, which helps to reveal the affected parameters on the separation mechanism of the original bubble.

Current state-of-the-art development of concentrated solar power (CSP) applications target cost-effective and highly efficient processes in order to establish commercialization of these technologies. The design of solar receivers/reactors and their respective flow configuration have a direct impact on the operational performance of the solar thermochemical processes. Thermal efficiencies, reaction kinetics and other key output metrics are the intrinsic result of the chosen configuration. Therefore, reactor design optimization plays a crucial role in the development of solar thermochemical applications. In this study a computational fluid dynamics (CFD) model of a directly-irradiated cavity receiver has been developed. The CFD-domain is coupled with incoming radiation that is obtained by using Monte Carlo Ray Tracing (MCRT). Experimental campaigns of the cavity receiver were carried out using a 7 kW High Flux Solar Simulator (HFSS) as radiative source. Temperature readings were obtained at different locations inside the cavity receiver for both wall and gas temperatures. In order to mimic naturally changing insolation conditions, the HFSS was run at different power levels. Heat flux at the aperture of the solar receiver was experimentally characterized. The acquired heat flux maps validated the intermediate results obtained with the MCRT method. The coupled computational model was validated against the measured temperatures at different locations inside the receiver. Computed temperature contours inside the receiver confirmed the experimentally observed non-uniformity of the axial temperature distribution. The validated analysis presented in this paper was then used as a baseline case for a parametric study. Design optimization efforts were undertaken towards obtaining temperature uniformity and achieving efficient heat transfer within the fluid domain. Enhanced flow circulation was achieved which yielded temperature uniformity of the receiver at steady state conditions. The outcome of this parametric analysis provided valuable insights in the development of thermal efficient solar cavity receivers. Hence, findings of this study will serve as a starting point for future solar reactor design. For example, it was found that reversing flow direction has an adverse effect on the temperature uniformity inside the receiver. Similarly, increasing the inlet angle does not positively affect the temperature distribution and hence should be chosen carefully when designing a solar reactor.

Pool boiling and in-tube condensation phenomena have been investigated intensively during the past decades, due to the superior heat transfer capacity of the phase change process. In passive heat removal heat exchangers of nuclear power plants, the two phase-change phenomena usually occur simultaneously on both sides of the tube wall to achieve the maximum heat transfer efficiency. However, the studies on the effects of in-tube condensation on external pool boiling heat transfer are very limited, especially in numerical computation aspect. In the present study, the saturated pooling boiling over a vertical tube under the influences of in-tube steam condensation is investigated numerically. The Volume of Fluid (VOF) interface tracking method is employed based on the 2D axisymmetric Euler-Euler multiphase frame. The phase change model combining with a mathematical smoothing algorithm and a temporal relaxation procedure has been implemented into CFD platform by user defined functions (UDFs). The two-phase flow pattern and bubble behavior have been analyzed. The effects of inlet steam mass flow rate on boiling heat transfer are discussed.

A computational simulation of the thermo hydraulic performance of a trapezoidal Off Set Strip Fin (OSF) is performed. The simulations are carried for Reynolds number ranging from 300 to 9000 considering three-dimensional conditions (3D). Calculations were developed assuming a constant flow. Colburn factor j , and the friction factor f , were calculated. Uniform temperature condition is assumed at the solid surface and at the inlet. The results have been compared with studies made by Kays and London, (1984), Manglik and Bergles (1990), and Muzychka and Yovanovich, (2001). According to the obtained results, it can be concluded that Computational Fluid Dynamics (CFD) is able to explore the behavior and performance of this kind of fin, showing that the hydraulic performance is well represented by correlations widely used in literature, while thermal performance seems to be under predicted.

A three-dimensional multi-phase, multi-species, turbulent reacting flow computational fluid dynamics (CFD) model was established to simulate fluid catalytic cracking (FCC) process inside an industrial FCC riser. FCC catalyst, oil, and air were used as the solid, liquid, and gas phases, respectively. A hybrid technique for coupling chemical kinetics and hydrodynamics computations was employed, where the simulation was divided into (a) reacting flow hydrodynamic simulation with a small but sufficient number of lumped reactions to compute flow filed properties and (b) and reacting flow hydrodynamics with many subspecies where complex chemical reactions occur. A four-lump kinetic model was used for the major species and a fourteen-lump kinetic model was used for the subspecies model. The results were validated against measurements from the actual riser.

The blast furnace process is a counter-current moving bed chemical reactor to reduce iron oxides to iron, which involves complex transport phenomena and chemical reactions. The iron ore and coke are alternatively charged into the blast furnace, forming a layer by layer structural burden which is slowly descending in the counter-current direction of the ascending gas flow. A new methodology was proposed to efficiently simulate the gas and solid burden flow in the counter current moving bed in blast furnace shaft. The gas dynamics, burden movement, chemical reactions, heat and mass transfer between the gas phase and solid phase are included. The new methodology has been developed to explicitly consider the effects of the layer thickness thermally and chemically in the CFD model.

A novel liquid-cooled (50-50 ethylene glycol-water mixture) composite cold plate made of phase-change material (PCM) is proposed as a thermal management solution for energy storage systems (ESS) in hybrid-electric vehicles (HEV). The composite cold plate is lighter than a traditional aluminum cold plate and able to absorb high heat flux spikes. Furthermore, the pump operation time is reduced. The goal of the present study is to evaluate the effectiveness of a preliminary PCM cold plate subjected to constant heat flux. The inlet temperature of the working fluid is parametrically varied and results include PCM temperatures and pump operation times.

Selective Catalytic Reduction (SCR) is an important air pollution control process that consists of injecting ammonia (NH 3 ) into the boiler flue gas and passing the flue gas through a catalyst bed where the NO x and NH 3 react to form nitrogen gas (N 2 ) and water vapor (H 2 O). [1] At a coal-fired power station, a decomposition chamber uses combustion air and a natural gas burner to provide the necessary temperature, air flow and pressure to convert the injected urea solution into ammonia gas. The inspections of this decomposition chamber indicate debris formations occurring at the burner/roof block the chamber from achieving proper temperature for conversion and redirect the burner flame/flow, which can potentially shift the flow pattern in the chamber. In order to identify the cause of this debris formation, Computational Fluid Dynamics (CFD) and Virtual reality fVR have been employed to simulate and visualize the flow distribution and species concentration inside this decomposition chamber. By analyzing the simulation data, excessive ammonia recirculation had been identified as the cause of the debris formation at the top of the chamber. Parametric studies have also been conducted to optimize the existing chamber design by introducing multiple turning vanes to eliminate the excessive recirculation, thus minimizing debris formation.

Fluid catalytic cracking (FCC) is one of the most important conversion processes in petroleum refineries, and FCC regenerator is a key part of an FCC unit to recover the solid catalyst activity by burning off the deposited coke on the catalyst surface. In modern FCC units, regenerator is a cylindrical vessel. Carrier gas transports the solid catalyst from the stripper and feeds the catalyst into the regenerator through catalyst distributors. The catalyst is fluidized by the air that is injected into the regenerator through air rings in the bottom part of the cylindrical vessel. A three-dimensional multi-phase, multi-species reacting flow computational fluid dynamics (CFD) model was established to simulate the flow inside an FCC regenerator. The two phases involved in the flow are gas phase and solid phase. The Euler-Euler approach, where the two phases are considered to be continuous and fully inter-penetrating, is employed. The model includes gas-solid momentum exchange, gas-solid heat exchange, gas-solid mass exchange, and chemical reactions. Chemical reactions incorporated into the model simulate the combustion of coke which is present on the catalyst surface. The simulation results show a good agreement with plant data.

The thermal vapor compressor (TVC) is an essential part that governs the overall process in the MED (Multiple-Effect Distillation) -TVC system. The flow and heat transfer in the TVC is very complex due to the strong compressibility, non-equilibrium phase change and supersonic turbulent flow of the stream. So in improving the performance of an ejector system, an investigation of the characteristics for the heat transfer and high speed flow in inside the ejector is often required. In the present study, the supersonic steam flow with non-equilibrium phase change and condensation shock was numerical studied based on the computational fluid dynamics (CFD) method. The special phenomena in the supersonic steam flow in the nozzle were investigated. The effects of various operating pressures and temperatures on the nozzle performance were investigated. The research explored the effect of steam pressure, temperature, supercooling level and super-saturation ratio on the onset of the nucleation and the intensity of condensation shock in the supersonic steam flow.

A power plant boiler is widely used as a heat source for generating steam through fuel combustion. Operations trainees at NIPSCO coal-fired power stations receive short-term training in boiler operation procedures and are given 2D, non-scaled representations of the plant’s steam, coal cycle, and limited key components. This study focused on pursuing a more efficient way of representation by using a three-dimensional (3D) numerical model of the power plant boiler and a Virtual Reality platform. Coal and air are injected into ten cyclones of the boiler to undergo violent combustion and release the heat to the tubes along both cyclone and furnace walls. In order to obtain a better understanding of the boiler operation process, which cannot be achieved in reality, Computational Fluid Dynamics (CFD) was employed to simulate the boiler components and the entire combustion procedure. Simulation results presented detailed transient flow characteristics and temperature gradients inside cyclones and the furnace to achieve a thorough understanding of the internal gas flow pattern. Also, the Virtual Reality (VR) platform of a power plant boiler was developed by combining the simulation data inside the boiler and visualization of model image outside the boiler to provide a vivid 3D representation for trainees.

The treatment of sphere contact is a crucial issue on the numerical analysis of the flow and heat transfer in packed beds of particles. In this work, the effects of three different methods including introducing a gap, area contacting and cylindrically bridging on the flow and heat transfer performances of structured packed beds of particles are investigated with CFD methods. The simulation results have shown that the influence of different treatment methods on the contact point on flow and heat transfer gets greater as the porosity decreases and the Reynolds number increases. There are no large differences among these three methods on the pressure drop and heat transfer under laminar flow regime. Compared with the experimental results, cylindrically bridging method is proved to be reasonable to simplify the sphere–sphere contact points. Therefore, cylindrically bridging treatment method is encouraged to be used instead of point contact method between particles with CFD analysis in structured packed beds of particles.

In this paper, a numerical model of the thermodynamic process was developed, by using CFD (software) technique and considering the gas flow, the diffused combustion and the radiative heat transfer in the molten salt furnace. This model aims to optimize the operating parameters. Simulation results demonstrate that the performances of the salt furnace can be improved by optimization. The temperatures along the fire wall circumference are quite even, and the deviant combustion phenomenon is not observed. A back-flow formed in the upper part of the furnace chamber enhances the circulation and the mixing of the gas, helping to effectively stabilize the combustion in the furnace. The behaviors of CO, CO 2 , NOx and H 2 O are presented in terms of the gas flow, temperature distribution and volumetric concentration distribution. The furnace with the constant air flow rate of 15500Nm 3 /h and the angle of guide vane at 48∼50 ° can increase the combustion effectiveness.

The present work describes development of an educational web portal for performing virtual experiments. Graduate students often conduct laser based optical measurements to study fundamentals of heat transfer and fluid flow. An attempt has been made to meet the same requirements with virtualization using computational tools. OpenFOAM, an open source fluid flow simulator serves as a backbone for this initiative. A new Foam solver is developed to incorporate an additional convective heat transfer equation, account for natural convection effects, implement specific boundary conditions of interest and represent all the required class of physics as required from a pedagogical perspective. The solver is tested for accuracy by comparing results with experiments and available data in the literature. Apart from access of the source code to students, open source methodology makes it free from any licensing restrictions allowing wider deployment across multiple schools simultaneously. Even if large number of students access the web portal at the same time, all simulations can be launched without any licensing restrictions, provided computing power is available. A suite of twelve examples covering steady and unsteady flow patterns is studied in the first phase. The graphical nature of results helps students to easily recall specialized phenomena such as transients, flow circulation patterns in natural convection and vortex shedding. A comparison with laser based experiments via interferograms and schlieren images proves useful to correlate the experimental results with physically realizable temperature fields.

The reduction of greenhouse gas emissions is essential to mitigate the impact of energy production from fossil fuels on the environment. Oxyfuel technology is a process developed to reduce emissions from power stations by removing nitrogen from air and burning the fossil fuels in a stream of pure oxygen. The remaining oxidiser is composed of recycled flue gas from the furnace to reduce temperatures. The product of this system is a flue gas with very high carbon dioxide concentration enabling more efficient capture and storage. Accurate modelling of oxyfuel is essential to gain better understanding of the combustion fundamentals and obtain accurate predictions of properties within the furnace that cannot be measured. Heat transfer to the furnace walls will be affected due to the different composition of the gases in the furnace. Carbon dioxide has higher heat capacity than nitrogen. Water vapour and carbon dioxide also exhibit absorption spectra of radiation in the infra-red region of the spectrum relating to wavelengths observed in combustion. Accurate CFD modelling of radiative heat transfer in oxyfuel combustion will require improvements to the radiative properties model to account for the spectral nature of radiation. In addition the impact of the solid fuel particles, soot and ash are considered. Several different radiative properties models have been tested to assess the impact on the predicted radiation and temperatures under air and oxy firing conditions. The results for radiation transferred to the walls are highly dependent upon the model chosen and the need for an accurate radiative properties model for oxyfuel firing, such as the full-spectrum k-distribution method is demonstrated.

The uniform flow rate is a fundamental requirement in the design of air distributors for the hydrogen reformer furnace. Constraints of flow rate primarily demands on configuration of air distributors. Particularly for the air with different temperature, velocity and pressure, an even distribution of air distributors is especially important. Air distributors containing one inlet and eleven outlets are connected with burners so that uniform flow rate of each outlet is required. Based on CFD (Computational Fluid Dynamics) method, temperature, velocity and pressure distribution in the air distributors are simulated. The results show that flow rate is sensitive to the rate of pressure and velocity change but not for temperature change. The maldistribution of each outlet cannot accord with engineering standard. So, it is necessary to take some methods to decrease the maldistribution of each outlet. The dampers exist at each outlet are controlled individually. Hence, the flow rate can be constrained by adjust pressure according to the proportion of maldistribution.

In this paper the Navier-stokes equations for a single liquid slug have been solved in order to predict the circulation patterns within the slug. Surface tension effects on the air-water interface have been investigated by solving the Young–Laplace equation. The calculated interface shape has been utilized to define the liquid slug geometry at the front and tail interfaces of the slug. Then the effects of the surface tension on the hydrodynamics of the two-phase slug flow have been compared to those where no surface tension forces exist. The importance of the complex flow field features in the vicinity of the two interfaces has been investigated by defining a non-dimensional form of the wall shear stress. The latter quantity has been formulated based on non-dimensional parameters in order to define a general Moody friction factor for typical two-phase slug flows in microchannels. Moreover, the hydrodynamics of slug flow formation has been examined using computational fluid dynamics (CFD). The volume-of-fluid (VOF) method has been applied to monitor the growth of the instability at the air-water interface. The lengths of the slugs have been correlated to the pressure fluctuations in the mixing region of the air and water streams at an axisymmetric T-junction. The main frequencies of the pressure fluctuations have been investigated using the Fast Fourier Transform (FFT) method.