Accepted Manuscripts

Ercan Dede, Yanghe Liu, Shailesh Joshi, Feng Zhou, Danny Lohan and Jong-Won Shin
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041440
Design optimization of a three-dimensional (3-D) heat flow structure for power electronics gate drive circuit thermal management is described. Optimization methods are described in the creation of several structural concepts targeted towards simultaneous temperature reduction of multiple gate drive integrated circuit (IC) devices. Each heat flow path concept is intended for seamless integration based on power electronics packaging space constraints, while maintaining required electrical isolation. The design synthesis and fabrication of a select concept prototype is presented along with the development of an experimental test bench for thermal performance characterization. Experimental results indicate a significant 45 degree C maximum temperature reduction for the gate drive IC devices in a laboratory environment, which translates to an estimated 41 degree C maximum temperature reduction under high temperature (~100 degree C) ambient conditions. The technical approach and design strategy is applicable to future wide band-gap (WBG) electronics packaging applications, where enhanced 3-D thermal routing is expected to be critical to maximizing volumetric power density.
TOPICS: Flow (Dynamics), Heat, Design, Electronics, Gates (Closures), Temperature, Optimization, Electronic packaging, Engineering prototypes, High temperature, Performance characterization, Power density, Circuits, Energy gap, Integrated circuits, Thermal management, Manufacturing
Harald H.-W. Funke, Nils Beckmann, Jan Keinz and Sylvester Abanteriba
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041495
The Dry-Low-NOx (DLN) Micromix combustion technology has been developed originally as a low emission alternative for industrial gas turbine combustors fueled with hydrogen. Currently the ongoing research process targets flexible fuel operation with hydrogen and syngas fuel. The non-premixed combustion process features jet-in-crossflow-mixing of fuel and oxidizer and combustion through multiple miniaturized flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. The paper presents the results of a numerical and experimental combustor test campaign. It is conducted as part of an integration study for a dual-fuel (H2 and H2/CO 90/10 Vol.%) Micromix combustion chamber prototype for application under full scale, pressurized gas turbine conditions in the auxiliary power unit Honeywell Garrett GTCP 36-300. In the presented experimental studies, the integration-optimized dual-fuel Micromix combustor geometry is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen and syngas fuel. The experimental investigations are supported by numerical combustion and flow simulations. For validation, the results of experimental exhaust gas analyses are applied. Despite the significantly differing fuel characteristics between pure hydrogen and hydrogen-rich syngas, the evaluated dual-fuel Micromix prototype shows a significant low NOx performance and high combustion efficiency. The combustor features an increased energy density that benefits manufacturing complexity and costs.
TOPICS: Fuels, Industrial gases, Combustion chambers, Turbines, Nitrogen oxides, Hydrogen, Combustion, Syngas, Flames, Emissions, Engineering prototypes, Flow simulation, Gas turbines, Atmospheric pressure, Manufacturing, Combustion technologies, Pressurized gas, Geometry, Exhaust systems, Density
Seham Shahid and Martin Agelin-Chaab
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041493
In this paper, the problem of air cooling and temperature non-uniformity at the cell and pack level is addressed. Passive techniques are developed by integrating jet inlets and vortex generators in a simple battery pack with the goal to achieve an effective cooling, and the desired temperature uniformity at the cell and pack level to less than 5 ºC, without an increase in the required mass flow and power requirements. Moreover, different configurations of the developed techniques are examined and compared. In order to achieve the objectives, computational fluid dynamics (CFD) is used to perform detailed simulations of the battery packs. The results concluded that by adding both the delta winglet vortex generator arrays and jet inlet arrays in the same configuration, significant improvements in cooling and temperature uniformity can be achieved. The results showed that the maximum temperature of the battery pack was reduced by ~6% and the temperature uniformity at the pack level was increased by 24%. Additionally, a ~37% improvement in the temperature uniformity at the cell level was achieved.
TOPICS: Cooling, Vortices, Generators, Temperature uniformity, Jets, Batteries, Computational fluid dynamics, Engineering simulation, Temperature nonunifomity, Simulation, Flow (Dynamics), Temperature
Ankush Tharkar and Shripad P. Mahulikar
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041492
The scope for the heat transfer enhancement in the tubular heat exchanger is high due to its unique property of having two separate convective heat transfer coefficients. The variation of diameter and annular space has a direct effect on the value of convective heat transfer coefficients due to their inverse relation. Thus, the strong emphasis has to be given on the influence of diameter and annular space on the thermal characteristics of the tubular heat exchanger. In this numerical analysis, peculiarities in the improvement of the performance parameters are studied with the variation in the value of inlet velocities of the fluids (cold and hot), inner pipe diameter and annular space for the combination of dimensional range such as macroscale and microscale range. The inner tube diameter is observed to be sensitive to the improvement in the performance parameter. The growth in performance parameter of the tubular micro heat exchanger is found to be higher when both the value of diameter and annular space is in the microscale range. Keywords: tubular micro heat exchanger, convective heat transfer coefficient, thermal characteristic, macroscale and microscale range
TOPICS: Heat exchangers, Microscale devices, Size effect, Convection, Heat transfer, Fluids, Numerical analysis, Pipes
Zhenping Wan, Xiaowu Wang, Shuiping Zou and Jun Deng
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041491
A novel stainless steel fiber sintered felt (SSFSF) with honeycombed channels (SSFSFHC) is a promising support for catalytic combustion of the volatile organic compounds. The SSFSFHC consists of stainless steel fiber, three-dimensionally reticulated porous structures and interconnected honeycombed channels. The equivalent thermal conductivity of the SSFSFHC is tested. It is found that the ETC of the SSFSFHC increases with the hot side temperature increasing but decreases with the porosity increasing and channel occupied area ratio increasing. The ETC of the SSFSFHC changes little with channel diameter increasing. The heat transfer model of the SSFSFHC is considered as parallel/ series combinations of relevant thermal resistances. In order to estimate the equivalent thermal conductivity of the SSFSFHC, the correlation of the ETC of the SSFSF is derived. The expressions of the axial temperature under different porosities are deduced when eliminating the radial heat transfer between the channel section and the SSFSF section. The relationships of the transferred heats and the corresponding resistances along the radial direction are obtained by assuming that the radial heat transfer can be simplified as a serial of heat resistances located between the channels and the SSFSF.
TOPICS: Fibers, Thermal conductivity, Stainless steel, Heat transfer, Temperature, Heat, Combustion, Organic compounds, Porosity
Ivana Fernandes de Sousa, Daduí Cordeiro Guerrieri, Carolina P. Naveira-Cotta and Manish Tiwari
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041439
This paper presents the experimental and theoretical analysis of a micro heat exchanger designed for the waste heat recovery from a high concentration photovoltaic (HCPV) system. A test bench was built to analyze the thermal behavior of a heat exchanger targeted to work in a similar condition of an existing HCPV panel. A high power heater was encapsulated inside a copper cartridge, covered by thermal insulation, leading to dissipated heat fluxes around 0.6 MW/m2, representative of the heat flux over the solar cell within the HCPV module. An infrared camera was used to non-intrusively measure the temperature field over the micro heat exchanger external surface, while thermocouples were placed at the contact between the heat exchanger and the heater, and at the water inlet and outlet ports. In the theoretical analysis, a hybrid numerical-analytical treatment is implemented, combining the numerical simulation through the COMSOL Multiphysics finite elements code for the micro-heat exchanger, and the analytical solution of a lumped-differential formulation for the electrical heater cartridge, offering a substantial computational cost reduction. Such computational simulations of the three-dimensional conjugated heat transfer problem were critically compared to the experimental results, and also permitted to inspect the adequacy of a theoretical correlation based on a simplified prescribed heat flux model without conjugation effects. It has been concluded that the conjugated heat transfer problem modeling should be adopted in future design and optimization tasks.
TOPICS: Heat exchangers, Theoretical analysis, Heat transfer, Heat, Heat flux, Temperature, Copper, Computer simulation, Heat recovery, Flux (Metallurgy), Simulation, Gates (Closures), Design, Engineering simulation, Finite element analysis, Thermal insulation, Thermocouples, Water, Modeling, Optimization, Solar cells
Gopala Krishna E D, Shaik Shamshoddin and Raghu Ande
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041341
A 3D transient numerical model of a ductile iron ladle has been developed to predictthe fluid flow and temperature drop during the holding and teeming. The volume of fluid (VOF) multiphase model has been employed to track the interface between the liquid metal and the air. The SST k-? model has been applied to model the turbulence due to natural convection in the ladle. The temperature evaluation in the refractory lining walls during preheating and teeming is shown. Appropriate boundary conditions are applied for natural convection and radiation to surroundings from all the outer steel surfaces as well as from the top glass wool cover. The heat loss due to radiation from the liquid metal surface to the surrounding walls is also considered in the present model by applying an energy sink term to the cells at the interface. The numerical results of the 780 Kg ladle have been compared with the measured temperature drop of the metal using an S-type thermocouple for two ladle cycles and the difference between the measured and predicted temperature at the end of two cycles is 3 0C. Decreasing the ladle capacity to 650 Kg for pouring the same amount of metal increased the temperature drop by 11 0C due to increase in surface area to melt volume ratio. Also increasing the refractory thickness for 650 Kg ladle increased the temperature drop by 4 0C due to the heat accumulation in the ladle during the cyclic transient heat transfer process.
TOPICS: Fluid dynamics, Heat transfer, Computer simulation, Nodular iron, Foundry ladles, Temperature, Natural convection, Liquid metals, Cycles, Metals, Radiation (Physics), Turbulence, Steel, Glass, Fluids, Heat, Heat losses, Thermocouples, Transient heat transfer, Linings (Textiles), Transients (Dynamics), Boundary-value problems
Xing Yang, Zhao LIU, Zhansheng Liu, Terrence Simon and Zhenping FENG
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041342
Effects of an upstream combustor wall on turbine nozzle endwall film cooling performance are numerically examined in a linear cascade in this paper. Film cooling is by two rows of cooling holes at 20% of the axial chord length upstream of the vane leading edge plane. The combustor walls are modeled as flat plates with square trailing edges positioned upstream of the endwall film cooling holes. A combustor wall is in line with the leading edge of every second vane. The influence of the combustor wall, when shifted in the axial and tangential directions, is investigated to determine effects on passage endwall cooling for three representative film cooling blowing ratios. The results show how shed vortices from the combustor wall greatly alter the flowfield near the cooling holes and inside the vane passage. Film cooling distribution patterns, particularly in the entry region and along the pressure side of the passage are affected. The combustor wall leads to an imbalance in film cooling distribution over the endwalls for adjacent vane passages. Results show a larger effect of tangential shift of the combustor wall on endwall cooling effectiveness than the effect of an equal axial shift. The study provides guidance regarding design of combustor-to-turbine transition ducts.
TOPICS: Combustion chambers, Film cooling, Guide vanes, Cooling, Turbines, Vortices, Ducts, Flat plates, Chords (Trusses), Design, Nozzles, Cascades (Fluid dynamics), Pressure
Pedram Bigdelou, Fathollah Pourfayaz and Younes Noorollahi
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041344
We investigate the effect of soil type and moisture on the operation of a ground source heat pump system in supplying the energy needs of a greenhouse in Karaj, Alborz province, Iran in terms of the required length of ground heat exchanger, the working hours, the electricity consumption, as well as the COP of heat pumps. In order to predict the capacity of heat pumps, governing equations of heat transfer in the ground heat exchanger are numerically solved through a finite difference method. Thermal properties of various soil types, namely sandy soil, sand, silty loam, and silty clay, with three different levels of moisture content referred to as dry, damp, and saturated, are considered as the main inputs for the computer code. The simulations indicate that when moisture is increased from dampness to saturation, the annual working hours of heat pumps decrease by 1.1%, 5.1%, 6.1%, and 4.6%, and the their annual electricity consumption is reduced by 2.2%, 10.6%, 12.6%, and 9.7% for sandy soil, sand, silty loam, and silty clay, respectively. Moreover, the average COP of heat pumps increase by 0.9%, 4.0%, 5.2%, and 3.7% in heating mode and 2.4%, 13.0%, 16.5%, 11.7% in cooling mode for the mentioned soils, respectively.
TOPICS: Heat pumps, Soil, Sands, Heat exchangers, Computers, Finite difference methods, Heat transfer, Cooling, Simulation, Thermal properties, Engineering simulation, Heating
yuanlong Wang, Abdalkaleg Hamad and Mohsen Tadi
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041343
This note is concerned with the evaluation of the unknown diffusion coefficient in a steady-state heat conduction problem. The proposed method is iterative and, starting with an initial guess, updates the assumed value at every iteration. The updating stage is achieved by generating a set of functions that satisfy "some" of the required boundary conditions. The correction to the assumed value is then computed by imposing the "remaining" boundary conditions. Numerical examples are used to study the applicability of this method.
TOPICS: Diffusion (Physics), Boundary-value problems, Steady state, Heat conduction
Mohammad Zia Zahedi and Ires Iskender
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041345
In this study, a losses analysis at bushing regions of a transformer covers is done using Finite Difference(FD) Method(FDM), considering that FDM being more flexible to deal with the nonlinear constitutive law and easier to be implemented than Finite Element(FE) and analytical methods. The analysis is performed based on a 2-level adaptive mesh solution of Maxwell equations and ohm law at the cross section area in axial symmetric page of a steel disk, taking account the non-linear magnetic permeability of the steel. The losses density obtained, as a heat source, is imported into an Alternating Direction Implicit (ADI) approach of heat conduction equation. Therefore, a FD solution algorithm for magneto-thermal analysis on cover plate is obtained by combination of Adaptive Mesh Refinement (AMR) and ADI-FDM, which improves the accuracy and decreases the computational time without losing accuracy. The reliability of the proposed technique is confirmed by experimental and FE Method (FEM) results, considering the temperature distribution of the cover. The comparison of the results with those obtained from FEM and experiments shows the efficiency and capability of the method.
TOPICS: Density, Heat, Permeability, Steel, Bushings, Heat conduction, Reliability, Maxwell equations, Finite element methods, Algorithms, Analytical methods, Constitutive equations, Finite element analysis, Disks, Finite element model, Temperature distribution, Thermal analysis
Toshihiko Shakouchi, Yusuke Matsumoto, Koichi Tsujimoto and Toshitake Ando
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041347
Heat exchanger is used widely in many fields, and various kinds of exchanger have been developed according to the practical application. But, recently heat exchanger with a high efficient or compact more is desired from the viewpoint of energy conservation, and has been developed new one such as a fin tube type compact one, a double tube type one having the inner pipe with a special geometry, and others. In this study, the flow and heat transfer characteristics of petal-shaped double tube with a large wetted perimeter of 6 and 5 petals and 5 shallow petals, and the effect of tube shape on the heat transfer and heat transfer efficiency are examined experimentally. The heat transfer of double tube with a petal shaped inner tube will be increased because of the large wetted perimeter, but the pressure loss by friction will be increased. The optimum shape of petal shaped double tube having a high heat transfer performance, efficiency, most will be shown.
TOPICS: Heat, Heat exchangers, Shapes, Heat transfer, Energy conservation, Pressure, Flow (Dynamics), Friction, Pipes, Geometry
Muhammad Ansab Ali, Tariq Khan, Ebrahim Al Hajri and Fadi Khasawneh
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041346
The present work demonstrates the use of manifold microchannel technology in conjunction with conventional macro geometries to achieve superior performance compared to traditional heat exchangers. A novel tubular manifold heat exchanger is designed using 3D printed manifold and conventional double enhanced tube. The experiments are performed using water as the working fluid and the manifold side heat transfer coefficient up to 9538 Wm-2K-1 with a low flow rate of 4.25 lpm is achieved with as low pressure drop as 323 Pa. A comparison with respect to thermal hydraulic performance of the results with a plate heat exchanger shows clear advantage of the proposed exchanger. Overall, microscale heat transfer characteristics are obtained by using relatively simple and economical fabrication techniques.
TOPICS: Heat exchangers, Manifolds, Performance evaluation, Pressure drop, Water, Microchannels, Heat transfer coefficients, Additive manufacturing, Microscale heat transfer, Flow (Dynamics), Fluids, Manufacturing
Adib Bazgir
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041348
The vortex tube is a mechanical device with no moving parts that can separate a compressed gas into a hot and a cold stream. Pressurized gas is injected tangentially into a swirl chamber and accelerated to a high rate of rotation. This gas motion creates a cold core and a hot shell. In certain engineering applications such as gas drilling, the use of a high flow-rate air with high pressure and low temperature can improve process efficiency. In these applications, demand for the cold air stream as high as 40 kg/s is not uncommon. In this paper, the use of a vortex tube bundle for generating this large flow-rate of the cold air stream is proposed and evaluated, using numerical simulations. A single commercially available vortex tube can only produce a cold air stream up to 0.008 kg/s. Thus it will take 5,000 such vortex tubes to reach the required flow rate of 40 kg/s. Space limitation, as well as assembly difficulty, makes such an approach unrealistic. The objective of this work is to design a custom-made vortex tube so that a minimum number of such tubes can be used to meet the performance requirement posted by these applications. In this study, computational fluid dynamics is used to analyze the flow field, temperature field and pressure field, and to optimize the vortex tube parameters so that a specific set of desired output can be achieved to meet the application requirements.
TOPICS: Drilling, Optimization, Vortices, Cooling, Flow (Dynamics), Temperature, Pressure, Rotation, High pressure (Physics), Computational fluid dynamics, Design, Engineering systems and industry applications, Low temperature, Computer simulation, Manufacturing, Pressurized gas, Shells
Kazi M. Rahman, Dr. M. Ruhul Amin and Ahsan Mian
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041349
In the field of additive manufacturing process, laser cladding is widely considered due to its cost effectiveness, small localized heat generation and full fusion to metals. Introducing nanoparticles with cladding metals produces metal matrix nanocomposites which in turn improves the material characteristics of the clad layer. The governing equations that control the fluid flow are standard incompressible Navier-Stokes and heat diffusion equation whereas the Euler-Lagrange approach has been considered for particle tracking. The mathematical formulation for solidification is adopted based on enthalpy porosity method. Liquid titanium has been considered as the initial condition where particle distribution has been assumed uniform throughout the geometry. A numerical model implemented in a commercial software based on control volume method has been developed that allows to simulate the fluid flow during solidification as well as tracking nanoparticles during this process. A detailed parametric study has been conducted by changing the Marangoni number, convection heat transfer coefficient, constant temperature below the melting point of titanium and insulated boundary conditions to analyze the behavior of the nanoparticle movement. The influence of increase in Marangoni number results in a higher concentration of nanoparticles in some portions of the geometry and lack of nanoparticles in rest of the geometry. The high concentration of nanoparticles decreases with a decrease in Marangoni number. Furthermore, an increase in the rate of solidification time limits the nanoparticle movement from its original position which results in different distribution patterns with respect to the solidification time.
TOPICS: Diffusion (Physics), Nanoparticles, Solidification, Geometry, Metals, Fluid dynamics, Cladding systems (Building), Particulate matter, Titanium, Additive manufacturing, Computer simulation, Convection, Heat, Temperature, Lasers, Melting point, Nanocomposites, Porosity, Thermal diffusion, Boundary-value problems, Computer software, Enthalpy
Kasem Ragab and Dr. Lamyaa El-Gabry
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041266
One of the approaches adopted to improve turbine efficiency and increase power to weight ratio is reducing vane count. In the current study, numerical analysis was performed for the heat transfer over the surface of nozzle guide vanes under the condition of reduced vane count using three dimensional computational fluid dynamics (CFD) models. The investigation has taken place in two stages: the baseline nonfilm-cooled nozzle guide vane, and the film-cooled nozzle guide vane. A finite volume based commercial code was used to build and analyze the CFD models. The investigated annular cascade has no heat transfer measurements available; hence in order to validate the CFD models against experimental data, two standalone studies were carried out on the NASA C3X vanes, one on the nonfilm-cooled C3X vane and the other on the film-cooled C3X vane. Different modelling parameters were investigated including turbulence models in order to obtain good agreement with the C3X experimental data, the same parameters were used afterwards to model the industrial nozzle guide vanes.
TOPICS: Cascades (Fluid dynamics), Heat transfer, Nozzle guide vanes, Computational fluid dynamics, Modeling, Numerical analysis, Turbines, NASA, Weight (Mass), Turbulence
Shirin Niroomand, Melanie Fauchoux and Carey J. Simonson
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4040989
This paper presents an experimental study on frost formation on a plate under natural convection conditions. Frost thickness, mass, density and surface roughness are measured during each test. Frost thickness and roughness are measured using an image processing technique. The effect of operating conditions (temperature of the plate, and temperature and relative humidity of the air) on the properties of frost are investigated. Frost surface roughness is quantified using two parameters; the average roughness and the skewness of the roughness, which can describe the frost layer shape. The surface roughness of the frost layer is considerably higher than the roughness of a flat plate, which should be considered in frosting studies. In this paper, it is shown that frost surface roughness is related to the frost layer shape, porosity and density. It is also found that the plate temperature affects the frost surface roughness significantly; as the plate temperature decreases, the frost layer has a high average roughness and negative skewness, which correspond to a highly porous, low density frost layer. Increasing the air humidity and air temperature affects the average surface roughness slightly but not skewness of the frost surface.
TOPICS: Natural convection, Experimental characterization, Surface roughness, Temperature, Density, Shapes, Flat plates, Image processing, Porosity
Mohsen Ali Mandegari, Somayeh Farzad and Hassan Pahlavanzadeh
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4032332
TOPICS: Exergy, Optimization, Wheels

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