The hot wire chemical vapor deposition method was applied for fabrication of hydrophobic fluoropolymer coatings on the surface of tubular heaters. The effect of hydrophobic surfaces (with static contact angle of 125°) on the local and integral heat transfer characteristics was studied during boiling of saturated water at atmospheric pressure, including high speed visualization. The heat transfer enhancement

Three-dimensional numerical simulations are conducted to calculate the surface heat transfer coefficient (HTC) of the water jet impinging on a TA2/Q235B clad plate. The accuracy of the simulation model is validated by experiment. The simulation results are basically in agreement with the experimental results. The effect of clad plate temperature and thickness, jet height, orifice diameter, and orifice

Many experimental and numerical investigations of arrays of impingement cooling jets have been performed. A lot of them have addressed the problem of cooling with jets directed perpendicularly or inclined to the planar plate. However, in many technical applications contour of the cooled surface is more complex. One of the examples is a casing of the low-pressure turbine of the jet engine. It’s shape

Threshold crude oil fouling models use activation energy in the deposition rate term to predict the initial fouling rates. It has been reported in the literature that fluid velocity has a strong influence on activation energy, which does not agree well with the principles of chemical reaction engineering. Besides, the existing threshold fouling models always predict an increase in the fouling rate

Numerical simulations were carried out to investigate the swirling decaying flow generated by a novel axial guide vane swirler with profiled blades and no supporting device in a tube and its effect on heat transfer and pressure drop compared to a developed turbulent flow in a no swirl tube. Reynolds number ranged from 10,000 to 200,000. Turbulence was modelled using a k−ω Shear Stress Transport model

Film cooling using coolant jets is effective for increasing the cooling effectiveness of turbines. In the present study, large eddy simulation was employed for predicting small-scale vortices in the film-cooling process with different blowing ratios (BRs). The counter-rotating vortex pair (CRVP) was compared with the hairpin vortex, and results indicated the CRVP was the cross section of hairpin vortex

The present work numerically studied the enhanced heat transfer mechanism of the coupled fields of detached and spiral vortices in symmetrical and asymmetrical spirally corrugated tubes. The heat transfer and viscous dissipation were analyzed by evaluating the entropy combined with the flow patterns, and the global entropy generation rate was analyzed by considering the local Nusselt number and friction

Utilizing energy efficiently could greatly relieve current energy crisis. Therefore, in this article, a simple supercritical CO2 Brayton cycle for waste heat recovery from gas turbine is presented. The system uses ambient air as its cold source, which is more convenient and economic. Considering temperature difference between heat source and turbine inlet, it is of great significance to research the

As a new type of cone flowmeter, the bi-directional cone flowmeter is a promising device for metering the cryogenic fluid due to its excellent advantages. This work presents a numerical study on the cavitating flow characteristics of liquid nitrogen in the bi-directional cone flowmeters based on a modified cavitation model with thermal effects. The influences of some factors, including operating conditions

Piezoelectric fan driven forced convection is investigated with a three-dimensional numerical model by employing a dynamic mesh technique for varying fin-array width with increasing number of fins. Two different types of boundary settings have been tested. In the boundary setting-I, a fixed heat flux value distributed uniformly among the fins, whereas a constant heat flux is applied to the base of

The results of an experimental study of the influence of longitudinal positive and negative pressure gradients in a rectangular flat channel with a backward-facing step on turbulent heat transfer in the zones of separation, attachment and relaxation of the flow are presented. The studies were carried out in a turbulent flow regime at Reynolds numbers 4 × 103–1.2×104. The height of the step was equal

Leidenfrost (LF) and rewetting (RWT) phenomenon are both closely related and involved for the cooling of a very hot object utilizing a suitable cooling agent. The present study focusses on the influence of different parameters on both LF and RWT phenomenon of vertical tubes by bottom flooding. The various parameters primarily include the quantity or injection rate of the coolant (CLNT), type of CLNT

In this paper, numerical simulation is performed to predict combined impingement and film cooling on a model of the turbine blade leading edge by the heat flow coupling method. The first stage rotor blade leading edge of the GE-E3 engine high pressure turbine is adopted for the simulation. The relative performances of turbulence models are compared with experimental data and the results show that standard

Microwave has been widely used in pyrolysis of waste lubricating oil, but the uneven electromagnetic field distribution seriously affects the product distribution and even aggravates coking in pyrolysis process, where the pyrolizer structure plays a dominant role. Four structures were simulated in the continuous pyrolysis of waste lubricating oil under microwave irradiation, including single circular

Selected Papers from the 5th International Workshop on Heat/Mass Transfer Advances for Energy Conservation and Pollution Control (IWHT2019). Heat Transfer Engineering. Accepted .

Mixed convection flow in a lid-driven cavity in the presence of a uniform partial magnetic field is investigated utilizing the pseudo spectral method based on polyharmonic spline radial basis functions. The two-dimensional problem is concerned in a unit square cavity designed by adiabatic horizontal walls and vertical walls with constant temperatures. The top wall moves either in the positive x or

The three-dimensional transient heat transfer analysis of multilayer functionally graded graphene platelets reinforced composite (FG-GPLRC) truncated conical shells subjected to asymmetric thermal shock is presented. In order to include the effect of finite heat wave speed, the non-Fourier heat conduction law is employed. The multilayer FG-GPLRC truncated conical shells are composed of perfectly bonded

This paper presents a novel approach to visualize the flow boiling in round tubes under “diabatic conditions”. In the visualization test section, a 3D printed round tube is placed inside a glass tube with secondary fluid at a higher temperature flowing in the annulus between the two tubes thus providing diabatic conditions. Experimental work was conducted for evaporating R410A flow in a horizontal

Ammonia (NH3) is attracting attention as a carbon-free fuel that does not emit carbon dioxide, but there is concern that a large amount of nitrogen oxides is emitted during its combustion. The mixtures of NH3 and city gas are used as fuels, and the effectiveness of Moderate or Intense Low-oxygen Dilution (MILD) combustion to reduce nitric oxide (NO) emissions is investigated through zero-dimensional

(2020). Selected Papers from the 5th International Conference on Polygeneration (ICP 2019). Heat Transfer Engineering. Ahead of Print.

Numerical optimization of heat and fluid flow over staggered tube banks are investigated for both unfinned and axially finned tube banks. Ansys Fluent software is utilized for numerical computations. To find maximum total heat transfer and minimum volume of tube bank for the given mass flow rate, allowable pressure drop and tube bank effectiveness; A Multi-objective Genetic Algorithm II is used. Optimum

This paper presents the influence of zigzag ribs placed on an air heater section of a force convective cabinet dryer on thermal, and fluid flow behaviors in the air heater section and temperature distribution in a cabinet dryer section. The experimental study was carried out in simulated conditions: a uniform absorbed thermal energy and an inlet air velocity under forced convection in the Reynolds

Nanofluid preparation and its deposition on metallic surfaces are in wide practice due to their enhancement capability in the pool boiling heat transfer. The effect of zirconia nanoparticles coated layer on pool boiling heat transfer has been investigated with de-ionized water. The turbidity, viscosity and stability test are conducted, and confirmed a better dispersion of nanoparticles. The synthesized

The present study involves the use of dip nanocoating, one of the passive techniques by the modification of the heater surface to understand the behavior of pool boiling heat transfer characteristics at atmospheric pressure using deionized water and Graphene- Poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) as a working fluid and coating material. The copper specimen is coated with the mentioned

In this study, the cooling and dehumidification performance of a photovoltaic powered thermoelectric air conditioning system is investigated under tropical climate. The system is first investigated under a controlled environment with different flow arrangements of the hot junction cooling air stream. Better temperature reduction was observed when the cross-flow arrangement is used. Besides, it delivered

Thermosyphon based evacuated tube solar collectors have seen exponential growth in the last few decades for domestic hot water applications. The output temperatures of such collectors can be increased by integrating evacuated tube receivers with compound parabolic concentrators (CPCs) to meet many industrial heat loads. This paper presents a new concept of increasing concentration of solar radiation

In humid climates, due to high relative humidity present in the ambient air, traditional air drying system is becoming inefficient for drying the agricultural/food products. On the other hand, there is a scarcity of useful drinking water in many parts of the world. In order to meet the aforementioned requirements, a novel multipurpose liquid desiccant drying/desalination system has been proposed in

Water scarcity is the biggest survival challenge for the current generation, and atmospheric water condensation can be a solution. This paper presents the results of a numerical and experimental evaluation of a novel thermoelectric air duct dehumidifier system (TE-ADD) installed on a test chamber. The subject system, made of twenty-four thermoelectric modules along with heat sinks and fans, was used

Metal-organic frameworks (MOFs) are emerging as potential adsorbents for adsorption based systems intended for various applications. Aluminum fumarate is one of the promising MOFs for being used as an adsorbent for water-based adsorption heat pumps. Though there have been a lot of studies regarding water adsorption characterization of aluminum fumarate, there is hardly any literature addressing the

Thermal energy storage has a potential future to store renewable energy. Thermochemical energy storage (TCES) is the most promising and possesses more advantages over sensible and latent heat thermal storage systems such as higher energy storage density and ambient temperature storage. The major concern at this time for TCES is to find the material or combination of materials which can be thermally

Countermeasures for global warming have been promoted internationally. Heat pump cycles that utilise refrigerants with high global warming potential values are required to adopt the next generation refrigerants to conform to the revised Montreal Protocol. Refrigerants R410A is commonly used in the room air conditioners while it has been substituted with HFC32 in Japan; yet their global warming potential

As the use of semiconductors in industrial site increases, research on ultra-low refrigerators is required to increase the life and quality of the semiconductors. While various types of refrigerators exist, Joule–Thomson refrigeration with the mixed refrigerant is preferred because of its compactness and stability. The performance of Joule–Thomson refrigeration with mixed refrigerants is based on the

The urge to replace hydrofluorocarbons which possess high global warming potentials has taken center stage in the air conditioning industry due to both international and local policies such as the Kigali Amendment and Japan’s revised Fluorinated Gas law. This has prompted the exploration of novel refrigerants as well as their mixtures to create high performance environmentally friendly alternatives

Experimental study on using nanofluid in a cross-flow minichannel heat exchanger (MICHX) to investigate its transient behavior was completed. Step changes of temperature and flow rate in the hot liquid were applied and the dynamic performance of the heat exchanger was analyzed. Results of nanofluid were compared to water and demonstrate an enhancement of 19% in heat transfer when using 2.5 wt% concentration

The effect of non-uniform magnetic field on forced convection heat transfer of ferrofluids in flattened tubes has been investigated numerically using two-phase mixture model. The equilibrium magnetization for the ferrofluids is considered, and the linear relationship of magnetization with applied magnetic field intensity is assumed to relax. The main goal of the current research is to study the effect

Advances in manufacturing technologies and the recent explosion of materials and methods for creating additively manufactured devices has opened new avenues for novel heat sink designs that can be optimized for flow and conduction considerations. This review paper highlights many of the recent successes and challenges associated with the utilization of “3 D printed” heat sinks for applications in electronics

The thermal efficiency of the modified Trombe-wall system proposed in this work is improved compared to its conventional version thanks to the adjunction of a porous material to the absorber wall. Thermal measurements were made in a wide Rayleigh number range, with high values reaching 4.52 × 109. The ratio between the matrix’s thermal conductivity of the porous material and that of the air varies

The systematic experimental investigation of the viscosity of more than 30 different nanofluids was carried out. The investigated nanofluids were prepared based on distilled water, ethylene glycol and engine oil containing nanoparticles Al2O3, TiO2, ZrO2, CuO, Fe2O3, and Fe3O4, as well as nanodiamonds. The nanoparticle volume concentration ranged from 0.25 to 8%. The size of nanoparticles varied from

The swirling flow is used to increase mixing and decrease nitrogen oxide emission in the combustor. Meanwhile, the swirling incoming flow has a significant effect on both aerodynamic and heat transfer characteristics of the downstream first-stage turbine. This paper conducts a numerical investigation on the influences of the inlet swirl core on the film cooling performance of a leading-edge model.

The heat and mass transfer characteristics of a micropolar nanofluid-filled cubic cavity are investigated with different types of nanoparticles (Al2O3, TiO2, Cu and Ag). Pure water is assumed as the base fluid. The governing equations are simplified by means of vorticity-vector potential formulation and subsequently solved numerically using the finite volume method. The influences of relevant parameters

The non-Fourier dual-phase-lag heat model has been solved as a well-known accurate bioheat model to compute the temperature distribution in a three-dimensional multilayered skin of the human finger including the embedded vessels. A novel conjugate solver over the platform of OpenFOAM codes has been developed. Three types of vessels that are representor of the capillaries, the small arteries, and the

Examining non-rarefaction effects in laminar micro-convective low subsonic (with negligible compressibility effects) gas flows is as important as the well-explored rarefaction effects. This study numerically analyzes one of the important non-rarefaction effects arising from steep density variations due to the steep temperature-gradients, in micro-convective air-flow. For the constant wall heat flux

In this study, a cooling radiator developed specifically for unmanned aerial vehicles was analyzed using computational fluid dynamics (CFD). The radiator consisted of turbulator pins (core side) placed between two vertical columns (column side). While the air passes from the core side, the cooling fluid takes place between two streams on the column side. CFD modeling of the radiator, which was developed

Channels not receiving the same amount of flow (flow maldistribution) is an important effectiveness loss for high effectiveness heat exchangers. This paper develops a finite difference model of a counter flow heat exchanger. It reproduced the simple NTU result for two channels exactly. For more than two channels, there is an edge effect, and the model agreed within 0.1% of the literature. Perfect agreement

This paper presents the creation of three-dimensional (3D) maps for selection of best Colebrook friction factor approximation. Twenty Colebrook approximations are observed in range of Reynolds numbers between 4000 and 108 and relative surface roughness less than 0.05. Colebrook approximations with the lowest relative errors at various combinations of Reynolds numbers and relative surface roughness

This paper proposes a numerical model of wicked heat pipes using a lumped parameter network. A lumped parameter network of a screen mesh wicked heat pipe is developed for the solid and fluid regions. Nodal analysis is applied to each node using the principles of conservation of mass, momentum, and energy. The resulting system of differential equations is solved using numerical integration. The lumped

In this study, the thermal and hydraulic performances of six different printed circuit heat exchanger (PCHE) configurations with supercritical liquefied natural gas as the working fluid are studied by a numerical method. Firstly, the thermal and hydraulic performances of the PCHE with airfoil fins are investigated at different operating pressures, which indicate that the PCHE with airfoil fins has

In this study, the effect of lubricating oil on the heat transfer characteristics of R600a condensing flow inside a horizontal micro-fin tube is experimentally investigated. The results are presented in three parts, including the characteristics of pure R600a condensation inside a smooth tube, the impact of using a micro-fin tube, and the effect of adding lubricating oil on the condensing heat transfer

This paper expounds the effect of horizontal spacing between two horizontally aligned circular cylinders on laminar natural convection to non-Newtonian power-law fluids. Numerical computations have been carried out for the following range of conditions: Grashof number (10 to 105), Prandtl number (0.71 to 100), horizontal spacing (0 to 20 times the cylinder diameter), and power-law index (0.4 to 1.6)

This study investigated the thermal performance of ultra-thin heat pipes (UTHPs). The total thickness of the heat pipe was 1 mm and the novel wick structure was copper braids modified to be superhydrophilic with higher capillary ability. This paper is divided into three parts, each focusing on the effect on the heat transfer performance of UTHPs, including the wettability of the wick, the filling ratio

Increasing attention has been paid to the flow and heat transfer in annular channels since their intensive applications in engineering. In this study, evaporation of the outer surface of two enhanced heat transfer tubes (2EHT) was compared to the performance of a smooth surface copper tube through experimental research. The refrigerant flowed in an annular space between the outer tube and the test

Printed circuit heat exchanger (PCHE) is a promising candidate of coolers used for SCO2 Brayton cycle. The thermal-hydraulic performance of SCO2 in a PCHE depends on the PCHE structure as well as the operating conditions of SCO2 due to its dramatic variation of thermal physical properties near the pseudo-critical point. This work experimentally investigated the thermal-hydraulic characteristics of

Accumulation of ice particles inside the pipes of an ice slurry refrigeration system is a problem that should be avoided to ensure the efficient performance of the system. In the present research, the swirling flow of ice slurry is numerically investigated using the Eulerian-Eulerian model coupled with the kinetic theory of granular flow. The swirling flow is generated by twisted tapes inserted into

Heat transfer induced by combined surface radiation and laminar natural convection in an open square cavity heated by three identical isothermal heat sources is studied numerically by using the multirelaxation time scheme of the lattice Boltzmann method. The working fluid is air. The heat sources, separated by adiabatic segments, are mounted on a vertical wall facing the aperture of the cavity and

The water permeability, form drag coefficient and heat transfer coefficient of porous copper samples manufactured by the Lost Carbonate Sintering process were measured and analyzed. The permeability increased and the form drag coefficient decreased with increasing porosity and decreasing pore size. There existed an empirical relationship between the form drag coefficient and the permeability. The highest

Heat transfer to an oscillating vertical annular flow through a porous material is investigated experimentally. The flow media includes stationary stainless steel wool filter and monoethylene glycol (which is known as a coolant, heat transfer agent or antifreeze) as the working fluid. Reciprocating forced oscillations are imposed on the single-phase monoethylene glycol via a frequency controlled dc

The liquid flow and heat transfer performance in rectangular channels with winglets are determined numerically in the Reynolds number range of 100 to 300. Water with constant thermophysical properties is used as the working fluid and modeled to be Newtonian. Three-dimensional numerical simulations have been performed on a rectangular plain channel and a rectangular channel with five pairs of winglets

In this study, in-tube condensation was conducted for mass fluxes of 100, 75 and 50 kg/m2s, and temperature differences of 1, 3, 5, 8 and 10 °C. Measurements and flow regimes were captured at various mean vapor qualities between 0.1 and 0.9 inside an inclined smooth tube with an inside diameter of 8.38 mm and 1.49 m long. Fifteen distinct inclination angles from -90° to 90° were considered while the

Laminar natural convection in unconfined power-law fluids from two attached horizontal cylinders has been investigated numerically to elucidate the non-Newtonian behavior of the fluid over a wide range of pertinent parameters: Grashof number (10 to 105), Prandtl number (0.71 to 100), and power-law index (0.2 to1.8). The heat transfer characteristics are elucidated in terms of isotherms, local Nusselt

Nanofluids are suspensions of ultra-fine nanoparticles or tubes resulting in the nanofluids having thermal conductivities significantly higher than those of the conventional base fluid alone. The purpose of this study is to evaluate the thermo-physical properties, including thermal conductivity, viscosity, electrical conductivity and above all, convective heat transfer coefficient, of de-aggregated