In the multi-effect evaporator (MED), the seawater falls on the outside of the tube, and the heat is transmitted from the steam flowing inside the tube. As a result, part of seawater evaporates and vapor is generated. Vapor flows in either co-current direction, cross direction or combination of both. The vapor flow exerts external force on falling film and affects film hydrodynamics, heat and mass

The large, complex batteries that are increasingly used in applications such as electric vehicles generate heat. As such, they require thermal management systems that can predict this heat generation. In this study, an electric-thermal coupled model was established to predict the temperature evolution of an air-cooled battery pack comprising three parallel branches with four cells in each branch. The

The present paper investigates how the cross–sectional shape of a vertical porous cylinder affects the onset of thermoconvective instability of the Rayleigh–Bénard type. The fluid saturating the porous medium is assumed to be a non–Newtonian power–law fluid. A linear stability analysis of the vertical thorughflow is carried out. Three special shapes of the cylinder cross–section are analysed: square

In this paper, an industrial-scale experiment with ten testing heat exchangers is conducted to study the influences of structures and working conditions on the tube-side heat transfer and flow characteristics of spiral-wound heat exchangers. The experimental results show that, with the increase of the winding angle, the tube-side heat transfer coefficients increase because of the enhanced secondary

The main challenge ahead of widespread application of renewable energy sources is their availability intermittence preventing continuous power supply. In order to circumvent the temporal mismatch between their supply and demand, thermal energy storage systems can be utilized. In this study, a compact spiral coil thermal storage unit was investigated to analyze the impact of operating parameters such

Additive manufacturing is a promising candidate to eliminate design constraints in thermal-fluid engineering problems as it enables optimized free-form designs to be produced. The brute force optimization needs too many experiments and/or analyses to obtain an optimized design. However, the same engineering design can be achieved by fewer experiments by using design of experiment (DOE) methodology

The research on working fluids of refrigerant/absorbent mixture is important for the development of the absorption refrigeration area. R290/POE-oil mixture is a new potential working fluid, in which R290 (propane) is the refrigerant and POE oil is the absorbent. This refrigerant/oil working fluid has a wide operating range, low generation temperature, and no corrosion to metals. Flow boiling heat transfer

Three-dimensional study of convection-radiation heat transfer of a discrete heat source (chip) inside an enclosure cooled by rectangular finned heat sink is studied. Conduction heat transfer through the enclosure walls and radiation exchange between these walls are considered. Convection heat transfer on the outer surfaces of the enclosure to the ambient is considered. A complete three-dimensional

Ceiling beams, such as smoke screens, supporting beams, and ceiling pipelines, exist in several types of tunnels. The ceiling structure of a tunnel has a significant influence on smoke propagation. This study determines the critical velocity required to control fire smoke in a tunnel with a ceiling beam. We conducted model experiments and numerical simulations to analyze the effects of a ceiling beam

In this work, a modeling approach is developed to cope with the phase-change problems having deviations from equilibrium conditions. The mathematical model is based on continuity and enthalpy conservation equations. The core of the model is a source term of continuity which governs the rate of phase change. The formulation of the source term is originally proposed with an infinite series, i.e. an iterative

Numerical study has been carried out to examine the heat transfer and fluid flow characteristics of open microchannel heat sinks consist of square pin fins. Variation of fin height evolves an open configuration of microchannel having open space available between fin top surface and top wall of the heat sink. Comparative analysis has been done amongst seven different heat sinks of varying fin height

The study numerically investigated the instability characteristics of a 3D highly separated natural convection flow developing within a cold cubic enclosure in the presence of a tandem of hot and cold horizontally aligned cylinders. The immersed boundary (IB) method was utilized to enforce kinematic no-slip and thermal boundary conditions on the surfaces of the two cylinders. The obtained results were

Compartment fire is a hazardous phenomenon because of the generated poisonous and high-temperature gases. Air curtain systems can be used in order to control the fire spread. This paper examines the numerical simulation method with a focus on the combustion model which can model the poisonous gases and investigates the effect of air curtain on fire. The results of the flamelet generated manifold (FGM)

This paper deals with thermosolutal convection in an inclined enclosure inserted with heat-generating porous blocks under the influence of magnetic field. The general Brinkman-extended Darcy model is adopted to formulate the fluid flow in the enclosure. An extensive series of numerical simulations is investigated in the range of parameters 0 ≤ Ha ≤ 150, 103 ≤ Ra ≤ 107, −10.0 ≤ N ≤ 10.0, 10−9 ≤ Da ≤

Laminarization of a turbulent flow due to wall heating has been known for more than 50 years, to the point that it is sometimes used as means of reducing friction. However this phenomenon has been mainly studied for cylindrical pipes and with imposed heat flux but not for channel flows and with imposed temperature boundary conditions, especially with asymmetric ones (that is to say in presence of a

Phase-change materials (PCMs) have attracted numerous attentions in thermal energy storage area due to their high latent heat capacity. However, their inherently low thermal conductivity and potential leakage risk severely decrease the thermal storage efficiency. In this study, thermally-enhanced nanoencapsulated phase change materials (NEPCMs) were proposed to overcome those limitations. Through a

A series of experiments on water droplet interaction with high-temperature peanut oil were conducted and the effects of droplet diameter and oil temperature were discussed in the current study. Three typical regimes, including secondary jet, bubble and vapor explosion were observed during the impact process. Especially, water vapor explosion can be induced by solid-liquid contact (Toil≥241 °C) and

Three types of helical microtube coil namely circle, oval and elliptical are introduced and evaluated both experimentally and numerically. Al2O3-water, ZnO-water at three volume fractions (ϕ) of 1.0%, 1.5% and 2% are considered as working fluid as well as the base fluid (water). Different values of pitch are tested with constant pitch/diameter ratio of 1 for all geometries. The numerical simulations

The accurate prediction of rod bundle critical heat flux (CHF) is an important task for thermal-hydraulic design of pressurized water reactor (PWR) core. Under normal and transient conditions of PWR, based on the two-phase flow pattern, there are different CHF regimes. In order to correctly distinguish the CHF regimes in rod bundle, it is necessary to analytical investigate rod bundle CHF-regime criterion

An appropriate evaluation of thermal characteristics in biological bodies under the influence of external heat source during the hyperthermia therapy is inherently difficult, since living tissues have a non-uniform and non-homogeneous structure composed of solid-liquid interfaces. In general, biological bodies are very sensitive to temperature alteration as it leads to a drastic change of protein structures

In micro-channel gas flows, velocity slip and temperature jump must be applied at the fluid/solid interface to take the thermodynamic non-equilibrium into account in the vicinity of the wall. In this work, simulations at molecular scale have been carried out and shown a jump in the conduction heat flux, in agreement with the boundary condition proposed by Maslen (1958) [1] in continuum mechanics.

Despite many research works considering metal foams largely involving heat exchange applications, an overall comprehensive view on the performance of metal foams based on their structural properties is hitherto unaddressed in the literature. In the present work, an air forced convection-laminar flow in a vertical channel is considered in which a heated plate along with metal foam is placed at the center

Laminarization of the turbulent flow of Helium in a heated vertical finned tube was studied using a low-Reynolds number turbulence model. The study was carried out for an inlet Reynolds number of 6000, a non-dimensional wall heat flux value of 0.003, the number of fins ranging from 8 to 24, and non-dimensional fin height ranging from 0.1 to 0.3. Reductions in turbulent kinetic energy production and

Radiant heat flux of fire plume is an essential parameter indicating the hazards of a fire. In this work, fire experiments of a wall-attached fire with different aspect ratios were conducted. In addition, the effect of the sidewall on mean flame height and radiant heat flux of the rectangular fire was investigated. The sidewall causes a decrease in air entrainment; therefore, the mean flame height

Evaporation, crystallization and heat transfer in a droplet of NaCl/H2O solution have been studied experimentally. Crystallization began at the edges of the droplet at solution supersaturation S = 1.94 (S = Csup/Csat, where Csup is the salt concentration in a metastable region (supersaturation), and Csat corresponds to saturation), which is noticeably higher than the previously obtained supersaturation

Heat dissipation is an important concern for micro devices which could be overheated in their working process. In the present work, aiming to find new methods for heat dissipation, the thermophysical properties induced by surface phonon polaritons in multilayer systems were probed. The specific heat capacity, expansion coefficient, thermal conductivities along in-plane and also cross-plane directions

The present work was aimed at investigating the effects of row number of effusion holes and coolant discharge ratio from channel tip on the thermal performance of an emulated cooling passage typical in the leading portion of a gas turbine blade. With each effusion and discharge condition, the full-field heat transfer data along with the channel averaged Fanning friction coefficients and thermal performance

In order to increase the performance of a heat exchanger flowing ethylene glycol (EG) and water (W) mixtures, the effects of different twisted tapes on heat transfer and flow characteristics in a heat exchanger tube is experimentally investigated. Material of the twisted tapes and the tube is selected as stainless steel. Three different volumetric ratios of EG and W mixtures are used with the volumetric

This study aimed to determines the heat transfer for flow past a cylinder with a slit. The flows past a cylinder with a slit at different angles of inclination were simulated to determine the effect of the inclination of the slit on the flow pattern and heat transfer. The results show that the slit increases the local Nusselt number and the average Nusselt number for a cylinder. At regimes of higher

In this study, a two dimensional enthalpy-based lattice Boltzmann method was developed to simulate the non-Newtonian melting process inside an enclosure. To examine the effect of power-law indexes in the phase change process, Nusselt number and the position of melting front for flow exposed to different flow behavior indexes (0.8−1.8) and Rayleigh number (50000, 170000, 840000) were investigated. Results

Carbon nanotubes/epoxy composites are increasingly employed in several industrial fields, because of the enhanced material properties provided by the nanofillers. In particular, the thermal conductivity of these nanocomposites is determined by heat transfer mechanisms occurring over multiple scales, thus causing a complex relation between effective response and microscopic characteristics of the material

Triply Periodic Minimal Surfaces are attractive porous media for the design of volumetric solar energy receivers; their design involves the evaluation of their heat transfer capabilities in the mixed conductive/radiative mode. We present image-based computations of effective thermal conductivities (ETC) for different radiation/conduction ratios in twenty distinct TPMS structures, using a Hybrid Random

A novel technical solution about helically coiled tube-in-tube (HCTT) heat exchanger with double cooling source is proposed to obtain regeneratively cooled air for advance aeroengine. 54 simulation runs are performed according the Box-Behnken design table, in which the effect of geometrical and operating parameters on performance of heat exchanger are well considered. Grid independence was carefully

This article presented an experimental investigation of thermo-acoustic instability of RP-3 (Rocket Propellant 3) aviation kerosene under supercritical pressures in a vertical upward circular channel. The oscillation characteristics of measured parameters were studied. The mechanisms and characteristics of unstable flow and heat transfer were analyzed. The effects of operating parameters, including

Hotspots have become one of the most limiting factors in the conception of more and more performing electronic chips. Although many wicking materials are used as porous media in used as porous media in flat plate heat pipe (FHP), copper metal foams are not well studied with these devices. In the present study, a three-dimensional FHPs with multi heat sources is investigated numerically using COMSOL

The present work aimed to conduct the visualization study on the effect of the ethylene glycol concentration on the interfacial behavior of successive droplets during the impacting onto a horizontal hot solid surface. The tested liquid droplets were pure water and two ethylene glycol-water mixtures, which contain 10% and 20% of ethylene glycol. A polished cylindrical plate of stainless steel (SUS 304)

To investigate the effects of tip gap height and the squealer cavity depth on aerothermal performance of a gas turbine rotor, two tip gap height and eight squealer cavity depth are investigated under stage environment. For the aerodynamic performance of blade tips, when the tip gap height is increased from 1.0% span to 1.5% span, the tip leakage flow rate is increased by about 1.0% total mass flow

Nanostructure and wettability present great potentials on high power electronics cooling. However, it is challenging to design optimal nanostructure for thermal management due to the mechanism of interaction between structure and wettability on boiling heat transfer which is not explicit. In this paper, a series of rough surfaces with different wettability were modeled to study the relationship between

The goal of this paper is to focus on a strategy to reduce the discharge time for a heat sink filled with a Phase Change Material (PCM). Reducing the heat discharge time is one of the key criteria in the design of a PCM based heat sink used in electronics cooling. To date, almost all of the studies have focused on the improvement of charging time for continuous operation under heavy computational loads

In this paper, thermal contact resistance between a pair of 8-harness satin woven pierced composites is numerically investigated when the interface gaps are filled with air. Numerical model of the rough surfaces is based on measured results of actual specimens by a microscope. The results show that thermal contact resistance decreases with an increase in both loading pressure and temperature. The effects

This paper reports an experimental and theoretical study of sessile water droplet evaporation during depressurization. During the experiments, three kinds of surfaces were used: copper, slide glass and Teflon. The change in droplet shape with ambient pressure was recorded. The experimental results showed that the water droplet evaporated the fastest on the slide glass surface and the lowest on the

To understand Microwave (MW) heating and boiling of binary liquid mixtures, a new multiphysics model was developed. The new model solves Maxwell's equations for the electromagnetic field distribution. Concerning the coupled dispersed and segregated vapor-liquid flow during MW boiling, it was modelled based on a hybrid Two-Fluid-Volume-of-Fluid method. As for the modelling of heat and mass transfer

The effect of slippage on the linear hydrodynamic flow stability of a shallow fluid layer induced by an inclined temperature gradient was studied for fluids with Prandtl number of 0.1, 0.7, 10 and 500, related with applications. The basic flow is induced by the horizontal component of the inclined temperature gradient. The slippage in the horizontal walls provide changes in the instability modes giving

In the present work, the influences of exponentially temperature-dependent viscosity on free convection in a porous cavity with a circular cylinder under local thermal non-equilibrium (LTNE) condition are investigated numerically via lattice Boltzmann (LB) method. To incorporate the LTNE effects, the temperature evolution equations are constructed by adding some unified source terms, which also preserve

The present study on vertical two-phase closed thermosyphon (TPCT) is aimed to determine the suitable volume-filling ratio, as a function of geometries, heat flux and vapor temperature, in order to avoid the potential local dryout in the evaporator section and hence to maximize the performance. In the study, the droplet entrainment, which is caused by the internal counter flow during the nucleate boiling

To ameliorate the thermal management of a regenerative cooling system in an advanced engine, the turbulence characteristics and entropy generation in a buoyancy-driven supercritical hydrocarbon fuel flow are numerically explored in detail. Several common buoyancy criteria (Gr/Re2, Gr/Re2.7 and Grq/Grth) are established and a three-dimensional numerical model is solved with an advanced LES model. The

Buoyancy-driven ventilation of an enclosure containing a convective area heat source with low surface emissivity is studied in this paper. Based on the dynamics of turbulent plumes generated from an area heat source, the mathematical models for dimensionless thermal stratification height are deduced and integrated into a unified formula in this study. And a mathematical model governing the transition

In this paper, the flow channel layout in latent heat storage unit is optimized to balance the effect of heat transfer and flow resistance based on topology optimization. A simplified two-dimensional latent heat storage unit is established and a binary objective function is adopted. The influence of different weighting coefficient ratio on the channel structure is discussed. Results show that as the

We develop formulas to approximate the effective thermal conductivity of composite materials consisting of a matrix with nominal dimensionless conductivity Kmat=1 containing inclusions (holes) with a conductivity Khole≤1 laid out in fractal patterns: 2D Sierpinski carpets and 3D Menger sponges. Direct simulation of steady state heat conduction in finite stages of construction of these objects provide

Quatrefoil perforated plate (QPP) is a kind of whole circular support plate for the shell side of shell-and-tube heat exchanger (STHX), and the design and optimization of heat exchanger with this support structure are the key technologies to study and improve the performance of heat exchanger. The influences of the hole height and plate spacing of the QPP on the thermal-hydraulic performance of the

Natural draft dry cooling tower (NDDCT) are a favourable choice for the cooling system of concentrating solar thermal power (CST) plants located in arid regions with high solar radiation. However, additional cooling towers may be required as the capacity of the CST plants is increased. The geometrical arrangement of the NDDCTs is an influencing parameter on the thermo-flow performance of the entire

In this work, a double-MRT lattice Boltzmann (LB) model for thermal multiphase flow is presented and analyzed. The model is based on a pseudopotential scheme, and introduces a second equation with a non-diagonal relaxation matrix and an explicit definition of the equilibrium distribution in moment space. This alternative approach formally reproduces the target energy equation with no additional terms

Effective thermal conductivity in 3D heterogeneous media consisting of fillers dispersed randomly in a matrix is evaluated through FEM based numerical simulations. The study examines the influences of various factors such as the filler concentration (up to 30%), fillers shape (spheres and polyhedrons) and size (100 to 300 μm) and thermal characteristics of fillers and matrix. Simulations indicate that

We analyze an extension for the Fourier law to describe the heat propagation in non-homogeneous solids by taking into accounts simultaneously different diffusion regimes such as the subdiffusion and superdiffusion. It considers differential operators of non-integer order, i.e., fractional differential operators, which are a simple way, from the formal point of view, of understanding the photothermal

Finned heat pipe radiators are popular as heat dissipation system of electronic components due to high reliability. But the inferior airside heat transfer limits its heat dissipation performance. Thus, the metal foam heat pipe radiator is introduced to solve this issue with metal foam substituting fins. The copper foam with 15 PPI (Pores per inch) is adopted to fabricate prototype to explore the performance

In this study, a new approach is developed to separately examine conductive and convective heat transfers through an assemblage of solid particles with fluid flowing through it. The inter-particle interactions are taken into account by using the cell model. The energy equations are solved along with the creeping flow field using a finite difference based numerical method for a range of physical and