Journal of Thermophysics and Heat Transfer, Ahead of Print.

Metallic lattice-frame materials, due to excellent heat transfer performance under high heat flux and mechanical property, are regarded as the potential candidates for a vehicle leading edge. This paper presents a new-style lattice-frame sandwich panel with active heat transfer wall-plate. The heat transfer performance and thermal–structural responses are numerically studied, considering the temperature-dependent

Molten calcium–magnesium–alumino–silicate (CMAS) infiltration into thermal barrier coatings (TBCs) of gas turbines causes loss of strain tolerance and delamination of the ceramic topcoat. To develop efficient mitigation strategies, it is crucial to understand CMAS infiltration dynamics into the porous topcoat. This study introduces an integrated model, incorporating liquid flow in unsaturated porous

Journal of Thermophysics and Heat Transfer, Ahead of Print.

A computational fluid dynamics (CFD) laminar-to-turbulence transition model was developed for the NASA Ames Research Center’s 20 MW Panel Test Facility (PTF). Surface pressure, heat flux to a water-cooled plate, and surface temperature on a tile plate coated with reaction-cured glass were measured across several conditions in the facility and compared with laminar and fully turbulent CFD simulations

The magnetron sputtering has been used to prepare metal foam wicks for heat pipes by coating the surface of copper foam with zinc oxide (ZnO) nanoparticles. The main properties, including microscopic appearance, contact angle, and capillary performance, as well as the boiling heat transfer performance of the metal foam wicks, are characterized and tested. The results indicate that, compared with the

This work describes numerical and experimental research in the Indian Hypersonic Shock Tunnel 3 on a blunt cone model and related computation of the facility parameters: nozzle reservoir conditions, nozzle transit time, and freestream conditions. Specialized codes accounting for real gas effects and nonequilibrium are used to obtain facility parameters. Starting at freestream conditions, a physicochemical

Journal of Thermophysics and Heat Transfer, Ahead of Print.

The study of fluid-induced vibration of helical elastic coiled tubes to enhance heat transfer is very important for engineering practice and energy saving. Fluid-induced vibration and enhanced heat transfer of a helical elastic coiled tube heat exchanger were analyzed based on its finite element model, by using a two-way fluid–solid coupling method. Vibration response of the helical elastic coiled

The fully developed turbulent flow and heat transfer in a plane channel at a nominal shear Reynolds number of 180 is studied via the direct numerical simulation technique. A linear velocity-slip boundary condition is assumed on one of the channel walls, whereas the classical no-slip condition is imposed on the other wall. The heat transfer at the slip wall is assumed to occur with and without temperature

Journal of Thermophysics and Heat Transfer, Ahead of Print.

The fluid motion characteristics have an important influence on the evolution of the backflow vortex near the pipe wall. The instantaneous velocity and instantaneous temperature of the outlet flow channel section, the shear stress of the outlet flow channel wall, the boundary layer thickness, and the Nusselt number under different ratios of the upstream and downstream pipe diameter are studied at the

Natural convection in a partially porous cavity with a heat generating source in the solid phase is studied numerically under a local thermal nonequilibrium condition. The right and left walls of the cavity are maintained at hot and cold temperatures, respectively. The horizontal walls are thermally insulated. The finite volume method and the semi-implicit method for pressure-linked equations (SIMPLER)

Today, many attempts have been made to introduce small particles with high thermal conductivity to the heat transfer fluids to improve the thermal properties of conventional fluids used in heat transfer. Therefore, in this paper Fe3O4 nanoparticles are used as fluid additives to study properties of the laminar flow regime. So, the laboratory setup was designed to experimentally investigate the forced

This work focuses on the experimental study of the heat transfer and film cooling characteristics of a fully cooled vane under high subsonic conditions; the transient heat transfer measurements with thermocouples were employed. The inlet Reynolds numbers of the cascade ranged from 3.0×105 to 9.0×105 and the exit Mach number was 0.8. Two freestream turbulence intensities (1.3% and 14.7%) and three mass

According to recent aircraft engine development trends, the performance enhancement of the propulsion plants is accompanied by both an increase of the overall pressure ratio and a decrease of the fan pressure ratio. Projections for the next decade show that equipment within the engine compartments can exceed their temperature thresholds, penalizing aircraft safety. Loop heat pipes (LHP) represent a

Homogeneous nucleation and bubble evolution inside a fuel droplet trigger the occurrence of flash boiling, which shows a high potential to improve the droplet evaporation. To understand the bubble dynamic characteristics, an analytical study on homogeneous nucleation and bubble evolution has been performed, based on the flash boiling model proposed in our work. First, the nucleation rate graph of seven

Journal of Thermophysics and Heat Transfer, Volume 35, Issue 1, Page 1-2, January 2021.

A new analysis is made on the viscous dissipation within a microchannel parallel plate gap induced by an oscillating lower plate and a stationary upper plate, assuming a one-dimensional, incompressible, laminar, Newtonian flow with constant properties. Firstly, a new form of velocity solution is obtained, which consists of a main sinusoidal term and a block of time-dependent summation terms. This is

A direct simulation Monte Carlo based approach is proposed to model the planar shock-wave reflection in a shock tube. The approach is validated through comparisons with available time-dependent pressure and absorbance measurements of gas relaxation behind a reflected shock in an argon–oxygen gas mixture for incident shock velocities of 1–1.5 km/s. It is then used to model reacting airflows for velocities

In this paper, the behavior of the plenum pressure behind a transpiration-cooled porous material sample after an incident surface heat flux to the sample is analyzed in experiment and theory. Two porous materials, zirconium diboride and carbon/carbon, were characterized using the pressure-based noninteger system identification method. The resulting impulse responses are analyzed based on two numerical

This work focuses on the heat flux characteristics of a hypersonic blunt body with a tangential Mach 3 supersonic cooling film. Experiments were carried out with main flow’s Mach numbers of 6, 7, and 8; total pressure of 15 MPa, and total temperature of 2600 K. The wall surface heat flux was measured under different cooling film pressures. Nanoparticle-based planar laser scattering was used to visualize

The thermal performance of high-Prandtl-number Fe3O4–vacuum pump oil (VPO) nanofluid with wire coil (WC) inserts is experimentally studied under laminar flow conditions. The volume concentrations of the nanoparticles considered are 0.05, 0.2, and 0.5%. The study also investigates different values of the ratio of the pitch to diameter (p/di) of the WC inserts; those include 1.79, 2.54, and 3.24. Mass

The impacts of Newtonian heating and a magnetic dipole in a two-dimensional ferrofluid due to a stretchable cylinder are analyzed in this paper. The effects of the homogeneous–heterogeneous reactions and a magnetic dipole are taken into account. Flow is caused by a linear stretching cylinder. Fourier’s law of heat conduction is applied in the evaluation of heat flux. Impacts of emerging parameters

A waste heat recovery system consisting of a hybrid power and cooling cycle is described in this paper. It couples a thermoelectric generator (TEG) and an organic Rankine cycle driving a vapor compression cycle to implement heat activated power and cooling. The system was designed, developed, and tested under laboratory conditions using a hot air source simulating a heavy-vehicle exhaust stream. The

The determination of the ablation rate for thermal protection systems on atmospheric entry is a difficult task, but can have significant implications in terms of safety and heat shield design. Ablation sensors of various kinds can be used to measure ablation directly, but in the event of a failure of these sensors, the use of thermocouples imbedded in the heat shield for determining the ablation rate

An experiment was carried out to study the effect of refrigerant mass flow rate, heat flux density, and saturation temperature on boiling heat transfer coefficient and frictional pressure drop in microchannel. Flow patterns are captured by a high-speed camera. HFO1234yf was used in rectangular microchannels with a hydraulic diameter of 0.5 mm. The results showed that there were eight flow patterns

The ablating species from the thermal protection systems upon atmospheric entry interact with the atomic/molecular gas species in the shock layer and form new products that affect total radiation. In this work, the ablation of carbon was experimentally studied by resistively preheating graphite strips to representative reentry wall temperatures and exposing them to hypervelocity Earth-entry flow conditions

In order to obtain the thermal design parameters that have a great influence on the temperature T of the spectrometer frame, the sensitivity of the thermal design parameters of a balloon-borne spectrometer system was analyzed and calculated by the global sensitivity analysis (GSA) method based on the backpropagation neural network (BPNN) surrogate model. Firstly, the BPNN with 12 selected thermal design

The practical use of supercritical carbon dioxide (sCO2) for systems operating on the Brayton cycle is currently difficult due to the occurrence of nonequilibrium and uncontrolled states near the critical point. This paper provides an analytical overview of existing mathematical models and theories to predict the occurrence of a condensing state and its effect on compressor performance in conditions

This paper presents a novel surrogate modeling approach that enables the application of Bayesian calibration to a gas turbine disc finite element (FE) heat transfer model. The surrogate modeling process begins with two transformations of the FE model predictions: first, principal components analysis “rotates” the multivariate FE model outputs into an uncorrelated and dimension-reduced subspace; second

This paper focuses on a numerical investigation of steady two-dimensional natural convection and volumetric radiation interactions in a concentric annulus between two square isothermal cylinders. The annulus is filled with a gray absorbing–emitting and non-scattering medium. All the walls are assumed to be gray, diffuse, and opaque. The dynamic and thermal interactions are studied through a finite

The present study investigates the effects of material discontinuities and thermal resistances on the temperature reconstruction and heat flux evaluation via an inverse heat transfer method in hypersonic wind-tunnel tests. Thin coating layers and adhesive interfaces support a localized multidimensional temperature perturbation that alters the near-surface field. A technique is developed for the real-time

Precursor electrons ahead of the shock wave are measured with a Langmuir probe using the hypervelocity shock tube of the Japan Aerospace Exploration Agency. The current–voltage curve of the probe is obtained with rapid scanning of the applied voltage, and the distributions of electron number density and temperature are obtained. The experimental results are compared with the analytically calculated

A methodology for directly informing flight vehicle radiative heating simulations based on shock-tube measurements is developed. The differences between these shock-tube informed (STI) radiative heating values and the corresponding nominal values are typically the dominant contributor to the radiative heating margin. Previous approaches for evaluating the STI radiation were limited to the stagnation-point

Journal of Thermophysics and Heat Transfer, Ahead of Print.

The interaction effects of surface radiation with natural convection of a transparent medium in an asymmetrically cooled square cavity including a partially heated inner circular cylinder have been numerically simulated. In this context the finite volume method and the discrete ordinates method are incorporated to simulate radiation problems. The flow inside the cavity is driven by the heated part

This study applied an incompressible version of the smoothed particle hydrodynamics (SPH) method for simulating a sloshing circular cylinder during natural convection flow over a T-shaped fin in an enclosure occupied by Al2O3 nanofluid. The center area of the enclosure is saturated with a heterogeneous porous medium. Variations in the thermal conditions of the embedded circular cylinder and T-shaped

Natural convection in a rectangular enclosure that arises from multiple heat sources at the bottom wall is considered. The top wall is kept at the surrounding temperature while the vertical walls and the rest of the bottom wall excluding the heat sources are assumed to be adiabatic. Based on the above conditions, the mathematical model is formulated in terms of the dimensionless equations. Finite difference

Considering the constraints of manufacturing sharp ribs, a systematic study of the aerothermal behavior of the sharp and rounded-edge ribs has been performed. The investigation was conducted in a square channel with 45 deg ribs over a wide range of Reynolds numbers (Re=6000 to 135,000). The rounded-edge ribs are known to reduce heat transfer and friction compared to the sharp ribs. However, the studies

Pin-fin arrays are generally present in trailing-edge regions of gas-turbine blades for internal cooling purposes. An elevated temperature is important to enhance the thermodynamic efficiency of gas-turbine cycles, and internal blade-cooling mechanisms are employed to mitigate material failure at these high temperatures. It is also important to have high heat transfer at a limited pressure drop to

Numerical simulations are carried out to predict the phantom cooling on the blade tip and casing from blade-surface film coolant. The impacts of hole compound angles and shape for the pressure side (PS) film hole on the tip and casing phantom cooling are investigated under various mass flow ratios (MFR) of coolant to mainstream from 0.7% to 2.6%. The results indicate that the coolant derived from the

Journal of Thermophysics and Heat Transfer, Ahead of Print.

In the present Paper, different wall heat flux evaluation methods for rocket engines are analyzed and compared. The test case for the comparison is a supercritical load point of an H2/O2 upper-stage engine. The evaluation of the heat flux using existing gradient methods shows unacceptable deviations, whereas significant improvements are found with an inverse heat transfer method. Using a Nusselt number

Journal of Thermophysics and Heat Transfer, Ahead of Print.

Geometrical configurations of tubes and vortex generators have been optimized in order to improve the hydrothermal characteristics of fin-and-tube heat exchangers. The work is divided into two parts: the first part concerns the effects of the inclination angle of the oval tube (α=0, 10, 20, 30, 40, 50, 60, 70, 80, and 90°); in the second part, the best case resulting from the first part is optimized

Heat transfer under space restriction is a challenging task in many energy systems due to unavoidable design constraints. For such conditions, the use of regular fin shapes cannot be possible, and eccentric geometry becomes a necessity. In this work, an optimization technique based on the inverse analysis using the differential evolution (DE) has been proposed to identify the dimensions of two-dimensional

The use of a fourth-order modified Runge–Kutta (MRK) scheme on a transformed coordinate system with Maxwell’s equations for nonrectangular domains and applications is presented. Maxwell’s equations are the governing equations for modeling electromagnetic wave propagation involving scattering, radiating structures, transmission lines, radar, biomedical applications, and nondestructive testing. Because

Woven thermal protection systems (TPSs) are being developed for extreme heating conditions experienced during hypersonic atmospheric entry. A linear elasticity solver is used to model this new class of TPS. In particular, this paper explores and assesses the effectiveness of the linear elastic model for the Heatshield for Extreme Entry Environment Technology (HEEET) woven material through comparisons

Journal of Thermophysics and Heat Transfer, Ahead of Print.

To decrease the heating and cooling demand of a building, thermal insulation is a well-known method. The properties of insulation materials are affected by many environmental factors, such as temperature and humidity. In this study, the change of thermal conductivity depending on relative humidity for a cold room was investigated experimentally. Furthermore, glass wool and rock wool were used as insulation

The experimental analysis is conducted to evaluate the thermal hydraulic performance of nanofluid flow in a tube with a helical screw insert at a number of strips and different twist ratios in a transition flow regime. The Nusselt number is achieved the enhancement with nanofluid flow in the double-strip helical screw tape (DS-HST) as compared with the single-strip helical screw tape (SS-HST) insert

This Paper presents the simulations of CO2 and CO infrared radiation behind shock waves and in expansion flows. This work is motivated by the little amount of characterizations of CO2 infrared radiation in these expansion flows and thermodynamic regimes, whereas carbon dioxide infrared radiation is deemed to contribute significantly to the afterbody heating withstood by a Martian spacecraft. Japan

The entropy generation due to magnetohydrodynamic mixed convection flow and heat transfer in a Gamma-shaped porous cavity is explored in this research by the finite volume technique. There exists an internal heating generation inside the cavity and the top and bottom walls are moving by constant velocities to induce forced convection. The cavity is filled with copper/water nanofluid and subjected to

In this Paper, two-dimensional unsteady laminar fluid flow and heat transfer characteristics have been investigated numerically in a symmetrically heated vertical channel with inclined baffles. The baffles are attached on both walls in a staggered manner with constant spacing. OpenFOAM®, an open source code based on the finite volume method, is used to solve the governing equations with the adequate

An experimental method is reported for the evaluation of the transmittance, in the 8–14 μm wavelength range, of the hypersonic flow of the SCIROCCO Plasma Wind Tunnel. The experimental setup for the measurements consists of a thermocamera and a black body placed on opposite sides of the facility, with hypersonic plasma in the middle of them. The situation is representative of the conditions at which

The goal envisioned for the Reduced-Order Computational Fluid Dynamics and Heat Transfer (ROM-CFDHT) procedure is obtaining fast turnaround in simulation time so that computational fluid dynamics can form a component of a system-level design tool. To accomplish this, a set of finite-element schemes is proposed, including the choice of the quadratic interpolation functions, the penalty approach, an

This paper proposes an analytical model for computing the highest temperature based on the Fermat point in chips. The transient temperature is determined through the heat source method based on the Fourier transform. Thermal accumulation at the Fermat point in chips of heat sources with identical powers is proposed based on the thermal path, and the expression of the highest temperature solved here

In the present study, the enthalpy-based lattice Boltzmann method (LBM) with multidistribution function model is used to investigate the melting process engendered by a thin heater placed in the horizontal median plane of the cavity. The latter is cooled from its vertical walls by maintaining their temperature constant at TC, lower than the constant temperature TH of the heater (TC

The study on fluid-induced vibration of helical elastic tube bundles (HETBs) to enhance heat transfer is of great significance in industrial production and energy utilization. The fluid-induced vibration response and the heat transfer property of a HETB heat exchanger were analyzed by using a two-way fluid–solid coupling method. The vibration frequency, displacement amplitude, and heat transfer coefficient