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

A computational simulation of various mixing laws for gaseous equations of state using planar traveling shocks for multiple mixtures in three dimensions is analyzed against nominal experimental data. Numerical simulations use the Sandia National Laboratories shock hydrodynamic code CTH and other codes including the thermochemical equilibrium code TIGER and the uncertainty qualification and sensitivity

The micro-pin-fin heat sink (MPFHS) is widely employed for the heat transfer enhancement of microchannel heat sinks. In the current paper, the effect of flow normalization on the thermohydraulic performance of micro-pin-finned heat sinks is studied numerically. Two geometries of MPFHSs, the conventional design micro-pin-fin heat sink (CD-MPFHS) with a uniform-width micro pin fin and the proposed design

For realizing effective vibration excitation and control, a new vortex generator (VG) is proposed. Based on a two-step calculation strategy, the flow-induced vibration responses of the elastic coil pipes (ECPs) when installing the VGs in the heat exchanger (HE) are investigated. In various flow-induced situations, the heat transfer performances (HTPs) of the ECPs are studied. Numerical results demonstrate

As long-distance human space travel becomes more realistic, the need for long-term storage of cryogenic propellants becomes a forefront issue. Effective cryo-fluid system management becomes a necessity to solve this issue. The fuel–oxidizer combination of choice for NASA’s Space Launch System is liquid hydrogen (LH2) and liquid oxygen (LOX). The current strategy used on many upper stage vehicles, including

The present study outlines a methodology for modeling instantaneous unsteady film condensation of vapor on a vertical flat wall. Both analytical and numerical solutions of the problem were obtained and compared with each other. Time variation of the thickness of the condensate film, velocity, and temperature profiles in the film as well as the friction and heat transfer coefficients were analyzed.

Surface coking is significantly affected by the mass transfer of regenerative cooling system in advanced aeroengines. On the basis of the detailed chemical kinetic mechanism of China No. 3 jet fuel (also known as RP-3), the flowfield and surface coking of RP-3 in the curved cooling channel surrounding around the cavity flameholder of scramjet are numerically studied. Results indicate that the vortex

Journal of Thermophysics and Heat Transfer, Ahead of Print.

To obtain accurate physical description of nonequilibrium flows, Eu proposed a set of generalized hydrodynamic equations (GHEs) using a nonequilibrium ensemble method. However, Eu’s equations are very difficult to solve by employing the well-established numerical schemes for hyperbolic partial differential equations. Recently, a simplified nonlinear model based on Eu’s equations has been proposed by

Direct molecular simulations (DMS) of nitrogen dissociation in adiabatic reservoirs covering a wide enthalpy range are presented. These conditions more realistically reproduce the gas state in a hypersonic shock layer than prior isothermal DMS studies. The Minnesota ab initio potential energy surface is used for nitrogen molecule-molecule (N2−N2) and nitrogen atom-molecule (N−N2) classical trajectory

Journal of Thermophysics and Heat Transfer, Ahead of Print.

In this Paper, the lattice Boltzmann method (LBM) is adopted to simulate bubble dynamics and heat transfer characteristics along inclined structured surfaces in subcooled boiling. First, the growth of the bubble in the liquid without consideration of gravity is simulated to validate the selected LBM multiphase model. Then, the current research is concerned with the bubble motion and its thermodynamic

The present study investigates heat transfer enhancement of forced convection in a horizontal channel by nonsymmetric electric field. The electrical field is generated from a wire electrode charged at a high voltage of direct current with a positive polarity. Numerical calculations have covered a wide range of parameters (that is, V0=12, 15, and 18 kV; and 10≤Re≤5000). The previous studies with a symmetrical

In practical applications, it is difficult for the control parameters of the proportional integral derivative (PID) thermal controller to be self-tuning online. As the control object or environment changes, the control parameters are required to change accordingly. An intelligent thermal controller based on the deep deterministic policy gradient, called DRLTC, is proposed. Two types of reinforcement

Using two-phase flows because of their high thermal conductivity coefficients is favorable in various industries such as oil, petro chemistry, and power plants that require significant thermal conductivity coefficients in heat exchangers. On the other hand, the limiting factor in benefiting from these flows is the critical heat flux phenomenon, the onset of which must be delayed by various means. One

A computational approach is developed to simulate high-enthalpy shock propagation under strong nonequilibrium conditions, such as reentry experiments at NASA’s Electric Arc Shock Tube (EAST) facility. Two-dimensional axisymmetric simulations of EAST flow are performed for Earth reentry at 10 km/s. An 11-species weakly ionized air model is used to capture the real-gas behavior with reaction rates from

The present study deals with a computational investigation on the effect of surface radiation for a buoyancy-induced flow and heat transfer from a horizontal cylinder suspended in air. The numerical simulations have been performed in the turbulent regime by changing the Rayleigh number from 1010 to 1013, surface emissivity of the cylinder surface within the ranges of 0.2–1, and considering temperature

An entropy-based error indicator is presented to assess the solution accuracy of fluid flow simulations with heat transfer using the second law of thermodynamics. This paper presents a new approach for the characterization of numerical error using a parameter called an “apparent entropy production difference.” A control-volume-based finite-element method is used to discretize and solve the governing

This paper analyzes test data obtained by the authors and corresponding results of numerical simulation of transients in a high-power loop heat pipe (LHP) with a small-diameter condenser bypass. Thermal-fluid oscillations (TFOs) and evaporator partial dryouts were observed for the same high-power LHP without a bypass operating at several intermediate power levels after heat load steps under certain

Comprehensive reviews of rarefied gas flows in circular and square microchannels over wide ranges of rarefaction show large differences in Poiseuille numbers and reduced flow rates when identical length scales are used. The continuum Poiseuille numbers differ by 12.5%, and the free molecule reduced flow rates differ by 11%. This work demonstrates that the product of reduced flow rate and continuum

Journal of Thermophysics and Heat Transfer, Volume 34, Issue 3, Page 669-672, July 2020.

Alumina reduction by laser ablation has been researched toward the lunar resource utilization without reducing agents: especially carbon. Alumina preheating and laser spot size optimization were conducted to increase both the ablation rate and the molar reduction percentage in alumina reduction using laser ablation. A sintered alumina rod was heated to Tpre=1500–2300 K. Then, laser ablation was done

A three-dimensional, unstructured-grid, pressure-based, reacting flow, computational fluid dynamics and heat transfer methodology was employed to study the base-heating environment of a lunar lander demonstrator, during terrestrial ground testing. Two base-heating environments were investigated: lunar lander demonstrator sitting on pad, and lunar lander demonstrator hovering at a distance above ground

A high-speed aircraft, capable of maneuvering when moving in dense layers of the atmosphere, is subjected to high dynamic and thermal loads, which can lead to destruction of its shape and changes in its aerodynamic characteristics. Consequently, the main design objective is the thermal protection of structural elements of aircraft. Electron transpiration cooling is a prospective method for the solution

Laser is widely used in material thermophysical properties testing because of its good test accuracy and test efficiency. However, due to the high market price of laser flash devices, their promotion space is limited. Based on the unsteady heat transfer model of a laser point heat source, the enantiomorphous heat source theory was introduced to modify the influence of an adiabatic boundary on the temperature

Experiments were conducted to simultaneously quantify the voltage distribution and heat losses along the length of an arc-plasma wind-tunnel constrictor employing air and argon gas. The objective was to generate a detailed data set and make it available electronically to the scientific community. High-spatial-resolution voltage measurements allowed the identification of a wavelike structure in the

In this study, an analytical expression for the second virial coefficient of the Stockmayer potential obtained by us previously has been used to evaluate the Boyle temperature and Boyle volume. The analytical expression is used to obtain an accurate and precise evaluation of the Boyle temperature and Boyle volume for refrigeration gases. The accuracies of the Boyle temperature and Boyle volume results

Notable efforts have been done to describe the propagation of a solar radiation in a heterogeneous medium containing particles. In the latter case, it is necessary to use the radiative transfer equation (RTE) that describes the propagation of radiations in participating media. Herein, the RTE was solved by using the four-flux method coupled with the T-matrix approach for the determination of effective

In this paper, two-dimensional numerical modeling of a premixed porous combustion is presented by a Lattice Boltzmann approach. In this solution, the flow distribution is replaced by a pressure distribution equation using the Darcy and Forchheimer model as the multiple-relaxation-time code. The laminar propane-air mixture with Reynolds number of 100 and Prandtl number of 0.75 is put through a silicon

The convective heat transfer enhancement and deterioration of the supercritical hydrocarbon fuel in the regenerative cooling channels of a scramjet were investigated numerically. This study focused on the heat transfer enhancement and deterioration suppression of the spiral rectangular channels with enhanced heat transfer effects resulting from the enhanced turbulence intensity and induced spiral flow

The effect of ply orientation on the in-depth response of carbon-phenolic ablative, which is widely used for thermal protection of rocket motor nozzles and reentry capsules, is studied using a newly developed axisymmetric, unstructured, finite volume model. The numerical scheme for solving the conservation equations of solid mass, gas mass, and mixture energy, along with Darcy’s law for the flow of

Merits of shear-stress transport and its wall-distance-free variant are evaluated by accommodating comparisons with direct numerical simulation and experimental data for heat and fluid flow problems. To improve the temperature field predictions in turbulent boundary layers and around the stagnation region accompanied by flow separation and reattachment, the thermal eddy diffusivity is approximated

Turbulent junction flow is a vortex system upstream of a blockage embedded in a turbulent boundary layer, which leads to augmented heat transfer near the blockage. Vortex legs wrap around the blockage and travel downstream as longitudinal vortices. In multistage axial turbines or multiple row tube heat exchangers, these longitudinal vortices can collide with junction flow vortices further downstream

The influence of different assumptions for thermochemistry modeling in hypersonic flow over a double-cone geometry is investigated. A computational fluid dynamics analysis is used to study the double cone in three different thermochemical cases, nonequilibrium flow, equilibrium flow, and frozen flow, for four different mixtures of nitrogen and oxygen. Specific areas of interest include the thermochemistry