Sudden Heating Research Articles

Stability and Failure Analysis of a W-Based Microhotplate

In this paper, we present the stability and failure of a tungsten-based microhotplate (W-MHP) fabricated with 0.5- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> standard CMOS technology. Resistance measurements and three-dimensional optical profilometer results combined with scanning electron microscopy observations were used to analyze the failure mechanisms of the W-MHP at operation temperatures up to 1000 °C. The electro-stress migration of the W film, recrystallization of the polycrystal W thin film, and breakage of the dielectric membrane were the dominant stability-failure mechanisms observed. The W-MHP had recoverable deformation and no evident resistance drift when the working temperature was below 450 °C. Correspondingly, at the operating temperature range of 500 °C– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$850~^{\circ }\text{C}$ </tex-math></inline-formula> , the W-MHP showed unrecoverable deformation and regular resistance drift caused by the electro-stress migration of the W heater and the interdiffusion of atoms between the W, Ti/TiN and SiO2. At temperatures higher than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1000~^{\circ }\text{C}$ </tex-math></inline-formula> , the recrystallization of the polycrystalline W film caused a sharp drop in resistance. In addition, sudden and large heat pulses were more likely to cause the suspended membrane to rupture, which resulted from the rapid accumulation of internal thermal stress and lack of time to release, indicating that the operating temperature of the MHP should slowly increase or decrease. One million cycles of thermal pulse between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25~^{\circ }\text{C}$ </tex-math></inline-formula> and 300 °C did not cause performance degradation of the device. Self-heating high-temperature rapid thermal annealing significantly improved the high-temperature stability of the MHP. [2022-0135]

A Capillary Tube Pulsating Heat Pipe With Asymmetric Adiabatic Channels for Thermal Management

The two-phase flow passive thermal management device, an asymmetric (adiabatic channel) closed-loop pulsating heat pipe (aCLPHP), has been investigated experimentally. The thermo-hydrodynamic behavior of a pulsating heat pipe (PHP) strongly depends on various operating and geometric parameters. In this effort, asymmetry has been adopted to promote the unidirectional two-phase oscillatory motion of the working fluid. In the present study, simultaneous pressure and temperature variations under gradual and sudden heat loads are monitored to estimate thermal performance. The effects of inclination angles (IAs), heat loads, working fluids, and filling ratios (FRs) on thermal performance have been demonstrated using average thermal resistance. In a two-turn (four-channel) aCLPHP in bottom heating mode, acetone and water were used as working fluids within 50%–70% of FRs. The results show that the startup phenomena of two-phase flow and pseudo-steady-state temperature were achieved using acetone at a 60% FR up to 30° angle from a horizontal orientation. In the vertical orientation, the working fluid water at 60% FR performed well under a sudden heat load of 50 W. Adding asymmetric adiabatic channels to a PHP can be a simple and inexpensive way to improve its thermal performance.

Large amplitude vibration of annular and circular functionally graded composite plates under cooling thermal shocks

In this paper, large amplitude thermally induced vibration (TIV) of annular and circular plates is analyzed under cooling shocks. A novel comparison of the TIV response is presented under rapid cooling and heating shock loads. This is the first time that TIV study has been presented for any flexural structure under thermal cooling. Structures can experience cooling shock loads in many circumstances, for example when exposed to spills of cryogenic liquids. The functionally graded composite plates are made of 304 grade stainless steel (SUS304) and low-carbon steel (AISI1020) and are graded through the plate thickness to have a continuously varying spatial composition profile in thickness direction. Thermo-mechanical properties are assumed to be temperature dependent. The plates are modeled using first-order shear deformation theory with von Karman geometric nonlinearity. The Generalized Differential Quadrature Method (GDQM) and Newton–Raphson technique are employed to solve the governing equations. A Fourier heat equation is used to evaluate temperature distribution over time using GDQM and Crank–Nicolson approaches. The validation study is conducted based on the literature and FEM software ABAQUS. Detailed parametric study is presented focusing on the effect of thermal shock magnitude, rapidity of the thermal shock application, plate geometry, material distribution, geometrical nonlinearity and temperature dependency of material properties. Differences in the response due to these factors have been shown between cooling and heating thermal loads. Results show that importance of the inertia effect is substantially higher under sudden cooling than it is under sudden heating, for the same thermal load magnitude and rapidity of thermal shock. Moreover, it is shown that stresses induced by thermal cooling can potentially reach yield strength of the material with relatively large amplitudes of fluctuations. Therefore, to estimate realistically the structural behavior of thin/slender plates under rapid cooling, the inertia effect should be taken into the account and TIV analysis needs to be performed.

Unsteady characteristics of flow pattern and pressure drop of flow boiling in single straight microchannel under sudden heat flux increase

Unsteady characteristics of flow pattern and pressure drop of flow boiling in single straight microchannel under sudden heat flux increase

About the “Heat Shock” Phenomenon

At present, depletion and diminished performance of oil formations take place. Operation of low production wells is carried out using ESP units at the rate of max. 35 m3/per day under low suction pressure of centrifugal pumps. The drop of the centrifugal pump suction pressure below the saturation pressure leads to liberation of free gas in the pumped mixture. Operation of a centrifugal pump during pumping of gas-cut mixtures results in reduction of the ESP unit efficiency. The loss of the pump efficiency leads to the fact that the substantial part of energy is consumed on heating and temperature rise of the centrifugal pump. Operation of a centrifugal pump at elevated temperatures results in frequent faults of the ESP units and in salt deposition. In some cases, faults of the ESP units may occur out of the blue due to the uncontrolled heat release and temperature rise. Let us call a sudden uncontrolled heating of a centrifugal pump a “heat shock”. The pump failure as a result of a heat shock is normally classified as the “wrongdoing of the oil producing organization personnel”. This article addresses the possibility of detection and elimination of the “heat shock” moment - a sudden ESP failure. Solution of this problem will be useful for design engineering of the pump automatic control.

Analysis of self-excited transverse combustion instability in a rectangular model rocket combustor

A methane/oxygen mixture is considered to be an appropriate propellant for many future rocket engines due to its practicality and low cost. To better understand the combustion instability in methane/oxygen-fed rocket engines, the spontaneous transverse combustion instability in a rectangular multi-element combustor (RMC) was analyzed both experimentally and numerically. Severe combustion instabilities occurred in the RMC during repeatable hot-fire tests. The physical mechanisms were systematically investigated through numerical simulations based on the stress-blended eddy simulation and flamelet-generated manifolds method with detailed chemical mechanisms (GRI Mech 3.0). The numerical results for the frequency spectrum and spatial modes agree well with the theoretical analysis and experimental data. The driven regions of the combustion instability were identified on both sides of the combustion chamber through a Rayleigh index analysis. The longitudinal pressure oscillations in the oxidizer post were found to be coupled with the transverse pressure waves in the combustion chamber and led to periodic oscillations of the mass flow rate of propellant. Moreover, the mixing was highly enhanced when the pressure wave interacted with walls of the combustion chamber. Therefore, a sudden release of heat occurred. The pressure oscillations were enhanced by pulsated heat release. A closed-loop system with positive feedback associated with periodic oscillations mass flow rate of the propellant, and sudden heat release, was believed to account for the present combustion instability.

Working With Nature to Solve Societal Problems

Are you worried about the climate and biodiversity crises and related events like heavy rainfalls and floods, high carbon emissions, sudden heat waves, or loss of species? Are you already doing something to help solve these problems? To reduce flood risks, we can give rivers more space by reconnecting floodplains. To store carbon and help to slow down climate change, we can protect and establish wetlands or mangroves. To make cities cooler in summer, we can plant trees and install rooftop gardens. These efforts to help combat societal problems are known as nature-based solutions. To use nature-based solutions effectively, we need to understand how we can work with nature and the steps we must take to put these ideas into practice. In this article, we introduce you to the concept of nature-based solutions and how they can help solve the climate and biodiversity crises.

Influence of transient heat flux on boiling flow pattern in a straight microchannel applied in concentrator photovoltaic systems

Concentrated photovoltaic (CPV) overheating due to the high radiation intensity became the critical challenge to preventing its benefits in advancing the photoelectric efficiency. To promote the application of CPV, efficient heat dissipation becomes the key technology. Meanwhile, microchannel flow boiling, as one of the most promising solution to advance cooling of high-flux equipment, has attracted increasing attentions in recent years. However, the fluctuating and non-uniform heat fluxes of CPVs may lead to challenges to microchannel boiling for cooling CPV. Therefore, the transient flow and phase change phenomenon in a microchannel with deionized (DI) water was studied through a numerical modeling on flow boiling. The effects of different sudden heat flux increases on flow boiling two-phase flow pattern were analyzed. It was found that different heat flux increase resulted to different flow pattern evolutions, a much higher sudden increase in heat flux leaded to serious variation of flow pattern, especially the fluctuation of elongated restricted bubbles, which may evolve to annular flow or even dry-out. The vapor phase volume fraction showed a much higher growth rate. When the heat flux increase was raised from 97.96 kW/m2 to 580 kW/m2, the maximum vapor phase volume fraction was increased from 0.104 to 0.8064, and the bubble length increased from smaller than 0.3 mm to 1.5 mm in the dry zone, indicating rapid phase change. Based on analysis on pressure drop and vapor volume fraction variation, the period after receiving sudden heat flux was divided into three stages: initial period, rapid development period, and quasi-stable period. With the rising of heat flux increase from 97.96 to 580 kW/m2, the duration of rapid development period was increased from 0.03 s to 0.066 s, the pressure drop increase was obviously enlarged, from 2.43 kPa to 14.51 kPa, and the vapor phase volume fraction increase in the microchannel was raised by 3.3 times to 25.6 times, indicating more intensive boiling, and deeper effect of higher heat flux increase on the phase change. In addition, the fluctuation intensity of pressure drop in the quasi-stable period was obviously increased from 0.025 to 0.193, demonstrating the advancement in flow boiling instability under higher heat flux increase, which should be controlled.

Experimental study on a hydrogen pulsating heat pipe in different heating modes

In practical applications, the heat load changes caused by various factors require the pulsating heat pipe (PHP) to have good heat transfer performance and temperature response characteristics in different heating modes. In order to understand the heat transfer performance of a hydrogen PHP in different heating modes, the temperature curves of the PHP in two heating modes (stepwise heating and sudden heating) are obtained experimentally. The experimental results show that for a given heat load, the differences of the quasi-steady-state temperatures and the effective thermal conductivities between two heating modes are negligible. It’s concluded that the stable heat transfer performance of the PHP is reproducible in the two different heating modes.

Three-Dimensional Numerical Analysis of Longitudinal Thermoacoustic Instability in a Single-Element Rocket Combustor

This study numerically investigated the thermoacoustic combustion instability characteristics of a scaled rocket combustor based on a hybrid of the Reynolds-averaged Navier–Stokes and large–eddy simulation method. The turbulence–combustion interactions were treated using flamelet generated manifold approach. An unstable case was simulated with detailed reaction mechanisms (GRI-Mech 3.0). The obtained results agree well with experiment data from Purdue University, in terms of pressure oscillations frequency and power spectral density spectrum. The combustion instability mode was identified to be coupled with the first longitudinal acoustic mode of the combustion chamber by dynamic model decomposition method. According to Rayleigh index analysis, the unstable driving source was found to be located near the combustor step, which was further confirmed by time-averaged flow fields. Detailed three-dimensional vortex ring shedding evolutions at the combustor step were tracked with fine time resolution. Results indicate that the combustion instability arises from periodic vortex ring shedding at the combustor step and interacting with the chamber wall. The unburnt reactants were rolled up by the shedding vortex ring, which would not break up until impact with the chamber wall. Therefore, the mixing performance was significantly enhanced, leading to sudden heat release. Consequently, the thermal energy is added to the acoustic field, and the first longitudinal mode is thus reinforced, giving rise to large amplitude axial velocity oscillations which prompt the generation of the new vortex ring. The results of the present investigation will support the design and development of high-performance rocket engines.

Thermodynamic and structure properties of aluminum nanoparticle due to heat treatment: a molecular dynamics study

Thermodynamic and structure evolution of Aluminum nanoparticle with diameter of 10 nm are investigated due to heat treatment by means of stepping heat and compared it to sudden heat. Molecular Dynamics (MD) simulation is employed to track the trajectories of each atom and its surrounding to define thermodynamic properties, e.g., temperature and pressure. The temperature evolution gives clear different profile for both cases, while pressure profile strongly evident different mechanism of melting. From thermodynamics point of view, the nanoparticle suffered different final state for both heating methods. Structure analysis later confirmed that for stepping heat the nanoparticle is melted while for sudden heat it is only partially melted.

Knowledge About How to Manage Warning Signs of Pregnancy Complications Among Immigrants and Their Descendants Compared to Women of Danish Origin.

Ethnic differences in perinatal morbidity and mortality are starting points for social inequality in health. Increased incidence and severity of some pregnancy complications are found among immigrant women compared to ethnic majority women in high-income settings. However, little is known about immigrant women's assessment and management of warning signs. We aimed to assess women's knowledge about how to manage warning signs of pregnancy complications among immigrants and their descendants compared to women of Danish origin. A cross-sectional study including phone-based interviews with 1899 women. Women were interviewed during gestational week 30-37 in one of six languages. Maternal ethnicity was categorized as; immigrants, their descendants and ethnic Danes. The outcomes were yes or no to; do you know what to do if you experience 1) sudden swelling, redness, and heat in one leg 2) severe headache and 3) vaginal bleeding. Immigrant women had lower levels of knowledge about how to manage all three types of warning signs of pregnancy complications compared to women of Danish origin. Adjusted OR for vaginal bleeding for women of European (4.33, 95% CI: 2.24-8.37), Asian (9.26, 95% CI: 5.10-16.83) and African (8.66, 95% CI: 3.26-23.05) origin. Immigrant women had lower levels of knowledge about how to manage warning signs of pregnancy complications compared to women of Danish origin. Improved needs-based health education in pregnancy complications and body symptoms during antenatal care is needed to address delays in the management of complications and could potentially improve the health of women and children.

An analysis approach for entropy generation in bounded solids subject to sudden heat flux

This work addresses the problem of entropy generation rate due to conduction for a one-dimensional bounded solid onto which a sudden heat flux is applied from one of its surfaces and the other surface is insulated. A theoretical procedure is presented using the infinite series to solve for temperature distribution with different forms of the applied heat flux. The considered cases include, but not limited to, constant, ramp and sinusoidal types of heat fluxes. The theoretical temperature results are found to be closely matching with those available in literature for one case and with those obtained by the finite element approach for all the cases. Entropy generation rate due to thermal field is presented in all the three cases with the conclusion that an energy balance is attained at some depth below the surface.

An analysis approach for entropy generation in bounded solids subject to sudden heat flux

An analysis approach for entropy generation in bounded solids subject to sudden heat flux

Durian Locule (Endocarp) Water Immersion Drinking Effect to Reduce Heaty Sensation after Flesh Consumption: A Preliminary Study

Durian is said to have a “heaty” effect on the people who have eaten it that can raise their body temperature and blood pressure. The locule water immersion is the water that is drunk using the durian’s inner skin (endocarp) that contains the durian flesh and it is said (mainly via local hearsay) that it can lower the body temperature right after consuming the flesh. The aim of this research is to investigate a myth about the effect of D24 durian locule water immersion that can possibly reduce body temperature after eating durian via oral temperature assessment. In order to explore the reliability of this myth, an experimental research was carried out with five different respondents to undergo with 3 different set of condition which are: a) consumed the same amount of durian, but they did not have to drink the immersed-locule water; b) consumed the durian and they had to drink the immersed-locule water and c) consumed the durian and they had to drink a cup of water. The changes in their body temperature (oral reading) were recorded and analysed for significant changes (n = 3). Overall, the immersed-locule water exhibited a mild affect in the changes of body temperature (p&lt;0.05) on a short period of time (&lt;30 mins after consumption). For that reason, the availability of pectin in the locule water-immersion might have help facilitates the natural homeostasis mechanism faster as to suppress of any sudden body heating after eating durian.

Impact of transportation and rehydration strategies on the physiological responses of clams (Ruditapes philippinarum)

With the prolongation of the post-catch circulation time, the soft tissue of live clam could gradually decline in its quality. This study investigated the quality changes of clams (Ruditapes philippinarum) during the cold chain transportation, and then focused on the rehydration processes, which included gradient heating rehydration (GR) and sudden heating rehydration (SR). Results showed that a higher survival rate of clams was obtained in the GR stage (95%) clams than that in the SR stage (76%). In addition, both glycogen content and adenylate energy charge (A.E.C) value were also higher in the GR stage (20.49 ± 1.05 mg/g, 70.77 ± 1.76%) than that in the SR stage (15.47 ± 1.83 mg/g, 61.63 ± 1.74%) clams. Conversely, the clams in the GR stage showed lower lactic acid content (0.167 ± 0.003 mmol/g) than that in the SR stage (0.181 ± 0.004 mmol/g). Therefore, during the rehydration processes, the GR was a better approach to preserve the quality of clams when compared with the SR. This work could provide reference to preserve the quality of clams and reduce the economic loss of clams during the transportation and rehydration process.

Conjugate heat transfer in the mode of thermal gravitational-capillary convection in the model of a fuel tank, after a sudden heating of the sidewall

The evolution of unsteady gravitational-capillary convection in a layer of ethyl alcohol with a free surface after sudden electric heating of one of the vertical walls of a rectangular cavity was investigated numerically. The effect of the incoming flow of hot liquid on the time evolution of the temperature field on the opposite thin metal wall of the cavity was investigated. The calculations were carried out by the finite element method in the conjugate two-dimensional formulation with the Prandtl number Pr = 16, and the range of Grashof numbers determined by the heat flux density, 33·103 ≤ Gr ≤ 28·106. It is shown that the maximum local temperature gradients occur on the wall near the liquid-gas interface.

Enhanced thermo-tolerance in transgenic potato (Solanum tuberosum L.) overexpressing hydrogen peroxide-producing germin-like protein (GLP)

Germins and germin-like proteins (GLPs) were reported to participate in plant response to biotic and abiotic stresses involving hydrogen peroxide (H2O2) production, but their role in mitigating heat stress is poorly understood. Here, we investigated the ability of a Solanum tuberosum L. GLP (StGLP) gene isolated from the yeast cDNA library generated from heat-stressed potato plants and characterized its role in generating innate and/or acquired thermo-tolerance to potato via genetic transformation. The transgenic plants exhibited enhanced tolerance to gradual heat stress (GHS) compared with sudden heat shock (SHS) in terms of maximal cell viability, minimal ion leakage and reduced chlorophyll breakdown. Further, three StGLP transgenic lines (G9, G12 and G15) exhibited enhanced production of H2O2, which was either reduced or blocked by inhibitors of H2O2 under normal and heat stress conditions. This tolerance was mediated by up-regulation of antioxidant enzymes (catalase, ascorbate peroxidase and glutathione reductase) and other heat stress-responsive genes (StHSP70, StHSP20 and StHSP90) in transgenic potato plants. These results demonstrate that H2O2 produced by over-expression of StGLP in transgenic potato plants triggered the reactive oxygen species (ROS) scavenging signaling pathways controlling antioxidant and heat stress-responsive genes in these plants imparting tolerance to heat stress.

Epidemiology of sudden death in organized school sports in Japan

BackgroundNearly half of the sudden deaths documented in Japanese middle and high school occurred during school organized sport activities. However, no study to date has calculated the incidence rates of these deaths by sport. Therefore, this study aimed to describe the epidemiology of sudden death in organized school sports in Japan.MethodsData submitted to Japan Sport Council (JSC) Injury and Accident Mutual Aid Benefit System between 2005 and 2016 were retrieved from JSC website for analysis (n = 1137). Case information on fatal incidents that occurred during organized school sports in middle and high school students were extracted for analysis (n = 198). Descriptive statistics about activity type, sex, sport, cause of death, and presence of on-site trained medical personnel were calculated using frequencies and proportions. Sudden death incidence rates were expressed per 100,000 athlete-years with 95% confidence intervals (CI).ResultsThe overall incidence rate of sports-related death was 0.38 deaths per 100,000 athlete-years (95%CI = 0.30, 0.45). Only three cases (2%) reported having trained medical personnel on-site at the time of death. Most deaths were in male student athletes (n = 149/162, 92%), with 7.5 times greater fatality rate in male compared to female student athletes (incidence rate ratio, 7.5; 95%CI = 4.43, 13.22). Baseball (n = 25/162, 15.4%), judo (n = 24/162, 14.8%), soccer/futsal (n = 20/162, 12.3%), and basketball (n = 18/162, 11.1%) accounted for 53.7% of deaths. Accounting for the number of participants in the respective sport, the three highest average incident rates of death were reported in rugby (4.59 deaths per 100,000 athlete-years, 95%CI = 2.43, 6.75), judo (3.76 deaths per 100,000 athlete-years, 95%CI = 1.58, 5.93), and baseball (0.59 deaths per 100,000 athlete-years, 95%CI = 0.38, 0.79). The top three causes of death were sudden cardiac arrest (n = 68/162, 42.0%), head trauma (n = 32/162, 19.8%), and heat related injury (n = 25/162, 15.4%).ConclusionsIn conclusion, the highest rates of sports-related death among Japanese student athletes were observed in the following: rugby, male athletes, and during practices. The leading cause of death was sudden cardiac arrest.

Magneto-thermoelastic interactions in generalized thermoelastic half-space for varying thermal and electrical conductivity

Significant variations are observed over the working temperature range of the various engineering problems such as designing the structures heated by sudden heat flux in engineering. At that time, major variations in the coefficient of the thermal conductivity of the material are observed. Electrical conductivity is also found to be directly dependent on the thermal conductivity. Therefore, present problem enlightens the influence of the variable thermal conductivity and electrical conductivity inside a half space medium permeated by the magnetic field in context of dual phase lag thermoelasticity. Thermal shock has been applied to the non-traction boundary of the medium. Analytical solutions are calculated by adopting Laplace transform technique. Physical fields such as conductive temperature, displacement as well stress of the medium are evaluated in time-domain numerically by using a suitable method of numerical inversion of Laplace transform. Further, to predict the utility of the present model, computational results are compared to the corresponding results of heat conduction model with single phase lag (Lord and Shulman model). By examining the numerical results that have been graphically represented, significant differences have been attributable to the studied fields due to the variable thermal conductivity and different heat conduction models.