Temperature Steady State Research Articles

Temperature management during cytoreductive surgery with hyperthermic intraperitoneal chemotherapy.

In addition to attaining complete or near complete cytoreduction, the instillation of select heated chemotherapeutic agents into the abdominal cavity has offered a chance for cure or longer survival inpatients with peritoneal surface malignancies. While the heating of chemotherapeutic agents enhances cytotoxicity, the resulting systemic hyperthermia has been associated with an increased risk of severe hyperthermia and its associated complications. Factors that have been associated with an increased risk of severe hyperthermia include intraoperative blood transfusions and longer perfusion duration. However, the development of severe hyperthermia still remains largely unpredictable. Thus, at several institutions, cooling protocols are employed during cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). Cooling protocols for CRS-HIPEC are not standardized and may be associated with episodes of severe hyperthermia or alternatively hypothermia. In theory, excessive cooling could result in a decreased effectiveness of the intraperitoneal chemotherapeutic agents. This presumption has been supported by a recent study of 214 adults undergoing CRS-HIPEC, where failure to attain a temperature of 38° C at the end of chemo-perfusion was associated with worse survival. Although not statistically significant, failure to maintain a temperature of 38° C for at least 30 minutes was associated with worse survival. Although studies are limited in this regard, the importance of maintaining a steady state of temperature during the hyperthermic phase of intraperitoneal chemotherapy administration cannot be disregarded. The following article describes the processes and physiological mechanisms responsible for hyperthermia during CRS-HIPEC. The challenges associated with temperature management during CRS-HIPEC and methods to avoid severe hypothermia and hyperthermia are also described.

Building Heat Load Estimation Method Including Parameter Estimation from Actual Data

In recent years, various method of air conditioning control and making operation plans have been developed. They require a building thermal model, but for making the model detailed design data is needed. Several model construction methods have been proposed up to now, but they are for buildings surrounded by walls made with one material. In this situation for deriving the room temperature and air conditioner power consumption, a parameter estimation method for estimating heat capacities and resistances of walls with different physical properties was developed. This method consists of two steps. At the first step, in steady temperature state, the least‐squares method is used to derive thermal resistances. In the second step, in non‐steady temperature state, an Unscented Kalman Filter (UKF) is used to derive heat capacities and solar‐radiation shading coefficients. UKF is adopted for numerical stability and short operation time. With this method, it is possible to obtain the independent parameters of each wall by repeating the evaluation using a simple model. These steps were applied to data obtained by simulation. As a result, the physical parameter error of the inner and outer walls was sometimes 10–60%. On the other hand, regarding to the estimation target, the error of the indoor temperature estimation was 0.3 °C, and the error of power consumption estimation was less than 4%, so high estimation accuracy was obtained. This confirmed the effectiveness of the proposed method. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Условия теплового взрыва в пластине при конвективно-радиационном теплообмене

The processes of obtaining and storing energy-saturated substances are characterized by energy release in their volume. The intensity of this energy release increases with increasing temperature. The stability of the stationary temperature state of a solid with a temperature-dependent intensity of volumetric energy release is directly related to the conditions of heat transfer of this body with the environment. If the heat energy released in the volume of the body can no longer be diverted into the environment, the steady temperature state of the body becomes impossible. The paper studies the conditions for a thermal explosion in a solid in the form of a plate with a temperature-dependent coefficient of thermal conductivity and convective-radiation heat transfer on its surfaces. The statement of the nonlinear problem of steady-state thermal conductivity in the plate is represented by a system of integral relations. The limits of integration of the integrals included in these relations are the desired functions and parameters which determine the temperature state of the plate. A quantitative analysis of these relationships makes it possible to establish the influence of the parameters which determine the intensity of heat transfer and the dependence of the thermal conductivity of the plate material on the conditions for a thermal explosion with an arbitrary law of variation with temperature of the volumetric power of the energy release in the plate. The results of such an analysis are presented in the framework of a one-parameter model of the stationary theory of thermal explosion

Material properties of normal and high strength aluminium alloys at elevated temperatures

Aluminium alloys are being used widely in multiple engineering applications. However, the material properties of aluminium alloys could change significantly at high temperatures. This paper studied the mechanical properties of normal strength aluminium alloy 6063-T5 and high strength aluminium alloy 6061-T6 at elevated temperatures. Tensile tests were conducted at room temperature (24 °C) and high temperatures up to 600 °C. Both steady temperature state tests and transient temperature state tests were used. The yield stress (i.e., 0.2% proof stress), the ultimate stress, the Young's modulus, and the ultimate strain were determined from tests. The measured material properties at different temperatures are compared with the predictions by the American and European specifications. A series of unified equations for calculating the reduction factors of the material properties at high temperatures are proposed herein; they are found to yield more accurate reduction factors for aluminium alloys.

Excitation of thermal dissipation of solid propellants during the fatigue process

By using the infrared thermographic method, a non-destructive testing technique was applied to detect the surface-temperature evolution of solid propellants during strain-control fatigue tests within finite cycles. When the applied strains were below the viscoelastic limit, two stages of temperature variation were observed before the initiation of macroscopic cracks: an initial temperature-increase stage, and a steady temperature state. Thermodynamic analysis was carried out and a method was developed to allow the acquisition of stored energy at different stages of cyclic loading, which can reflect the material damage on the macroscopic scale. In addition, temperature localization during fatigue was observed, which implied the occurrence of damage accumulation and crack propagation. The results reveal that the cyclic-loading induced temperature increase of solid propellants during the fatigue process has a significant effect on solid rocket motors in a transportation or storage state.

Variational Approach to the Thermal Explosion Model Analysis in a Solid

A temperature state of the solid body may depend both on the conditions of heat exchange with external environment surrounding its surface and on the energy release within the body volume, caused, for example, by the processes in nuclear reactor elements or exothermic chemical reactions, absorption of penetrating radiation energy or transformation of a part of the electrical power into heat with flowing electric current (so-called Joule heat). If with growing temperature the intensity of bulk power density increases, a limited steady temperature state can emerge at which heat extracted to the body surface and released within its volume reaches maximum. Thus, small increments of temperature lead to an increase of heat release, which can not be extracted to the body surface by conduction without further temperature increase. As a result, the steady temperature distribution in the body becomes impossible that determines the state of the thermal explosion, so named due to the fact that in this case the appropriate mathematical model predicts an unlimited temperature increase. A lot of published papers and monographs concerning the study of the combustion and explosion processes in a stationary medium analyse the thermal explosion state. The most famous papers consider a mathematical model to describe a temperature distribution in the case when heat release is because of exothermic chemical reactions the rate of which increases with temperature growth. The dependence of the chemical reaction rate on temperature is usually described by the exponential Arrhenius law, which makes it necessary to consider an essentially nonlinear mathematical model containing differential equation, which includes the term, nonlinearly rising with increasing temperature. Even with simplifying assumptions, this model allows an exact closed form solution only in the case of one-dimensional temperature distributions in the two areas of the canonical form: in the plate, infinite in its plane, and in the circular cylinder unlimited in length. An approximate numerical solution of the differential equation that is included in a nonlinear mathematical model of the thermal explosion enables us to obtain quantitative estimates of combination of determining parameters at which the limit state occurs in areas of not only canonical form. A capability to study of the thermal explosion state can be extended in the context of development of mathematical modeling methods, including methods of model analysis to describe the thermal state of solids. To analyse a mathematical model of the thermal explosion in a homogeneous solid the paper uses a variational approach based on the dual variational formulation of the appropriate nonlinear stationary problem of heat conduction in such a body. This formulation contains two alternative functional reaching the matching values in their stationary points corresponding to the true temperature distribution. This functional feature allows you to not only get an approximate quantitative estimate of the combination of parameters that determine the thermal explosion state, but also to find the greatest possible error in such estimation.

Modeling and analysis of transient temperature field in finite thickness plate under symmetrically located moving heat sources

The thermal problem of plate slides against symmetrically located contacting pads is investigated. The aim is to find out the influences of plate thickness, moving speed, and convection on the temperature field of the plate. Proper models and computing methods for specific situations can be determined based on these analyses. Finite element method of moving heat input is used to calculate the temperature field which is validated by comparing with some existing analytical solutions. The results show that the characteristic time for the steady state of temperature can be approximated exponentially as a function of moving speed. If the plate is thinner than the critical thickness, the surface temperature is increased significantly, which means that the temperature field is very sensitive to the plate thickness in this situation. The increasing moving speed increases the peak surface temperature almost linearly, and the convection outside of the contact area can decrease the peak surface temperature significantly if the heat sources move slowly, while it hardly affects the peak surface temperature if the heat sources move fast. Based on these results, the criterion of choosing a model and computing methods for studying the temperature fields in the similar structures is established.

Optimization of heat flow analysis for exceeding hundred watts in HI-LEDs projectors

This study conducted a heat flow-lighting performance test to evaluate and analyze an exceeding hundred watts of HI-LEDs (higher-power LEDs) projector. In addition, a Windows-based optimization program was developed to optimize the heat sink of the HI-LEDs projector. The results indicated that the maximal LED temperature of the projector was 108°C at a steady temperature state (approximately 1h of operation). When the metal-core printed circuit board (MCPCB) of the projector was replaced with a vapor-chamber PCB (VCPCB), the LED temperature decreased to 87.6°C. Iterative calculations were subsequently performed using the self-developed Windows-based optimization program for determining the optimal fin interval (8.94mm) and thickness (2.56mm). These optimal parameters were simulated using CFD (computational fluid dynamics), and the results were compared with those of the original 150-W HI-LEDs projector. A Rayleigh number of 6.1304×105 was obtained, indicating a laminar flow model. When the optimized heat sink was used, the LED temperatures for the MCPCB and VCPCB HI-LEDs projector samples decreased by 14 and 9.74°C, respectively. The h value of the optimized HI-LEDs projector (8.094W/m2k) was higher than that of the original HI-LEDs projector (7.154W/m2k), and its weight was reduced by approximately 2%.

Creep transition stresses of a thick isotropic spherical shell by finitesimal deformation under steady state of temperature and internal pressure

Creep stresses for a thick isotropic spherical shell by finitesimal deformation under steady state temperature and internal pressure have been derived by using Seth?s transition theory. Results are depicted graphically. It is seen that shell made of incompressible material require higher pressure to yield as compared to shell made of compressible material. For no thermal effects, the result are same as given by Gupta, Bhardwaj, Rana and Hulsurkar [1,3] and Bhardwaj, Bailey [2,4].

Electrode Potentials of a Silver-Silver Chloride Electrode vs. Temperature for Biosensors

The aim of this study is to make clear the effect of temperature on the potentials of silver-silver chloride(Ag-AgCl) electrodes in potassium chloride(KCl) and sodium chloride(NaCl) solutions for micro biosensor applications. Non-isothermal coefficients, or thermal coefficient of Ag-AgCl electrodes in the concentrations of 0.1 to 1.0[mol/kg] were experimentally measured in the range of 15 to 45[°C]. The electrode was prepared by electrolytical process in KCl or NaCl solutions. The length and diameter of the electrode are 20[mm] and 3[mm], respectively. The coefficients in KCl solutions were 0.42[mV/°C] in 0.1[mol/kg] and 0.26[mV/°C] in 1.0[mol/kg] and almost the same in NaCl solutions. Isothermal coefficients were also measured. Although the coefficients must theoretically be zero by definition for all temperatures, the difference of potentials between a pair of electrodes which is called as offset voltage appears practically. They were 3∼4[μV/°C] in 0.1[mol/kg] and 0.3[μV/°C] in 1[mol/kg] at the steady state of temperature. The values were depending on the degree of the uniformity of electrode surface.

FEM stress analysis and sealing performance improvement of box-shaped bolted flanged joints using silicone sealant under internal pressure and thermal conduction conditions

Interface stresses and sealing performance of thin-wall box-shaped bolted flanged joints using silicone sealant under internal pressure and thermal conduction conditions are analyzed by the thermo-elastic finite element method. The flexible flanges were fastened by M8 bolts and nuts with an initial clamping force (bolt preload) after being joined with the silicone sealant. In the elastic and thermo-elastic Finite Element Method (FEM) calculations, the effects of the bolt pitch distance, flange rigidity and flange thickness were examined on the interface stress distributions. In addition, the effects of the linear thermal expansion coefficient and Young's modulus of the silicone sealant in the steady temperature state were also examined from a design standpoint. In the experiments, leakage pressure was measured when the silicone sealant was applied between an aluminum flexible flange with 1 mm thickness and an aluminum flange (body) with 10 mm thickness. Measurements of sealing performance with the silicone sealant and a sheet gasket were also conducted. In addition, strains in the joint in steady temperature states were also measured by strain gauges to understand the effect of the operative temperature on the sealing performance. The experimental results were found to be in fairly good agreement with the calculated results. From the results, it was found that the effect of the thermal conduction condition was greater than that of the internal pressure on both the interface stress distributions and the sealing performance. In addition, the sealing performance was found to be better in the joint with the silicone sealant than that with the sheet gasket.

A New Theoretical Approach to Steady State of Temperature Modulated Heat Flux DSC

The steady state of temperature modulated heat flux DSC, in which the sample temperature is controlled at a fixed frequency, a fixed amplitude and a constant underlying heating rate, is theoretically investigated for complex heat capacity of the sample, taking accounts of heat capacities of heat paths, heat loss to the environment and mutual heat exchange between the sample and the reference material. Rigorous and general solutions for the temperature difference oscillation are obtained in relation to the sample temperature as a reference oscillation. The results are quite different from those obtained in functions of the heat source temperature as a reference oscillation. From these solutions, application of the technique to heat capacity measurements is discussed.

On the thermal stresses of an infinite plate with two circular inclusions under the steady state of temperature (Case of an infinite plate containing a pair of heat sources)

In this paper, we consider the problem of thermal stresses in an infinite plate with two circular inclusions. The steady state of temperature is induced by a pair of heat sources (positive and negative sources) placed on the x-axis. The analysis is developed by Airy's stress function in the case of generalized plane stress and by applying the bipolar coordinates. The method of perturbation is adopted for the determination of the unknown coefficients involved in the solution. Numerical calculations of the stress distributions along the main parts of the infinite plate and the inclusions are worked out in some detail. The maximum stresses on the common boundaries are also calculated and compared with the available results.

On the Thermal Stresses of an Infinite Plate with an Infinite Row of Circular Inclusions unber the Steady State of Temperature : Case of an Infinite Plate Having an Infinite Row of Pairs of Heat Sources

In the present paper, we consider the problem of thermal stresses in an infinite plate with an infinite row of circular holes which are filled with elastic inclusions of another material. The steady state of temperature is induced by the infinite row of pairs of heat sources (positive and negative sources) periodically placed on either side of the infinite row of inclusions. The analysis is developed by the Airy's stress function in the generalized plane stress. In the construction of temperature and stress functions, periodical harmonic functions are utilized as the fundamental stress function. The successive approximation is adopted for the numerical determination of the unknown coefficients involved in the solution. Moreover, numerical calculations about the stress distributions along main parts of the infinite plate and the inclusions are worked out in some detail, in order to clarify the effects of an infinite row of circular inclusions.

Thermomechanical Coupling Behavior of Viscoelastic Rods Subjected to Cyclic Loading

The problem of longitudinal oscillation of a viscoelastic rod of finite length including the effect of thermomechanical coupling has been studied. The material is assumed to be thermorheologically simple. The almost steady oscillation superposed on a slowly varying temperature distribution permits representation as a boundary-value problem which is solved numerically by iterative procedures. Calculations are made for different stress levels and frequencies. It is found that the temperature increases considerably after a length of time of vibration although the stress level is low. A steady state of temperature can be reached if the temperature at one end of the rod is fixed and a radiation boundary condition is prescribed at the other end.

Transient K.V.P. and r Output from an Air-cooled Therapy Tube

IT is the purpose of this paper to call attention to a little known X-ray tube phenomenon which, while possibly not very important once it is understood, can cause considerable bewilderment if it is encountered without a knowledge of its explanation. The phenomenon takes place in any air-cooled therapy tube during the heat-ing-up period of operation (while the anode and glass of the tube are coming to a steady state of temperature). Even though the primary voltage and milliamperage, or peak kilovoltage and milliamperage, are kept constant, it makes itself known by a changing r output. Since air-cooled therapy tubes are now developed to the point at which they can be used at full voltage without first going through a long warming-up process, the transient during this period, unless taken into consideration, can be a source of error in dosage large enough to be significant writh present-day methods of measurement. Data Data on both kenotron and mechanically rectified equipment show that operation of an air-...