Allowable Operating Temperature Research Articles

Designs of ultra-HPHT Electrical Component Packages for Downhole and Geothermal Wellbore Logging Tool Integrations

Conventional dielectric sealing materials (PEEK, glass and glass-ceramic) used for sealing electrical feedthroughs, connectors, interconnectors and bulkheads in electronic packages can provide reliable downhole wellbore long-term logging tool service up to 150C or short-term logging service for greater than/equal 200C, due primarily to low glass transition temperature of the used sealing materials. This paper will demonstrate that the maximum allowable operating pressure and temperature could be from 20KSI to 100KSI and from 200C to 400C with Borosilicate and Bismuth-Boron-Silica (XTS) sealing glasses. Borosilicate glass sealed Inconel-Kovar/Kovar electronic housing could maintain reliability up to the maximum pressures of ~35KSI at 200C or 25KSI at 400C. Similarly, a Bismuth-Boron-Silica XTS glass sealed stainless steel electronic package housing could have a maximum operating pressure of ~100KSI at 150C or ~50KSI at 300C temperature. It has been found that high glass transition temperatures of (440-560)C for Borosilicate glass and (44010)C for Bismuth-Boron-Silicate (XTS) glass are key for making highly reliable ultra-HPHT electronic component packages. It is shown that the tetrahedral diamond-like microstructures of these sealing glasses are keys to ensure water-repelling properties to maintain sufficient electrical insulation resistance regardless of their use in water or moisture-rich wellbores. Moreover, compressive pin stress is found to be additional key for mitigate frequently observed glass seal cracks during logging tool field services.

AUTOMATED CALCULATIONS IN THE DEVELOPMENT OF ENERGY-EFFICIENT DESIGNS OF FURNACES FOR ALUMINUM SCRAP REMELTING

The analysis of operational thermal conditions of the furnaces for aluminum scrap remelting is given. It was established that it is necessary to choose refractory materials with aluminum oxide content more than 85 % and the thickness of the thermal insulation should ensure the temperature of the external surfaces not higher than 50 °C when designing the furnaces for lining. On the basis of relevant methods packages of application programs have been developed for design calculations of lining and thermal insulation considering thermal conductivity change of individual layers as a result of their complete or partial impregnation with molten aluminum; calculations of energy balances; the selection of external heating devices with electric or flame heating. The power of the external heat source, the amount of heat spent on heating the scrap to the melting temperature, melting and overheating the melt to the working temperature and heat loss have been taken into account in the energy balance. The heat balance equation is used for determination of the melting time for electrically heated furnaces or the power of burner devices at the desired melting time. In the design calculations, the necessary thicknesses of lining and heat-insulating materials are chosen for all elements of enclosure. With appropriate calculations in dialog mode, it is also possible to change materials and their thickness quickly in case of exceeding the allowable operating temperatures of these materials. Options of using electric tape or wire heaters made of nichrome or EI-626 steel were considered during external heating devices calculations. Flame heating can be implemented using gas burners or liquid fuel nozzles. Further variant calculations based on the developed methods and software made it possible to create a furnace design with a capacity of 600 kW with reduced energy and operating costs for the melting process. Bibl. 14, Fig. 1, Tab. 1.

Experimental study on temperature and performance of an open-cathode PEMFC stack under thermal radiation environment

The open-cathode proton exchange membrane fuel cell stack is an air-cooled stack, and has the characteristics of small footprint and high power density because of its unique configuration, combining oxidizer and coolant via axial fan. Depending on the demands of the application, proton exchange membrane fuel cells inevitably operate in harsh environments, such as high pressure, low or high temperature, etc. In this study, the performance of a 10-cell open-cathode PEMFC stack under thermal radiation was evaluated. The variations in cathode air temperature and relative humidity, stack temperature, output power and single-cell voltage under three different radiant heat fluxes were obtained by changing the load current and cathode air flow rate. The experimental results show that, even if the thermal radiation is beneficial to improve the stack temperature, the stack performance is not improved in all tested cases. Conversely, the degradation of stack power and failure of the stack continuous operation can be observed, especially for higher radiant heat flux, higher load current and lower air velocity. For the highest radiant heat flux in current study, the temperature of the first single cell closest to the radiant heat source exceeds the maximum allowable operating temperature of 65 °C due to the insufficient capacity of air cooling and the heating effect of radiant heat source. The significant drop in the first single-cell voltage results in the rapid degradation of the overall performance of the stack, and finally the stack fails to run continuously.

Technological Justification of the Possibility of Applying Wear-Resistant Coatings to Strengthen Machine Parts

The technology of restoring worn-out engine parts using modern techniques for applying wear-resistant diamond-like (DLC) coatings has been analyzed. To simplify the coating technology and reduce the wear of the highly adhesive deposited layer, applying metal-containing adhesive undercoats has been proposed. The camshaft surface wear types have been studied.The dependence of the change in the oil film thickness in the camshaft -follower contact zone on the cam rotation angle at a rotation frequency of 1,500 rpm is given. The contact causes an unsteady friction surface lubrication mode and intensive wear of the material in the contact zone.To apply a wear-resistant coating, ion etching has been proposed, followed by spattering a tungsten layer with a thickness of up to 10 μm on the product surface with subsequent 20 μm thick tungsten carbide-based coating using microwave plasma. Such a gradient structure over the cross-section of the wear-resistant coating allows achieving the best product performance.The values ​​for the change in surface temperature in the cam-follower friction pair contact zone are given. Nitride, carbonitride, and other types of wear-resistant coatings, their recommended thicknesses, and maximum allowable operating temperatures are given. The hardness of various coatings and possible types of their destruction are shown.The reasons for adhesive and cohesive delamination of wear-resistant coatings are shown, and ways to eliminate this phenomenon are proposed.

Immobilization of phosphonium-based ionic liquid stationary phases extends their operative range to routine applications in the flavor, fragrance and natural product fields

Phosphonium-based ionic liquids (ILs) have proven to be successful stationary phases (SPs) for gas chromatography (GC) in several fields of application because of their unique selectivity and good chromatographic properties. This study focuses on the use of two ILs as GC SPs that are based on the phosphonium derivatives trihexyl(tetradecyl)phosphonium chloride ([P66614+] [Cl−]), and trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]imide ([P66614+][NTf2−]), which have previously been shown to be complementary in terms of chromatographic selectivity and retention. Their application in routine analysis has been limited by their lower maximum allowable operating temperatures (MAOT) (200 °C for the [P66614+][Cl−] IL and 180 °C for [P66614+][NTf2−]), which restricts their use to samples that consist of analytes with relatively high volatility. A previous study carried out in the Authors’ laboratory focused on extending the use of the [P66614+][Cl−] IL SP to the analysis of samples with analytes of medium-to-low volatility by optimizing column characteristics and operative conditions. This study addresses the immobilization of both the [P66614+][Cl−] and [P66614+][NTf2−] ILs to the inner wall of fused silica columns to increase their MAOT under soft and hard reaction conditions. The resulting MAOT depended on more or less drastic immobilization conditions, and reached 220 °C for soft immobilization (So-Im) and 240 °C for hard immobilization (Ha-Im) in the [P66614+][Cl−] IL columns, and 200 °C for So-Im and 220° for Ha-Im in columns coated with the [P66614+] [NTf2−] IL. The influence of immobilization on the separation power and performance of all the columns has been evaluated using i) the Grob test, ii) a model mixture of 41 compounds of different polarity, structure, and with different organic functional groups representative of the flavor and fragrance field, iii) a standard mixture of 37 fatty acid methyl esters, iv) the peppermint essential oil, v) two mixtures of sesquiterpenic alcohols (farnesols and santalols), and vi) a standard mixture of 16 pesticides. These test samples were also used to demonstrate the complementarity of the two phosphonium-based IL SPs in terms of selectivity and retention.

Amphiphilic triblock copolymer as the gas chromatographic stationary phase with high-resolution performance towards a wide range of isomers and the components of lemon essential oil

This work presents the investigation of using the amphiphilic triblock copolymer composed of poly(ethylene oxide)(PEO)-poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) (denoted as EPE) as the stationary phase for gas chromatographic (GC) analyses. The EPE capillary column exhibited moderate polarity and column efficiency of 4348 plates/m determined by naphthalene at 120 °C (k = 11.52). Different from the PEG and polysiloxane homopolymers, it showed high-resolution performance towards a wide range of aliphatic and aromatic isomers in terms of polarity and acid-base properties. Particularly, the EPE column displayed distinct advantages for separating the critical isomers of alkanes, anilines and phenols and the components of the lemon essential oil over the commercial PEG and polysiloxane columns. In addition, the EPE column exhibited excellent separation repeatability and reproducibility with the relative standard deviation (RSD) values in the range of 0.03% – 0.08% for run-to-run, 0.14% – 0.61% for day-to-day and 3.1% – 4.0% for column-to-column, respectively. Moreover, the EPE column was investigated in terms of thermal stability, the minimum allowable operating temperature (MiAOT) and sample loadability. Its application to GC-MS analysis of the essential oil demonstrated its feasibility for practical analyses. This work demonstrates the promising future of triblock copolymers as a new class of selective stationary phases for GC analyses, which is barely reported up to date. The findings of this work is of important value for fundamental researches and practical applications.

High Strain Rate Behavior of GTM-900 Titanium Alloy

Abstract GTM-900 is an α + β alloy of titanium used in low-pressure (LP) compressor blades of gas turbine (GT) engines. The maximum allowable operating temperature of this alloy is 500°C. Silicon is added to enhance the creep resistance at elevated temperatures. The aim of this work is to establish the microstructural stability of this alloy and determine the high strain rate Johnson-Cook (J-C) material parameters such as A, B, and n. The material parameters are subsequently used by designers to simulate the “blade-off” and “casing containment” capability of the LP compressor blade. Split Hopkinson tensile bar was used to conduct high strain rate tests at about 2,000 s−1, and at three different temperatures, viz., 25°C, 300°C, and 500°C, to simulate critical conditions. Data obtained from these testing were used to construct a J-C model. Flow stress increased with an increase in strain rate and decreased with an increase in temperature because of thermal softening. Characterization, using optical and electron microscopes, indicated that the microstructure was stable even after the deformation at 500°C. The presence of needle-like silicide phase was observed under transmission electron microscopy and the composition was verified with X-ray diffraction results. A high strain hardening rate was observed even at elevated temperatures in this alloy (n ≈ 0.54 at 2,000 s−1 and 500°C) compared to Ti-6Al-4V titanium alloy (n ≈ 0.28). Considering good strength and microstructural stability up to 500°C, the present material offers to be an attractive alternate to other contemporary titanium alloys currently used in GT engine applications.

High-performance energy-saving miniature loop heat pipe for cooling compact power semiconductors

A miniature loop heat pipe (mLHP) is developed to cool compact wide bandgap power semiconductors with a high heat flux (≥30 W/cm2) and high allowable operating temperature (≤250 °C) for the first time. Since the mLHP consists of an evaporator (15 × 16 × 3 mm), a condenser (12 × 12.5 × 2 mm), and transport tubes (100 mm), it can be mounted on a small product equivalent to the size of a gaming smartphone. To achieve high heat flux performance, the mLHP uses Shirasu porous glass for the wick and ethanol for the working fluid. Moreover, for the condenser, heat dissipation is enhanced using a thin copper plate (60 × 60 × 0.5 mm), a thin aluminum cold plate (35 × 20 × 3 mm), or a small cooling fan (17 × 17 × 3 mm). When the condenser dissipates heat using the thin aluminum cold plate, the mLHP achieves a maximum heat-transport performance of 15 W (60 W/cm2) in the horizontal attitude. At the maximum heat load, the heat-source temperature, evaporator temperature, and system thermal resistance at 15 W are 249.8 °C, 142.2 °C, and 0.72 °C/W, respectively. Additionally, the heat transfer coefficient of evaporation at the evaporator is approximately 24,000 W/m2/K. The proposed steady-state numerical model is consistent with the experimental results, excluding the condenser part, with a relative error of 7%.

Calculation of the overhead transmission line conductor temperature in real operating conditions

The integration of fluctuating renewable sources, load growth and aging of the current power system is the major reasons for the development of the electric power engineering. Transmission lines are recently facing new technical and economic challenges. The immediate utilization of advanced technologies and modern methods could solve these issues. This study deals with the transmission and distribution of electrical energy with orientation on the calculation of operating temperature on the conductor of transmission line, which is under actual current load. The load of the transmission line is limited with allowable operating temperature. The operating temperature should not exceed the allowable operating temperature because the conductors of the transmission line have mechanical limit from the standpoint of deflection of conductors. The operating temperature as well as operating conditions of the conductor is determined by the type and material of the ACSR conductor. This article aims to propose the suitable calculation methods of the operating temperature of the overhead transmission line conductor in real operating conditions (external weather influences, current loading and corona effect). The originality of this proposed method (by differential equation) lies in considering corona effect. This improves the accuracy of the calculation of the operating temperature of the conductor under real conditions. In this article, the calculations are compared according to methodology of differential equation and methodology described in CIGRE Technical Brochure 601—guide for thermal rating calculations of overhead lines. The methodology of differential equation counts with or without losses by corona. The article also compares these methods of operating temperature during days in various different weather conditions like environment temperature, solar irradiance, wind speed and direction. It was found that under the action of the corona, the temperature of the conductor increases to a small extent.

Can the selectivity of phosphonium based ionic liquids be exploited as stationary phase for routine gas chromatography? A case study: The use of trihexyl(tetradecyl) phosphonium chloride in the flavor, fragrance and natural product fields

Room temperature ionic liquids (ILs) are well established stationary phases (SPs) for gas chromatography (GC) in several fields of applications because of their unique and tunable selectivity, low vapor pressure and volatility, high thermal stability (over 300 °C), and good chromatographic properties. This study is focused on an IL based on a phosphonium derivative (trihexyl(tetradecyl)phosphonium chloride, [P66614+] [Cl−]), previously shown to be suitable as a gas chromatographic SP because of its unique selectivity. In particular, it aims to establish the operative conditions to apply [P66614+][Cl−] to routine analysis of samples containing medium to high volatility analytes with different polarity, organic functional groups and chemical structure. In the first part, the study critically evaluates long term [P66614+][Cl−] column stability and maximum allowable operating temperatures (MAOT). The relatively low MAOT (210 °C) requires the adoption of a dedicated approach for analytes eluting above this temperature based on a suitable combination of efficiency and selectivity, and column characteristics (length, inner diameter and film thickness) and operative conditions. The performance of [P66614+][Cl−] as a GC SP have been validated through the Grob test, a model mixture of 41 compounds of different polarity, structure, and with different organic functional groups in the flavor and fragrance field, a standard mixture of 37 fatty acid methyl esters, some essential oils containing pairs or groups of compounds of different volatility critical to separate in particular peppermint, thyme, oregano, sandalwood and frankincense. The above approach has produced highly satisfactory separations with all of the samples investigated.

Cotton fibres with fine glass flakes–gel paste: a novel matrix-electrolyte hybrid for enhanced power generation and durable operation of fuel cell

Cotton fibres with fine glass flakes (CFGF), a new solid matrix, is reported here for soaking and retaining more electrolyte and water that aids to enhance proton conductivity above that of conventional glass mat-phosphoric acid electrolyte. Further, layering of all inorganic gel paste (GP) electrolytes on CFGF reduces the charge transport resistance, Warburg impedance and diffusion time, and enhances the proton conductivity. The use of sandwiched GP-CFGF-GP hybrid electrolyte in fuel cell offers higher power density, durability and higher allowable operating temperature up to 180 °C.

Ethyl Carbazole-Grafted Polysiloxane as Stationary Phase for Gas Chromatography

In this work, we synthesized ethyl carbazole-grafted polysiloxanes, namely, ECP-9 and ECP-18, which possessed ethyl carbazole contents of 9% and 18%, respectively. The results of thermogravimetric analysis showed that ECP-9 and ECP-18 polymers lost 2% of weight at 365 °C and 380 °C. The minimum allowable operating temperature for the ECP-9 and ECP-18 was 40 °C. In addition, the ECP-9 and ECP-18 columns were thermally stable at 340 °C and 360 °C. The column average efficiencies of ECP-9 were 2306–3090 plates m−1 for a 10 m column and 2594–3438 plates m−1 for a 30 m column. The column efficiencies of ECP-18 were 2497–3428 plates m−1 for a 10 m column and 2829–3700 plates m−1 for a 30 m column. ECP-9 and ECP-18 as stationary phases exhibited moderate polarity based on the McReynolds constants. Given its specific dipole–dipole, dipole-induced dipole, π–π stacking interactions, and hydrogen bond force with solutes, the ECP stationary phases achieved excellent separation for aromatic isomers, substituted benzenes, polycyclic aromatic mixtures, polycyclic aromatic hydrocarbons, and fatty acid esters with satisfactory peak shapes.

An Analysis of Creep Phenomena in the Power Boiler Superheaters

Higher temperatures of the power boiler superheater operation may lead to high strains caused by the creep phenomenon. This paper presents a determination of the maximum allowable operating temperature limited by the creep phenomenon for steam superheater SH3. The calculations are carried out first on the basis of applicable European standards. Then, calculations are performed based on conducted creep tests, a proposed creep model, and a finite element method (FEM) model. A detailed creep phenomenon analysis based on the conducted creep tests shows that stresses that determine the creep process are mainly caused by pressure. Normal stresses resulting from bending are mainly the effect of thermal expansion. These stresses undergo significant relaxation because of creep. The creep phenomenon analysis explains the equations of the European standards. The presented calculations enable estimation of a safe value of the operating temperature which is constant over time. The estimated time of safe operation does not take account of temperature spikes. For this reason, pressure elements working at high temperatures must be inspected regularly to assess their wear state.

One-Dimensional Thermal Analysis Model for Charring Ablative Materials

This paper presents a one-dimensional model for the analysis of the charring ablative materials used in spacecraft thermal protection systems. The numerical method is based on an implicit finite difference formulation of the governing equations written for a system of mobile coordinates that accounts for the possible presence of surface recession. The maximum allowable operating temperature for the adhesive layer of the junction between the heat shield and the substructure is used as a design parameter for determining the minimum heat shield thickness. A case study on the re-entry of the Stardust capsule is presented. The model proposed as a useful dimensioning tool for the preliminary design phase of the heat shields of spacecraft entering the atmosphere. The model was validated through a survey of the literature related to the dimensioning of thermal shields but based on numeric programs of highly representative industrial standards.

Argentation gas chromatography revisited: Separation of light olefin/paraffin mixtures using silver-based ionic liquid stationary phases

Silver ion or argentation chromatography utilizes stationary phases containing silver ions for the separation of unsaturated compounds. In this study, a mixed-ligand silver-based ionic liquid (IL) was evaluated for the first time as a gas chromatographic (GC) stationary phase for the separation of light olefin/paraffin mixtures. The selectivity of the stationary phase toward olefins can be tuned by adjusting the ratio of silver ion and the mixed ligands. The maximum allowable operating temperature of these stationary phases was determined to be between 125°C and 150°C. Nuclear magnetic resonance (NMR) spectroscopy was used to characterize the coordination behavior of the silver-based IL as well as provide an understanding into the retention mechanism of light olefins.

Model Predictive Control of a Steam Methane Reforming Reactor Described by a Computational Fluid Dynamics Model

The present work demonstrates, for the first time, the development of a computationally efficient closed-loop system with a model predictive controller (MPC) where a computational fluid dynamics (CFD) process model is utilized to represent the process behavior. Specifically, we present the development of a MPC and its implementation within the CFD model of a steam methane reforming reactor, which has been developed and validated in our previous work, to create the CFD-based closed-loop system. Initially, we develop an MPC algorithm using a linear approximation of the dynamics based on the CFD data, and implement it within the CFD simulation as a user-defined function. The MPC accounts for the physical limitations (maximum allowable operating temperature of the outer reforming tube wall) of the reactor as a constraint. We demonstrate the application of the developed MPC within the CFD simulations for a set-point change under the influence of a tube-side feed disturbance. The CFD model determines an optimal...

Evaluating the efficiency of thermo-electric conversion of heat from gas combustion in a small-scale system with counterflow heat exchange

The efficiency of thermoelectric conversion of heat from gas combustion was evaluated in a small-scale system consisting of two channels with opposing gas flows and thermocouples located in the separating wall. Combustion occurred in the chamber fed with fresh mixture heated by combustion products through heat-conducting walls of the channel. In the channel walls, there were thermoelectric converters. It has been shown that in this system, the maximum conversion efficiency of heat from gas combustion may be close to the maximum efficiency of thermoelectric conversion calculated by the maximum acceptable working temperature of the hot side of the converter. This conclusion is valid in the case when the adiabatic combustion temperature of the gas mixture is below the maximum allowable operating temperature of the hot side of the thermoelectric converter. The considered system is promising for the burning of low-calorific gas mixtures and does not require additional energy for cooling the cold side of the thermoelectric converter.

Crosslinked structurally-tuned polymeric ionic liquids as stationary phases for the analysis of hydrocarbons in kerosene and diesel fuels by comprehensive two-dimensional gas chromatography

Structurally-tuned ionic liquids (ILs) have been previously applied as the second dimension column in comprehensive two-dimensional gas chromatography (GC×GC) and have demonstrated high selectivity in the separation of individual aliphatic hydrocarbons from other aliphatic hydrocarbons. However, the maximum operating temperatures of these stationary phases limit the separation of analytes with high boiling points. In order to address this issue, a series of polymeric ionic liquid (PIL)-based stationary phases were prepared in this study using imidazolium-based IL monomers via in-column free radical polymerization. The IL monomers were functionalized with long alkyl chain substituents to provide the needed selectivity for the separation of aliphatic hydrocarbons. Columns were prepared with different film thicknesses to identify the best performing stationary phase for the separation of kerosene. The bis[(trifluoromethyl)sulfonyl]imide ([NTf2]−)-based PIL stationary phase with larger film thickness (0.28μm) exhibited higher selectivity for aliphatic hydrocarbons and showed a maximum allowable operating temperature of 300°C. PIL-based stationary phases containing varied amount of IL-based crosslinker were prepared to study the effect of the crosslinker on the selectivity and thermal stability of the resulting stationary phase. The optimal resolution of aliphatic hydrocarbons was achieved when 50% (w/w) of crosslinker was incorporated into the PIL-based stationary phase. The resulting stationary phase exhibited good selectivity for different groups of aliphatic hydrocarbons even after being conditioned at 325°C. Finally, the crosslinked PIL-based stationary phase was compared with SUPELCOWAX 10 and DB-17 columns for the separation of aliphatic hydrocarbons in diesel fuel. Better resolution of aliphatic hydrocarbons was obtained when employing the crosslinked PIL-based stationary phase as the second dimension column.

MEMS 기반 고체 추력기의 마이크로 점화기를 이용한 궤도 열제어

MEMS based solid propellant thruster researched for the purpose of an academic research will be verified at space environment through CubeSat program. For this, the temperature of the MEMS thruster should be within allowable operating temperature range by proper thermal control to prevent the ignition failure caused by ignition time delay and to guarantee the structural safety of the MEMS thruster in the low temperature. In this study, we proposed an effective thermal control strategy, that is to use micro-igniter as a heater and temperature sensor for active thermal control instead of using additional heater. The effectiveness of the strategy has been verified through on-orbit thermal analysis of CubeSats with MEMS thruster.

Tuning the Selectivity of Ionic Liquid Stationary Phases for Enhanced Separation of Nonpolar Analytes in Kerosene Using Multidimensional Gas Chromatography

In this study, a series of ionic liquids (ILs) are evaluated as stationary phases in comprehensive two-dimensional gas chromatography (GC × GC) for the separation of aliphatic hydrocarbons from kerosene. IL-based stationary phases were carefully designed to evaluate the role of cavity formation/dispersive interaction on the chromatographic retention of nonpolar analytes by GC × GC. The maximum allowable operating temperature (MAOT) of the IL-based columns was compared to that of commercial IL-based columns. Evaluation of the solvation characteristics of GC columns guided the selection of the best performing IL-based stationary phases for the resolution of aliphatic hydrocarbons, namely, trihexyl(tetradecyl)phosphonium tetrachloroferrate ([P66614][FeCl4]) and trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate ([P66614][FAP]) ILs. The best performing [P66614][FeCl4] IL-based column exhibited a MAOT of 320 °C, higher than the commercial SUPELCOWAX 10 (MAOT of 280 °C) and commercial IL-based columns (MAOT up to 300 °C). The structurally tuned [P66614][FeCl4] IL stationary phase exhibited improved separation of aliphatic hydrocarbons by GC × GC compared to the commercial columns examined (e.g., OV-1701, SUPELCOWAX 10, SLB-IL60, SLB-IL100, and SLB-IL111).