Thermal Equilibrium Time Research Articles

Calorimetric Measurements of a High-Power RF Signal

Development of a high-power RF signal meter based on the method of calorimetric measurements, which in some cases is the only possible one is presented. The device is as a system of elements exchanging either energy or information, the operation and interconnection of which ensures the stability of its functioning. The main elements of the device are: a coordinated load and a two-circuit water-air cooling system that convert RF energy first into thermal electrical energy, and then into internal energy of the coolant (working fluid). The measurement and control system provides information display on the monitor and generation of internal control signals. The work focuses on the process of converting electromagnetic energy into internal energy of the coolant, since the matched RF load is integrated into the cooling system and requires special design and technological solutions to ensure efficient operation. A cooling and measurement system has been designed to test the developed RF absorber with a power of up to 5 kW. The parameters of the cooling system were determined based on minimizing the time to achieve thermal equilibrium (time to establish readings) and the set parameters (input temperature no more than 35 °С, temperature difference no more than 40 °С). Based on calculations of the electrodynamic model constructed by the partial domain method, the geometric dimensions were determined at which the voltage standing wave ratio of the load in the operating frequency range (from DC to 1300 MHz) will be the smallest. The article presents the results of designing a high-frequency wattmeter cooled by a liquid (water), examines the thermophysical processes occurring in it and the influence of the presence of a coolant in the cooling circuit.

Amphibious Hybrid Laser Tweezers for Fluid and Solid Domains.

Optical trapping is a potent tool for achieving precise and noninvasive manipulation of small objects in a vacuum and liquids. However, due to the substantial disparity between optical forces and interfacial adhesion, target objects should be suspended in fluid environments, rendering solid contact surfaces a restricted area for conventional optical tweezers. In this work, by relying on a single continuous wave (CW) laser, we demonstrate an optical manipulation system applicable for both fluid and solid domains, namely, amphibious hybrid laser tweezers. The key to our system lies in modulating the intensity of the CW laser with duration shorter than the dynamic thermal equilibrium time within objects, wherein strong thermal gradient forces with ∼6 orders of magnitude higher than the forces in optical tweezers are produced, enabling moving and trapping micro/nano-objects on solid interfaces. Thereby, CW laser-based optical tweezers and pulsed laser-based photothermal shock tweezers are seamlessly fused with the advantages of cost-effectiveness and simplicity. Our concept breaks the stereotype that CW lasers are limited to generating tiny forces and instead achieve ultrawide force generation spanning from femto-newtons (10-15 N) to (10-6 N). Our work expands the horizon of optical manipulation by seamlessly bridging its applications in fluid and solid environments and holds promise for inspiring optical manipulation techniques to perform more challenging tasks, which may unearth application scenarios in diverse fields such as fundamental physical research, nanofabrication, micro/nanorobotics, biomedicine, and cytology.

Research on thermal mass flowmeter (TMF) measurement of coalbed methane (CBM) well production profile.

Developing coalbed methane (CBM) aligns with global climate change policies and sustainable energy development. Currently, methods for testing gas and water production profiles in CBM wells are diverse. A downhole constant-flow thermal mass flowmeter (TMF) was designed to address the difficulty of testing gas production above the liquid level in low-yield CBM wells. A computational fluid dynamics model with a 125mm diameter pipe was established to study the TMF's temperature field and thermal equilibrium time as the gas flow rate changes. The relationship curve between temperature, thermal equilibrium time, and flow rate changes was obtained. The effect of the TMF's installation angle and position in the wellbore on resolution was discussed. Experimental research on a multiphase flow simulation apparatus showed that the TMF has good response capability and testing accuracy in a gas environment. Measuring downhole flow rates using the thermal flow meters is feasible and meets the testing requirements of CBM wells.

Thermal equilibrium time as a novel characteristic of nanofluid evaluation: An experimental investigation of distilled water-based binary and ternary nanofluids

Nanofluids enhance thermal energy transfer in energy storage applications. Proper nanoparticles are crucial, especially regarding their thermophysical properties. This work fabricated a novel instrument to evaluate a mixture of distilled water-based ternary and binary nanofluids. This work prepared novel ternary and binary nanofluids by mixing multi-wall carbon nanotubes (MWCNTs), magnesium oxide (MgO), and boron nitride (BN) into distilled water at various volume concentrations. The instrument that has been fabricated measures the time taken by the nanofluids to reach a thermal equilibrium state as a new characteristic to evaluate and compare the thermal potential of nanofluids, which alleviates the dependence on other instruments that are occasionally inaccessible or costly for researchers. Thermodynamically, this instrument enables the assessment of nano-energy, manifested as the heat transferred to the nanofluid while reaching an equilibrium state. The results verified the purpose of the proposed instrument; the novel characteristic was affected perfectly by increasing the volume concentration of the nanoparticles in the base fluid. All nanofluids prepared with a concentration of 0.5 % emerged as the most effective in achieving thermal equilibrium in a shorter time than the other concentrations. The ternary hybrid nanofluid MWCNTs–MgO–BN with a volume concentration of 0.5 % had the shortest thermal equilibrium time, 157 s. MWCNTs–MgO–BN ternary hybrid nanofluids transferred 8.3, 5.8, and 11.8 % more heat than MWCNTs–MgO, MWCNTs–BN, and MgO–BN binary hybrid nanofluids. The thermophysical essence behind the result obtained by the created instrument lies in the fact that it generated a new approach to evaluating the nanofluids, thanks to which it was possible to evaluate and find out which fluid has the highest thermal conductivity. The uncertainty analysis showed error acceptability in the experimental instrument, with an average uncertainty value percentage for all presented composites of ± 0.936 %.

Temperature-insensitive FDL-stabilized laser using a PMF-based dual interferometer.

We demonstrate a temperature-insensitive fiber-delay-line-stabilized (FDL-stabilized) laser based on a dual Mach-Zehnder interferometer (MZI) by using polarization maintaining fibers (PMFs). Two orthogonal polarization components of a beam are simultaneously transmitted in the interferometer. Each polarization component exhibits a unique phase shift in response to the changes in temperature, forming a dual MZI. One of the heterodyne signals is used to lock the laser frequency, while the other one is used to compensate the frequency change induced by the temperature fluctuation. The experiment shows that the laser frequency fluctuation has been suppressed at least 25 times. This is an effective method to reduce the laser frequency noise induced by the temperature fluctuation of the FDL. In this way, a compact system with less thermal shields can be realized, and the thermal equilibrium time could be decreased dramatically.

Design and implementation of a temperature-compensated corrector magnet power supply for the Taiwan Photon Source

The Taiwan Photon Source (TPS) is a widely recognised 3 GeV synchrotron light source. It has demonstrated exceptional performance in average beam downtime and meeting international standards over its successful ten-year operation. Regular equipment updates are conducted for all subsystems to ensure continuous improvement and maintain an optimal research facility environment. This study focuses on designing and implementing a temperature-compensated corrector magnet power supply for the TPS. The power supply incorporates a high-bandwidth, compact, cost-effective, bipolar, and highly precise shunt resistor as the current feedback component. A temperature control copper box and temperature compensation circuit are employed to improve the thermal equilibrium time of the output current. A laboratory-developed TPS-corrected magnet power supply with temperature compensation control has been successfully developed through these measures. The prototype exhibits a maximum output current of 10 A and operates at a voltage of 40 V. Metal-oxide-semiconductor field-effect transistors (MOSFETs) are utilised as the power switch in a full-bridge (H-bridge) configuration with a driving frequency of 40 kHz. The output current ripple is effectively maintained at 100 μA for a 10 A output, and the stabilisation time is achieved within 5 minutes. The control loop design of the prototype has been verified to achieve fast and stable output current performance. The completed prototype demonstrated a -3 dB bandwidth of 2.57 kHz when tested with an input reference signal of 0.1 V. Finally, a hardware prototype circuit was constructed in the power supply laboratory, featuring an input voltage of 48 V, an output current of 10 A, and a maximum power capacity of 400 W.

Novel smart plugging material for high‐temperature gas well

AbstractA novel smart material is developed, which is synthesized by succinic anhydride, epoxy resin, and zinc acetylacetone hydrate. The smart material has excellent properties of self‐healing, shape memory, and degradation. The experimental results of performance characterization show that the material has good thermal stability. The glass transition temperature is adjustable between 100 and 120°C, and the storage modulus can reach 20 GPa. The maximum thermal expansion at 50°C is less than 15%, the thermal expansion equilibrium time at 120°C is less than 5 min, and the maximum thermal expansion is 131%. The stress relaxation time at 120°C is more than 2 h, which can slowly self‐heal on the basis of maintaining the mechanical strength. When the NaOH content is 1.5%, the degradation equilibrium can be reached in about 3 h, and the maximum degradation rate is 86%. The comprehensive performance evaluation shows that after hot rolling at 120°C/16 h, the material has no effect on the rheology and filtration properties. When plugging the fracture width of 5 × 4 mm, the pressure bearing capacity reaches 10 MPa. Its main mechanism is temperature‐sensitive expansion, and the stress relaxation effect heals and blocks the micro pore throat.

Prediction of thermal errors in a motorized spindle in CNC machine tools by applying loads based on heat flux

The thermal errors of a motorized spindle are seen as a source of significant errors in computer numerical control (CNC) machine tools, and motion errors, geometrical errors, among others, that are consequences of the thermal errors in the spindle. A predictive model of the thermal errors of a motorized spindle is proposed using a loading method based on heat flux. At first, a finite element model for the steady-state and transient thermal-structure coupling analysis of a motorized spindle is established, in which the loading method based on heat flux is adopted to assign the total amount of heat to the ball, an inner race, and an outer race of angular-contact ball bearing proportionally. The response values of sample points are obtained by simulation, and then a response surface model for the prediction of the steady-state elongation of the spindle thermal deformation under the influences of four factors including rotational speed of a bearing, coolant temperature, ambient temperature, and preload is constructed. The simulation and experimental results indicate that predictive error of the steady-state elongation of the spindle thermal deformation is only 3.81 μm, and the thermal equilibrium time in the transient thermal-structure coupling analysis is almost same to the experimental result. The response surface model can predict steady-state errors arising from the changes in working conditions and corresponding changes of the spindle.

Feedback control of the mechanical spindle thermal error based on thermal simulation with bearing heat sources analysis

The thermal error stability (STE) of the spindle seriously affects the machining accuracy of a machine tool, however existing empirical heating model-based active cooling strategies mainly focus on suppressing the spindle’s overall thermal deformation and cannot effectively stabilize the thermal error. This study regards the “active cooling-spindle” system as a feedback control system and employs a data-driven thermal error model to provide feedback. Thus, the spindle thermal error can be stabilized for a long time owing to the homeostasis of the feedback control system under disturbance. A mechanical spindle with an external cooling scheme is taken as the study object. Bearings are the primary heat sources of the mechanical spindle; thus, the angular contact ball-bearing heat generation is precisely modeled based on local heat sources analysis of bearing components, elastohydrodynamic lubrication, and micro-contact theory. Thermal simulation of the spindle under varying-coolant temperature cooling is conducted to pre-validate the thermal error suppression and variation trend influencing effect, and obtain the Reference Input of Thermal Error (RITE) for the feedback control under different work conditions. Subsequently, a spindle thermal error feedback control system is developed, including computation, cooling, and real-time monitoring modules with inter-communication. Finally, the thermal error feedback control strategy is applied on the mechanical spindle, and experimental comparisons with constant coolant temperature cooling show that the thermal equilibrium time is advanced by 61.46%, 59.16%, 40.51%, and 58.08%. The thermal error variation range (TEVR) after the preheating stage is reduced to1.92, 1.52, 1.91, and 1.69 μm, respectively. The significant reduction in TEVR validated the effectiveness of the proposed strategy for spindle thermal error stabilization.

Temperature field analysis and structure redesign of fiber optic gyroscope

Taking the fiber ring of the core device of the fiber optic gyro as the research object, the temperature field simulation analysis of the fiber gyroscope was carried out by ANSYS finite element analysis software, and the structural optimization of the fiber gyroscope was carried out, which effectively improved the temperature field distribution uniformity of the fiber optic ring and reduced the overall thermal equilibrium temperature and time when the fiber gyro reached stability.

Look-ahead prediction of spindle thermal errors with on-machine measurement and the cubic exponential smoothing-unscented Kalman filtering-based temperature prediction model of the machine tools

Reducing the thermal equilibrium time is one effective way to improving the efficiency and utilization and ensuring the accuracy of machine tools. This paper proposed the look-ahead prediction of spindle thermal errors based on CES-UKF temperature prediction model using on-machine measurement. It can predict the thermal errors during the warm-up stage just with the measured temperature data in the required on-machine measurement time (ROMT). With the thermal error compensation function, the machine tool only needs warm-up for ROMT to improve the efficiency and ensuring the accuracy of machine tools. The look-ahead temperature prediction is realized combining UKF and CES including real-time adjustment of exponential smoothing coefficients and ROMT calculation. Temperature-sensitive point selection based on self-attention mechanism is established. Gate recurrent unit (GRU)-based thermal error model is proposed considering the thermal hysteresis effects. Verifications and cutting experiments are carried out to testify the effectiveness and robustness of the method.

Thermodynamics of hydrogen sulfide adsorption in NaX zeolite

Sulfur-containing organic and inorganic compounds are the main harmful component of natural gas and oil, as well as products of their processing. Since sulfur compounds have acidic properties, their content leads to corrosion of technological parts in production processes. The content of hydrogen sulfide in the transported gas should not exceed 20 mg/m3. In Uzbekistan, motor vehicles run mainly on liquefied natural gas. Sulfur compounds in natural gas corrode gas cylinders, resulting in an explosion. If synthetic zeolites are used in manufacturing processes, as well as in small gas production, process degradation will be prevented. Synthetic zeolites are widely used in various industrial production processes due to their high sorption properties. This study makes it possible to study the localization and sorption structure of sulfur compounds in supercavities of zeolites of the faujasite type. The adsorption of hydrogen sulfide on NaX zeolite was carried out in a high vacuum adsorption unit. Based on the results obtained, the differential heat of adsorption, isotherm, entropy, and thermal equilibrium time (thermokinetics) were calculated.

Thermodynamics of hydrogen sulfide adsorption in Zeolite LiX

Sulfur compounds adversely affect the technological process of oil and gas refining, as well as the release of sulfur-containing compounds into the atmosphere, polluting the environment. Oil and gas processing is carried out using microporous adsorbents with high sorption capacity in the purification of gases containing sulfur. This is one of the most efficient methods in oil refining and gas processing. In research work, the adsorption of gases containing sulfur in their composition is carried out in various ways. When determining the formation complex, the main centers of Li-ionic molecules, it was possible to obtain a more accurate idea of the adsorption mechanism at the stages of absorption of hydrogen sulfide molecules into Li-zeolites using a highly sensitive adsorption calorimeter. In our study, in the process of adsorption of hydrogen sulfide on the LiX zeolite, the results of differential adsorption heat, isotherm, entropy, and thermal equilibrium time (thermokinetics) based on obtained in a high vacuum adsorption device are accurately revealed. Based on exact formulas, it was proved how many hydrogen sulfide molecules are adsorbed in the zeolite that died under vacuum conditions.

Thermodynamics of hydrogen sulfide adsorption in Zeolite Lix

Sulfur compounds adversely affect the technological process of oil and gas refining, as well as the release of sulfur-containing compounds into the atmosphere, polluting the environment. Oil and gas processing is carried out using microporous adsorbents with high sorption capacity in the purification of gases containing sulfur. This is one of the most efficient methods in oil refining and gas processing. In research work, the adsorption of gases containing sulfur in their composition is carried out in various ways. When determining the formation complex, the main centers of Li-ionic molecules, it was possible to obtain a more accurate idea of the adsorption mechanism at the stages of absorption of hydrogen sulfide molecules into Li-zeolites using a highly sensitive adsorption calorimeter. In our study, in the process of adsorption of hydrogen sulfide on the LiX zeolite, the results of differential adsorption heat, isotherm, entropy, and thermal equilibrium time (thermokinetics) based on obtained in a high vacuum adsorption device are accurately revealed. Based on exact formulas, it was proved how many hydrogen sulfide molecules are adsorbed in the zeolite that died under vacuum conditions.

Theoretical and experimental study on rotating heat pipe towards thermal error control of motorized spindle

The thermal equilibrium time (TET) is extremely long, and the thermal elongation (TE) is obvious because the heat dissipation performance (HDP) is weak and the temperature gradient is significant for the high-speed motorized spindle (HSMS). Aiming at the above problems, a new rotating heat pipe (RHP) is designed towards the HSMS cooling and thermally induced error (TIE) control according to the working condition and geometric size constraint of the HSMS, and the theoretical and experimental studies are conducted on the designed RHP. To verify the heat transfer performance (HTP), the gas-liquid phase transition model is established for the designed RHP. A new test platform is constructed to simulate the actual service condition of the RHP and measure its HTP, and the experimental study is carried out for the designed RHP to get the optimal design parameters of the RHP. The temperatures and HTP obtained by the gas-liquid phase transition model agree well with the measured data. Finally, the designed RHP is embedded into the HSMS to increase the HDP and control the TIE. The fluid-thermal-solid interaction characteristic (FTSIC) models are established for the HSMS with the RHP and traditional fluid-cooled HSMS (FCHSMS) without the RHP. The results show that the designed RHP is effective to realize the HSMS cooling and TIE control, and finally the designed RHP and established FTSIC models are verified by carrying out the thermal behavior experiments.

Influence of Evotherm on the thermal equilibrium time of unmodified and modified bituminous binders

ABSTRACT The rheological properties of bitumen largely influence the performance of the pavement. Determination of rheological properties of bitumen depends on thermal equilibrium time. The main objective of this study is to evaluate the effect of Evotherm, a chemical warm mix additive on the thermal equilibrium time of bituminous binders. The bituminous binders used for this study included two unmodified binders, a polymer-modified bitumen (PMB) and a crumb rubber-modified bitumen (CRMB). The thermal equilibrium times for bituminous binders with and without Evotherm were measured using a dynamic shear rheometer. The results indicate that the thermal equilibrium time primarily depends on the type of binder, wherein the asphaltene content, presence of polymer and rubber influence thermal equilibrium time. The higher thermal equilibrium times observed for the Evotherm-modified PMB40 binder and Evotherm-modified CRMB60 binder in unaged condition can be attributed to a change in morphology and chemical interaction respectively upon the addition of Evotherm. Lesser thermal equilibrium time exhibited by short-term aged Evotherm binders can be because of the reduced formation of ageing compounds due to reduced short-term ageing temperature and presence of Evotherm. The linear regression model well predicted the thermal equilibrium time based on test temperature and softening point of binders.

Feedback control–based active cooling with pre-estimated reliability for stabilizing the thermal error of a precision mechanical spindle

The thermal error stability (STE) of the spindle determines the machining accuracy of a precision machine tool. The “active cooling-spindle” system is regarded as a feedback control system, and the data-driven thermal error model is utilized to output feedback. In this way, the spindle thermal error can be stabilized by the homeostasis ability of the feedback control system under disturbance. Structural temperature measurements are considerably interfered by the active cooling, so the regression models trained with experimental data might output inaccurate feedback in unseen work conditions. Such inaccurate feedbacks are the primary cause for excessive fluctuations and failures of the thermal error control processes. The independence of the thermal data is analyzed, and a V-C (Vapnik–Chervonenkis) dimension–based approach is presented to estimate the generalization error bound of the regression models. Then, the model which is most likely to give acceptable performance can be selected, the reliability of the feedback can be pre-estimated, and the risk of unsatisfactory control effect will be largely reduced. Experiments under different work conditions are conducted to verify the proposed strategy. The thermal error is stabilized to be within a range smaller than 1.637 μm, and thermal equilibrium time is advanced by more than 78.3%.

Improved unscented Kalman filter algorithm-based rapid identification of thermal errors of machine tool spindle for shortening thermal equilibrium time

Thermal equilibrium of machine tools is needed before machining to ensure the accuracy. To shorten the warm-up time and improve the machining efficiency, a rapid identification of thermal errors is proposed. It can predict the thermal errors in the shortest identification time so that the thermal error compensation can be started in advance to shorten the thermal equilibrium time. A Singular Value Decomposition-Adaptive Unscented Kalman Filter algorithm (SVD-AUKF) is proposed with singular value decomposition and adaptive rule for the fast identification. A general exponential thermal error model is established and applied into the SVD-AUKF. RMSE of the thermal error data within each time is calculated for the evaluation to obtain the shortest identification time. K hysteresis rule, Δt judgment rule and maximum time rule are proposed for the prediction accuracy. Different experiments are proposed with two machine tools to testify the effectiveness of the shortest identification time.

Contact heat transfer analysis between mechanical surfaces based on reverse engineering and FEM

In engineering application, analyzing the temperature field of structures is often necessary. The contact surface is constituted by the superposition of different scales of rough surfaces because it is not completely smooth. When heat is transferred between these two contact surfaces, the surfaces are in incomplete contact, and a temperature difference is formed on the contact surface. The non -smooth contact surface also delays the thermal equilibrium time in numerical simulation. In this paper, the W-M fractal function is used to reconstruct the rough surface of the experimental plate according to its profile parameters, then the nonuniform B-spline global surface interpolation method is used to aid the construction of a 3D surface that could keep the true shape of the plate to the greatest extent, and the 3D rough surface with the same size as the experimental plate is reconstructed by reverse engineering. Finally, the heat transfer characteristics of non-smooth contact are simulated and analyzed by using the finite element method, and verified by experiments. Experimental and simulation results show that the actual contact area of the plate is about 7.09% of the nominal contact area. The research method in this paper can be utilized to study not only the heat conduction characteristics of the contact surface but also engineering problems such as friction and wear of the contact surfaces.

Research on improved hydrostatic guideway base thermal characteristics by flattening temperature distribution

This paper proposed a new guideway base structure of hydrostatic guideways to flatten its spatial temperature variation characteristics. Four oil storage holes penetrating through the base are used to collect the hydraulic oil, which is heated by power losses after oil flows through the bearing clearances. When the heated oil flows into the four oil storage holes, the whole base is warmed and temperature distribution non-uniformity is avoided. In order to verify the effectiveness of the new structure, a physical model of the guideway base simplified from actual base was developed. A thermal model of a guideway base was developed using the finite element method (FEM). The temperature distribution of guideway bases was calculated, taking into account the temperature-dependent heat transfer coefficients of interfaces and thermal contact conductances. Analysis of temperature differences, thermal equilibrium time, and temperature uniformity of bases demonstrates the effectiveness of the new base design on its thermal characteristics and improves structural parameters. The experimental results verify the accuracy of the thermal model hydrostatic guideway bases.