•Hybrid sol-gel coatings have been investigated with the non-destructive technique.•Thermal parameters of these thin coatings were determined depending on their composition.•Optical photoacoustic ...method was applied for experimental investigations.•Two layer model of the samples was used for interpretation of experimental results.
This work presents results of studies of thermal parameters such as thermal diffusivity, thermal conductivity, thermal effusivity and volumetric heat capacity of thin hybrid sol-gel corrosion protective layers deposited on the aluminum substrate. In the studies two groups of samples were investigated. The first group was: TMZ.1, TMZ.2 and TMZ.3 (TMZ- Si/Zr-based hybrid sol-gel coatings), with different amount of zirconium, and the second group was: TMZ.1/Ce, TMZ.2/Ce and TMZ.3/Ce (TMZ/Ce - Ce-doped Si/Zr-based hybrid sol-gel coatings) with the same amount of zirconium and an addition of cerium. This work presents the influence of the content of zirconium and cerium on their thermal parameters. The possibility of using the nondestructive photoacoustic method (PA), with the microphone detection, to characterize this type of layers was analyzed theoretically and experimentally too.
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The energy output from a combined cycle power plant (CCPP) varying with the operating thermal parameters like ambient pressure, vacuum, relative humidity, and relative temperature is modelling using ...different approaches. The huge data obtained from the experimental readings is found to be highly non-linear using the data visualization technique. The energy output from the CCPP reduces linearly with the temperature and non-linearly with pressure. A mathematical model is developed for the predictions of the energy output. Modelling using sequential API and functional API based artificial neural network (SANN and FANN) having single hidden layer is carried out. Finally, energy output modelling using sequential API and functional API based deep ANN (SDNN and FDNN) is also performed. The residuals of the predicted and experimental observations indicate that the error is acceptable and it lies uniformly above and below the regression line. The R-squared value of the mathematical model is 0.93 and 0.94 during training and testing. The obtained R-squared value of the ANN and DNN using sequential and functional API is 0.94. The training and testing of all the models are successful and these models have shown a great compatibility in predicting the energy output of a CCPP. The ANN model with single layer and deep layer has no difference in accuracy hence the former one is recommended as it is computationally less expensive.
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This paper presents an equivalent winding model of a small and medium permanent-magnet synchronous motor. The model considers fill factor and void ratio. To verify the model, two winding samples are ...made. One is annular and adopts ordinary enameled wires. The other is circle but adopts self-adhesion wires. Temperature rises of the winding samples supplied with different current densities are tested. The calculated and tested results were compared. The equivalent winding model is also used for the temperature calculation of a 6-pole/9-slot permanent magnet synchronous motor. The influence of fill factor and void ratio on the temperature rise of the motor is investigated, as well as two overload short time states are compared. Comparing with ignoring the effect of the void ratio, the winding temperature estimation error reduces about 5 °C. Finally, winding temperature rises of a prototype are tested. The results can provide some references for choosing a reasonable current density and improving the accuracy of motor temperature estimation.
The dielectric behavior of stearic acid in 1,4-dioxane medium at various temperature 303 K–288 K and frequency regime (10 MHz–30 GHz) determined from the complex dielectric permittivity spectra ...obtained by Time Domain Reflectometry(TDR). In this frequency range, the dielectric study gives the electrostatic interaction as well as orientational polarizability of complex mixtures of long chain molecules significantly. Dielectric parameters were calculated from the complex spectra of the binary mixture by non linear least square fit method. The excess permittivity (εE), correlation factors were calculated for the binary system. Thermal parameters(ΔH-enthalpy, ΔS-entropy and ΔG-Gibbs free energy) were calculated and the direction of reaction is determined. The FTIR spectrum of the binary system recorded and the assignments are discussed. The FTIR spectral assignments confirm the molecular interactions.
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•Dielectric dispersion studies revealed the interaction between amphiphilics(stearic acid) and non-polar solvent(1,4-dioxane).•Static dielectric constant variation with concentration and temperature ensure the molecular interaction.•Relaxation dynamics revealed frequency, temperature dependent molecular interaction and Critical Micelle Concentration (CMC) formation.•Excess permittivity values of the mixture validate the solute-solvent molecular interaction.•The FT-IR absorption intensity varies with solvent concentration confirms the molecular interaction and CMC formation extensively.
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•Considered occupancy indicators: CO2 concentration and computers power consumption.•Accurate occupancy time is estimated from CO2 concentration in low occupancy rooms.•Increments of CO2 ...concentration showed bad performance identifying room occupancy.•Computer power consumption gave accurate occupancy patterns and number of users.•Agreement of results from 1month and 7years data evidences robustness of results.
This paper reports on various options for estimating room occupancy levels in an office building from the results of testing, and aims to find an efficient way to represent this occupancy, optimizing accuracy, cost effectiveness and the intrusiveness of measuring, which is very useful for commercial applications.
CO2 concentration and computer electricity consumption were considered alternative indicators of occupancy level. Advantages and drawbacks of both indicators are discussed.
In both cases, ranges when the room was positively empty and when it was positively occupied were identified. This study is based on histograms that represent indicator measurements in each of those ranges during the study period. Afterwards, the ranges identified were used to find room occupancy patterns. Information previously available about the rooms, such as typical work hours, and lunch hours, holidays, weekends, etc., when rooms are empty were used to validate the results.
Data were from a seven-year series acquired while the building was in regular use. The first analysis considers all of these available data making results robust. Accuracy with shorter experimental test periods was also studied.
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Temperature heavily affects the behavior of any energy storage chemistries. In particular, lithium-ion batteries (LIBs) play a significant role in almost all storage application fields, including ...Electric Vehicles (EVs). Therefore, a full comprehension of the influence of the temperature on the key cell components and their governing equations is mandatory for the effective integration of LIBs into the application. If the battery is exposed to extreme thermal environments or the desired temperature cannot be maintained, the rates of chemical reactions and/or the mobility of the active species may change drastically. The alteration of properties of LIBs with temperature may create at best a performance problem and at worst a safety problem. Despite the presence of many reports on LIBs in the literature, their industrial realization has still been difficult, as the technologies developed in different labs have not been standardized yet. Thus, the field requires a systematic analysis of the effect of temperature on the critical properties of LIBs. In this paper, we report a comprehensive review of the effect of temperature on the properties of LIBs such as performance, cycle life, and safety. In addition, we focus on the alterations in resistances, energy losses, physicochemical properties, and aging mechanism when the temperature of LIBs are not under control.
In this work, a LiFePO4/graphite lithium-ion pouch cell with a rated capacity of 45Ah has been used and a two dimensional thermal model is developed to predict the cell temperature distribution over ...the surface of the battery, this model requires less input parameters and still has high accuracy.
The used input parameters are the heat generation and thermal properties. The ANSYS FLUENT software has been used to solve the models. In addition, a new estimation tool has been developed for estimation of the thermal model parameters. Furthermore, the thermal behavior of the proposed battery has been investigated at different environmental conditions as well as during the abuse conditions. Thermal runaway is investigated in depth by the model.
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This paper concerns fault diagnosis of centrifugal compressor based on thermal parameters. An improved qualitative simulation (QSIM) based fault diagnosis method is proposed to diagnose the faults of ...centrifugal compressor in a gas-steam combined-cycle power plant (CCPP). The qualitative models under normal and two faulty conditions have been built through the analysis of the principle of centrifugal compressor. To solve the problem of qualitative description of the observations of system variables, a qualitative trend extraction algorithm is applied to extract the trends of the observations. For qualitative states matching, a sliding window based matching strategy which consists of variables operating ranges constraints and qualitative constraints is proposed. The matching results are used to determine which QSIM model is more consistent with the running state of system. The correct diagnosis of two typical faults: seal leakage and valve stuck in the centrifugal compressor has validated the targeted performance of the proposed method, showing the advantages of fault roots containing in thermal parameters.
•Thermal parameters of centrifugal compressor are used for fault diagnosis.•Improved qualitative simulation based fault diagnosis method is proposed.•Qualitative models under normal and two faulty conditions are built.•The qualitative trends of variables' observations are extracted online.•A sliding window based model matching strategy is applied for fault diagnosis.
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The knowledge of the thermal properties of materials is a key resource for the correct design of industrial components. The laser flash method is a well-known procedure to determine the thermal ...diffusivity of a wide range of materials. However, in some cases there is the need of limiting the input power, or measuring materials with high thermal capacity, or investigating thick samples. Under these circumstances, the expected signal-to-noise ratio can reach extremely low values. To solve this issue, the existing laser flash apparatus has been improved, creating a new control and data acquisition system that is able to repeat multiple times the emission of the laser impulse and the measurement of the thermal response of the specimen. This gives the possibility of averaging several measurements, leading to a decrease of the noise. The experimental validation on different samples shows the feasibility of the proposed setup, that makes it possible to work with low power inputs.
This paper presents a optimization design method on the compression ratio of the compression process and the expansion ratio of the expansion process for the compressed gas energy storage system ...using carbon dioxide as the working fluid. On this basis, from the thermal parameter perspective of the stage design, compression ratio/expansion ratio design, and compression heat temperature, the thermal characteristics are analyzed using round-trip efficiency and heat storage efficiency as measurement indicators, and a better design scheme for energy-saving and efficiency improvement is obtained. The results show that it will have a positive role in the improvement of the system performance with a three-stage compression-three-stage expansion design structure, an un-equal compression ratio-equal expansion ratio design scheme, and a compression heat temperature of 388.15K. In addition, the round-trip efficiency is up to 74.07% and the heat storage efficiency is up to 51.95%, which has good thermal performance and energy-saving effect for the energy storage system.
•A optimization design method on the compression ratio and the expansion ratio is posed.•A design scheme for energy-saving and efficiency improvement is obtained.•Sensitivity analysis is conducted on the energy storage system.•Comparative analysis of different design schemes are discussed.
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