K-type Thermocouples Research Articles

Low-cost portable system for measuring thermal conductivity of building

The developed system allows to measure the thermal conductivity of solid materials used as thermal insulators in building bioclimatic houses on high Andean zones. A unidirectional heat flow model through a sample of dimensions 4.0 cm x 4.2 cm x 1.35 cm has been considered. K-type thermocouples were used to measure the temperature’s gradient. The obtained values were: 0.97 Wm−1°C−1 for glass, 0.38 Wm−1°C−1 in the ignimbrite, 0.58 Wm−1°C−1 for the roof brick and 0.34 Wm−1°C−1 in the adobe with Stipa ichu. These materials have been evaluated considering their abundance and use in house building on the Arequipa department high zones.

Deep Neural Network Based Linearization and Cold Junction Compensation of Thermocouple

In this proposed work, temperature sensors, namely, a thermocouple and thermistor were linearized using deep neural networks. The deep feedforward neural network (DFNN) technique was proposed to linearize the K-type thermocouple’s output, in the given temperature range −100 °C to 1372 °C, while nonlinearity was reduced from 2.03% to 0.002% full scale span (FSS). Deep layer recurrent neural network (DLR-NN) was used to reduce the nonlinearity of a negative temperature coefficient (NTC) thermistor from 84.63% to 0.13% FSS. The linearized thermistor was used for cold junction compensation (CJC) of the thermocouple. In both the thermocouple and thermistor, linearization was achieved in a single stage for a wide range digitally using deep neural networks alone. There were no analog pre-signal conditioning circuits, unlike the existing neural network-based linearization techniques in literature. A hardware setup of a stand-alone module for linearization was designed using the Raspberry pi microcontroller consisting of two soft modules, one for thermocouple linearization and the other for thermistor linearization. The proposed system was experimentally tested using a K-type thermocouple on a thermal calibrator in a 0 °C–300 °C range. The cold junction compensated output of the thermocouple had a maximum absolute error of 0.34 °C when ambient temperature varied from 0 °C to 40 °C. The results were satisfactory and better than the existing National Institute of Standards and Technology (NIST) standard. This linearization technique can be extended to other thermocouple types as well as other nonlinear sensors.

Microprocessor temperature control device for a thermal object

The article deals with a device for temperature control of a thermal object. The device is based on a single-chip AVR ATmega32 microcontroller. There are two modes of temperature regulation. The first is designed for temperature regulation within the range of -55 ° C to +125 ° C, and the second is from +126 ° C to +1000 ° C. The first range uses a DS18B20 digital serial output temperature sensor. The temperature measurement resolution in the first temperature range of -55 °C to +125 °C is 0.0625 °C. The second range uses a K-type thermocouple and a MAX6675 thermocouple signal converter with I2C interface. The discreteness of temperature measurement in the range from +126 C to +1000 C is 2 C. The microprocessor based controller has a very wide temperature control range from -55 to +1000°C, which is well within the temperature range required by the process. In the first area, due to high accuracy digital temperature sensor DS18B20, the resolution is very good ±0.0625 °C, which enables the use of the controller in climate control systems.

ПРЕЦИЗИОННАЯ ЛАБОРАТОРНАЯ ПЕЧЬ ДЛЯ ПОЛУЧЕНИЯ НАНОЧАСТИЦ С СИСТЕМОЙ ПРОГРАММНОГО УПРАВЛЕНИЯ И ОБЛАЧНЫМ МОНИТОРИНГОМ

Introduction: The development of a precision reaction furnace with a microprocessor control system based on an IoT class ESP-8266 microcontroller and a K-type thermocouple is presented. The temperature in the furnace hearth is maintained in the range from 50 to 350 °C with an accuracy of 1%. The temperature compensation of the cold junction of the thermocouple is provided. To improve the contro-accuracy and adjust the controller parameters, a reference mathematical model is used. Methods: a procedure for identifying the parameters of the reference model using the least squares has been developed. Regulator settings eliminate the occurrence of overshoot or fluctuations in the transient. A mode for monitoring the temperature and current power of the heater with visualization and logging of telemetry data to the cloud service (Telegram bot) has been implemented. Results: a mobile application implemented on a smart phone allows you to remotely receive temperature data and control the operating modes of the furnace. The duration of the experiment is actually not limited, the continuous operation of the furnace was tested on an interval of 24 hours. For high temperatures, in order to preserve the crucible, a mode of automatic stepwise heating and cooling is implemented. The furnace allows chemical reactions to be carried out at high temperatures in stabilization or program control modes, including decomposition reactions or the synthesis of nanoparticles from copper and other metals.

Thermal conductivity of hybrid fibre reinforced concrete under varying temperature

The Small closely spaced and uniformly dispersed fibres in concrete greatly improve its mechanical and fire-resistant properties. This paper deals with experimental investigation of the performance of Hybrid Fibre Reinforced Concrete (HFRC) with carbon and steel wool fibres under different elevated temperatures. Five different fibre volume fractions between 0 and 1% were selected. The concrete cube specimens were casted with five combinations of carbon fibre (CF) and steel wool fibre (SW) and cured. The concrete cube specimens were exposed to three different temperatures (400 °C, 600 °C, 800 °C) and the thermal conductivity of the concrete cube specimen were measured using K-type thermocouple. Temperature exposed specimens were tested for compressive strength and compared with control specimen. The compressive strength of temperature exposed HRFC cube specimens are reduced due to the degradation of the cube specimen. The compressive strength test results were compared with control specimen to find the optimum fibre proportion in HFRC.

Cutting force & thermal analysis during turning using Ansys

In metal cutting, the magnitude of the cutting forces and temperature at various interfaces is the function of the cutting process variables. These cutting process variables directly affect production. Therefore, more research on this topic and further development will lead to improved production. Experimental work was conducted under dry machining with heat-treated 4140 Alloy Steel workpiece and the cutting tool was Cast Steel Silver Brazed Carbide were used under turning process. In this experimentation, during the machining the cutting forces were measured using Tool-Lathe Sharp Techno Dynamometer and the temperature measurement was done employing two techniques that were K-Type Thermocouple for the tool temperature and Infrared Thermometer for the tool chip contact area temperature. In this research, Finite Element Analysis (FEA) methodology was used, with cutting forces and temperatures at the different points of the cutting tool as an input. Model of the Single Point Cutting Tool (SPCT) was generated using Solid Works software and the analysis was done in Ansys (Workbench) software. The Ansys software analyzed the Single Point Cutting Tool (SPCT) model by FEA and results obtained are discussed in this study.

Pengujian Eksperimen Pembuang Panas dan Aliran Udara Pada Berbagai Bentuk Heatsink

Heatsinks are widely used in heat exchangers to increase the rate of heat transfer between a surface and the working fluid. This study aims to determine the effect of surface shape and area, and air flow velocity on the rate of heat transfer of the three different heatsinks. The research was conducted experimentally by testing three forms of heatsinks with variations in air flow velocity in a small windtunell. The windtunnel is equipped with test equipment such as a handheld wind meter, K-Type thermocouple and a stopwatch. The heating source for the three model heatsinks is an electric heater that can reach a heating temperature of 100oC. Air flow velocity is varied from 0.5 m/s, 1.0 m/s and 1.5 m/s. The results of this experiment show that the heat dissipation rate is directly correlated with the air flow velocity and the heat transfer surface area. At flow velocities of 0.5 m/s, 1.0 m/s and 1.5 m/s, the air temperature behind the heat sink (T2) is 62.8oC, 56.7 oC, and 52.4 oC, respectively. From the heat calculation results show that the shape of the heatsink -model 3- dissipates heat higher than others where the surface area is much larger. For a flow velocity of 0.5 m/s, the rate of heat dissipation generated in model 1, Model 2 and model 3 are 26875 J/s, 34449.01 J/s and 37686.19 J/s, respectively. Keywords: Heat dissipation, surface model, air flow and heatsink.

CHARACTERIZATION OF WELD HEAT INPUT EFFECTS ON MECHANICAL PROPERTIES OF Cr-Mo STEEL BAR USING TIG WELDING PROCESS

Welding as an energy-consuming process is inevitable as-welded joint can be subject to various loads without failure. Therefore, this paper presents the welding thermal cycle of Cr-Mo steel bar (ASTM A304) of dimensions 100 by 50 and various thicknesses of 5, 10- and 15-mm. Pure tungsten with 2% thoriated TIG electrodes sizes 1.6 mm X 175 mm, 2.4 mm X 175 mm, and 3.2 mm X 175 were used without filler materials for the welding process. A double V-groove weld joint, with a moving heat source, was employed to determine the temperature fields and transformation in the single-pass butt-welded joint. A calibration process was attached at each point of interest using a datalogger type K-type thermocouple 3-channel–LU-MTM-380SD during the welding process on the Cr-Mo steel bar. The results showed that the welding temperature became higher at the welding centreline and decreased towards the edges of the bar. An indication that a weld thermal cycle is a veritable tool, a function of heat input to access likely consequence of the welding process at both welded and parent metal portions of steel bar. Design of Experiment using Taguchi L9 orthogonal array matrix L9(3^4), Factors:4 and Runs:18 in Minitab 17 Taguchi Design Method that suited the experimental method used. Taguchi’s L9 orthogonal array to restrict the number of experimental runs was used for the design of the experiment (DOE). Mechanical and Microstructure tests were carried out on the samples to investigate the effect of weld heat input. The hardness test result showed that samples C15 and D15 have the highest hardness values 165.0HV and 164.0HV respectively at Base metal (BM) 20mm away from weld centreline and it was also observed that samples C15 and D15 have the highest impact values 48.53J and 48.7J respectively. The microstructure of the C15 at the weld zone WZ, which consists majorly of pearlite and less ferrite, BM shows the appearance of alpha ferrite and pearlite and heat-affected zone HAZ consists majorly of pearlite and a very small proportion of ferrite resulted in increased hardness and impact values at the HAZ.

Experimental and Numerical Analysis of Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets.

The refill friction stir spot welding (refill FSSW) process is a solid-state joining process to produce welds without a keyhole in spot joint configuration. This study presents a thermo-mechanical model of refill FSSW, validated on experimental thermal cycles for thin aluminium sheets of AA7075-T6. The temperatures in the weld centre and outside the welding zone at selected points were recorded using K-type thermocouples for more accurate validation of the thermo-mechanical model. A thermo-mechanical three-dimensional refill FSSW model was built using DEFORM-3D. The temperature results from the refill FSSW numerical model are in good agreement with the experimental results. Three-dimensional material flow during plunging and refilling stages is analysed in detail and compared to experimental microstructure and hardness results. The simulation results obtained from the refill FSSW model correspond well with the experimental results. The developed 3D numerical model is able to predict the thermal cycles, material flow, strain, and strain rates which are key factors for the identification and characterization of zones as well for determining joint quality.

Thermal changes during drilling in human femur by rotary ultrasonic bone drilling machine: A histologic and ultrastructural study.

Undue heat production in surgical bone drilling leads to osteonecrosis and can be an important cause of failure of osteosynthesis, impaired healing, and loosening of implants following orthopedic surgery. The present work aims to minimize heat production below the critical temperature for thermal osteonecrosis (i.e., 47°C) and obviate thermal bone damage due to drilling. A total of 20 samples from the shaft of the human femur were obtained at autopsies and drilling was performed at room temperature by an operation theater (OT) compatible rotary ultrasonic bone drilling (RUBD) machine. K-type thermocouples were used to measure the temperature rise during drilling and the physical changes of the bone samples were observed by infrared gama camera. Light microscopic and transmission electron microscopic studies were performed to evaluate the bone cell damage. The maximum temperature recorded in RUBD (40.6 ± 1.3°C) was much below the critical temperature for thermal osteonecrosis (p < .05) at the rotational speed of 2000 rpm. Light microscopic and ultrastructural studies also revealed that there was no appreciable damage to the bone cells. Conventional bone drilling (CD) on the other hand recorded much higher temperature (66.6 ± 3.2°C), tissue burn and bone cell necrosis. Hence, RUBD machine has a potentiality for its use in orthopedic surgery and may provide better results.

The effect of operating parameters on the heat transfer in the heat pipe

Heat pipes are a good solution for temperature stabilization, for example, of microelectronics, because these kinds of systems are without any moving parts. Experimental research of the effect of operating parameters on the heat transfer in a cylindrical heat pipe has been conducted. The effect of the working fluid properties and the porous layer thickness on the heat flux and temperature difference in the heat pipe has been investigated. The temperature field of the heat pipe has been investigated using the IR-camera and K-type thermocouples. The data obtained by IR-camera and K-type thermocouples have been compared. It is demonstrated the power transferred from the evaporator to the condenser is a linear function of the temperature difference between them.

Investigating the effect of sensible and latent heat storage materials on the performance of a single basin solar still during winter days

A passive solar still combined with a heat storage system was developed and used for desalination of brackish water. The experimental setup mainly consists of an insulated rectangular basin, filled with 19 kg of saline water, painted black and installed south-facing onto the flat roof of a building located in the Meknès city (Latitude: 33°53′36′′ North; Longitude: 5°32′50′′ West). The device was equipped with K-type thermocouples which were connected to a data logger and laptop computer in order to measure and record different temperatures.Emphasis focused on the influence of winter (2020) ambient conditions and storage materials (air, sand and paraffin wax) on the thermal efficiency and pure water productivity of the desalination system. Weather conditions of winter days (sunny, cloudy, rainy, windy, warm, cold) significantly impact the yield of solar still. Heat is stored (or retrieved) as sensible heat for sand unlike paraffin wax (Phase Change Material: PCM) which stores/retrieves heat in both modes: sensible and latent. Temperature melting of the PCM was not reached for unfavorable weather conditions (rainy, cloudy and windy days). The sensible heat storage/retrieval mode is predominant while the latent mode appears for a short period (about 25 min). Latent heat storage mode allows storing a huge amount of heat (> 1 MJ), hence the using of heat storage system (sand and paraffin wax) enhances the overall thermal efficiency by 152.8 and 223.09%, respectively, compared to conventional solar still. In conclusion, a solar distiller coupled with a heat storage system is a promising technology for desalination in arid and semi-arid regions which are confronting to a severe scarcity of fresh water as the same time they have abundant amounts of brackish water.

Improvement of Thermal Performance of Coiled Tube Heat Exchanger Utilizing Air Bubble Injection Technique

The heat transfer enhancement in terms of temperature of a vertical helically coiled tube heat exchanger is carried out experimentally. The experiments were achieved in a heat exchanger with a 50 cm height and 15 cm internal diameter under four different cold and three hot water mass flow rates and four different airflow rates. At the same time, the temperature difference was taken invariant (ΔT=20°C). To avoid some uncertainties, the hot side temperature of the heat exchanger was measured via k-type thermocouples. The results showed that the increase of air injection flow rate improved heat transfer from the hot stream flowing in the coil to the shell’s cold stream. An intimate thermal mixing when air injected is clearly observed, which could be responsible for the heat exchanger’s thermal enhancement. Finally, the injected air pressure was noticed to be having only a minor effect on thermal performance improvement.

The cooling performance of halogenated alkane fire extinguishing agent and its quantitative prediction model

The halogenated alkane fire extinguishing agent inhibits a flame by the utilization of both physical and chemical effects. The cooling performance is an important physical index for various fire extinguishing agents to suppress a fire and prevent re-ignition. Fire extinguishing agent with high cooling performance is of great necessity and need to be developed urgently. However, a profound understanding of quantitative cooling performance for traditional fire extinguishing agents is still unavailable. Presently, a series of experiments are performed to study the quantitative cooling performance of traditional fire extinguishing agents. The test facilities consist of thermocouples, a nozzle, a fire agent tank, a hot plate, and a data acquisition device. The fire extinguishing agents are comprised of FC 114B2 (C2F4Br2), BTP (C3H2BrF3), CFC 13B1 (CBrF3) and HFC-227ea (C3HF7). During the experiments, the temperature change of the hot plate is recorded and averaged by five K-type thermocouples. It indicates that BTP shows a good cooling performance through the analysis of experimental data. A dimensionless model is proposed to predict the cooling performance based on physical parameters and finally verified using two refrigerants, HFC-32 (CH2F2) and HFC-134a (C2H2F4). It provides a potential method for developing and screening the new fire extinguishing agent with high cooling performance.

Pre-Heating Effect on Monomer Elution and Degree of Conversion of Contemporary and Thermoviscous Bulk-Fill Resin-Based Dental Composites

Detection of unreacted monomers from pre-heated resin-based dental composites (RBC) is not a well-investigated topic so far. The objectives were to determine the temperature changes during the application and polymerization, the degree of conversion (DC) and unreacted monomer elution of room temperature (RT), and pre-heated thermoviscous [VisCalor Bulk(VCB)] and high-viscosity full-body contemporary [Filtek One Bulk(FOB)] bulk-fill RBCs. The RBCs’ temperatures during the sample preparation were recorded with a K-type thermocouple. The DC at the top and bottom was measured with micro-Raman spectroscopy and the amounts of eluted BisGMA, UDMA, DDMA, and TEGDMA were assessed with High-Performance Liquid Chromatography. The temperatures of the pre-heated RBCs decreased rapidly during the manipulation phase. The temperature rise during photopolymerization reflects the bottom DCs. The differences in DC% between the top and the bottom were significant. RT VCB had a lower DC% compared to FOB. Pre-heating did not influence the DC, except on the bottom surface of FOB where a significant decrease was measured. Pre-heating significantly decreased the elution of BisGMA, UDMA, DDMA in the case of FOB, meanwhile, it had no effect on monomer release from VCB, except TEGDMA, which elution was decreased. In comparison, RBC composition had a stronger influence on DC and monomer elution, than pre-cure temperature.

Effects of Seasonal Temperature Variation on Slurry Temperature and Biogas Composition of a Commercial Fixed-Dome Anaerobic Digester Used in Bangladesh

Biogas is produced in Bangladesh mostly through fixed-dome anaerobic digesters, which usually operate without any temperature controller. An experiment was conducted to monitor the seasonal temperature variation inside a fixed-dome type digester and its effect on biogas composition. A commercial-scale digester with a working volume of 350 m3 was used for this study. Three k-type thermocouple sensors were used to monitor the ambient, biogas, and slurry temperatures in real-time. The results showed that the average ambient temperature in the autumn, late autumn, and winter was 29.05, 22.90, and 17.64 °C, respectively. The average slurry temperature in the autumn (30.38 °C) was higher than in the late autumn (29.36 °C) and in the winter (25.76 °C). The highest and lowest slurry temperatures were found to be 31.11 and 24.47 °C, respectively, which indicated that the digester worked within a wide temperature range, establishing both psychrophilic and mesophilic operational conditions. Higher methane concentrations were observed in the autumn than in the late autumn and winter. The CO2 and H2S concentrations were higher in the winter than those of in the autumn and late autumn. The electricity generation in the winter was 47.85% and 45.15% lower than in the autumn and late autumn, respectively.

Denoising MAX6675 reading using Kalman filter and factorial design

This paper aims to tune the Kalman filter (KF) input variables, namely measurement error and process noise, based on two-level factorial design. Kalman filter then was applied in inexpensive temperature-acquisition utilizing MAX6675 and K-type thermocouple with Arduino as its microprocessor. Two levels for each input variable, respectively, 0.1 and 0.9, were selected and applied to four K-type thermocouples mounted on MAX6675. Each sensor with a different combination of input variables was used to measure the temperature of ambient-water, boiling water, and sudden temperature drops in the system. The measurement results which consisted of the original and KF readings were evaluated to determine the optimum combination of input variables. It was found that the optimum combination of input variables was highly dependent on the system's dynamics. For systems with relatively constant dynamics, a large value of measurement error and small value of process noise results in higher precision readings. Nevertheless, for fast dynamic systems, the previous input variables' combination is less optimal because it produced a time-gap, which made the KF reading differ from the original measurement. The selection of the optimum input combination using two-level factorial design eased the KF tuning process, resulting in a more precise yet low-cost sensor.

Effect of Accelerators on the Curing of Unsaturated Polyester Resins: Kinetic Model for Room Temperature Curing

Several iron and vanadium compounds were evaluated as accelerators for curing of unsaturated polyester resins, serving as alternatives to toxic cobalt(II) carboxylates currently in widespread use in the composite industry. The catalytic power of the given metal-based compounds has been verified by gelation time measurements on a multipurpose unsaturated polyester/styrene/methyl ethyl ketone peroxide system. Due to different demands of the application sphere, our detailed investigation of the curing process has covered two extreme situations: the behaviors of the accelerators under adiabatic and isothermal conditions. Exothermic behavior in the thermally isolated system, followed by a K-type thermocouple, enabled recognition of the inhibition of the curing process at high concentration of the accelerator and verification of its thermal stability. At isothermal conditions, a radical copolymerization process has been followed by real-time near-infrared spectroscopy, which enabled the establishment of a kinetic model for precise quantification of the catalytic effect for given accelerators.

Experimental Study of Polyethylene Fusion by Scheffler Solar Concentrator

Aims: The present work is the use of Scheffler technology to melt plastic waste to produce composite materials using an oven type receiver. The composite material in this study contains polyethylene as a matrix and sand as reinforcement.&#x0D; Study Design: The fusion temperature of polyethylene is about 200°C and is obtained by solar concentration. The experimental plastic melting unit in Saaba (latitude 12.38° N; longitude -1.43° E), Burkina Faso, uses two 8 m² Scheffler concentrators sharing a cubic receiver. Three types of mirrors with a reflectivity of at least 90% are used as reflecting facets to equip the Scheffler dishes at the site.&#x0D; Methodology: The thermal behavior of the receiver is analyzed experimentally. Temperatures are measured on the inner and outer walls as well as the internal air temperature with 5 K-type thermocouples. When the fusion temperature is reached on the inside, we introduce the plastic waste which has been previously washed, crushed, dried and weighed.&#x0D; Results: The installed model obtained an average energy of 1.80 kW at the receiver and an average internal temperature of 251.15°C for an average irradiance of 623 W/m² during the no-load test. During the load test, an average energy of 1.34 kW and an internal temperature of 206.4°C were reached for an average irradiance of 473 W/m² and an optical efficiency of 56%. This test led to the production of two pavers of the composite material matrix with 2.2 kg of plastic waste.&#x0D; Conclusion: These results show that the profiles of the primary reflector, tracking system, and tilt axis are accurate and the maximum concentrated solar flux converges on the absorbing surfaces of the receiver. The tempered panes of the absorbing surfaces is more transparent and less emissive. Thus our device contributes to the valorization of plastic waste by using a non-polluting energy source.

Sensitivity-optimized strongly coupled multicore fiber-based thermometer

In this paper, we report on a multicore fiber-based (MCF) temperature sensor that operates in a wide thermal range and that is robustly packaged to withstand harsh environments. To develop the sensor, the fundamentals concerning the effect of temperature on such fibers have been analyzed in detail to predict the most temperature sensitive MCF geometry. Thanks to it, the device, which operates in reflection mode and consists of a short segment of strongly coupled MCF fusion spliced to a standard single mode fiber, shows higher sensitivity than other devices with identical configuration. Regarding its packaging, it consists of an inner ceramic and two outer metallic tubes to provide rigidity and protection against impacts or dirt. The device was calibrated for a thermal range from −25 °C to 900 °C and a K-type thermocouple was used as reference. Our results suggest that the manufactured optical thermometer is as accurate as the electronic one, reaching a sensitivity up to 29.426 pm/°C with the advantage of being passive, compact and easy to fabricate and interrogate. Therefore, we believe this device is appealing for industrial applications that require highly sensitive temperature sensing in very demanding environments, and that the analysis included in this work could be analogously applied to develop sensitivity-optimized devices for other parameters of interest.