Thermocouple, model

The parameters r and depend on the constructional and material characteristics of the temperature-sensing device (i.e., thermocouple, casing, materials of construction). It is clear that the response of a thermocouple modeled by eq. (13.11) is slower than that of a thermocouple modeled by eq. (13.10) (see Figure 13.8). 

An Omega model HH22 type J-K digital thermometer, connected to a type K thermocouple probe inserted directly into the flask, was used to measure the temperature. 

Thermocouples were placed in the curing part so that the model could be compared to the actual process. The model accurately predicted the cure time and temperature curing profiles for several parts with different geometries and curing conditions. 

Perhaps a more severe comparison of model response is the time history of the centerline temperature. These values reflect the interaction of several phenomena the reaction itself, the heat liberated by the reaction, the heat storage capacity of the material, and the rate at which heat can be carried away from the centerline region by conduction. Figure 8 shows the temperatures predicted by the Chiao and finite element models, as well as the imposed autoclave temperature history. It also includes five thermocouple readings which were reported in Chiao s manuscript (8). 

Gulton-Rustrak Quartel Data Logger - Model 58-100 with - Type K thermocouple pod-58-124... 

Figure 135 shows a temperature history in a cooling experiment. In Figure 136 the time when the temperature at the different thermocouples in the experiment dropped below the phase change temperature is compared with predictions from different models. 

Several features of the early model (Fig. 6) have been modified in the present-day, high-temperature version of this calorimeter (Fig. 7) (37). Depending upon the temperature range envisaged, the block is made of refractory steel, alumina, or beryllium oxide and is machined to house the calorimeter itself. The thermoelectric pile (about 50 platinum to platinum-rhodium thermocouples) is affixed in the grooves of an alumina plate (A), which is permanently cemented to two cylindrical tubes of alumina (B). Cylindrical containers of platinum (C) ensure the uniformity of the temperature distribution within the calorimeter cells. 

Saito with a fine wire thermocouple embedded at the surface [3]. The scatter in the results are most likely due to the decomposition variables and the accuracy of this difficult measurement. (Note that the surface temperature here is being measured with a thermocouple bead of finite size and having properties dissimilar to wood.) Likewise the properties k. p and c cannot be expected to be equal to values found in the literature for generic common materials since temperature variations in the least will make them change. We expect k and c to increase with temperature, and c to effectively increase due to decomposition, phase change and the evaporation of absorbed water. While we are not modeling all of these effects, we can still use the effective properties of Tig, k, p and c to explain the ignition behavior. For example,... 

A comparison has been made between small scale test results and a field trial at a 17-ton scale for a solid compound [217]. The test results from a very sensitive calorimeter (Thermal Activity Monitor from ThermoMetric, Sweden) were substituted in a model, and the self-heating situation in bulk containers was predicted. The large-scale trial was carried out in a steel rectangular container lined with polyethylene. A control device was used to keep the container at a temperature of 40 to 45°C. Several thermocouples enabled monitoring of the temperature as a function of time in different places in the large container. 

The raw data of the thermocouples consist of the temperature as a function of time (Fig. 8.9, left). In the raw data, the passing of the conversion front can be observed by a rapid increase in temperature. Because the distance between the thermocouples is known, the velocity of the conversion front can be determined. The front velocity can be used to transform the time domain in Fig. 8.9 (left) to the spatial domain. The resulting spatial flame profiles can be compared with the spatial profiles resulting from the model. The solid mass flux can also be plotted as a function of gas mass flow rate. The trend of this curve is similar to the model results (Fig. 8.9, right). 

A Teflon-coated thermocouple of the J-type attached to an Omega model 650 digital thermometer can be substituted for the immersion thermometer. 

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

It is important to note that Vie and Kjelstrup [250] designed a method of measuring fhe fhermal conductivities of different components of a fuel cell while fhe cell was rurming (i.e., in situ tests). They added four thermocouples inside an MEA (i.e., an invasive method) one on each side of the membrane and one on each diffusion layer (on the surface facing the FF channels). The temperature values from the thermocouples near the membrane and in the DL were used to calculate the average thermal conductivity of the DL and CL using Fourier s law. Unfortunately, the thermal conductivity values presented in their work were given for both the DL and CL combined. Therefore, these values are useful for mathematical models but not to determine the exact thermal characteristics of different DLs. 

Commercially available heat flux sensors with thermopiles sandwiched at the interface were used to measure the local temperatures and heat fluxes that is. Omega Corporation, Model HFS-4 devices. The total thickness of the sensors was nominally less then 0.18 mm, and a schematic of the device is shown in Fig. 5.10. By measuring the temperature difference across the center film (AT) and assuming one-dimentional heat transfer, then the heat flux can be measured using the temperature difference and the thermal conductivity of the film. The local temperature is recorded using the thermocouple nearest the barrel. The senors were calibrated at ambient condition with zero heat flux. 

Mench et al. developed a technique to embed microthermocouples in a multilayered membrane of an operating PEM fuel cell so that the membrane temperature can be measured in situ. These microthermocouples can be embedded inside two thin layers of the membrane without causing delamination or leakage. An array of up to 10 thermocouples can be instrumented into a single membrane for temperature distribution measurements. Figure 32 shows the deviation of the membrane temperature in an operating fuel cell from its open-circuit state as a function of the current density. This new data in conjunction with a parallel modeling effort of Ju et al. helped to probe the thermal environment of PEM fuel cells. 

The physical and mathematical model of the determination of ignition rate are not explicitly formulated. However, it is understood from the displayed graphs that the ten thermocouples inserted in the fuel bed are used to detect the speed of the ignition front. The thermocouples are placed with a known distance between them. Furthermore, Rogers states The ignition rates were computed as the product of the rate of travel of the ignition front and the initial bed density . No verification method was used. 

Inside the column oven, the solvent flows through 0.75 m of 0.009 in. I.D. conditioning coil, through a low dead-volume tee containing a thermocouple to monitor solvent temperature, and then to the column. The column oven, with a 425 0 maximum temperature, is heated by two 2-kilowatt wire wound heaters which are controlled with a Gulton Model 2GB Controller which provides either Isothermal or programmed temperature control. 

Exhaust gas temperature measurements are made with a fine-wire R-type thermocouple connected to an Omega model 660 digital readout. Gas samples are extracted using a 6.4-millimeter (0.25-inch) O.D. water-cooled stainless-steel suction probe and then filtered, dried, and analyzed for CO, CO2, O2, UHC, and NOj . Instrumentation includes a Beckman model 864 NDIR CO2 analyzer, Beckman model 867 NDIR CO analyzer, Siemens OXYMAT 5E paramagnetic O2 analyzer, Siemens FIDAMAT 5E-E FID total hydrocarbon analyzer, and a Beckman model 955 Chemiluminescent NO/NOj, analyzer. Certified span gases are used for instrument calibration. PC-based data acquisition is available during experimentation. All of the emissions data reported here were obtained approximately 24 pipe diameters downstream of the fuel injector and represent average exhaust concentrations. 

Tool-mounted optrode (TMO). The cure-monitoring experiments described here were conducted with a "tool-mounted" optrode (TMO) arrangement (5,6) (Figure 2) which is Ideally suited for the manufacturing environment where minimum interference with the laminate layup work is desirable. The use of a tool-mounted optrode is as simple as the use of tool-mounted thermocouples currently in wide use. Indeed, the TMO provides viscosity/degree-of-cure information on the cure state of the surface layer only. However, knowledge of the cure state of the surface layer permits determination of the cure states in the bulk based on the available models (1,2). 

Heat transfer models of the autoclave process are the most accurate and well understood of all the process models. Much of this understanding is because the models are so easily verified through thermocouple measurements. Thermocouples are the most common part-sensing technique used in production. The challenging aspects are the incorporation of the affects of resin flow, resin kinetics, and autoclave position on heat transfer properties. The importance of incorporating resin kinetic models is to properly predict conditions that may lead to exotherms, especially for thick laminates [17]. 

Heat transfer models are a powerful tool for developing autoclave process cycles. They are especially useful in aiding tool designers in choosing tooling materials, thicknesses, and thermocouple locations. Models can also be used to determine if a tooling concept would be detrimental in a specific position in the autoclave and the types of tools that should be processed together to optimize the cure cycle. 

Changes in convective heat transfer coefficients due to autoclave position and loading scheme are difficult to model. These coefficients are more easily correlated from experimental data. This correlation can be determined from monitoring thermocouples attached to tools or by correlating air flow based on autoclave position. These coefficients are crucial for determining the rate of heat transfer from the autoclave environment into the part. Heat transfer coefficients are also a function of autoclave pressure however, the adjustment for... 

Most supervisory controllers contain some minimal capability to vary from the process plan, such as the ability to detect faulty thermocouples and react appropriately. Knowledge-based, real-time controllers take this adaptability one step further by using combinations of sensors and/or models to determine the state of the process and predict trends. The controllers then compare the measured state with the desired state, and change the process plan when necessary to adapt to those trends, forcing the outcome toward a desired state. Knowledge-based systems must include some means of converting the sensor data into information and a set of rules to act on that information. Knowledge-based control systems are not always... 

Biological castles are employed during heat penetration situations in order to demonstrate the degree of process lethality provided by the sterilization cycle. Calibrated biological indicators utilized for this purpose function as bioburden models providing data that can be utilized to calculate Fq or substantiate and supplement physical temperature measurements obtained from thermocouples. 

Finally, predicted and simulated catalyst temperatures are compared in Fig. 23. These temperatures were measured by a thermocouple inserted into the catalyst 25 mm from the front face, as measured in the axial direction. The agreement between measurement and prediction is good, indicating that the thermal properties used in the model for the catalyst/substrate are reasonable. 

Pressures within the optical cells are adjusted using a microprocessor-controlled supercritical fluid syringe pump (Isco model SFC-500). The temperature of the cylinder head is regulated using a VWR 1140 temperature bath. The output from the pump is directed through a 2 /xm fritted filter and a series of valves into the optical high pressure cell which is temperature controlled ( 0.1 °C) by a Lauda RLS-6 temperature bath. The local temperature of the optical cell is determined using a thermocouple (Cole Palmer) placed directly into the cell body. 

The entire valve, located outside the oven is independently heated and insulated from the column oven via 1/2" Cole Palmer flexible heating cord (Cole Palmer Instrument Co., Chicago, IL). Heating is controlled via a thermocouple and an Electronic Control Systems (Model No. 800-262) temperature controller coupled to a Glas-Col variable AC voltage source (Glas-Col Apparatus Co., Terre Haute,... 

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