Modelling and testing of industrial thermometers

Thermocouples and Resistance Temperature Detectors are widely used in nuclear power plants and other industrial processes for temperature measurements. Such measurement is necessary for control and safety purposes. Thus temperature sensors and the various factors that may affect their speed of response are of great importance to manufacturers and users of temperature sensors.

This work is concerned with the numerical simulation of temperature sensors along with the experimental verification of theoretically developed correlations to characterize and better understand sensor behavior under laboratory and practical conditions.

A general purpose computer program for two-dimensional simulation of industrial temperature sensors has been developed. The program permits dynamic simulation of industrial sensors. Effects of porosity of the insulator, surface heat transfer coefficient, and physical pro perties of the sensor were examined to demonstrate the utility of the approach.

In addition, an extensive set of experiments was carried out to verify a theoretically developed correlation. This correlation indicates that the time constant varies inversely as the heat transfer coef ficient. Experimentation involved different liquids, different velocities, different sensors, and different experimental facilities. The results have shown satisfactory validation of the theoretical rela tion.

As a continuation of the experimental program, an apparatus for testing temperature sensors in dry and wet air has been constructed. Tests were carried out on four thermocouples. The results show that the response times increase dramatically in comparison with the response times in liquids.