Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Experimental Study and Simulation Model for Determining the Response Time of Thermocouples with Different Insulation Thicknesses
Submission Author:
Katrine Barbosa Oliveira Chaves , MG , Brazil
Co-Authors:
Katrine Barbosa Oliveira Chaves, Fabiano Drumond Chaves, Juan Jose Garcia Pabon, Ricardo Junqueira Silva, Luiz Machado, Willian Moreira Duarte
Presenter: Katrine Barbosa Oliveira Chaves
doi://10.26678/ABCM.COBEM2023.COB2023-1058
Abstract
The aim of this article is to determine the temporal response of thermocouples with coating thicknesses of 1.5 mm and 5.0 mm. Thermocouples are temperature sensors widely used in various industrial and scientific applications. In some applications, such as experiments on the quenching process on steel tubes, the thermocouple may experience thermal fatigue caused by its exposure to elevated temperature levels and severe thermal cycling involving heating and cooling of the sensor. Therefore, repeated expansions and contractions can lead to the appearance of micro cracks in the thermocouple wire, affecting the accuracy of temperature measurements and eventually causing sensor failure. In these circumstances, thermocouples with greater sheath thicknesses are more suitable. However, thicker thermocouples have a high response time, so that, in processes under transient conditions, the delay will generate an error in temperature at each instant of time. The present study focuses on how different sheath thicknesses affect the thermocouple ability to accurately measure temperature changes over time. Experimental tests were carried out with a pair of thermocouples connected in series. In this pair, a calibrated thermocouple with sheath of 0.5 mm was kept during all tests, but the other was replaced by calibrated thermocouples of 1.5 mm and 5.0 mm. Testing began with both thermocouples of the pair at the same standard temperature. Subsequently the tested thermocouple was transferred to another higher temperature environment. Based on the thermocouple connection configuration, it was possible to perform measurements of time versus electrical current and voltage generated by the thermocouples. These were repeatedly tested and the corresponding delays determined according to different sheath diameters. Results indicated that sheath thickness has a significant impact on thermocouple response. It was observed that thermocouples with 1.5 mm and 5.0 mm sheaths had an average response time of 5 s and 10 s, respectively. Furthermore, these response times were determined through mathematical modeling of thermocouples. Simulations carried out with the model revealed good agreement with the experimental results, since the average error of the model was less than 5%. In conclusion, the results of this work can be used to provide useful information to compensate the delay of thermocouples used in specific applications.
Keywords
Termocouple, temporal response, quenching on steel tubes, mathematical modeling of thermocouples
