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Abstract
In both conventional and nuclear power plants, the high thermal load of thick-walled elements occurs during start-up and shutdown. Therefore, thermal stresses should be determined on-line during plant start-up to avoid shortening the lifetime of critical pressure elements. It is necessary to know the fluid temperature and heat transfer coefficient on the internal surface of the elements, which vary over time to determine transient temperature distribution and thermal stresses in boilers critical pressure elements. For this reason, accurate measurement of transient fluid temperature is very significant, and the correct determination of transient thermal stresses depends to a large extent on it. However, thermometers used in power plants are not able to measure the transient fluid temperature with adequate accuracy due to their massive housing and high thermal inertia. The article aims to present a new technique of measuring transient superheated steam temperature and the results of its application on a real object.
Highlights
The unsteady temperature of the fluid is difficult to measure with satisfactory accuracy under industrial conditions
Large dynamic temperature measurement errors are mainly caused by the massive thermometer housing, which has to withstand high pressure and the pressure of the flowing medium
In the works of Jaremkiewicz et al [8,9,10] is a method of determining fluid temperature developed, taking into account the influence of fluid velocity and the heat transfer coefficient on the sheathed thermocouple surface on the thermometer time constant. This method is suitable for low velocity and atmospheric pressure fluid temperature measurements
Summary
The unsteady temperature of the fluid is difficult to measure with satisfactory accuracy under industrial conditions. In the works of Jaremkiewicz et al [8,9,10] is a method of determining fluid temperature developed, taking into account the influence of fluid velocity and the heat transfer coefficient on the sheathed thermocouple surface on the thermometer time constant. This method is suitable for low velocity and atmospheric pressure fluid temperature measurements. To achieve a short reaction time, micro-thermocouples or very thin thermometers are used as temperature sensors These sensors are not suitable for measuring the transient temperature changes of fluids flowing at high velocity under high pressure. View—longitudinal section, (b) dividing the cylindrical element into four control volumes
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