Design a radiation shield for the thermocouple described in Design Problem 1.2. Determine the accuracy of the thermocouple measurement with the shield as a function of air temperature and velocity. Suggest modifications to the shield that could be used to further improve the accuracy, e.g., painting or electroplating one or both surfaces. Are there any other modifications to the geometry of the thermocouple and shield that could provide further improvement?

Data from in Design Problem 1.2

Design a thermocouple installation to measure the temperature of air flowing at a velocity of 15 m/s in a 1-m-diameter duct. The air is at approximately 1000°C and the duct walls are at 200°C. Select a type of thermocouple to use, and then determine how accurately the thermocouple measures the air temperature. Prepare a plot of the measurement error vs. air temperature and discuss the result. Use Table 1.4 to estimate the convection heat transfer coefficients. This is a multistep problem; after one has studied convection and radiation, improve this design to reduce the measurement error by orienting the thermocouple and its leads differently and using a radiation shield.

Transcribed Image Text:

Air flow Duct Leads Shield Thermocouple