A thermometer well 2 cm in diameter 1 mm thick is made of steel (k = 30 W/mK and it is used to measure the temperature of air flowing through a pipe. Calculate the minimum length of pocket so that the...

A thermometer well 2 cm in diameter 1 mm thick is made of steel (k = 30 W/mK and it is used to measure the temperature of air flowing through a pipe. Calculate the minimum length of pocket so that the error is less than 1% of applied temperature difference. Air temperature is 300°C and h = 100 W/m2K.