3. (30 pts) You are a safety engineer for a curling iron manufacturer. Your company is coming out with a new model which

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3 30 Pts You Are A Safety Engineer For A Curling Iron Manufacturer Your Company Is Coming Out With A New Model Which 1 (95.98 KiB) Viewed 45 times

3. (30 pts) You are a safety engineer for a curling iron manufacturer. Your company is coming out with a new model which sports a 3 cm diameter barrel 20 cm long. Under normal operation, a thermostatic controller in the unit turns the 200 W heater inside the curling iron barrel on and off as needed to maintain a surface temperature of 200°C. As a safety engineer you have been asked to do a heat transfer analysis to estimate the steady state surface temperature of the curling iron barrel in the event that the controller failed and the 200 W heater remained on constantly. Assume the iron has achieved steady state heat transfer and that the air temperature and wall and ceiling temperatures of the bathroom are all 20°C. The convective heat transfer coefficient between the iron and the air is 35 W/m²K. The emissivity of the barrel is 0.3 and you decide to ignore the heat transfer from the tip of the barrel. (a) Determine the surface temperature of the barrel of the curling iron assuming it is uniform over the whole surface. (A guess and check solution may be required.) Knowing that the flame temperature of paper is 233°C and is 250°C for cotton, do you think there is a safety concern with this new model? (b) What is the radiation heat transfer rate from the curling iron at steady state? (c) What is the convection heat transfer rate? (d) Do you think it would be worth an extra $5 per curling iron to add a coating on the barrel that increased the emissivity to a value of 0.9? Explain/justify your response.