Question

# 8. Large spherical tanks are often used to store low temperature gases at chemical plants. An AISI 304 stainless steel tank with an inner diameter of 40 meters is completely

filled with liquid nitrogen at -196 °C with a convective heat transfer coefficient hn2, of 167 W/m^2-K. The wall thickness of the tank is 12 cm, and the outside of the sphere is exposed to air at 25 °C, with a convective heat transfer coefficient, hair, of 67 W/m?-K. To find properties of the steel, use 200 K. A. What are the values of the thermal resistance terms going between bulk air and bulk liquid nitrogen(in K/W)? B. What is the total heat transfer rate, q, from the air to the liquid nitrogen? C. A thin layer of insulation is added to the outside of the spherical tank. The insulation has k = 0.08 W/m-K and is 1.5 cm thick. What is the thermal resistance term for the insulation? Does the thermal resistance term for any of the other layers change because of the addition of the insulation? If so, calculate. D. Calculate the new heat transfer rate with insulation to determine if the insulation helped reduce heat transfer. What is the % of heat transfer with insulation (D) compared to without (B)?Comment on your answer.

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