Heat Transfer and Temperature
Question 1:
A 50 mm diameter, thin wall metal pipe covered by 25 mm thick layer of insulation (ki = 0.085 W/m.K) and carrying a superheated steam at atmospheric pressure is suspended from the ceiling of a large room. The steam temperature entering the pipe is 120 oC, and the air temperature is 20 oC. The overall heat transfer coefficient on the outer surface of the covered pipe is 10 W/m2.K. if the velocity of the steam is 10 m/s, at what point along the pipe will the steam begin condensing and what distance will be required for the steam to reach a mean temperature of 100 oC?
Question 2:
Consider a horizontal, thin walled circular tube of diameter D = 0.025 m submerge in a container of n-octadecane (paraffin), which is used to store thermal energy. As hot water flows through the tube, heat is transferred to the paraffin, converting it from the solid to liquid state at the phase change temperature of T∞ = 27.4 oC. The latent heat of fusion and density of paraffin are hsf = 244 kJ/kg and ρ = 770 kg/m3, respectively and thermophysical properties of the water may be taken as cp = 4.185 kJ/kg.K, k = 0.635 W/m.K, and μ = 467 x 10-6 kg/s.m. Assuming the tube surface to have a uniform temperature corresponding to that of the phase change, determine the water outlet temperature and total heat transfer rate for a water flow-rate of 0.1 kg/s and inlet temperature of 60 oC. If the height, width and length of the container are 0.25 m, 0.25 m and 3 m, respectively, how long would it take to completely liquefy the paraffin, from an initial state for which all of the paraffin is solid and at 27.4 oC?
Question 3:
Consider the process by which ice is formed for an indoor rink. A parallel array of cooling tube is submerge in a shallow layer of water, and a refrigerant (Freon-12) is passed through the tubes. The layer height is H = 60 mm and the tube pitch, diameter and length are S = 50 mm, D = 12 mm, and L = 5 m, respectively. The temperature and flow rate of
A 50 mm diameter, thin wall metal pipe covered by 25 mm thick layer of insulation (ki = 0.085 W/m.K) and carrying a superheated steam at atmospheric pressure is suspended from the ceiling of a large room. The steam temperature entering the pipe is 120 oC, and the air temperature is 20 oC. The overall heat transfer coefficient on the outer surface of the covered pipe is 10 W/m2.K. if the velocity of the steam is 10 m/s, at what point along the pipe will the steam begin condensing and what distance will be required for the steam to reach a mean temperature of 100 oC?
Question 2:
Consider a horizontal, thin walled circular tube of diameter D = 0.025 m submerge in a container of n-octadecane (paraffin), which is used to store thermal energy. As hot water flows through the tube, heat is transferred to the paraffin, converting it from the solid to liquid state at the phase change temperature of T∞ = 27.4 oC. The latent heat of fusion and density of paraffin are hsf = 244 kJ/kg and ρ = 770 kg/m3, respectively and thermophysical properties of the water may be taken as cp = 4.185 kJ/kg.K, k = 0.635 W/m.K, and μ = 467 x 10-6 kg/s.m. Assuming the tube surface to have a uniform temperature corresponding to that of the phase change, determine the water outlet temperature and total heat transfer rate for a water flow-rate of 0.1 kg/s and inlet temperature of 60 oC. If the height, width and length of the container are 0.25 m, 0.25 m and 3 m, respectively, how long would it take to completely liquefy the paraffin, from an initial state for which all of the paraffin is solid and at 27.4 oC?
Question 3:
Consider the process by which ice is formed for an indoor rink. A parallel array of cooling tube is submerge in a shallow layer of water, and a refrigerant (Freon-12) is passed through the tubes. The layer height is H = 60 mm and the tube pitch, diameter and length are S = 50 mm, D = 12 mm, and L = 5 m, respectively. The temperature and flow rate of