Question 21, Morning Session, 2013 Professional Case Studies
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The outer wall of the steel pipe with a diameter of φ108x4 mm is wrapped successively with insulation materials 50 mm and 60 mm thick. The temperature of the outer wall of the pipe is t1=110°C, while the surface temperature of the outermost layer of insulation material is t2=32°C. The insulation layers are in good contact with each other; the thermal conductivity values of the inner and outer insulation layers are 0.043 W/(m·°C) and 0.07 W/(m·°C), respectively. What is the heat loss per meter of pipe length (in W)? (A) 33.56 (B) 36.38 (C) 21.45 (D) 43.23 Finally, I’ve found the original question; I’m sharing it here and seeking an answer.
Similar examples can be found in this book on chemical engineering principles, or in the Tianjin University review books