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Tham khảo tài liệu 'a heat transfer textbook - third edition episode 3 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Problems 589 radiation but that it offers very little resistance to conduction. Thus the window temperature is almost uniform. 10.28 A very effective low-temperature insulation is made by evacuating the space between parallel metal sheets. Convection is eliminated conduction occurs only at spacers and radiation is responsible for what little heat transfer occurs. Calculate q between 150 K and 100 K for three cases a two sheets of highly polished aluminum b three sheets of highly polished aluminum and c three sheets of rolled sheet steel. 10.29 Three parallel black walls 1 m wide form an equilateral triangle. One wall is held at 400 K one is at 300 K and the third is insulated. Find Q W m and the temperature of the third wall. 10.30 Two 1 cm diameter rods run parallel with centers 4 cm apart. One is at 1500 K and black. The other is unheated and 8 0.66. They are both encircled by a cylindrical black radiation shield at 400 K. Evaluate Q W m and the temperature of the unheated rod. 10.31 A small-diameter heater is centered in a large cylindrical radiation shield. Discuss the relative importance of the emittance of the shield during specular and diffuse radiation. 10.32 Two 1 m wide commercial aluminum sheets are joined at a 120 angle along one edge. The back or 240 angle side is insulated. The plates are both held at 120 C. The 20 C surroundings are distant. What is the net radiant heat transfer from the left-hand plate to the right-hand side and to the surroundings 10.33 Two parallel discs of 0.5 m diameter are separated by an infinite parallel plate midway between them with a 0.2 m diameter hole in it. The discs are centered on the hole. What is the view factor between the two discs if they are 0.6 m apart 10.34 An evacuated spherical cavity 0.3 m in diameter in a zerogravity environment is kept at 300 C. Saturated steam at 1 atm is then placed in the cavity. a What is the initial flux of radiant heat transfer to the steam b Determine how long it will take for .
