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A pipe is used for transporting boiling water in which the inner surface is at 100°C. The pipe is situated in surroundings where the ambient temperature is 10°C and the convection heat transfer coefficient is 70 W/m2 ⋅K. The wall thickness of the pipe is 3 mm, and its inner diameter is 30 mm. The pipe wall has a variable thermal conductivity given as
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- Hot water at an average temperature of 70°C is flowing over a 15-m section of a cast iron pipe (k = 52 W/m·K) whose inner and outer diameters are 4 cm and 4.6 cm, respectively. The inner surface of the pipe exchanges heat by convection and radiation to the cold air at 10°C inside the pipe, with a convective heat transfer coefficient of 15 W/m2·K and heat transfer coefficient for radiation is 6.157 W/m2·K. The heat transfer coefficient at the outer surface of the pipe in the hot water side is 120 W/m2·K, Draw the thermal resistance network and determine the rate of heat loss from the hot water.arrow_forwardA 5 m long section of a steam pipe whose outer diameter is 10 cm passes through an open space at 30°C. The average temperature of the outer surface of the pipe is measured to be 150°C, and the average heat transfer coefficient on that surface is determined to be 180 W/m^2.k. Determine (a) the rate of heat loss through convection from the steam pipe and (b) the annual cost of this energy loss if steam is generated in a natural gas furnace, and the price of natural gas is 0.05 Rs/Kwh, consider a 250 working-day year.arrow_forwardA person puts a few apples into the freezer at -13°C to cool them quickly for guests who are about to arrive. Initially, the apples are at a uniform temperature of 37°C, and the heat transfer coefficient on the surfaces is 6.3 W/m2 · °C. Treating the apples as 8.2-cm-diameter spheres and taking their properties to be ρ= 836 kg/m3, Cp = 4.05 kJ/kg · °C, k= 0.426 W/m · °C, and α= 1.43 ×10-7 m2/s, determine the center and surface temperatures of the apples in 1.9 harrow_forward
- 10 m long pipe is being used to deliver steam through a processing plant. The inner radius of the pipe is r1 = 6 cm and the thickness of the pipe is 2 cm. Thermal conductivity k = 8 W/m⋅K and the average temperature steam flowing through the pipe is 160°C, the average convection heat transfer coefficient on the inner surface is given to be h = 20 W/m2⋅K. If the average temperature on the outer surfaces of the pipe is T2 = 70°C, (a) express the differential equation and the boundary conditions for steady operating conditions, (b) determine a relation for the variation of temperature in the pipe, and (c) evaluate the rate of heat loss (heat of conduction) from the steam through the pipe.arrow_forwardConsider a person standing in a breezy room at 20°C. Determine the total rate of heat transfer from this person if the exposed surface area and the average outer surface temperature of the person are 1.6 m2 and 29°C, respectively, and the convection heat transfer coefficient is 6 W/m2 ·°C (Fig. 2–75).arrow_forwardSteam at 280° C flows in a stainless steel pipe (k = 15 W/m⋅K) whose inner and outer diameters are 5 cm and 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation (k = 0.038 W/m⋅K). Heat is lost to the surroundings at 5° C by natural convection and radiation, with a combined natural convection and radiation heat transfer coefficient of 22 W/ m2⋅K.Taking the heat transfer coefficient inside the pipe to be 80 W/ m2⋅K.Determine the rate of heat loss from the steam per unit length of the pipe and Determine the temperature decrease between the inner pipe surface and the outer insulation surface.arrow_forward
- A refrigerator door of area 0.6 sq.m consists of 25 mm of insulation on top of a thin metal sheet. The film heat transfer coefficients inside and outside the refrigerator are 10.0 and 15.0 W m-2K -1 , respectively, and the thermal conductivity of the insulation is 0.25 W m-1K -1 . If the working temperature of the refrigerator is 0oC and ambient temperature is 20oC, determine the heat flow through the refrigerator door and the temperature of the inside surface of the door.arrow_forwardSteam at 320°C flows in a stainless steel pipe (k = 15 W/m-°C) whose inner and outer diameters are 5 cm and 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation (k = 0.038 W/m-°C). Heat is lost to the surroundings at 5°C by natural convection and radiation, with a combined natural convection and radiation heat transfer coefficient of 15Wm2-°C. Taking the heat transfer coefficient inside the pipe to be 80 W/m2-°C, determine the rate of heat loss from the steam per unit length of the pipe. Also determine the temperature drops across the pipe shell and the insulation.arrow_forwardSteam at To1= 320°C flows through a cast iron pipe (k = 80 W/mK) with inner and outer diameters of D1= 5cm and D2 = 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation with k = 0.05 W/mk(Figure Q2). Heat is lost to the surroundings (To2 = 5°C) by natural convection and radiation, with a combinedheat transfer coefficient of h2 = 18 W/m2.K.(a) Taking the heat transfer coefficient inside the pipe to be h1 = 60 W/m2 K, Calculate the rate of heat lossfrom steam per unit length of pipe.(b) Calculate the temperature differences between the pipe shell and the insulation. Someone comments that a microwave oven can be viewed as a conventional oven with zero convectionresistance at the surface of the food. Is this a correct statement? Discuss the reason.arrow_forward
- Hot water is flowing at an average velocity of1.5 m/s through a cast iron pipe (k = 52 W/m·K) whose innerand outer diameters are 3 cm and 3.5 cm, respectively. Thepipe passes through a 15-m-long section of a basement whosetemperature is 15°C. If the temperature of the water dropsfrom 70°C to 67°C as it passes through the basement and theheat transfer coefficient on the inner surface of the pipe is400 W/m2·K, determine the combined convection and radiationheat transfer coefficient at the outer surface of thepipe.arrow_forwardIn a meat processing plant, 2-cm-thick steaks (k =0.45 W/m·K and a = 0.91 * 1027 m2/s) that are initially at25°C are to be cooled by passing them through a refrigerationroom at 211°C. The heat transfer coefficient on both sides ofthe steaks is 9 W/m2·K. If both surfaces of the steaks are to becooled to 2°C, determine how long the steaks should be keptin the refrigeration room. Solve this problem using analyticalone-term approximation method (not the Heisler charts).arrow_forwardIn a meat processing plant, 4 cm-diameter spherical meat balls (k=0.45 W/m-K and α=0.91×10-7 m²/s) that are initially at 25 °C are to be cooled by passing them through a refrigeration room at -10 °C. The heat transfer coefficient in the cold room is 22.5 W/m²-K. If surface of the meat balls is to be cooled to 3 °C, determine how long the meat balls should be kept in the refrigeration room. What will be the center temperature of the meat balls at the end of the process?arrow_forward
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