Chapter 2, Problem 2.59P

A 50-cm-diameter pipeline in the Arctic carries hot oil at 30◦C and is exposed to a surrounding temperature of −20◦C. A special powder insulation 5 cm thick surrounds the pipe and has a thermal conductivity of 7 mW/m · ◦C. The convection heat-transfer coefficient on the outside of the pipe is 9 W/m2 · ◦C. Estimate the energy loss from the pipe per meter of length.   (Please give step-by-step solution)

In a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 1.7 cm enters into the boiler that has the thermal conductivity as 0.3 W/mK. The boiler is maintained at 107degreeC and temperature of the water that flows inside the pipe is at 31degreeC. If the energy transfer (Q) is 124925 kJ in 7 hours. Determine the Heat transfer rate, Surface area of the pipe and Diameter & Length of the pipe, if D = 0.012 L.Change in Temperature (in K) Heat Transfer Rate (in W) Surface Area of the Pipe (m2) Pipe Length (in m) Pipe Diameter (in mm)

Consider a 2-m-wide 1.5-m-high wood-framed window with 3-mm-thick single-panel glass covering 85 percent of the area (k = 0.7 W/m °C). Pine wood (k = 0.12 W/m °C) is used for the frame, which is 5 cm thick. Inside, the heat transfer coefficient is 7 W/m2 °C, while outside, it is 13 W/m2 °C. The temperature in the room is kept at 24°C, while the outside temperature is 40°C. Considering and stating the necessary assumptions.   calculate the percent inaccuracy in heat transfer when the window is supposed to be made entirely of glass. (b) Consider the continuous heat flow through a room's wall in the winter. As a result of the winds, the convection heat transfer coefficient at the outer surface of the wall is three times that of the inner surface. Which side of the wall do you believe the temperature will be closest to the temperature of the surrounding air? Explain.

Consider a steam pipe of length L = 26 m, inner radius ? = 5 cm, outer radius ? = 7 cm, and thermal conductivity k = 25 W/m·K, as shown in Fig. The inner and outer surfaces of the pipearemaintainedataveragetemperaturesof? =120°Cand? =50°C,respectively.Obtain a general relation for the temperature distribution inside the pipe under steady conditions and determine the rate of heat loss from the steam through the pipe.

Steam 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.

Convective heat transfer coefficient is 15 W/(m*K), surface area of the fin is 2 m^2, the temperature at the base is 70 C and the ambient temperature is 20 C. Determine the fin efficiency if the actual heat transfer rate from the fin is 500 W?

In a thermal power plant, a horizontal copper pipe of "D" diameter, "L" length and thickness 0.6 cm enters into the boiler that has the thermal conductivity as 0.33 W/mK. The boiler is maintained at 105C and temperature of the water that flows inside the pipe is at 28C. If the energy transfer (Q) is 118922 kJ in 6 hours.  Determine the Heat transfer rate, Surface area of the pipe and Diameter & Length of the pipe, if D = 0.016 L.  Change in Temperature (in K) = Heat Transfer Rate (in W) = Surface Area of the Pipe (m2) =

The blades of a wind turbine turn a large shaft at a relatively slow speed. The rotational speed is increased by a gearbox that has an efficiency of 0.93. In turn, the gearbox output shaft drives an electric generator with an efficiency of 0.95. The cylindrical nacelle, which houses the gearbox, generator, and associated equipment, is of length L = 6 m and diameter D = 3 m. If the turbine produces P = 2.5 MW of electrical power, and the air and surroundings temperatures are T = 25 oC and Tsur = 20 oC, respectively, determine the minimum possible operating temperature inside the nacelle. The emissivity of the nacelle is 0.83, and the convective heat transfer coefficient is h = 35 W/m2 .K. The surface of the nacelle that is adjacent to the blade hub can be considered to be adiabatic, and solar irradiation may be neglected.           Use Fin or N number of fins to reduce the Ts of the nacelle less than 143 oC

Pulverized coal particles are used in oxy-fuel combustion power plants for electricity generation. Consider a situation where coal particles are suspended in hot air flowing through a heated tube, where the convection heat transfer coefficient is 100 W/m2·K. If the average surface area and volume of the coal particles are 3.1 mm2 and 0.5 mm3, respectively, determine how much time it would take to heat the coal particles to two-thirds of the initial temperature difference.