Heat and Mass Transfer: Fundamentals and Applications 5th. Edition by Yunus A. Çengel, Afshin J. Ghajar | 9780073398181 | 0073398187 | Holooly

Heat and Mass Transfer: Fundamentals and Applications [EXP-6580]

211 SOLVED PROBLEMS

A 0.2 m × 0.2 m vertical plate has a surface temperature that is maintained at 40°C. Air at 20°C is flowing in parallel over the plate with a velocity of 0.4 m / s. Determine the Nusselt number for both assisting flow and opposing flow (Fig. 9-38).

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SOLUTION Air is flowing over a vertical plate. Nus...

A 0.2-W small cylindrical resistor mounted on a PCB is 1 cm long and has a diameter of 0.3 cm, as shown in Fig. 15-41. The view of the resistor is largely blocked by the PCB facing it, and the heat transfer from the connecting wires is negligible. The air is free to flow through the parallel flow

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SOLUTION A small cylindrical resistor mounted on a...

A 10 -m-long metal pipe kpipe =15 W / m.K has an inner diameter of5 cm an outer diameter of 6 cm is used for transporting hot saturated water vapor at a flow rate of 0.05 kg / s (Fig.8-33).The water vapor enters and exits the pipe at 350°C and 290°Crespectively. In order to prevent thermal burn on

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SOLUTION In this example, the concepts of PtD are ...

A 10- cm × 12- cm circuit board dissipating 24 W of heat is to be conductioncooled by a 1.2-mm-thick copper heat frame (k=386 W / m. °C ) 10 cm ×14 cm in size. The epoxy laminate (k=0.26 W / m.°C ) has a thickness of 0.8 mm and is attached to the heat frame with conductive epoxy adhesive

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SOLUTION A circuit board with uniform heat generat...

A 10-cm-diameter copper ball is to be heated from 100°C to an average temperature of 150°C in 30 minutes (Fig. 1–14). Taking the average density and specific heat of copper in this temperature range to be ρ=8950 kg/m^3 and cp = 0.395 kJ/kg·°C, respectively, determine (a) the total amount of heat

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The copper ball is to be heated from

100^{\...

A 12-cm-wide and 18 -cm-high vertical hot surface in 30°C air is to be cooled by a heat sink with equally spaced fins of rectangular profile Fig. (9-23) . The fins are 0.1 cm thick and 18 cm long in the vertical direction and have a height of 2.4 cm from the base. Determine the optimum fin spacing

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SOLUTION A heat sink with equally spaced rectangul...

A 15- cm × 20- cm PCB has electronic components on one side, dissipating a total of 7 W, as shown in Fig. (15-42). The PCB is mounted in a rack vertically together with other PCBs. If the surface temperature of the components is notto exceed 100°C, determine the maximum temperature of the

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SOLUTION The surface temperature of a PCB is not t...

A 15-cm × 20-cm integrated circuit board is to be cooled by attaching 4-cm long aluminum (k = 237 W/m∙K) fins on one side of it (Fig. 3–50). Each fin has a 2-mm × 2-mm square cross section. The surrounding ambient temperatureis 25°C and the convection heat transfer coefficient on each fin surface

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SOLUTION In this example, the concepts of Preventi...

A 2-kW resistance heater wire whose thermal conductivity is k = 15 W/m·K has a diameter of D = 4 mm and a length of L = 0.5 m, and is used to boil water (Fig. 2–58). If the outer surface temperature of the resistance wire is Ts = 105°C, determine the temperature at the center of the wire.

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SOLUTION The center temperature of a resistance he...

A 2-kW resistance heater wire with thermal conductivity k = 15 W/m·K, diameter D = 0.4 cm, and length L = 50 cm is used to boil water by immersing it in water (Fig. 2–18). Assuming the variation of the thermal conductivity of the wire with temperature to be negligible, obtain the differential

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SOLUTION The resistance wire of a water heater is ...

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