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Unformatted text preview: QL, irrev Low-temperature reservoir at TL FIGURE P7–154
7–155 The inner and outer surfaces of a 2-m 2-m window
glass in winter are 10°C and 3°C, respectively. If the rate of
heat loss through the window is 3.2 kJ/s, determine the amount
of heat loss, in kilojoules, through the glass over a period of
5 h. Also, determine the rate of entropy generation during this
process within the glass.
7–156 Two rigid tanks are connected by a valve. Tank A is insulated and contains 0.2 m3 of steam at 400 kPa and 80 percent
quality. Tank B is uninsulated and contains 3 kg of steam at
200 kPa and 250°C. The valve is now opened, and steam flows
from tank A to tank B until the pressure in tank A drops to
300 kPa. During this process 600 kJ of heat is transferred from
tank B to the surroundings at 0°C. Assuming the steam remaining inside tank A to have undergone a reversible adiabatic 7–158 An 800-W electric resistance heating element whose
diameter is 0.5 cm is immersed in 40 kg of water initially at
20°C. Assuming the water container is well-insulated, determine how long it will take for this heater to raise the water temperature to 80°C. Also, determin...
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- Spring '09