(1) Saturated steam flowing at 2.5 kg/s and 200 kPa is condensed into saturated
ID: 2261730 • Letter: #
Question
(1) Saturated steam flowing at 2.5 kg/s and 200 kPa is condensed into saturated liquid at the same pressure in a counter-flow exchanger. The coolant is water with an inlet temperature of 17 degrees Celcius and an outlet temperature of 46 degrees Celcius. What is the mass flow rate of the coolant water in kg/s?
(2) Hydrogen is supplied to a medical facility from ten 3.8 ft^3 compressed hydrogen tanks. Initially, these tanks are at 1538 psia and 80 degrees Fairinheit. The hydrogen is removed from these tanks slowly enough that the temperature in the tanks remains at 80 degrees Fairinheit. After two weeks, the pressure in the tanks is 173 psia. Determine the total heat transfer to the tanks in Btu.
Explanation / Answer
1.
mass flow rate of water x cp x (46-17) = 2.5 x change in enthalpy
mass flow rate water = 2.5 x (2725-582) / (4.2 x 29)
= 43.99 kg/s
2.
work done = NRT ln(p1/p2) = 4.813 moles x 8.314 x 353 x ln(8.89)
= 30.86 kJ
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