1. Thermodynamic Systems and Ideal Gas Law:
(1) (a) You are part of a team that is to design a low-pressure steam boiler for your manufacturing plant. The plant needs 1.0 kg/s of steam
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with a pressure of 100 kPa and temperature of 120 C (u=2,537.3 kJ/kg, v = 1,792.9 cm /g). Liquid water is available at 100 kPa, saturated,
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(u=417.36 kJ/kg, v=1.0432 cm /g). Your team decides to first consider designs using an electric heating coil as heat source. Calculate the
power requirement in kW needed by the heating coil. One member suggests the following simple design.
(b) When design A is presented to your team, one of the team claims that he can reduce the power requirement by using the product
steam to preheat the liquid feed. This would be done by passing the feed water through a heat exchanger before it enters the boiler. The
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heat exchanger would be insulated, and it would use steam from the boiler to heat the feed from 28 C to 100 C. Analyze the design and
discuss whether the power requirement of the heating coils is in fact smaller than in design A.
(2) A stone of 25 kg mass and a tank containing 300 kg of water comprise a system. The stone is 20 m above the water level initially. If the
stone falls into water, then determine the available energy, in Joules when:
a. The stone is about to enter the water
b. The stone has come to rest in the tank
c. The heat is transferred to the surroundings in such an amount that the stone and water come to their initial temperature.
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(3) Carbon Dioxide has a pressure of 350 kN/m when its volume is 0.03 m and its temperature is 35 C. Determine the mass of the gas. If the
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gas pressure is increased to 1.05 MN/m while the volume remains constant, determine the new temperature of the gas?
