CHEN 3320: ChE Thermo
Department of Chem & Bio Engineering
Assignment # 6
Group Assignment
Fall 2022
Due: Friday Sep 23, 2022 by 11:59 pm
This assignment must be completed in teams, and only one set of solutions should be
turned in to Gradescope. Print the names of the team members at the top of the first
page. You must also enter your team members into Gradescope when you submit the
assignment. The same requirements apply to this assignment as previous assignments.
1. In the Persian Gulf, we can produce electricity by using the difference in temperature
between ocean water near the surface (30°C) and ocean water that is 550. m
beneath the surface (4°C). What is the maximum work that can be obtained for each
kilogram of water that is pumped to the surface? That is, what is the work produced
minus the work required to pump water to the surface?
2. The same inventor from Assignment 5 is applying for a patent claiming a heat
engine that takes in 50. kW of energy from a warm reservoir of water at 75°C,
performs 5.5 kW of work, and loses the rest of the heat by transfer to the
atmosphere at 21 °C. Should the patent be granted? Explain.
3. A Rankine cycle is used to produce power using steam as a working fluid. Liquid
water enters the constant-pressure boiler at 135°C and 25 MPa, and exits at 500 ̊C.
The turbine expands the steam to a pressure of 0.30 MPa. The turbine efficiency is
70%. How much heat must be removed per kilogram of process water in the
condenser? The energy requirements of the liquid pump may be considered
negligible.
4. What happens to efficiency for a Rankine cycle as the inlet pressure to the turbine
increases. Explain why. What happens when the outlet pressure from the turbine
decreases. Explain why.
5. This picture shows a DNA molecule on a surface with vertical pillars on half the
surface. As you observe this through a microscope as a function of time, what
happens. Explain why.
6. An ideal gas is heated in the piston-cylinder arrangement below. When the piston
hits the green stops, it cannot move (but heating continues). Show this process on a
temperature-entropy diagram.
7. Two piston-cylinders each contain one mole of an ideal gas. System A expands
isothermally and reversibly from 3 bar and 350 K to 1 bar. System B expands
isothermally from 3 bar and 350 K to 1 bar but the resisting pressure during the
expansion is 1 bar. Which gas has the larger entropy change? Explain.