Module 6
Assignment 6:
Utilizing your understanding of the First Law of Thermodynamics, consider two turbines: one open flow and one closed flow. Superheated water (a pure substance) is demonstrated throughout each individual turbine.
- The initial pressure is 0.40MPa and the initial temperature is 700ᴼC in both systems.
- The heat loss from the closed system is half that of the open system.
- The temperature for the open system is reduced by 100ᴼC and pressure is reduced by 25% at the second point value.
- The pressure increases to 0.60MPa at the second point value for the closed system. This increase in pressure compensates for the heat loss allowing the temperature to remain constant throughout the closed system.
Questions
- Using the Superheated Water Tables, consider that the superheated water used in both systems is an ideal gas, what is the specific volume of the two system at the second point value for each system.
- Which of the systems is isothermal? Calculate the coefficient of pressure for the adiabatic system.
- If the open turbine system were to be considered a Carnot engine, given your understanding of the 2nd Law of Thermodynamics, what would its the efficiency be?
- Would its COP be higher if it operated as a heat pump or if it operated as a refrigerator?
Discussion 6:
Read and analyze the problem below:
A gas in a piston- cylinder assembly undergoes an expansion process for which the relationship between pressure and volume is given by: pVn
- The initial pressure is 7 bar, the initial volume is 0.1m3 and the final volume is 0.3m3.
- Determine the final pressure of the process, if (a) n = 1.5, (b) n = 1.0 and (c) n = 0.
- Explain how knowing the assumptions assist you in solving the problem.
- How does knowing the pressure of the system add to your understanding of the system?
Assumptions:
- The gas is a closed system
- The expansion is a polytropic process
Post your solution to the problem in this discussion area.