MECN2024 Engineering Thermodynamics Assignment Brief 2025 | Wits University

MECN2024 Engineering Thermodynamics Assignment

A Rankine cycle is one of the most common methods to generate electricity by utilising water as the working fluid. The two images below illustrate (a) the component-flow diagram that a Rankine cycle consists of and (b) the temperature-entropy (T-s) diagram of a simple ideal Rankine cycle:

By considering the two diagrams above and the points marked 1-6, the Rankine cycle functions as follows: 

1-2: The pump takes suction of saturated liquid water from the condenser outlet and compresses it to the maximum pressure of the cycle, undergoing an isentropic process.

2-3: Heat is transferred from a heat source (usually a boiler) to the liquid water after the pump discharge until the water reaches saturation temperature for that pressure (constant from 2-5).

3-4: More heat is absorbed by the water from the heat source to induce a latent heat phase change(boiling process) until all liquid is turned into saturated steam.

4-5: More heat is added to form superheated steam at the maximum temperature of the cycle.

5-6: The steam now flows through a turbine, where it produces work in an isentropic expansion process and discharges into the two-phase region of the condenser.

6-1: The remaining heat is rejected in the condenser (heat sink), which is also at the same temperature as the environment. The cycle now resumes as before.

The following properties apply to this Rankine cycle:

By neglecting any stray heat transfer, potential and kinetic energy effects, use the information provided and make the appropriate assumptions to calculate the following: 

• The temperature, pressure, specific volume, specific enthalpy and specific entropy for points(1 -6) indicated in the diagrams above in their correct SI units.
• The specific heat input, 𝑞in (kJ/kg), from the heat source.
• The heat rate input, 𝑄󰇗in (MW), from the heat source.
• The specific heat output, 𝑞out (kJ/kg), from the condenser.
• The heat rate output, 𝑄󰇗out (MW), from the condenser.
• The specific work input, win (kJ/kg), of the pump.
• The work rate input, 𝑊󰇗in (kW), of the pump.
• The specific work output, w out (kJ/kg), of the turbine.
• The work rate output, 𝑊󰇗out (MW), of the turbine.
• The net work rate, if 𝑊󰇗net = 𝑊󰇗out – 𝑊󰇗in.
• The thermal efficiency, if ηTH =𝑊󰇗net / 𝑄󰇗in.
•  If the First Law energy balance, 𝐸󰇗 in – 𝐸󰇗 out, equals zero.

Submission date: 

29 April 2025 08h00

The total project mark contributes 15% of the year mark for the course. Failure to meet the specified deadlines will result in an immediate penalty of 25% for any submission within the first 24 hours past the official deadline. Thereafter, a 100% penalty will be applied after the initial 24-hour period. 

Group Selection and Participation: 

You will be divided into groups of two - three students with whom you will work for the duration of the assignment. Group selection can be viewed on Ulwazi, where a leader for each group will be assigned, who will be in charge of making the final submission for the group. Group member selections will not be changed. Email your group members as soon as possible to ensure that they are active on Ulwazi. In the event of a group being reduced to less than three students due to de-registration or other circumstances, and there are no additional students to fill the group, the onus is on the remaining members to complete the project to the same standard as a two-membered group. 

Submission: 

Submit all the answers on a PDF document, properly written out, showing all the steps taken. 

You must first submit the PDF document on the Turnitin submission so that a Turnitin report can be generated. Then submit the Turnitin report on the Final submissions assignment.

Resources: 

Studying the prescribed textbook (Moran & Shapiro, Principles of Engineering Thermodynamics) is an excellent starting point. Students are also encouraged to make use of additional reading material, online videos, podcasts and any other type of resource to inspire their research; however, these sources must be referenced.