Assignment 2:
(Design Problem 2 – Heat Exchanger Project Spreadsheet)
Due Date: Thursday 5th May 2023, 5:00 pm Please submit electronically as an excel spreadsheet file through a submission point in the assessments folder on Learning @ Griffith
Weighting: 25% of the total marks for this course.
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The report should be in the form of a Microsoft Excel spreadsheet. Each question should be on a separate page (sheet) in the excel workbook (with tabs labelled Question 1, Question 2, etc.). Input parameters should be clearly identified with units specified. Likewise, output parameters should also be highlighted. The spreadsheet should be ‘user friendly’ so that someone else could easily use the spreadsheet to solve the same problems but with different input parameters.
While the lab work is done in groups. Every student should submit their own spreadsheet.
Design Brief
Your task is to design, build and test a prototype double-pipe (i.e. concentric tube) heat exchanger. The objective of the heat exchanger is to cool water which is initially at a temperature of 60 C and flowing at a rate of 0.8 L/min to below 50 C. You have access to a water supply at room temperature (approximately 20 C) and in the interests of conserving water, the flow rate of cold water should be limited to 3.6 L/min (0.06 kg/s). (If it is possible, the flow rate of cold water should be less than this). You have access to a heat exchanger testing module (produced by TecQuipment) during the laboratory classes. You will be given a selection of pipes (with various diameters, lengths, etc.) to build your heat exchanger. Before starting construction, you should make predictions of your prototype’s performance in order to choose the most appropriate pipe diameters and lengths.
One of the technical officers from your company also found a few commercial heat exchangers of different types in the back shed. Your boss requested that (in addition to building your prototype heat exchanger) you should also test these to see if any of them can meet the design requirement. Your report should contain graphs showing the performance of each heat exchanger for different flow rates of cold fluid up to the maximum allowed (i.e. 3.6 L/min).
Question 1: Raw HX Data Collected in the Lab
On the first Tab of the spreadsheet, you should include the raw data that you collected in the Lab. This should include data from the commercial heat exchanger and raw data from the double pipe heat exchanger that you built. Please insert photographs of the heat exchangers tested on this Tab also. Data should be easy to understand and labeled with units.
Please also include a graph on this Tab. The graph should show clearly the measured performance of the commercial heat exchanger and the prototype heat exchanger that you built. Please include an indication on the graph as to whether the heat exchangers could satisfy the design specifications.
Question 2: Theoretical Calculations of Double Pipe Heat Exchanger Performance
On the second Tab of the spreadsheet you should make a spreadsheet calculator that can predict the performance of the double pipe heat exchanger as a function of the following inputs:
• Flow rate of hot water
• Inlet temperature of hot water
• Flow rate of cold water
• Inlet temperature of cold water
• Inside diameter of the inner tube
• Outside diameter of the inner tube
• Inside diameter of the outer tube
• Length of the heat exchanger
• Density of the hot water
• Density of the cold water
• Viscosity of the hot water
• Viscosity of the cold water
• Thermal conductivity of the hot water
• Thermal conductivity of the cold water
The outputs should be:
• Outlet temperature of the hot water
• Outlet temperature of the cold water
• Difference in temperature between inlet and outlet of the hot water
• Heat transfer rate from hot to cold water
A brief explanation of the theory/equations used should be included on this Tab also. When you submit your spreadsheet, the values of the pipe diameters and length entered should be the ones for the best performance.
Question 3: Comparison between Theory and Experiment
On the third tab of the spreadsheet, you should have a graph that shows how well your measurements for your prototype heat exchanger compare with the theory predictions. A figure (drawing or photograph with annotations) showing the key dimensions of your constructed heat exchanger.
Question 4: Radiation Calculator
On the fourth tab you should include a calculator to estimate the radiation heat exchange between a long cylinder at the temperature of the outside surface of your prototype HX (measured in the lab) and the surrounding room temperature (measured in the lab).
The inputs to the calculator should be:
• The diameter of the cylinder
• The length of the cylinder
• The surface temperature of the cylinder
• The temperature of the walls of the surrounding room
• The emissivity of the surface of the cylinder
The output:
The net radiation heat transfer from the surface of the cylinder to the walls of the room.
You should add a comment as to why radiation heat exchange can be neglected based on your calculation result.