Specification
It has been found that to improve product quality, a process stream leaving a storage vessel on a chemical plant now needs to be cooled from a temperature of 100ºC to a temperature of 50ºC before entering the reactor. The ambient air temperature averages 15ºC with a high of 25ºC.
A water supply at 40ºC is available
Derive at least four concept designs to satisfy the given specification. Use short written descriptions and simple sketches to illustrate your ideas. Show evidence of the use of the following techniques:
- brainstorming
- synectics
- morphological chart.
2. Use the weighted objective method to select your best solution from any four of the concept designs.
3. What other information would be required to be able to write a more complete Product Design Specification? (Use an objective tree to clarify and expand upon the vague brief given.)
QUESTION # 02
1. Following on from question # 01, produce a design report for design of the product based on the scenarios covered on the following pages. The report should contain, where appropriate:
- Title page
- Acknowledgements
- Summary
- Contents
- Introduction
- Basic Product Design Specification
- Design Parameters
- Simple Description of chosen Design
- Design Evaluation
- Conclusions
- References
- Appendices.
scenario
Heat exchanger
Based on a full Product Design Specification, the shell and tube heat exchanger to be used will replace part of the pipe connecting the existing reactor feed inlet and the storage tank. This pipe is an 80 mm internal diameter pipe which has a wall thickness of 4 mm. The connections required on the heat exchanger will have the same internal diameter andwall thickness as the pipe and are to be made using flanges which are 150 mm diameter, 15 mm thick and joined to an identical flange on the pipe using 4 M10 nuts and bolts equally spaced with centres 15 mm from the circumference of the flange.
The maximum horizontal space between the storage tank and reactor inlet is 7 m.
The large amount of cooling required means that water (rather than air) will need to be used for the cooling and this is to be supplied via a 42 mm internal diameter pipe, wall thickness 4 mm, fitted with a 100 mm flange, 10 mm thick with 4 holes equally spaced with centres 12 mm from the circumference to allow M8 nuts to be used for the connection to a similar pipe and flange on the water pipe. For higher efficiency, the water will flow in the shell counter current to the process fluid within the tubes.
96 tubes are required of 12 m length to give the required heat exchange surface area and each tube will need to be 20 mm internal diameter (to maintain the required flow velocity of process fluid), of 4 mm wall thickness (for strength) and at centres 50 mm apart. Square pitch is to be used to enable easier cleaning. The tube headers are semi-spherical of diameter D (the diameter of the shell) and 10 mm wall thickness. The tube plates are 6 mm thick.
The total shell area per tube pass is to be 0.2618 m2. Four shell side baffles are required to maintain the required water flow velocity and level of turbulence. The baffles will be equally spaced and will be of height 0.7D (D = diameter of shell).
The baffles and any pass partition plates used will be 5 mm thick to give them the required strength.
For safety reasons, the shell will be covered by 100 mm of lagging. You will be required to draw a central cross-section of the heat exchanger and a view of the tube plate at either end of the exchanger.