3 Introduction Heat Exchanger Design
This chapter will introduce you into the heat exchanger design module. First open a job and create a new heat exchanger as described in chapter 2. In below figure the open job number is V-1234-99 and the selected item is heat exchanger number E-1003 of TEMA type AEM.
The next paragraphs will tell you how to start entering the data for the heat exchanger design. It will start by editing the Nozzle list document. Then opening the document called Mechanical vessel design. In this document you can enter the mechanical design data and the materials for the heat exchanger. The mechanical design document contains a custom made material list especially designed for heat exchangers.
3.1 Edit the nozzle list
Select and open the nozzle list document from figure 3-1. The default number of nozzles for a heat exchanger is 4. For each nozzle you must enter the following data:
- Nozzle mark
- Service description
- Flange rating " Flange type
- Flange facing type
- Nominal nozzle neck outside diameter
- Nozzle neck wall thickness
- Nozzle neck wall tolerance
Don't enter the reinforcement pad dimensions and the standout. The heat exchanger design module will calculate these values for you. You can use the option menus to select pipe schedules, rating and flange types.
3.2 Edit the mechanical datasheet
Select and open the document called Mechanical vessel design (figure 3-1). This will open the mechanical datasheet (figure 3-4). The MDS is divided into four section:
- Design data: pressures, temperatures, join efficiency, number of passes etc.
- Design data cylinders : diameters, optional thickness and optional reinforcement pad dimensions.
- Design data girth flanges: type of flange and gasket properties.
- Design data tube sheet and bundle: tube properties, tube pitch layout, baffle cuts and spacing, optional tube sheet thickness.
Fill in the mechanical datasheet completely and use the File menu entry Save to secure the data. It is good practice to save the mechanical datasheet every time you made some important changes to the data.
3.2.1 Optional data entries
Some of the data entries are marked as optional (figure 3-4). A value of zero indicates the design module must calculate an optimised value for this entry. You can force the heat exchanger design to use a specific user defined value by entering a none zero value for the optional data entry. Example: you want use a 13 mm thick plate for the channel. In the section called Design data cylinders enter the value 13 in the entry called Wall thickness (this entry is marked as optional). The design module will design the channels using a 13 mm wall thickness. If the 13 mm plate is not enough for the design pressure you will get a warning indicating there is not enough wall thickness to satisfy the pressure code regulations. There are optional data entries for the cylinder wall thickness, reinforcement pads, tube sheet thickness and flat cover thickness (if applicable).
3.2.2 Reinforcement pads
You can force the design module to design the heat exchanger with integral nozzle reinforcement. If you fill the data entry called Allow reinforcement pads with No the design module will calculate the cylinder wall thickness to be sufficient for internal pressure and nozzle reinforcement. There will be no reinforcement pads required because of the oversized wall thickness of the cylinders. In case of large reinforcement pads you could try this option to reduce the length of the channels.
3.2.3 Gasket parameters
Use the Edit menu entry called Gasket to select one of the standard ASME gaskets. VES has added some new gaskets to the end of the list (Camprofiles). If you want to use none standard gaskets you must enter the gasket parameters like the compression factor and the seating pressure yourself. You can get these parameters from your gasket supplier.
3.3 Edit the material list
Use the Edit menu entry Material list to open the material list (figure 3-4). This is a custom made material list especially for the heat exchanger design module. In this list you can find the allowable stress values and the specific gravity for each material.
You can select materials from the material database supplied by VES. Or you can enter materials not available in the material database.
To enter a material from the material database:
- Move the cursor onto the cell of the material you want to edit.
- Use the Material button to open a selection window containing the database materials.
- Select on of the materials and click the Ok button.
- The material and allowable stress values will appear in selected cell of the material list.
To enter a custom material not available from the material database:
- Move the cursor onto the cell of the material you want to edit.
- Enter the custom material description.
- Enter the allowable stress values and the specific gravity (Kg per cubic decimeter).
For each design cycle the design module will check if the design temperature has changed. For the materials selected from the VES material database it will adjust the allowable stress values for the new design temperature.
If you have entered materials not available from the VES material database you have to check the allowable stress values for these materials yourself. If you are ready entering materials click the Close button and use the Save menu to secure the data changes.
3.4 Starting a heat exchanger design cycle
Design & View
If you have filled the nozzle list, mechanical data sheet and the material list you are ready to start a design cycle. To start a design cycle use the View menu entry Design & View… from the mechanical data sheet. To design the heat exchanger you have two options:
- Design & View the heat exchanger dimensions. This option will design the heat exchanger and show you a workbook filled with the mechanical datasheet, all pressure part dimensions, nozzle list and the material list. You can use the Export to Excel button to create a MS Excel work of this output. This is useful if you want to E-mail the heat exchanger design over the Internet.
- Design & View the ASME calculations. This option will design the heat exchanger and show you a workbook filled with all applicable ASME calculations. This workbook can also be exported to a MS Excel formatted file.
Each time you run a design cycle all dimensions will recalculated. You have to run at least one design cycle to get a complete heat exchanger design. After running a design cycle you can use the View menu to get a weight table or to view the setting plan drawings.
Check & View (customised heat exchangers)
After running at least one design cycle you can use the Stoomwezen, ASME or AD Merblätter modules to customise one of the pressure parts. Now you can only use one of the Check & View … menu entries. Using one of these entries will not change the heat exchanger design and only report if there are inconsistencies in the heat exchanger design. If you want to discard the customised pressure parts you can rerun a Design & View … cycle. This will restore the default pressure part dimensions. After a Design & View .. cycle all customised data will be lost (you could use the Item menu entry Copy to secure your customised heat exchanger design).
3.5 Design options
The Edit menu entry Options will open the option window. This window is filled with design parameters you can use the control the heat exchanger design. There are options for:
- Flange design
- Minimum bolt sizes
- Tube sheet design
- Nozzle position and orientations
- Saddle positions
- Dished covers design
- Flat cover design
- Floating tube sheet design
You can get technical help for all options by clicking the Help button at the bottom of the options window. In the help file you will find picture and text explaining the use of all options. Some options will change the heat exchanger design details. Therefore it is useful to print the option worksheet if you have finalised your heat exchanger design. Use the print button to get a printable design parameter worksheet.
End of quick reference.
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