Compress heat exchanger design w notes

Heat Exchanger Design
Mechanical Engineering Department
By Sharon Wenger
June 11, 2015
Heat Exchanger Design training

Outline
Introduction
Why we need to use a systematic approach to design heat exchangers
What factors are needed to design a quality heat exchanger
How do we approach that goal
What are a Process engineers responsibilities
What are the Mechanical engineers responsibilities
What tools are available in-house for heat exchanger design
Heat Exchanger design codes
An example of step by step design for a heat exchanger
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INTRODUCTION
The objective of this training is to provide a concise review of the key issues involved in Heat Exchanger
design. At the start of the heat exchanger design, process and mechanical considerations are crucial. It
needs to be clearly understood what we want to achieve. The calculations in the software program
relies on careful considered input. Engineering judgment must be used to evaluate both thermal and
hydraulic the design results.
So what are the key parameters we should consider to produce a quality design?
The Data Sheet is the final product, all the hard work will be inputted here. When complete it is ready
to be issued to vendors, manufactures for quote.
Client often decide which Vendors to select.
Therefore, we want to produce a quality design to demonstrate we know how to design heat
exchangers.
How do we approach this goal?
 Process Considerations
 Mechanical Considerations
 Construction Considerations
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INTRODUCTION
 Process Considerations
− How many heat exchangers are required?
− What duty?
− What type of utility (air, water, steam, hot oil) is required?
 Mechanical Considerations
− What is the Lead Time and Cost?
 Construction Considerations
Not covered here
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Systematic Approach – the following steps are suggested
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Ho do we approach to design a quality heat Exchanger?

Optimization possibilities
Is Optimization possible?
Pinch Technology is one of the optimize heat exchanger design methods. The results of the pinch
technology will targets for:
1. Calculate utility requirements
2. Estimate exchanger requirements
3. Overview of energy flows for entire process
4. Overall view of entire steam/power system
5. Potential energy saving in a process
6. Targets to aim for
• Quantity of exchangers (# shells, total area)
• Utility Capital cost targets
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Process Considerations

Data Extraction
To start the Pinch Analysis, we need
to extract the necessary thermal data
from process simulations as shown in
Figure 1.
Figures (a) & (b) on next page shows
an example represented by the two
process Flow sheets. We now apply
the pinch analysis principles to design
the heat exchanger.
* Pinch Technology (JGCA-1303-0132)
Example: Condenser Design
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Fig. 1
Fig. 1 Work Steps Required*

Example: Condenser Design (Cont.)
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Process Flow Sheet

Optimization possibilities
9
Example: Condenser design (cont.)
Table 1 shows the thermal extraction data for Pinch Analysis. Streams 1 & 2 are hot steams (heat sources).
Streams 3 & 4 are cold streams (heat sinks). Assume a minimum temperature difference of 10o C. The hot utility
is steam at 200o C and the cold utility is cooling water in the range 25 o C to 30 o C. Figures (a) & (b) represent a
graphical construction of the target for minimum energy consumption for the process.
Fig. 2 Construction of Composite CurvesTable 1

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The minimum energy target for the process. The hot and cold composite curves are now overlapped on one another. Fig. (a), separating them by the
minimum temperature difference ∆Tmin = 10 C.
Fig. (b) shows the minimum hot utility (QHmin)
As you can see, using Pinch Analysis we are able to set targets for minimum energy consumption based on heat and material balance information prior
to heat exchanger design. This allows us to quickly identify any energy saving at an early stage.
For more details refer to JGCA-1303-0132 Pinch Technology
DETERMINING THE ENERGY TARGETS

The Pinch Principle
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The point where ∆Tmin is observed is
known as the “Pinch” and recognizing
its implications allow energy targets
to be realized in practice.
One above and one below the pinch,
as shown in Fig. (a). The system
above the pinch requires a heat input,
The system below the pinch rejects
heat, so is a net heat source. To
restore the heat balance, the hot
utility must be increased by the same
amount, that is, α units., therefore the
cold utility requirement also increases
by α units. In conclusion, the
consequence of a cross-pinch heat
transfer (α) is that both the hot and
cold utility will increase by the cross-
pinch duty (α).
DETERMINING THE ENERGY TARGETS

Systematic Approach – the following steps are suggested
There are two disciplines whose goal is to generate the HX datasheet. Process Engineer and Mechanical Engineer.
Process Responsibilities are:
◦ Selection of heat transfer models
◦ Define Fluid Composition for both shell side and tube side
◦ Define Operating Pressure and Temperature
◦ Define shell side and tube side allowable Pressure limits
◦ Define shell side and tube side velocity limits.
◦ Define Gravity or Density
◦ Define Specific Heat
◦ Define Viscosity, cp
◦ Define Fouling Factor for shell side and tube side
◦ Define Thermal Conductivity
◦ Define Latent Heat, (if phase change)
◦ Complete optimum thermal design
◦ Complete internal Process verification and checking and pass the Data Sheet to Mechanical
12
Ho do we approach to design a quality heat Exchanger?

Optimizing Heat Exchanger Process and Cost Effectiveness
Mechanical engineer shall use the Data Sheet from process and import the
data into COMPRESS. Then complete the mechanical design and complete
the mechanical sections of the Data Sheet.
Mechanical engineer responsibilities are:
1. Confirm the type of exchanger configuration.
2. Set upper and lower design limits on shell diameter
3. Set upper and lower design limits on tube length.
4. Specify both shell and tube side layout
5. Specify pitch, material, baffle cut, baffle spacing and clearances.
6. Prepare Material Requisition
7. Complete Technical Bid Evaluation on bids
Items 1 to 5 are covered in the following sections.
13
Mechanical

Tools are available in-house for design the exchangers
There are two software programs in house
1) HTRI,
2) COMPRESS.
HTRI is best used for process thermal design and to produce TEMA
Datasheet.
COMPRESS is used to design the complete exchanger. Tubesheet(s), tubes,
expansion joint, shell, channels, flanges, head closures, nozzles, etc.
COMPRESS will generate shell side & tube side hydrotest conditions based
on the input design conditions.
There are four ways to create a heat exchanger in COMPRESS.
1. Start from “File” and select “New heat exchanger”.
2. Pressing “Ctrl T” on your keyboard
3. Import an HTRI designed file
4. To Start a File click on the heat exchanger icon found on the main menu
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Mechanical Design Software

Two methods are used in COMPRESS design.
a) TEMA
b) UHX methods.
When to use TEMA or UHX methods.
• When rating an existing exchanger built to TEMA.
• When supplying new equipment where TEMA has been specified in addition to UHX.
Regardless which option is selected, for new exchanger design. ASME is mandatory for tubesheet
design
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COMPRESS Heat Exchanger introduction
How does COMPRESS work

 COMPRESS has a built in interface with HTRI.
 COMPRESS can read and write HTRI’S Xist files
 COMPRESS directly importing an existing HTRI file to complete the mechanical design
 COMPRESS / HTRI interface enables shell and tube heat exchanger files design interchangeable
 COMPRESS can analyze all components design conditions simultaneously
 COMPRESS has built-in Design codes to check and evaluate components design conditions
• Such as ASME VIII UHX, TEMA, or both ASME VIII UHX & TEMA and more
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How does COMPRESS work

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The following screenshots are example from COMPRESS
Exchanger design codes

Example by import an HTRI designed file
Before starting COMPRESS to design a heat exchanger, a few things are required. Open COMPRESS, on the lower right
corner, select the Mode, units, Div. and revision to set up the calculation Mode.
https://support.codeware.com/link/portal/9185/9191/Article/352/COMPRESS-Heat-Exchanger-Tutorial
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COMPRESS Heat Exchanger introduction

Step 1: Start the Heat Exchanger Wizard
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This is the HTRI File Import Values. The color code indicate four results

Step 2: Edit an existing Heat Exchanger
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Report summary

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Report summary

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 HTRI Fundamentals of Exchanger Design
 COMPRESS , BUILD 7500
 COMPRESS REPORT RGX6_663-E016, Provided by -
Leonard Stephen Thill, san, Principal Piping – Lead Piping Stress Specialist, Stress &
Static Equipment
References

Compress heat exchanger design w notes

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