ASPEN Exchanger Design & Rating software can be used for thermal analysis of various types of exchangers including shell and tube, air cooled, fired heater, plate, plate-fin, and coil wound. It covers single phase liquid, single phase gas as well as the two-phase fluids.
This software can be used for:
- Calculating the size of an exchanger based on the specified process requirements (such as inlet and outlet temperatures, flow rates, and other factors).
- Calculating the outlet conditions given the exchanger geometry.
- Running vibration analysis on a shell and tube heat exchanger.
- Calculating pressure drop.
In this article, we are going to use ASPEN Exchanger Design and Rating software to simulate a double pipe heat exchanger. We have used a simple double pipe counter-flow heat exchanger to be able to compare and verify the results obtained from ASPEN EDR with the CFD results obtained from SolidWorks Flow Simulation.
The double-pipe heat exchanger we are going to simulate throughout this article has the following dimensions and process characteristics:
|Shell ID: 30 mm||Tube mass flow rate: 0.2 kg/s|
|Shell OD: 36 mm||Tube inlet Temp.: 343 K|
|Tube OD: 19 mm||Shell mass flow rate: 0.4 kg/s|
|Tube thk.: 2 mm||Shell inlet Temp.: 283 K|
|Tube Length: 1000 mm||Shell and tube side fluids: Water|
|Tube material: SS|
Simulating in ASPEN Exchanger Design and Rating
We are going to use ASPEN EDR to get the shell-side and tube-side outlet temperatures based on the exchanger geometry and the fluid information provided above.
ASPEN EDR has four run modes as shown below:
Design (Sizing): For finding the size of exchanger for specified process requirements.
Rating/Checking: Evaluates how over or under surface (required heat transfer area for the required heat load) the defined exchanger geometry is for a process requirement.
Simulation: Evaluates the outlet conditions achievable for a defined exchanger geometry.
Find Fouling: Evaluates the fouling resistance consistent with defined process conditions.
For our sample problem, the exchanger geometry is known, and we are looking to calculate the outlet temperatures for both the tube-side as well as the shell-side. The Simulation mode will be used.
Below are the screenshots showing the values used for defining the geometry and the process of the exchanger.
In the next step, the thermodynamic properties for the hot and cold streams will be defined. ASPEN has a database covering various materials and chemical compositions used in the industry. In this example we are going to use Water as the fluid for both the hot and cold streams. ASPEN will calculate the physical and thermodynamic properties of both streams using the thermodynamic equation of states (tables) for the full range of temperatures and pressures applicable to our current exchanger design. Below are screenshots showing the resultant property table and plots generated by ASPEN for hot and cold streams (water). We can export all the plots and tables into excel or modify their values, if required.
Below is the list of all the plots that can be generated by ASPEN for the hot and cold streams.
We can also specify the full exchanger geometry and materials, if required. Below are few screenshots of the possible inputs.
Running the simulation, ASPEN will generate outputs and calculation results. The most useful output may be the TEMA Sheet. Below is the TEMA Sheet for our sample exchanger. The outlet temperatures for both the shell-side and tube-side have been highlighted in green.
ASPEN also generates several plots showing the distribution of the temperatures, heat loads and pressures through the exchanger. Below are some sample plots generated by ASPEN for our exchanger.
Here is the list of all the plots that can be generated by ASPEN EDR.
Other useful calculations performed by ASPEN are the vibration analysis and the pressure drop calculations. We are going to explain them in more detail during future posts.
In the next section of this article, we are going to use CFD using SolidWorks Flow Simulation and compare the results to the outlet temperatures calculated by ASPEN.
SolidWorks Flow Simulation
We have created the 3d model in SolidWorks per the problem definition in part 1 of this article. We are going to use this 3D model to run CFD and compare the outlet temperatures with the ones calculated by ASPEN.
Below is the screenshot of the exchanger 3D model in SolidWorks.
The dimensions are shown below.
The shell-side and tube-side input and output boundary conditions are shown below:
Running the simulation produces the results found below:
As we can see in the above plots (Figure 27 and Figure 31), the tube-side and shell-side outlet temperatures almost perfectly match the ASPEN results (Figure 14).
Tube metal temperature calculated by ASPEN (Figure 16) shows a temperature range from 43.3° C (316.45 K) at the tube inlet to 38.7° C (311.85 K) at the tube outlet. Tube metal temperature obtained from CFD results (Figure 28) shows an almost perfect match.
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