# Thermal Design of Shell and Tube Heat Exchanger and Mean Metal Temperatures Calculation

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. Aspen Exchanger Design and Rating

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.

### Problem Definition

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 Figure 1 – Double Pipe Exchanger Schematic

### 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: Figure 2 – ASPEN EDR Run Modes

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. Figure 3 – Geometry of The Exchanger Figure 4 – Process

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. Figure 5 – Water Properties Table per Temperature Figure 6 – Hot side Liquid Density vs Temperature Figure 7 – Hot side Liquid Thermal Conductivity vs Temperature

Below is the list of all the plots that can be generated by ASPEN for the hot and cold streams. Figure 8 – Available Plots

We can also specify the full exchanger geometry and materials, if required. Below are few screenshots of the possible inputs. Figure 9 – Exchanger Shell and Heads Figure 10 – Exchanger Covers Figure 11 – Exchanger Tubesheets Figure 12 – Exchanger Flanges Figure 13 – Exchanger Tube Layout Parameters

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. Figure 14 – TEMA Sheet

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. Figure 15 – Tube-side and Shell-side Temperatures Figure 16 – Tube-Side Bulk, Fouling Surface, and Metal Temperatures Figure 17 – Shell-side Bulk, and Fouling Surface Temperatures

Here is the list of all the plots that can be generated by ASPEN EDR. Figure 18 – Available Output Plots

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. Figure 19 – Exchanger 3D model

The dimensions are shown below. Figure 20 – 3D model Dimensions

The shell-side and tube-side input and output boundary conditions are shown below: Figure 21 – Tube Inlet Mass Flow and Temperature Figure 22 – Tube Outlet (Ambient Pressure and Temperature) Figure 23 – Shell Inlet Mass Flow and Temperature Figure 24 – Shell Outlet (Ambient Pressure and Temperature)

Running the simulation produces the results found below: Figure 25 – Shell-side Fluid Temperature Figure 26 – Tube-side Fluid Temperature Figure 27 – Fluid Temp. through Tube Length Figure 28 – Tube Metal Temperature Figure 29 – Shell Metal Temp. Figure 30 – Shell Inlet Temp. (Through Shell Inlet Nozzle Diameter) Figure 31 – Shell Outlet Temp. (Through Shell Outlet Nozzle Diameter)

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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