how to model fluid-solid (heated-platen heat exchanger) heat transfer in Simscape

Hello

I want to model fluid-to-solid heat transfer in Simscape. For fluid-to-fluid heat exchange, we have blocks for heat exchangers, but I haven't come across one for fluid-to-solid heat exchange (please correct me if I'm mistaken).

In my current model, process fluid is being heated by thermal oil. The thermal oil circuit acts as the main loop, where the oil circulates, transfers heat to the user (another fluid), and returns to the main circuit. The secondary loop is an open process loop, where fluid from a reservoir enters at a fixed temperature, gets heated by the thermal oil, and then flows back to the reservoir. The outlet temperature of the process fluid controls the opening/closing of a 3-way valve (attached diagram).

Now, I want to achieve something similar but with a heated platen. In this case, instead of process fluid, we have a solid plate being heated by the thermal oil. The temperature of the plate will control the opening or closing of the 3-way control valve.

Could you guide me on how to approach this setup in Simscape?

Answer 1

[akshatsood]

Hi @Muhammad Ali,

I understand that you are looking to model a fluid-to-solid heat transfer system in Simscape, where a solid plate is heated by a circulating thermal oil. The temperature of the solid plate will control a 3-way valve, similar to how a fluid-to-fluid heat exchanger operates.

Approach to Modeling in Simscape

Understand the Components:

• Thermal Oil Circuit: This is your primary loop where the thermal oil circulates and transfers heat.
• Solid Plate: This is your secondary component, which receives heat from the thermal oil.
• 3-Way Valve: This valve will be controlled based on the temperature of the solid plate.

Modeling Steps

• Create the Thermal Oil Circuit.
• Use the "Thermal Liquid" blocks in Simscape to model the thermal oil loop.
• Include pumps, pipes, and heat transfer elements to simulate the flow and heat exchange.

Model the Solid Plate:

• Use the "Thermal Mass" block to represent the solid plate.
• This block allows you to simulate the heat capacity and temperature of the solid plate.

Heat Transfer Between Fluid and Solid

• Use "Convective Heat Transfer" block to simulate the heat transfer between the thermal oil and solid plate.
• Set the parameters such as heat transfer coefficient and surface area based on your system specifications.

Control System for the 3-Way Valve

• Use a "Temperature Sensor" block to measure the temperature of the solid plate.
• Implement a control strategy using "Simulink blocks" or a "PID Controller" to control the 3-way valve based on the temperature reading.

Simulation and Validation

• Simulate the model to ensure the solid plate reaches the desired temperature.
• Adjust parameters such as flow rates, heat transfer coefficients, and control settings to match real-world data.

Please refer to the following documentation for better understanding

https://www.mathworks.com/help/releases/R2023a/hydro/thermal-liquid-modeling.html

By following these steps, you should be able to create a functional model of a fluid-to-solid heat transfer system in Simscape, where the temperature of a solid plate controls a 3-way valve. Adjust and validate your model.

I hope this helps.

[Muhammad Ali]

Thanks @akshatsood

I’ve followed your advice and created the model (see attached image). However, I am facing a minor issue: after the plate absorbs heat from the thermal oil, it transfers that heat to the wooden panels involved in the process. I want to account for this heat transfer (loss) by incorporating the energy loss from the plate, which reduces its temperature. Specifically, I need to introduce an external temperature source (in blue) that reflects the plate's temperature after it has lost heat to the wooden panels.

I hope my question is clear, and I would appreciate your guidance on how to integrate this temperature source block into the model.

Thanks!

[akshatsood]

Hi @Muhammad Ali,

It sounds like you are making great progress with your Simscape model. To account for the heat transfer from the solid plate to the wooden panels, you can follow these steps to incorporate the energy loss..

Modeling the Wooden Panels

• Use a "Thermal Mass" block to represent the wooden panels. This block will simulate the heat capacity and temperature change of the panels as they absorb heat from the solid plate.

Heat Transfer Between Plate and Wooden Panels

• Add a "Convective Heat Transfer" block or a "Conductive Heat Transfer" block to model the heat transfer between the solid plate and the wooden panels.
• Set parameters such as heat transfer coefficient and contact surface area according to your needs.

Incorporating External Temperature Source

• To reflect the temperature of the plate after losing heat, you can use a "Temperature Source" block.
• Connect this block to the solid plate to simulate the effect of external conditions or heat loss.

By integrating these components, you should be able to simulate the heat loss from the solid plate to wooden panels.

I hope this helps.

[Muhammad Ali]

Hello @akshatsood

good progress indeed, thanks to your advice!

I just want to be more clear about placement of connection of "temperature source". If you see in the attached image, I have placed the connection before and after the Thermal Mass (in blue).

I am not sure about what would it mean placing before or after the Thermal Mass component and how would it affect the physics.

Thanks

[akshatsood]

Hi @Muhammad Ali,

As per my understanding, the placement of the "Temperature Source" block in relation to the "Thermal Mass" can influence how the simulation interprets the heat flow and temperature distribution.

Temperature Source Before Thermal Mass:

• Interpretation: This setup suggests that the external temperature source directly influences the solid plate before considering the heat capacity of the wooden panels.
• Effect: The temperature source will affect the temperature of the solid plate first, and then the heat will be transferred to the thermal mass of the wooden panels. This might be suitable if you want to simulate a scenario where the solid plate is directly exposed to an external temperature change before interacting with the wooden panels.

Temperature Source After Thermal Mass:

• Interpretation: In this configuration, the thermal mass (wooden panels) is influenced by the temperature source after the heat has been transferred from the solid plate.
• Effect: The temperature change due to the external source will be applied to the thermal mass after accounting for the heat transfer from the solid plate. This might be appropriate if you want to simulate the effect of external conditions on the wooden panels directly, independent of the initial state of the solid plate.

Choosing the Right Configuration:

• Before Thermal Mass: Use this if the external temperature primarily affects the solid plate first.
• After Thermal Mass: Use this if the external temperature primarily affects the wooden panels or if you want to simulate the response of the wooden panels to changing external conditions.

I hope this helps.