[Thermal Liquid library Simscape] Help for an Engine cooling model

Hey guys !

I am part of a formula student team, and decided to create a simulation and modelling department for the team, which aims to model our car in Simulink. I am pretty new to simulink/simscape, and as a first task, I wanted to model the car cooling system. The aim is to determine a required flow rates in the radiators to help the aero team to design side pods.

The cooling system follows the path : Left radiator (ambient cooled) -> right radiator (ambient air and a fan operating) -> pump -> engine -> reserve tank -> left radiator ect...

My model can be found through the drive : <link removed>

For now, it has been assumed that the engine temperature is constant at 383.15K. I have neglected the effects of the fan, as they operate only when the car is at low speed. The heat exchanger now receives moist air as coolant (so ambient air), and through a pressure source (which I guess is the pressure agains the radiator as the car is driving). The cooling curve looks better, however, as I vary the pressure source value, the coolant temperature doesn't vary (or I can't notice on the graph any change in temperature. (it always look like that)

Could anyone help me on that ? Not only the model displays wrong values (from testing, the coolant temperature should sit at 80°C ), but i am also looking for a way to chnaghe the pressure block source, to a volume flow rate in the radiators.

Here is a picture of my updated simplified model. To model the radiators, I have used the tutorial: from mathwork https://uk.mathworks.com/help/hydro/ug/modeling-heat-exchangers.htm

[Yifeng Tang]

I changed pressure_sidepods from 500 to 2000 and did observe change in the coolant temperature. The trend looks reasonable, so I am thinking this mismatch between simulation result and test (coolant at 80degC) is most likely (1) parametrization and (2) the way some components are represented.

I observe in Simscape Result Explorer that each heat exchanger is rejecting >10kW of heat, these are reasonable numbers. Of course, it also depends on how big your car is. Do you know how much heat they should reject? In the test data, you should be able to find out from inlet & outlet temperature, flow rate and specific heat.

Another thing to think about: the engine thermal load is now modeled as a temperature boundary at the pipe wall at 383.15K. As the coolant temperature drops at the heat exchangers, the temperature difference in the engine "pipe" increases and more heat will enter the coolant stream, hence more heat needs to be rejected. Is this the most reasonable way to represent the engine? Will a heat flow source be more appropriate? I'm not sure. Just wondering.

One more comment: I saw you are using an offset to convert K to degC. You can use the affine conversion in the PS-Simulink converter to do the same thing, without extra blocks. Details here: https://www.mathworks.com/help/simscape/ug/how-to-apply-affine-conversion.html

Answer 1

[Yifeng Tang]

Copied from the comment section:

I changed pressure_sidepods from 500 to 2000 and did observe change in the coolant temperature. The trend looks reasonable, so I am thinking this mismatch between simulation result and test (coolant at 80degC) is most likely (1) parametrization and (2) the way some components are represented.

I observe in Simscape Result Explorer that each heat exchanger is rejecting >10kW of heat, these are reasonable numbers. Of course, it also depends on how big your car is. Do you know how much heat they should reject? In the test data, you should be able to find out from inlet & outlet temperature, flow rate and specific heat.

Another thing to think about: the engine thermal load is now modeled as a temperature boundary at the pipe wall at 383.15K. As the coolant temperature drops at the heat exchangers, the temperature difference in the engine "pipe" increases and more heat will enter the coolant stream, hence more heat needs to be rejected. Is this the most reasonable way to represent the engine? Will a heat flow source be more appropriate? I'm not sure. Just wondering.

One more comment: I saw you are using an offset to convert K to degC. You can use the affine conversion in the PS-Simulink converter to do the same thing, without extra blocks. Details here: https://www.mathworks.com/help/simscape/ug/how-to-apply-affine-conversion.html