Heat Transfer Simulation

Objective: The convection heat transfer has applications in a wide variety of engineering and technologies applications. To mention some of them, the cooling system should be mentioned which is the main concern of the factories and industries such as microelectronics.  Thus, using some cooling systems with strong and improved cooling methods is something necessary.

Approach: In this study, a hot obstacle which is located in the middle of a rectangular enclosure is cooled, and the flow is considered two dimensional, steady, laminar, and incompressible. This enclosure has an inlet and outlet, and the fluid is entered from one side and gone out from the other side (forced convection heat transfer). All the walls are insulated and the obstacle is hot. The effects of different parameters such as volume fraction of nanoparticles, Reynolds number, Hartmann number, and the outlet place on the heat transfer rate has been investigated.

Results: The results show that the average Nusselt number and heat transfer rate increases as the outlet place goes down. Besides, by increasing the Reynolds number, the isothermal lines are compressed and the dimension of the cold spots near the entrance augments. This phenomenon causes the isotherms to come near the hot obstacle and the heat transfer increases. Moreover, by changing the volume fraction of nanoparticles, no changes are observed in the vertical velocities and the general pattern of the flow as far as the nanoparticles have little effects on the viscosity of nanofluid. Finally, by increasing the Reynolds number and volume fraction of nanoparticles, the average Nusselt number and heat transfer augment.

Objective: This task involves preparing a fully meshed model of a car to run a simulation to check for thermal hot spots in the engine bay and the exhaust components based on the boundary conditions given to us by the testing team. This is a generic simulation that is run by the team in Bangalore, India for various car lines under development at Daimler.

Approach: The methodology involved is to run a fluid simulation to check for convective heat transfer and the flow pattern. This simulation is mainly used to check for any hot spots and the flow parameters through the different heat exchangers ( mass flow, inlet, and outlet temperatures etc). Based on the results, we generally propose ways to increase the mass flow through the heat exchangers or reduce the exit temperature of the Radiator, for example. One such case that I worked on was to alter the porous media coefficients of a radiator such that there is more air flowing through it and to check if the exit temperature falls.

The selection of the porous media co-efficient cannot be random. It has to be selected from a pool of different radiators, condensers used by Daimler. It was seen that the air temperatures from the radiator outlet had come down.

Since all these changes are done at a very early stage of the design process of a car line, simulations such as these are used to improve the design for the next quality gates or design reviews.

Results: The geometry maturity improves at every subsequent design review gates and the validation process and design improvements go as loops. The maturity level of our simulations has reached a level where the reliance on hardware testing has come down. The direct result of such robust simulation methods has been saving costs on hardware testing.

The simulations do not stop at just the fluid flow simulations. The solids are also modeled and simulated to account for conductive and radiation heat transfers. For which the fluid flow simulation is used as an initial condition. And then the fluid and solid simulations are run in loops as co-simulation until both the solid and fluid simulation results converge.