[Ezail]

Hello everyone, first of all, English is not my native language. I apologize for that.
I am a mechanical engineering student, and I have a project that I am working on. This project is related to natural convection heat transfer. Let me explain the project that I am working on.
As you know, airplanes ascend to high altitudes, where the air temperature can reach as low as -50 to -60 degrees. It is precisely at these temperatures that icing begins to occur on the aircraft's propellers and other components, posing a significant risk and inefficiency for the aircraft. My project involves heating the propellers of an aircraft flying at these temperatures using heating pads and analyzing this process in the Fluent program. According to the project, it will be assumed that there will be no icing when the surface average temperature reaches 0 degrees. Additionally, this project will be executed not by creating a flow volume, but by calculating the average heat transfer coefficient (h) from appropriate Nusselt correlations and reporting it in Fluent. These are the general constraints of the project, dear users.

I have provided a general overview of the project. Now, let's address the problem that I have spent approximately 95 hours on and still haven't solved: Firstly, for flight conditions, we will take the air temperature as -60 degrees and the airspeed as 139 m/s. In order to determine whether the flow is turbulent or laminar and to calculate the heat transfer coefficient (h) using the appropriate Nusselt correlation, the Reynolds number (Re) is calculated, resulting in Re: 836953, indicating turbulent flow. If we calculate the Nusselt number (Nu) from the Nu correlation I shared below, we get a value of 1038.33. When we calculate the heat transfer coefficient from the formula Nu = h.l/k, we find that h is 535.45.
I have shared the appropriate Nusselt number for the project. This Nusselt correlation is formulated for turbulent flow over a flat plate, even though the geometry of the propeller is not that of a flat plate. Nevertheless, we will proceed with the assumption that the geometry can be treated as a flat plate for the purpose of solving this project.
If we revisit the issue, the calculated value for h was 535.45, which is a considerably high value. When I input this value into the Convection section of Fluent and set the Free Stream Temperature to -60 degrees, it becomes impossible to heat the propeller with the defined heating pad in Fluent. I have shared the geometry of the propeller and an image of this analysis below. I enter the power value of the heating pad attached to the propeller surface as 15 kW/m^2 for the purpose of heating the propeller. However, I am faced with such a result. Heating the propeller seems impossible with these h values. Dear users, where am I making a mistake? This project has become a nightmare for me... Please do not withhold your valuable opinions. Regards
(I may have forgotten to provide some information. If I have omitted any crucial details, please do not hesitate to ask and request the missing information from me.)

[MKuhn]

Dear Ezail, regarding the high air speed a heat transfer coefficient of 535 seams reasonable for me, this leads also to the enormous required heating power. Sorry, sometimes physics is hard and the desired practicable solution is not feasible. This seems to be the case here.


--
Moritz

[Ezail]

Originally Posted by MKuhn

Dear Ezail, regarding the high air speed a heat transfer coefficient of 535 seams reasonable for me, this leads also to the enormous required heating power. Sorry, sometimes physics is hard and the desired practicable solution is not feasible. This seems to be the case here.


--
Moritz

Thank you dear MKHun. I think ı am going to add some thermal pads in my design. If you have any suggestion about this topic, please send your suggestions.
Regards