Learning Forum

[Abubakar]

Hi Sir,

I was doing an Intro heat transfer course, I found some issues with an example which I am expanding below,

In video number 01 of the Intro heat transfer course the instructor explaining the conduction with the below example,

[Karthik Remella]

Hello You are right about natural convection if the density of the gas is a function of temperature and if the gravitational vector is in the favorable direction (downward-pointing). We don't mention any of these details here and are simply assuming that there is no gravity and the density of the gas is constant. Under these conditions, conduction is the primary mode of heat transfer. I hope this helps.
Karthik

[Abubakar]

Hi Sir Just one follow-up question "As we have a temperature gradient the density can't be constant, right?"

[Karthik Remella]

Not necessarily. Density is a property of the material. Whether it is a strong or weak function of temperature depends on the fluid or solid material. Again, this is just to simplify and help understand the concept. But, I can see your point if the material were air and we had a favorable gravity vector for causing natural convection.
Karthik

[Abubakar]

Understood sir. Thanks for helping me.