hello, i am using fluent for analysing natural convection rectangular plate heat sink.How to decide about extended boundries? b.r. sunil

hi you have to take the very large enclosure ....so that boundaries should not affect the flow near the heat sink.....also you should use pressure inlet BC at the outer domain boundaries...

Tanveer

thnaks tanveer.In operating Conditions panel which operating temperature & specified operating density values should i give?b.r.sunil

hi sunil,

In natural convection flow will occure because of the temp difference...so you can not treat density as a constant....either you can use boussinsq approximation in materaila panel for density......this option is available in material panel......For operating temp you just use ambient temp and operating density will be same as air density..

note: you have to give some value in density panel after turning on boussinsq approximation and it would be actual density of the air....also you have to give thermal expansion coefficient in material panel........all properties must be defined in mean film temp.