[ViLaks]

Hello All,

I am working on estimating the time taken for temperature pull down inside a deep freezer using Fluent.

1. The deep freezer, which is functional, is switched off.
2. The Lid is opened and left open for sometime, as the ambient air enters inside.
3. The lid is closed.
4. The freezer is switched on, whose Te = -20 deg C
5. My aim is to estimate the time taken to cool down the air at 43 deg C (ambient) to -18 deg C. Im assuming entire freezer is filled with ambient air.
6. For starters, my initial condition is air at 43 deg C and the walls are maintained at a constant temperature of -20 deg C. On solving for natural convection using Boussinesq approximation, the time taken for the required pull down is approx. 115 s, say 2 mins. Is this right? I ask this because experimental analysis show it takes around 2 hours. If my result according to the way I have modelled the problem is right, what actually is fluent solving? By the way, I plot area - weighted average of temperature over an iso-surface inside the domain versus flow time, which directly gives the time taken for cooling. Is this interpretation right?
7. My another concern is, once the freezer is switched on, the walls wont be at -20 deg C, as the evaporator needs some time to reach the specified evaporationg temperature. The air temp of 43 deg C reduces simultaneously along with the the wall temp, until wall temp reaches steady state of -20 deg C. The cooling of air continues further. How to model this temperature - time dependence as Boundary condition in fluent.

Thanks in Advance.

With Regards
Vignesh