Temperature of shipping container

[woody726]

How do I calculate the surface temperature of a shipping container's roof over 24 hours? All weather and sun parameters are known and I use an energy balance equation, but the contribution of the inside of the container causes the calculated values (rise too fast) to differ from the measured ones.

 

[dauto]

• Can you give more details of what your assumptions are? How are we supposed to help you fix your model when we don't know anything about your model?
• The unknown contentents of the containers will produce - well - unknown effect on the result

 

[SteamKing]

Sometimes, the contents of shipping containers have been known to ignite (see calcium hypochlorite). That could really throw off your calculations.

If you are treating the container as a 'black box' (where the contents are unknown), I don't know if it is feasible to construct a very accurate model, since you have no practical way to account for the heat absorption of the contents during the day.

 

[woody726]

The container is empty (air), and I use a model considering solar (shortwave) absorption, longwave atmospheric irradiance aborption, graybody emission from the container and convection. But the contribution of the inside of the container is what I am not sure of since currently the roof is considered simply as a sheet of metal. I assume net heat flux=0 for a given set of environmental parameters that are known for every minute over 24 hours: air temperature, solar irradiance, relative humidity, air pressure, wind velocity. The thermodynamic parameters for the container roof are also know: specific heat capacity (600 J/(kgK)), conductivity (50 W/(mK) ), density (7000 kgm-3), short (0.88) and longwave (0.9) absorption coeff, emissivity (0.88), and thickness (3mm).