# Calculating Heat Transfer (Thermal Radiation) to a Shipping Container

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1. Oct 6, 2014

### thomas82

Hello,

I am trying to calculate the thermal radiation heat transfer to a shipping container which would be painted white.

The purpose is to size an air conditioner for equipment, not living conditions. I have already calculated heat from the other sources. The desired internal temperature is 30 degrees.

The container has dimensions 4.636 m x 2.591 m x 2.438 m (There is an internal wall) which implies three sections could face the sun at any given time, for a maximum surface area of 29.6 m2

On my first attempt I used an equation based on the Stefan-Boltzmann Constant:

Q = ε σ (Th4 – Tc4) A

The amount I calculated was 1953 W, But I've been told this equation is invalid in this context.

On my second attempt I used the nominal irradiance and just the roof area. I used an emissivity value of 0.4.

800 W/m2 x 11.2m2 x 0.4 = 3584 W

This value is very high and the process is hugely simplistic given that I'm ignoring solar geometry and the specifics of the location entirely. Also, the intention is not to remove all the heat, but I can't figure out how to separate it into a component which would allow for 30 degrees worth of heat to remain.

Can anyone direct me to a site (or provide the step by step equations) that could lead to a reasonable approximation for this application? You're also welcome to comment on how I've approached the problem.

Thank you,

Thomas

2. Oct 7, 2014

### SteamKing

Staff Emeritus
This is why HVAC engineers were created. They do calculations like this every day. Find an HVAC engineer and make him/her happy.