### How does temperature difference affect the rate of heat transfer?

For conductive and convective heat transfer, the rate of heat transfer is proportional to the the temperature difference; if you double the difference you will double the rate of heat transfer. For radiative heat transfer, the rate of heat transfer is proportional to the difference of the 4th powers of the absolute temperatures.

### What is radiation in heat transfer?

Radiation in heat transfer is one of three known modes of heat transfer: conduction (as heat transfer in solids and less effective in liquids)), Convection (as in liquids and gases), and radiation (that not necessarily require a medium for the transfer). Heat of sun is transferred to us in the vacuum space by radiation heat transfer.

### How does transient heat transfer differ from steady state heat transfer?

In transient heat transfer, the rate of heat transfer is changing with time. By definition, in steady-state heat transfer, the rate of heat transfer does NOT change with time. In the real world, heat transfer starts out as transient and then approaches steady-state with time until the difference between the actual and the ideal becomes negligible or until thermal equilibrium is approached.