Thread: Defender additions

Another bump for Travelsick on the water tank question.

Erich

Heat transfer obeys laws of physics. There are 3 modes of heat transfer:

1. Conduction - will not happen because the dry air between the exhaust and tank is a very good insulator. Adding another insulator will not achieve much unless it is much better than air - unlikely, but don't let me stop you. Insulation combats conduction.

2. Convection - heat is transferred to the air in contact with the exhaust, which becomes less dense and rises to where it contacts the surface of the tank. If the heated air is dispersed by vehicle motion or wind this wont be a problem until you stop, but then the exhaust starts to cool - this is where an insulator against the tank may help as a barrier.

3. Radiation - the dominant mode of heat transfer in this application. Polished stainless steel or aluminium is a very good reflector (note that dullbird's black plastic tank does, but Bundalene's stainless tank doesn't suffer from water being heated.

A reflecting shield close to the tank can reflect a lot of the radiation and the air between the shield and tank surface will serve as insulation - just my 2 cents from someone who has has done the calculations to apply this to industrial applications from time to time and observed the results.

The tank material then has to transfer heat to the water. Stainless steel conducts less heat than plain carbon steel, which conducts less than aluminium.

Heat transfer and insulation problems differ between short and long periods of time. Over a long period (we may often be driving for long periods) the temperature will rise across the thickness of insulation and heat transfer will increase. In this situation it is much better expend your effort/$$ to reflecting the radiant heat away and to disperse (ventilation and air flow) air that is heated by the exhaust, than to add insulation.