Hi Louie,

It's really reverse thermo syphoning.

Thermo syphoning was used in early motor vehicles and stationary engines and domestic hot water systems which had heating coils in the wood stove firebox to circulate the radiator fluid and water out of the hot water storage tank and through the heating coil. The hot water in the engine or heating coil was lighter than the cold in the radiator or storage tank and the density imbalance circulated the water.

I am hoping that the warm air in the box will rise and the cooler air behind the tank fall thereby creating a circulation. There's considerably more insulation on the tank back side now so the heat loss on that side should be less.

I have built a vertical slot into the aft end into which I can fit a computer fan if I need to force circulate as well.