Airotherm is a combination of shell-in-shell and tube-in-shell type hot air generator. It has four concentric shells. The furnace shell has a blind end where the flue gases are reversed over the flame itself forming the 1st and 2nd pass. The 3rd pass is situated between the 2nd &3rd shell from where the flue gases, led via a duct, to the tube-in-shell type heat exchanger. The 4th & 5th pass are through tubes of the tube-in-shell heat exchanger. The burner assembly is bolted on a removable inner cover plate. The combustion air is led to an air register which is formed by the annular space of the inner cover and the outer cover. The air going for combustion is thus preheated.
The fresh air has four passes to absorb heat from the flue gases. The 1st pass of the cold air enters around the 5th pass of the flue gases. Likewise all the subsequent passes of the air and flue are in counter current mode enabling maximum heat transfer. The final 4th pass of the fresh air which is at the last leg of the heat transfer path wraps around the furnace in circular path absorbing the heat attaining the required temperature for the process. The max temp for this model of heater is 300 The design of the heater is made simple and operator friendly.