Upflow/downflow heated tube circulating system

Abstract From the Canadian patent

A fluid flow circuit for a boiler having a combustion chamber and an exhaust passage. In one embodiment there is provided at least one upflow vaporative generating bank module in the exhaust passage and at least one downflow evaporative generating bank module in the exhaust passage positioned, downstream of the upflow module. One or more upper downcomers are connected to a steam drum and supply water to the lower header of the upflow module and to the upper header of the downflow module. If needed the convection pass, wall enclosures can also be fed by the upper downcomers to their upper inlet headers. One or more lower downcomers may be connected to each lower header of the downflow module …