Abstract
An advanced-type compact water-tube boiler has been designed on the basis of the new concept of cooling flame by tube-nest in the furnace, and is referred to as tube-nested combustor. It realized drastic reduction in boiler size as well as (NO)_x emission. In a convective heat transfer section downstream the tube-nested combustor, the flow area channel is reduced and the finned tubes are used to increase the heat transfer rate. In this section, heat transfer and flow characteristics are different from the combustion chamber owing to the existence of forward facing step in the flow area. This paper described the result of flow visualization and measurement of heat transfer coefficient in such section.
