Hi,
That 70% quality... that would be a mixture of 70% steam + 30% water. What's the application? I've never heard of an application for WET steam like that.
Or would that be boiler efficiency with the fuel you plan to burn?
The heat transfer rate depends on many factors but I would suggest that boiler design is the main one.
But, if your looking for a ballpark type of figure, I would say that 21 W/cm2 is in the range of typical industrial boilers (about 66,000 BTU/h*ft2).
Paul
The boiler itself could be $US 5 to 10 Million (depends on aux. equipement). Installation would depend where it needs to go, new installation? (many $$$), replace an old boiler? (fewer $$$), use existing controls? or a new steam plant?. Boiler auxilliaries are extra (fuel and feed water...