Question

Which of the following boilers has the highest heat transfer capacity?

(a) Subcritical boiler

(b) Critical boiler

(c) Forced circulation boiler

(d) Supercritical boiler

I had been asked this question in a national level competition.

This is a very interesting question from Types of High Pressure Boilers in section Steam Generators & Accessories of Energy Engineering

Answer 1

Right choice is (d) Supercritical boiler

To elaborate: The heat transfer rates of supercritical boilers are large compared to any other boilers. The steam side heat transfer of subcritical is 165000 kJ/m^2hr^oc when the steam pressure and temperature are 180 bar and 538^oC whereas, the steam side heat transfer coefficients of supercritical boiler is about 2,20,200 kJ/m^2hr^oC when the steam is generated at 240^oC.