There are several factors that influence the natural circulation in a watertube boiler. These are:
A ) The height of the steam drum above the bottom drum or header.
B ) The amount of heat applied to the tube. The hotter the tube becomes, the more steam bubbles are formed, creating more mass differential and thus more circulation.
C ) The operating pressure of the boiler. As boiler pressures increase, the density of the steam increases
D ) The cleanliness of the tubes can also affect circulation.
E ) All of the above
Answer: E