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In most circumstances, the two phases are taken as having the same pressure; but allowance can be made for the existence of a contact pressure between solid particles, when their volume fraction is close to unity.
This extra pressure is not shared by the fluid within which they move.
The IPSA method has been used in PHOENICS since 1981.
Click here for a lecture on IPSA.
Applications of the use of this method include the simulation of:-
Contours of volume fraction of steam, formed from water entering at the bottom of the cylindrical vessel
The steam-generation pattern is not symmetrical because the temperature of the water in the immersed U-tubes falls between inlet and outlet.
The water enthalpy, measured above a base value corresponding to the entry temperature, just below boiling point. The water becomes super-saturated where the heating rate is most intense.
Contours of upward velocity of steam. The flow pattern is far from being axi- symmetrical.
Contours of upward velocity of water. Note that the water velocities are smaller than the steam velocities, because of inter-phase slip.
The distribution of pressure.
The pressure diminishes with increase in height partly because of gravity and partly to accelerate the steam-water mixture.
The IPSA method is used so as to simulate the different but interacting motions and exchanges of heat and mass between the coal and the burning gases.
Gas-phase temperature contours
Solid-phase temperature contours in the coal-fired furnace.
Note that the gas and coal temperatures are not the same.