FLOW THROUGH ORIFICE 27
produce a depression at the bottom of the regenerator which will
be equal, neglecting the resistance to their flow, to
2.X 273
To sum the matter up, when a chamber is filled with a light
gas and the line at which its pressure is in equilibrium with the
atmospheric pressure is at or below the lowest point of the chamber,
the pressure in the upper part of the enclosure will be higher
than atmospheric pressure. If the line of equilibrium with the
atmospheric pressure passes through or above the upper part of
the chamber, the pressure at the lowest point in the chamber will
be negative. In other words: when a light gas ascends it will
create a pressure; conversely, to force a light gas to pass down-
ward, it is necessary to create a depression.
V. THE APPLICATION TO HOT GASES OF THE LAWS FOR THE
FLOW OF LIQUIDS THROUGH AN ORIFICE IN THE BOTTOM
OF THE RESERVOIR.
For water flowing into air the formula is:
in which Q= the volume of liquid flowing;
h= the head of the liquid above the orifice;
= the theoretical velocity of flow;
co = the area of the orifice;
/ci = the coefficient for the contracted vein, that is, the
ratio between the area of the contracted vein and
co (generally KI = 0.64) ;
/C2=the coefficient of velocity, that is, the ratio between
the actual velocity at the contracted vein and the
theoretical velocity (generally /C2 = 0.97).
If it is desired to apply this formula to the flow of kerosene
through an orifice in the top of a bell glass immersed in a vessel of
water, it is necessary to determine exactly what is meant by the
head A.