Total BTU in superheated steam at temperature of T.
Units. Degrees Fahrenheit and BTU per pound.
SUPERHEATERS.
1). 5 BTU's will be transmitted to the steam for each per square foot of heating surface per degree of
difference in temperature between the flue gases and the steam.
2). E x S x T ( Z - A) / 5
Where:- A = temperature of boiler + half the required superheat E = Weight of water evaporated per hour ( in pounds) S = specific heat of superheated steam T = degrees of superheat required Z = mean temperature of gases before and after the superheater.
Expansion of superheated steam.
The equation for the expansion of steam with rise of temperature, (known as Callendar's Equation) for superheated steam:-
V = 1.253 ( H - 835 ) / P
V = specific volume of superheated steam, cu ft/lb. H = total heat of superheated steam B.t.u. /lb. P = pressure of superheated steam lb./sq. in absolute
