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Full text of "The Flow Of Gases In Furnaces"

HEAT CAPACITY AND  CALORIFIC INTENSITY CURVES   349
values of fuels, as determined by the calorimeter or by computa-
tion, but the temperature obtainable by the use of any particular
source of heat energy depends upon so many variables that it
cannot be reduced to tabular form. Experiment and practice
have developed a certain amount of knowledge regarding the tem-
peratures obtainable, but this is an uncertain guide regarding
the temperature effects which may be expected under different
conditions.
The temperature obtainable by the oxidation of a combusti-
ble depends upon:
(a) The quantity of heat released by the oxidation of a unit
of combustible;
(6) The oxygen supply or the amount of air used;
(c)   The temperature of the fuel and air supply at the point
of combination;
(d)  The heat capacity of the products of combustion;
(e)   The velocity of the reaction of combustion;
(/)   The combustion chamber;
(g) The completeness of the reaction.
Each one of these seven important variables has a considerable
effect upon the temperature produced, a is readily obtainable.
b and c are susceptible of control and in turn bring d under control.
The problem may be solved by making certain assumptions regard-
ing the other variables. These assumptions are:
1.  That complete, instantaneous combustion occurs;
2.  That the total amount of heat released is contained in the
products of combustion, i.e., that combustion occurs
in an athermal chamber which does not absorb or
give off heat.
It is impossible to realize either of these assumptions in practice,
but they permit the computation and plotting of curves which
supply a large amount of " relative " information regarding the
temperature possibilities of a combustible under a variety of
conditions. True, the values are only approximate, only relative,
the assumed conditions impossible, but at the same time these
curves permit a very close approximation of the results obtained
in practice and of the effect of variations in operating conditions
upon the temperature realized. There is a time element in the