On converting tins formula into terms of the English
system of measures (_i.e._, _l_ feet, Q cubic feet, and
_h_ and _d_ inches) it becomes
(i) d = 0.045122(Q^2_l/h_)^(1/5)
At first sight this formula does not appear to differ greatly from
Bernat's, the only change being that the constant is 0.045122 instead of
0.05552, but the effect of this change is very great--for instance, other
factors remaining unaltered, the value of Q by Morel's formula will be
1.68 times as much as by Bernat's formula. Transformations of Morel's
formula which may sometimes be more convenient to apply than (i) are:
(ii) Q = 2312.2(_hd^5/l_)^(1/2)
(iii) _h_ = 0.000000187011(Q^2_l/d^5_)
and (iv) _l_ = 5,346,340(_hd^5_/Q^2)
In order to avoid as far as possible expenditure of time and labour in
repeating calculations, tables have been drawn up by the authors from
Morel's formulae which will serve to give the requisite information as to
the proper sizes of pipes to be used in those cases which are likely to
be met with in ordinary practice. These tables are given at the end of
this chapter.
When dealing with coal-gas, it is highly important to bear in mind that
the ordinary distributing formulae apply directly only when the pipe or
main is horizontal, and that a rise in the pipe will be attended by an
increase of pressure at the upper end.
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