ARTIFICIAL REFRIGERATION AND ICE MAKING. LXXI. 
ducing the air at a.much lower temperature @,, and this is 
heated up to the temperature 7,, increasing the work done by 
nw area H DC where @, is the absolute temperature of the 
cold air introduced from the expansion cylinder to the cold 
chamber. The process is thermodynamically wasteful to the 
extent shown by the area of the triangle # D C, where £ D is 
usually about twice A D. Again the compressor aspirates air at 
a ~ ace pepe 7, and compresses it with a rise of temperature 0,. 
If this occurs adiabatically the rise is 9, -7, which is equal to 
T2 —6., hence the heat is rejected between the temperatures 7, 
and #, and the increase in work done is shown by the triangle 
A F B which is equal to the triangle DC #. Hence the whole 
orig representing the work done in a dry air machine assuming 
adiabatic expansion and compression is fA # C, or about three 
times the area A BC D. 
But actually the result is worse than represented by this area 
‘ there is an interchange of heat through the cylinder walls and 
€ work done is somewhat as shown by the dotted area A FC, 
= 1 Or = four times A BOD. The relatively large cylinders 
eye in the dry air machine as compared with the vapour 
Machines increases the work required to be done beyond that 
=" by the diagram A ’'C,£,D. In the “Linde,” “Hercules,” 
; “tie ca we, the compressed liquid flows from the cylinder 
i, e regulating valve to the cooler., and a portion of this 
a S ab i she tose before it is admitted to the expansion coils, 
involves a loss in efficiency, and it is the object in all refriger- 
ating plant to minimise this 
loss. It may be represented 
by an addition to the Carnot 
V% A B cycle ABCD of A £ D, 
where A E D represents the 
increase in the work done in 
Ty consequence of the heat units 
& oO od abstracted at decreasing tem- 
perature. 
