. The steam-engine and other heat-motors. e the pump-valvesare mechanically operated, and for the low vacuum they can be ad-justed only by the sound which the mechanism gives out; but thecurve in general is correct and demonstrates the point. The read-ings were taken down to 18-J of vacuum. Below that point onlyone reading was to be had, , that at 0 Proof. (Fig. 141.) P1V1+ I ~pdv-(p1vc+p2v2-p2Vc) t/Vl P\V\VcV2 ; A = area of card = P\Vi +P1V1 log, v2-piVi log* l>i PlVi dA n PlVc-Pll\-\~Pl logell , PlVc Pi +7- The area = a maximum when log, Vi = log* v2 — 1 + Let pi=14.
. The steam-engine and other heat-motors. e the pump-valvesare mechanically operated, and for the low vacuum they can be ad-justed only by the sound which the mechanism gives out; but thecurve in general is correct and demonstrates the point. The read-ings were taken down to 18-J of vacuum. Below that point onlyone reading was to be had, , that at 0 Proof. (Fig. 141.) P1V1+ I ~pdv-(p1vc+p2v2-p2Vc) t/Vl P\V\VcV2 ; A = area of card = P\Vi +P1V1 log, v2-piVi log* l>i PlVi dA n PlVc-Pll\-\~Pl logell , PlVc Pi +7- The area = a maximum when log, Vi = log* v2 — 1 + Let pi=, d2 = 1, ?v = .03, log, ii =0-1 +.03= (Add and we obtain = , or the logarithmof ten times the required number, .*. Fi = .379.) Hence the jarea is a maximum when Vi = .379. The corresponding value of COXDEXSERS AXD AIR-PUMPS. 271 p2 iromp1Vi=p2v2is pounds, or a vacuum of = X2= 18. r • • • • a© t- 3 •2 / CO © ,8 <3 0 8 10 12 H 1G IS 20 22 24 26 28 30Vacuum in Inches Fig. Fig. Air-pump.—The condensed steam flows continu-ously by gravity from the condenser into the base of the pump 272 THE STEAM-ENGINE AND OTHER HEAT-MOTORS. and is there dealt with mechanically by the conical bucket workingin connection with a base of similar shape. Upon the descent ofthe bucket the water is projected silently and without shock ata high velocity through the ports into the working barrel. However slowly an air-pump with foot- and bucket-valvesmay be running, the pressure in the condenser has to be sufficientlyabove that in the pump to lift the foot-valves, overcome the inertia
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