. Applied thermodynamics for engineers. no heat is lost and nowork is done, the areas BFHXC andBFZD being equal. Along NX, the heat transformed into work is BFHXC - BFXE = FHXA — CAXE, less than that during adiabatic expansion by the amount of work converted back to heat. Considering expansion from X to Z, I /h n \ 1 \\ 1 c !e id Fig. 239. Art. 518 Path as Modified by Friction. NExpansive F= Qi=0, since q = Q^. Nozzle friction decreases the heat drop, the final velocityattained, and the external work done. 519. Allowance for Friction Loss. For the present, we will assumenozzle fricti
. Applied thermodynamics for engineers. no heat is lost and nowork is done, the areas BFHXC andBFZD being equal. Along NX, the heat transformed into work is BFHXC - BFXE = FHXA — CAXE, less than that during adiabatic expansion by the amount of work converted back to heat. Considering expansion from X to Z, I /h n \ 1 \\ 1 c !e id Fig. 239. Art. 518 Path as Modified by Friction. NExpansive F= Qi=0, since q = Q^. Nozzle friction decreases the heat drop, the final velocityattained, and the external work done. 519. Allowance for Friction Loss. For the present, we will assumenozzle friction to reduce the heat drop by 10 per cent. In Fig. 240, whichis an enlarged view of a portion of Fig. 177, let AB represent adiabatic(isentropic) expansion from the condition A to the state B. Lay off BC AB 10 368 APPLIED THERMODYNAMICS and draw the line of constant heat CD. Then D is the equivalent finalH state at the same pressure as that existing at B, andAC represents the heatdrop corrected for by laying offAH. HG = 10 Fig. 240. Arts. 519, 524, 525, 532, the Turbine. and drawing GE to inter-sect the 35-lb. pressureline, we find the point Eon the path AD of thesteam through the may use the new heatdrop thus obtained in de-termining F; or generally, -N if m is the friction loss, The Steam Path -j-^g ^ = (l-m)(9-Q) and If m = , F= Vg V= Vl -m^q- Q. Q> 520. Analytical Relations. The influence of friction in determining the finalcondition of the steam may be examined analytically. For example, let the initialcondition be wet or dry; then friction will not ordinarily cause superheating, sothat the steam will remain saturated throughout expansion. Without friction, thefinal dryness Xq would be given by the equation (Art. 392), Friction causes a return to the steam of the quantity of heat m{q — Q). This in- creases the final dryness by m{q- making it x„ = r{log4 + f|+m(?-G) If the initial condition is superheated to tg,
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