MECH 213 - 9.26.07

MECH 213 - 9.26.07 - o on left there is an initial...

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MECH 213 – September 26, 2007 work output device o Turbine Work Input Devices o Compressors o o Aircraft Propellers o Pumps o Marine Propellers Q net.in dot – W net.out dot = –Σm in dot(θ) in + Σm out dot(θ) out o If adiabatic turbine/compressor Qdot 0 Usually neglect potential energy (assume small) Neglect kinetic energy -Wdot = mdot(Δh) if Δke is given in the problem -Wdot = mdot(Δh + Δke) if heat loss/gain is given or wanted Qdot – Wdot = mdot(Δh + Δke) o Incompressible devices (pumps, fans, hydro turbines, wind turbines) Δh = Δu + pΔv + vΔp (pΔv goes to 0) Iff isentropic: Δu goes to 0 Δh = pΔv + vΔp -Wdot = mdot(vΔp) = mdot(Δp/ρ) Throttling device – any device in the fluid flow whose purpose is to bring about pressure reduction
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Unformatted text preview: o on left there is an initial velocity, specific volume, enthalpy o at center flow is deflected by a stopper with increasing area as you move up o on the right is a final velocity with a new specific volume, and new enthalpy o If v 1 = v 2 if incompressible Diameter is equivalent at either side V 1 = V 2 ke Assume Qdot Assume Wdot Assume pe ~ 0 0 = mdot(h) h = 0 o h 2 = h 1 o state 2 = (h 2 h f )/h fg Chapter 5 #195E o 15psia, 20F, 10 ft 3 /s o 100psia, Wdot = -45 hp o Find mdot, T 2 o Assume adiabtatic No mention of heat o Need saturation tables and superheat tables o mdot = AV = V o wdot = mdot(h) 45hp(conversion) = mdot(h 2 h 1 ) solve for h 2...
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MECH 213 - 9.26.07 - o on left there is an initial...

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