Presentation on theme: "Assumptions: Incompressible substance, B. Negligible heat transfer"— Presentation transcript:
1 SFEE for liquid nozzles, pumps and water turbine: toward the Bernoulli equation Assumptions:Incompressible substance,B. Negligible heat transferC. negligible friction despite “the rubbing liquid layers”D. B and C leading to near isothermal operation.
2 SFEE applied to heat exchangers hot (h)cold (c)Take CV enclosing the stream thatis hot at inletTake CV enclosing the stream thatis cold at inlet
3 Mixing chambers or “direct contact heat exchangers” 321Conservation of massConservation of energy
4 Throttling devices Flow restriction A device that causes a drop in pressureby restricting the flow passage canbe termed a throttling device.
5 Throttling devices non-quasiequilibrium. Flow restriction Slow flows, DKE effects can beneglectedCapillary tube expansionvalve used to drop refrigerantpressure and temperatureThrottling is anisenthalpic process.Negligible heat transfer(small devices)Fundamentally,non-quasiequilibrium.
6 Physical effects in throttling From upstream to downstream section:Pressure (P) drops (due to fluid-solid friction)Velocity increases slightlySpecific volume increasesTemperature of fluid may increase or decrease or remain same (Joule Thomson effect). The fluids for which temperature decreases are candidates for use in refrigerators.Ideal gas temperature remains same.Incompressible substance temperature increasesThrottling of a refrigerant on T-v / P-v diagram (on board).
7 Throttling calorimeter to measure steam quality P-v diagram?Board!
8 Reading assignmentCyclic processes in engineering: “Power cycles” and “Refrigeration cycles”. (Moran Section 2.6, next slide)System integration of steady flow devices to execute composite processes and power/refrigeration cycles (Subsection titled “System Integration” of Section 4.3, next slide)Special topics (not in book, may be covered in lecture)Differential form of the steady flow energy equationThe quasi-equilibrium steady flow heat transfer.
9 First law analysis of a simple power cycle For the closed system shown:Do steady state open system analysis ofall components. Boilers/condensersare heat exchangers where one fluidundergoes (here the working fluid of thepower plant, usually steam)undergoes vaporization/condensationThermal efficiencyof a power plant