Presentation on theme: "Assumptions: Incompressible substance, B. Negligible heat transfer"— Presentation transcript:
1SFEE 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.
2SFEE 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
3Mixing chambers or “direct contact heat exchangers” 321Conservation of massConservation of energy
4Throttling devices Flow restriction A device that causes a drop in pressureby restricting the flow passage canbe termed a throttling device.
5Throttling 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.
6Physical 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).
7Throttling calorimeter to measure steam quality P-v diagram?Board!
8Reading 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.
9First 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