HW5 - A number of simple models have been proposed for the...

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Two Phase 27 1 A number of simple models have been proposed for the modeling of two-phase systems. These include the assumption of homogeneous flow where the phases velocities are assumed to be equal, and an equilibrium model where both phases are assumed to be at thermodynamic equilibrium. Both assumptions impact the computed void, quality and density distributions in the channel. Operating parameters for representative BWR and PWR designs are given below. For the PWR hot channel and the BWR average channel compute and plot: 1) the void and quality distributions 2) the liquid phase enthalpy distribution 3) the mixture density distribution Compare the results obtained using the following models: a) Non-equilibrium, Non-homogeneous flow b) Equilibrium, Non-homogeneous flow c) Homogeneous, Equilibrium Flow (BWR Only) You may assume the saturation properties are constant along the length of the channel and may be evaluated at the system pressure. PRESSURIZED WATER REACTOR PARAMETERS Pressure 2250 psia Coolant Mass Flux 2.50 x 10 6 lbm/hr-ft 2 Core Inlet Temperature 545 F Maximum Core Heat Flux 580,000 Btu/hr-ft 2 Rod Pitch 0.563 inches Rod Diameter 0.422 inches Fuel Height 144 inches Axial Peak to Average Ratio 1.5 The axial heat flux may be taken to be ′′ + qz q z H e () s in = 0 πλ BOILING WATER REACTOR PARAMETERS Core Averaged Heat Flux 144,032 Btu/hr-ft 2 Pressure 1000 psia Coolant Mass Flux 1.42 x 10 6 lbm/hr-ft 2 Core Inlet Temperature 532 F Rod Pitch 0.640 inches Rod Diameter 0.493 inches Fuel Height 146 inches Axial Peak to Average Ratio 1.4 The axial heat flux may be taken to be + + qz q Hz H H ee (- ) ) 0 πλπλ sin
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Two Phase 27 2 SOLUTION Heat Flux Profiles PWR The heat flux profile for the PWR case is given as ′′ + qz q z H e () s in = 0 πλ where for this profile the maximum heat flux occurs at 2 / H and is equal to 0 q . For the hot channel, then 2 0m a x 580,000 Btu/hr-ft qq == . Extrapolation Distance The axial peak to average ratio is defined to be q z q F z ) ( max where max z is the position of maximum heat flux in a particular channel, and q is the axially averaged heat flux in the same channel. Note, that since for any given channel ) ( max z q and q both contain the amplitude 0 q , this parameter cancels and the axial peak to average ratio is only a function of shape. The position of maximum heat flux is that location such that 0 max = z q dz d For this heat flux profile, the maximum heat flux occurs at 2 H , such that a x m a x ( ) 580,000 z q = Btu/hr-ft 2 . The axially averaged heat flux is defined to be dz H z q H dz z q H q e H H + = λ π 0 0 0 sin 1 ) ( 1 + = e e e H H H H H q q ) ( cos cos 0 The axial peaking factor is then + = e e e z H H H H H F ) ( cos
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This note was uploaded on 12/08/2010 for the course NE 402 taught by Professor Doster during the Fall '08 term at N.C. State.

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HW5 - A number of simple models have been proposed for the...

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