Title and Link to Calc:

Compressible Fluid Flow : Flow in an Ideal Nozzle : CFF-CRFOF-0005

Description:

Calculates Flow in an Ideal Isentropic Nozzle

Alternative Descriptors:

Isentropic Flow in Nozzles, Ideal Gas Flow in Frictionless Nozzles, Adiabatic Flow in Nozzles

Calc Number:

CFF-CRFOF-0005

Calc Status:

Beta

Reference:

Introduction to Chemical Engineering Thermodynamics, 3rd Edition, Smith & Van Ness, pgs. 466-470

Reference Example(s) Modeled/Generalized:

Calc Origination Date:

02/22/2006

Calc Originator:

RBC

Calc Revision History:

Calc Guidelines:

Calculates the mass flow rate in an ideal nozzle. Flow is considered to be isentropic. The fluid is considered to behave as an ideal gas. Critical pressure ratio is determined per Eq. 10-44 of the above reference. If P2 from this equation is less than DPA below, then the flow is subsonic and DPA is used in Eq. 10-42 (DPA=P2) to calculate the throat velocity. If P2 is greater than DPA then the flow is sonic and P2 from Eq. 10-44 is used to calculate the throat velocity in Eq. 10-42. Upstream velocity is assumed to be zero (u1=0).

Access:

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Variables:

Variable Description - Description of the variable
Variable Label Description - The description of the variable as it appears in the calc.
Variable Calc Name - The calc internal variable name
Variable Units - The units for the variable
Variable Calc Upper Limit - The highest allowed value in the calc.
Variable Calc Lower Limit - The lowest allowed value in the calc.
Variable Type - Either "Output" or "Input"
Variable Format - Real Number, Text, or Integer
Variable Notes - Other comments about the variable

Variable Description: Mass flow rate in the nozzle
Variable Label Description: Nozzle Discharge Rate
Variable Calc Name: WRLM
Variable Units: LB/SEC
Variable Calc Upper Limit: 10000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Ratio of Absolute Downstream Pressure to Absolute Upstream Pressure
Variable Label Description: [Downstream P]/[Upstream P] Ratio
Variable Calc Name: DPRA
Variable Units:
Variable Calc Upper Limit: 1
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: Ratio of the upstream pressure to the pressure at nozzle outlet. Pressure in the nozzle, before discharge, may not necessarily be the same as the downstream pressure.

Variable Description: Critical Pressure Ratio
Variable Label Description: Critical Pressure Ratio
Variable Calc Name: CPR
Variable Units:
Variable Calc Upper Limit: 1
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Pressure at Nozzle Throat
Variable Label Description: Nozzle Throat Pressure
Variable Calc Name: DPRE
Variable Units: PSIA
Variable Calc Upper Limit: 10000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Temperature at Nozzle Throat
Variable Label Description: Nozzle Throat Temperature
Variable Calc Name: DTEM
Variable Units: R
Variable Calc Upper Limit: 10000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Comments
Variable Label Description: Comments
Variable Calc Name: COM
Variable Units:
Variable Calc Upper Limit:
Variable Calc Lower Limit:
Variable Type: Output
Variable Format: TEXT
Variable Notes: Displays "Input(s) out of range." if an entered input variable(s) are out of range. Displays "Output(s) out of range." if an output variable exceeds its range. The "out of range" variable(s) are displayed in yellow. The limited range values are used in the calculation, not the "out of range" value(s). Displays "Sonic Velocity" when sonic velocity occurs at the end of the nozzle. Displays "Subsonic Velocity" when velocity is subsonic at the end of the nozzle.

Variable Description: Inside diameter of nozzle at discharge point
Variable Label Description: Nozzle Inside Diameter
Variable Calc Name: TID
Variable Units: IN
Variable Calc Upper Limit: 24
Variable Calc Lower Limit: 0.05
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Temperature of Fluid at Entrance of Nozzle
Variable Label Description: Upstream Temperature
Variable Calc Name: UTEM
Variable Units: R
Variable Calc Upper Limit: 10000
Variable Calc Lower Limit: 1
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Fluid Specific Gravity Relative to Air
Variable Label Description: Fluid Specific Gravity
Variable Calc Name: FSG
Variable Units:
Variable Calc Upper Limit: 100
Variable Calc Lower Limit: 0.01
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Nozzle Upstream Pressure or Stagnation Pressure (Pressure at zero velocity / infinite area)
Variable Label Description: Upstream Pressure
Variable Calc Name: UPA
Variable Units: PSIA
Variable Calc Upper Limit: 10000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Nozzle Downstream Pressure
Variable Label Description: Downstream Pressure
Variable Calc Name: DPA
Variable Units: PSIA
Variable Calc Upper Limit: 10000
Variable Calc Lower Limit: 0.01
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Isentropic K
Variable Label Description: Isentropic K
Variable Calc Name: ISK
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 1
Variable Type: Input
Variable Format: REAL
Variable Notes: Ratio of heat capacities (Cp to Cv)

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