ETBX Converging-Diverging Nozzle Flow Module

Converging-Diverging Nozzle Flow

An EngineersToolbox Calculation Module

Summary

This module is used to compute the maximum gas flow rate and flow regime in a converging-diverging nozzle. This module can also be applied to compute the maximum allowable mass flow rate of a gas through a given cross-section.

Background Information

The flow behavior through a converging-diverging nozzle as depicted in Figure 1 is computed.

This module calculates the maximum mass flow rate through the throat section of the nozzle using equation (1). The flow conditions at the exit of the nozzle are also computed. The maximum allowable mass flow rate of gas through a cross-section can be computed by setting the cross-sectional area to be same as the throat area.

(1)

where m is mass flow rate, P_t is supply total pressure, T_t is total temperature, r is gas specific heat ratio, R is universal gas constant, A* is throat area and n is computed using equation (2),

(2)

Input

The inputs for this module are depicted in Figure 2. The inputs consist of geometric dimensions, fluid flow properties and inflow conditions. The total inflow pressure and temperature is specified.

Figure 2: ETBX inputs for nozzle flow computations.

Results

The results are displayed using standard ETBX output window shown in Figure 3. The output consists of mass flow rate and flow conditions at the nozzle exit.

Figure 3: ETBX heat transfer coefficient module outputs.

References

1. S.M. Walas, Chemical process equipment, selection and design, Butterworth-Heineman publication in chemical engineering, 1990.

2. J.E. John, Gas dynamics, Allyn and Bacon, Inc. 1969.

3. J.D. Anderson, Modern compressible flow, Mc Graw-hill, 1982.

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