The Critical Flow Function for Superheated Steam

1964 ◽  
Vol 86 (3) ◽  
pp. 507-516 ◽  
Author(s):  
J. W. Murdock ◽  
J. M. Bauman
Keyword(s):  
Superheated Steam ◽  
Compressibility Factor ◽  
Practical Method ◽  
Ideal Gas ◽  
Critical Flow ◽  
Stagnation Temperature ◽  
Flow Function ◽  
Critical Function ◽  
Inlet Conditions ◽  
Reduced Coordinates

Computations are made of the theoretical critical flow rate of superheated steam through nozzles or other passages. Flow maximization was used in determining the critical function φ=GT11/2/p1. Tabulations of the critical flow function are given for the “superheated vapor” region defined by Keenan and Keyes “Steam Tables” with a pressure limitation of 5000 psia. Two approaches are presented to relate the critical flow function to an ideal state. In the first approach the temperature of the throttled vapor, from inlet conditions, to a very low pressure (p = 0.08854 psia) was used. The second approach utilized the equivalent ideal-gas stagnation temperature that steam would have if its compressibility factor was unity. A dimensionless correlation on reduced coordinates is presented for the second approach, which permits the correlation of steam data to hydrocarbons or other nonideal gases the compressibility factors of which are available as functions of reduced coordinates. A practical method for calculating theoretical critical flow is presented utilizing the properties of steam as taken directly from the Keenan and Keyes “Steam Tables.”

Computation of the Critical Flow Function, Pressure Ratio, and Temperature Ratio for Real Air

1964 ◽  
Vol 86 (2) ◽  
pp. 169-173 ◽  
Author(s):  
Robert M. Reimer
Keyword(s):  
Critical Temperature ◽  
Speed Of Sound ◽  
Critical Pressure ◽  
Pressure Ratio ◽  
Elevated Pressure ◽  
Stagnation Pressure ◽  
Critical Flow ◽  
Stagnation Temperature ◽  
Flow Function ◽  
Temperature Ratio

A method of computing the critical flow function, critical pressure ratio, and critical temperature ratio is presented. Use is made of the NBS Circular 564 tabulated data of the speed of sound, enthalpy, and compressibility. Computations are made for dry real air at stagnation temperature from 60 to 100 F and stagnation pressure from zero to 300 psia. The change in the flow function and ratios is 0.9, 0.5, and 0.4 percent, respectively, over this range. Calculations are also performed at elevated pressure and temperature.

scholarly journals A Design Tool for Supercritical CO2 Radial Compressors Based on the Two-Zone Model

2020 ◽  
Author(s):  
Ihab Abd El Hussein ◽  
Alexander Johannes Hacks ◽  
Sebastian Schuster ◽  
Dieter Brillert
Keyword(s):  
Pressure Ratio ◽  
Compressibility Factor ◽  
Ideal Gas ◽  
Design Tool ◽  
Design Approach ◽  
Maximum Deviation ◽  
Zone Model ◽  
Plausibility Check ◽  
Compressor Inlet ◽  
Inlet Conditions

Abstract In supercritical Carbon Dioxide (sCO2) cycles, the compressor inlet conditions are selected near the critical point where compressibility factor reaches values as low as 0.2. Consequently, conventional compressor design approaches formulated for fluids obeying the ideal gas law are not verified. Therefore, this paper proposes a design approach for sCO2 radial compressors that consists of a performance prediction model in addition to a set of geometry parameters suitable for radial compressors. The compressor model is based on the two-zone modeling approach, in which the Span and Wagner equation of state for CO2 is integrated. At first, the compressor model is presented in addition to the required correlations. Afterwards, a sensitivity analysis is performed on the model main parameters. Thereafter, a plausibility check is performed against experimentally obtained data. Finally, an overall design approach is proposed and its capability to deliver new geometries is assessed by comparing the tool predictions against the results from a verified CFD code for several test cases. The Comparison shows a maximum deviation of less than 2 percent for the pressure ratio and less than 3.5 percentage points for the efficiency. The results indicate the ability of the proposed approach to predict the performance of sCO2 compressor from correlations that originate from experience with conventional fluids. Additionally, the adopted geometric relations proved its applicability to sCO2 compressors.

GENERALIZATION OF AN ANALYTICAL TWO-PHASE STEAM FLOW CALCULATOR TO HIGH-PRESSURE CASES

2006 ◽  
Vol 30 (4) ◽  
pp. 581-595
Author(s):  
M. J. Kermani ◽  
M. Zayemouri ◽  
M. Saffar Avval
Keyword(s):  
High Pressure ◽  
Local Equilibrium ◽  
Low Pressure ◽  
Ideal Gas ◽  
Steam Flow ◽  
Stagnation Temperature ◽  
Two Phase ◽  
Dimensional Parameter ◽  
Phase Mixture ◽  
Experimental Values

Extension of a recently developed analytical two-phase steam flow calculator to high pressure cases is performed in this paper. The initial solution, obtained in earlier study was developed for low pressure cases. In low pressure cases, the vapor portion of the two-phase mixture reliably obeys the ideal gas Equation of State (EOS). In the present high pressure study, real gas effects are included using the more suitable EOS of “Lee-Kesler”. The model similar to the low pressure model assumes local equilibrium between the phases, in which condensation onsets as soon as the saturation line is closed. Before the condensation onset, the stagnation properties echo those at the inflow. However, beyond the condensation onset, the transfer of latent heat toward the vapor portion of the two-phase mixture rises its stagnation temperature. To evaluate this rise in the vapor portion stagnation temperature, a non dimensional parameter ζ is defined. Comparison for low- and high-pressure cases between the present analytical solution and the published experimental values in the literature show very good agreement.

Calculation Method of Natural Gas Compressibility Factor and its Application in Pipeline Trade

2014 ◽  
Author(s):  
Xiaocui Tian ◽  
Xiaokai Xing ◽  
Rui Chen ◽  
Shubao Pang ◽  
Liu Yang
Keyword(s):  
Natural Gas ◽  
Compressibility Factor ◽  
Economic Benefits ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Pipeline System ◽  
Natural Gas Pipeline ◽  
Gas Volume ◽  
Gas Compressibility ◽  
Simplified Formula

In the custody transfer metering of natural gas, it’s necessary to transform gas volume from metering state into standard state. Natural gas is non-ideal gas, and its compressibility factor varies with different components, temperature and pressure. So the accuracy of its calculation has direct impact on that of natural gas metering, and then affects the economic benefits of the enterprise [1]. According to related standard of China, in the custody transfer metering of natural gas, the formula stipulated by AGA NO.8 should be adopted to calculate compressibility factor. But the components of natural gas must be monitored at all times when this method is used, and the calculation process is complicated. In practical operation of natural gas trade, compressibility factor changes because of frequent adjustment of pipeline operating conditions. In order to simplify the calculation, simplified formula is applied to calculate compressibility factor generally, but it’s difficult to guarantee the accuracy at the same time. In this paper, the simplified formula, which is used for calculating natural gas compressibility factor of a joint-stock natural gas pipeline of CNPC, is modified with the standard formula stipulated by AGA NO.8. After the modification, an empirical formula of compressibility factor calculation applicable to this pipeline system is proposed, whereby the accuracy of compressibility factor calculation is improved. When the modified one is applied to natural gas trade, the accuracy of metering is improved likewise.

scholarly journals THE INFLUENCE OF PRESSURE AND TEMPERATURE ON THE COMPRESSIBILITY FACTOR

2021 ◽  
Vol 2(73) (2) ◽  
pp. 13-21
Author(s):  
George Iulian Oprea ◽  
◽  
Artemis Aidoni ◽  
Ioana Cornelia Mitrea ◽  
Florinel Dinu ◽  
...  
Keyword(s):  
Natural Gas ◽  
Entire Range ◽  
Compressibility Factor ◽  
Ideal Gas ◽  
Calculation Methods ◽  
Natural Gases ◽  
Canadian Association ◽  
Compression And Expansion ◽  
Gas Compressibility ◽  
Reduced Pressures

The natural gas compressibility factor indicates the compression and expansion characteristics of natural gas under different conditions. It is a thermodynamic property used to take into account the deviation of the behaviour of real natural gases from that of an ideal gas. Compressibility factor, Z, values of natural gases are necessary for most petroleum gas engineering calculations. In this study, a comparison between five different calculation methods is presented to determine this critical parameter for the same natural gas at different conditions (pressure and temperature), using Canadian Association of Petroleum Producers, Azizi, Behbahani and Isazadeh, Dranchuk- Purvis- Robinson, Dranchuk-Abu-Kassem and Standing- Katz methods. The correlations are based on the equation of state are often implicit because they require iteration. Many correlations have been derived to enhance simplicity; however, no correlation has been developed for the entire range of pseudo-reduced pressures and temperatures. Azizi, Behbahani and Isazadeh’s method was found to have the biggest error as a result obtained for T=20° C, and p=20 bar is no longer in the field of applicability.

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