Tools › Fluids and Heat Transfer › Compressible Flow

Compressible Flow

2 tools in the Fluids and Heat Transfer area.

Compressible Flow Tables

The compressible-flow relations of NACA Report 1135 (Ames Research Staff 1953, Equations, Tables, and Charts for Compressible Flow) for a perfect gas of any specific-heat ratio: isentropic flow (p/p_t, ρ/ρ_t, T/T_t, A/A*, V/a*, q/p_t, the Mach angle and the Prandtl-Meyer angle, eqs. 43–51 and 80), normal shock waves (p_2/p_1, ρ_2/ρ_1, T_2/T_1, M_2, p_t2/p_t1, the Rayleigh pitot ratio and the entropy rise, eqs. 93–102), oblique shock waves (shock angle from the deflection on the weak or strong branch, or the deflection from the shock angle, eqs. 128–145, with the maximum deflection, the sonic limit, Chart 2 and the shock polar), Prandtl-Meyer expansion (eq. 171 and its inverse), and the Fanno and Rayleigh lines of constant-area flow with friction or heat addition. Each mode also solves the inverse problem the report tabulates (Mach number from a pressure, temperature, density or area ratio, from a shock pressure ratio or downstream Mach number, from the Prandtl-Meyer angle, from fL*/D or T_t/T_t*), prints the neighbouring rows in the report's table layout, and, when a static pressure and temperature are entered, the dimensional state (density, speed of sound, velocity, dynamic pressure, total conditions and the state behind the shock). The default is M = 2 in air (γ = 1.4) with a 10° deflection, for which every mode's values are those of the report's Table II.

1 worked example reproduced, listed on the tool page.

Pressure Relief Valve and Rupture Disk Sizing

Required effective orifice area of a pressure relief valve or rupture disk and the API 526 letter that provides it, for gas or vapour (the isentropic-nozzle equation in the API 520 / ASME VIII form, choked or subcritical with the F_2 factor and the back-pressure, combination and discharge coefficients), steam (Napier's form with the superheat ratio computed from IAPWS-IF97 and the published K_N correction, beside the direct IF97 nozzle flux on the equilibrium and metastable paths), liquid (the orifice form with the API viscosity correction solved by iteration), two-phase flashing or frozen flow (Leung's omega method, with omega from the IF97 saturation properties for water), the fire case (wetted-area heat input with the latent heat from IF97, the 29 CFR 1910.106 Table H-10 free-air rates and the 29 CFR 1910.110 LP-gas rates) and atmospheric-tank breathing. Adds the inlet pressure-loss check against the 3 percent rule and the built-up back pressure of the outlet line by isothermal compressible flow, the discharge reaction force from a momentum balance, the rated capacity of the selected orifice, and charts of capacity against set pressure and of the back-pressure factor. The default is air at 150 psig set pressure with 10 percent overpressure and 5,000 lb/h (illustrative).

1 worked example reproduced, listed on the tool page.

Other Fluids and Heat Transfer sections

Pipe Flow · Pumps and Fans · Conduction · Convection · Radiation · Heat Exchangers · Thermodynamic Cycles · Fluid Properties