## Gas Domain

To view the complete domain source file, at the MATLAB® Command prompt, type:

`open([matlabroot '/toolbox/physmod/simscape/library/m/+foundation/+gas/gas.ssc'])`

Abbreviated gas domain declaration is shown below, with intermediate lookup table values omitted for readability.

```domain gas % Gas Domain % Copyright 2016-2019 The MathWorks, Inc. parameters gas_spec = foundation.enum.gas_spec.perfect_gas; % Gas specification % 1 - perfect_gas % 2 - semiperfect_gas % 3 - real_gas % Perfect gas properties R = {0.287, 'kJ/(kg*K)'}; % Specific gas constant Z = {1, '1' }; % Compressibility factor T_ref = {293.15, 'K' }; % Reference temperature for gas properties h_ref = {420, 'kJ/kg' }; % Specific enthalpy at reference temperature cp_ref = {1, 'kJ/(kg*K)'}; % Specific heat at constant pressure cv_ref = {0.713, 'kJ/(kg*K)'}; % Specific heat at constant volume mu_ref = {18, 'uPa*s' }; % Dynamic viscosity k_ref = {26, 'mW/(m*K)' }; % Thermal conductivity Pr_ref = {0.692307692307692, '1' }; % Prandtl number % Semiperfect gas properties T_TLU1 = {[150:10:200, 250:50:1000, 1500, 2000]', 'K'}; % Temperature vector log_T_TLU1 = {[ 5.01063529409626 5.07517381523383 ... 7.60090245954208 ], '1'}; % Log temperature vector h_TLU1 = {[ 275.264783730547 285.377054177734 ... 2377.14064127409 ], 'kJ/kg'}; % Specific enthalpy vector cp_TLU1 = {[ 1.01211492398124 1.01042105529234 ... 1.24628356718428 ], 'kJ/(kg*K)'}; % Specific heat at constant pressure vector cv_TLU1 = {[ 0.725174216111164 0.723480347422265 ... 0.959342859314206 ], 'kJ/(kg*K)'}; % Specific heat at constant volume vector mu_TLU1 = {[ 10.3766056544352 10.9908682444892 ... 68.0682900809450 ], 'uPa*s'}; % Dynamic viscosity vector k_TLU1 = {[ 14.1517155766309 15.0474512994325 ... 114.486299090693 ], 'mW/(m*K)'}; % Thermal conductivity vector Pr_TLU1 = {[ 0.742123270231960 0.738025627675206 ... 0.740982912785154 ], '1'}; % Prandtl number vector a_TLU1 = {[ 245.095563145758 253.217606015000 ... 863.440849227825 ], 'm/s'}; % Speed of sound vector int_dh_T_TLU1 = {[ 0 0.0652630980004620 0.126478959779276 ... 2.79681971660776 ], 'kJ/(kg*K)'}; % integral of dh/T vector % Real gas properties % Default gas property tables for dry air % Rows of the tables correspond to the temperature vector % Columns of the tables correspond to the pressure vector T_TLU2 = {[150:10:200, 250:50:1000, 1500, 2000]', 'K' }; % Temperature vector p_TLU2 = {[0.001,0.005,0.01:0.01:0.1,0.12,0.15,0.2,0.5,1,2,5,10]','MPa'}; % Pressure vector log_T_TLU2 = {[ 5.01063529409626 5.07517381523383 ... 7.60090245954208 ], '1'}; % Log temperature vector log_p_TLU2 = {[ 9.21034037197618 9.90348755253613 ... 16.1180956509583 ], '1'}; % Log pressure vector log_rho_TLU2 = {[ -1.45933859209149 -0.765580954956293 ... 2.84006136461620 ], '1'}; % Log density table s_TLU2 = {[ 3.85666832168988 3.65733557342939 ... 4.66584072487367 ], 'kJ/(kg*K)'}; % Specific entropy table h_TLU2 = {[ 276.007989595737 275.926922934925 ... 2386.79535914098 ], 'kJ/kg'}; % Specific enthalpy table cp_TLU2 = {[ 1.00320557010184 1.00416915257750 ... 1.24767439351222 ], 'kJ/(kg*K)'}; % Specific heat at constant pressure table cv_TLU2 = {[ 0.715425577953031 0.715655648411093 ... 0.960303115685940 ], 'kJ/(kg*K)'}; % Specific heat at constant volume table mu_TLU2 = {[ 10.3604759816291 10.3621937105615 ... 68.3249440282350 ], 'uPa*s'}; % Dynamic viscosity table k_TLU2 = {[ 14.0896194596466 14.0962928994967 ... 114.905858092359 ], 'mW/(m*K)'}; % Thermal conductivity table Pr_TLU2 = {[ 0.737684026417089 0.738165370950116 ... 0.741888050943969 ], '1'}; % Prandtl number table a_TLU2 = {[ 245.567929192228 245.496359667264 ... 878.939999571000 ], 'm/s'}; % Speed of sound table log_drho_dp_TLU2 = [ -10.6690690699104 -10.6678475863467 ... -13.2956456388403 ]; % Log derivative of density with respect to pressure table log_drho_dT_TLU2 = [ -6.46809263806814 -5.77245144865022 ... -4.77782516923660 ]; % Log derivative of density with respect to temperature table drhou_dp_TLU2 = [ 5.41617782089664 5.42024592837099 ... 3.03095417965253 ]; % Derivative of internal energy per unit volume with respect to pressure table drhou_dT_TLU2 = {[ -0.195280173069178 -0.391714814336739 ... 1.27305147462835 ], 'kJ/(m^3*K)'}; % Derivative of internal energy per unit volume with respect to temperature table pT_region_flag = foundation.enum.pT_region_G.from_props; % Valid pressure-temperature region parameterization % 1 - from_props % 2 - min_max % 3 - validity pT_validity_TLU2 = ones(24, 20); % Pressure-temperature validity matrix T_min = {1, 'K' }; % Minimum valid temperature T_max = {inf, 'K' }; % Maximum valid temperature p_min = {1, 'MPa'}; % Minimum valid pressure p_max = {inf, 'MPa'}; % Maximum valid pressure p_atm = {0.101325, 'MPa'}; % Atmospheric pressure T_unit = {1, 'K' }; % Unit for log temperature p_unit = {1, 'Pa' }; % Unit for log pressure rho_unit = {1, 'kg/m^3' }; % Unit for log density drho_dp_unit = {1, 'kg/(m^3*Pa)'}; % Unit for log derivative of density with respect to pressure drho_dT_unit = {1, 'kg/(m^3*K)' }; % Unit for log derivative of density with respect to temperature log_ZR = 5.65948221575962; % Log of compressibility factor times specific gas constant end variables p = {0.1, 'MPa'}; % Pressure T = {300, 'K' }; % Temperature end variables (Balancing=true) mdot = {0, 'kg/s'}; % Mass flow rate Phi = {0, 'kW' }; % Energy flow rate end end ```

The domain declaration contains the following variables and parameters:

• Across variable p (absolute pressure), in MPa

• Through variable mdot (mass flow rate), in kg/s

• Across variable T (temperature), in K

• Through variable Phi (energy flow rate), in kW

• Parameter T_min, defining the minimum allowable temperature

• Parameter T_max, defining the maximum allowable temperature

• Parameter p_min, defining the minimum allowable pressure

• Parameter p_max, defining the maximum allowable pressure

• Parameter p_atm, defining the atmospheric pressure

Parameter gas_spec provides a choice of three gas models:

• `1` — Perfect (default)

• `2` — Semiperfect

• `3` — Real

In the Foundation Gas library, the Gas Properties (G) block serves as the source for domain parameter values, including the selection of the gas model. For more information on propagation of domain parameters, see Working with Domain Parameters.

The domain declaration also contains sets of parameters that define gas properties for each gas model.

Properties for semiperfect and real gas are in the form of lookup table data. These parameter declarations propagate to the components connected to the Gas domain, and therefore you can use them in the `tablelookup` function in the component equations.

To refer to this domain in your custom component declarations, use the following syntax:

`foundation.gas.gas`