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Moist Air Properties (MA)

Global moist air properties for attached circuit

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  • Moist Air Properties (MA) block

Libraries:
Simscape / Foundation Library / Moist Air / Utilities

Description

The Moist Air Properties (MA) block defines the moist air properties that act as global parameters for all the blocks connected to a circuit. The moist air mixture is composed of dry air, water vapor, and an optional trace gas. The default trace gas is carbon dioxide.

Dry air, water vapor, and trace gas are assumed to be semiperfect gas. Pressure, temperature, and density obey the ideal gas law. Other properties are functions of temperature. You specify them as one-dimensional arrays corresponding to the Temperature vector.

Each topologically distinct moist air circuit in a diagram can have a Moist Air Properties (MA) block connected to it. If no Moist Air Properties (MA) block is attached to a circuit, the blocks in this circuit use the properties corresponding to the default Moist Air Properties (MA) block parameter values.

Examples

Vehicle HVAC System

Vehicle HVAC System

Models moist air flow in a vehicle heating, ventilation, and air conditioning (HVAC) system. The vehicle cabin is represented as a volume of moist air exchanging heat with the external environment. The moist air flows through a recirculation flap, a blower, an evaporator, a blend door, and a heater before returning to the cabin. The recirculation flap selects flow intake from the cabin or from the external environment. The blender door diverts flow around the heater to control the temperature.

Open Model
Aircraft Environmental Control System

Aircraft Environmental Control System

Models an aircraft environmental control system (ECS) that regulates pressure, temperature, humidity, and ozone (O3) to maintain a comfortable and safe cabin environment. Cooling and dehumidification are provided by the air cycle machine (ACM), which operates as an inverse Brayton cycle to remove heat from pressurized hot engine bleed air. Some hot bleed air is mixed directly with the output of the ACM to adjust the temperature. Pressurization is maintained by the outflow valve in the cabin. This model simulates the ECS operating from a hot ground condition to a cold cruise condition and back to a cold ground condition.

Open Model
Medical Ventilator with Lung Model

Medical Ventilator with Lung Model

Models a positive-pressure medical ventilator system. A preset flow rate is supplied to the patient. The lungs are modeled with the Translational Mechanical Converter (MA), which converts moist air pressure into translational motion. By setting the Interface cross-sectional area to unity, displacement in the mechanical translational network becomes a proxy for volume, force becomes a proxy for pressure, spring constant becomes a proxy for respiratory elastance, and damping coefficient becomes a proxy for respiratory resistance.

Open Model
Pneumatic Actuator with Humidity

Pneumatic Actuator with Humidity

How the Simscape™ Foundation Library moist air components can be used to model a pneumatic actuator operating in a humid environment. The Directional Valve is a subsystem composed of four Variable Local Restriction (MA) blocks, and the Double-Acting Actuator is a subsystem composed of two Translational Mechanical Converter (MA) blocks in opposite mechanical orientation.

Open Model

Ports

Conserving

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Conserving port that connects the block to the moist air network. You can connect it to any point on a moist air connection line in a block diagram. When you connect the Moist Air Properties (MA) block to a connection line, the software automatically identifies the moist air blocks connected to the particular circuit and propagates the properties to all these blocks.

Parameters

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Dry Air

Universal gas constant divided by molar mass of dry air.

Vector of temperature values, to be used for table lookup of other properties as a function of temperature. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [-56.55, -50 : 10 : -10, -5 : 1 : 5, 10 : 10 : 350]' degC.

The vector of specific enthalpy values of dry air, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size.

The default value is [342.416126230579; 349.005511058471; 359.063577249119; 369.119948684177; 379.175469465129; 389.230944678417; 394.258910928084; 395.264534937366; 396.27017101329; 397.275819932805; 398.281482472874; 399.287159410541; 400.292851523015; 401.298559587728; 402.304284382408; 403.310026685143; 404.315787274435; 409.34489180313; 419.404921755863; 429.468036401264; 439.535033154839; 449.606720928652; 459.683919949603; 469.767460521911; 479.858181001348; 489.956925196484; 500.064539372946; 510.181869006204; 520.309755403634; 530.449032296018; 540.60052248087; 550.765034584465; 560.943359995745; 571.136270013102; 581.344513234296; 591.568813210327; 601.809866375885; 612.068340261954; 622.344871990218; 632.640067043998; 642.95449830646; 653.288705353699; 663.643193987949; 674.018435994423; 684.414869104228; 694.832897145098; 705.272890361557; 715.735185886199; 726.220088344236; 736.727870574087; 747.258774447567; 757.813011774199] kJ/kg.

The vector of dynamic viscosity values of dry air, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size.

The default value is [14.2568883320012; 14.6140127728333; 15.1517277055779; 15.6806860159119; 16.2012351072083; 16.7137043125028; 16.9670071730589; 17.017438062815; 17.0677930842452; 17.1180725309876; 17.1682766951315; 17.2184058672268; 17.2684603362935; 17.3184403898301; 17.3683463138234; 17.4181783927569; 17.4679369096204; 17.7156358640698; 18.2056751785154; 18.68879035749; 19.1652344664982; 19.6352478927873; 20.099059103658; 20.5568853601578; 21.0089333871663; 21.4554000014051; 21.8964726992323; 22.3323302062775; 22.7631429910631; 23.1890737447833; 23.6102778293792; 24.0269036959922; 24.4390932757886; 24.8469823450548; 25.2507008663546; 25.6503733074314; 26.0461189394339; 26.4380521159325; 26.8262825340948; 27.2109154792923; 27.5920520543128; 27.969789394274; 28.3442208682439; 28.7154362685068; 29.0835219883356; 29.4485611890712; 29.8106339572472; 30.1698174524429; 30.5261860464955; 30.8798114546565; 31.2307628592324; 31.5791070262086] s*μPa.

The vector of thermal conductivity values of dry air, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size.

The default value is [19.8808489374933; 20.4162454629695; 21.2248743590758; 22.0232452890903; 22.8117314495857; 23.5906913619588; 23.9767075412237; 24.053639990175; 24.1304826682191; 24.2072359051629; 24.2839000294007; 24.3604753679152; 24.4369622462801; 24.5133609886625; 24.5896719178249; 24.6658953551279; 24.7420316205333; 25.1214164701832; 25.8738283029331; 26.6180150229276; 27.3542674377332; 28.0828634735341; 28.8040686837224; 29.5181367785657; 30.2253101618423; 30.9258204644224; 31.6198890677835; 32.3077276126633; 32.9895384896798; 33.6655153099498; 34.33584335461; 35.0007000027879; 35.6602551380254; 36.3146715334901; 36.9641052165342; 37.6087058133173; 38.248616874307; 38.8839761815308; 39.5149160384798; 40.1415635435708; 40.7640408480637; 41.3824653993118; 41.9969501701893; 42.6076038755117; 43.2145311762238; 43.8178328720941; 44.4176060836121; 45.013944423749; 45.6069381602018; 46.1966743687041; 46.783237077953; 47.3667074066625] mW/m/K.

Lowest pressure allowed in the moist air network. The simulation issues an error when pressure is out of range.

Highest pressure allowed in the moist air network. The simulation issues an error when pressure is out of range.

Lowest temperature allowed in the moist air network. The simulation issues an error when temperature is out of range.

Highest temperature allowed in the moist air network. The simulation issues an error when temperature is out of range.

Select what happens if the moist air pressure or temperature go beyond the valid range during simulation:

  • None ― The block does not return an error if the properties go out of range.

  • Warning ― The block issues a warning, but continues the simulation.

  • Error ― The block returns an error and stops the simulation.

Absolute pressure of the environment.

Absolute temperature of the environment.

Water Vapor

Universal gas constant divided by molar mass of water vapor.

Vector of vapor saturation values for water as a function of temperature, to be used for one-dimensional table lookup. Moist air becomes saturated when the partial pressure of water vapor is equal to the water vapor saturation pressure. Therefore, condensation may occur. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [1.71168953425982e-06; 3.93770601979424e-06; 1.28411717710344e-05; 3.80051394873809e-05; .00010323902900209; .000259873810798063; .000401741022116384; .000437454836117844; .000476040820618202; .000517704666185737; .000562664883741207; .000611212677444345; .000657088049117899; .000705987905898279; .000758082381149132; .000813549384183233; .000872574861129522; .00122818386934022; .0023392147667769; .00424668834054807; .00738442748706953; .0123512704340234; .0199458019246787; .0312006356960619; .0474147199263783; .0701823607447713; .10141797792131; .143375967241115; .198665399739302; .270259606559999; .361500961984849; .476101381081492; .618139196722055; .792053183687694; 1.0026345688121; 1.25501792086105; 1.55467186826983; 1.90739066433297; 2.31928772772542; 2.79679245576864; 3.34665187151016; 3.97593907083533; 4.69207105435535; 5.5028394740883; 6.41645928168037; 7.4416425436169; 8.58770832955728; 9.86474556030261; 11.2838558865497; 12.8575218898034; 14.6001810568052; 16.5291642526045] MPa.

Vector of the difference between the specific enthalpy of saturated water vapor and the specific enthalpy of saturated liquid water as a function of temperature, to be used for one-dimensional table lookup. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [2836.88241275372; 2837.81392500514; 2838.63937175807; 2838.7309929628; 2838.06905313927; 2836.62597341095; 2835.60023952573; 2835.37006381376; 2835.13143158077; 2834.88429145066; 2834.62859062897; 2500.93420564316; 2498.55329907119; 2496.17495082036; 2493.79885912205; 2491.42474723191; 2489.05236104642; 2477.20875029194; 2453.54955988604; 2429.83856603313; 2406.00136954922; 2381.97406342174; 2357.69101156389; 2333.08088387814; 2308.06565480412; 2282.56034405021; 2256.47287422313; 2229.70428017508; 2202.14968030993; 2173.69998896199; 2144.24368406447; 2113.66758247452; 2081.85585110571; 2048.68725710494; 2014.03141249899; 1977.7449923284; 1939.66849592886; 1899.62342931686; 1857.40930169838; 1812.79975416601; 1765.53721731251; 1715.32525772152; 1661.81700477787; 1604.59703745016; 1543.1534616334; 1476.83692476464; 1404.80240352424; 1325.92091736114; 1238.61667822208; 1140.5102987018; 1027.62017777647; 892.733785613825] kJ/kg.

The vector of specific enthalpy values of water vapor, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [2396.55944251649; 2408.68643343608; 2427.1988031141; 2445.702165897; 2464.18429108356; 2482.62529466839; 2491.82135326629; 2493.6580151792; 2495.49372578218; 2497.32843835745; 2499.16210446923; 2500.99462758899; 2502.83092214066; 2504.6665223621; 2506.50140563013; 2508.335548891; 2510.16892865793; 2519.32352241995; 2537.56068088674; 2555.67742615292; 2573.6403223998; 2591.4109179101; 2608.9455037701; 2626.19492016262; 2643.10444358428; 2659.61377634497; 2675.58278696023; 2696.1846256545; 2716.49989553741; 2736.6235210957; 2756.61216047011; 2776.50561773853; 2796.33378922508; 2816.11979583049; 2835.88181423877; 2855.63430574511; 2875.38889327595; 2895.15500577172; 2914.94035964689; 2934.75132290228; 2954.59319330244; 2974.47041285505; 2994.38673458964; 3014.34535328009; 3034.34900867103; 3054.40006755764; 3074.50058946898; 3094.65237953784; 3114.85703128106; 3135.11596137801; 3155.43043805905; 3175.80160435813] kJ/kg.

The vector of dynamic viscosity values of water vapor, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [6.81365662228272; 7.04953750742707; 7.40970098298307; 7.76991278093907; 8.13017290129507; 8.49048134405107; 8.67065368632907; 8.70668960445667; 8.74272600580827; 8.77876289038387; 8.81480025818347; 8.85083810920707; 8.88687644345467; 8.92291526092627; 8.95895456162187; 8.99499434554147; 9.03103461268507; 9.21124319676307; 9.57169660671907; 9.93219833907507; 10.2927483938311; 10.6533467709871; 11.0139934705431; 11.3746884924991; 11.7354318368551; 12.0962235036111; 12.4570634927671; 12.8179518043231; 13.1788884382791; 13.5398733946351; 13.9009066733911; 14.2619882745471; 14.6231181981031; 14.9842964440591; 15.3455230124151; 15.7067979031711; 16.0681211163271; 16.4294926518831; 16.7909125098391; 17.1523806901951; 17.5138971929511; 17.8754620181071; 18.2370751656631; 18.5987366356191; 18.9604464279751; 19.3222045427311; 19.6840109798871; 20.0458657394431; 20.4077688213991; 20.7697202257551; 21.1317199525111; 21.4937680016671] s*μPa.

The vector of thermal conductivity values of water vapor, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [11.46288215976; 11.941997488935; 12.676358586935; 13.414208884935; 14.155548382935; 14.900377080935; 15.274099879935; 15.348949115735; 15.423833243535; 15.498752263335; 15.573706175135; 15.648694978935; 15.723718674735; 15.798777262535; 15.873870742335; 15.948999114135; 16.024162377935; 16.400502076935; 17.155798374935; 17.914583872935; 18.676858570935; 19.442622468935; 20.211875566935; 20.984617864935; 21.760849362935; 22.540570060935; 23.323779958935; 24.110479056935; 24.900667354935; 25.694344852935; 26.491511550935; 27.292167448935; 28.096312546935; 28.903946844935; 29.715070342935; 30.529683040935; 31.347784938935; 32.169376036935; 32.994456334935; 33.823025832935; 34.655084530935; 35.490632428935; 36.329669526935; 37.172195824935; 38.018211322935; 38.867716020935; 39.720709918935; 40.577193016935; 41.437165314935; 42.300626812935; 43.167577510935; 44.038017408935] mW/m/K.

Coefficient for the diffusive flux of water vapor in the moist air mixture due to the difference in concentration of water vapor. During mixture flow reversal, the water vapor mass flow rate at the ports smoothly transitions between the upstream and downstream value based on the diffusivity.

Trace Gas

Select how the block models the amount of trace gas in the air mixture:

  • None — No trace gas is present. The moist air mixture consists of only dry air and water vapor. Any nonzero values of trace gas level in parameters and variable targets of the blocks connected to the circuit are ignored. All connections to the trace gas source blocks in the model are also ignored. Therefore, you do not need to modify your model based on the trace gas modeling selection.

  • Track mass fraction only — The trace gas level can be nonzero and vary during simulation. However, the amount of trace gas is assumed to be small enough to have a negligible impact on the fluid properties of the moist air mixture.

  • Track mass fraction and gas properties — The trace gas level can be nonzero and vary during simulation. The fluid properties of the moist air mixture depend on the amount of trace gas in the mixture.

For more information on the impact of these options on block and system equations, see Trace Gas Modeling Options.

Universal gas constant divided by molar mass of trace gas.

Dependencies

Enabled when the Trace gas model parameter is set to Track mass fraction only or Track mass fraction and gas properties.

The vector of specific enthalpy values of trace gas, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [439.555216260064; 444.670268200251; 452.538618847003; 460.487124258496; 468.522588768941; 476.649415958793; 480.74798538725; 481.57054318762; 482.394052398751; 483.218514288831; 484.043930029015; 484.870300696555; 485.697627277859; 486.525910671489; 487.355151691079; 488.185351068185; 489.016509455051; 493.186704139431; 501.599194953048; 510.107689961685; 518.711611080182; 527.410026793075; 536.201764778798; 545.085474203452; 554.059675505208; 563.122805485367; 572.27325096919; 581.509373027928; 590.829525105886; 600.232066705818; 609.715373581392; 619.277845178105; 628.917909922924; 638.634028838794; 648.424697859328; 658.288449140109; 668.223851601449; 678.229510889093; 688.304068901113; 698.44620299875; 708.654624994591; 718.928079991818; 729.265345132425; 739.665228299475; 750.126566808087; 760.648226111439; 771.229098541268; 781.868102096908; 792.564179292476; 803.316296068366; 814.123440770426; 824.984623198037] kJ/kg.

Dependencies

Enabled when the Trace gas model parameter is set to Track mass fraction and gas properties.

The vector of dynamic viscosity values of trace gas, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [10.8921054191698; 11.2215357085649; 11.7233300740382; 12.2234238147811; 12.7215124453467; 13.2173328890673; 13.4643203184773; 13.5136406274989; 13.562934752385; 13.6122025024997; 13.6614436900741; 13.7106581301692; 13.7598456406398; 13.8090060420983; 13.8581391578796; 13.9072448140062; 13.9563228391538; 14.2012926853717; 14.6890687376044; 15.1738428124161; 15.6554929043332; 16.1339159800463; 16.6090257998657; 17.0807510097148; 17.5490334645512; 18.0138267508952; 18.4750948814453; 18.9328111390399; 19.3869570507278; 19.8375214755778; 20.2844997922255; 20.7278931741254; 21.1677079421287; 21.6039549853963; 22.036649242835; 22.4658092382469; 22.8914566632375; 23.3136160026627; 23.7323141980278; 24.1475803447965; 24.5594454200432; 24.9679420372927; 25.3731042257492; 25.774967231431; 26.1735673380029; 26.5689417053362; 26.9611282240413; 27.350165384404; 27.73609215832; 28.118947892972; 28.4987722151178; 28.8756049449796] s*μPa.

Dependencies

Enabled when the Trace gas model parameter is set to Track mass fraction and gas properties.

The vector of thermal conductivity values of trace gas, to be used for one-dimensional table lookup based on the corresponding temperature value. The vector size must be the same as the temperature vector size. Dry air, water vapor, and trace gas properties share the same temperature vector.

The default value is [10.489430678843; 10.9507672150864; 11.666197960308; 12.392559739764; 13.1299519771612; 13.8778409888416; 14.2554325416312; 14.3312274189707; 14.4071122346908; 14.4830860227061; 14.5591478179508; 14.6352966574703; 14.7115315815553; 14.787851634907; 14.8642558678259; 14.9407433374142; 15.0173131087819; 15.401364480906; 16.1751373988038; 16.9558134611595; 17.7432208682398; 18.5366976599676; 19.3360988502003; 20.1412225692689; 20.9517507672929; 21.7672310558863; 22.5871115634685; 23.4107980865695; 24.2377021890869; 25.0672663781241; 25.8989689893876; 26.732318357514; 27.5668446164644; 28.4020933015927; 29.2376215872816; 30.0729965057542; 30.9077942826816; 31.7416001931033; 32.5740086297993; 33.4046232539953; 34.2330571812868; 35.0589331874899; 35.8818839295189; 36.701552179391; 37.5175910702657; 38.3296643536716; 39.1374466671854; 39.9406238119064; 40.7388930391313; 41.5319633456945; 42.3195557774861; 43.1014037407076] mW/m/K.

Dependencies

Enabled when the Trace gas model parameter is set to Track mass fraction and gas properties.

Coefficient for the diffusive flux of trace gas in the moist air mixture due to the difference in concentration of trace gas. During mixture flow reversal, the trace gas mass flow rate at the ports smoothly transitions between the upstream and downstream value based on the diffusivity.

Dependencies

Enabled when the Trace gas model parameter is set to Track mass fraction only or Track mass fraction and gas properties.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a

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See Also

Topics