Named Excel Lambdas for Air Systems

AirModule.code-snippets

// Excel formula module with functions for air systems

/**Rectangular duct equivalent diameter (Huebscher) for static pressure loss*/
// See https://www.engineeringtoolbox.com/equivalent-diameter-d_205.html
RectDuctEqDiam = LAMBDA(WIDTH, HEIGHT, 
    1.30*(WIDTH*HEIGHT)^0.625/(WIDTH+HEIGHT)^0.25);
    
/** Equivalent rectangular duct dimension given equivalent diameter and fixed dimension (inches) -
Currently no array support*/
RectDuctEqWidth = LAMBDA(DIAM, HEIGHT,
    LET(
        FN, LAMBDA(W, RectDuctEqDiam(W,HEIGHT)),
        rootBisection(FN, DIAM, DIAM/HEIGHT, DIAM^2, 0.1)
        )
    );

/** Equivalent Square duct dimension given equivalent diameter (inches) -
Currently no array support*/
SqDuctEqWidth = LAMBDA(DIAM,
    LET(
        FN, LAMBDA(W, RectDuctEqDiam(W,W)),
        rootBisection(FN, DIAM, DIAM^0.5, DIAM^2,0.1)
        )
    );
    
/**Round Duct Diameter (in) for given airflow and SPL/100' based on simplified SPL formula*/
RoundDuctSize = LAMBDA(CFM, SPL,
    (SPL/0.109136/CFM^1.9)^(-1/5.02)
);

/**Simple formulation for approx. sp loss (inwc/100') in round duct given flow (CFM) and diameter (Inches)*/
// See https://www.engineeringtoolbox.com/duct-friction-pressure-loss-d_444.html
RoundDuctStaticLoss = LAMBDA(CFM, DIA,
    0.109136*CFM^1.9/DIA^5.02);

/**Simple formulation for CFM given sp loss (inwc/100') and Diameter in round duct (Inches)*/
// See https://www.engineeringtoolbox.com/duct-friction-pressure-loss-d_444.html
RoundDuctCFM = LAMBDA(DIA, SPL,
    (SPL*DIA^5.02/0.109136)^(1/1.9));
    
/**Avg. air speed (ft/min) in round duct given flow (CFM) and diameter (Inches)*/
RoundDuctVelocity = LAMBDA(CFM, DIA,
    LET(csa, PI() * DIA ^ 2 / 4 / 144, 
        CFM / csa)
    );

/**Round Duct Flow based on Size and Maximum Duct Velocity (fpm)*/
RoundDuctCFM_Velocity = LAMBDA(DIA, FPM,
    LET(csa, PI() * DIA ^ 2 / 4 / 144, 
        csa * FPM)
    );

/**Round Duct Size based on CFM and Maximum Duct Velocity (fpm)*/
RoundDuctSize_Velocity = LAMBDA(CFM, FPM,
    LET(csa, CFM/FPM*144, 
        (4*csa/PI())^0.5)
    );
    
/**Round Elbow Loss Coefficient (dimensionless) from Turning Radius / Diameter,
Turning Angle, and number of gores (0 = smooth)*/
RoundElbowCF = LAMBDA(RD, angle, gores,
    LET(
        angles, {20,30,45,60,75,90,110,130,150,180},
        angleFactors, {0.31, 0.45, 0.60, 0.78, 0.90, 1.00, 1.13, 1.20, 1.28, 1.40},
        radiusRatios, {0.5, 0.75, 1.0, 1.5, 2.0},
        goreCounts, {0,3,4,5},
        radiusFactors, {0.71, 0.33, 0.22, 0.15, 0.13;
                        0.98, 0.54, 0.42, 0.34, 0.33;
                        0.88, 0.50, 0.37, 0.27, 0.24;
                        0.80, 0.46, 0.33, 0.24, 0.19},

        angleFactor, INTERP1(angle,angles,angleFactors),
        radiusFactor, INTERP2(RD, gores, radiusRatios, TRANSPOSE(goreCounts), radiusFactors),
        angleFactor * radiusFactor
    )
);

/**Rounds exact size up to nearest even dimension or minimum size.  
Default min size is 6"*/
RoundDesignSize = LAMBDA(size, [MinSize],
    LET(
        ms, IF(ISOMITTED(MinSize),6,MinSize),
        _ds1, 2*CEILING.MATH(size/2),
        _ds2, IF(_ds1<ms, ms, _ds1),
        IFERROR(_ds2, "")
    )
);



/** Simple formulation for air stream velocity pressure (inWG) from velocity (ft/min)*/
VelocityPressure = LAMBDA(v,
    (v/4005)^2
);