ASHRAE-Standard-55 - Page 035

Extracted Content

function radians_to_degrees(radians) {

const pi = Math.PI; return radians * (180 / pi); }

function degrees_to_radians(degrees) { const pi = Math.PI; return degrees * (pi / 180); }

function get_fp(alt, sharp, posture){ /* This function calculates the projected sunlit fraction (fp) given

a seated or standing posture, a solar altitude, and a solar horizontal angle relative to the person (SHARP). fp values are taken from Thermal Comfort, Fanger 1970, Danish Technical Press.

alt : altitude of sun in degrees [0, 90] (beta) Integer sharp : sun’s horizontal angle relative to person in degrees [0, 180] Integer */

if (posture == “horizontal”) { //transpose alt and sharp for a horizontal person

const altitude_new = radians_to_degrees(

Math.asin(

Math.sin(degrees_to_radians(Math.abs(sharp - 90))) * Math.cos(degrees_to_radians(alt)) ) ); sharp = radians_to_degrees(

Math.atan(

Math.sin(degrees_to_radians(sharp)) * Math.tan(degrees_to_radians(90 - alt)) ) );

alt = altitude_new; }

var fp; var alt_range = [0, 15, 30, 45, 60, 75, 90]; var sharp_range = [0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165,

180]; var alt_i = find_span(alt_range, alt); var sharp_i = find_span(sharp_range, sharp);

if (posture 'standing'|| posture ‘horizontal’){

var fp_table = [[0.35,0.35,0.314,0.258,0.206,0.144,0.082],

[0.342,0.342,0.31,0.252,0.2,0.14,0.082],

[0.33,0.33,0.3,0.244,0.19,0.132,0.082],

[0.31,0.31,0.275,0.228,0.175,0.124,0.082],

[0.283,0.283,0.251,0.208,0.16,0.114,0.082],

[0.252,0.252,0.228,0.188,0.15,0.108,0.082],

[0.23,0.23,0.214,0.18,0.148,0.108,0.082],

[0.242,0.242,0.222,0.18,0.153,0.112,0.082],

[0.274,0.274,0.245,0.203,0.165,0.116,0.082],

[0.304,0.304,0.27,0.22,0.174,0.121,0.082],

[0.328,0.328,0.29,0.234,0.183,0.125,0.082],

[0.344,0.344,0.304,0.244,0.19,0.128,0.082],

[0.347,0.347,0.308,0.246,0.191,0.128,0.082]]; } else if (posture == ‘seated’){

var fp_table = [[0.29,0.324,0.305,0.303,0.262,0.224,0.177],

[0.292,0.328,0.294,0.288,0.268,0.227,0.177],

ANSI/ASHRAE Standard 55-2023 33