| | 1 | #!/usr/bin/env python3 |
| | 2 | # Desc: Humidity conversion functions from EVA-2020-02-2 |
| | 3 | # Ref/Attrib: https://gitlab.com/baltakatei/ninfacyzga-01 |
| | 4 | |
| | 5 | def rel_to_abs(T,P,RH): |
| | 6 | """Returns absolute humidity given relative humidity. |
| | 7 | |
| | 8 | Inputs: |
| | 9 | -------- |
| | 10 | T : float |
| | 11 | Absolute temperature in units Kelvin (K). |
| | 12 | P : float |
| | 13 | Total pressure in units Pascals (Pa). |
| | 14 | RH : float |
| | 15 | Relative humidity in units percent (%). |
| | 16 | |
| | 17 | Output: |
| | 18 | -------- |
| | 19 | absolute_humidity : float |
| | 20 | Absolute humidity in units [kg water vapor / kg dry air]. |
| | 21 | |
| | 22 | References: |
| | 23 | -------- |
| | 24 | 1. Sonntag, D. "Advancements in the field of hygrometry". 1994. https://doi.org/10.1127/metz/3/1994/51 |
| | 25 | 2. Green, D. "Perry's Chemical Engineers' Handbook" (8th Edition). Page "12-4". McGraw-Hill Professional Publishing. 2007. |
| | 26 | |
| | 27 | Version: 0.0.1 |
| | 28 | Author: Steven Baltakatei Sandoval |
| | 29 | License: GPLv3+ |
| | 30 | """ |
| | 31 | |
| | 32 | import math; |
| | 33 | |
| | 34 | # Check input types |
| | 35 | T = float(T); |
| | 36 | P = float(P); |
| | 37 | RH = float(RH); |
| | 38 | |
| | 39 | #debug |
| | 40 | # print('DEBUG:Input Temperature (K) :' + str(T)); |
| | 41 | # print('DEBUG:Input Pressure (Pa) :' + str(P)); |
| | 42 | # print('DEBUG:Input Rel. Humidity (%) :' + str(RH)); |
| | 43 | |
| | 44 | # Set constants and initial conversions |
| | 45 | epsilon = 0.62198 # (molar mass of water vapor) / (molar mass of dry air) |
| | 46 | t = T - 273.15; # Celsius from Kelvin |
| | 47 | P_hpa = P / 100; # hectoPascals (hPa) from Pascals (Pa) |
| | 48 | |
| | 49 | # Calculate e_w(T), saturation vapor pressure of water in a pure phase, in Pascals |
| | 50 | ln_e_w = -6096*T**-1 + 21.2409642 - 2.711193*10**-2*T + 1.673952*10**-5*T**2 + 2.433502*math.log(T); # Sonntag-1994 eq 7; e_w in Pascals |
| | 51 | e_w = math.exp(ln_e_w); |
| | 52 | e_w_hpa = e_w / 100; # also save e_w in hectoPascals (hPa) |
| | 53 | # print('DEBUG:ln_e_w:' + str(ln_e_w)); # debug |
| | 54 | # print('DEBUG:e_w:' + str(e_w)); # debug |
| | 55 | |
| | 56 | # Calculate f_w(P,T), enhancement factor for water |
| | 57 | f_w = 1 + (10**-4*e_w_hpa)/(273 + t)*(((38 + 173*math.exp(-t/43))*(1 - (e_w_hpa / P_hpa))) + ((6.39 + 4.28*math.exp(-t / 107))*((P_hpa / e_w_hpa) - 1))); # Sonntag-1994 eq 22. |
| | 58 | # print('DEBUG:f_w:' + str(f_w)); # debug |
| | 59 | |
| | 60 | # Calculate e_prime_w(P,T), saturation vapor pressure of water in air-water mixture, in Pascals |
| | 61 | e_prime_w = f_w * e_w; # Sonntag-1994 eq 18 |
| | 62 | # print('DEBUG:e_prime_w:' + str(e_prime_w)); # debug |
| | 63 | |
| | 64 | # Calculate e_prime, vapor pressure of water in air, in Pascals |
| | 65 | e_prime = (RH / 100) * e_prime_w; |
| | 66 | # print('DEBUG:e_prime:' + str(e_prime)); # debug |
| | 67 | |
| | 68 | # Calculate r, the absolute humidity, in [kg water vapor / kg dry air] |
| | 69 | r = (epsilon * e_prime) / (P - e_prime); |
| | 70 | # print('DEBUG:r:' + str(r)); # debug |
| | 71 | |
| | 72 | return float(r); |
| | 73 | |
| | 74 | def rel_to_dpt(T,P,RH): |
| | 75 | """Returns dew point temperature given relative humidity. |
| | 76 | |
| | 77 | Inputs: |
| | 78 | -------- |
| | 79 | T : float |
| | 80 | Absolute temperature in units Kelvin (K). |
| | 81 | P : float |
| | 82 | Total pressure in units Pascals (Pa). |
| | 83 | RH : float |
| | 84 | Relative humidity in units percent (%). |
| | 85 | |
| | 86 | Output: |
| | 87 | -------- |
| | 88 | T_d : float |
| | 89 | Dew point temperature in units Kelvin (K). |
| | 90 | |
| | 91 | References: |
| | 92 | -------- |
| | 93 | 1. Sonntag, D. "Advancements in the field of hygrometry". 1994. https://doi.org/10.1127/metz/3/1994/51 |
| | 94 | 2. Green, D. "Perry's Chemical Engineers' Handbook" (8th Edition). Page "12-4". McGraw-Hill Professional Publishing. 2007. |
| | 95 | |
| | 96 | Version: 0.0.1 |
| | 97 | Author: Steven Baltakatei Sandoval |
| | 98 | License: GPLv3+ |
| | 99 | """ |
| | 100 | |
| | 101 | import math; |
| | 102 | |
| | 103 | # Check input types |
| | 104 | T = float(T); |
| | 105 | P = float(P); |
| | 106 | RH = float(RH); |
| | 107 | |
| | 108 | #debug |
| | 109 | # print('DEBUG:Input Temperature (K) :' + str(T)); |
| | 110 | # print('DEBUG:Input Pressure (Pa) :' + str(P)); |
| | 111 | # print('DEBUG:Input Rel. Humidity (%) :' + str(RH)); |
| | 112 | |
| | 113 | # Set constants and initial conversions |
| | 114 | epsilon = 0.62198 # (molar mass of water vapor) / (molar mass of dry air) |
| | 115 | t = T - 273.15; # Celsius from Kelvin |
| | 116 | P_hpa = P / 100; # hectoPascals (hPa) from Pascals (Pa) |
| | 117 | |
| | 118 | # Calculate e_w(T), saturation vapor pressure of water in a pure phase, in Pascals |
| | 119 | ln_e_w = -6096*T**-1 + 21.2409642 - 2.711193*10**-2*T + 1.673952*10**-5*T**2 + 2.433502*math.log(T); # Sonntag-1994 eq 7; e_w in Pascals |
| | 120 | e_w = math.exp(ln_e_w); |
| | 121 | e_w_hpa = e_w / 100; # also save e_w in hectoPascals (hPa) |
| | 122 | # print('DEBUG:ln_e_w:' + str(ln_e_w)); # debug |
| | 123 | # print('DEBUG:e_w:' + str(e_w)); # debug |
| | 124 | |
| | 125 | # Calculate f_w(P,T), enhancement factor for water |
| | 126 | f_w = 1 + (10**-4*e_w_hpa)/(273 + t)*(((38 + 173*math.exp(-t/43))*(1 - (e_w_hpa / P_hpa))) + ((6.39 + 4.28*math.exp(-t / 107))*((P_hpa / e_w_hpa) - 1))); # Sonntag-1994 eq 22. |
| | 127 | # print('DEBUG:f_w:' + str(f_w)); # debug |
| | 128 | |
| | 129 | # Calculate e_prime_w(P,T), saturation vapor pressure of water in air-water mixture, in Pascals |
| | 130 | e_prime_w = f_w * e_w; # Sonntag-1994 eq 18 |
| | 131 | # print('DEBUG:e_prime_w:' + str(e_prime_w)); # debug |
| | 132 | |
| | 133 | # Calculate e_prime, vapor pressure of water in air, in Pascals |
| | 134 | e_prime = (RH / 100) * e_prime_w; |
| | 135 | # print('DEBUG:e_prime:' + str(e_prime)); # debug |
| | 136 | |
| | 137 | n = 0; repeat_flag = True; |
| | 138 | while repeat_flag == True: |
| | 139 | # print('DEBUG:n:' + str(n)); # debug |
| | 140 | |
| | 141 | # Calculate f_w_td, the enhancement factor for water at dew point temperature. |
| | 142 | if n == 0: |
| | 143 | f = 1.0016 + 3.15*10**-6*P_hpa - (0.074 / P_hpa); # Sonntag-1994 eq 24 |
| | 144 | f_w_td = f; # initial approximation |
| | 145 | elif n > 0: |
| | 146 | t_d_prev = float(t_d); # save previous t_d value for later comparison |
| | 147 | f_w_td = 1 + (10**-4*e_w_hpa)/(273 + t_d)*(((38 + 173*math.exp(-t_d/43))*(1 - (e_w_hpa / P_hpa))) + ((6.39 + 4.28*math.exp(-t_d / 107))*((P_hpa / e_w_hpa) - 1))); # Sonntag-1994 eq 22. |
| | 148 | # print('DEBUG:f_w_td:' + str(f_w_td)); # debug |
| | 149 | |
| | 150 | # Calculate e, the vapor pressure of water in the pure phase, in Pascals |
| | 151 | e = (e_prime / f_w_td); # Sonntag-1994 eq 9 and 20 |
| | 152 | # print('DEBUG:e:' + str(e)); # debug |
| | 153 | |
| | 154 | # Calculate y, an intermediate dew point calculation variable |
| | 155 | y = math.log(e / 611.213); |
| | 156 | # print('DEBUG:y:' + str(y)); # debug |
| | 157 | |
| | 158 | # Calculate t_d, the dew point temperature in degrees Celsius |
| | 159 | t_d = 13.715*y + 8.4262*10**-1*y**2 + 1.9048*10**-2*y**3 + 7.8158*10**-3*y**4;# Sonntag-1994 eq 10 |
| | 160 | # print('DEBUG:t_d:' + str(t_d)); # debug |
| | 161 | |
| | 162 | if n == 0: |
| | 163 | # First run |
| | 164 | repeat_flag = True; |
| | 165 | else: |
| | 166 | # Test t_d accuracy |
| | 167 | t_d_diff = math.fabs(t_d - t_d_prev); |
| | 168 | # print('DEBUG:t_d :' + str(t_d)); # debug |
| | 169 | # print('DEBUG:t_d_prev:' + str(t_d_prev)); # debug |
| | 170 | # print('DEBUG:t_d_diff:' + str(t_d_diff)); # debug |
| | 171 | if t_d_diff < 0.01: |
| | 172 | repeat_flag = False; |
| | 173 | else: |
| | 174 | repeat_flag = True; |
| | 175 | |
| | 176 | # Calculate T_d, the dew point temperature in Kelvin |
| | 177 | T_d = 273.15 + t_d; |
| | 178 | # print('DEBUG:T_d:' + str(T_d)); # debug |
| | 179 | |
| | 180 | if n > 100: |
| | 181 | return T_d; # good enough |
| | 182 | |
| | 183 | # update loop counter |
| | 184 | n += 1; |
| | 185 | return T_d; |
projects / BK-2020-03.git / blame_incremental