# Variables
t_db = 293.; #K
W = 0.0095; #kg/kg of dry air
p_t = 1.0132;
# Calculations and Results
print ("(i) Partial pressure of vapour")
p_v = p_t*W/(W+0.622);
print ("p_v = %.3f")% (p_v), ("bar")
p_vs = 0.0234; #bar; From steam tables corresponding to 20 0C
phi = p_v/p_vs;
print ("(ii)relative hmidity = %.3f")% (phi)
print ("(iii) Dew point temperature")
t_dp = 13 + (14-13)/(0.01598 - 0.0150)*(0.01524-0.0150); #From stea table by interpolation
print ("t_dp = %.3f")% (t_dp), ("0C")
# Variables
t_db = 290.; #K
phi = 0.6; #relative humidity
p_t = 1.01325; #bar
p_vs = 0.0194; #bar
# Calculations
p_v = phi*p_vs;
W = 0.622*p_v/(p_t - p_v);
t_dp = 9 + (10-9)*(0.01164-0.01150)/(0.01230 - 0.01150); #By interpolation from steam tables
# Results
print ("Specific Humidity = %.4f")% (W), ("kg/kg of dry air")
print ("dew point temperature = "), (t_dp), ("0C")
# Variables
phi = 0.55;
p_vs = 0.0425; #bar
p_t = 1.0132; #bar
# Calculations
p_v = phi*p_vs;
W = 0.622*p_v/(p_t-p_v);
#Specific humidity after removing o.oo4 kg of water vapour
Wnew = W-0.004;
p_v = p_t*Wnew/(Wnew+0.622);
p_vs = 0.0234; #bar
# Results
print ("(i) Relative humidity"),
phi = p_v/p_vs;
print ("phi = %.3f")%(phi)
print ("(ii) Dew point temperature")
print ("Corresponding to 0.0171 bar, from steam tables")
t_dp = 15.; #0C
print ("t_dp = %.3f")% (t_dp), ("0C")
# Variables
t_db = 35.; #0C
t_wb = 25.; #0C
p_t = 1.0132; #bar
#Corresponding to 25 0C in steam tables
p_vs_wb = 0.0317; #bar
# Calculations
p_v = p_vs_wb - (p_t - p_vs_wb)*(t_db - t_wb)/(1527.4 - 1.3*t_wb);
print ("(i) Specific humidity")
W = 0.622*p_v/(p_t-p_v);
print ("W = %.3f")% (W), ("kg/kg of dry air")
print ("(ii) Relative humidity")
#Corresponding to 35 0C, from steam tables
p_vs = 0.0563;
phi = p_v/p_vs;
print ("phi %.3f")% (phi)
print ("(iii) Vapour density")
R_v = 8314.3/18;
T_v = 308.; #K
rho_v = p_v*10**5/(R_v*T_v);
print ("rho_v = %.3f")% (rho_v),("kg/m**3")
print ("(iv) Dew point temperature")
t_dp = 21 + (22-21)*(0.0252-0.0249)/(0.0264-0.0249);
print ("t_dp %.3f")%(t_dp), ("0C")
print ("(v) Enthalpy of mixture per kg of dry air")
cp = 1.005;
h_g = 2565.3; #kJ/kg; corresponding to 35 0C
h_vapour = h_g + 1.88*(t_db - t_dp);
h = cp*t_db + W*h_vapour;
print ("h = %.3f")% (h), ("kJ/kg of dry air")
#For the air at 35 0C DBT and 60% R.H.
p_vs = 0.0563; #bar; Corresponding to 35 0C from stem tables
phi = 0.6;
p_t = 1.0132; #bar
cp = 1.005;
t_db = 35.; #0C
h_g = 2565.5; #kJ/kg
m1 = 1.; #kg
m2 = 2.; #kg
m = m1+m2;
# Calculations
p_v = phi*p_vs;
W1 = 0.622*p_v/(p_t-p_v);
#Corresponding to 0.0388 bar, from steam tables
t_dp = 26.+(27.-26)*(0.0338-0.0336)/(0.0356-0.0336);
h_vapour = h_g + 1.88*(t_db - t_dp);
h1 = cp*t_db+W1*h_vapour;
#For the air at 20°C DBT and 13°C dew point temperature :
p_v = 0.0150; #bar
W2 = 0.622*p_v/(p_t-p_v);
t_db = 20.; #0C
t_dp = 13.;
h_g = 2538.1; #kJ/kg
h_vapour = h_g + 1.88*(t_db - t_dp);
h2 = cp*t_db+W2*h_vapour;
#let enthalpy per kg of moist air be h
h = ((m1*h1/(1+W1)) + (m2*h2/(1+W2)))/m;
#Let Mass of vapour/kg of moist air be M
M = (m1*W1/(1+W1) + m2*W2/(1+W2))/m;
#Let specific humidity be denoted by SH
SH = M/(1-M);
# Results
print ("Specific humidity = %.3f")% (SH), ("kg/kg of dry air")
# Variables
#For air at 20 0C and 75% R.H
p_vs = 0.0234; #bar
phi = 0.75;
p_t = 1.0132;
cp = 1.005;
t_db = 20.; #0C
# Calculations
p_v = phi*p_vs;
t_dp = 15 + (16-15)*(0.01755-0.017)/(0.0182-0.017);
W = 0.622*p_v/(p_t-p_v);
h_g = 2538.1 #kJ/kg
h_vapour = h_g + 1.88*(t_db - t_dp);
h1 = cp*t_db + W*h_vapour;
# Calculations and Results
print ("(i) Relative humidity of heated air :")
#For air at 30°C DBT
p_vs = 0.0425; #bar; corresponding to 30 0C
phi = p_v/p_vs;
print ("Relative humidity = %.3f")% (phi*100), ("%")
print ("(ii) Heat added to air per minute")
h_g = 2556.3; #kJkg
t_db = 30.;
h2 = cp*t_db+W*h_vapour;
V = 90.; #m**3
R = 287.;
T = 293.; #K
m = (p_t-p_v)*V*10**5/R/T;
Amt = m*(h2-h1);
print ("Amount of heat added per minute = %.3f")% (Amt),("kJ")
#For air at 35 0C DBT and 50% RH
p_vs = 0.0563; #bar; At 35 0C, from steam tables
phi = 0.5;
p_t = 1.0132;
t_db1 = 35.; #0C
t_dp1 = 23.; #0C
cp = 1.005;
R = 287.;
# Calculations
p_v = phi*p_vs;
W1 = 0.622*p_v/(p_t-p_v);
h_g1 = 2565.3; #kJ/kg
h_vapour = h_g1 + 1.88*(t_db1 - t_dp1);
h1 = cp*t_db1+W1*h_vapour;
# Results
print ("(i) R.H. of cooled air")
p_vs = 0.0317;
phi = p_v/p_vs;
print ("RH of cooled air = %.3f")% (phi*100), ("%")
print ("(ii) Heat removed from air")
h_g2 = 2547.2; #kJ/kg
t_db2 = 25.; #0C
t_dp2 = 23.; #0C
W2 = W1;
T = 308.; #K
V = 40.; #m**3
h_vapour = h_g2 + 1.88*(t_db2 - t_dp2);
h2 = cp*t_db2+W2*h_vapour;
m = (p_t-p_v)*10**5*V/R/T;
#Let Heat removed be denoted by H
H = m*(h1-h2);
print ("Heat removed = %.3f")% (H), ("kJ")
#For the air at 35°C DBT and 50% R.H.
# Variables
p_vs = 0.0563; #bar; At 35 0C, from steam tables
phi = 0.5;
p_v = phi*p_vs;
p_t = 1.0132; #bar
t_dp1 = 23.; #0C
t_db1 = 35.; #0C
W1 = 0.622*p_v/(p_t-p_v);
h_g1 = 2565.3; #kJ/kg
R = 287.;
cp = 1.005;
# Calculations and Results
h_vapour = h_g1 + 1.88*(t_db1 - t_dp1);
h1 = cp*t_db1+W1*h_vapour;
print ("(i) Relative humidity of out coming air and its wet bulb temperature.")
print ("Relative humidity of exit air is 100 per cent.")
t_wb = 20; #0C
print ("Wet bulb temperture = %.3f")%(t_wb), ("0C")
p_v = 0.0234; #bar
p_vs = p_v;
t_db2 = 20; #0C
h_g2 = 2538.1; #kJ/kg
t_dp2 = t_db2;
W2 = 0.622*p_v/(p_t-p_v);
h_vapour = h_g2 + 1.88*(t_db2 - t_dp2);
h2 = cp*t_db2+W2*h_vapour;
T = 308.; #K
V = 120.; #m**3
W = W1-W2; #Weight of water vvapour removed per kg of dry air
h = h1-h2; #Heat removed per kg of dry air
m = (p_t-p_v)*10**5*V/R/T;
print ("(ii) Capacity of the cooling coil in tonnes of refrigeration")
C = m*(h1-h2)*60/14000;
print ("Capacity = %.3f")% (C), ("TR")
Amt = m*(W1-W2)*60;
print ("(iii)Amount of water removed per hour = %.3f")% (Amt), ("kg/h")
# Variables
p_vs = 0.0563; #bar
phi = 0.2;
p_v = phi*p_vs;
p_t = 1.0132; #bar
# Calculations and Results
W1 = 0.622*p_v/(p_t-p_v);
print ("(i) Dew point temperature")
#
t_dp = 8+(9.-8)*(0.01126-0.01072)/(0.01150-0.01072);
print ("dew point temperature = %.3f")% (t_dp), ("0C")
print ("(ii) Relative humidity of the exit air :")
p_vs_wb = 0.0170; #bar
p_vs = 0.0234; #bar
t_db = 20.; #0C
t_wb = 15.; #0C
p_v = p_vs_wb - (p_t-p_vs_wb)*(t_db-t_wb)/(1527.4-1.3*t_wb);
W2 = 0.622*p_v/(p_t-p_v);
RH = p_v/p_vs;
print ("Relative humidity = %.3f")% (RH)
p_v = 0.01126; #bar
R = 287.;
T = 308.; #K
V = 150.;
m = (p_t-p_v)*V*10**5/R/T;
print ("(iii) Amount of water vapour added to the air per minute")
amt = m*(W2-W1);
print ("Amount = %.3f")% (amt), ("kg/min")
# Variables
p_s = 0.0206; #bar
p_t = 1; #bar
p_s1 = 0.03782; #bar
W_2s = 0.622*p_s/(p_t-p_s);
cp = 1.005;
t_db2 = 18; #0C
t_db1 = 28; #0C
h_g2 = 2534.4; #kJ/kg
h_f2 = 75.6; #kJ/kg
h_g1 = 2552.6; #kJ/kg
# Calculations
W1 = (cp*(t_db1-t_db2) + W_2s*(h_g2-h_f2))/(h_g1-h_f2);
p_v1 = W1*p_t/(0.622+W1);
RH = p_v1/p_s1; #Relative humidity
# Results
print ("Relative humidity %.3f")% (RH)
# Variables
t_db1 = 38.; #0C
t_db2 = 18.; #0C
phi_1 = 0.75;
phi_2 = 0.85;
p_t = 1.; #bar
cp = 1.005;
#At 38 0C
p_vs = 0.0663; #bar
h_g1 = 2570.7; #kJ/kg
# Calculations
p_v = phi_1*p_vs;
W1 = 0.622*p_v/(p_t-p_v);
#At 18 0C
p_vs = 0.0206; #bar
h_g2 = 2534.4; #kJ/kg
h_f2 = 75.6; #kJ/kg
p_v = phi_2*p_vs;
W2 = 0.622*p_v/(p_t-p_v);
q = (W2*h_g2 - W1*h_g1) + cp*(t_db2-t_db1) + (W1-W2)*h_f2;
# Results
print ("Heat transfer rate = %.3f")% (q), ("kJ/kg of dry air")
# Variables
#At 38 0C
p_vs = 0.0663; #bar
h_g1 = 2570.7; #kJ/kg
phi = 0.25;
p_t = 1.0132;
p_v = phi*p_vs;
cp = 1.005;
#At 18 0C
h_g2 = 2534.4; #kJ/kg
p_vs = 0.0206; #bar
W1 = 0.622*p_v/(p_t-p_v);
t_db1 = 38.; #0C
t_db2 = 18.; #0C
# Results
W2 = (cp*(t_db1-t_db2) + W1*h_g1)/h_g2;
#amount of water added = amt
amt = W2-W1;
# Results
print ("amt = %.5f")% (amt), ("kg/kg of dry air")
p_v2 = amt*p_t/(0.622+amt);
RH = p_v2/p_vs;
print ("Final relative humidity %.3f")% (RH)
import math
# Variables
#At 22 0c
p_vs = 0.0264; #bar
phi_3 = 0.55;
p_t = 1.0132; #bar
p_v3 = phi_3*p_vs;
W3 = 0.622*p_v3/(p_t-p_v3);
#At 3 0C
p_vs1 = 0.0076; #bar
p_v1 = p_vs1;
# Calculations and Results
W1 = 0.622*p_v1/(p_t-p_v1);
R = 287.;
T_3 = 295.; #K
v = R*T_3/(p_t-p_v3)/10**5;
m = (W3-W1)/v;
print ("(i)Mass of spray water required = %.6f")% (m), ("kg moisture/m**3")
t_dp = 12.5; #0C
cp = 1.005;
t_db3 = 22.; #0C
h_g3 = 2524.; #kJ/kg
h_vapour3 = h_g3 + 1.88*(t_db3 - t_dp);
W2 = 0.0047;
h_g2 = 2524; #kJ/kg
h4 = 41.87;
t_db2 = (cp*t_db3 + W3*h_vapour3 -W2*h_g2 + 1.88*W2*t_dp - (W3-W2)*h4)/(cp-W2*1.88);
print ("(ii) Temperature to which the air must be heated"),("t_db2 = %.3f")%(t_db2), ("0C")
import math
# Variables
p_vs = 0.0206; #bar
phi = 0.6;
p_t = 1.013; #bar
# Calculations and Results
p_v1 = phi*p_vs;
p_a1 = p_t-p_v1;
V = 9.; #m**3
R = 287.;
T = 291.; #K
m_a = p_a1*10**5*V/R/T;
m_v1 = 0.0828; #kg/s
#At exit at 26 0C
p_vs = 0.0336; #bar
phi = 1;
p_v = p_vs;
W2 = 0.622*p_v/(p_t-p_v);
m_v2 = W2*m_a;
m = m_v2-m_v1;
print ("(i)Make-up water required = %.3f")%(m), ("kg/s")
m_w1 = 5.5; #kg/s
m_w2 = m_w1-m;
Wi = 4.75; #kJ/s
h_w1 = 184.3; #kJ/kg
h_a1 = 18.09; #kJ/kg
h_v1 = 2534.74; #kJ/kg
h_v2 = 2549; #kJ/kg
h_a2 = 26.13; #kJ/kg
h_w2 = (Wi + m_w1*h_w1 + m_a*h_a1 + m_v1*h_v1 - m_a*h_a2 - m_v2*h_v2)/m_w2;
#By interpolation, h_w2 corresponds to t
t = 26.7; #0C
print ("(ii)final temperature of water = %.3f")%(t), ("0C")
# Variables
m_water = 60000.; #kg/s
c = 4.186;
t1 = 30.; #0C
t2 = 35.; #0C
# Calculations
Q = m_water*c*(t2-t1);
h1 = 76.5; #kJ/kg
W1 = 0.016; #kg/kg of air
h2 = 92.5; #kJ/kg
W2 = 0.0246; #kg/kg of air
m_air = Q/(h2-h1);
A = m_air/10; #Quantity of air handled per fan
# Results
print ("Quantity of air handled per fan = %.3f")%(A), ("kg/h")
B = m_air*(W2-W1);
print ("Quantity of make up water = %.3f")% (B),("kg/h")
# Variables
h1 = 35.4; #kJ/kg
h2 = 45.2; #kJ/kg
v_s1 = 0.8267; #m**3/kg
m_a = 241.9;
# Calculations and Results
RH = 41; # From chart
print ("(i) R.H. of heated air = %.3f")%(RH), ("%")
WBT = 16.1; #0C
print ("(ii) WBT of heated air = "), (WBT), ("ºC")
Q = m_a*(h2-h1);
print ("(iii) Heat added to air per minute = "), (Q), ("kJ")
# Variables
h1 = 29.3; #kJ/kg
h2 = 42.3; #kJ/kg
h3 = h2;
t_db2 = 24.5; #0C
t_db1 = 12; #0C
v_s1 = 0.817; #m**3/kg
amt = 0.30; #Amount of air circulation m**3/min/person
capacity = 60; #Seating capacity of office
BF = 0.4; #By-pass factor
W3 = 8.6;
W1 = 6.8;
# Calculations and Results
m_a = amt*capacity/v_s1;
Q = m_a*(h2-h1)/60;
print ("(i) Heating capacity of the heating coil = %.3f")%(Q), ("kW")
t_db4 = (t_db2-BF*t_db1)/(1-BF);
print ("Coil surface temperature = %.3f")%(t_db4),("ºC")
c = m_a*(W3-W1)/1000*60;
print ("(ii) The capacity of the humidifier = %.3f")% (c),("kg/h")
# Variables
h1 = 82.5; #kJ/kg
h2 = 47.5; #kJ/kg
h3 = 55.7; #kJ/kg
h5 = 36.6; #kJ/kg
W1 = 19.6; #gm/kg
W3 = 11.8; #gm/kg
t_db2 = 17.6; #0C
t_db3 = 25.; #0C
v_s1 = 0.892; #m**3/kg
amt = 250.; #m**3/min
# Calculations and Results
m_a = amt/v_s1;
capacity = m_a*(h1-h2)*60/14000.;
print ("(i) The capacity of the cooling coil = %.3f")%(capacity),("TR")
BF = (h2-h5)/(h1-h5);
print ("by-pass factor of the cooling coil = %.3f")%(BF)
Q = m_a*(h3-h2)/60.;
print ("(ii) The heating capacity of the heating coil = %.3f")%(Q),("kW")
BF = 0.3;
t_db6 = (t_db3-BF*t_db2)/(1-BF);
print ("surface temperature of heating coil = %.3f")% (t_db6), ("C")
m = m_a*(W1-W3)*60/1000.;
print ("(iii) The mass of water vapour removed per hour = %.3f")% (m), ("kg/h")