Determine the wet-bulb and dewpoint temperature the given temperature is 40°C, relative humidity is 50% and then actual station pressure is 3 millibars.
T = 40°C rh = 50% Psta = 3 hPA
Substitute the given values in the formula
Saturation Vapor Pressure (es) Calculation es = 6.112 x e(17.67x40)/(40+243.5) es = 6.112 x e2.493121693 es = 73.9490
Vapor Pressure (e) Calculation e = (73.9490 x 50) / 100 e = 3697.45 / 100 e = 36.9745
Dewpoint Temperature Calculation Td = [243.5 x ln(36.9745/6.112)] / [17.67 - ln(36.9745/6.112)] Td = 438.2938 / 15.87 Td = 27.6177°C
Substitute the given values in the formula
Its upto reach Ed is zero or absolute value of Ed is greater than 0.05
Vapor Pressure (e) Calculation From Dewpoint Temperature Calculation we get Vapor Pressure (e) value is, 36.9745
Wet-bulb Temperature Calculation
Tw | = 0 | |
Ewg | = 6.112 x e(17.67x0)/(0+243.5) | = 6.112 |
eg | = 6.112 - 3 x (40 - 0) x 0.00066 x (1 + (0.00115 x 0)) | = 6.0328 |
Tw | = 10 | |
Ed | = 36.9745 - 6.0328 | = 30.9417 |
Tw | = 10 | |
Ewg | = 6.112 x e(17.67x10)/(10+243.5) | = 12.271 |
eg | = 12.271 - 3 x (40 - 10) x 0.00066 x (1 + (0.00115 x 10)) | = 12.2116 |
Tw | = 10 + 10 | = 20 |
Ed | = 36.9745 - 12.2116 | = 24.7629 |
Tw | = 20 | |
Ewg | = 6.112 x e(17.67x20)/(20+243.5) | = 23.3695 |
eg | = 23.3695 - 3 x (40 - 20) x 0.00066 x (1 + (0.00115 x 20)) | = 23.329 |
Tw | = 20 + 10 | = 30 |
Ed | = 36.9745 - 23.329 | = 13.6455 |
Tw | = 27.65 | |
Ewg | = 6.112 x e(17.67x27.65)/(27.65+243.5) | = 37.0444 |
eg | = 37.0444 - 3 x (40-27.65) x 0.00066 x (1 +(0.00115x27.65)) | = 37.0192 |
Tw | = 27.65 - 0.01 | = 27.64 |
Ed | = 36.9745 - 37.0192 | = -0.0447 |
In this Iteration 17 Ed value is less than 0.05, so to stop the iteration. Finally the Tw is 27.64°C.