A
I need an enthalpy calculation formula to put in a macro datasheet and then this macro do it automaticlly to avoid do another extra calculation in the psychometric chart.
I saw this formula in this forum, but this was put it here two years ago:
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Here's a short BASIC program that calculates the enthalpy using dry bulb temperature and releative humidity.
10 REM ENTHALPY CALCULATION
20 REM Assumes standard atmospheric pressure (14.7 psi), see line 110
30 REM Dry-bulb temperature in degrees F (TEMP)
40 REM Relative humidity in percentage (RH)
50 REM Enthalpy in BTU/LB OF DRY AIR (H)
60 T = TEMP + 459.67
70 N = LN( T ) : REM Natural Logrithm
80 L = -10440.4 / T - 11.29465 - 0.02702235 * T + 1.289036E-005 * T ^ 2 - 2.478068E-009 * T ^ 3 + 6.545967 * N
90 S = LN-1( L ) : REM Inverse Natural Logrithm
100 P = RH / 100 * S
110 W = 0.62198 * P / ( 14.7 - P )
120 H = 0.24 * TEMP + W * ( 1061 + 0.444 * TEMP )
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But the problem is that
According to the formula, the results that I get are not acurate,
maybe
I'm putting something wrong when I calculate the "L" I check everything, But I don't get it.
Can somebody help me?
The air inlet that I have is 100°F and the humidity is 40%RH.
The enthalphy is sopposed to be in 42.9 BTU/LB according to the machine results, but I'm getting 24 BTU/Lb with this formula, what could be wrong????
Does anybody has another formula to calculate the enthalphy of the air to avoid using the psychometric char????
I saw this formula in this forum, but this was put it here two years ago:
---
Here's a short BASIC program that calculates the enthalpy using dry bulb temperature and releative humidity.
10 REM ENTHALPY CALCULATION
20 REM Assumes standard atmospheric pressure (14.7 psi), see line 110
30 REM Dry-bulb temperature in degrees F (TEMP)
40 REM Relative humidity in percentage (RH)
50 REM Enthalpy in BTU/LB OF DRY AIR (H)
60 T = TEMP + 459.67
70 N = LN( T ) : REM Natural Logrithm
80 L = -10440.4 / T - 11.29465 - 0.02702235 * T + 1.289036E-005 * T ^ 2 - 2.478068E-009 * T ^ 3 + 6.545967 * N
90 S = LN-1( L ) : REM Inverse Natural Logrithm
100 P = RH / 100 * S
110 W = 0.62198 * P / ( 14.7 - P )
120 H = 0.24 * TEMP + W * ( 1061 + 0.444 * TEMP )
---
But the problem is that
According to the formula, the results that I get are not acurate,
maybe
I'm putting something wrong when I calculate the "L" I check everything, But I don't get it.
Can somebody help me?
The air inlet that I have is 100°F and the humidity is 40%RH.
The enthalphy is sopposed to be in 42.9 BTU/LB according to the machine results, but I'm getting 24 BTU/Lb with this formula, what could be wrong????
Does anybody has another formula to calculate the enthalphy of the air to avoid using the psychometric char????