Help with Function

nutttom

New Member
Joined
Oct 7, 2015
Messages
2
Hi can someone please help with my VBA function:

The WB Function is return a #VALUE! error and I can't understand way. Here is the code:

Thank you Tom


'====================================================================================================================='
' Constants
'====================================================================================================================='

Const CONST_01 = -5674.5359
Const CONST_02 = 6.3925247
Const CONST_03 = -0.009677843
Const CONST_04 = 0.000000622157
Const CONST_05 = 2.0747825E-09
Const CONST_06 = -9.484024E-13
Const CONST_07 = 4.1635019
Const CONST_08 = -5800.2206
Const CONST_09 = 1.3914993
Const CONST_10 = -0.048640239
Const CONST_11 = 0.000041764768
Const CONST_12 = -0.000000014452093
Const CONST_13 = 6.5459673
Const CONST_14 = 6.54
Const CONST_15 = 14.526
Const CONST_16 = 0.7389
Const CONST_17 = 0.09486
Const CONST_18 = 0.4569

Const R_WATER = 18.015268
Const R_AIR = 28.964546

'1) Equation 1: Get humidity from paritial vapour pressure and saturated vapour pressure.

Function get_humidity(ByVal paritial_vapour_pressure As Variant, ByVal saturated_vapour_pressure As Variant)

get_humidity = (paritial_vapour_pressure / saturated_vapour_pressure) * 100

End Function

'5) Equation 5: Get saturated vapour pressure from dry bulb.

Function get_saturated_vapour_pressure(ByVal dry_bulb As Variant)

If dry_bulb >= 0 Then
get_saturated_vapour_pressure = (Exp(CONST_08 / (dry_bulb + 273.15) + CONST_09 + CONST_10 * (dry_bulb + 273.15) + CONST_11 * (dry_bulb + 273.15) ^ 2 + CONST_12 * (dry_bulb + 273.15) ^ 3 + CONST_13 * Log((dry_bulb + 273.15)))) / 1000
Else:
get_saturated_vapour_pressure = (Exp(CONST_01 / (dry_bulb + 273.15) + CONST_02 + CONST_03 * (dry_bulb + 273.15) + CONST_04 * (dry_bulb + 273.15) ^ 2 + CONST_05 * (dry_bulb + 273.15) ^ 3 + CONST_06 * (dry_bulb + 273.15) ^ 4 + CONST_07 * Log((dry_bulb + 273.15)))) / 1000
End If

End Function

'6) Equation 6: Get humidity ratio from dry bulb vapour pressure and pressure.

Function get_humidity_ratio(ByVal dry_bulb_vapour_pressure As Variant, ByVal pressure As Variant)

get_humidity_ratio = R_WATER / R_AIR * dry_bulb_vapour_pressure / (pressure - dry_bulb_vapour_pressure)

End Function

'7) Equation 7: Get moisture content from wet buld, humidity ratio and dry bulb.

Function get_moisture_content(ByVal wet_bulb As Variant, ByVal humidity_ratio As Variant, ByVal dry_bulb As Variant)

If dry_bulb <= 0 Then
get_moisture_content = ((2830 - 0.24 * wet_bulb) * humidity_ratio - 1.006 * (dry_bulb - wet_bulb)) / (2830 + 1.86 * dry_bulb - 2.1 * wet_bulb)
Else:
get_moisture_content = ((2501 - 2.326 * wet_bulb) * humidity_ratio - 1.006 * (dry_bulb - wet_bulb)) / (2501 + 1.86 * dry_bulb - 4.186 * wet_bulb)

End If

End Function

'8) Equation 8: Get dry bulb vapour pressure from wet bulb.
Function get_dry_bulb_vapour_pressure(ByVal wet_bulb As Variant)

If (wet_bulb + 273.15) >= 0 Then
get_dry_bulb_vapour_pressure = Exp(CONST_08 / (wet_bulb + 273.15) + CONST_09 + CONST_10 * (wet_bulb + 273.15) + CONST_11 * (wet_bulb + 273.15) ^ 2 + CONST_12 * (wet_bulb + 273.15) ^ 3 + CONST_13 * Log((wet_bulb + 273.15))) / 1000
Else:
get_dry_bulb_vapour_pressure = Exp(CONST_01 / (wet_bulb + 273.15) + CONST_02 + CONST_03 * (wet_bulb + 273.15) + CONST_04 * (wet_bulb + 273.15) ^ 2 + CONST_05 * (wet_bulb + 273.15) ^ 3 + CONST_06 * (wet_bulb + 273.15) ^ 4 + CONST_07 * Log((wet_bulb + 273.15))) / 1000
End If

End Function

'9) Equation 9: Get partial vapour pressure from pressure and moisture content.

Function get_partial_vapour_pressure(ByVal pressure As Variant, ByVal moisture_content As Variant)

get_partial_vapour_pressure = (pressure * moisture_content) / (0.621945 + moisture_content)

End Function

'10) Equation 10: Get enthalpy from dry bulb and moisture content.

Function get_enthalpy(ByVal dry_bulb As Variant, ByVal moisture_content As Variant)

get_enthalpy = 1.006 * dry_bulb + moisture_content * (2501 + 1.86 * dry_bulb)

End Function

'11) Equation 11: Get pressure from altitude.

Function get_pressure(ByVal altitude As Variant):

get_pressure = 101.325 * (1 - 0.0000225577 * altitude) ^ 5.2559

End Function

'12) Equation 12: Get specific volume from dry bulb, moisture content and pressure.

Function get_specific_volume(ByVal dry_bulb As Variant, ByVal moisture_content As Variant, ByVal pressure As Variant):

get_specific_volume = (0.287042 * (dry_bulb + 273.15)) * (1 + 1.607858 * moisture_content) / pressure

End Function

'13) Equation 13: Get dew point temperature from partial vapour pressure.

Function get_dew_point_temperature(ByVal partial_vapour_pressure As Variant)

If dry_bulb <= 93 And dry_bulb >= 0 Then

get_dew_point_temperature = 6.54 + 14.526 * Log(partial_vapour_pressure) + 0.7389 * Log(partial_vapour_pressure) * Log(partial_vapour_pressure) + 0.09486 * Log(partial_vapour_pressure) ^ 3 + 0.4569 * partial_vapour_pressure ^ 0.1984

ElseIf dry_bulb < 0 Then

get_dew_point_temperature = 6.09 + 12.608 * Log(partial_vapour_pressure) + 0.4959 * Log(partial_vapour_pressure) * Log(partial_vapour_pressure)

Else
get_dew_point_temperature = "Error"

End If

End Function


Function hum_acc(ByVal humidity As Variant, ByVal humidity_loop As Variant)

If (humidity / humidity_loop) < 1.1 And (humidity / humidity_loop) > 0.9 Then

hum_acc = True

Else

hum_acc = False

End If

End Function


Function WB(ByVal altitude As Variant, ByVal dry_bulb As Variant, ByVal humidity As Variant) As Variant

Dim wet_bulb As Variant
Dim wb_loop As Variant
Dim saturated_vapour_pressure As Variant
Dim pressure As Variant
Dim dry_bulb_vapour_pressure As Variant
Dim humidity_ratio As Variant
Dim moisture_content As Variant
Dim partial_vapour_pressure As Variant
Dim hum_ok As Boolean

wb_loop = 0.001
wet_bulb = dry_bulb

Do

wet_bulb = wet_bulb - wb_loop
saturated_vapour_pressure = get_saturated_vapour_pressure(dry_bulb)
pressure = get_pressure(altitude)
dry_bulb_vapour_pressure = get_dry_bulb_vapour_pressure(wet_bulb)
humidity_ratio = get_humidity_ratio(dry_bulb_vapour_pressure, pressure)
moisture_content = get_moisture_content(wet_bulb, humidity_ratio, dry_bulb)
partial_vapour_pressure = get_partial_vapour_pressure(pressure, moisture_content)

humidity_loop = get_humidity(paritial_vapour_pressure, saturated_vapour_pressure)

hum_ok = hum_acc(humidity, humidity_loop)

Loop Until hum_ok = True

WB = 1000

End Function
 

Excel Facts

What does custom number format of ;;; mean?
Three semi-colons will hide the value in the cell. Although most people use white font instead.

Watch MrExcel Video

Forum statistics

Threads
1,132,799
Messages
5,655,367
Members
418,193
Latest member
RichKatzRich

We've detected that you are using an adblocker.

We have a great community of people providing Excel help here, but the hosting costs are enormous. You can help keep this site running by allowing ads on MrExcel.com.
Allow Ads at MrExcel

Which adblocker are you using?

Disable AdBlock

Follow these easy steps to disable AdBlock

1)Click on the icon in the browser’s toolbar.
2)Click on the icon in the browser’s toolbar.
2)Click on the "Pause on this site" option.
Go back

Disable AdBlock Plus

Follow these easy steps to disable AdBlock Plus

1)Click on the icon in the browser’s toolbar.
2)Click on the toggle to disable it for "mrexcel.com".
Go back

Disable uBlock Origin

Follow these easy steps to disable uBlock Origin

1)Click on the icon in the browser’s toolbar.
2)Click on the "Power" button.
3)Click on the "Refresh" button.
Go back

Disable uBlock

Follow these easy steps to disable uBlock

1)Click on the icon in the browser’s toolbar.
2)Click on the "Power" button.
3)Click on the "Refresh" button.
Go back
Top