Using Returned value of a function

[programmingpat]

Hey everyone,
I have many functions that perform mathematical calculations.
Here is one for example:

Public Function internaldiamofcasingpipecalculation(ByVal Externaldiameterofcarrierpipe As Double, ByVal insulationthickness As Double) As Double

        Dim InternalDiameterofCasingPipe = Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

        Return InternalDiameterofCasingPipe
    End Function

Now in the next function I need to use the returned value of the previous function " InternalDiameterofCasingPipe":

Public Function externaldiamofcasingpipe(ByVal internaldiameterofcasingpipe As Double, ByVal jacketthickness As Double) As Double

        Dim ExternalDiameterofCasingPipe = internaldiameterofcasingpipe + 2 * (jacketthickness / 1000)

        Return ExternalDiameterofCasingPipe
    End Function

So the problem is while I am debugging I put a break point and found that the first function taht calulates the InternalDiameterofCasingPipe works fine. But when I check the value of InternalDiameterofCasingPipe in the second function its value is 0... Why is this? Is there a specific way to use the values returned by a function?

Here is the function that calls the calculations in order:

Public Sub btnOk_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOk.Click

        ' 1. Check if Metric or Imperial Units are selected.
        ' 2. Convert Entered Variables to opposite unit.
        ' 3. Determine what type of pipe is selected
        ' 4. Determine what type of casing is selected.
        ' 5. Perform Required Calculations & display them

        If optMetric.Checked Then


            Call ConvertVariableToImperial(SoilTemp, SupplyTemp, CarrierPipeWallThickness, InsulationThickness, JacketThickness, Externaldiameterofcarrierpipe, LayingDepthtoTopofPipe, TotalLengthofPipeRun,
                                           FlowRate, Temperaturetoreach)

            Call choosepipecomboboxcoding(cboChoosePipe,
                                                   HDPE,
                                                   PVC,
                                                   ABS,
                                                   FRP,
                                                   Copper,
                                                   Steel,
                                                   Ductileiron,
                                                   ImperialHDPE,
                                                   ImperialPVC,
                                                   ImperialABS,
                                                   ImperialFRP,
                                                   ImperialCopper,
                                                   ImperialSteel,
                                                   ImperialDuctileIron)
            choosecasingcomboboxcoding(cboChooseCasingPipe, HDPE, GalvanizedSteel, Aluminum, PVC, Steel, ImperialHDPE, ImperialGalvanizedSteel, ImperialAluminum, ImperialPVC, ImperialSteel)


            InternalDiamCarrierPipeCalculation(Externaldiameterofcarrierpipe, CarrierPipeWallThickness)

            internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)

            externaldiamofcasingpipe(InternalDiameterofCasingPipe, JacketThickness)

            layingdepthtocenterlineofpipecal(LayingDepthtoTopofPipe, ExternalDiameterofCasingPipe)

            crosssectionalareaofpipecal(Externaldiameterofcarrierpipe, CarrierPipeWallThickness)

            thermalresistanceofinsulationcal(ThermalConductivityofInsulation, InternalDiameterofCasingPipe, Externaldiameterofcarrierpipe)

            thermalresistanceofthecarrierpipecal(ThermalConductivityofCarrierPipe, Externaldiameterofcarrierpipe, InternalDiameterofCarrierPipe)

            thermalresistanceofthejacketpipecal(ThermalConductivityofCasingPipe, ExternalDiameterofCasingPipe, InternalDiameterofCasingPipe)

            thermalresistanceofsoilcal(ThermalConductivityofSoil, LayingDepthToCenterlineOfPipe, ExternalDiameterofCasingPipe)

            timetoreachtempcal(Temperaturetoreach, SoilTemp, SupplyTemp, InternalDiameterofCarrierPipe, ThermalResistanceofTheInsulation, ThermalResistanceOfTheCarrierPipe,
                               ThermalResistanceofTheJacketPipe, ThermalResistanceOfTheSoil)

            totalheatgainfromsoilonpiperuncal(TotalLengthofPipeRun, HeatGain)

            increaseinsupplytempatoutletcal(TotalHeatGainFromSoilonPipeRun, FlowRateImperial)




            Call HeatTransmissionCoefficientforAsinglePipeCalculation(ThermalResistanceofTheInsulation, ThermalResistanceOfTheCarrierPipe, ThermalResistanceofTheJacketPipe,
                                                                      ThermalResistanceOfTheSoil)

            Call HeatGainCalculation(HeatTransmissionCoefficientforASinglePipe,
                                     SoilTemp,
                                     SupplyTemp)


            Call VelocityCalculation(FlowRate, Externaldiameterofcarrierpipe, CarrierPipeWallThickness)


        ElseIf optImperial.Checked Then

            ImperialSoilTemp = SoilTemp
            ImperialSupplyTemp = SupplyTemp
            ImperialCarrierPipeWallThickness = CarrierPipeWallThickness
            ImperialInsulationThickness = InsulationThickness
            ImperialJacketThickness = JacketThickness
            ImperialExternaldiameterofcarrierpipe = Externaldiameterofcarrierpipe
            ImperialLayingDepthtoTopofPipe = LayingDepthtoTopofPipe
            ImperialTotalLengthofPipeRun = TotalLengthofPipeRun
            ImperialTemperaturetoreach = Temperaturetoreach
            FlowRateImperial = FlowRate

            Call ConvertVariablesToMetric(ImperialSoilTemp, ImperialSupplyTemp, ImperialCarrierPipeWallThickness, ImperialInsulationThickness, ImperialJacketThickness, ImperialExternaldiameterofcarrierpipe,
                                          ImperialLayingDepthtoTopofPipe, ImperialTotalLengthofPipeRun, ImperialTemperaturetoreach)

            Call choosepipecomboboxcoding(cboChoosePipe,
                                                  HDPE,
                                                  PVC,
                                                  ABS,
                                                  FRP,
                                                  Copper,
                                                  Steel,
                                                  Ductileiron,
                                                  ImperialHDPE,
                                                  ImperialPVC,
                                                  ImperialABS,
                                                  ImperialFRP,
                                                  ImperialCopper,
                                                  ImperialSteel,
                                                  ImperialDuctileIron)
            choosecasingcomboboxcoding(cboChooseCasingPipe, HDPE, GalvanizedSteel, Aluminum, PVC, Steel, ImperialHDPE, ImperialGalvanizedSteel, ImperialAluminum, ImperialPVC, ImperialSteel)


            InternalDiamCarrierPipeCalculation(Externaldiameterofcarrierpipe, CarrierPipeWallThickness)

            internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)

            externaldiamofcasingpipe(InternalDiameterofCasingPipe, JacketThickness)

            layingdepthtocenterlineofpipecal(LayingDepthtoTopofPipe, ExternalDiameterofCasingPipe)

            crosssectionalareaofpipecal(Externaldiameterofcarrierpipe, CarrierPipeWallThickness)

            thermalresistanceofinsulationcal(ThermalConductivityofInsulation, InternalDiameterofCasingPipe, Externaldiameterofcarrierpipe)

            thermalresistanceofthecarrierpipecal(ThermalConductivityofCarrierPipe, Externaldiameterofcarrierpipe, InternalDiameterofCarrierPipe)

            thermalresistanceofthejacketpipecal(ThermalConductivityofCasingPipe, ExternalDiameterofCasingPipe, InternalDiameterofCasingPipe)

            thermalresistanceofsoilcal(ThermalConductivityofSoil, LayingDepthToCenterlineOfPipe, ExternalDiameterofCasingPipe)

            timetoreachtempcal(Temperaturetoreach, SoilTemp, SupplyTemp, InternalDiameterofCarrierPipe, ThermalResistanceofTheInsulation, ThermalResistanceOfTheCarrierPipe,
                               ThermalResistanceofTheJacketPipe, ThermalResistanceOfTheSoil)

            totalheatgainfromsoilonpiperuncal(TotalLengthofPipeRun, HeatGain)

            increaseinsupplytempatoutletcal(TotalHeatGainFromSoilonPipeRun, FlowRateImperial)



            Call HeatTransmissionCoefficientforAsinglePipeCalculation(ThermalResistanceofTheInsulation, ThermalResistanceOfTheCarrierPipe, ThermalResistanceofTheJacketPipe,
                                                                      ThermalResistanceOfTheSoil)

            Call VelocityCalculation(FlowRate, Externaldiameterofcarrierpipe, CarrierPipeWallThickness)


        Else
            ' Error Message Box Signaling the user if he forgets to mention the units
            MessageBox.Show("Please Select The Units You Are Working With.")

        End If





    End Sub

Thanks!!

[bergerkiller]

You are not specifying a value type to store it in, replace:

Dim InternalDiameterofCasingPipe = Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

With:

Dim InternalDiameterofCasingPipe As Double = Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

Not sure what happens when not specifying a type, so I recommend avoiding this at all.

Or, even better:

Return Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

EDIT

Your code is extremely hard to read because of all the long function names, but this could be the issue, but I am not sure.
You have to use the result of the previous function in your next function:

InternalDiameterofCasingPipe = internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)
externaldiamofcasingpipe(InternalDiameterofCasingPipe, JacketThickness)

[programmingpat]

Ok, I am not sure if I properly understood that last part but if im correct my code for the funciton that will be using the result from the previous function should look like this?:

    Public Function externaldiamofcasingpipe(ByVal jacketthickness As Double) As Double

        internaldiameterofcasingpipe = internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)
        Dim ExternalDiameterofCasingPipe As Double = internaldiameterofcasingpipe + 2 * (jacketthickness / 1000)

        Return ExternalDiameterofCasingPipe
    End Function

[Sitten Spynne]

Uhhh... this was the first draft of the post below. Not sure how it got here; I guess I hit the wrong button. You didn't see this. Move along!

[Sitten Spynne]

Let's pick some easier methods to keep things sane.

Let's say you have an Add() function and a Subtract() function:

Public Sub Add(ByVal left As Integer, ByVal right As Integer) As Integer
    Return left + right
End Sub

Public Sub Subtract(ByVal left As Integer, ByVal right As Integer) As Integer
    Return left - right
End Sub

Now let's say you want to evaluate 2 + 3 - 4. Obviously Add() comes first, and Subtract() needs a way to subtract 4 from that result. You *could* add a variable to keep track of this:

Private lastAddResult As Integer = 0
Public Sub Add(...)
    lastAddResult = left + right
    Return lastAddResult
End Sub

Public Sub Subtract(ByVal right As Integer)
    Return lastAddResult - right
End Sub

This is not a good idea. What happens when you want to try 2 - 3 + 4? Add() doesn't know about any subtraction results! But if you add it, then subtract has to be wrong because it needs to do left - right! You can add overrides to make this work. Then you find out you need to implement Multiply(). Oh no! How does Subtract(Integer) know whether it should use the result from Add() or Subtract()?

When something starts getting hard, you're probably doing it wrong. So let's think about it again. How would you do 2 + 3 - 4 by hand?

• Add 2 + 3 and store the result.
• Subtract 4 from the result.

Hmm... I had to store the result somewhere. That's an idea. What if I go back to the original Add() and Subtract() and use them this way:

Dim result As Integer
result = Add(2, 3)
result = Subtract(result, 4)

That's what bergerkiller's saying. If you want to use a result from another function, you have to store that result in a variable that the second function can see. The best way to do that is to make it a parameter of the next function. I'd like to show you how to change your code to fix it, but there's a lot of things missing and I think it'd be some major changes. Let's say for a second that "internaldiamofcasingpipecalculation" is working fine. Here's how you might make your first examples work:

Dim internalDiameter As Double = internaldiamofcasingpipecalculation(...)
Dim externalDiameter As Double = externaldiamofcasingpipe(internalDiameter, ...)

See how I stored the result in a variable, then used that variable in the next function? That's how it should work.

[programmingpat]

I think I got the idea. I am still new to programming so there is still ALOT to learn...
My code still needs alot of debugging and fixing but I think I am on the right track because the results are finaly making some sence.
Here is what I have just spent the last hour fixing:

' Internal Diameter of Carrier Pipe Calculation
    Public Function InternalDiamCarrierPipeCalculation(ByVal Externaldiameterofcarrierpipe As Double, ByVal carrierpipewallthickness As Double) As Double

        Dim InternalDiameterofCarrierPipe As Double = Externaldiameterofcarrierpipe - 2 * (carrierpipewallthickness / 1000)

        Return InternalDiameterofCarrierPipe

    End Function
    ' Internal Diameter of Casing Pipe Calculation
    Public Function internaldiamofcasingpipecalculation(ByVal Externaldiameterofcarrierpipe As Double, ByVal insulationthickness As Double) As Double

        Dim InternalDiameterofCasingPipe As Double = Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

        Return InternalDiameterofCasingPipe
    End Function
    ' External Diameter of Casing Pipe Calculation
    Public Function externaldiamofcasingpipe(ByVal internaldiameterofcasingpipe As Double, ByVal jacketthickness As Double) As Double

        internaldiameterofcasingpipe = internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)
        Dim ExternalDiameterofCasingPipe As Double = InternalDiameterofCasingPipe + 2 * (jacketthickness / 1000)

        Return ExternalDiameterofCasingPipe
    End Function
    ' Laying depth to center line of pipe calculations
    Public Function layingdepthtocenterlineofpipecal(ByVal layingdepthtotopofpipe As Double, ByVal externaldiameterofcasingpipe As Double) As Double

        externaldiameterofcasingpipe = externaldiamofcasingpipe(InternalDiameterofCasingPipe, JacketThickness)
        Dim LayingDepthToCenterlineOfPipe As Double = layingdepthtotopofpipe + externaldiameterofcasingpipe / 2

        Return LayingDepthToCenterlineOfPipe
    End Function
    ' Crosssectional area of pipe calculation
    Public Function crosssectionalareaofpipecal(ByVal externaldiameterofcarrierpipe As Double, ByVal carrierpipewallthickness As Double) As Double


        Dim CrossSectionalAreaOfPipe As Double = 3.1415926 * (((externaldiameterofcarrierpipe / 2) ^ 2) - ((externaldiameterofcarrierpipe - 2 * (carrierpipewallthickness / 1000)) / 2) ^ 2)

        Return CrossSectionalAreaOfPipe
    End Function
    ' Thermal Resistance of Insulation calculation
    Public Function thermalresistanceofinsulationcal(ByVal thermalconductivityofinsulation As Double, ByVal internaldiameterofcasingpipe As Double, ByVal externaldiameterofcarrierpipe As Double) As Double

        internaldiameterofcasingpipe = internaldiamofcasingpipecalculation(externaldiameterofcarrierpipe, InsulationThickness)

        Dim ThermalResistanceofTheInsulation As Double = ((1 / (2 * 3.1416 * thermalconductivityofinsulation)) * (Math.Log(internaldiameterofcasingpipe / externaldiameterofcarrierpipe)))

        Return ThermalResistanceofTheInsulation
    End Function
    ' Thermal Resistance of the carrier pipe calculation
    Public Function thermalresistanceofthecarrierpipecal(ByVal thermalconductivityofcarrierpipe As Double, ByVal externaldiameterofcarrierpipe As Double, ByVal internaldiameterofcarrierpipe As Double) As Double
        internaldiameterofcarrierpipe = InternalDiamCarrierPipeCalculation(externaldiameterofcarrierpipe, CarrierPipeWallThickness)
        Dim ThermalResistanceOfTheCarrierPipe As Double = ((1 / (2 * 3.1416 * thermalconductivityofcarrierpipe)) * Math.Log(externaldiameterofcarrierpipe / internaldiameterofcarrierpipe))

        Return ThermalResistanceOfTheCarrierPipe
    End Function
    ' Thermal Resistance of the Jacket Pipe Calculation
    Public Function thermalresistanceofthejacketpipecal(ByVal thermalconductivityofcasingpipe As Double, ByVal externaldiameterofcasingpipe As Double, ByVal internaldiameterofcasingpipe As Double) As Double

        internaldiameterofcasingpipe = internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)
        externaldiameterofcasingpipe = externaldiamofcasingpipe(internaldiameterofcasingpipe, JacketThickness)

        Dim ThermalResistanceofTheJacketPipe As Double = ((1 / (2 * 3.1416 * thermalconductivityofcasingpipe))) * (Math.Log(externaldiameterofcasingpipe / internaldiameterofcasingpipe))

        Return ThermalResistanceofTheJacketPipe
    End Function
    ' Thermal resistance of soil calculation
    Public Function thermalresistanceofsoilcal(ByVal thermalconductivityofsoil As Double, ByVal layingdepthtocenterlineofpipe As Double, ByVal externaldiameterofcasingpipe As Double) As Double

        externaldiameterofcasingpipe = externaldiamofcasingpipe(InternalDiameterofCasingPipe, JacketThickness)
        Dim ThermalResistanceOfTheSoil As Double = ((1 / (2 * 3.1416 * thermalconductivityofsoil)) * (Math.Log(4 * (layingdepthtocenterlineofpipe + 0.0685 * thermalconductivityofsoil) / externaldiameterofcasingpipe)))

        Return ThermalResistanceOfTheSoil
    End Function
    ' Time to reach temperature calculation
    Public Function timetoreachtempcal(ByVal temperaturetoreach As Double, ByVal soiltemp As Double, ByVal supplytemp As Double, ByVal internaldiameterofcarrierpipe As Double, ByVal thermalresistanceoftheinsulation As Double, ByVal thermalresistanceofthecarrierpipe As Double, ByVal thermalresistanceofthejacketpipe As Double, ByVal thermalresistanceofthesoil As Double) As Double

        'Time to reach
        internaldiameterofcarrierpipe = InternalDiamCarrierPipeCalculation(Externaldiameterofcarrierpipe, CarrierPipeWallThickness)
        Dim TimeToReachTemperature As Double = -1 * Math.Log((temperaturetoreach - soiltemp) / (supplytemp - soiltemp)) * 998 * 3.1416 * (internaldiameterofcarrierpipe / 2) * (internaldiameterofcarrierpipe / 2) * (thermalresistanceoftheinsulation + thermalresistanceofthecarrierpipe + thermalresistanceofthejacketpipe + thermalresistanceofthesoil) *
        (4190 / 3600)
        Dim RoundedTimeToReachTemperature As Double = Math.Round(TimeToReachTemperature, 3)
        lblTimetoReachTemperature.Text = "Time To Reach Temperature : " & RoundedTimeToReachTemperature & " Hours"

        Return RoundedTimeToReachTemperature
    End Function

[programmingpat]

'Total Heat Gain From Soil On Pipe Run Calculaiton
    Public Function totalheatgainfromsoilonpiperuncal(ByVal totallengthofpiperun As Double, ByVal HeatGain As Double) As Double


        HeatGain = HeatGainCalculation(HeatTransmissionCoefficientforASinglePipe, SoilTemp, SupplyTemp)

        Dim TotalHeatGainFromSoilonPipeRun As Double = totallengthofpiperun * HeatGain
        Dim RoundedTotalHeatGainFromSoilonPipeRun As Double = Math.Round(TotalHeatGainFromSoilonPipeRun, 3)

        If RoundedTotalHeatGainFromSoilonPipeRun > 0 Then
            lblTotalHeatGainFromSoilOnPipeRun.Text = " Total Heat Gain From Soil On Pipe Run : " & RoundedTotalHeatGainFromSoilonPipeRun & " Watts "
        ElseIf RoundedTotalHeatGainFromSoilonPipeRun < 0 Then
            lblTotalHeatGainFromSoilOnPipeRun.Text = " Total Heat Loss From Soil On Pipe Run : " & RoundedTotalHeatGainFromSoilonPipeRun & " Watts "
        End If

        Return RoundedTotalHeatGainfromsoilonPipeRun
    End Function
    'HeatGain Calculation
    Public Function HeatGainCalculation(ByVal HeatTransmissionCoefficientforASinglePipe As Double,
                                    ByVal SoilTemp As Double,
                                    ByVal SupplyTemp As Double) As Double

        InternalDiameterofCasingPipe = internaldiamofcasingpipecalculation(Externaldiameterofcarrierpipe, InsulationThickness)
        ExternalDiameterofCasingPipe = externaldiamofcasingpipe(InternalDiameterofCasingPipe, JacketThickness)
        LayingDepthToCenterlineOfPipe = layingdepthtocenterlineofpipecal(LayingDepthtoTopofPipe, ExternalDiameterofCasingPipe)
        InternalDiameterofCarrierPipe = InternalDiamCarrierPipeCalculation(Externaldiameterofcarrierpipe, CarrierPipeWallThickness)

        ThermalResistanceofTheInsulation = thermalresistanceofinsulationcal(ThermalConductivityofInsulation, InternalDiameterofCasingPipe, Externaldiameterofcarrierpipe)
        ThermalResistanceOfTheCarrierPipe = thermalresistanceofthecarrierpipecal(ThermalConductivityofCarrierPipe, Externaldiameterofcarrierpipe, InternalDiameterofCarrierPipe)
        ThermalResistanceofTheJacketPipe = thermalresistanceofthejacketpipecal(ThermalConductivityofCasingPipe, ExternalDiameterofCasingPipe, InternalDiameterofCasingPipe)
        ThermalResistanceOfTheSoil = thermalresistanceofsoilcal(ThermalConductivityofSoil, LayingDepthToCenterlineOfPipe, ExternalDiameterofCasingPipe)
        HeatTransmissionCoefficientforASinglePipe = HeatTransmissionCoefficientforAsinglePipeCalculation(ThermalResistanceofTheInsulation, ThermalResistanceOfTheCarrierPipe,
                                                                                                         ThermalResistanceofTheJacketPipe, ThermalResistanceOfTheSoil)

        Dim HeatGain As Double = HeatTransmissionCoefficientforASinglePipe * (SoilTemp - SupplyTemp)
        Dim RoundedHeatGain As Double = Math.Round(HeatGain, 3)

        If RoundedHeatGain > 0 Then
            lblHeatGain.Text = " HeatGain : " & RoundedHeatGain & " W/m "
        ElseIf RoundedHeatGain < 0 Then
            lblHeatGain.Text = " HeatLoss : " & RoundedHeatGain & " W/m "

        End If
        Return HeatGain

    End Function
    ' Increase in supply temp at outlet
    Public Function increaseinsupplytempatoutletcal(ByVal totalheatgainfromsoilonpiperun As Double, ByVal flowrateimperial As Double) As Double


        totalheatgainfromsoilonpiperun = totalheatgainfromsoilonpiperuncal(TotalLengthofPipeRun, HeatGain)
        flowrateimperial = ConvertVariableToImperial(SoilTemp, SupplyTemp, CarrierPipeWallThickness, InsulationThickness, JacketThickness, Externaldiameterofcarrierpipe,
                                                     LayingDepthtoTopofPipe, TotalLengthofPipeRun, FlowRate, Temperaturetoreach)
        Dim IncreaseInSupplyTemperatureAtOutlet As Double = totalheatgainfromsoilonpiperun / (flowrateimperial * 998 * 4190 * 0.000063)
        Dim RoundedIncreaseInsupplyTemperatureAtOutlet As Double = Math.Round(IncreaseInSupplyTemperatureAtOutlet, 3)

        If RoundedIncreaseInsupplyTemperatureAtOutlet > 0 Then
            lblIncreaseinSupplyTemperatureatOutlet.Text = " Incease in supply temperature at outlet : " & RoundedIncreaseInsupplyTemperatureAtOutlet & " Degree C"
        ElseIf RoundedIncreaseInsupplyTemperatureAtOutlet < 0 Then
            lblIncreaseinSupplyTemperatureatOutlet.Text = " Decrease in supply temperature at outlet : " & RoundedIncreaseInsupplyTemperatureAtOutlet & " Degree C"
        End If

        Return RoundedIncreaseInSupplyTemperatureAtOutlet
    End Function
    ' Heat transmission coefficient for a single pipe calculation
    Public Function HeatTransmissionCoefficientforAsinglePipeCalculation(ByVal ThermalResistanceofTheInsulation As Double,
                                                                         ByVal ThermalResistanceOfTheCarrierPipe As Double,
                                                                         ByVal ThermalResistanceofTheJacketPipe As Double,
                                                                         ByVal ThermalResistanceOftheSoil As Double) As Double

        ThermalResistanceofTheInsulation = thermalresistanceofinsulationcal(ThermalConductivityofInsulation, InternalDiameterofCasingPipe, Externaldiameterofcarrierpipe)
        ThermalResistanceOfTheCarrierPipe = thermalresistanceofthecarrierpipecal(ThermalConductivityofCarrierPipe, Externaldiameterofcarrierpipe, InternalDiameterofCarrierPipe)
        ThermalResistanceofTheJacketPipe = thermalresistanceofthejacketpipecal(ThermalConductivityofCasingPipe, ExternalDiameterofCasingPipe, InternalDiameterofCasingPipe)
        ThermalResistanceOftheSoil = thermalresistanceofsoilcal(ThermalConductivityofSoil, LayingDepthToCenterlineOfPipe, ExternalDiameterofCasingPipe)

        Dim HeatTransmissionCoefficientforASinglePipe As Double = (1 / (ThermalResistanceofTheInsulation + ThermalResistanceOfTheCarrierPipe + ThermalResistanceofTheJacketPipe + ThermalResistanceOftheSoil))

        Return HeatTransmissionCoefficientforASinglePipe

    End Function

    ' Velocity Calculation

    Public Function VelocityCalculation(ByVal txtFlowRate As Double, ByVal txtExternaldiameterofcarrierpipe As Double, ByVal txtCarrierPipeWallThickness As Double) As Double

        Dim InternalDiameterofCarrierPipe As Double = (Externaldiameterofcarrierpipe - 2) * (CarrierPipeWallThickness / 1000)
        Dim Velocity As Double = FlowRate * 0.001 / (3.1416 * InternalDiameterofCarrierPipe * (InternalDiameterofCarrierPipe / 4))
        Dim RoundedVelocity = Math.Round(Velocity, 3)
        lblVelocity.Text = " Velocity : " & RoundedVelocity & " m / sec "



        Return Velocity

        Exit Function
    End Function

[bergerkiller]

I have another tip to organize your code, and that is storing your functions as shared in classes:

    Public Class PipeCasing
        Public Shared Function InternalDiam(ByVal ExternalDiam As Double, ByVal InsulationThickness As Double) As Double
            Return ExternalDiam + 2 * (InsulationThickness / 1000)
        End Function
        Public Shared Function ExternalDiam(ByVal InternalDiam As Double, ByVal JacketThickness As Double) As Double
            Return InternalDiam + 2 * (JacketThickness / 1000)
        End Function
    End Class
    Public Class PipeCarrier
        Public Shared Function InternalDiam(ByVal ExternalDiam As Double, ByVal WallThickness As Double) As Double
            Return ExternalDiam - 2 * (WallThickness / 1000)
        End Function
    End Class

For some other calculations this is a bit harder. Try at best to get your calculations inside a class, or even better, have all "pipe objects" as a separate class. Like this:

    Public Class Pipe
        Public MyCarrier As Carrier
        Public MyCasing As Casing
        Public MyInsulation As Insulation
        Public MyCrossSection As CrossSection

        Public Class Carrier
            Public InternalDiam As Double
            Public ExternalDiam As Double
        End Class
        Public Class Casing
            Public InternalDiam As Double
            Public ExternalDiam As Double
        End Class
        Public Class Insulation
            Public ThermalResistance As Double
        End Class
        Public Class CrossSection
            Public Area As Double
        End Class
    End Class

You can also add functions to these sub classes, or do the calculation in the new sub. (in the constructor)

        Public Class Casing
            Sub New(ByVal InternalDiameter As Double, ByVal JacketThickness As Double)
                Me.InternalDiam = InternalDiam
                Me.ExternalDiam = InternalDiam + 2 * (JacketThickness / 1000)
            End Sub
            Public InternalDiam As Double
            Public ExternalDiam As Double
        End Class

So you can organize your code and make it look very clean:

        Dim p As New Pipe()
        p.MyCasing = New Pipe.Casing(100, 200)

So instead of:

ThermalResistanceofTheJacketPipe

You get:

Pipe.Jacket.ThermalResistance

[NickThissen]

You are not specifying a value type to store it in, replace:

Dim InternalDiameterofCasingPipe = Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

With:

Dim InternalDiameterofCasingPipe As Double = Externaldiameterofcarrierpipe + 2 * (insulationthickness / 1000)

Not sure what happens when not specifying a type, so I recommend avoiding this at all.

A little off-topic, but as long as Option Infer is on (which it should be by default) then not specifying the type is fine, and VB will infer ('guess') the type from the expression you assign to it.

For example

Dim x = 3   'x is of type Integer
Dim y = "Hi"  'y is of type String
Dim z = New Button()  'z is of type Button

In your case you are assigning a calculation so you'd have to know the specifics of how VB handles calculations, but it will likely be a Double (I'm too lazy to figure it out at the moment, but since you are dividing it should be Double).

(If you're familiar with C#, this is the equivalent of the 'var' keyword in C#)