total pressure formula

Discussion in 'HVAC' started by richardscheff@gmail.com, Dec 10, 2005.

  1. Guest

    I am doing computer simulations of HVAC system. I have tried
    calculating total pressure using Wright equatiuon and Loeffler
    equation; both result in numbers that I think are too low.
    Do you know if these formulas are a calculation of total pressure,
    static pressure, or velocity pressure.

    Their root is the Darcy-Weisbach friction coefficient equation.

    Am I missing something?
    I calculate total pressure of the ducts based on lengths. Then I add
    velocity pressure of joints and bends. The sum should be Total
    Pressure.

    Also this is a calculation of the furthest hood and all the ducts
    required to reach the fan.

    Thank you
     
    , Dec 10, 2005
    #1
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  2. Oscar_Lives Guest

    <> wrote in message
    news:...
    >I am doing computer simulations of HVAC system. I have tried
    > calculating total pressure using Wright equatiuon and Loeffler
    > equation; both result in numbers that I think are too low.
    > Do you know if these formulas are a calculation of total pressure,
    > static pressure, or velocity pressure.
    >
    > Their root is the Darcy-Weisbach friction coefficient equation.
    >
    > Am I missing something?
    > I calculate total pressure of the ducts based on lengths. Then I add
    > velocity pressure of joints and bends. The sum should be Total
    > Pressure.
    >
    > Also this is a calculation of the furthest hood and all the ducts
    > required to reach the fan.
    >
    > Thank you
    >


    Length isn't as important as most folks think.
     
    Oscar_Lives, Dec 10, 2005
    #2
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  3. On Sat, 10 Dec 2005 04:11:26 GMT, "Oscar_Lives" <>
    wrote:

    >
    ><> wrote in message
    >news:...
    >>I am doing computer simulations of HVAC system. I have tried
    >> calculating total pressure using Wright equatiuon and Loeffler
    >> equation; both result in numbers that I think are too low.
    >> Do you know if these formulas are a calculation of total pressure,
    >> static pressure, or velocity pressure.
    >>
    >> Their root is the Darcy-Weisbach friction coefficient equation.
    >>
    >> Am I missing something?
    >> I calculate total pressure of the ducts based on lengths. Then I add
    >> velocity pressure of joints and bends. The sum should be Total
    >> Pressure.
    >>
    >> Also this is a calculation of the furthest hood and all the ducts
    >> required to reach the fan.
    >>
    >> Thank you
    >>

    >
    >Length isn't as important as most folks think.
    >


    Keep telling her that.


    --

    Click here every day to feed an animal that needs you today !!!

    http://www.theanimalrescuesite.com/

    Paul ( pjm @ pobox . com ) - remove spaces to email me
    'Some days, it's just not worth chewing through the restraints.'
    'With sufficient thrust, pigs fly just fine.'
    HVAC/R program for Palm PDA's
    Free demo now available online http://pmilligan.net/palm/
     
    .p.jm@see_my_sig_for_address.com, Dec 10, 2005
    #3
  4. Noon-Air Guest

    "Oscar_Lives" <> wrote in message
    news:Ozsmf.635166$xm3.310501@attbi_s21...
    >
    > <> wrote in message
    > news:...
    >>I am doing computer simulations of HVAC system. I have tried
    >> calculating total pressure using Wright equatiuon and Loeffler
    >> equation; both result in numbers that I think are too low.
    >> Do you know if these formulas are a calculation of total pressure,
    >> static pressure, or velocity pressure.
    >>
    >> Their root is the Darcy-Weisbach friction coefficient equation.
    >>
    >> Am I missing something?
    >> I calculate total pressure of the ducts based on lengths. Then I add
    >> velocity pressure of joints and bends. The sum should be Total
    >> Pressure.
    >>
    >> Also this is a calculation of the furthest hood and all the ducts
    >> required to reach the fan.
    >>
    >> Thank you
    >>

    >
    > Length isn't as important as most folks think.


    Thats not what she said.....
     
    Noon-Air, Dec 10, 2005
    #4
  5. Oscar_Lives Guest

    "Noon-Air" <> wrote in message
    news:D...
    >
    > "Oscar_Lives" <> wrote in message
    > news:Ozsmf.635166$xm3.310501@attbi_s21...
    >>
    >> <> wrote in message
    >> news:...
    >>>I am doing computer simulations of HVAC system. I have tried
    >>> calculating total pressure using Wright equatiuon and Loeffler
    >>> equation; both result in numbers that I think are too low.
    >>> Do you know if these formulas are a calculation of total pressure,
    >>> static pressure, or velocity pressure.
    >>>
    >>> Their root is the Darcy-Weisbach friction coefficient equation.
    >>>
    >>> Am I missing something?
    >>> I calculate total pressure of the ducts based on lengths. Then I add
    >>> velocity pressure of joints and bends. The sum should be Total
    >>> Pressure.
    >>>
    >>> Also this is a calculation of the furthest hood and all the ducts
    >>> required to reach the fan.
    >>>
    >>> Thank you
    >>>

    >>
    >> Length isn't as important as most folks think.

    >
    > Thats not what she said.....
    >'


    She doesn't say anything with that big log in her mouth...
     
    Oscar_Lives, Dec 10, 2005
    #5
  6. Oscar_Lives Guest

    <.p.jm@see_my_sig_for_address.com> wrote in message
    news:...
    > On Sat, 10 Dec 2005 04:11:26 GMT, "Oscar_Lives" <>
    > wrote:
    >
    >>
    >><> wrote in message
    >>news:...
    >>>I am doing computer simulations of HVAC system. I have tried
    >>> calculating total pressure using Wright equatiuon and Loeffler
    >>> equation; both result in numbers that I think are too low.
    >>> Do you know if these formulas are a calculation of total pressure,
    >>> static pressure, or velocity pressure.
    >>>
    >>> Their root is the Darcy-Weisbach friction coefficient equation.
    >>>
    >>> Am I missing something?
    >>> I calculate total pressure of the ducts based on lengths. Then I add
    >>> velocity pressure of joints and bends. The sum should be Total
    >>> Pressure.
    >>>
    >>> Also this is a calculation of the furthest hood and all the ducts
    >>> required to reach the fan.
    >>>
    >>> Thank you
    >>>

    >>
    >>Length isn't as important as most folks think.
    >>

    >
    > Keep telling her that.
    >



    She calls me "Mr. Beer Can"...






    >
    > --
    >
    > Click here every day to feed an animal that needs you today !!!
    >
    > http://www.theanimalrescuesite.com/
    >
    > Paul ( pjm @ pobox . com ) - remove spaces to email me
    > 'Some days, it's just not worth chewing through the restraints.'
    > 'With sufficient thrust, pigs fly just fine.'
    > HVAC/R program for Palm PDA's
    > Free demo now available online http://pmilligan.net/palm/
     
    Oscar_Lives, Dec 10, 2005
    #6
  7. Guest

    Thank you for your response to my hvac question. I am just trying to
    confirm if my calculations for total pressure are correct.

    Coefficcient is a number based on tables (for bends in ducts, joints,
    or expansions) from 0 to 1.

    tp=.0274*DUCT[h].Length*(DUCT[h].Velocity/1000^1.9)/(DUCT[h].Diameter^1.22)+DUCT[h].Coefficient*Math.Sqrt(DUCT[h].Velocity/4005);

    Am I using the correct formula?
     
    , Dec 10, 2005
    #7
  8. Tekkie® Guest

    Oscar_Lives posted for all of us...
    I don't top post - see either inline or at bottom.

    >
    > <> wrote in message
    > news:...
    > >I am doing computer simulations of HVAC system. I have tried
    > > calculating total pressure using Wright equatiuon and Loeffler
    > > equation; both result in numbers that I think are too low.
    > > Do you know if these formulas are a calculation of total pressure,
    > > static pressure, or velocity pressure.
    > >
    > > Their root is the Darcy-Weisbach friction coefficient equation.
    > >
    > > Am I missing something?
    > > I calculate total pressure of the ducts based on lengths. Then I add
    > > velocity pressure of joints and bends. The sum should be Total
    > > Pressure.
    > >
    > > Also this is a calculation of the furthest hood and all the ducts
    > > required to reach the fan.
    > >
    > > Thank you
    > >

    >
    > Length isn't as important as most folks think.
    >
    >
    >

    Said by the man known as "Shorty" I will show the difference!
    --
    My boss said I was dumb and apathetic.
    I said I don't know and I don't care...

    Tekkie
     
    Tekkie®, Dec 11, 2005
    #8
  9. Tekkie® Guest

    Oscar_Lives posted for all of us...
    I don't top post - see either inline or at bottom.

    >
    > <.p.jm@see_my_sig_for_address.com> wrote in message
    > news:...
    > > On Sat, 10 Dec 2005 04:11:26 GMT, "Oscar_Lives" <>
    > > wrote:
    > >
    > >>
    > >><> wrote in message
    > >>news:...
    > >>>I am doing computer simulations of HVAC system. I have tried
    > >>> calculating total pressure using Wright equatiuon and Loeffler
    > >>> equation; both result in numbers that I think are too low.
    > >>> Do you know if these formulas are a calculation of total pressure,
    > >>> static pressure, or velocity pressure.
    > >>>
    > >>> Their root is the Darcy-Weisbach friction coefficient equation.
    > >>>
    > >>> Am I missing something?
    > >>> I calculate total pressure of the ducts based on lengths. Then I add
    > >>> velocity pressure of joints and bends. The sum should be Total
    > >>> Pressure.
    > >>>
    > >>> Also this is a calculation of the furthest hood and all the ducts
    > >>> required to reach the fan.
    > >>>
    > >>> Thank you
    > >>>
    > >>
    > >>Length isn't as important as most folks think.
    > >>

    > >
    > > Keep telling her that.
    > >

    >
    >
    > She calls me "Mr. Beer Can"...
    >
    >

    Dat's Kold!
    --
    My boss said I was dumb and apathetic.
    I said I don't know and I don't care...

    Tekkie
     
    Tekkie®, Dec 11, 2005
    #9
  10. Tekkie® Guest

    Oscar_Lives posted for all of us...
    I don't top post - see either inline or at bottom.

    >
    > "Noon-Air" <> wrote in message
    > news:D...
    > >
    > > "Oscar_Lives" <> wrote in message
    > > news:Ozsmf.635166$xm3.310501@attbi_s21...
    > >>
    > >> <> wrote in message
    > >> news:...
    > >>>I am doing computer simulations of HVAC system. I have tried
    > >>> calculating total pressure using Wright equatiuon and Loeffler
    > >>> equation; both result in numbers that I think are too low.
    > >>> Do you know if these formulas are a calculation of total pressure,
    > >>> static pressure, or velocity pressure.
    > >>>
    > >>> Their root is the Darcy-Weisbach friction coefficient equation.
    > >>>
    > >>> Am I missing something?
    > >>> I calculate total pressure of the ducts based on lengths. Then I add
    > >>> velocity pressure of joints and bends. The sum should be Total
    > >>> Pressure.
    > >>>
    > >>> Also this is a calculation of the furthest hood and all the ducts
    > >>> required to reach the fan.
    > >>>
    > >>> Thank you
    > >>>
    > >>
    > >> Length isn't as important as most folks think.

    > >
    > > Thats not what she said.....
    > >'

    >
    > She doesn't say anything with that big log in her mouth...
    >
    >
    >

    Did she mention my name? I come & go...
    --
    My boss said I was dumb and apathetic.
    I said I don't know and I don't care...

    Tekkie
     
    Tekkie®, Dec 11, 2005
    #10
  11. Guest

    I don't think it is possible to get a straight answer out of this
    forum. I asked a question and was beraded for my stupidity.
     
    , Dec 11, 2005
    #11
  12. On 10 Dec 2005 18:55:17 -0800, "" <>
    wrote:

    >I don't think it is possible to get a straight answer out of this
    >forum. I asked a question and was beraded for my stupidity.


    You asked a stupid home-moaner question that belongs in
    alt.home.repair, not here.

    "Hello Group:

    The day before Thanksgiving I changed the fan speed to HIGH by moving
    the red wire from MEDIUM to HIGH terminal on the motor. Seemed OK till
    Thanksgiving day when the fan died. Turned out to be a bad capacitor.
    Was this just a coincidence or did this hasten the caps demise? It is
    only a year old.
    Thanks,
    Dick"

    You got appropriate answers, first and foremost of which was
    'post in alt.home.repair, not here'.

    Now, if you want to get all pissy about it, I don't really
    give a shit.


    --

    Click here every day to feed an animal that needs you today !!!

    http://www.theanimalrescuesite.com/

    Paul ( pjm @ pobox . com ) - remove spaces to email me
    'Some days, it's just not worth chewing through the restraints.'
    'With sufficient thrust, pigs fly just fine.'
    HVAC/R program for Palm PDA's
    Free demo now available online http://pmilligan.net/palm/
     
    .p.jm@see_my_sig_for_address.com, Dec 11, 2005
    #12
  13. TURTLE Guest

    ..p.jm@see_my_sig_for_address.com wrote:
    > On 10 Dec 2005 18:55:17 -0800, "" <>
    > wrote:
    >
    > >I don't think it is possible to get a straight answer out of this
    > >forum. I asked a question and was beraded for my stupidity.

    >
    > You asked a stupid home-moaner question that belongs in
    > alt.home.repair, not here.
    >
    > "Hello Group:
    >
    > The day before Thanksgiving I changed the fan speed to HIGH by moving
    > the red wire from MEDIUM to HIGH terminal on the motor. Seemed OK till
    > Thanksgiving day when the fan died. Turned out to be a bad capacitor.
    > Was this just a coincidence or did this hasten the caps demise? It is
    > only a year old.
    > Thanks,
    > Dick"
    >
    > You got appropriate answers, first and foremost of which was
    > 'post in alt.home.repair, not here'.
    >
    > Now, if you want to get all pissy about it, I don't really
    > give a shit.
    >


    This is Turtle.

    Earth to Spaceman Paul , Only in your dreams will you every see home
    owners stop coming to alt.hvac. Dream On Cat Man !

    TURTLE
     
    TURTLE, Dec 12, 2005
    #13
  14. Oscar_Lives Guest

    "TURTLE" <> wrote in message
    news:...
    >
    > .p.jm@see_my_sig_for_address.com wrote:
    >> On 10 Dec 2005 18:55:17 -0800, "" <>
    >> wrote:
    >>
    >> >I don't think it is possible to get a straight answer out of this
    >> >forum. I asked a question and was beraded for my stupidity.

    >>
    >> You asked a stupid home-moaner question that belongs in
    >> alt.home.repair, not here.
    >>
    >> "Hello Group:
    >>
    >> The day before Thanksgiving I changed the fan speed to HIGH by moving
    >> the red wire from MEDIUM to HIGH terminal on the motor. Seemed OK till
    >> Thanksgiving day when the fan died. Turned out to be a bad capacitor.
    >> Was this just a coincidence or did this hasten the caps demise? It is
    >> only a year old.
    >> Thanks,
    >> Dick"
    >>
    >> You got appropriate answers, first and foremost of which was
    >> 'post in alt.home.repair, not here'.
    >>
    >> Now, if you want to get all pissy about it, I don't really
    >> give a shit.
    >>

    >
    > This is Turtle.
    >
    > Earth to Spaceman Paul , Only in your dreams will you every see home
    > owners stop coming to alt.hvac. Dream On Cat Man !
    >
    > TURTLE
    >


    Sometimes in life if you don't have your dreams, you may not have anything.

    Also, if you don't have bad times, you won't know what the good times are.
     
    Oscar_Lives, Dec 13, 2005
    #14
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