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Thread: Heat Transfer on Biogas Pipeline

  1. #1
    Associate Engineer
    Join Date
    Oct 2013
    Posts
    1

    Heat Transfer on Biogas Pipeline

    I am looking for some direction in the equations required to calculate the heat energy required to heat gas in a pipeline from 20 to 25 degrees Celsius. The reason is to calculate what the best means of heat exchange would be to surround the pipe that would allow the bio gas to heat up to a minimum of 25 degrees before it enters a dehumdifier unit. Before I get into this I first need to calculate the heat capacity required to raise the temperature of the gas internally before I look to find a means to create this heat.

  2. #2
    Lead Engineer
    Join Date
    Aug 2013
    Location
    Houston TX USA
    Posts
    421
    The calculation is relatively straight forward once you have the basic data available. (I apologize for the use of english measurements)

    The first critical data required is the Sp Specific Heat (BTU/lb/degreeF) for your biogas, which depends upon the actual composition of the gas. For pure gases this Sp value is available in tables or its value for pure gas mixtures can be determined by calculation based upon the mole wt percentages of each component gas in the mixture. I have no background with biogases so I don't know if this data is available for your specific biogas or for the individual biogases in your has composition. If not, it may be necessary to have a laboratory calorimeter test performed to determine this critical data.

    Once you have the Sp for your biogas composition then, assuming based upon your description this is a continuous process with flowing gas in the pipe, you will need to determine the mass flow rate in lbs/hr of your process.

    With these values known, then the equation for a constant pressure process of heating in BTU's/Hr is: Q = Sp * lbs/hr * (to - ti)
    where: Q is the required input heat in BTU/hr,
    Sp is the Specific heat value for your gas
    lbs/hr is the gas mass flow at the pipe section average gas temperature and pressure,
    (to - ti) is the differential temperaure in degrees F between your desired gas output temperature and the minimum input temperature of your gas

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