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Glycol Derate

Jims
Jims Member Posts: 1
in THE MAIN WALL
Altitude usually requires a boiler outpt derate of 4%per 1000ft of altitude above 2000ft. Glycol heat transfer rate usually requires a derate of about 1/4% per 1% of Prop glycol. We normally see boiler manufacturers derating for combustion efficieny only. If the job site is at 6000 ft elevation and the 400,000 input boiler combustion efficiency is 85% and we have a 30% Prop glycol mix is the total boiler output = 400,000x(.85 effcy) x(.84Alt) x(1/4x30)/100 = 264,180 ?

Comments

  • ALH_4
    ALH_4 Member Posts: 1,790
    Glycol

    You would not derate the boiler for glycol. That is accounted for when you up-size the circulator to accommodate the flow rate needed for the glycol concentration required. The more viscous fluid will probably cause a slightly thicker boundary layer inside the boiler heat exchanger, although the higher velocity due to up-size of the circ would make it thinner. Accounting for this with any accuracy would be very difficult.

    Short answer: The de-rating has been accounted for in the circulator sizing.
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