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How does a heat exchanger truck mount compare to fuel fired by BTU calculations?

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  • How does a heat exchanger truck mount compare to fuel fired by BTU calculations?

    How does a heat exchanger truck mount compare to fuel fired by BTU calculations?
    CFM X 1.08 X tRise = Btu/hr

    General information follows.

    That factor is based on standard conditions which are at sea level and A standard humidity level which i do not remember off hand. As altitude increases the factor decreases. At 2100 feet it is roughly 1.0.
    The humidity also affects this number. Generally the greater the humidity the greater the factor.*

    1.08 Will be good enough for most applications though.

    I'll give an example of the use:

    Suppose the room temperature is 65.
    We have a 1200 CFM blower. We measure an output temperature of 100.
    100 - 65 = 35 temp Rise.

    Now we have all the numbers to get our BUT/hr.

    1200 x 1.08 X 35 = 45,360 btu/hr

    Some truck mounts only heat of the engine exhaust. Say for example the 25 hp engine is 730cc displacement or 44.547 cubic inches, or .02578 cubic feet. Engine turns at 3200 rpm under a load or displaces 82.50 cubic feet of air.
    Temperature rise up to 1100 degree above starting temperature.
    82.5 Cfm X 1.08 X 1100 = 98,010 BTU / hour
    This means that for every 1 hp of engine size you have about 3,920 BTU of heat.
    or for every cc of engine displacement you get 134.26 BTU of heat.

    Some use vacuum blower exhaust to supplement the heat.
    a positive vacuum pump, with a wand on the floor displaces about half of the air that it can at open flow but this is when it produces heat. We have seen some vacuum pumps produce up to 240 degree F air and again taking an average vacuum pump size of Tuthill 4005, or Denver 4MR, or Roots 45 they move a max un-restricted air flow of 425 cfm and with the wand on the floor 212 cfm but now the temperature rise is 165 degrees.
    Formula is 212 cfm X 1.08 X 165 degrees = 37,778 BTU /hour
    Vacuum Blowers product 178.2 BTU per cfm with the wand on the floor and have of this in the air (89.1 BTU per cfm)

    Some water cooled truck mount absorb energy from the hot radiator water and even from the oil cooler.
    One*BTU*is the amount of heat energy required to raise one pound of*water*by 1ºF. Water*weighs 8.33 pounds per*gallon*so we can calculate that one*gallon*of*water requires 8.33*BTU*to raise the temperature 1ºF So now we would have to know the in and outbound temperatures of the heat exchanger at 1 gpm.
    I have seen one hundred degree F rise on a liquid to liquid heat exchanger and even a 135 degree rise on oil to water heat exchangers. So here is some math.
    8.33 X 100 degree rise X 60 minutes = 49,980 BTU per hour
    8.33 X 135 degree rise X 60 minutes = 67,473 BTU per hour.

    Also electric 2000 watt in line water heaters offer about 9166 BTU of heat

    In summary larger engines and vacuum pumps produce more BTU’s and hold up better during faster, high flow rates in pressure washing, dual wanding, and tile cleaning. The more heat exchangers use the better the machine will hold up in the high flow applications. Each truck mount design is different in how many of these heat exchangers or used and even how the water flows through them. We have even seen engine abeyant heat exchangers where the hot air that flows through the air cooled cylinder fins passes by a mini air to water radiator. The real test is using your carpet cleaning wand and lay on the trigger full time to see how well the machine holds up. The total amount of heat exchanger surface area and closeness to the heat source all play factors in actuall numbers.

    Donald Cook

    You also might want to read post at
    Truck Mount Comparison Chart by performance and dollar spent

    Water molecule vibration for cleaning

    BTU comparison chart on truckmounts is located at
    Last edited by Donald; November 4, 2017, 05:48 AM.