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Thread: heating elements

  1. #1
    Join Date
    Mar 2008
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    ryde
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    heating elements

    Hi newbie here
    I've almost finished building a plant to make my biodiesel- and have decided to go with electric heating elements- the people at Grimwood heating have said hotwater elements won't cut it and sell a biodiesel kit( I haven't seen it) has anyone got experience with using hot w elements.Any help appreciated- Adrian

  2. #2
    Join Date
    Sep 2005
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    Re: heating elements

    The issue with hot water heating elements is that oil will burn if too the element has a very high heat density (W/sq cm), if that is the correct terminology, resulting in very high element surface temperatures. Water does not have this issue.

    It is possible to reduce the heat density of heating elements at the design stage, where a 1KW element for oil has twice or more surface area than a 1KW heating element for water.

    IF you can buy 2, 2KW water heating elements and operate them in series, you should be able to halve the power density of these elements and provide the same heating to the oil as a 1KW water heating element, with reduced carbonising of oil on the elements.

    You could also use a "simmerstat" (which is a controller for electric stove elements). By using settings below 5 (on a scale of 10) you should easily keep the element temperature below the charring temperature of the oil., while the element is immersed in the oil.

    I hope this helps,
    Tony

  3. #3
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    Mar 2008
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    ryde
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    12

    Re: heating elements

    Hi Tony
    I feel like a goose- the oil burning never occurred to me- Doh!Thanks- I will investigate their 'Kit'- Adrian

  4. #4
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    Sep 2005
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    Re: heating elements

    To most people, an element is an element, nothing more.

    By using a simmerstat on a higher wattage heating element, and limiting the highest setting to 50% of full power, you can achieve a similar result as using an element half the power, but with a power density of half of the one used.

    ie, Run a 2KW element at 1KW and you have the same result as a 1 KW element with lower power density.

    Hope this helps,
    Tony

  5. #5
    Join Date
    Jul 2007
    Location
    Canberra, ACT, Australia
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    333

    Re: heating elements

    Tony, can you please say that again slowly and in plain english. I'm interested but I'm having trouble following the bouncing ball. Is a simmerstat available for a HWS? Some not so accurate figures to help with the understanding would be appreciated, especially WRT your ie.

    Thanks.
    Maverick
    Canberra

  6. #6
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    Re: heating elements

    A simmerstat is a bimetal spring which is heated when the simmerstat is on. When the spring gets hot, it opens the contacts, turning off the load (and the heating element for the bimetal spring) The bimetal spring cools down, closing the contacts, allowing power to flow to the load and the bimetal spring heating element.
    By varying spring pressure (a cam on the rotating control adds tension to the spring), it can be used as a variable control for heating elements. These are the type of control electric stoves use to regulate element (burner) heat.

    By running a high power element at low power (using a Simmerstat or other device), the power density is reduced, and thus the maximum temperatue the element achieves when immersed in a liquid (eg oil) is also reduced.
    If the simmerstat is operated at full on setting, the full power of the element becomes available (and the high power density & surface temperatures of the element also), so this control should be set and preferrably sealed to prevent adjusting of the control by others.

    I hope this helps exp[lain what I was trying to say

  7. #7
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    Canberra, ACT, Australia
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    Re: heating elements

    Thanks Tony, I understand the simmerstat principle of operation but I'm still having trouble working out how it is preventing a high power heating element, say 3600 watts, from acheiving it's full 3600 watt power draw.

    Is the bi-metalic strip positioned on the heater element, thus sensing heater element temp or is it sensing oil temp? If the latter then the bi-metalic strip will allow the heater element to draw the full 3600 watts untill the bi-metalic strip (oil) reaches the preset temp and then switch in and out to maintain that temp, but every time it switches in the heater can again draw the full 3600 watts.

    Am I on the right track? I still can't see how a 2kw heater element can be turned into a 1kw heater element simply by introducing a simmerstat unless the simmerstat is sensing the heater element temperature directly and not via the oil.

    I am interested as I have a 3600 watt heater element that I would like to only draw the power of a 2400 watt heater element.
    Maverick
    Canberra

  8. #8
    Join Date
    Nov 2007
    Location
    South Coast, NSW
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    870

    Re: heating elements

    grimwoods kit is quite good value. he has helped many fellow sydney biodieselers out. I myself am buying one in a month or so. goodluck and welcome to the forum.
    Cheers
    Nick.
    Harold 2002 Toyota Landcruiser 105 series. 4.2lt turbo glide turbo, Too lazy to make bio nowdays times money. 3'' lift.

    Roidio 2001 Holden Rodeo 4x4 2.8L TD. 2.5" exhaust sytem, H/E shower system. 4" Lift, Airbags, And lots of fruit, B100 for 55,000 . SOLD

    Elsa 1983 Mercedes-Benz W123 300D. Still The Fastest Merc in Oz, Self built and Female proofed. COUSINS NOW

  9. #9
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    Re: heating elements

    What the simmerstat is doing, is "pulse width modulating" the power applied to the heating element. At a 50% pulse width, half the power is available. The pulse width is around 5 - 30 seconds.
    So at 50%, the full power is applied for 50% iof the time and off for 50% of the time.

  10. #10
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    Re: heating elements

    Quote Originally Posted by maverick_sr71 View Post
    Thanks Tony, I understand the simmerstat principle of operation but I'm still having trouble working out how it is preventing a high power heating element, say 3600 watts, from acheiving it's full 3600 watt power draw.

    Is the bi-metalic strip positioned on the heater element, thus sensing heater element temp or is it sensing oil temp? If the latter then the bi-metalic strip will allow the heater element to draw the full 3600 watts untill the bi-metalic strip (oil) reaches the preset temp and then switch in and out to maintain that temp, but every time it switches in the heater can again draw the full 3600 watts.

    Am I on the right track? I still can't see how a 2kw heater element can be turned into a 1kw heater element simply by introducing a simmerstat unless the simmerstat is sensing the heater element temperature directly and not via the oil.

    I am interested as I have a 3600 watt heater element that I would like to only draw the power of a 2400 watt heater element.
    The bi-metalic strip is not in the oil nor at the heating element, if it were it would be a thermostat. The bi-metalic strip heats up because it has 3600 w passing through it so it deflects an opens the circuit, then cools and returns to original position and closes the circuit again. As Tony explains, the adjustment allows you to modulate the pulse width so toget 2400w you will need 66% on and 34% off (by trial and error). You will also need a thermostat, in series, to control the temperature.

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