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Water heating transfer

  1. Oct 30, 2012 #1
    Hello,

    its my first post here, I had physics long time ago and now composing a system which need some (only probably) calculation.

    I have a water system containing 200 litres of water, its all in tube system which is vertically stacked, each tube have capacity of 10 litres, so theres 20 glass (thickness 3mm, diameter 50mm, length 150cm (60 inches)) tubes with water, connected with each other so it can circulate thans to heat in the bottom. Theres a condition to hold temperature of the water between 30-35°C (86-95F).
    I am planning to do it with quartz infrared heater placed underneath (about at least 30 cm under first tube in order to prevent overheating of first tubes near it, there will be life in it!), the quartz heater will be one rod of approx length 50 inches so it nearly covers length of tubes.

    The question is, how much power do I need to hold temperature?
    In aqaurium, its said that 300W is enough for 200litres, but aquarium heaters are placed in the water, in our case we are using air as a heater medium. I am pretending the target is somewhere between 300 and 700Watts.

    If its difficult to imagine whole system I will add picture of it.

    Thanks for insights,
    V.
     
  2. jcsd
  3. Oct 30, 2012 #2

    sophiecentaur

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    Hello and welcome to PF

    The temperature that a system will settle down to ('equilibrium temperature') will be reached when the rate of heat supplied is balanced by the rate that heat is lost. So you haven't told us enough about your system for an answer yet.

    If it is all in an insulated box then a very few watts will be needed, if outdoors in winter, you will need a lot. Is it in a normal room? How fast do you want the system to warm up at switch-on? Do you plan to circulate water around the tubes? That would ensure that the temperatures are all kept the same as the radiant heat is bound to heat the nearest tubes much more than the furthest tubes.
     
  4. Oct 30, 2012 #3
    thanks for pointing it up, the system will not be closed and it will be placed indoors, so lets say in room temperature about 20°C.
    No need for fast heating, heater just simulate natural conditions and temperature will be cycled in 12/12 or 16/8 hours on/off when shut down temperature will drop to room temperature, so it wont matter if heating process to 35°C will take one hour or two hours, its important to hold it then for following 12 hours or so..
    The water should circulate at a small rate, that was a hidden second question, if every tube is connected with upper one and top tube leads down to bottom one, will the water circulate on its own (if the heater will be nearer to connection with upper tube)?

    I am including a simplified picture how I mean it (sorry for my drawing skills, it was done in hurry in ms paint:), please note there will be at least 20 tubes.

    V.
     

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