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I want to heat up my room, would a fan towards the radiator work?

  1. Dec 7, 2011 #1

    Might sound like a homework problem but since it isnt I posted it here.

    I currently live in a small 22m^2 student apartment. Heating is included in the rent, in the shape of a basic water radiator located below the window towards the wall (dont worry, there is nothing standing towards it preventing the air from circulating). Me, and several others do however find that during the winter it gets too cold, the landlords reply is that we should put on a second pullover...

    Adding an electrical radiator would work, but since the water radiator is designed to only keep the surrounding temperature around the radiator at a certain level, me increasing it would force me to pay the entire heating bill (plus the one for the water radiator which is the same for everyone, included in the rent).

    As Im studying towards a msc I have had a few courses in heat transfer, thermodynamics etc.

    I know that increasing the air flow increases the heat transfer coefficient etc. Would it be possible to fool the water radiator to believe that the room is colder than it actually is by placing a fan that blows air through the water radiator (it doesnt really look like this, but close enough http://tinyurl.com/cz6uqtn as you see it is "open" on the sides allowing me to blow air "through" it). By this I would force the radiator to put out more heat.

    1, The warm air would spread better around the room which is good (on the landlords HP it says that the radiator might experience the room temperature warmer than it is if the air circulation is bad)

    2, I would replace the warm air from inside the radiator faster with colder air fooling the settings of the radiator (I have no extensive experience with radiators but one would think that they are designed to "believe" that the room temperature is X when the temperature inside the radiator is X+Y)

    3, The higher heat transfer coefficient would remove heat from the radiator itself faster

    Possible Problem: I do not know where the "sensors" are located

    Question: What do you think? Will a basic fan (think the big ones you have on your desktop in the summers) make any difference? Just a few degrees or even a single degree would be wonderful.

    The electricity cost for keeping the fan running is irrelevant.

    Thank you for reading, hopefully someone has encountered a similar problem or perhaps knows anyway. In worst case I'll take it up with the professor :D
  2. jcsd
  3. Dec 7, 2011 #2


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    Quite often, a hot water radiator has a valve that you manually turn to adjust the amount of hot water flowing through it. That little knob might be your manual valve.
    Others are regulated by an electronic valve connected to a thermostat on the wall.
    And then there are some that have no regulation at all for individual rooms or dwellings.
    I have never heard of a radiator "itself" sensing the room temperature, but I could be mistaken - it just seems odd for the radiator to have control like that ( the radiator doesn't know what the temperature of the room is 10 feet away).

    On top of that, the hot water flowing through the radiator can be set at a certain temperature at source, meaning at the hot water tank down in the basement.
    If all the tennants are feeling cold in the building, perhaps the landlord has it set too low.
    Or the pump is old and not pumping enough water through the system.
    And then again some are gravity fed, with the hot water rising and colder water falling to provide the circulation.

    If you blow air at the radiator you will increase convective heat transfer and for that reason your dwelling should become warmer. Make sure you have curtains on your windows to retain the heat within your living space.
    Last edited: Dec 7, 2011
  4. Dec 7, 2011 #3
    sure, a small fan moving air across the existing radiator will extract some additional heat as long as the radiator is warmer than the air....of course the moving air, a draft, might offset that a bit. And you can add an electric heater at a distance from the existing radiator so the room is heated more evenly....A plastic temporary "stick on" plastic cover over the window can also substantially decrease heat loss if the window is single pane and drafty.
  5. Dec 7, 2011 #4


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    Yes, a fan gently blowing on a rad should heat your room better. Not just because it will circulate the heat away from the rad better, but also because the general air circulation will discourage the warm air from pooling at the ceiling.

    I have rads and, if there hasn't been a lot of activity in my living room for a while, it can be significantly warmer at standing height than at sitting height, and moreso at ankle height.
  6. Dec 7, 2011 #5
    Thank you for your reply, you are right about the manual valve. That is however left on max all year around. I do have the curtains down 24/7. I hope the convective heat transfer will make a difference, I plan to buy a fan in a few days to try.

    On the homepage it says they have a central heating system, and they shut it off during the summer. It also says that the thermostat of the radiator might feel that the room is warmer than it is, if you for instance but a blanket on the radiator and thereby disturbing the air flow, and then it could lower the output heat. That is what i meant by "sensing"
  7. Dec 7, 2011 #6


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    Also, there should be a small bleed valve screw located somewhere on the radiator that you can turn with a screw driver or small tool to let out entrained air. Air in the system hampers its performance. Turn the screw a tiny bit until you hear some hissing or you see water coming out ( at which point you turn closed again ). I emphasize turn only tiny bit.
  8. Dec 7, 2011 #7


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    Bleeding the rad is always a good idea. This is the most common and most easily remedial problem with rads.

    You might want to put a cup under that. After a summer, my rads can gain quite a bit of air. It takes time for the air to bleed out. You have to open the valve all the way. And you will certainly not shut it off in time to prevent some grey, smelly water spitting out onto your floor.
  9. Dec 7, 2011 #8


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    A cieling fan works wonders.
  10. Dec 7, 2011 #9
    Thank you all for some really fast and good advice!

    I tried bleeding the radiator but water came instantly so probably not much air. I believe the radiator and the windows etc are quite new since the house is from 2005.

    It all boils down to the radiator being able to sense the temperature (if it does or not).
    If it does, I believe insulation efforts will only make the landlord happy since the radiator will put out less. As they hint on the homepage, this should be the case and I will try it out with the fan! Hopefully the above mentioned draft wont ruin it.

    If not, its all insulation (and avoid warm air pooling at the ceiling etc.).

    About the electric heater on the other side of the room I think my room might be too small? (22m^2) for that to have the desired effect.

    When I try this out Ill post the results
  11. Dec 7, 2011 #10


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    You could use a fan, but first

    1. Check there are no currents of cold air coming from the window. (If you lick your finger, that makes a very sensitive cold-air detector!) If the curtains are closed, make sure they are blocking off the cold air flow, not just chanelling it down to ground level.

    2. If there is some cold air coming under the door, block that off as well.

    3. Put a heat shield between the radiator and the wall, if there isn't one there already, You can probably buy these for "rip-off" prices from DIY stores, but a sheet of thick cardboard (cut from a big cardboard box) covered with kitchen foil on the radiator side works just as well. Otherwise, half the heat from the radiator is just warming up the outside wall of your room. You will need to figure out the right size to fit between the brackets holding the radiator onto the wall, or whatever.
  12. Dec 7, 2011 #11


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    Yes, we have ceiling fans. We don't always have them on though; they can be noisy.
  13. Dec 7, 2011 #12


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    The rad does not sense temperature. There's a thermostat somewhere in the house - it might not be in your part.

    No. Insulation will certainly help you. At worst it will not hurt.
  14. Dec 7, 2011 #13
    Let me offer my 2 cents on how to make your room appear much warmer:

    Get some gloves and get to a heavybag at your gym. Throw 100 hard punches at the bag as fast as you can then rest for a little while. While you are resting, you can go to a speedbag. Then, repeat for 12 rounds, giving you 1200 heavybag punches at the end of the day. Do this every day you get the chance.

    The room will appear much warmer for you.
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