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Calculate work needed to evaporate water

  1. Oct 23, 2011 #1
    how would you calculate the work needed to evaporate water from washed clothes, if the clothes r in a well isolated room with temperature of 75F
    help plzzzz
  2. jcsd
  3. Oct 23, 2011 #2
    The energy required is the mass of water multiplied by the laten heat of vaporization:

    Q = m [itex]h_{fg}[/itex]

    Q = energy required
    m = mass of water
    [itex]h_{fg}[/itex] = latent heat of vaporization

    If you want to estimate how long it will take to evaporate naturally, search for "swimming pool evaporation equation."
  4. Oct 23, 2011 #3


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    No, he said it starts off at 75 degrees. Surely that has to be taken into account. I mean, it CAN'T take the same amount of energy to evaporate water at 1 degree above freezing as to do it to water at 1 degree below boiling.
  5. Oct 23, 2011 #4
    The sensible heat can be included as follows:

    q = m [itex]h_{fg}[/itex] + m [itex]c_{p}[/itex][itex] \Delta[/itex]T

    cp = specific heat
    [itex]\Delta[/itex]T = temperature change = 212 F - 75F
  6. Oct 23, 2011 #5
    thank you for the reply guys, see what im trying to do is actually calculate how much money would u save from line drying clothes vs using an electric dryer. knowing that u have an ac/ heater at the houseto keep the temperature at 75. so i was thinking that after calculating the heat to evaporate the water from the clothes wouldnt be the same amount of energy that the ac/heater has to apply to maintain the temperature at 75?
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