calculate work needed to evaporate water


by pikiche
Tags: energy, enthalpy change, evaporation, heat, work
pikiche
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#1
Oct23-11, 12:32 AM
P: 3
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
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edgepflow
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#2
Oct23-11, 11:13 AM
P: 688
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."
phinds
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#3
Oct23-11, 11:20 AM
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Quote Quote by edgepflow View Post
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."
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.

edgepflow
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#4
Oct23-11, 01:46 PM
P: 688

calculate work needed to evaporate water


Quote Quote by phinds View Post
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.
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
pikiche
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#5
Oct23-11, 05:14 PM
P: 3
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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