# Calculate work needed to evaporate water

1. Oct 23, 2011

### pikiche

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. Oct 23, 2011

### edgepflow

The energy required is the mass of water multiplied by the laten heat of vaporization:

Q = m $h_{fg}$

Q = energy required
m = mass of water
$h_{fg}$ = latent heat of vaporization

If you want to estimate how long it will take to evaporate naturally, search for "swimming pool evaporation equation."

3. Oct 23, 2011

### phinds

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.

4. Oct 23, 2011

### edgepflow

The sensible heat can be included as follows:

q = m $h_{fg}$ + m $c_{p}$$\Delta$T

cp = specific heat
$\Delta$T = temperature change = 212 F - 75F

5. Oct 23, 2011

### pikiche

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?