I am struggling to find the formula to calculate how long it will take to vaporize a quantity of water.?

Question

Its 70g of water if that helps

Answer 1

The first answer tells you how to calculate the amount of energy you need to add to the water to raise its temperature (you didn't mention the starting temperature) to the boiling point. Add to that the heat of vaporization mentioned in the second answer, and you get the amount of heat you need to add to the water. Next you need to know how fast you can transfer heat to the water. Knowing those, you can calculate the time.

Answer 2

First, to heat the water you need 4.186 j/ºC/g.

Say, from 25ºC to 100ºC = 75 x 70 x 4.186 = 21.977 kJ

Then, to vaporise it, Latent heat of vaporisation of water =
2260 J/g

You have 70 g. This is 70 x 2260 = 158.2 kJ of heat.

Total heat to this point = 158.2 kJ + 21.977 kJ = 180.177 kJ or 1.802 MJ

How long this would take to vaporise is not known but, if you turn up the gas and increase the boiling rate, it will vaporise faster.

(By the way Zelda, 1 Btu is the heat required to raise 1 POUND of water by 1 ºF).

Answer 3

1 btu is defined as heating 1 cubic foot of water 1 degree. Therefore if you know the qty of water, and how many degrees you need to raise it, you can calculate the # of BTU's required. Also depends on your heat source, and number of BTU's produced.