Why does wort being boiled take longer to come to the boil the higher the temperature of the wort gets

For example: I’m getting 30 liters of wort from approximately 67C to 100C. the time. It takes about 5 mins to get to the low to mid 90s but then takes at least three times that to get to the boil.

This happen both when I do or don’t watch it boil.

Trevtaowillgetyounowhere said:

Why does wort being boiled take longer to come to the boil the higher the temperature of the wort gets

For example: I’m getting 30 liters of wort from approximately 67C to 100C. the time. It takes about 5 mins to get to the low to mid 90s but then takes at least three times that to get to the boil.

This happen both when I do or don’t watch it boil.

Latent Heat of Vapourisation.

https://en.wikipedia.org/wiki/Enthalpy_of_vaporization

Once a liquid gets up to its boiling point it takes an extra kick of energy to make the conversion from a liquid to a gas.

You’re entering a phase change state and that takes a lot of additional energy.

party_pants said:

Trevtaowillgetyounowhere said:

Why does wort being boiled take longer to come to the boil the higher the temperature of the wort gets

For example: I’m getting 30 liters of wort from approximately 67C to 100C. the time. It takes about 5 mins to get to the low to mid 90s but then takes at least three times that to get to the boil.

This happen both when I do or don’t watch it boil.

Latent Heat of Vapourisation.

https://en.wikipedia.org/wiki/Enthalpy_of_vaporization

Once a liquid gets up to its boiling point it takes an extra kick of energy to make the conversion from a liquid to a gas.

indeed, alongside the increased evaporative losses, losses by conduction and radiation also increase with the temperature differential relative to surroundings

from the Wikipedia

The enthalpy of vaporization can be written as

ok got it its magic.

but yeah ok so it simply takes more energy to go from liquid to steam than just heating the liquid from x to y C

Today I learned something I never even noticed or suspected was a thing in over 50 years of living.

Thanks

side question. does the opposite thing happen when you make a liquid turn into a solid? ie. less energy the colder it gets?

Trevtaowillgetyounowhere said:

but yeah ok so it simply takes more energy to go from liquid to steam than just heating the liquid from x to y C

Today I learned something I never even noticed or suspected was a thing in over 50 years of living.

Yeah the phase-change thing can consume a fair bit of energy.
For example part of the cooling system on the Apollo lunar rover used wax. When it got hot enough it’d melt and thus absorb a lot of heat from the electronics, then flow somewhere else to cool down, thus dumping a lot of heat to do so.
Some car engines use this effect in some small areas around the head gasket – The water is meant to be very near boiling as it transits the head gasket between the head and engine block, and so when it very briefly turns to steam it soaks up a lot of heat energy around that part of the engine.

source address in image

Trevtaowillgetyounowhere said:

side question. does the opposite thing happen when you make a liquid turn into a solid? ie. less energy the colder it gets?

Yes. This is called the Latent Heat of Fusion, same sort of deal changing from solid to liquid. You can cool water to 0C without it freezing, you have to add a bit more cooling effort to make it turn to ice.

The process of the water turning into steam also works in reverse. When steam condenses back into water it will release heat. This has all sorts of useful applications. Also, non-useful things, it is what drives the formation of tropical cyclone storms.

Trevtaowillgetyounowhere said:

from the Wikipedia

The enthalpy of vaporization can be written as

ok got it its magic.

but yeah ok so it simply takes more energy to go from liquid to steam than just heating the liquid from x to y C

Today I learned something I never even noticed or suspected was a thing in over 50 years of living.

Thanks

side question. does the opposite thing happen when you make a liquid turn into a solid? ie. less energy the colder it gets?

Trev, the above graph shows the energy required for the state changes.

To go from ice to water requires 333 J/g.

To go from water to steam requires 2256 J/g.

Note that going to other way energy is released, so water vapour turning back to water releases 2256 J/g of energy as heat.

SCIENCE said:

source address in image

Air conditioner…

sibeen said:

Trevtaowillgetyounowhere said:

from the Wikipedia

The enthalpy of vaporization can be written as

ok got it its magic.

but yeah ok so it simply takes more energy to go from liquid to steam than just heating the liquid from x to y C

Today I learned something I never even noticed or suspected was a thing in over 50 years of living.

Thanks

side question. does the opposite thing happen when you make a liquid turn into a solid? ie. less energy the colder it gets?

Trev, the above graph shows the energy required for the state changes.

To go from ice to water requires 333 J/g.

To go from water to steam requires 2256 J/g.

Note that going to other way energy is released, so water vapour turning back to water releases 2256 J/g of energy as heat.

ahh i guess that makes sense now . Kind of how fridges and air conditioner work. never connected that before.

You know I’ve never minded being the guy who gets the C grades in the smart kids class. You always learn new things and you get to call people NEEEEEEEEEERDS a lot

> This happen both when I do or don’t watch it boil.

LOL.