What happens when you wring out a washcloth in space [video]

Post by 4ad » Sun, Apr 21, 2013, 4:40 PM UTC

spinonethird wrote: post #42

4ad wrote: post #40

Earlier quoted context omitted.

The water won't have less than 200K when you start the experiment though (else you won't have a wet cloth but a frozen cloth), so all the water will boil off almost instantly.

It would start boiling but this very fact would very quickly cool it off to freezing point: water has a very high heat of vaporization.

    mc dT = λv dm

    dT = λv/(mc) dm | ∫

    Tƒ - T₀ = λv/c ∫ (dm/m) 
        = λv/c (ln mƒ' - ln m₀) =
        = λv/c ln (mƒ'/m₀)

    ln (mƒ'/m₀) = c/λv (Tƒ - T₀)

    mƒ'/ m₀ = exp[c/λv (Tƒ - T₀)]

    mƒ'/m₀ = exp[ 4192J/(kg K) * 1/(2257 * 10^3J/kg) * (-100K)] =
        = exp[ -4192/2257 * 10^-3 * 10^2 ] = 
        = exp[ -4192/2257 * 10^-1 ] ≈
        ≈ 83%.

    mƒ = mƒ' - mv

    |Qced| = Qabs

    mƒ λc = mv λv

    mƒ = λv/λc mv

    mƒ = λv/λc (mƒ' - mƒ) = λv/λc mƒ' - λv/λc mƒ

    mƒ (1 + λv/λc) = λv/λc mƒ'

    mƒ = λc/(λc + λv) * λv/λc mƒ' =
        = λv/(λc + λv) mƒ'

    mƒ/m₀ = 2257kJ/kg * 1/(2257kJ/kg + 335kJ/kg) * 0.83 ≈
        ≈ 2257/2592 * 0.83 ≈
        ≈ 72%

Post by kvprashant » Mon, Apr 22, 2013, 12:45 PM UTC

4ad wrote: post #111

spinonethird wrote: post #42

Earlier quoted context omitted.

It would start boiling but this very fact would very quickly cool it off to freezing point: water has a very high heat of vaporization.

~72% of the initial water would freeze as ice. Phase #1, water cooling and boiling: mc dT = λv dm dT = λv/(mc) dm | ∫ Tƒ - T₀ = λv/c ∫ (dm/m) = λv/c (ln mƒ' - ln m₀) = = λv/c ln (mƒ'/m₀) ln (mƒ'/m₀) = c/λv (Tƒ - T₀) mƒ'/ m₀ = exp[c/λv (Tƒ - T₀)] mƒ'/m₀ = exp[ 4192J/(kg K) * 1/(2257 * 10^3J/kg) * (-100K)] = = exp[ -4192/2257 * 10^-3 * 10^2 ] = = exp[ -4192/2257 * 10^-1 ] ≈ ≈ 83%. Phase #2, water freezing, remaining wa…