In reply to  Jed Rothwell's message of Sun, 23 Jan 2011 15:29:03 -0500:
...but you are not actually producing wet steam. You are producing dry steam
that then condenses to some extent upon contact with the cool air. "Real" wet
steam might be produced in a situation where the flow of steam was very rapid
and it passed across a wet surface so that water could be entrained in the
steam, e.g. a narrow pipe rather than a large open surface. In that situation it
could transport water droplets that had never been vaporized.

>In the discussion her:
>Someone named Guest insists that it is possible to boil 8.8 kg of water in
>30 min with 700 W input. He give a set of reasons similar to the ones cited
>here by Horace Heffner; i.e. the enthalpy of wet steam is much lower than
>dry steam. If that were true, it would be possible to boil away water much
>faster than the textbook heat of vaporization of water indicates, with a
>method that produces wet steam.
>I tested this assertion by boiling 500 ml of water in an electric frying
>pan. I uploaded the results along with a photo.
>Boiling Water Test
>See attached photo [NOT HERE -- AT WEB SITE] of frying pan with boiling
>water and orange indicator light and control set for top temperature. 500 ml
>cup in foreground. Data:
>2:11 Power on to highest level 425°F (218°C), nominal 1.5 kW
>2:14 Orange indicator shows terminal temperature reached
>2:14 500 ml room temperature water added
>2:15 Indicator light on again. Pan partly covered to bring to boil
>2:16 Boiling
>2:17 Pot top removed
>2:17 Lots of visible vapor, just above water. Very wet steam. Condensation
>on top of pan.
>2:21 Not too hot to hand 30 cm above pot. Tissues on table next to pot not
>2:25 Take photo
>2:29 Indicator light on steady the whole time; power is continuous
>2:32 Tissues remain dry; water is not falling back into pot.
>2:32 Close to bottom
>2:36 Dry!
>FIRST PHASE Water from room temperature to boiling took 2 min
>2 min * 60 s =120 s
>120 s * 1,500 W = 180,000 J = 180 kJ
>Heat capacity of water (4.2 kJ/kgK) and
>Temperature change nominally 80°C
>Energy to bring water to 100°C: 80°C*4.2*0.5 kg = 168 kJ
>~ 93% heat recovery but probably less because pot was pre-heated to 218°C
>SECOND PHASE 20 min to boil dry
>20 min * 60 s = 1,200 s
>1,200 s * 1,500 W = 1,800,000 J = 1,800 kJ
>Heat of vaporization of water (2260 kJ/kg)
>Energy to vaporize 0.5 kg of water: 2260*0.5 = 1,130 kJ
>It takes much more than the expected amount of heat to boil the water
>because the pot poorly insulated, heat is lost from the bottom and sides of
>the pot. Note that the Rossi device is also is also poorly insulated and
>loses heat to other paths. The flowing water does not recover all the heat.
>If this were dry steam, heat recovery would be 63% (1130/1800).
>CONCLUSION Boiling water in a pot to produce wet steam gives a value
>reasonably close to the textbook heat of vaporization of water (2260 kJ/kg).
>It is not possible to boil away water with wet steam in far less time than
>predicted by the heat of vaporization.
>Website is
>right, and Guest is wrong.

Robin van Spaandonk

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