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Blog: Boiling in Space

A New Thermodynamics

By Kent W. Mayhew

 

  If I was to say that: ďboiling in a closed rigid (isometric) system requires increases the systemís ability to do workĒ, would I be right. It all depends upon how one defines the systems. It would be best if one considered the boiling water as System 1, and rest of the isometric system as its surrounding System 2. Therefore boiling System 1 increases the potential of surrounding System 2 to do work [VdP(system2)].  

 

Boiling in Space

Consider the boiling of water in the space lab orbiting Earth. There is no gravity thus vaporization does not involve work being passed onto the atmosphere i.e. lost work. Therefore, boiling in space should require less energy than here on Earth.

Investigating further: The space lab is in an isometric (closed rigid) system hence the work (or potential work), as defined VdP , should be required as the labís pressure increases. As a potential to do work, it is not necessarily lost work. Even so let us play the game and say our first inclination might be to write:

         Lvap=dU+VlabdP    (1)

How accurate is eqn (1)? Herein the boiling System 1 is again the boiling water, and surrounding System 2 is the rest of the space lab. Eqn (1) assumes that the volume of surrounding System 2 is constant, which is not exactly correct because its volume increases as the volume of boiling water decreases. However let us consider that eqn (1) gives a good rough approximation and forgo the mass transfer aspects of the problem.

Consider that a large pot of water is boiled in the space lab, hence the labís pressure increases. Eqn 1 is still problematic because as the pressure inside the space lab increases, then the mean molecular volume in the gaseous state must decrease. Therefore boiling in the space lab might need to consider the path dependence of pressure with volume. And if the gas inside of the space lab is ideal (PV=NkT) then the work might become a logarithmic function. The logarithmic function based upon the ideal gas law would be an isothermal function hence ignores that this may also result in heat being added to the space labís interior, due in part to increased molecular friction i.e. natural P-T relationship.

Certainly the understanding of boiling in a rigid body in outer space with complete precision may become rather complex. However: Imagine the far-fetched possibility that the space lab had some elaborate engineering that manages to keep the space lab isobaric. If this engineering marvel keep everything isobaric throughout the whole process then the latent heat of vaporization would equal negative of latent heat of condensation. Hence:

  Lvap=dU                  (2)

 

The realization is that eliminating gravity simply means that no work was actually required.  Of course this is not exactly true in the case of the space lab because the pressure increases due to boiling and it eradication by the space labís devices will not necessarily be instantaneous and continuous.    

No matter we can now think of it this way, weight of the atmosphere on Earth means there is a downward force that expanding systemís must overcome, and this force is non-existent in space.

 

Therefore boiling in the space lab is nothing more than an increase to both the thermal energy and the number of gaseous molecules in the space lab. If in its interior pressure and/or temperature were allowed to increase then the ability of the gas within the lab to do work will increase. Even so no work is actually done.

There has been research done in zero gravity boiling by Herman Merte6 and others. They have found that due the lack of buoyancy and convection in weightless environments, the boiling tends to involve large often singular bubbles, as the bubble tends to stay near the heater, rather than form the cascade of smaller bubbles as normally witnessed here on Earth. It should be stated that such experiments were performed under the premises of traditional thought, rather than the understanding presented in this book.

 

Copyright Kent W. Mayhew

 

 

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This website is copyright of Kent W. Mayhew who in 2018 resides in Ottawa Ontario Canada
 
   This website is full of new ideas, which are the property of Kent W. Mayhew.  
 
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