An Engineers View of Osmosis

My first and only osmosis experiment failed.  I could not learn by sleeping with a book under my pillow. 

As a consulting engineer I was given the opportunity to design seed storage warehouses for DeKalb Genetics.    Hybrid seed is expensive to produce and  must be planted or disposed as a special waste.   It is treated with fungicides.    Environmentally controlled warehouses provide an economical solution.    Excess treated seed can be saved for the next planting season.   

I researched publications to determine the best temperature and relative humidity design conditions.  Eventually, I chose the conventional design conditions of 50°F, 50% relative humidity.  These came from experiments in the 1950s.   The engineering design included selecting contractors,  building insulation, refrigeration equipment and a control system.     The completed warehouse worked.  It met design conditions.   This was the first company seed storage warehouse that met design conditions.    I tried an alternate supplier for the next two warehouses.    Neither one worked initially.   Over the next summer,  I learned that small manufacturing short cuts were the culprit and corrected the problem.

For the next several warehouses everything worked well.   I had noticed a small but possible situation that could allow the Temperature and relative humidity control system to cause the warehouse to freeze.    I looked for something more elegant than a simple low limit thermostat with a digital control system.   After reviewing thermodynamics, I learned that  the warehouse would always seek the correct design conditions if controlled by Temperature and calculated moisture vapor pressure.    Temperature and relative humidity sensors were installed  but the control programming used Temperature and calculated moisture vapor pressure.   It always sought the design conditions. 

Everything worked well till I was called to start up a warehouse in Texas with a contractor that took a short cut.    I did not find the problem until a refrigeration unit failed.     Now,   I had some free time.  

I suspected that moisture vapor pressure control was significant, and I developed a computer model for stored seed.    Now, I could calculate storage conditions based on measured properties of a seed.   Furthermore,  the model showed why a standard rule of thumb for seed storage worked.   The sum of temperature (F) and relative humidity equals 100.   ( T + %rh = 100).   I wrote a short paper and sent it to a colleague working on seed storage for comments.  She quit talking to me.     A more refined paper submitted to a seed publication took longer  but it was rejected also.      

I found out why.  My model for moisture transfer through a seed membrane was based on the moisture vapor pressure gradient.      The accepted model for moisture transfer through a membrane was the theory of osmosis.   Osmotic pressure was related to moisture transfer through a membrane.  

So, I studied osmosis. 

My papers are published as Osmosis: The Molecular Theory.

©   Larry Howlett     HTMD Engineering     2020

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