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7 DECEMBER 2016 Molecules by Bill Corey Pentair Water Training Institute Kind of strange that when you talk about pumps, you might talk about mo l e c u l e s . Ye t everything is made of molecules. Daniel Bernoulli was born in 1700, and even way back then he could tell water mole- cules were noncompressible. I’m not sure if he could distinguish between one water molecule and another, but he knew we could not put enough pressure to compress them. Why is this important? Because last month I talked about cooling a submersible motor and said you had to have a certain velocity of water moving past the motor to cool it. So because water is noncompress- ible, we can use a very simple formula to convert speed into head, our word for energy. The formula is V²÷2G [V2 is the veloc- ity of the water squared; 2G is 2 times the Universal Gravitation Constant (G=32.2 feet per second)] and the answer is in Head Energy. Friction Energy is heat; and remember, water is a very good conductor of heat. I’ve said in the past, motors create a lot of heat. The heat is transferred from the motor stator to the shell of the motor; and from that contact from the shell, to the water moving past it, the heat is then transferred to the water molecule. Now if the water molecule doesn’t move fast enough, the water around the motor gets hot, again water is a good conductor of heat. One-horsepower submersible motors or less have a built-in thermal-overload protector. The overload is a thermal or heat- sensitive device. So when the water around the motor gets too hot, the overload trips. Yes, it is a normally closed switch which opens up when it gets too hot. This stops the flow of electricity and, because it is also automatic, you have to wait for it to cool off before it will close and the motor will start again. Now if the water is moving fast enough past the motor, those molecules carry the heat away. What makes the water move fast enough? According to Mr. Bernoulli, it is the area the water is moving through. A meteorologist will tell you never to seek shelter from a tornado under a bridge. Why? Bernoulli said the smaller the area something is moving through, the faster it will move. When you have a tornado, the wind is already moving very fast; but when you force it through a smaller area it will move even faster. Same with water - the smaller the area it has to move through, the faster it will move. Please refer back to the last issue for the chart which told you what size the pipe would be to get the velocity fast enough to move the heat away. Now remember, we can convert velocity to head, but we can also say flow and velocity. So I can convert the velocity required to remove the heat from the motor to flow, which is exactly what the chart tells you. I hope this wasn’t too confusing. I know one guy who had a very hard time trying to understand how we could con- vert velocity to flow, but of course it is all related to the area the water is moving through. Have a good month. Let me know if you have any questions. Bill Bill Corey may be contacted via e-mail to michele@ worldwidedrillingresource.com ! *- */ )- &! *!! / %&,)( )#!* !(,!* % $')( %*#%(% ""% ! (") ,!* !&& ++) % ,%)( )*# ... ,!* !&& ++) % ,%)( )*# WorldWide Drilling Resource ®