Know How... 157: DIY Swamp Cooler, BeerLift, & TrackingPoint Hack

How an AC works and how to build your own simple version for staying cool this summer, Beer lifting quad copter, and the TrackingPoint gun hack from BlackHat.

Let's talk about Air Conditioning

To talk about AC, we first need to make clear what "hot" and "cold" really are.

• "Hot" is really just energy in the process of being transferred from one body to another -- From the body that has more energy, to the one that has less


• In any given system, this transfer of energy will take place until you reach maximum entropy: the energy is as evenly distributed among all the bodies in a system as is possible.


• Also, in any given system, the energy in that system will stay constant (unless that energy is somehow moved away from that system)

So... if we have air blowing in our face, and it feel "hot", it just means that the molecules in that air contain more energy than the molecules in our face, and energy is being transferred from the air to our faces.

Conversely, if that air feels "cold" it means that the molecules in that air contain less energy that the molecules in our face, and energy is being transferred from our faces into the air.

Now that we have that sorted, let's talk about HOW we make that blowing air hot or cold.

To make air feel hot, we simply add energy to it:

• A furnace burns gas or uses electricity to heat up coils


• Air is blown over the element being heated by the gas or electricity


• That air "absorbs" heat from the element


• TA DA! (Hot Air)

But to make cold air, the process isn't so simple:

• We can't just add energy into air to make it cold. We need a way to take energy away.


• And remember... the energy in a given system will stay constant unless that energy is somehow moved away from that system


• The answer is to build a system that will absorb heat from one system, and release it into another.


• And THAT is what an air conditioner is designed to do!

Let's talk about a simple 2-stage AC: It has 4 parts

1. Compressor


2. Condensor Coil


3. Expansion Valve


4. Evaporator Coil

1. Compressor
   
   
   • The Compressor takes a gas within the system and pressurizes it.
   
   
   • Important to note: If you have a gas that has energy level "x" at its regular volume, and you pressurize it to 3x it original pressure in the same volume, then that volume MUST contain 3x the amount of energy. (Again, in a closed system)
   
   
   • So... if I have 1 cubic meter of gas at 50 degrees, and I pressurize it to 3x it original pressure, then that volume of gas (at 3x pressure) should be 150 degrees.
   
   
   • Super Side Note: This is the "Ideal Gas Law"
     
     
     • ((P1*V1)/T1) = ((P2*V2)/T2)
     
     
     • (Initial Pressure * Initial Volume)/Initial Temperature = (Final Pressure * Final Volume)/Final Temperature
   
   
   • Ok... so now we have a bunch of HOT pressurized gas, but we want COLD gas.


2. Condensor Coil
   
   
   • The condensor coil takes the now pressurized gas and gives it contact (through a conductive surface that allows the closed system to retain the gas, while conducting the energy of that closed system) with an outside system.
   
   
   • We know that energy (heat) will want to flow from a body of high energy, to a body of lower energy
   
   
   • If the system in which that condensor coil is of a lower energy state than the system contained within the coil, then energy (heat) will flow out of the gas, and into that outside system.
   
   
   • Given enough time, the
   
   
   • Just for

Bui

These show notes have been truncated due to length. For the full show notes, visit https://twit.tv/shows/know-how/episodes/157

Hosts: Fr. Robert Ballecer, SJ and Bryan Burnett

Technical Director: Alex Gumpel

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