Demonstrate Some HVAC Basics the Fun and Cheap Way
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The first tool is a hand boiler. The hand boiler has a bottom bulb with ether alcohol. When you hold the bulb, the liquid rises to the top and may bubble. That occurs because your hand transfers heat to the ether alcohol, and the molecules begin moving more rapidly, creating more pressure in the closed space and making the liquid occupy more of that space. The hand boiler also illustrates that boiling can happen at relatively low temperatures, not just 212 degrees Fahrenheit (100 degrees Celsius). (You can find the hand boiler HERE).
The next tool is a Stirling engine. You can put an ice cube on top of it and hold the apparatus in your hand. As you hold it, the heat from your hand transfers to the Stirling engine. When you start spinning the flywheel, it keeps going. That is because the pressure differential between your warm hands and the cool ice cube moves the bellows between them, and those bellows keep moving up and down as pressure builds and releases. The movement of those bellows turns the flywheel. (You can find the Stirling engine HERE).
We recommend using an electrical kit with a fan motor, ammeter, voltmeter, lightbulb holders, generator, bell circuit, and more for teaching the electrical side of HVAC. The electrical kit is a fantastic way to introduce electrical basics to middle and high school students. (You can find the EUDAX electrical kit HERE).
Another interesting novelty is the magic drinking bird. The drinking bird has two bulbs connected by an elongated glass tube. The lower bulb contains liquid methylene chloride, and the top bulb only contains invisible vapor. When the bird’s head gets wet, the water begins evaporating immediately, cooling the head. (Think about stepping into a room with a fan while you’re sweating; you cool down as your sweat evaporates.) Some of the vapor in the upper bulb condenses, reducing the vapor pressure in the top bulb. Since the vapor pressure in the bottom bulb has remained constant, the pressure differential between the bulbs will force some of the liquid will rise to the top bulb to maintain equilibrium. Then, the bird appears to drink when the top bulb gets heavy enough to tip. A similar pressure differential forces the bird back upright. If the bird has tipped its head into some water, the process will repeat itself. (You can find the drinking bird HERE).
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