Modern Hot/Cold Air

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Luckily in my life, they just work but there’s gotta be way more to it than gas/electricity make air hot, refrigerant/coolant make air cold. Also what is refrigerant/coolant?

Also I’m sure it can vary in application so I’m mainly asking about buildings/residences.

In: Technology

7 Answers

Anonymous 0 Comments

Electric heaters are pretty simple. They use resistance to heat up a wire, and use that to heat the room. They turn electricity into heat energy, basically.

Coolers are a little more complex, but on the simplest level, they take the heat out of the air inside your room and pump that heat outside.

I’m sure someone with more intricate knowledge than me will be able to come up with a better explanation, but those are the broad strokes.

Anonymous 0 Comments

Refrigerant is the substance used in the cooling mechanism of a refrigerator or air conditioner or similar device. The exact substance used is chosen in respect to the design parameters of the machine – where it is used, the amount of cooling required, etc.

This substance is pumped under pressure through a pipe. When the pipe gets to where you want the cooling the pipe size is changed to cause the refrigerant to be under less pressure. This pressure drop makes it colder which cools what you want to cool. The cold refrigerant is pumped out of the cooling area and recompressed which warms it up. The back of a domestic fridge or freezer is warm as that is where this heat is dumped into the atmosphere.

Anonymous 0 Comments

Temperature is the local egress of macross not all the way to the other macross and there can be temporary and permanent change in temperature. For example, chicken is cooked into raw chicken sashimi (warmed raw chicken )at 100 microtherm from the item 1200 to the item 1300 and further, chicken can be cooked into cooked chicken full chicken at 1700HZ 400 microtherm. For cooling, heated air exists at item 350 and cooled air exists at item 330 with air existing above both of these, making the cooling and heating of air a use of illegal therms with microtherm minus twenty for heated air and microtherm minus fifty for cooled air which is easier to generate by thermic load by an evaporate cooler from running water item 300 with evaporative cooling at microtherm 30 which is simple action. The appliance which generates this action of cooling the air often works on a serial forward feed with some maybe 3 feed item 370 to item 350 item 350 to illegal 340 and illegal item 340 to item 330 which are formalized as the compression, expansion joint, and heat diffusor as items. As well, a wizard can generate cooled air by simply generating cooled air by targeting air and applying negative 40 microtherms with some kind of magical device.

Anonymous 0 Comments

This requires a thermodynamics lesson. But I understand and relate to the question – makes no fucking sense how the adiabatic cycle works. But it does and it’s really awesome !

Anonymous 0 Comments

Have you ever noticed how a spray can goes super cold when you spray it? That’s because gas cools down when it expands. After a while, as the spray can soaks up heat from the room around it, it’ll warm back up to room temperature. Because you’re soaking heat from the room, the room goes colder overall. The same also works in reverse: If you compress a gas, it’ll warm up. Wait a while and it sheds heat and cools down to room temperature (but warms up the room as a consequence).

So, now, the trick is to set up a a machine that does both of these at the same time.

You pump gas into one room and let it expand, so it goes cold. You let it soak up heat from the room, that room cools down. Move the now warm gas to another room, and compress it so it warms up even further. Let it cool down, warming this room. Move it to the cold room, let it expand… and we complete the cycle. This is called a heat pump.

In a refrigerator, the “cold room” is the fridge itself and the “hot room” is your kitchen. In an AC, the cold room is your house and the the hot room is the outside world. You can also use a heat pump for heating: The outside is the cold room, and your house is the hot room.

Anonymous 0 Comments

The 2 most simple system for heating is gas and electric. You burn gas, generates heat, which then heat up a coil of fluids, which goes to a radiator and gives off heat. In electric heating, electricity is ran through a high resistance material, which heats up. Air is blown through the heating element.

For heat pump, this is the fascinating system. It pumps heat from one area to another. It uses a gas that can easily be converted between a gas and a liquid. The type of gas is specific to the temperature you’re trying to achieve, and that depends on its use case.

The principle is this: you take a gas, and compress it to a high pressure. When you compress a gas to a high pressure, it inadvertently gets hotter. That’s the “heat of compression” part of the first law of thermodynamics.

So now you have a hot gas as a source of heat. You run that hot gas through a radiator (condenser) and blow air across it, the air gets hot. This, inadvertently cools down the gas. When the high pressure-hot gas meets a cold surface (the condenser), it condenses into a liquid and remains at high pressure. Pretty much how a cold glass of water causes water to condense on the glass.

So now you have a high pressure-lower temp liquid in the system. To get this liquid to an even lower temperature, you need to turn it back into a gas. In order to turn it back into a gas, it needs to be in a low pressure area. To do so, you pass the liquid through either a thermal expansion valve or an orifice tube. Those devices acts as a gate. On one side of the gate, there is the high pressure liquid. On the other side of the gate, is a low pressure area. When the liquid passes through the gate, it meets a low pressure area, and quickly evaporates into a gas. This is governed by the enthalpy of vaporization part of the 2nd law of thermodynamics. When a liquid evaporates, it gets cold.

So now, you have a low pressure-cold gas. You pass it through another radiator (this is called the evaporator). Hot Air is blown through the evaporator, depositing its heat to the cold gas. This is how you get cooling. The cold gas is now a warmed-low pressure gas. The gas then, goes back to the compressor, which gets compressed again to a high pressure gas, inadvertently, gets hot again.

The heat pump system has the compressor, a radiator, an air handler, and another radiator. The 2 radiators switches role between condenser or evaporator depending on where you’re trying to move the heat. If you’re trying to cool the inside of your house, the radiator in the outside unit is the condenser, and the radiator in the air handler is the evaporator. If you’re heating the inside of your house, they switch roles.

The reason why your heat pump is able to extract heat from the outside in the winter, is because the temperature outside is still hotter than the temperature of the low pressure-low temperature gas. It’s only cold to you. Likewise, when it’s scorching outside, it can still cool your house because the air temperature outside is still colder than the high pressure-high temp gas.

Simply put, during the winter, the heat pump is trying to cool the outside, by moving heat to the inside. During the summer, the AC is trying to heat the outside by moving heat from the inside to the outside.

Anonymous 0 Comments

Most heaters work by one of three principles:

* Push electricity really hard through a wire that resists current going through it. Resistance generates heat, and that heats the air around the coil. (You can see this at work on electric stove burners.)
* Burn something (coal, gas, wood, etc.), and make use of that heat to heat other stuff. This is your standard gas furnace.
* Heat up water, and then pump that hot water through pipes in the space you want to heat. Some “combined heat and power” systems use this, especially in geothermically-active areas like Iceland.

Refrigeration systems usually use one basic process, but particular variations exist. The TL;DR is that you can exploit thermodynamic processes to use something that evaporates at low temperature in order to extract heat. It works like this:

1. Send the refrigerant into an electrically-powered compressor. This raises the pressure and temperature of the refrigerant.
2. Pass the pressurized, hot refrigerant through coils at the back, which dissipate this heat, producing pressurized liquid at ambient temperature.
3. Pass the now-cooled refrigerant to coils inside the insulated refrigerator, where the refrigerant is then sprayed (still inside the closed system), causing it to drop in pressure and evaporate.
4. Doing this extracts heat from the refrigerant’s surroundings, causing the inside of the refrigerator to cool down.
5. Pump the resulting evaporated refrigerant back into the condenser. Repeat from step 1.

Both AC units and refrigerators use this same principle. Refrigerators just get things much colder.

You can experience the cooling effect yourself, by the way, simply by rubbing a few drops of rubbing alcohol on your skin. That’s a volatile compound that evaporates at temperatures below your body temperature, so it extracts heat from its surroundings (specifically, your skin) in the process of evaporating away. Freon (specifically Freon-12), aka dichlorodifluoromethane (CCl2F2), is one example of a refrigerant. Because it evaporates at around -30 C, freon works for getting most things we want to get cold. It can’t cool anything to lower than that temperature.