How Automotive Air Conditioning Works You're stopped in traffic on an August afternoon. Sweat drips from your neck all the way down your back until your shirt absorbs it, making a damp spot between you and the seat. Your legs are either stuck to the vinyl upholstery or prickled by its cheap velvet. Your hands feel like they're about to slip off the steering wheel, and you're thankful your eyebrows are keeping the sweat from running into your eyes. What's missing from this picture? It's become nearly universal, with 99 percent of all new cars as of summer 2010 coming equipped with it. When it's missing, we notice. How Car Cooling Systems Work It's also been with us longer than you might think. Packard invented automotive AC all the way back in 1939, and in 1940 was the first car company to offer factory-installed air conditioning. Of course, this early system didn't have a thermostat, but it was better than not having anything at all. The idea caught on, though, and by 1969, more than half of all new cars were sold with air conditioning built in.

That's not including the aftermarket AC units that could be installed during the first heat wave of the year, when the new owner regretted his penny-pinching at the dealership in January. Eventually, it was determined that the refrigerant used for decades in automotive AC, known as R-12, CFC-12, or its brand name Freon, was damaging the ozone layer (it's a chlorofluorocarbon). It was banned from being manufactured in the United States and an alternative, called R-134a or HFC-134a, was required for all cars manufactured after 1996. Now, any car older than that needs to be retrofitted with a new system that can use the newer, safer refrigerant. Air conditioning has worked pretty much the same way for its entire existence: it cools and removes humidity from the air. There are three main parts to the system -- the compressor, condenser, and evaporator -- that achieve this, plus a few other parts to keep the system running smoothly. Let's take a look at each.How does this work. Available in high-resolution and several sizes to fit the needs of your project.

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Vectors, or eps files are included in the price of your purchase. How long can I use these images? Our license is a global/world-wide usage license that lasts in perpetuity. Once you have downloaded your image, you have life-long rights to use it under the terms of the license purchased. Can I cancel my subscription?We offer a money-back guarantee. If at any time you're unsatisfied with your experience with us, you can cancel your subscription.Please feel free to copy this air conditioning circuit and cycle diagram and print it out.panel mount ac connector The component at #1 in this air conditioning circuit and cyclehow to move hvac unit diagram is the compressor.how hvac works pdf The compressor is the heart of the system; it keeps the refrigerant flowing through the system at specific rates of flow, and at specific pressures.

It takes refrigerant vapor in from the low pressure side of the circuit, and discharges it at a much higher pressure into the high side of the circuit. The rate of flow through the system will depend on the size of the unit, And the operating pressures will depend on the refrigerant being used and the desired evaporator temperature. The component at #2 in this air conditioning circuit and cycle diagram is the condenser. The red dots inside the piping represent discharge vapor. The solid red color represents high pressure liquid refrigerant. Most air cooled air conditioning and refrigeration systems are designed so that the refrigerant will condense at a temperature about 25 to 30 degrees above outside ambient air temperature. When the hot refrigerant vapor discharged from the compressor travels through the condenser, the cool air flowing through the condenser coil absorbs enough heat from the vapor to cause it to condense. If the outside air temperature is 80 degrees, the system is designed so that the temperature of the refrigerant, right at the point where it first condenses, will be about 105 to 115 degrees.

Why do we want the refrigerant to condense at this relatively high temperature? So that the air will be very cold relative to the temperature of the discharge vapor, Which will allow the latent heat energy in the vapor to transfer over to that relatively cold air, And cause the refrigerant to condense. This transfer of heat from the vapor to the flowing air is what makes hot air blow out of your air conditioner's condensing unit. At this stage in the air conditioning circuit and cycle diagram, high pressure liquid refrigerant will flow down the liquid line, through a filter drier that is designed to prevent contaminants from flowing through the system, and on to the metering device. The metering device, component #3 on this air conditioning circuit and cycle diagram, is the dividing point between the high pressure and low pressure sides of the system, And is designed to maintain a specific rate of flow of refrigerant into the low side of the system.

If the wrong capacity of metering device is used, or if there is a problem with the metering device, An incorrect quantity of refrigerant will flow into the evaporator. When the refrigerant passes through the metering device, it drops from about 225 psi to about 70 psi, It also drops in temperature from about 110 degrees to about 40 degrees, And it wouldn't be too inaccurate to imagine it acting like warm soda when you shake the bottle and pop the top off. It shoots out into the evaporator foaming, bubbling, and boiling, And remember, it's at a low pressure, so it's only boiling at about 40 degrees F. And that brings us to the evaporator, component #4 in the air conditioning circuit and cycle diagram. There will be relatively warm air flowing over the evaporator coil, lets say about 80 degrees. The air conditiong system is designed so that the refrigerant will evaporate in the evaporator at a temperature of about 40 degrees, so that it will be cold compared to the warm air flowing over it.