# How much should the compressor generate?

• marellasunny
In summary, a compressor needs to add 2000W of heat to the refrigerant to suck away all the heat from a car with 2 passengers who generate 1000W of heat. The equation depends on external temperature and the compressor's efficiency.
marellasunny
Suppose the 2 passengers in my car generate 1000W of heat and the sunlight falling inside the car generates 1000W of heat, how much heat should my compressor add on the refrigerant to suck away all the 2000W of heat in the car?

I realize that a compressor is rated in pressure but I would like to know the thermodynamic equivalence.

Is the equation?

Heat generated inside car = Heat added to the refrigerant by the compressor

Apparently that would be 2000 W times a kind of efficiency of your compressor.
But you would also need to account for heat losses through the envelope of the car.
The problem also is that the efficiency strongly depends on the external temperature.
It is not the same if you aspirate hot air or cold air from the outside.
It is not the same if the heat exchanger of the compressor sees an external temperature of 40°C or -10°C.

You can convert from compression factor to power assuming an adiabatic compression and some adiabatic efficiency. However, if the compressed gas reaches a temperature near the external cooling air temperature, you will have no way of cooling. Therefore, you understand that higher external temperatures will demand higher compression ratio.

______________________________
I hate cars and energy wasting too.

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Passengers don't generate anywhere close to 1000W of heat, but regardless, the concept you are looking for is coefficient of performance (COP). A good air conditioner has a COP of 3 or 4, which means for every watt of mechanical energy input, it removes 3 or 4 watts of heat from the area being cooled.

Maajdl: Cleared-up the question I had.But,by efficiency,do you mean COP/the usual thermal efficiency ?

Russ_walters:COP does not have the variable Q_compressor(dot). How can I use COP to judge how much heat the compressor needs to generate to cool down 1000W?

The input for COP is compressor mechanical work. Since conservation of energy applies, all must be converted to heat.

...or are you asking about the heat separate from the temporary increase in fluid pressure energy? The compressor is probably on the order of 60% efficient so perhaps 60% is temporarily converted to presssure energy and the other 40% is immediately added as heat.

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## 1. How does the size of the compressor affect the amount of air it can generate?

The size of the compressor directly affects the amount of air it can generate. A larger compressor will have a higher capacity and can generate more air, while a smaller compressor will have a lower capacity and generate less air.

## 2. What factors determine the appropriate amount of air a compressor should generate?

The appropriate amount of air a compressor should generate depends on several factors, including the size and type of equipment it will be powering, the operating pressure required, and the frequency of use. It is important to carefully consider these factors to determine the right amount of air for your specific needs.

## 3. How can I calculate the necessary air output for my compressor?

To calculate the necessary air output for your compressor, you will need to determine the air consumption of the equipment it will be powering, the duty cycle (how often the equipment will be used), and the required operating pressure. From there, you can use a formula to determine the required air output in cubic feet per minute (CFM).

## 4. Is it better to have a compressor with a higher or lower CFM rating?

The ideal CFM rating for a compressor will depend on your specific needs and usage. In general, a higher CFM rating will provide more air and is better for larger or more frequent usage, while a lower CFM rating may be sufficient for smaller or less frequent usage.

## 5. Can a compressor generate too much air?

Yes, a compressor can generate too much air, which can cause damage to equipment and decrease efficiency. It is important to carefully consider your specific needs and choose a compressor with an appropriate CFM rating to avoid generating too much air.

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