A mate of mine was saying the hotter it is outside the car the cooler the air con works,I would of thought if it was cooler outside then the air coming out will be alot colder,If my mate is right how does it work?
Refrigerant gas is compressed into a liquid form in the condesor under high pressure, then this liquid is released under controlled conditions into the evaporator (heat exchanger) there by turning cold as it looses pressure and returns to a gas. This cools of the evaporator which you blow air through and into the cabin to cool the air inside the car. the gas is then carried back to the compressor where it is compressed back into a liquid in the condensor coil (creating heat) and the process starts over again.
Therefore, the cooler it is outside, the less heat the liquid refrigerant has to loose as it turns back into a gas cooling the evaporator and the less the Aircond has to work.
The gassing in the evaporator carries away heat. look up "latent heat of evaporation". The heat is being removed from the air that is being blown over the evap thus making it feel cooler. This heat is then carried to the condenser where the condensation process releases it (sort of the reverse process). These are the two "heat exchangers" and how they absorb or dispel the heat.
AC works on the principle of transferring heat from one point to another. In very basic terms, a gallon of gasoline when combined with oxygen can generate 106 K BTU of heat when burnt. Where if that same gallon of gas could somehow be used to mechanically run a compressor with 100% efficiency, an AC system could transfer as much as 10-15 times that amount of heat. AC systems are most efficient at around 80*F, but that SEER factor decreases as the ambient temperature increases dropping to about unity at around 130*F. Vent temperatures are useless in determining the efficiency or the amount of heat transferred in some unit of heat measurement. Temperature is just the force of the equation, air flow is the other, compounded by humidity that determines the amount of heat transfer.
But in regards to vent temperatures, some AC systems are designed to work much harder at higher ambient temperatures. Fixed orifice systems are the worse, if the low side pressure skyrockets to 80 PSI, maximum vent temperatures could on be as low as 75*F, but in a good TXV POA or variable displacement where the low side is held automatically at 30 psi, still capable for providing near freezing point air temperatures. Provided these systems have the capacity to handle it.
No set answer to your question, too many other variables to consider.
Thank you now i know how it works.
No Karl im not Slingblade>>>>Just Blade
That's cool Blade... Just checking as there is a UK refrigeration engineer who uses the handle "Slingblade" and he can be a bit of a wind up merchant
Never knock on deaths door... Ring the doorbell and run away, death really hates that!
The cooler it is outside the car, the more heat that can be transferred from the condensor to the air(Newton's law of cooling), which ultimately will determine how much heat can be absorbed and transferred from the evaporator that feeds the cabin, cooler interior temps.
Sucking warmer air across the evaporator will increase the total amount of heat transferred by the system(Newton's law of cooling again), it will only increase the vent and cabin temps
Did you read that in Newton's "PhilosophiÃÂ¦ Naturalis Principia Mathematica"? Didn't think he got involved with thermodynamics nor in Boyle's laws. But I am also here to learn.
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