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> "Note: Car air-conditioners are funny systems. They use the heat from the combustion engine to move heat from inside the cabin to the outside world. So you ar

> "Note: Car air-conditioners are funny systems. They use the heat from the combustion engine to move heat from inside the cabin to the outside world. So you are literally using heat to move other heat." Car air-conditioners are not powered by heat from the combustion engine. They are powered mechanically by a belt ("serpentine belt") connected to the engine. Or, in some cases such as battery electric vehicles, powered electrically with the compressor turned by an integrated electric motor. The extra heat produced is just a byproduct (thermal inefficiency) of producing and transmitting that mechanical/electrical energy.

dragontamer 6y ago
> Car air-conditioners are not powered by heat from the combustion engine. They are powered mechanically by a belt ("serpentine belt") connected to the engine. But that belt is powered by the expansion of gas that takes place inside of a piston, due largely to the increase in heat from combusting gasoline. Ultimately, an ICE engine is a heat-engine (like a steam engine or sterling engine, but different).
- Reason077 6y ago
  Yes, but the useful energy in a combustion engine comes from that expansion of gas driving the pistons. The heat is, for the most part, just a wasted byproduct. (It can be used for ancillary purposes like heating the cabin).
  - dragontamer 6y ago
    > Yes, but the useful energy in a combustion engine comes from that expansion of gas driving the pistons. Isn't that expansion of gas largely driven by the increase of heat? https://en.wikipedia.org/wiki/Internal_combustion_engine https://en.wikipedia.org/wiki/Internal_combustion_engine Wikipedia lists the ICE as a heat-engine. ------ With that being said: the octane combustion formula has 25 O2 as input and 16 CO2 + 18 H2O as output (and I assume the H2O is mostly water vapor). So that's 25 molecules of gas input -> 34 molecules of gas output. So it seems like more "CO2 + vapor" is created than the number of input O2 molecules. But that only accounts for 34% expansion of the volume of the stroke. (25 mols input -> 34 mols output). The rest of the stroke's power comes from the ideal-gas law: higher temperature means higher pressure and larger volume. Literally the heat generated by the chemical reaction.

dragontamer 6y ago

> Car air-conditioners are not powered by heat from the combustion engine. They are powered mechanically by a belt ("serpentine belt") connected to the engine. But that belt is powered by the expansion of gas that takes place inside of a piston, due largely to the increase in heat from combusting gasoline. Ultimately, an ICE engine is a heat-engine (like a steam engine or sterling engine, but different).

Reason077 6y ago
Yes, but the useful energy in a combustion engine comes from that expansion of gas driving the pistons. The heat is, for the most part, just a wasted byproduct. (It can be used for ancillary purposes like heating the cabin).
- dragontamer 6y ago
  > Yes, but the useful energy in a combustion engine comes from that expansion of gas driving the pistons. Isn't that expansion of gas largely driven by the increase of heat? https://en.wikipedia.org/wiki/Internal_combustion_engine https://en.wikipedia.org/wiki/Internal_combustion_engine Wikipedia lists the ICE as a heat-engine. ------ With that being said: the octane combustion formula has 25 O2 as input and 16 CO2 + 18 H2O as output (and I assume the H2O is mostly water vapor). So that's 25 molecules of gas input -> 34 molecules of gas output. So it seems like more "CO2 + vapor" is created than the number of input O2 molecules. But that only accounts for 34% expansion of the volume of the stroke. (25 mols input -> 34 mols output). The rest of the stroke's power comes from the ideal-gas law: higher temperature means higher pressure and larger volume. Literally the heat generated by the chemical reaction.