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Car air condition power ratings?

Would anyone happen to have a vague idea of the power rating of a typical car air condition system (such as that in a Rover SD1)? I'd like to have a ball-park figure for the wattage (or any scalar equivalent such the British Thermal Units per hour) as a measure of the heat transfer that such a system is capable.

For example, I think I've read somewhere that the radiator for a typical car engine water-cooling system might dissipate about 3kW (or maybe that was the figure for a tractor, not sure). But obviously cooling air at

30C requires a considerably lower transfer of energy than cooling water at 90C...

Michael

Reply to
Michael Kilpatrick
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I don't have an exact figure, but the main rad dissipates a great deal more than 3 kW. I read of one chap using a Jag one as the heat exchanger for a warm air system in a house. So more like 20-30 kW. A decent car heater produces maybe 5 kW.

I also remember reading a tech article about the then new Rolls Silver Shadow. It said the AC took about the same power as a Mini at full belt...

Reply to
Dave Plowman (News)

My books tend to stop at about the time air-conditioning became common. Presumably they have a coefficient of refrigeration of 2 or 3(?), so several times the input power to the compressor is being dissipated.

Greene & Lucas "Testing of Internal Combustion Engines", 1969 show typically 30-odd percent of the input energy being dissipated through the radiator, so rather more than the maximum mechanical output of the engine. An SD1, with a power of 150-ish bhp, would have a radiator capable of getting rid of at least 150kW, or whatever that is in ton-acres/cubic fortnight.

Reply to
Kevin Poole

If memory serves me right, the a/c system in a Bentley produces the equivalent cooling as 16 domestic fridges.

Reply to
Pete M

Typical car aircon uses around 5 bhp / 4kW. The thermal efficiency is about 3.42 (i.e. for each kilowatt of input mechanical energy the aircon can pump out 3.42 kW of heat. So at full output the aircon could be extracting around 14kW of heat from the incoming air.

Reply to
Steve Firth

Ah, I imagine the figure must have been 30kW for the radiator in question, and I must have stripped off the zero.

Michael

Reply to
Michael Kilpatrick

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Pete M saying something like:

So, that's about four football pitches, right?

Reply to
Grimly Curmudgeon

Probably. I suspect it's quite a bit when measured in whatever you measure aircon thingies in..

Reply to
Pete M

It's normal to use consistent units, SI with SI and Imperial with Imperial. So bhp with BTU/h and kw with kw.

Engine with 110Kw output would need 150Kw rad. A 150bhp engine a

512276.9 BTU/h rad. In practice it's usual for rads to be much bigger than the rated power would require.

What are you doing with that book? Mines a '69 edition too. I'm not sure if it's permitted for 2 people in a newsgroup to have the same reference library.

Reply to
Peter Hill

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