Recently came back from a trip North on our beautiful Cape York Peninsular, (the pointy bit at the top of Australia), and the mecca of many 4 wheel drives in Australia, "The Telegraph track" and "Frenchmans Track", a really challenging couple of 4WD destinations that are on most 4WD enthusiasts list to do at least once in a lifetime, because I live up on Cape York Peninsular we get to do the trip every year, or at least every year for the past 12 years we have lived up here. Although it is "local" for us it is still an all round trip of near enough to 2000 kilometres, much of that over very bad corrugated and rocky main road, (the Peninsular Development road, or PDR), and many more rougher washed out tracks with steep sided and deep creek and river crossings, from what I've seen on video much like some of the old Camel trophy terrain of the early 90's.
As usual our 300Tdi Disco 1 went perfectly and performed impeccably throughout the trip.
Something that always happens on these really badly corrugated roads has me puzzled though, we have the A/C on all the time, (except deep water crossings), because daytime temperatures seldom drop below 30 Deg Celsius and it can get quite warm in the vehicle, on the smoother terrain the A/C just manages to keep things liveable but on the corrugated and rougher bits the air temperature exiting the vents becomes extremely cold, so cold in fact it becomes downright uncomfortable on longer bad stretches, cannot think why or if I am imagining it, but then the wife also reaches for the "turn up the temp dial", so not just me.
Thing is, anyone on here have any ideas, factual, theoretical, or just plain made up to offer on why the A/C responds this way to what my mate, driving the other Disco1, described as sitting in a vehicle that has been put into a hardware store paint mixer shaker.

Gazbo said:

put into a hardware store paint mixer shaker.

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I think you may have nailed it with that analogy...

IIRC, A/C, like most heat pumps, works by evaporating the refrigerant, and then compressing it to condense, and allow the heat to escape. ( I'm paraphrasing, on the basis that a mathematical dissertation on Boyle's Law is not required )

Thus, the effective surface area of the liquid during the evaporation bit of the cycle will affect the efficiency of the system. refrigerant is very thin, and shaking the system, will thus make it climb up the walls of any vessel its in, and also form waves on the surface, increasing the surface area, and thus the efficiency of the system...

At least, that's my sunday morning take on it.

Disco1BFG said:

Thus, the effective surface area of the liquid during the evaporation bit of the cycle will affect the efficiency of the system.

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Disco 1 BFG, sounds as if you know your stuff, thanks for that reply, it certainly makes sense, it has always had us puzzled why it occurs, I now understand better.
As my electrical engineer son always tells me when he amazes me with what he knows , "see Dad you did not waste your money on my education!"
Now just have to work out a way to keep the A/C vibrating on those super hot days whilst on the bitumen roads, maybe bolt the whole A/C system onto the top of the old Tdi engine.

Gazbo said:

a way to keep the A/C vibrating

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Do they do hardware store paint mixers in 12V ??

HTH.