Question for physisists/gas experts (1 Viewer)

[Manxcat]

We have a cadac with a very long gas cable which we attach to the exterior gas point on our Globecar campscout. This works very well.

My wife has suggested that the cable is too long and if we shorten it the heat will improve. Her thinking is that as the gas has less far to go it will have more pressure. I disagree.

Anyone here able to give a definitive answer?

 

[Printermick]

I can't quote the exact law but there is certainly friction from any liquid or gas through a pipe. I think that there is a maximum length of pipe suggested in the Cadac instructions.

 

[DBK]

How long is very long? A couple of meters will be fine. As mentioned, the pipe is an obstruction and there will be some loss of pressure, but it will be quite small unless the pipe is extremely long.

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[Kingham]

As the gas is flowing then it will be subject to internal pipework friction and a reduction in pressure. Whether or not it will make a noticeable difference to cooking temperature will be more down to the size of flame, rather than a lowering of the heat that the gas burns at.

 

[Manxcat]

Not measured it, we think it's 4m (about 12 feet)

 

[funflair]

Well at the risk of being pedantic, the pressure is the same no matter what the length of hose as long as the exit is turned off, BUT it is the volumetric flow that will suffer relative to internal losses and this indeed could cause some perceived loss off pressure BUT relative to the demand of the Cadac (more gas flow less pressure) will it make a difference over a few metres? I doubt it.

Martin

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[Fletton]

Just adapt an old fireman's hose... bigger cross section; then you can park up in France and BBQ in Spain...

 

[tonyidle]

As per 'funflair' - although I suspect that the pipe is of more than adequate cross-section for its intended purpose so the pressure will be the same at both ends. The burner jet internal diameter is minute compared with that of the feed pipe.

 

[Sandancers]

The "heat" of the flame is down to the calorific value of the gas supplied. Don't know if the value for Butane or Propane is declared on the bottles ?

But for domestic gas supply each area of the UK may have a slightly different calorific value to another and if you have a high calorific value your kettle will boil faster. Tho the difference will be small. And your gas bill is adjusted for how "good" the gas is !

The "size" of the flame may get smaller on a really long pipe run, but doubt 4m will affect it at all.

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[Dorset Diver]

Been using a 5m length on our cadac since 2009 without problems. Frankly ours gets too hot and is never used above the minimum setting. If you want more from it up-size the jet.

 

[The Wino]

If as you say it works very well why ask the question!!!!! (and remember whatever the question your wife is right)

 

[Stretto Boy]

The Wino is right : ignore the experts (who are of course correct), tell Mrs Manxcat that as always she is right, get out your pipe-cutters, comment on the remarkable improvement in the performance of your Cadac and enjoy the lovely meals that your wife cooks for you on it. Result happiness!

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[Just smiffy]

Gas in my house comes all the way from the North Sea and I've still got pressure .....

 

[pappajohn]

Won't make any noticeable difference over such a short length.
How far is it from the Russian gas fields to the UK ?

Gas doesn't suffer the same flow restrictions of, such as, water in a pipe.
Consider how far gas has to travel around your house.

 

[mitzimad]

standing pressure will always be the same its working pressure of each appliance thats affected by the length of the runand your wife is right the longer the hose the less working pressure you will have whether its discernable is another thing

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