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Old Dec 8th 2010, 12:26 AM   #1
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Fluid mechanics- bernoulli's equation help

Figure 1.1. shows a simplified diagram of the camping stove used by a famous scientist up a mountain, in which gas under pressure is transported to the four nozzles via metal piping. A valve is used to control the flowrate by reducing the delivery pressure to a maximum of 2 kPa gauge. The diameter of each nozzle is 1 mm. The density of camping gas at atmospheric pressure is 2.686 kg m3, and its calorific value on combustion is 126000 kJ m3. Ignoring friction losses and making other appropriate assumptions, estimate the maximum volumetric flowrate of gas through the four nozzles if the valve is fully open, and hence the maximum rate of supply of heat. Comment on your answer is it reasonable?

Not sire where to begin, should I be using bernoulli;s equation? Should I also be making an assumption on height?


thank you,
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Old Dec 10th 2010, 01:48 PM   #2
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Fluid mechanics- bernoulli's equation help

You are definitely on the right track with Bernoulli. One way of checking for reasonableness is to see how long it takes to generate 400 kj of heat which is the amount of heat to bring a litre of water to the boil. (Give or take). I dont think you should worry to much about the height unless there are specifics given in the problem.
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Old Dec 12th 2010, 05:16 AM   #3
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Originally Posted by YellowPeril View Post
You are definitely on the right track with Bernoulli. One way of checking for reasonableness is to see how long it takes to generate 400 kj of heat which is the amount of heat to bring a litre of water to the boil. (Give or take). I dont think you should worry to much about the height unless there are specifics given in the problem.

Hey,

Thanks so much for replying. I have attached my working please can you check it?

Thank you.
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Old Dec 19th 2010, 03:32 AM   #4
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Fluid mechanics- bernoulli's equation help

Your equations look right to me, but remember that you need to consider a p1 and a p2, p2 is the atmospheric pressure and not zero so it will be something like "2000 - 1000" in the pressure term and not "2000 - 0". I think that the prediction Bernouli is a bit high but no inordinantly so. You will then look at the cross sectional area of the output and multiply that by the velocity to get the volume of delivery. Multiplying that by the calorific value on combustion gives you the maximum supply of heat.

Last edited by YellowPeril; Dec 19th 2010 at 03:34 AM. Reason: Extra stuff to say
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