Multiple Choice
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Re: Multiple Choice
Re: Multiple Choice -- robertedelong	Post Reply	Top of thread	Forum

Posted by: scalarcharge ® 11/17/2006, 08:12:49 Author Profile eMail author Edit

From Machine Design Second Edition by Anthony Esposito and J. Robert Thrower, Delmar Publishers. ISBN: 0-8273-4081-8 Horsepower=Tn/63000 Where: T=torque in pound-inches n=rotational speed in revolutions per minute ********** From Applied Fluid Mechanics Sixth Edition by Robert L. Mott, Pearson Prentice Hall. ISBN: 0-13-114680-7 Conversion factor: 745.7W/Hp *********** So: 2000 lb * ft X (12in / ft) = 24000 lb * in 24000 x 60 / 63000 = 22.86 Hp 22.86 Hp x (745.7W / Hp) = 17044.6 W = 17.04 kW (This is power) if ran for 1 hour the energy output would be 17.04 kW-Hrs if ran for one day, the energy output would be 409 kW-Hrs (17.04 x 24) Right? EDIT ...and *then* factor in the efficiency of your generator. The above is just the power supplied *to* the generator. Modified by scalarcharge at Fri, Nov 17, 2006, 13:05:40

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Re: Multiple Choice
Re: Multiple Choice -- robertedelong	Post Reply	Top of thread	Forum

Posted by: leonardo ® 11/17/2006, 04:42:05 Author Profile eMail author Edit

1 lb = 0.4536 kg 1 ft = 0.3048 m power = (torque) x (angular velocity) torque = 2000 * 0.4536 * 0.3048 * 9.8182 = 2714.9 Nm in the above I multiply for 9.8182 to convert from kgf to N angular velocity = (2*PI*n)/60 = 2*3.1415*60/60=6.2831 rad/s power=6.2831*2714.9 = (circa) 17052 W = 17,05 kW so the energy delivered in 1 hour is about 17,05 kWh

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Re: Multiple Choice
Re: Multiple Choice -- robertedelong	Post Reply	Top of thread	Forum

Posted by: cakub ® 11/15/2006, 17:43:40 Author Profile eMail author Edit

Correct result is 17.038kW-hr. One wat drawn from the source during one hour makes one kilowatt-hour of energy.

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Re: Re: Multiple Choice
Re: Re: Multiple Choice -- cakub	Post Reply	Top of thread	Forum

Posted by: cakub ® 11/21/2006, 18:07:18 Author Profile eMail author Edit

Ihave to correct a misspel.Instead of "...One wat drawn from the source during one hour makes one kilowat-hr of energy" Correct result is 17.038kW-hr. One kiloWatt of power drawn from the source during one hour makes one kilowatt-hour of energy. The real power available depends on the energy conversion efficiency. It is always smaller then one. Thus your generstor will generste less then 17.038 kW-hr.

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Re: Multiple Choice
Re: Multiple Choice -- robertedelong	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/07/2006, 15:29:11 Author Profile eMail author Edit

it is 17.038 kW-hr Power (in hp) = (torque x angular speed) / 5252 which gives us 22.85 hp (do the math yourself) now convert 22.85 hp to W = 17,038 Watts or 17.038kW-hr

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Re: Re: Multiple Choice
Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: Administrator ® 11/09/2006, 14:57:05 Author Profile eMail author Edit

Posted on behalf of robertedelong. Good day to you; I am working a a project that requires engineering expertise. The question that is posted has been asked 6 or seven times (once on your forum) I have received 7 different answers; I don't just mean a few numbers apart but some are as far apart as the sun and the earth; after receiving the response on your forum I finally contacted an "expert" on the ###### website and paid him $20 for an answer; here is what was returned to me: Given, Torque T = 2000 ft lb Speed, R = 60 rpm The above value of torque is in ft lb. To get the value in metric units, we need the following conversion values: 1 ft = 0.3048 m 1 lb = 4.45 N Therefore, the value of torque in metric units is: T = 2000 * 0.3048m * 4.45 N i.e T = 2712.72 Nm Similarly, the given speed R is is in rpm. To get the value in metric(rad/s) we need the following conversion values: 1 rpm = 2*PI/60 rad/s [Where PI = 3.14] Therefore, the value of speed in metric units is: R = 60*2*PI/60 i.e. R = 6.28 rad/s Now, to get the power generated by the generator, we use the following formula of power: Power = Torque*Speed i.e. P = T*R i.e. P = 2712.72Nm * 6.28 rad/s i.e. P = 17035.8816 Nmrad/s i.e. P = 17035.8816 Joule/s [The unit for energy is Joule] i.e. P = 17035.8816 Watts [Joules/s = Watts] i.e P = 17.036 KW [1KW = 1000 Watts] The above vale of P is the power generated by the generator in one second. To get the power generated by the generator in one hour, we need to multiply the above value by 60. Therefore, X = P*60 i.e. X = 17.036*60 KWH i.e. X = 1022.16 KWH [ANSWER] I don't know is this is correct or not however I do not want to make a big splash or tell someone they are wrong on your forum. How would you suggest I approach this to get the final and correct answer? Thanks for your help BOB Modified by Administrator at Thu, Nov 09, 2006, 14:57:42

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Re: Re: Multiple Choice
Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: scalarcharge ® 11/09/2006, 07:22:54 Author Profile eMail author Edit

Just for kicks... Would you need to account for the efficiency of the generator? Modified by scalarcharge at Thu, Nov 09, 2006, 07:38:24

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Re: Re: Re: Multiple Choice
Re: Re: Re: Multiple Choice -- scalarcharge	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/09/2006, 09:30:40 Author Profile eMail author Edit

yeah, why not just assume 80% efficiency? or roughly 13.5 kw-hr

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Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/09/2006, 16:14:15 Author Profile eMail author Edit

Robert---you are ALMOST there. You got exactly what i did... 17.036 kW of power (look at my earlier post). But, when you tried to call it a kilowatt-hour, that's where your assumption is wrong. I think the definnition of a kW-hr might help. kilowatt-hour "The work performed by one kilowatt of electric power in one hour. The unit on which the price of electrical energy is based. A 1000 watt light bulb operating for one hour would use one kWh. A measurement of energy. One kilowatt hour is equal to one kilowatt being used for one hour" So there we have it---17.036 kW produces just that, 17.036 kW per hour. Your friend was confused with the fact that a Watt is measured in Joules per second. So the answer can be termed either A.) 17.036 kW-hr or B.) 61,329,600 Joules one more quote from wikipedia might help Definition One watt-hour is the amount of electrical energy equivalent to a one-watt load drawing power for one hour. This is equivalent to 3,600 joules, the joule being the SI unit of energy. Thus a kilowatt-hour is 3,600,000 joules or 3.6 megajoules. For example, a 60-watt light bulb uses 60 watt-hours of energy every hour. Similarly, a 100-watt light bulb uses 100 watt-hours in an hour. The kilowatt-hour is usually used by U.S. power companies to measure power usage, so a rate of US$0.10 per kilowatt-hour will cost US$0.10 to run a 1,000-watt light bulb for one hour. Similarly UK power companies define 1 unit of electricity as 1 kilowatt-hour, which costs anywhere between 4 and 20 UK pence depending upon tariff. Modified by blakes30 at Thu, Nov 09, 2006, 16:35:45

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Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: robertedelong ® 11/09/2006, 17:14:59 Author Profile eMail author Edit

OK everybody; Thanks for you help so far; so now lets look at the multiple choices I've gotten so far: A. 2.7 KWH B. 1510 KWH C. 9720 KWH D. 17.038 KWH E. 1022.16 KWH Seems to be a lot of confusion. I reached the point where I've decided if I can get THREE people to answer the same I will go with that answer. So far NO ONE agrees. Any other contributors?

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Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Multiple Choice -- robertedelong	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/09/2006, 17:19:41 Author Profile eMail author Edit

did you read what i posted? math and physics are beautiful because they are perfect. Numbers are exact!!!!!!! Plug the numbers in for yourself. You have the right answer, i posted it with a very long drawn-out description of exactly why and how i got the correct answer. I would suggest you start with learning what a Joule is and then what a Watt is. Energy vs Power. kw-hour is actually a misnomer. It is a measure of energy, not power. If you multiply a watt, by time, you are back to energy. Don't trust me, plug in the numbers for yourself. YOU ultimately won't be satisfied until YOU get the answer.

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Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: robertedelong ® 11/09/2006, 19:56:32 Author Profile eMail author Edit

Yes I read what you posted; Did you ever go to a doctor and get one opinion about your condition; then to another and another opinion; then to a specialist and still another opinion; then to a chiropractor and still another; that's exactly what has happened here; If this is such a "carved in stone" principle why do I have 6 different answers; I need two more of your profession to agree; This is not an argument for the sake of argument; this is a critical question; Does it not seem odd that no one agrees and yet everyone who has answered so far is an engineer. I have sent a copy of your explanaation to the others; we'll see how they answer/

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Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- robertedelong	Post Reply	Top of thread	Forum

Posted by: Zip ® 11/12/2006, 23:36:24 Author Profile eMail author Edit

22.85 H.P.= 17.023 Watts not Kw's friend. R.P.M. is R.P.M. Metronic or Jolly olde English Zip

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- Zip	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/16/2006, 16:51:01 Author Profile eMail author Edit

are there really that many --------- engineers out there??? 22.85 hp does NOT equal 17.039 Watts (----------------------------------) the answer, is exactly what i said it was 22.85 hp = 17,039 Watts since there are 1,000 Watts in 1 KiloWatt, that is 17.039 kW and he wants it per kW-hr Admin: Ahem, you might want to re-read the forum policy for EE blakes30. Modified by Administrator at Thu, Nov 16, 2006, 17:36:48

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: Zip ® 11/18/2006, 23:05:36 Author Profile eMail author Edit

TOUCHE!! Looks like I'm the ---A ---! Zip Modified by Administrator at Sun, Nov 19, 2006, 08:48:24

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- Zip	Post Reply	Top of thread	Forum

Posted by: Zip ® 11/20/2006, 23:37:24 Author Profile eMail author Edit

.01703 KwH KwH = Watts x Time over 1000 Zip

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- Zip	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/21/2006, 10:42:59 Author Profile eMail author Edit

nope--wrong again kilowatt-hour "The work performed by one kilowatt of electric power in one hour. The unit on which the price of electrical energy is based. A 1000 watt light bulb operating for one hour would use one kWh. A measurement of energy. One kilowatt hour is equal to one kilowatt being used for one hour"

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: Zip ® 11/22/2006, 00:11:59 Author Profile eMail author Edit

1000 watt bulb times one hour divided by 1000= one Zip

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- Zip	Post Reply	Top of thread	Forum

Posted by: blakes30 ® 11/22/2006, 09:35:15 Author Profile eMail author Edit

I'm curious to know what answer the author of this thread went with????

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- blakes30	Post Reply	Top of thread	Forum

Posted by: Zip ® 11/24/2006, 00:29:45 Author Profile eMail author Edit

So am I. Zip

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Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Multiple Choice -- Zip	Post Reply	Top of thread	Forum

Posted by: robertedelong ® 12/09/2006, 09:21:51 Author Profile eMail author Edit

Well Gentlemen: Thank you all for your contribution; I certainly meant no disrespect by doubting the early responses I received; I said I would go with a majority answer and I will; You all were able to muster up at least three people who agreed; I have an ongoing project that requires accurate data and you all have helped a lot. I hope you won't mind helping again in the future. Seasons Greetings

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