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Old 07-10-2015, 05:47   #331
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Re: Why no Residential Fridges?

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Originally Posted by valhalla360 View Post
If you have a dozen eggs...the unit is "eggs".
If you are going to measure charge in terms of electrons...the unit is "electron charges" (or similarly you could use protons).

Speaking in terms of dozens is really just a bastardized combination of base 10 and base 12 numbering systems. Base 12 has some major advantages as it can evenly be divided by 6 differnt numbers. Base 10 can only be divided by 4 different numbers. The main downside is everyone is used to working in base 10. The most obvious point where we see this is in shipping and packaging. If you go to the grocery store and look at packaging, it's almost always base 12 based. (6 pack are 1/2 of 12, a case is a 24 pack which is 2 of 12, etc...)

The problem with calling it dimensionless is it can't have dimensions. Ie: if you have 10 kg/kg, kg/kg must equal 1 since anything divided by itself is by definition 1. Thus you have 10*KG/KG = 10 * 1 = 10 (no dimensions)

If 1 C = 1 amp* sec, the only way for it to be dimensionless is if 1amp = 1/(1 * sec). Thus 1 amp * sec = 1/(1 *sec) * sec = 1 * sec/sec = 1 * 1 = 1.

Since nothing in my engineer courses nor that I can find anything online suggests 1 amp = 1/(1 * sec), it can't be dimensionless, since we have it defined by dimensions.
Hmm… I did suggest that YMMV.

This guy knows a bit about physics and he is happy to accept that "dozen" is a dimensionless unit.

Dimensionless Units

Of course I not suggesting you need to agree but it should be interesting reading. Some of his other articles can be quite thought provoking .
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Old 07-10-2015, 06:07   #332
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Re: Why no Residential Fridges?

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Hmm… I did suggest that YMMV.

This guy knows a bit about physics and he is happy to accept that "dozen" is a dimensionless unit.

Dimensionless Units

Of course I not suggesting you need to agree but it should interesting reading. Some of his other articles can be quite thought provoking .
The guys posting to wikipedia know a lot about pretty much everything and I use it often but I don't take it for fact. Same with this guys personal web page.

Sure a "dozen" is dimensionless same as "42" is dimensionless but your example was a "dozen eggs" which has the dimension of "eggs".

Again, "dozen" isn't really a unit but more a a twisted merger of base 10 and base 12 numbering systems as I can't think of any situation where it used independent of another unit. Dozen is just a number (ie: 12).

Still doesn't make coulumbs dimensionless since we have dimensions to define it.
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Old 07-10-2015, 06:22   #333
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Re: Why no Residential Fridges?

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Originally Posted by valhalla360 View Post
……….
Again, "dozen" isn't really a unit but more a a twisted merger of base 10 and base 12 numbering systems as I can't think of any situation where it used independent of another unit. Dozen is just a number (ie: 12).
…….
You need more imagination

Try "it's cheaper by the dozen" or "buy a dozen and get one free" or perhaps better known "bakers dozen"

Should we move onto gross

EDIT: I really suggest you spend two minutes (max) reading this http://www.av8n.com/how/htm/author.html
The guy is actually well known.
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Old 07-10-2015, 06:25   #334
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Re: Why no Residential Fridges?

I've had a Coleman cooler in the past that had a Peltier plate, I didn't care about energy, I just used one while I was Road Racing motorcycles. I doubt seriously you will get them down to 40 degrees, I found it worthless and ended up just putting ice in the thing and not even bothering to plug it in
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Old 07-10-2015, 06:59   #335
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Re: Why no Residential Fridges?

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You need more imagination

Try "it's cheaper by the dozen" or "buy a dozen and get one free" or perhaps better known "bakers dozen"

Should we move onto gross

EDIT: I really suggest you spend two minutes (max) reading this About the Author
The guy is actually well known.
Cheaper by the dozen: Units = kids (similar with buy a dozen get one free with what every you are buying being the units)

You simply left part out of your quote (kids are cheaper by the dozen) same as people using "amp" instead of "amp-hr". When you skip things you change the meaning.

I looked at the guy's personal web page the first time you posted it. Nice but no different than trusting wikipedia as the final truth.

Well known is nice but no assurance his web page is accurate. Bill Nye the Science Guy is also well known but I've come across web pages detailing the science mistakes he makes.
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Old 07-10-2015, 07:25   #336
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Re: Why no Residential Fridges?

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Originally Posted by Wotname View Post
You need more imagination

Try "it's cheaper by the dozen" or "buy a dozen and get one free" or perhaps better known "bakers dozen"

Should we move onto gross

EDIT: I really suggest you spend two minutes (max) reading this About the Author
The guy is actually well known.
Yep, of course dozen is dimensionless when used by itself as it is in most of most of those statements.

However the last one isn't. A baker's dozen has an implied dimension of bread loaves.

When you say "dozen" without specify a "dozen of what", you have a dimensionless quantity.
As soon as you say "dozen feet" or "dozen minutes" you have a one dimensional quantity.
When you say "dozen amp hours" or "dozen mile per gallon" you have a two dimensional quantity.
See how it works?
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Old 07-10-2015, 07:32   #337
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Re: Why no Residential Fridges?

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Attachment 110549
FWIW This is an amp. Keeps me charged for about three hours. It does flow though. Have never measured the flow on the other end.


Sent from my iPhone using Cruisers Sailing Forum
Jhnhll, brought tears to my eyes...that was good.
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Old 07-10-2015, 08:25   #338
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Re: Why no Residential Fridges?

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Are you familiar with the efficiency of thermoelectric cooling compared to the alternatives? Have you done the math for the Amp hrs required to cool a single 325ml drink can from your ambient down to 40 degrees?
Stu yes I am rather well informed on the ineficiencies of the pielter plate systems. I see as I stated I was opening up a can of worms with this one
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Old 07-10-2015, 08:40   #339
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Re: Why no Residential Fridges?

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Just for sh*t and giggles, I did some calcs. So to take a short digression from GPH, Coulombs, dimensions and HP/ccs - here goes another direction of thread drift:

Averag US summer temperature 75F = 24C
Safe fridge temperature 40F = 4C
So we need a 20C drop
I can = 0.33litres (approx)

To raise or lower 1 litre of water by 1C takes 1kilocalorie
and 1kcal = 1.163 Watt Hours

So to reduce 1 can by 20 degrees we need
1.163 x .33 x 20 = 7.7 Watt Hours (approx)

A 100Watt panel will generate maybe 500 Watt hours per day at best
So if the system were 100% efficient, we could cool about 13 cans from a full days output of the 100 Watt solar panel.

Unfortunately Peltier systems have about 5-8% Carnot efficiency.
(Carnot efficiency is the percentage efficiency compared to a theoretical 100% efficient heat pump.)

So it will take the full output of your 100 Watt panel all day to cool a single can.

And that's without taking into account any other draw such as cooling fans to move the heat away.
OK here goes there is a cooling fan double pole unit moving air across both sides of the plate within the heat sinks. Drawing 2.5 watts. The heat side will be in a compartment with an average temp of 65 deg in the summer and as low as 45 deg in the winter. ( Puget sound) the compartment under the sink is basicly below the waterline. So I am looking at a temperature differential between 5 and 25 degrees. In the summer I actually require less refrigeration due to availability of fresh produce. ( it is an experiment all the parts are free) the plate itsself draws 5.2 amps when running. So total drawwhen operating would be 80.5 watts with an expected 30% duty cycle in winter and a duty cycle as high as 75% when used in the summer.
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Old 07-10-2015, 09:23   #340
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Re: Why no Residential Fridges?

If it's that cool and all you need is between a 5 to 25 deg temp differential, it may work for you, but so would a small amount of ice.
Most of us are looking for as much as a 60 degree temp differential, I like the fridge to be just below freezing myself, enough so I have to keep the milk on a shelf to keep it from freezing.
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Old 07-10-2015, 09:32   #341
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Re: Why no Residential Fridges?

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I challenge you to provide an independent source that supports your statement.

It must be quoted in GPH and only GPH (no adding a duration or otherwise changing the units).

I'll accept any reputable source that is within 20% (to account for rounding errors)
Oddly enough the weight of fluid GPH is used lots when calculating fuel required and weight of fuel in aircraft. They use the GPH consumption in the engine to get the weight of fuel. As GPH includes a duration (Hours) I have to include duration otherwise we just have gallons.

Since we know the weight of the fluid, calculating the weight of X GPH is quite simple.

So yes there is a real world application for it too. How sweet is that...

When we use units like Ampere's or GPH it's not just a number, there are other properties of the underling element or particle. So for GPH to have meaning you need to know what the GPH is measuring (water, diesel, Avgas, etc). Otherwise it has no meaning.

Same with Ampere. The charge of 1 Ampere has other properties depending on if the ampere is from a proton, electron, x-ray, gamma ray, etc. When we talk about Ampere it's not a imaginary number. There is an underlying physical/quantum object that is creating the charge. When we talk about Electric Current in the real world, to create that current, we are talking about electrons moving.

Yes amperes has a speed, but a ampere is not a measurement of speed, but of flow. Very much like GPH is a measurement of mass flow of a fluid, not a velocity. Yes it will have a velocity, but ampere and GPH are not that measurement. If it was velocity, we would know that an Ampere or GPH was equal to x feet (or meters) per second. We can not derive the velocity from ampere or GPH by itself, We need the conductor size and material for Ampere and the pipe or conduit size and material (for friction calculations or Reynolds number) for fluid.
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Old 07-10-2015, 09:54   #342
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Re: Why no Residential Fridges?

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Stu,

Get off the electrons and coulombs. It has no practical application.

I haven't heard coulombs since college and that was 50 yrs. ago.

This, I think, is a practical thread. I believe not a course in physics so amps work. And a google of the physics does not make you an expert.

Sorry if I sound crass. But stop with the non relevant BS.
WADR, you appeared to miss the point of my post. It was my first on this subject, and simply commented on "=" issue in terms of definitions.

Oh, wait, I see, you didn't notice that I am a DIFFERENT Stu.
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Old 07-10-2015, 09:58   #343
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Re: Why no Residential Fridges?

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If it's that cool and all you need is between a 5 to 25 deg temp differential, it may work for you, but so would a small amount of ice.
Most of us are looking for as much as a 60 degree temp differential, I like the fridge to be just below freezing myself, enough so I have to keep the milk on a shelf to keep it from freezing.
When I get meat I usually put it under about a pound of dry ice in a cooler. Also I buy what I need in frozen form if it is available. ( hamburger hot dogs and the like) putting dry ice on top of foods will, freeze it in short order without the mess of regular ice. I would love a better unit however on the is,under I can't justify the price ( especially when the pielter stuff was free) was planning on the 100 watt solar panel regardless. And it is just an experiment after all .
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Old 07-10-2015, 11:45   #344
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Re: Why no Residential Fridges?

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Are you familiar with the efficiency of thermoelectric cooling compared to the alternatives? Have you done the math for the Amp hrs required to cool a single 325ml drink can from your ambient down to 40 degrees?
I believe they say 40degrees below ambient temp.. Not worth having in anyplace that gets above about 75. I had one onboard down in Ft. Myers, Fl.. I had to make ice runs to keep a cold beer on hand.
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Old 07-10-2015, 11:52   #345
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Re: Why no Residential Fridges?

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WADR, you appeared to miss the point of my post. It was my first on this subject, and simply commented on "=" issue in terms of definitions.

Oh, wait, I see, you didn't notice that I am a DIFFERENT Stu.
Sorry! My stupidity. It's funny. I was just reading a post of yours on another subject and thought to myself, I better keep the Stu's straight.
My apologies again.
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