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Old 07-10-2015, 11:56   #346
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Re: Why no Residential Fridges?

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Originally Posted by Cadence View Post
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.
That is correct 40 deg f below ambient hense the thermostat to keep it from being to cold most of the time I'm only looking at a 5 to 25 deg f differential also I don't drink alcohol so room temp water is fine for me.
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Old 07-10-2015, 11:59   #347
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Re: Why no Residential Fridges?

Well bottom line is hook it all up and see if it works. Any solar, battery combination will be ultimately deficient in many circumstances, especially when you shoch the refer by overfilling it before a trip or during a period of overcast days. A gen set will provide reliable, surplus power.

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Old 07-10-2015, 12:01   #348
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Re: Why no Residential Fridges?

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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.
Much appreciated from a dimension-less individual!
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Old 07-10-2015, 12:08   #349
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Re: Why no Residential Fridges?

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Originally Posted by Cadence View Post
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.
I'm also toying with the idea of adding a homebuilt heat pipe using propane or r134 as the cooling medium. Would increase the ambient operational temperature range and efficiency.
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Old 07-10-2015, 12:26   #350
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Re: Why no Residential Fridges?

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Originally Posted by newhaul View Post
That is correct 40 deg f below ambient hense the thermostat to keep it from being to cold most of the time I'm only looking at a 5 to 25 deg f differential also I don't drink alcohol so room temp water is fine for me.
It would probably work fine for someone at your lat.. I wouldn't want to really rely upon it for long term perishables. JMHO


PS, beer only needs to get down to 40 so alcohol content really don't mater. Just in case you take up drinking.
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Old 07-10-2015, 15:44   #351
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Re: Why no Residential Fridges?

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Originally Posted by Cadence View Post
It would probably work fine for someone at your lat.. I wouldn't want to really rely upon it for long term perishables. JMHO
Yep, in his location as long as his reefer is very well insulated, he doesn't open it too often and he only puts pre-chilled or frozen produce in it, it could work quite well for him.
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Old 07-10-2015, 19:46   #352
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Re: Why no Residential Fridges?

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Originally Posted by Cadence View Post
It would probably work fine for someone at your lat.. I wouldn't want to really rely upon it for long term perishables. JMHO


PS, beer only needs to get down to 40 so alcohol content really don't mater. Just in case you take up drinking.
Actually back when I did do beer I loved it just a bit slushy when I opened the can. Quit back in 1990 something about 2 fifths of vodka an ocean salvage tug I was assigned to and a typhoon. Worst hangover ever.
As far as fresh produce most of what I do eat comes from a farmers market. I can sniff eem out. ( also best eggs )
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Old 07-10-2015, 21:35   #353
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Re: Why no Residential Fridges?

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Originally Posted by valhalla360 View Post
. detailing the science mistakes he makes.

That is true science. The art of thinking about a subject, creating an understanding of it and then trying in every way possible to disprove the assertion. If a rational "disproof" is not found, the assertion has a scientific merit and remains so until a deeper understanding causes some modification. One of the many reasons why definitions change

Quote:
Originally Posted by StuM View Post
..
However the last one isn't. A baker's dozen has an implied dimension of bread loaves.
...
See how it works?
Clearly you don't buy your wine by the bakers dozen like I do .

Here is how it really works - you two guys and myself retire to a suitable place and open our favourite bevies. My shout first

Once we have sorted out the remaining fundamental questions of the world and everything, we can sort out all the questions on CF and right the wrong...

Cheers and thanks to the OP some some great drift on his thread
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Old 07-10-2015, 21:54   #354
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Re: Why no Residential Fridges?

OMFG!
This thread is still alive. Kidding, as I've enjoyed some of it (I'm with the EE pendants, amp-hrs and all that, was going to mention coulombs and whatever but by the time I read a bit it was all being thrashed out).

And now for something more on topic. When I spotted it I just went 'WTF?'. but who knows. For $25 it might even work, one beer at a time.
It's nothing if not cute...but USB powered?

Mini Portable USB LED PC Refrigerator Fridge

Mini Portable USB LED PC Refrigerator Fridge Beverage Drink Cans Cooling Cooler Warmer - Newegg.com

8. Powered by USB cable with a switch to any USB port located on your PC prior, no batteries required.
9. Dual functions: Cool at 8-10C, heat at 65C, and quick heating and cooling.
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Old 07-10-2015, 22:29   #355
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Re: Why no Residential Fridges?

Quote:
Originally Posted by Tx J View Post
OMFG!
This thread is still alive. Kidding, as I've enjoyed some of it (I'm with the EE pendants, amp-hrs and all that, was going to mention coulombs and whatever but by the time I read a bit it was all being thrashed out).

And now for something more on topic. When I spotted it I just went 'WTF?'. but who knows. For $25 it might even work, one beer at a time.
It's nothing if not cute...but USB powered?

Mini Portable USB LED PC Refrigerator Fridge

Mini Portable USB LED PC Refrigerator Fridge Beverage Drink Cans Cooling Cooler Warmer - Newegg.com

8. Powered by USB cable with a switch to any USB port located on your PC prior, no batteries required.
9. Dual functions: Cool at 8-10C, heat at 65C, and quick heating and cooling.
Hmmm. Guess it's a Peltier cooler, so let's see. We've already determined that a can requires 77 Watt hrs to cool by 20C at 10% Carnot efficiency, so that would be around 40 Watt hrs for 10C. Assume a 2 Amp 5V USB connection. That's 10 Watts. So about 4 hours to cool that can.
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Old 08-10-2015, 01:01   #356
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Re: Why no Residential Fridges?

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Originally Posted by sailorchic34 View Post
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.

They use weight per period of time as an equivilent to GPH. They use total weight as an equivilent to Gallons.

From a scientific point of view they are not equivilent but they correlate nicely and they are very interested in weight because planes are so sensitive to being overweight.

As GPH includes a duration (Hours) I have to include duration otherwise we just have gallons.

"Hour" is a duration. "Per hour" is a rate. When you say X GPH for Y H, you wind up with X*Y G. The weight you measure is gallons not GPH.

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

Sure you can calculate it but not until you add a duration and first convert to Gal. A full 5 gal jerrycan will always weigh the same (pending minor variations for temperature expansion and such). 5GPH doesn't have a weight. 5 GPH for 1 Hour has a weight but 5 GPH for 1 Hour defines a number of Gallons (ie: 5 Gallons)

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

Still waiting for that sweet example.

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.

Agreed but that wasn't the question. The question was how much does your fuel jug weigh when filled. Unless you have a multifuel engine, the fluid is already defined.

We were talking about consistent systems (unless you fill your fuel tank with water or grape juice occasionally).

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.

Again only applicable if you run a gamma ray power system. I've yet to come across a 12 volt battery system that runs on x-rays.

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.

Agreed. Amp or GPH is not a speed (someone else added that to the discussion as an analogy to give the less technically minded something they could visualize. It's a valid analogy but it probably added more confusion to the discussion than help since electrons do have a speed when passing thru a wire but it's a more complicated concept not directly comparable).

It's not a flow either. It's a flow rate.
So still waiting for an example with the weight purely defined by GPH. To get to weight, you need to add a duration to GPH and once you do that, the duration and rate cancel out and it simply becomes gallons that you are providing a weight for.
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Old 08-10-2015, 11:08   #357
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Re: Why no Residential Fridges?

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So still waiting for an example with the weight purely defined by GPH..
I oddly agree with what your saying. But to get a Flow rate, we need a bit more information.

From Wikipedia,
"Volumetric flow rate

In physics and engineering, in particular fluid dynamics and hydrometry, the volumetric flow rate, (also known as volume flow rate, rate of fluid flow or volume velocity) is the volume of fluid which passes per unit time;



Fundamental definition Volumetric flow rate is defined by the limit:[1]


I.e., the flow of volume of fluid V through a surface per unit time t.
Since this is only the time derivative of volume, a scalar quantity, the volumetric flow rate is also a scalar quantity. The change in volume is the amount that flows after crossing the boundary for some time duration, not simply the initial amount of volume at the boundary minus the final amount at the boundary, since the change in volume flowing through the area would be zero for steady flow."


So while I agree with what your saying, we also can know the weight of the fluid per unit time. The question asked was "What is the weight of a GPH" To know what GPH is we must know the volume of the fluid. If we know the volume and fluid type we also know the weight of the fluid flowing allowing for temperature density changes. So yes we can know the weight of a GPH.
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Old 08-10-2015, 11:33   #358
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Re: Why no Residential Fridges?

Quote:
Originally Posted by Tx J View Post
OMFG!
This thread is still alive. Kidding, as I've enjoyed some of it (I'm with the EE pendants, amp-hrs and all that, was going to mention coulombs and whatever but by the time I read a bit it was all being thrashed out).

And now for something more on topic. When I spotted it I just went 'WTF?'. but who knows. For $25 it might even work, one beer at a time.
It's nothing if not cute...but USB powered?

Mini Portable USB LED PC Refrigerator Fridge

Mini Portable USB LED PC Refrigerator Fridge Beverage Drink Cans Cooling Cooler Warmer - Newegg.com

8. Powered by USB cable with a switch to any USB port located on your PC prior, no batteries required.
9. Dual functions: Cool at 8-10C, heat at 65C, and quick heating and cooling.
I need one. That's the jackpot. It better be quick chill or I'll need two.
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Old 08-10-2015, 12:35   #359
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Re: Why no Residential Fridges?

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Originally Posted by StuM View Post
Hmmm. Guess it's a Peltier cooler, so let's see. We've already determined that a can requires 77 Watt hrs to cool by 20C at 10% Carnot efficiency, so that would be around 40 Watt hrs for 10C. Assume a 2 Amp 5V USB connection. That's 10 Watts. So about 4 hours to cool that can.
Stu I do believe that your 4 hour statement may be incorrect due to all of the variables that may or may not be involved such as the.base temperature of the unit the ambient air temperature , the base temperature of the medium being cooled, the amount of air movement in the vicinity of the unit at the time of testing, barametric pressure, as well as relative humidity at the time of testing. Not to mention the rate of caloric exchange that changes at the point of phase change( dependant on starting ambient temperature) and the heretofore unknown actual size of the pielter unit installed in the can cooler unit we are currently discussing.
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Old 08-10-2015, 16:13   #360
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Re: Why no Residential Fridges?

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Stu I do believe that your 4 hour statement may be incorrect due to all of the variables that may or may not be involved such as the.base temperature of the unit the ambient air temperature , the base temperature of the medium being cooled, the amount of air movement in the vicinity of the unit at the time of testing, barametric pressure, as well as relative humidity at the time of testing. Not to mention the rate of caloric exchange that changes at the point of phase change( dependant on starting ambient temperature) and the heretofore unknown actual size of the pielter unit installed in the can cooler unit we are currently discussing.
You are absolutely correct.

It's a rough approximation based on the critical factors:

Amount to be cooled (Amt): One approx 330 mil can.
Degrees to cool (Deg): quoted 8- 10 degrees C.
Carnot efficiency of the unit (Car): 5-8% assumed.

These three factors are sufficient to get a reasonable approximation of the Watt hrs required: Required: Amt x Deg * Car * K where K is the (dimensionless) conversion factor from whatever units you did the calculation in to Watt hours.

USB power supply: approx 2 Amps at 5 Volts maximum for the vast majority of USB sources. Avail= 2 x 5 = 10 Watts

That is sufficient to get a reasonable approximation of the Watts deliverable.

Time = Required/Avail (to the nearest order of magnitude )

Note, as long as it can accept the available 10 Watts. it doesn't matter how big the Peltier unit is. That is all the power that will be available.

"Ye cannae change the laws of physics, Jim"
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