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Topic: USB Beverage cooler (Read 1 time)previous topic - next topic

PrescottJoule

Jul 13, 2015, 04:06 am
Beverge Cooler
I saw this and was wondering the best way to build my own. How do you think it is cooled? It would seem it uses a peltier because it is referred to as a "thermoelectric cooler" elsewhere and the similar model can heat as well as cool. Thanks

jremington

#1
Jul 13, 2015, 04:14 amLast Edit: Jul 13, 2015, 04:18 am by jremington
Quote
you insert a warm soda and put it in the mini fridge overnight, in the morning you'll have a warm soda.
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Maybe five degrees cooler than ambient room temperature. An absolute waste of money.
The device consumes 10 watts. It is impossible to cool effectively with such low power and so little insulation. 12 volt thermoelectric beverage coolers for autos have decent insulation and typically consume about 100 watts.

1:1

#2
Jul 13, 2015, 05:37 am
I found one of these at work - I concur, practically useless - and it stands to reason that is why I found it abandoned.

However the base does get cold if that interests you, but the laws of thermodynamics/heat transfer work very strongly against the intended purpose.
The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

1:1

#3
Jul 13, 2015, 05:38 am

'Peltier effect'
The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

PrescottJoule

#4
Jul 13, 2015, 05:52 am
The reason I want to build one myself IS the negative reviews. I realize good insulation would required for such a low current model to do anything meaningful.

jremington

#5
Jul 13, 2015, 04:44 pm
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I realize good insulation would required for such a low current model to do anything meaningful.
Excellent.

There is another factor: heat is energy.

If the insulation is perfect, 4 watts removed in 1 second will reduce the temperature of 1 gram (1 cubic centimeter) of water by 1 degree Celsius.

Peltier devices are typically around 5% efficient, which means you need 20 watts of electrical energy to achieve 1 watt of cooling.

DVDdoug

#6
Jul 13, 2015, 06:10 pm
Quote
The reason I want to build one myself IS the negative reviews. I realize good insulation would required for such a low current model to do anything meaningful.
Standard USB 2 ports are rated for 1/2 Amp (2.5W).    USB 3 ports are rated for 0.9 Amps (4.5W).

I suggest you have a "plan B" with a better power source just in case you can't get nearly infinite insulation and in case you don't have a nearly infinite amount of time to cool the drink.

DrAzzy

#7
Jul 13, 2015, 07:23 pm
It is impossible to make an effective beverage cooler that is powered off of a USB power supply - the laws of physics dictate that more power than USB can supply is needed. By a lot - that 5% efficiency is a killer.
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PrescottJoule

#8
Jul 13, 2015, 10:07 pm
I don't plan on powering the final unit through USB, but i do want it to act as a small fridge.

1:1

#9
Jul 14, 2015, 01:16 am
Sorry, I didn't realise you adjust said peltier effect in your original post.

Are there no instructables or otherwise?

--------
Heat is energy ?

Watts >> joules/s >> rate of energy transfer

The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

jremington

#10
Jul 14, 2015, 04:12 am
Quote
Heat is energy ?

Watts >> joules/s >> rate of energy transfer
Yep, as stated, 4 watts for one second is 4 joules (~ 1 cal) of heat energy removed.

A more accurate conversion is 4.184 joules per cal.

1:1

#11
Jul 14, 2015, 10:18 am
Ugh,

Typing on a mobile has made a mess of my last post ...

also I was trying to point out the unit / rate difference between heat and heat transfer - but the question mark doesn't help
The XY problem:  "the over-use of one line responses that simply link though to websites that describe the XY problem"

jremington

#12
Jul 14, 2015, 04:17 pm
One watt (rate of heat transfer) times one second = one Joule (of heat transferred).

PrescottJoule

#13
Jul 15, 2015, 10:51 pm
I got a response from the distributor claiming it would take to long for them to test how fast they cool, I guess they don't know how to ask the manufacturer for part numbers.

raschemmel

#14
Jul 16, 2015, 07:47 pm
Google Search: Peltier Cooler Response Time

From what I can tell, and from personal experience, the response of the wafer is one factor, the volume of the cooler is the other factor. The first is almost instantaneous
(fractions of a second), the second factor depends on the size of the wafer with respect to the surface area of the cooler walls (ie: % of cooler surface area covered by peltier wafers)

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