Ideas for refrigerator door design

[DrClaude]

This seems to corroborate my intuition: most of the cold air escapes in the first ~10 seconds.

 

[OmCheeto]

...
average consumption per day is 1.3 - 1.5 kWh.

How do you know that?

as for the issue of difference of leaving the door open for 5 secs vs 30 secs, pretty sure more heat will enter the compartment the longer the door is opened. heat transfer is a time function after all.
so, the longer the door is opened, the more electricity will be consumed to restore the temperature in the compartment to "normal"

It's actually very interesting, when you graph it:

Door opened for 74 seconds:

Door opened for 5 seconds:

time lag of my detector:

 

[OmCheeto]

This seems to corroborate my intuition: most of the cold air escapes in the first ~10 seconds.

I was involved in an argument a while back regarding the term "most".
I very much liked marcus's answer to the question:

I certainly agree his wording ("most" of the mass) was ill-advised even if technically correct. "Most" suggests a substantial majority (at least to me and probably to most people) rather than a very slim majority like 50.1% versus 49.9%. Gives the wrong impression --- mostly a matter of nuance.

I propose, in a most off topic manner, that someone start a poll, in another thread, as to how we should scientifically define the term "most".
Personally, I like the 1/√2

 

[OCR]

Yes, I meant how much negative heat is lost

... We can go with that... it certainly sounds reasonable to me...[COLOR=#black].[/COLOR]

 

[OCR]

This seems to corroborate my intuition: most of the cold air escapes in the first ~10 seconds.

I'll bet you meant...

: most of the cold negative hot air escapes in the first ~10 seconds.

[COLOR=#black].[/COLOR]... Can we go with that ?... it certainly sounds reasonable to me...[COLOR=#black].[/COLOR]

 

[NTL2009]

"out of town"?
That doesn't happen very often for me.
But your's is a very good idea.

Though, it may extend this experiment into the "months" range.

But, as an oldster, I'm getting somewhat used to long range experiments.

ps. I will pay someone actual currency, if they can determine which continent jtbell's image is from...
on Tuesday, of course.

If you are using a Kill-a-watt meter, or equiv, couldn't you compare overnight kWh to daytime kWh? You'd need to manually log the kWh and time before bed and in the AM, but a week's worth of data should average out the defrost cycles.

 

[Trainee Engineering]

How do you know that?

using Kill A Watt. I plug the Kill A Watt at 1AM 4 days ago, and I read everyday at 1AM.
as for your graph, this is very interesting. the temp indeed increase more as more time goes by, but the significant loss is at the first 10 seconds. I guess that's the cold air leaking out, but negative heat from solids (stuff actually inside fridge) takes longer to transfer out to environment.

 

[OmCheeto]

If you are using a Kill-a-watt meter, or equiv, couldn't you compare overnight kWh to daytime kWh? You'd need to manually log the kWh and time before bed and in the AM, but a week's worth of data should average out the defrost cycles.

@T=180 hours(7.5 days), the energy consumed was 27.69 kwh, which corresponds to an average power of 152 watts.

using Kill A Watt...

Great devices!
I've learned a lot about my refrigerator from the data I've collected over the last week.
One peculiarity during this experiment, was that my refrigerator operated at between 210 & 228 watts.

It wasn't until I accidentally triggered it to turn on, and start recording data every minute, that I found out why.

For some reason, instantaneous power consumption goes down with time, after the compressor has started running.

And I think I may have captured the defrost cycle:

"watts rough" is the the wattage between readings
"watts smooth" is the wattage from time = 14 hours

Entertaining numbers:

On or about t=20 hours, I went out for lunch, in an attempt not to booger my "DON'T OPEN THE REFRIGERATOR DOOR!" experiment, and spent $7.35 for lunch.
From my extrapolation of data so far, it costs me $13.55 to run my refrigerator for a month.​

Conclusion: Eating out, even at Taco Bell, is kind of expensive.

 

[Trainee Engineering]

@T=180 hours(7.5 days), the energy consumed was 27.69 kwh, which corresponds to an average power of 152 watts.

Great devices!
I've learned a lot about my refrigerator from the data I've collected over the last week.
One peculiarity during this experiment, was that my refrigerator operated at between 210 & 228 watts.
View attachment 112711
It wasn't until I accidentally triggered it to turn on, and start recording data every minute, that I found out why.

View attachment 112712

For some reason, instantaneous power consumption goes down with time, after the compressor has started running.

And I think I may have captured the defrost cycle:
View attachment 112714
"watts rough" is the the wattage between readings
"watts smooth" is the wattage from time = 14 hours

Entertaining numbers:

On or about t=20 hours, I went out for lunch, in an attempt not to booger my "DON'T OPEN THE REFRIGERATOR DOOR!" experiment, and spent $7.35 for lunch.
From my extrapolation of data so far, it costs me $13.55 to run my refrigerator for a month.​

Conclusion: Eating out, even at Taco Bell, is kind of expensive.

hmm, $13.55, may I have the kWh? because price per kWh from one country to another is different, but kWh remains constant anywhere. a bit curious about the energy consumption when door not opened.

 

[Buckleymanor]

I would argue that transparency is actually not desirable for kitchen fridges, from a user's perspective.

Try this.http://www.explainthatstuff.com/electrochromic-windows.html

 

[OmCheeto]

hmm, $13.55, may I have the kWh? because price per kWh from one country to another is different, but kWh remains constant anywhere. a bit curious about the energy consumption when door not opened.

This can be calculated with the the data from the first line of mine that you quoted;" ...which corresponds to an average power of 152 watts"
152 watts * 24 hours / 1000 = 3.65 kwh/day

average consumption per day is 1.3 - 1.5 kWh.

So your refrigerator uses less than half what mine does.

When I discovered that, I looked into purchasing the fancy refrigerator rbelli1 referenced earlier:

http://www.samsung.com/us/explore/family-hub-refrigerator/

Already a thing!

BoB

Cost: $5,600

I did some fancy maths and discovered it would take about 59 years for the refrigerator to pay for itself.
I decided against the purchase.

 

[rbelli1]

Cost: $5,600

I was just saying it was a thing. I had no idea what it cost. Please don't buy it and encourage them. The couple hundred dollars for the parts gets them a few thousand extra in product cost.

For some reason, instantaneous power consumption goes down with time, after the compressor has started running.

The temperature difference decreases over time with the operation of the cooling device. The power needed to operate the compressor decreases with a decrease in temperature differential. Quod erat demonstrandum.

BoB