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Ideas for refrigerator door design

  1. Jan 30, 2017 #1
    Hi all,

    I just want to throw some ideas and get feedback from the community on refrigerator door design.
    If anybody notices in supermarkets, etc, the frozen food are kept in glass-doored refrigerators. the prupose of the glass door is so the customers can see if the stuff they're looking is behind door number X, so, no opening door and got nothing, thus, increasing the temp in the compartment for nothing, where this would mean need to consume extra electricity to decrease the temp back to where it was for nothing.

    now, the problem with this is that glass, even if it's not a good conductor, it still conducts heat. meaning, it heat from outside will still seep into the compartment, even when it's closed. I have 2 ideas:

    1. in normal fridge in houses, we have 2 solid (non transparent) doors, top and bottom. I suggest we change this to a transparent material (glass, plastic, etc), but it a layered design. so the door is something like glass - vacuum - glass. the vacuum between glass is to prevent heat transfer from outside to inside compartment.

    2. create more compartments in each section. so, right now, there are only 2 sections in a fridge --> freezer and refrigerator. normally, refrigerator section is quite big, so, I think it's better to further divide it to several compartment (tray level), so each tray is one separate compartment, so, when we open the compartment, we dont increase the temp for the other compartments.

    the main objective is of course to save electricity, in tandem with inverter tech

    any input ?
    thanks
     
    Last edited by a moderator: Jan 30, 2017
  2. jcsd
  3. Jan 30, 2017 #2
    You want to see through the glass what is in the fridge?
     
    Last edited by a moderator: Jan 31, 2017
  4. Jan 30, 2017 #3
    correct, see through the glass door what's inside. that way, less time looking for the item, which means less time the door is open, which would mean, less heat entering the compartment, which means less electricity to cool the temp down after opening the compartment door.
    secondly, prevent as much heat as possible from entering into the compartments
     
    Last edited by a moderator: Jan 31, 2017
  5. Jan 30, 2017 #4
    I suppose a comparison of the amount of time the door is open whether it ( the door ) is transparent vs non-transparent would be a place to start.
    That would have to be done to see if type of door is a determining factor for the behavior of people, which includes those who who actually do like to open the door and stand there looking into the fridge.
    And you would have to determine whether a transparent door would make retrieving items, or placing them into the fridge a time saver for the user and for electrical usage,
    A table of time spent locating an item, retrieving the item, placing an item would quantify the results.

    You could then record the amount of electricity used for both cases, if you find a substantial difference in the time the door is open.
     
  6. Jan 30, 2017 #5

    russ_watters

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    Have you looked into how windows are designed?
     
  7. Jan 30, 2017 #6
    I would argue that transparency is actually not desirable for kitchen fridges, from a user's perspective.
     
  8. Jan 30, 2017 #7

    billy_joule

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    Well domestic fridges with glass doors are already available so presumably they're desirable to some consumers.

    Take a closer look at the supermarket next time, all the fridge doors are already double glazed. If they weren't, condensation would obscure the products and defeat the purpose of the glass doors.
    In my country, most appliances have compulsory energy efficiency ratings with an annual running cost, glass door fridges cost a lot more to run than solid door fridges so that's probably one reason why market share is low.

    An idea i quite like is having a small access port in domestic fridge doors, just large enough to grab the milk or butter while avoiding the energy loss associated with opening the door.
    images?q=tbn:ANd9GcRSPwoN4QRSNT7j5UmHFpX99j8Eb_xqIQmDwVXX9QSKNpZiUrj1s3XNDVLL4A.jpg

    The door in door fridges are also an interesting idea;

    images?q=tbn:ANd9GcRjL54tDqpoSqn3lUJsKmLdiVqx5yQsh3k_5xYcmJlRkboJk-5r71HbaAdDVQ.jpg
     
  9. Jan 30, 2017 #8

    anorlunda

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    There are at least two simpler or less expensive ways I can think of to reduce energy losses when the refrigerator door is open.
    They are both based on the principle that most of the energy loss comes when cold heavier air spills out onto the floor, and is replaced by warmer lighter air from above.

    1) Make a horizontal refrigerator where the door opens from the top. That has a convenience cost.

    849409.jpg

    2) Use a plastic strip curtain inside the refrigerator to slow down and reduce the spillage of cold air when the door is open.
    mainpic.jpg

    An engineer in training should know that before presenting an innovative idea to management, that he should do some engineering analysis. For example,
    • Where does a typical refrigerator's energy go? We are interested in the fraction of that energy that could be saved, and how much that is worth to the consumer in terms of cost savings per year.
    • How much would the idea cost in design and manufacturing?
    • How would the design affect customer service and warranty costs? (two doors = twice as many door-related problems)
    • What is the cost/benefit ratio to the manufacturer? to the consumer?
    • How would it impact consumer convenience?
    • What similar ideas have been tried and rejected in the past by other manufacturers?
    It is fine to filter ideas first with simple questions, "How much energy would the split door save?" If the answer comes back, "very little." then there is no need to investigate the other questions.
     
  10. Jan 30, 2017 #9
    The first thing one should probably do is attach an amp meter to the fridge power cable, and see how much additional power is consumed after a normal access to the fridge. Alternatively, you could measure the temperature inside the fridge, and see how long it takes to go back to operating temperature.

    Another, wild idea would be to do something like stores do when they blow warm air from the ceiling when you enter the store, in order to prevent cold air from entering. Maybe you could push cold air out when the door is opened!
     
  11. Jan 30, 2017 #10

    Stephen Tashi

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    Cameras inside the fridge and an LCD display on the outside of the door - which could show reminder messages when the owner wasn't browsing the contents of the refrigerator.
     
  12. Jan 30, 2017 #11

    rbelli1

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  13. Jan 30, 2017 #12

    OmCheeto

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    According to my calculations, I would have to open and shut my refrigerator door 36 times before it would cost me a penny's worth of electricity.

    Based on:
    the volume of my fridge: 0.37 m^3
    difference in air temperature: 17.8K
    my last electric bill: $0.122/kwh
    and all those universal constants​

    Although saving energy is always a good idea, I like to do a tad bit of maths before I invest too much money in things that will save me virtually nothing.

    This sounds like a very good experiment. I purchased a Kill-A-Watt meter last summer. I think it will pay for itself in what it's made me aware of.
    My above calculations were based solely on the heat capacity of air. Heat losses, I am sure, are higher, due to both convective and radiant energy transfers. Though, I doubt they will be significant. But, you can never be sure. The experiment has started.

    And right off the bat, I notice a problem. My refrigerator has a power factor of 0.5
    Volts: 121.4
    Volt Amps: 413
    Watts: 208
    PF: 0.50​

    I may have to look into this. Although I may not pay for un-utilized current flow, I have a feeling it makes the entire grid less efficient, which I would imagine we are all paying for.
     
  14. Jan 31, 2017 #13
    I suspect most homeowners don't want to have the contents visible. They'd rather see a nice enameled or stainless surface, not a bunch of drippy bottles and Tupperware full of yesterday's beans.
     
  15. Jan 31, 2017 #14
    ok, so there are 2 issues here:
    • see through fridge door --> already a concept by samsung (pretty sure it's not on sale yet, or is it?). the reason I brought this point up is that I've observed the behavior of normal people when opening the fridge :
      1. open door
      2. aristotle's pose when pondering which leftover food one wants to eat now
      3. turn the fridge upside down in an attempt to locate said leftover
      4. close door (#1 to #4 takes around 10 seconds)
    • multi compartment --> now, I think an experiment is in order. @OmCheeto , you're already conducting experiment? lets compare data later.
    I'm in asian country where electricity is quite high and dry season can be really hot and humid, so I dont know if this will affect the speed of heat transfer when door is opened.
     
  16. Jan 31, 2017 #15

    OmCheeto

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    Preliminary results are inconclusive:
    I either opened my refrigerator door 356 times last night, or
    I have not collected enough data, or
    I have not accounted for all significant variables​

    Thank you for mentioning humidity. As everyone knows, warm humid air will condense on everything in the refrigerator. This may be significant. I will attempt to ascertain the humidity in my house.
     
  17. Jan 31, 2017 #16
    just want to clarify, I meant was quite expensive
     
  18. Jan 31, 2017 #17

    berkeman

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    Sorry if this has been already suggested (TLDR), but do you have a barcode reader in your door? :smile:
     
  19. Feb 1, 2017 #18
    in my door? as in fridge door? I dont think so. why?
     
  20. Feb 1, 2017 #19
    As I mentioned in post #4 you will have to do obtain some data, if your premise that a glass door will save electricity in the long run.


    That is your biggest issue here.
    Just making the assumption is not enough. You have to back it up.

    With a glass door, all the convenient placeholders will be lost for eggs, milk, etc.
    Final result could be a larger fridge with more surface area to lose "coolness", so the gain in electrical usage can end up negative just from that.
     
  21. Feb 2, 2017 #20

    OmCheeto

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    Yes! It would be interesting to see how other people approach this problem.
    Mostly, I've been trying to not open my refrigerator at all. It is more difficult than one would expect.
    So far, I've accidentally opened the door 4 times, and 4 times on purpose, for a total door open time of 30 seconds.

    I've now collected 48 hours worth of data, and have come to no conclusions. I will probably do some more tests tomorrow.

    Things I originally overlooked:
    The unit is a frost free type, so it must have a defrost cycle. I have not determined how much power that consumes.

    I have a feeling that when I'm done, I will have discovered that this is more of a psychology test, than a science experiment.

    I think I will post a sign on my refrigerator:

    Are you really hungry,
    or just bored?

     
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