5 ms·

"Vertical doors in refrigeration devices are inherently inefficient. As soon as we open a vertical fridge door – the cold air escapes, simply because it is heav

"Vertical doors in refrigeration devices are inherently inefficient. As soon as we open a vertical fridge door – the cold air escapes, simply because it is heavier than the warmer air in the room." Okay, so the author proposes that the thermal losses from the cold air being replaced with ambient air make up for the hundreds of extra kWh/year consumed by a vertical fridge. While chest freezers typically have better thermal insulation and larger evaporators than fridges... So shouldn't we be comparing a chest fridge to a vertical fridge with a comparable insulation system and condenser/evaporator capacity before declaring that lower air losses are the reason chest fridges work better?

vanderZwan 10y ago
> In 2004 I became really curious just how efficient a “chest fridge” can be. Pretty sure you couldn't easily get a chest fridge back then. I know, I looked for one a few years later.
- deleted 10y ago
  [deleted]
- cptskippy 10y ago
  What constitutes a chest fridge to you? A Google image search on the term yields exactly what I expected and those have been around as long as I can remember (30+ years).
  - vanderZwan 10y ago
    Something I can buy in a store or have delivered to my house and isn't an order of magnitude more expensive because it's "design"
    - cptskippy 10y ago
      So you're saying that "design" chest fridges are a new occurrence? I'm thoroughly confused as to what you're trying to say. Chest fridges are not new and have been around for decades. If by "design" you mean designer, then ok maybe designer chest fridges are a new thing. I wouldn't know because I've never actually seen one. Most people keep chest fridges in their basement or garage and wouldn't care if it's designer or not.
      - vanderZwan 10y ago
        > Chest fridges are not new and have been around for decades. I'm saying that they might "have been around", but they weren't in any of the stores that sold fridges when I went looking for them. The only thing resembling a chest fridge I have seen in real life in the last decade was some kind of fancy designer-drawer in an upper-class house.
URSpider94 10y ago
We know the important fact already -- the chest fridge consumes much less power than an upright. The author has demonstrated that clearly. His reasoning as to why that's true is really secondary, almost irrelevant.
- dpark 10y ago
  > His reasoning as to why that's true is really secondary, almost irrelevant. It's really not. I'd wager that the vast majority of the efficiency is due to the lack of condensation control rather than the fact it's in a chest orientation.
rebootthesystem 10y ago
This is nonsense (what the author said, not you). The heat capacity of the air contained in a fridge is insignificant when compared to that of the contents. Opening and closing the door occasionally has almost no effect. The two important variables are thermal mass and insulation.
- Xylakant 10y ago
  The relative heat capacity of the air and the content is irrelevant. The thermal mass of the content is irrelevant as well since it's the same for a chest fridge and an upright fridge. The relevant comparison is how much heat escapes through the walls of the fridge relative to the heat loss via escaping air. Since fridge insulation has improved massively in the last decade that might actually be a significant share. The paper also mentions that an imperfect seal (due to imperfect closing or plain wear) on a vertical door leads to a constant trickle loss, while it does have much less of an effect on a chest freezer.
  - joezydeco 10y ago
    Consumer fridges also consume a lot more energy in the interest of keeping humidity (and, subsequently, frost) out of the compartment. They also run defrost cycles with heaters to keep the evaporators from icing over and locking up the system. That lack of humidity control is what builds up a secondary layer of insulating frost/ice inside a normal chest freezer. It results in that "cleaning flow" of water inside the chest fridge, which doesn't sound as sanitary or healthy as the author proclaims once it builds up to a significant level. "The amount of condensation depends how much moisture is in the ambient air and how often and how vigorously we open and close the fridge lid." Wait. I thought less to no ambient air mixed into a chest fridge cavity according the author.
    - dpark 10y ago
      > Consumer fridges also consume a lot more energy in the interest of keeping humidity (and, subsequently, frost) out of the compartment. Yep. I'm pretty sure if you had an upright fridge built to modern standards but cooled conductively (convectively?) it would be about as efficient as the chest fridge here, but it would also have the same condensation problem.
david-given 10y ago
Hm. Air has a heat capacity of approximately 1 kJ/(kg K). Its density is 1.2 kg/m^3. I don't know how big the fridge is, but someone elsethread said 600 litres, so I'll use that. (And assume that it's empty.) That's 0.6 m^3, and so has a mass of ~700 grams. Assuming ambient air temperature of 20°C and a fridge temperature of 4°C, that's a temperature delta of 16 K. Therefore the energy required to chill that air is 0.6 * 16 = ~10 kJ. 10 kJ is 0.003 kWh. Electricity costs about 20 US cents per kWh. Assuming a factor of ten fudge factor for cooling efficiency, then we can be reasonably confident that opening and closing the fridge would cost less than 0.03 * 0.20 = 0.006 dollars = 0.6 cents. That's not a lot. Does anyone have any figures on how good fridge insulation is, for comparison?
- CompelTechnic 10y ago
  Don't forget that refrigerators have a coefficient of performance greater than 1. So it takes less than 1 Joule of work to cool the interior by 1 Joule.

vanderZwan 10y ago

> In 2004 I became really curious just how efficient a “chest fridge” can be. Pretty sure you couldn't easily get a chest fridge back then. I know, I looked for one a few years later.

deleted 10y ago
[deleted]
cptskippy 10y ago
What constitutes a chest fridge to you? A Google image search on the term yields exactly what I expected and those have been around as long as I can remember (30+ years).
- vanderZwan 10y ago
  Something I can buy in a store or have delivered to my house and isn't an order of magnitude more expensive because it's "design"
  - cptskippy 10y ago
    So you're saying that "design" chest fridges are a new occurrence? I'm thoroughly confused as to what you're trying to say. Chest fridges are not new and have been around for decades. If by "design" you mean designer, then ok maybe designer chest fridges are a new thing. I wouldn't know because I've never actually seen one. Most people keep chest fridges in their basement or garage and wouldn't care if it's designer or not.
    - vanderZwan 10y ago
      > Chest fridges are not new and have been around for decades. I'm saying that they might "have been around", but they weren't in any of the stores that sold fridges when I went looking for them. The only thing resembling a chest fridge I have seen in real life in the last decade was some kind of fancy designer-drawer in an upper-class house.

URSpider94 10y ago

We know the important fact already -- the chest fridge consumes much less power than an upright. The author has demonstrated that clearly. His reasoning as to why that's true is really secondary, almost irrelevant.

dpark 10y ago
> His reasoning as to why that's true is really secondary, almost irrelevant. It's really not. I'd wager that the vast majority of the efficiency is due to the lack of condensation control rather than the fact it's in a chest orientation.

rebootthesystem 10y ago

This is nonsense (what the author said, not you). The heat capacity of the air contained in a fridge is insignificant when compared to that of the contents. Opening and closing the door occasionally has almost no effect. The two important variables are thermal mass and insulation.

Xylakant 10y ago
The relative heat capacity of the air and the content is irrelevant. The thermal mass of the content is irrelevant as well since it's the same for a chest fridge and an upright fridge. The relevant comparison is how much heat escapes through the walls of the fridge relative to the heat loss via escaping air. Since fridge insulation has improved massively in the last decade that might actually be a significant share. The paper also mentions that an imperfect seal (due to imperfect closing or plain wear) on a vertical door leads to a constant trickle loss, while it does have much less of an effect on a chest freezer.
- joezydeco 10y ago
  Consumer fridges also consume a lot more energy in the interest of keeping humidity (and, subsequently, frost) out of the compartment. They also run defrost cycles with heaters to keep the evaporators from icing over and locking up the system. That lack of humidity control is what builds up a secondary layer of insulating frost/ice inside a normal chest freezer. It results in that "cleaning flow" of water inside the chest fridge, which doesn't sound as sanitary or healthy as the author proclaims once it builds up to a significant level. "The amount of condensation depends how much moisture is in the ambient air and how often and how vigorously we open and close the fridge lid." Wait. I thought less to no ambient air mixed into a chest fridge cavity according the author.
  - dpark 10y ago
    > Consumer fridges also consume a lot more energy in the interest of keeping humidity (and, subsequently, frost) out of the compartment. Yep. I'm pretty sure if you had an upright fridge built to modern standards but cooled conductively (convectively?) it would be about as efficient as the chest fridge here, but it would also have the same condensation problem.

david-given 10y ago

Hm. Air has a heat capacity of approximately 1 kJ/(kg K). Its density is 1.2 kg/m^3. I don't know how big the fridge is, but someone elsethread said 600 litres, so I'll use that. (And assume that it's empty.) That's 0.6 m^3, and so has a mass of ~700 grams. Assuming ambient air temperature of 20°C and a fridge temperature of 4°C, that's a temperature delta of 16 K. Therefore the energy required to chill that air is 0.6 * 16 = ~10 kJ. 10 kJ is 0.003 kWh. Electricity costs about 20 US cents per kWh. Assuming a factor of ten fudge factor for cooling efficiency, then we can be reasonably confident that opening and closing the fridge would cost less than 0.03 * 0.20 = 0.006 dollars = 0.6 cents. That's not a lot. Does anyone have any figures on how good fridge insulation is, for comparison?

CompelTechnic 10y ago
Don't forget that refrigerators have a coefficient of performance greater than 1. So it takes less than 1 Joule of work to cool the interior by 1 Joule.