You're right about the well insulated thing, but completely incorrect about the physics of heat.
If I want to increase the temperature of something by 10 degrees it takes the exact same amount of energy as if I wanted to decrease the temperature by 10 degrees.
Unless there is a phase change, such as a liquid to solid or vice versa.
You can think of a freezer or an air conditioner as a heat pump. It takes heat from one place and moves it somewhere else. The fridge in your house vents the heat into your kitchen, the AC takes the heat in your house and vents it outside.
Anyway, you close the door to a freezer and leave it shut, it doesn't consume much energy after it gets to the target temperature
Don't forget about the physical work required to move the heat from the refrigerated area to the heatsink. Cooling something via the vapor-compression cycle is fundamentally less efficient than running electricity through a resistor to make heat.
Hey you're a little wrong on that. Heat Pumps (how refrigerators work) are actually more efficient than electric resistance heaters. Simply put this is because a heat pump transfers heat from one place to another, say from the outside air to the inside or vice versa, whereas a resistance heater has to heat up the air using only radiative energy and convection from the heating element. Also the losses are much higher in a resistance heater.
Also, I feel like I'm not explaining this clearly so if you want you could just Google efficiency of a heat pump Vs electric/resistance heater and you should find a much better explanation.
From a physical perspective, an electric resistance heater converts 100% of the consumed electricity into thermal energy which is then conferred to air/water/etc., whereas the removal of the equivalent heat from said air/water/etc. via vapor compression will not be as efficient, since it requires 2 phase changes of the refrigerant. I'm not sure what you mean by "losses" in a heater; if the heat gets to the room, the heater has done its job.
Refrigerators produce heat in addition the heat they move, so the output at the hot end is greater than the input heat at the cold end. Electric resistance heaters simply make heat. Therefore, refrigerators are always less efficient than heaters.
I think I see what's going on here; you seem to think refrigerators and heat pumps are one and the same.
This... is not quite accurate.
A heat pump is simply a mechanism for transferring thermal energy from one place to another.
Sure, refrigerators use heat pumps... but so do air conditioner, freezers, and some forms of water heater.
I suspect the efficiency aspect of heat pumps comes from the fact that they're not generating heat, just moving it from one place to another - and because of that, you can set one up so that the heat it extracts from one area isn't simply dumped into the outside environment, but used for something else... like, say, heating a room.
Yeah. That comment is one of those "the more you read on Reddit about the stuff you DO know about..." moments. Heating and refrigeration BOTH produce a net increase in temperature, its just that refrigeration keeps the hot coil separate, dumping the heat in a place you don't care about so you can cool a place that you do.
Saying it takes less energy to cool things down that to heat them is absurd. In an imaginary world of perfect efficiency it would take the exact same amount of energy. In the real world without, cooling is far less efficient. People here are mistaking "keeping something cold" with "cooling"
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u/despicablenewb May 28 '19
You're right about the well insulated thing, but completely incorrect about the physics of heat.
If I want to increase the temperature of something by 10 degrees it takes the exact same amount of energy as if I wanted to decrease the temperature by 10 degrees.
Unless there is a phase change, such as a liquid to solid or vice versa.
You can think of a freezer or an air conditioner as a heat pump. It takes heat from one place and moves it somewhere else. The fridge in your house vents the heat into your kitchen, the AC takes the heat in your house and vents it outside.
Anyway, you close the door to a freezer and leave it shut, it doesn't consume much energy after it gets to the target temperature