I have a few questions about refrigeration and AC units

In summary, the conversation discusses the similarities and differences between fridges and AC units in terms of their cooling effect and efficiency, and also delves into the factors that affect the amount of condensation on frozen objects.
  • #1
SentinelAeon
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3
I have a few questions about how fridge and AC work, i didn't know where to open this thread, i hope this is ok.

So from what i learned so far, both work in a similar way, effectively moving heat from place #1 to place #2, in effect, "cooling" #1 and heating #2. The main difference (apart from their use) is the moving capacity. My fridge is using about 250W when it is turned on. A home AC can use 2000W. So a few things i am wondering are:

1) Since they move heat, their "cooling" effect is actualy more than the amount of electricity they use. I know this is not a correct way to measure it but i always use Watts because it's easy to compare. 400W cooling effect means that if you put 400W cooling effect near a 400W heating element, they will effectively negate eachother. So is it correct that a fridge and AC, while using X amount of power to run the compressor, it is actualy moving 3-4X the energy ? So if an AC is using 2000W while running, it will actualy be "cooling" the place by 6000-8000W ?

2) How do their efficiency compare if you take the average unit ? For instance, for an experiment let's say you have both AC and a fridge and you make 10 kilograms of ice in a fridge, put it in a room and watch how temperature changes. Then the next day, you use AC to have the same cooling effect that you had with ice. Let's say 10 kilograms gave you X amount of "cooling" Watts and AC gave you the same. If then you checked how much electricity was used 1 way and the other, how would they compare ? Obviously it would take a long time to make 10 kilograms of ice and you would get negligible amount of cooling, i wrote 10 kilograms just as an example. How do this 2 devices compare in efficiency, apart from already said much larger moving capacity and purpose.

3) Is it true that if radiator snake behind the fridge is able to dissipate heat better/faster, the fridge will need less cycles to cool the interior to a set temperature and the "turned on" status of fridge will be shorter ? When the gas is compressed, it heats up. It goes into radiator snake to cool down. The colder the gas is, the more capacity it will have to draw heat from fridge/freezer. Now i know that most heat is actualy transfered through liquid changing into gas but surely temperature of said gas has some small effect also ? In a fridge manual it is said that you must not cover the radiator behind the fridge in order for it to be able to dissipate heat.

4) This is actualy a bonus question. Often i will put something out of the fridge for ice to melt before i can use it. I noticed that frozen material, exposed to room temperature will result in condense appearing on the object - room temperature air is rapidly cooled down therefor its relative humidity will rise until the air can no longer hold the water and it will appear on the object. I compared a few different setups trying to figure out what makes more condense and what makes less of it. I tried different materials, they all held 1 kg of ice. I was interested in how glass/plastic/metal container will affect the amount of water that will condense, also was interested in how smooth and textured surface compared. If anyone could point me in the right direction to get more information, for instance, how important is the temperature of ice, amount of ice, surface material and finish.

This is all for now, i think for those more keen in physics than me it will be really easy to answer and a chance for me to learn some basics i have been wondering about :)
 
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  • #2
1) Yes. An AC drawing 1000 watts of electric power might pull 3000 watts of heat out of the room. That AC will discharge 4000 watts of heat outside.

2) A general rule is that the efficiency is proportional to the temperature difference between the hot side and the cold side. Try search terms heat pump efficiency and Carnot cycle to learn more. The Carnot cycle hits will discuss the effect of temperature difference on the efficiency of a theoretical ideal cycle.

3) The better the job of dissipating heat, the more efficient the cycle, and the less electricity used. You could run some experiments with a Kill-A-Watt meter to study this.

4) Start with search term dew point. If you want to learn more, search psychrometric chart. The standard, and most accurate, method of measuring humidity is with the use of dew point measurement.
 
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Related to I have a few questions about refrigeration and AC units

```html

How does a refrigeration or AC unit work?

Refrigeration and AC units work by transferring heat from one place to another using a refrigerant. The refrigerant absorbs heat from the indoor air as it evaporates in the evaporator coil, then releases that heat outside as it condenses in the condenser coil. This cycle is driven by a compressor and controlled by expansion valves and various sensors.

What are the common types of refrigerants used in AC units?

Common refrigerants include R-22 (Freon), R-410A (Puron), and R-134a. R-22 is being phased out due to its ozone-depleting properties, while R-410A and R-134a are more environmentally friendly options. Newer refrigerants like R-32 and R-1234yf are also being introduced to further reduce environmental impact.

How often should I service my AC unit?

It is generally recommended to service your AC unit at least once a year. Regular maintenance includes cleaning or replacing filters, checking refrigerant levels, inspecting coils and fins, and ensuring that the system is operating efficiently. Regular servicing can help extend the life of the unit and improve its efficiency.

Why is my AC unit leaking water?

Water leakage from an AC unit is usually due to a clogged condensate drain line, a dirty air filter, or low refrigerant levels. The condensate drain line can become blocked by debris, causing water to back up and leak. A dirty air filter can cause the evaporator coil to freeze, and when it melts, the excess water can overflow. Low refrigerant levels can also cause the coil to freeze.

What can I do to improve the energy efficiency of my AC unit?

To improve the energy efficiency of your AC unit, you can regularly clean or replace air filters, ensure that the coils and fins are clean, and seal any leaks in the ductwork. Additionally, using a programmable thermostat to better control the temperature, keeping windows and doors closed when the AC is running, and ensuring proper insulation can all help improve efficiency.

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