# Calculate Time for Fridge to Cool 1m3 Air from 20°C to 3°C

• Jimmy234
In summary, the conversation discusses calculating the time it takes for a fridge to cool 1m3 of air from 20°C to 3°C while running at 200 watts. The equation T = E/P is used, but more data is needed. The efficiency of the fridge, temperature difference, and other factors such as the presence of food in the fridge can affect the cooling time. It is suggested to use assumptions and equations to estimate the time, but the specific design and efficiency of the fridge will ultimately determine the cooling time.

#### Jimmy234

Hi Guys

I have a relatively simple question (I think!),

I am trying to calculate the amount of time it takes for a fridge to cool 1m3 of air from 20°C to 3°C while running a fridge's compressor at 200 watts

I have calculated this using T = E/P

From this I am trying to work out the time this 1m3 of air will take to go through the piping system within the fridge using;

Flow rate = Volume / Time

I'm having trouble with putting all of this into practice, any help would be appreciated.

Jim

Without more data, this won't work.
I guess the air is not going through the compressor, it gets cooled with a separate cooling cycle? Either way, you'll need data how efficient the fridge is, this will also depend on the temperature difference.

Air doesn't have a very high specific heat capacity, so I'm thinking you'll find that a general refrigerator will be able to cool a cubic meter volume pretty fast. However, if you take ainto account a body of food in it (especially one with high water content, even a gallon of milk) it will take significantly longer to cool.

If you make some assumptions about the typical efficiency of a fridge (maybe using the refrigeration coefficient of performance equations), you would be able to get a rough estimate of the time involved.

You can't calculate it from thermodynamic principles - it depends on the design and efficiency of the particular fridge. (How fast does the fan move the air, what's the surface area of the cooling coils, what's the temperature of the room, etc.)

If this is more in the nature of a test question, perhaps you can assume ideal efficiency, but you still need the room's temperature.

## 1. How long does it take for a fridge to cool 1m3 of air from 20°C to 3°C?

The time it takes for a fridge to cool 1m3 of air from 20°C to 3°C can vary depending on factors such as the size and efficiency of the fridge, the initial temperature of the air, and the surrounding temperature. On average, it can take anywhere from 2-6 hours for a fridge to cool 1m3 of air from 20°C to 3°C.

## 2. What is the formula for calculating the time it takes to cool air in a fridge?

The formula for calculating the time it takes to cool air in a fridge is: Time = (1m3 x Specific Heat Capacity x Density x change in Temperature) / (Cooling Capacity x Efficiency)

## 3. How does the specific heat capacity of air affect the cooling time of a fridge?

The specific heat capacity of air is the amount of energy needed to raise the temperature of 1m3 of air by 1°C. The higher the specific heat capacity, the more energy is needed to cool the air, resulting in a longer cooling time for the fridge.

## 4. Can the time it takes for a fridge to cool 1m3 of air be shortened?

Yes, the time it takes for a fridge to cool 1m3 of air can be shortened by increasing the efficiency of the fridge or by lowering the initial temperature of the air. Keeping the fridge well-stocked can also help maintain a lower temperature and decrease cooling time.

## 5. Are there any other factors that can affect the cooling time for a fridge?

Yes, other factors such as the size and placement of food items in the fridge, the frequency of opening and closing the fridge door, and the ambient temperature of the room can also affect the cooling time for a fridge. It is important to consider all these factors when calculating the time for a fridge to cool 1m3 of air.