Where can I learn to calculate the need for cooling?

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In summary, the conversation revolves around finding a website that deals with calculating cooling effects for deep freezers, with the main goal being to learn the basics of finding the needed cooling effect based on input values such as food amount, required temperature, room size, and insulation. The conversation also touches on the relationship between heat loss/gain and temperature difference, as well as the linear approximation of heat transfer modes such as conduction and convection. Ultimately, the conversation emphasizes the importance of considering only relevant and significant effects in engineering problem solving.
  • #1
TSN79
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I'm on the lookout for a website dealing with calculation of cooling effects in deep freezers (for food storage and such). The main goal for me is to learn the basics of how to find the needed cooling effect from input values like amount of food, required temperature, room size, insulation, etc. If anyone know any good places I'll be happy :)
 
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  • #2
Google REFRIGERATION CALCULATIONS ...

You could also get empirical information off the back of any freezer...or the owners manual for one...

One thing I can tell you in general: heat loss/gain is directly proportional to the difference in temperature between the ambient and refrigerated area...so keeping something at zero degress in 80 degree ambient takes twice as much cooling (power) as in 40 degree ambient.
 
  • #3
Naty1 said:
One thing I can tell you in general: heat loss/gain is directly proportional to the difference in temperature between the ambient and refrigerated area...so keeping something at zero degress in 80 degree ambient takes twice as much cooling (power) as in 40 degree ambient.

Saywhatnow?
Stefan-Boltzmann's law:
[tex]j^{\star} = \sigma T^{4} [/tex]

Does that look linear in T to you?
 
  • #4
That's only for radiation and a refrigerator is almost entirely conduction and convection and is linear.
 
  • #5
russ_watters said:
That's only for radiation and a refrigerator is almost entirely conduction and convection and is linear.

I know it's for radiation, and at least where I learned to do these kinds of calculations, radiation losses were never neglected.

Conduction is generally treated as if it was linear, but it is not. It's an approximation. The same goes for convection, only it's a worse approximation there.

Using a linear approximation is one thing, stating that reality is linear is something else.
 
  • #6
alxm said:
I know it's for radiation, and at least where I learned to do these kinds of calculations, radiation losses were never neglected.
That's surprising since radiation really is insignificantly small for this case. A tiny fraction of a percent of the heat transfer.
Conduction is generally treated as if it was linear, but it is not.
I've never heard that before - could you provide a source? Here's the typical description: http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/heatra.html
The same goes for convection, only it's a worse approximation there.
Convection is only approximately linear, but in a situation where you have a lot of insulation, the conduction through the insulation is by far the dominant mode of heat transfer. So again, other nonlinear modes are insignificantly small.
Using a linear approximation is one thing, stating that reality is linear is something else.
I think you are being overly pedantic. When someone is looking for 95% accuracy and an effect is .0001% (estimates), it can safely be ignored. This is an engineering question and one of the more important skills in doing an engineering problem is figuring out what you need to consider and what you can safely ignore. If an engineer tries to consider all effects - no matter how small - in all cases, they'd never finish solving a problem.
 

1. What is the purpose of calculating the need for cooling?

The purpose of calculating the need for cooling is to determine the amount of cooling required for a particular space or system. This information is important for designing and implementing efficient cooling systems, as well as for budgeting and cost estimation.

2. What factors are involved in calculating the need for cooling?

Several factors are considered when calculating the need for cooling, including the size of the space or system, the temperature and humidity levels, the type of equipment being used, and the desired level of cooling. Other factors may include insulation, ventilation, and building orientation.

3. Can I learn to calculate the need for cooling on my own?

While it is possible to learn the basics of calculating cooling needs on your own, it is recommended to seek guidance from a professional or take a course in HVAC (heating, ventilation, and air conditioning) design. This will ensure accurate calculations and proper implementation of cooling systems.

4. Are there different methods for calculating the need for cooling?

Yes, there are different methods for calculating the need for cooling. These may include the heat gain/loss method, which takes into account the heat generated by occupants and equipment in the space, and the heat balance method, which considers all heat gains and losses in the space. The specific method used may vary depending on the type of space or system.

5. How can I ensure accurate calculations for cooling needs?

To ensure accurate calculations for cooling needs, it is important to gather all necessary information about the space or system, such as size, location, and equipment being used. It is also important to use the appropriate calculation method and to double-check all calculations for accuracy. Seeking guidance from a professional or taking a course in HVAC design can also help ensure accurate calculations.

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