- #1
mknott
How do you calculate the time to cool down a 60'X60'X50' building filled with outside air at 96°F to 65°F with 14,250 CFM of supply air at 55°F?
This is a surprisingly difficult question because you have to consider the thermal mass of the building and it's contents and how efficient the airflow is. If you just want a rough estimate of how fast it can cool the air, Newton's law of cooling (or the dilution/mixing equation) can be solved numerically in a spreadsheet in about 30 seconds...mknott said:How do you calculate the time to cool down a 60'X60'X50' building filled with outside air at 96°F to 65°F with 14,250 CFM of supply air at 55°F?
Is this homework or a real life situation? Either way, we like to teach here rather than spoonfeed, so you should be able to take partial answers and nudges in the right direction and move them along yourself...mknott said:So, what is the Newton's Law of Cooling equation and how would you solve this problem with it?
A weighted average is the amount of air at one temperature plus the amount of air at another temperature divided by the total amount of air.mknott said:I'm not sure how to calculate weighted average either.
Just use the weighted average. You have only one unknown; the temperature after each mixing interval(T3). Do a series of 1 minute increments using that equation and you'll get your answer.mknott said:So, how does the weighted average pertain to the equation above? I still have two variables that are unknown.
Each interval is 1 minute, so you add up the number of intervals (number of calculations). The fact that the same calculation gets repeated several times is why a spreadsheet works so well...mknott said:So once I calculate all the temperatures after each interval until I reach the desired 65F, how then am I able to calculate the time to get to that temperature? Sorry if I'm not understanding you correctly.
The time it takes for a room to cool down depends on several factors, such as the size of the room, the temperature outside, and the efficiency of the cooling system. Generally, it can take anywhere from 30 minutes to a few hours for a room to cool down.
The cooling time of a room is affected by the temperature difference between the inside and outside of the room, the rate of heat transfer, and the cooling capacity of the system. Other factors such as insulation, air flow, and humidity can also impact the cooling time.
To determine the specific cooling time for your room, you can use a mathematical equation that takes into account the factors mentioned above. Alternatively, you can use a thermometer to measure the temperature and track how long it takes for the room to reach your desired temperature.
Yes, the type of cooling system can significantly impact the cooling time of a room. For example, an air conditioner with a higher cooling capacity will cool a room faster than a fan or a smaller air conditioner. Additionally, the efficiency and maintenance of the cooling system can also affect the cooling time.
To decrease the cooling time of a room, you can make sure that all windows and doors are closed to prevent warm air from entering. Additionally, using curtains or blinds to block out sunlight can also help. Regular maintenance of the cooling system and proper insulation can also decrease the cooling time.