If a 5 amp unit can cool 4 cups of water to 50 degrees fahrenheit in one hour...
- Thread starter tylercc
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What formula or other information did they give you for this exercise?
When you reply, please include a clear listing of your thoughts and efforts so far. Thank you!
so this is actually a real world situation where I am trying to figure out what the 30 amp unit would do just by knowing what a 5 amp unit can do. If there is information missing that you need let me know and I will get it. I remember doing a similar problem in high school and I know it involved cross multiply (4x=50*128) but then that didn't work so now I am kind of stuck. thanks
As stapel said, more information is needed:
-Cooled to 50\(\displaystyle ^\circ\)F from what temperature?
-Would a 30 amp unit cool the same amount of water from the same starting temperature to 50\(\displaystyle ^\circ\)F six times faster than the 5 amp unit.
-How does this change when to volume [number of cups] changes?
You might want to look at
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html
as a starting place and then maybe use DuckDuckGo or your favourite search engine for more information.
so the water was cooled to 50 degrees from 75 degrees
as far as your other two questions I would've guess so but unfortunately I do not have the ability to test that as i don't have the 5 amp and 30 amp unit. I was hoping to get an idea about how the 30 amp unit would perform with some knowledge about the 5 amp unit.
as far as your other two questions I would've guess so but unfortunately I do not have the ability to test that as i don't have the 5 amp and 30 amp unit. I was hoping to get an idea about how the 30 amp unit would perform with some knowledge about the 5 amp unit.
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We can help students with the math, but we won't know about industry-specific stuff. You'll need to provide all of the engineering, physics, etc, information, including all relevant formulas and assumptions, before we could begin to assist with the math.
If you're looking for the engineering or physics info, then you might want to hire an engineer or physicist to provide you with the consulting services you seem to be seeking. Good luck!
Well, if you look at that link you will see that
Q = c m dT
where we can take Q to represent your 5 amp or 30 amp unit output over 1 hour, c is some 'constant', m can represent the number of cups of water and dT is the change in temperature. We know that when m=4, dT is about -3.89\(\displaystyle ^{\circ}\)C and Q=5 so that
c5 ~ 5/4/(-3.89) ~ -0.321
where the subscript 5 represents the 'constant' for 5 amp unit.
Part of our problem is whether c is constant if we change from a 5 amp unit to a 30 amp unit. That is, does the 'caloric output' scale proportionally with the amperage. If it does, then just use the above equation to compute the change in temperature (in degrees Celsius), i.e.
dT = 30 / (128 c)
EDIT: Note that this is a classic equation and assumes, for example 'a well mixed liquid' as well as several other things. Thus you would have to, at a minimum, 'stir you water gently' so that those assumptions would be at least close to true.
Last edited:
Example of worded problem
Use this as an example where temperature drop is 50 F .
In your question temperature drop is 25F ( 75 down to 50).
EXAMPLE:
If a 5 amp unit can cool 4 cups of water 50 degrees fahrenheit in one hour, what temperature could a 30 amp unit cool 128 cups of water in the same amount of time?
30 amp unit cools 24 cups of water 50 F in one hour
30 amp unit cools 48 cups of water 25 F in one hour
30 amp unit cools 96 cups of water 12.5 F in one hour
30 amp unit cools 32 cups of water 37.5 F in one hour
30 amp unit cools 128 cups of water 9.375 F in one hour
Use this as an example where temperature drop is 50 F .
In your question temperature drop is 25F ( 75 down to 50).
EXAMPLE:
If a 5 amp unit can cool 4 cups of water 50 degrees fahrenheit in one hour, what temperature could a 30 amp unit cool 128 cups of water in the same amount of time?
30 amp unit cools 24 cups of water 50 F in one hour
30 amp unit cools 48 cups of water 25 F in one hour
30 amp unit cools 96 cups of water 12.5 F in one hour
30 amp unit cools 32 cups of water 37.5 F in one hour
30 amp unit cools 128 cups of water 9.375 F in one hour
D
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Are you trying to cool with:
a fan or
a refrigerator?
In either case, you would need more information!!