I need a little help with a calculation

[Kompulsa]

Hello.

I built a water chiller, and I don't know what its cooling capacity is because I am still learning about these things and it was not built perfectly.

If it cools 1 gallon of room temperature (25 C) water to 2 degrees celsius, then how many BTUh of heat was removed from the water?

[install monkey]

http://www.refrigeration-engineer.com/forums/showthread.php?28310-chiller-capacity-formula-amp-calculation&highlight=capacity

[frank]

We need to know how long it took to cool the water

[Kompulsa]

4 minutes.

Sorry, the temperature the water was cooled to is actually 10 C. Not 2.

[frank]

You don't say if your Gallon is US or 'Rest of the World' :D

As I work in SI lets assume the following:

1 UK Gallon = 4.8 Lts
1 US Gallon = 3.8 Lts

Using the formula Q = M C DT

Where Q = Power Required in kW
M = Mass Flow
C = Specific Heat Capacity
dt = Temperature difference of working fluid (T1 - T2)

To use the formula we need to convert your mass into mass flow, so 4.8/240 = 0.02l/s
Therefore, Q = 0.02 x 4.19 x (25-10)
= 1.257kW
Converting kW to BTU's = 4291.9334 BTU's

If it is US Gallons

3.8/240 = 0.01583
Therefore Q = 0.01583 x 4.19 x 15
= 0.995kW
Converting kW to BTU's = 3397.3538 BTU's

I'm assuming that this is a college question? ;)

[Kompulsa]

Sorry, I meant U.S gallons. :)

This is for a water chiller that I built with a 50 foot 3/16" copper plain tubing condenser and a 20 foot 1/4" plain tubing evaporator, as well as a 1/4 HP R-134a fridge compressor.

I tried to cool air with the water but that failed so badly the air was just warm, and air flow was very slow, I could barely feel air coming out of the other side of the heat exchanger and the water the evaporator was in was barely cool. I don't understand if something went wrong when I started trying to cool air, but it cools the water when by itself fine (in the time I showed you).

This has been tremendously helpful, and it was kind of you to go to that trouble for me.

Thank you for helping me. :)

You answered my question, but now I need to figure out what is happening, and i'm not sure how.

I'm not sure if my chiller is performing as well as it should as I don't know what the BTU rating at 10 C should be.

Here is the compressor datasheet, it has a chart of the cooling capacity at different temperatures, but only up to -10, which is 20 C below the temperature I operated it at: http://www.fileconvoy.com/dfl.php?id=g671c8a65541b4f9a14341966ad13bff139f15c

Does anyone know?

You don't say if your Gallon is US or 'Rest of the World' :D

As I work in SI lets assume the following:

1 UK Gallon = 4.8 Lts
1 US Gallon = 3.8 Lts

Using the formula Q = M C DT

Where Q = Power Required in kW
M = Mass Flow
C = Specific Heat Capacity
dt = Temperature difference of working fluid (T1 - T2)

To use the formula we need to convert your mass into mass flow, so 4.8/240 = 0.02l/s
Therefore, Q = 0.02 x 4.19 x (25-10)
= 1.257kW
Converting kW to BTU's = 4291.9334 BTU's

If it is US Gallons

3.8/240 = 0.01583
Therefore Q = 0.01583 x 4.19 x 15
= 0.995kW
Converting kW to BTU's = 3397.3538 BTU's

I'm assuming that this is a college question? ;)

[MikeHolm]

To keep us all from changing all your data, try to stick to either imperial or SI. I know it is hard to do while sitting below the big American machine.