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.co...light=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'

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...ad13bff139f15c

Does anyone know?

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

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.