Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations The Obturator on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

How Convert 1 gal of chilled water to Tons

Status
Not open for further replies.

vanleurth

Mechanical
Oct 31, 2003
11
Hello Everybody,

I'm trying to convert a gallon of chilled water to TONS.
Is this correct?
1. The weight of 1 gal of water is 8.35 lbm
2. From saturated liquid tables I get uf (internal energy @ 50F temp) = 18.06 btu/lbm
3. 1 Ton = 12000 btu

Therefore,

1 gal (8.35 lbm/1 gal)(18.06 btu/lbm)(1 ton / 12000 btu)

Is this correct?
Thank you in advance for any help on this question,

V.
 
Replies continue below

Recommended for you

No.

1 ton of refrigeration is 12,000 BTU/h. It is a unit of POWER.

Change in energy per time.

It is impossible to convert the energy in a gallon of water to tons (or any other unit of power) because you have only one energy state and no time.
 
Like MintJulep said, you're computing energy not power.

In US units, you need gallons per minute (GPM), not gallons, and the delta-T (which corresponds to the delta-enthalpy of liquid water) of the chilled water to compute power.

(Total heat into the chiller - Total heat out of the chiller) / time period



Good on ya,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies
 
vanleurth,

What kind of tons. Short, long, metric, registered gross?

Critter.gif
JHG
 
Like GooberDave said in his second paragraph, it only is defined as with regard to a difference in two states. If you had asked "how many tons of refrigeration would be required to cool one gallon of water from 60F to 35F in 30 seconds" there would have been an answer.

Unless you are talking about a nuclear reaction converting a mass to an energy unit isn't happening.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
 
accepting that the OP needs to understand units better ...

if 1 ton = 12000 Btu/hr (in refrigeration)

and chilled water has 18.06 Btu/lbm = 18.06*8.35 Btu/gallon
(mind you i remember 1 gallon of water weighing 10 lbs (ie lbf) ... but ...)

so 12000/(18.06*8.35) would be the number of gallons of chilled water to provide 1 ton of refrigeration (power)
(which looks like the reciporical of the OP's calc)
 
Well...but uf = internal energy = 18.06 Btu/lbm (didn't verify this) - this is the internal energy of the water relative to a reference temperature (I think 32 F = 0 C, but definitely not to some unknown, warmer temperature that the chilled water would be returned to the chiller at. Sorry for the grammar. The correct equation would use the known (or WAG'd) temperature differential of the water multiplied by its average specific heat, which is roughly 1.0 BTU/lb/deg F for water based on my hazy memory of the definition of a BTU (1 lb. of water raised 1 deg. F).
 
@rb1957 - An imperial gallon weighs close to 10 lbs, and a US Gallon weighs about 8.35 lbs.

Katmar Software - Engineering & Risk Analysis Software

"An undefined problem has an infinite number of solutions"
 
true enough ... automatically thought of the UK gallon (8 pints or 4.54 lt not the US 3.8 lt variety (Y, oh Y?) ...
 
this whole thread is a +1 for the metric system...

NX 7.5.5.4 with Teamcenter 8 on win7 64
Intel Xeon @3.2GHz
8GB RAM
Nvidia Quadro 2000
 
this whole thread is a +1 for the metric system...

Why?

The OP is confused on fundamental principles. Until you grasp the fundamentals the unit system is irrelevant.

 
It depends on what kind of ton, long, short or metric. 1000 litres of water weighs 1 metric tonne.
 
lisa ...

we're not talking about a ton as a weight (be it 2240 lbs, 2000 lbs, or whatever) but a ton as a unit of refrigeration power ...

i somehow think the OP knew what he wanted, just failed to express it (clearly)
 
Ah I see, I wondered why everyone was over-complicating it, lol.
 
Mintjulep said:

Because apparently "ton" has 3 definitions in a non-metric environment, which is the initial source of the OP's confusion.
Not to forget that a gallon in America is different from a gallon in England, which sure doesn't make things any easier to understand.

NX 7.5.5.4 with Teamcenter 8 on win7 64
Intel Xeon @3.2GHz
8GB RAM
Nvidia Quadro 2000
 
You could express the OP's query in whatever units you like, and he would still have the same conceptual misunderstanding. As much as I am a supporter of SI Units, the units are not the problem here.

Katmar Software - Engineering & Risk Analysis Software

"An undefined problem has an infinite number of solutions"
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor