Need help in Chiller capacity reverse calculation 1

[Asisraja D]

Hi professionals

we have ordered 20TR Brine chiller for our pilot plant purpose. recently i checked the chiller specification sheet and i was curious to do the reverse calculation based on the data provided by vendor. i did the calculation using the website

https://theengineeringmindset.com/chiller-cooling-capacity-calculate/

I have attached the excel sheet for my calculation but i get only 15TR capacity instead of 20TR.

Can anyone just check my calculations ? is this correct ? if any errors please tell me where i have did the mistake ?

"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce​

 

[Asisraja D]

Graph i used for density values for - 10 Deg.C for 50% methanol by its weight.

link:

https://www.methanol.org/wp-content/uploads/2016/06/Densities-of-Methanol-Water-Mixes.pdf

Specific heat value i used here has taken for -10 Deg.C at isobaric process due to change in temperature at evaporator section.

link:

https://www.engineeringtoolbox.com/...obaric-isochoric-d_2103.html?vA=-10&degree=C#

Please find the attached chiller specification provided by vendor.

"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce

 

[BronYrAur]

This should be an easy check with the manufacturer. I don't use metric units and don't have time to convert and double-check anything. But the nominal tonnage rating of a piece of equipment is based on certain flow and temperature conditions, and it is most likely based on straight water with no glycol. The addition of glycol reduces capacity. I know that's not much help, but I would check with the manufacturer on how they determined that the unit was 20TR.

 

[Asisraja D]

BronYrAur

I did the calculation based on flow rate & in and out chilled water temperatures so i request you to just check my steps involved in this. Thank you

"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce

 

[pierreick]

Hi,
Consider this link to support:

https://waterchillers.com/chiller-resources/sizing-information/

Simple, No?
Are you an undergraduate student? IF so, you should go to student forum.
Your excel sheet is terrible, in particular intermediate calculation. Before starting using excel make sure you understand the calculation and formula to apply.
In your case: Q=M*cp* delta T and 1RT = 12 000 btu/h.
20% safety margin seems common in this industry.
Good luck
Pierre

 

[Asisraja D]

pierreick

Are you an undergraduate student? IF so, you should go to student forum.
No i am a working professional, yeah i made formulas looks shortcut and i will give correct abbreviation for them to understand well.

i tried that calculator already but i don't think it will work for all kind of chillers because we use methanol for anti-freezing agent in brine chillers so the specific heat of the solution may vary. that's why i made this steps for accurate load calculations.

you can see there it suggest me to go for 33 TR chiller but we don't know the background steps and parameters involved, hope you understand my point. this is my curious to know that's it.

"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce

 

[Asisraja D]

pierreick

I used metric units all over the sheet so consider in metric units only for all the calculations and enter your values in metric only.

I revised the sheet with little modifications for clear understanding.
if you feel free please review my pipe wall thickness excel sheet in this thread 522778

Thank you.

"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce

 

[pierreick]

Hi,
The point is that RT is a unit of power: 1 RT =12 000 BTU/h
In your case, based on the link shared:
Oversized capacity is 20RT or 20*12 000= 240000 btu/h
Capacity required (theoretical) should be: 240000/1.2 = 200 000 btu/h or 58.61 Kw
which allows a cooling flow rate of:
58.6 /(cp *delta T) = ..... kg/s
cp in KJ/Kg K, delta T is 5 C or K

Make sure you have the properties of your coolant with the right units.
A google search: Cp is about 3.4 kJ/Kg/K and Ro about 930 kg/m3, different from your data.
The question mark is how concentrated is your brine? this will affect the properties of the coolant.
Good luck
Pierre

 

[Asisraja D]

cp in KJ/Kg K, delta T is 5 C or K.

In my case the det-t value is (-5 C). This is brine chiller so.

Make sure you have the properties of your coolant with the right units.

You are referring chilled brine if yes, those properties are in correct units.

i have attached the pdf for taking values of chilled brine water solution like

Density of the brine at -10 C at 50% mixture is 935 kG/M3.

I took specific heat values from this site for -10 C.

https://www.engineeringtoolbox.com/...capacity-Cp-Cv-isobaric-isochoric-d_2103.html

Sp.heat of the brine at -10 C is 2.36 KJ/KG/K.



"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce

 

[pierreick]

Hi,

https://detector-cooling.web.cern.ch/data/Table 8-3-2.htm

Pierre

 

[Asisraja D]

pierreick

It helped me a lot, i hope it works now because
i change the brine properties but i took for 40% mixture for -10 Deg.C
sp.heat is 3.632 KJ/KG.K
Density is 951 kg/m3

Now the chiller capacity is 23.24 TR.

20% Higher Safety margin is 27.89 TR.


"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce

 

[Asisraja D]

pierreick

Thanks a lot sir.

Please review my thread 522778 for pipe wall thickness calculation for under internal pressure.

Thank you

"Strive for perfection in everything you do. Take the best that exists and make it better. When it does not exist, design it." - Sir Henry Royce