Friciton Loss Mulitplier

[SMontgomery119]

Hello,

We are designing a new AC piping system that uses ethylene glycol chiller fluid that can go down to 8-degrees Fahrenheit.

I need to compute a friction loss factor to adjust the piping system head loss assuming water is the fluid to the actual head loss for ethylene glycol.

I found that the water fluid friction factor varies significantly with temperature, as the viscosity of water varies significantly with temperature.

At what temperature do I compute the water friction factor?

or what water temperature are typical water piping and fitting losses, such as Table 11 of Carrier Piping Design, determined at?

--Steve

 

[BigInch]

Why not use the actual EG density and viscosity at -8F?

Dynamic Viscosity ? (centpoise) Ethylene Glycol Solution (% by volume)
Temperature (oF) 25 30 40 50 60 65 100
0 1)  1) 15 22 35 45 310
40 3 3.5 4.8 6.5 9 10,2 48
80 1.5 1.7 2.2 2.8 3.8 4.5 14
120 0.9 1 1.3 1.5 2 2.4 7
160 0.65 0.7 0.8 0.95 1.3 1.5 3.8
200 0.48 0.5 0.6 0.7 0.88 0.98 1.4
240 2) 2) 2) 2) 2) 2) 1.8
280 2) 2) 2) 2) 2) 2) 1.4

1. below freezing point
2. above boiling point

Note! The dynamic viscosity of an ethylene glycol based water solution is increased compared with the dynamic viscosity of clean water. As a consequence the head loss in the piping system increase.   

Specific Gravity of Ethylene Glycol based Water Solutions 

Specific gravity - SG - of ethylene glycol based water solutions at various temperatures:

Specific  Gravity  Ethylene Glycol Solution (% by volume)
SG
Temperature (oF) 25 30 40 50 60 65 100
-40 1)  1)  1)  1)  1.12 1.13 1) 
0 1)  1)  1.08 1.10 1.11 1.12 1.16
40 1.048 1.057 1.07 1.088 1.1 1.11 1.145
80 1.04 1.048 1.06 1.077 1.09 1.095 1.13
120 1.03 1.038 1.05 1.064 1.077 1.82 1.115
160 1.018 1.025 1.038 1.05 1.062 1.068 1.049
200 1.005 1.013 1.026 1.038 1.049 1.054 1.084
240 2) 2) 2) 2) 2) 2) 1.067
280 2) 2) 2) 2) 2) 2) 1.05

1. below freezing point
2. above boiling point

Note! The specific gravity of an ethylene glycol based water solution is increased compared with the specific gravity of clean water.  

Specific Heat Capacity of Ethylene Glycol based Water Solutions 

Specific Heat Capacity - cp - of ethylene glycol based water solutions at various temperatures:

Specific Heat Capacity  cp   Ethylene Glycol Solution (% by volume)
 (Btu/lb.oF)
Temperature (oF) 25 30 40 50 60 65 100
-40 1)  1)  1)  1)  0,68 0.703 1) 
0 1)  1)  0.83 0.78 0.723 0.7 0.54
40 0.913 0.89 0.845 0.795 0.748 0.721 0.562
80 0.921 0.902 0.86 0.815 0.768 0.743 0.59
120 0.933 0.915 0.875 0.832 0.788 0.765 0.612
160 0.94 0.925 0.89 0.85 0.81 0.786 0.64
200 0.953 0.936 0.905 0.865 0.83 0.807 0.66
240 2) 2) 2) 2) 2) 0.828 0.689
280 2) 2) 2) 2) 2) 2) 0.71

1. below freezing point
2. above boiling point

Note! The specific heat capacity of an ethylene glycol based water solution is less than the specific heat of clean water. For a heat transfer system the circulated volume must be increased. 

In a 50% solution with operational temperatures above 36 oF the specific heat capacity is decreased with aprox. 20%. The reduced specific heat capacity must be compensated by circulating more fluid.   

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"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein

 

[SMontgomery119]

Yes, I have the all properties of ethylene glycol.

However, my piping head loss values are for water. I still need a multiplier to convert water piping head loss to ethylene glycol piping head loss.

The question is what temperature do I compute the water friction factor at?

--Steve

 

[BigInch]

Much better to compute your head losses at the correct density and viscosity, then use equivalent lengths for the fittings.

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"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein

 

[BigInch]

Lacking adequate notation on the table, assume 60F. I doubt you'll be far off.

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"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein