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Friciton Loss Mulitplier

Friciton Loss Mulitplier

Friciton Loss Mulitplier

(OP)

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

RE: Friciton Loss Mulitplier

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.                                   
            

http://virtualpipeline.spaces.msn.com

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

RE: Friciton Loss Mulitplier

(OP)

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

RE: Friciton Loss Mulitplier

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

http://virtualpipeline.spaces.msn.com

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

RE: Friciton Loss Mulitplier

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

http://virtualpipeline.spaces.msn.com

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

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