Thermodynamics on steady state

AI Thread Summary
At steady state, a mixture of liquid water and ethylene glycol is analyzed, with water at 20°C and 1 bar, having a molar flow rate of 4.2 kmol/min. The mixture is specified to be 50% ethylene glycol by mass, leading to the need for calculations regarding the flow rates of both components. The density of ethylene glycol is determined to be 1.115 times that of water, which is approximately 1112.77 kg/m³. The calculations attempt to establish the mass and volumetric flow rates of ethylene glycol, but assumptions about exit flow rates lead to negative results, indicating a potential miscalculation or misunderstanding of the system. The discussion highlights the importance of correctly defining flow rates in steady-state thermodynamic problems.
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Homework Statement


At steady state, a stream of liquid water at 20C, 1bar is mixed with a stream of ethylene glycol (M=62.07 g/mol) to form a refrigerant mixture that is 50% glycol by mass. The water molar flow rate is 4.2 kmol/min. The density of ethylene glycol is 1.115 times that of water.

Determine

a) the molar flow rate, in kmol/min, and volumetric flow rate, in m3/min, of the entering
ethylene glycol.

Homework Equations



m1 + m2 = m3

m1h1 + m2h2 = m3h3


The Attempt at a Solution



Firstly, I do not know whether is there a leaving flow on the ethylene glycol there that make it to have the m3 flow rate to exist.

If I assume there is a flow rate exit there,

Vf = 0.001002 m^3/kg
Density of water = 1/0.001002
= 998 kg/m^3
Density of ethylene = 1.115 x 998
= 1112.77kg/m^3

Mw = 18.015 kg/kmol
Volume flow rate of water = 18.015(4.2)(0.001002)
= 0.07581 m^3/min

0.07581 + m2 = m3

If I assume that the mass flow rate for the exit one is m3 = 0.5m2

The answer turns out to be negative, which i don't think is correct
 
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questions for you:

what is the mass flow of the water?
therefore, what is the mass flow of the ethylene glycol?
therefore, what is the volumetric flow of ethylene glycol?
and finally the molar flow of the ethylene glycol?
 
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