The data below are for an unnamed fluid at 80 degrees C: a) Obtain the molecular

Question

The data below are for an unnamed fluid at 80 degrees C:

a) Obtain the molecular weight of the fluid.

b) A 1 m3 tank contains 120 kg of this fluid at 80 degrees C. Determine the volume fraction of the liquid in the tank.

c) A rigid tank is completely filled with saturated liquid at 80 degrees C. Heat is added until temperature increases to 85 degrees C. Determine the pressure that develops in the tank due to the thermal expansion of the liquid, assuming the tank itself does not expand. Hint: Calculate the coefficient of isothermal compressibility, k.

P (bar) Density (kg/m3)Phase 0.109 0.553 1.123 1.723 2.123 732.6 735.1 vapor vapor vapor vapor sat. vapor sat. liquid liquid 20 volumetric coefficient of thermal expansion: = 0.0014 K-1

Explanation / Answer

PV = nRT

n - number of moles = M/m , M is the mass and m- molecular weight

P = (1/m) (M/V)RT, M/V = d - density

molecular weight m = (d/P)RT

d/P is slope of P-d curve

      = (0.553-0.109)/(0.5-0.1)e+5 = 1.11e-5

molecular weight m = 1.11e-5*8.314*(273+80) = 32.5 gms

b) Tank contains 120 kg of liquid

moles n = 120/32.5e-3 = 3.6923e+3 moles

volume V = 1 cu.m

P = nRT/V = 3.6923e+3*8.314*353/1.0 = 1.084 e+7 Pa

                                                               = 108.4 bar

From the data given above the density and the pressure in the tank are for liquid pahse of the fluid and 100% of the fluid in in liquid phase.

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