Pretest homemade

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Pretest homemade 1) In a three-effect evaporators the boiling points are respectively: BP1= 383K ; BP2=95°C; BP3=80°C; Which are the thermal coefficients of each effect? (Boiling point elevation negligible) Utot= 850 W/m2/K ; TV0= 393 K [sol: W/m2/K U1=3400; U2=2267 ; U3=2267 ] DTtot=TV0-BP3=40 Utot*DTtot=U1*(TV0-BP1) ---> U1 Utot*DTtot=U2*(BP1-BP2) ---> U2 Utot*DTtot=U3*(BP2-BP3) ---> U3 2) In a once-through evaporator an aqueous solution of NaNO3, a very soluble salt, must be concentrated. The temperature inside the unit is 105,72 °C and Tv = 104,3 °C. Which is the molal concentration of the solute obtained? Considering that, Keb [°C*kg/mol] = 9, doesn’t take into account the van’t Hoff factor, but during calculations you should consider it. [sol: m=0,079 mol/kg] deltaTeb = Keb * m * i , where i = 1+ alfa*(n-1) is the van’t Hoff factor, and alfa = 1 since is very soluble and n = 2 since this salt splits in two ions → m 3) A crystallizer operates for 2h to have a growth of 0,052 mm. Give a first estimation of the total mass transfer coefficient knowing that: deltaC = 5 kg/m3 ; rhos=1500 g/dm3 ; volume shape factor= 0,80 ; surface shape factor= 0,85 ; [sol: K = 6,12*10^-6] dL/dt = K/3rhos * psi/phi * deltaC → first estimation deltaL/deltat → K = deltaL/deltat * 3rhos * volume shape factor/surface shape factor *1/deltaC 4) In the graph T vs mole fraction (y), for a crystallizer, highlight the driving force requested for the surface reaction. [solution guideline: ] the difference segment between red - green → y’-ys 5) According to the given data for a centrifugal filtration, decantation will be a problem to filtrate 95% of the liquid? rhos[kg/m3]=2000 ; rhow[kg/m3]=1001 ; w [round/s] = 1,05 ; mu [Pa*s] = 1,19*10^-3 ; Dp[m]=1,11*10^-3 ; R0/R=0,7 ; V0/K = 5 s [sol:…