How Does a Double Effect Evaporator Work in Chemical Concentration?

[Naraneer]

Homework Statement

A double effect forward feed evaporator is to concentrate a 12.5% solution of a certain chemical compound "YZ". The feed is to be at and is to be 120 F of such an amount as to contain 6250 "YZ" per hour. Saturated steam is available at 250 F (29.7 psi ). The accepted value of the overall coefficient for the first effect is ( 400 Btu/hr ft2 F ). Condensate may be assumed to leave at the saturation temperature of the steam. The evaporator is provided with a barometric counter-current condenser fed with 357500 Ib/hr cooling water entering at 85 F and leaving at 136 F

i) Calculate the values of the concentration of the "YZ" solution leaving the 1st and 2nd effects, respectively. ii) Determine the temperature of the 2nd effect.
iii) What heating surface must be used if all effects are to have the same area?
iv) Compute the value of the overall coefficient of the 2nd effect.

Homework Equations

[/B]
Cp steam=0.48 Btu/Ib F Latent Heat of steam at 250 F=945.5 Btu/Ib
Feed Enthalpy= 70 Btu/Ib
Evaporation per Ib of Steam = 1.45
Effect I II
T 230 T
t sat 216 141
Lf (latent heat) 967 1011.32
h (enthalpy of liquid) 192 175

The Attempt at a Solution

(945.5)*m(steam) + 5*10^4(70)=(5*10^4-m(vapor 1)(192)+m(vapor 1)Hv1
Hv1=0.48(230-216)+967 + Enthalpy of Saturated liquid at T=216 F

Effect 2
(0.48(230-216)+967) *m(vapor 1)+(5*10^4-m(vapor 1)(192)=(5*10^-4-m(vapor 1)-m(vapor 2))(175)+m(vapor 2)*Hv2

Hv2=0.48 (T-141)+1013.2 + Enthalpy of Saturated liquid at T=141 F

How can I determine the values of Enthalpy of saturated liquid at 216 F and 141 F?
Secondly, How can I perform an Energy balance over the condenser?

 

[KataKoniK]

To determine the enthalpy of saturated liquid at 216 F and 141 F, you can use steam tables or thermodynamic property software to find the specific enthalpies at those temperatures. Alternatively, you can use the Clausius-Clapeyron equation to calculate the enthalpies at those temperatures.

To perform an energy balance over the condenser, you can use the following equation:

Q = m_water * Cp_water * (T_out - T_in)

where Q is the heat transferred, m_water is the mass flow rate of cooling water, Cp_water is the specific heat of water, and T_out and T_in are the outlet and inlet temperatures of the cooling water. This equation assumes that there is no change in the enthalpy of the cooling water as it passes through the condenser.