The Detailed Evaporator model can be used to simulate various types of evaporators including Long Tube Vertical and Falling Film evaporators.
The Liquor_In, Liquor_Out, Steam_In, Steam_Out and Condensate_Out streams are required. Post_Heater_Liquor_In and Post_Heater_Liquor_Out streams are required for a post-heater. The Condensate_In stream is optional.
Specify the heat transfer Area and either the Dome Pressure or Heat Transfer Coefficient. If the Dome Pressure is given the Heat Transfer Coefficient is calculated. If the Heat Transfer Coefficient is given the Dome Pressure is calculated. The Energy Efficiency is required.
If the heat transfer Area is not given the available energy is transferred to the liquor side. The Liquor_Out and Steam_Out pressures are the Dome Pressure (if given) or the Liquor_In pressure.
If a post-heater is included specify either the Heat Transfer Coefficient and Area or the post-heater Delta T. Post-heater pressure defaults to the Post_Heater_Liquor_In pressure if not given.

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Data Description

Equipment Properties

Data Descriptions

Data		Unit		Description
Set	Item	Type	Native	Description
Equipment Properties	Dome Pressure	Pressure	psia	Pressure of Liquor_Out and Steam_Out streams. If given with Area the Heat Transfer Coefficient is calculated.
	Heat Transfer Coefficient	Heat Trans Coef	BTU/hr/F/ft2	If given with Area the Dome Pressure is calculated.
	Area	Area	ft2	Heat transfer Area.
	Energy Efficiency	Fraction or Percent	Fraction	Fraction of available energy transferred to the liquor.
Post Heater	Heat Transfer Coefficient	Heat Trans Coef	BTU/hr/F/ft2	If given Area must also be given.
	Area	Area	ft2	If given Heat Transfer Coefficient must also be given.
	Delta T	Temperature Change	Delta F	Change in temperature from Post_Heater_Liquor_In to Post_Heater_Liquor_Out.
	Pressure	Pressure	psia	Post heater pressure. Defaults to Post_Heater_Liquor_In pressure.
Calculated Properties	Dome Pressure	Pressure	psia	The dome pressure of the evaporator, calculated if the Heat Transfer Coefficient is given.
	Heat Available for Transfer	Energy Flow	BTU/hr	This is the heat input to the evaporator body, SI * Hstm
	Evap Heat Transfer Coef	Heat Trans Coef	BTU/hr/F/ft2	The heat transfer coefficient calculated for saturated liquor, assuming the logarithmic average temperature difference between the inlet and outlet flows. It is taken in account that the heat transferred is the latent heat of steam and, usually, the evaporators are working with a constant delta T.
	Evap Delta T	Temperature Change	Delta F	Condensate_Out temperature minus Liquor_Out temperature.
	Evap Heat Transferred	Energy Flow	BTU/hr	The heat transferred to evaporator (a part of the total available heat).
	BPR	Temperature	F	The boiling point rise of the outlet liquor.
	Post Heater Heat Trans Coef	Heat Trans Coef	BTU/hr/F/ft2	Heat transfer coefficient, calculated for post heater.
	PH LM Delta T	Temperature Change	Delta F	Logarithmic average temperature difference, calculated for post heater.

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Equipment Properties

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Example of using equipment

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Method&Equations

The Steam_In stream and the Condensate_In stream (if supplied) supply the energy for evaporation (q_in).
If the Heat Transfer Coefficient and heat transfer Area are given the Dome Pressure is calculated by first calculating the saturation temperature and then calculating the corresponding saturation pressure.
qtransferred = HTC*A*deltaTlog
deltaTlog = (deltaTmax - deltaTmin)/ln(deltaTmax/deltaTmin)
where:
deltaTmax = Tsatsteam - (Tsat-5) (assumed that, usually, the liquor is heated with approximately 5 degrees in a single effect)
deltaTmin = (Tsatsteam - 1) - Tsat (assumed that the condensate temperature is lower with 1 degree than the steam saturated temperature)
then:
Tsat = (Tsatsteam * (Exp(6*HTC*A/qtransferred) - 1) - Exp(6*HTC*A/qtransferred) - 5) / (Exp(6*HTC*A/qtransferred) - 1)
Tsat is the liquor saturation temperature at the Dome Pressure.
Also:
qtrans=Eff*(q_in-q_cond) - q_ph
q_cond is the energy leaving with Condensate_Out and q_ph is the energy transferred to the post-heater (if supplied).
If the Dome Pressure and Area are given the Heat Transfer Coefficient is calculated by:
HTC=qtrans / (A*deltaTlog)
qtransferred is taken over by the liquor which is flashed at the Dome Pressure. The resulting vapor is transferred to Steam_Out and the remaining solution is transferred to Liquor_Out.

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Warnings

Outlet flow is zero!