Multi-Effect Evaporation: Heating Tab (TVR)

This tab appears on the interface dialog of the Continuous Multi-Effect Evaporation operation if the Vapor Recompression Option is set to “Thermal Vapor Recompression” in the Oper. Conds Tab (see Multi-Effect Evaporation: Oper. Conds Tab).

Variable Definitions, Ranges and Default Values

The following table shows a brief description of the variables appearing in this tab; for a detailed description of these variables, see Multi-Effect Evaporation: Description of Terms The table also displays their default values and their generally acceptable range. Note that due to how the variables are used in the modeling equations, the range of acceptable values may be further reduced; for more details, see Multi-Effect Evaporation: Modeling Assumptions & Constraints.

Variable	Default Value	Range

○ Heating Agent Name Indicates the heating agent used in the evaporator. Click on the list box to bring up a list of available heating agents in order to select one.	Steam	Any Heating Agent
● Supply Temp. of Heating Agent (^oC) The temperature of the heating agent before the heat transfer.	152.0	Positive
● Return Temp. of Heating Agent (^oC) The temperature of the heating agent after the heat transfer.	152.0	Positive
● Mass-to-Energy Factor of Heating Agent (kcal/kg) The specific heat source of the heating agent between supply and return.	503.683	Positive
● Duty of Heating Agent (kcal/h) The heat transfer rate of the heating agent.	0.0	Positive
● Flow of Heating Agent (kg/h) The mass flow rate of the heating agent.	0.0	Positive
○ Same Properties As Vapor? The heating fluid in the first effect may be a mixture of heating agent, desuperheating agent and recompressed vapor. Check this box to indicate that the unknown thermodynamic properties of this fluid (outlet enthalpy, pressure) will be calculated based on the properties of recompressed vapor only.	<Yes>	Yes/No
● Flow of Heating Fluid in First Effect (kg/h) The mass flow rate of the heating fluid in the first effect.	0.0	Positive
● Specific Inlet Enthalpy of Heating Fluid in First Effect (kcal/kg) The specific enthalpy of the heating fluid at the steam chest inlet of the first effect.	0.0	Positive
● Outlet Temp. of Heating Fluid in First Effect (^oC) The temperature of the heating fluid at the steam chest outlet of the first effect.	152.0	Positive
◙ Condensing Temp. of Heating Fluid in First Effect (^oC) The temperature at which the heating fluid will condense in the steam chest of the first effect (corresponding to the pressure that the heating fluid exhibits in the steam chest of that effect).	152.0	[Supply Temp., Return Temp.]
◙ Specific Outlet Enthalpy of Heating Fluid in First Effect (kcal/kg) The specific enthalpy of the heating fluid at the steam chest outlet of the first effect.	0.0	Positive
◙ Pressure of Heating Fluid in First Effect (bar) The pressure of the heating fluid in the steam chest of the first effect.	1.013	Positive
● Specific Heat Duty of Heating Fluid in First Effect (kcal/kg) The specific heat source of the heating fluid used in the heating space of the first effect.	0.0	Positive
○ Entrainment Ratio (wt Vapor/wt Heating Agent) The entrainment ratio of vapor drawn from the selected effect in the steam-jet ejector. The entrainment ratio is defined as the ratio of the mass flow rate of vapor at the vapor inlet of the steam-jet ejector to the mass flow rate of heating agent at the heating agent inlet of the steam-jet ejector.	1.0	Positive
● Heating Agent Inlet Temperature (^oC) The temperature of heating agent at the heating agent inlet of the steam-jet ejector. This is the same as the supply temperature of the heating agent.	152.0	Positive
● Heating Agent Inlet Specific Enthalpy (kcal/kg) The specific enthalpy of heating agent at the heating agent inlet of the steam-jet ejector.	0.0	Positive
○ Entrained Vapor Inlet From Effect The effect from which vapor is drawn and recompressed.	1	Positive
● Entrained Vapor Inlet Pressure (bar) The pressure of entrained vapor at the vapor inlet of the steam-jet ejector. This is the same as the pressure of vapor in the effect from which the entrained vapor in the steam-jet ejector is drawn.	1.013	Positive
● Entrained Vapor Inlet Temperature (^oC) The temperature of entrained vapor at the vapor inlet of the steam-jet ejector. This is the same as the pressure of vapor in the effect from which the entrained vapor in the steam-jet ejector is drawn.	25.0	Positive
● Entrained Vapor Inlet Specific Enthalpy (kcal/kg) The specific enthalpy of entrained vapor at the vapor inlet of the steam-jet ejector. This is the same as the specific enthalpy of vapor in the effect from which the entrained vapor in the steam-jet ejector is drawn.	0.0	Positive
● Entrained Vapor Flow(kg/h) The mass flow rate of entrained vapor in the steam-jet ejector.	0.0	Positive
● Recompressed % (% of Vapor in Effect) The percentage of vapor produced in the chosen effect for recompression that is drawn from that effect and is entrained in the steam-jet ejector where it is recompressed.	0.0	[0,100)
● Steam Ejector Outlet Pressure (bar) The pressure of the mixture of entrained vapor and heating agent at the outlet of the steam-jet ejector.	1.013	Positive
● Steam Ejector Outlet Specific Enthalpy (kcal/kg) The specific enthalpy of the mixture of entrained vapor and heating agent at the outlet of the steam-jet ejector.	0.0	Positive
● Steam Ejector Outlet Flow(kg/h) The mass flow rate of the mixture of entrained vapor and heating agent at the outlet of the steam-jet ejector.	0.0	Positive

Symbol Key: ○ User-specified value (always input); ● Calculated value (always output); ◙ Sometimes input, sometimes output

Specification Choices / Comments

The following list describes the available specification choices in this tab; for more details on how these are implemented, see Multi-Effect Evaporation: Modeling Calculations.

•If the option “Same Properties As Vapor” is checked...

You must specify the Specific Outlet Enthalpy and Pressure of the heating fluid in the first effect.

•If the option “Same Properties As Vapor” is not checked...

The Specific Outlet Enthalpy and Pressure of the heating fluid in the first effect will be calculated by the program based on the assumption that the thermodynamic properties of the heating fluid in the first effect (which may consist of heating agent, desuperheating agent and recompressed vapor) are the same as those of recompressed vapor.

•Entrained Vapor Inlet From Effect...

Select one of the available effects (specified in the Oper. Conds Tab) as the effect from which vapor will be drawn and will be entrained in the steam-jet ejector.