Split Thermal (SplitT)

Navigation: Models ➔ Sub-Models ➔ Split Thermal (SplitT)

Split Material Flow		Split Thermal (Requires SplitFlow = On)
Split Flows (Split)	SplitFlow - General Operation	Split Thermal (SplitT)

---

General Description

This sub-model allows the user to specify different temperatures for the outlet streams from a unit. Units that may have SplitT enabled are currently the Tank or Tie. The user may either:

1. Specify the temperatures for all outlet streams and allow SysCAD to Add/Remove heat to satisfy the requirements OR
2. Specify n-1 streams to allow the last stream be the balance of the total energy to ensure a conservation of energy across the unit operation.

Note:
The SplitFlows option MUST be selected before the SplitThermal, option is available to the user.

Adding Split Thermal (SplitT) to a Unit

The SplitT is enabled in a unit when the user enables the tickbox for SplitThermal under Options as shown below:

A new Tab page becomes visible, SplitT, that the user can then configure to adjust the outgoing stream temperatures from the unit.

Options

The user may specify a number of different methods for setting the temperature in the exiting streams. Some Examples are shown on the bottom of the page.

1. Required
   • The user sets the actual required temperature in the outgoing stream.
2. Change
   • The Change value is the difference between the exiting stream temperature and the Feed temperature to the SplitT block, i.e. the actual temperature within the unit.
   • The temperature difference may be limited if ChangeT.Limit is enabled.
3. FreeDiff
   • The User may set a temperature difference for the selected outlet stream to the streams that are set at Free.
   • The temperature difference may be limited if ChangeT.Limit is enabled.
4. Free
   • This is the default option. It does not allow the user to set the value of the exiting stream. Therefore, if all streams remain in the default mode, they will leave the unit at the same temperature as the unit temperature.
5. AllowHX
   • If AllowHX is enabled, then the user may set the values for ALL of the exiting streams, as SysCAD will either add or remove energy from the unit to maintain an energy balance. The values for each stream may be any value.
   • If AllowHX is NOT enabled, then the user may set the values for N - 1 exiting streams, where N is the total number of exiting streams. SysCAD will then adjust the temperature of the N^th stream to maintain an energy balance. The values for each stream may be any value.
   • In Build 139.31388 or later, the user can set values for ALL of the exiting streams, even if the AllowHX option has NOT been enabled. If the specifications are not able to be achieved, then the amount of energy that would need to be added or removed in order to achieve the temperatures specified by the user will be displayed.
6. User may set the value for only a single stream, if required, and the other streams will then all be at the same (different) temperature.

Data Sections

The Split Thermal (SplitT) tab page can be used to specify how heat is distributed with the streams.

Tag (Long/Short)	Input/Calc	Description
Mixture temperature before thermal split
Feed.MassFlow / Qm	Feedback	Only available in Build 139.31388 or later. The mass flow of the mixture before splitting of streams.
Feed.Temperature / T	Feedback	The temperature of the mixture before splitting of streams - this is the temperature in the unit.
Condition	Feedback	OK if no errors, otherwise displays error message.
AllowHX	Tickbox	Selecting this option allows the user to specify temperatures for all outgoing streams. SysCAD will add or remove energy to conserve the energy across the unit operation. Any energy added/removed will be shown on the HeatFlow field.
UseSplitFlowsPriority	Tickbox	Only available in Build 139.31424 or later. If selected, the order of streams on the SplitT page will match the order on the Split page. If not selected, then the user will be able to set the priorities for each stream on the SplitT page, independent of the order on the Split page.
HeatFlow	FeedBack	In older builds, this was only visible when the AllowHX option had been enabled. This shows the amount of energy added or removed in order to achieve the temperatures specified by the user.
HeatCorrection	FeedBack	Only available in Build 139.31388 or later. Only visible when the AllowHX option has NOT been enabled. This shows the amount of energy that would need to be added or removed in order to achieve the temperatures specified by the user. This will only be non-zero if the required temperatures can not be achieved.
TIOs.[stream name]...
Order	FeedBack	This can be changed using the Priority field (if available).
Priority	List	This is used to change the order of the output streams if the Required or Change modes are selected. In Build 139.31388 or later, it is only available if the UseSplitFlowsPriority option has NOT been enabled.
Mode (See Options and Examples for more info)	Required	The user may specify the required temperature of the outlet stream. This temperature may be limited by the temperature change limits specified.
	Change	The user may specify the required temperature change for the outlet stream. This temperature may be limited by the temperature change limits specified.
	FreeDiff	The user can set a temperature difference for the selected outlet stream to the streams that are set at Free. For example, if the unit operation has two outlet streams, stream 1 is set at FreeDiff = 10, stream 2 is set at Free, then Stream 1 will be 10 degrees hotter than stream 2 when solved. This temperature may be limited by the temperature change limits specified.
	Free	The user may not specify any outlet temperature requirements, SysCAD will determine the outlet temperature. If Free is used for all streams then all streams will have the same outlet temperature (same behaviour as when SplitT model is not used at all).
TemperatureReqd / T_Reqd	Input	This is visible with mode set to Required, use this to specify the stream outlet temperature.
TempChange	Input	This is visible with mode set to Change, use this to specify the stream outlet temperature change.
TempDiff	Input	This is visible with mode set to FreeDiff, use this to specify the stream outlet temperature difference for the current stream and the streams that are set at Free.
TemperatureOut / To	FeedBack	This is the outlet temperature for the stream.
Result	FeedBack	This shows whether the user specified temperature conditions have been achieved. NOTE: Fraction of the target is based on required temperature change that has been achieved.
Achieved	FeedBack	This shows the fraction of the required temperature change that has been achieved.
MassFlow / Qm	Feedback	Only available in Build 139.31388 or later. The mass flow of the stream, after the split logic has been applied.
Temperature change limits:
FinalT.Min	Input	The minimum temperature of the mixture leaving the unit operation. If the balance stream temperature falls below this minimum when the AllowHX option is ticked, heat will be added to make it up to the minimum temperature. If AllowHX option is not selected, all outlet stream temperatures will be adjusted to keep a balance of heat.
FinalT.Max	Input	The maximum temperature of the mixture leaving the unit operation. If the balance stream temperature is above this maximum when the AllowHX option is ticked, heat will be removed to limit it to the maximum temperature. If AllowHX option is not selected, all outlet stream temperatures will be adjusted to keep a balance of heat.
ChangeT.Limit	Tickbox	Selecting this option allows the user to specify temperature limits for all outgoing streams. If AllowHX option is selected, SysCAD will add or remove heat to conserve the energy across the unit operation. Any energy added/removed will be shown on the PowerInput field.
ChangeT.MaxDrop	Input	Only visible if ChangeT.Limit is enabled. This is the maximum amount that any stream be below the Feed temperature of the SplitT block.
ChangeT.MaxRise	Input	Only visible if ChangeT.Limit is enabled. This is the maximum amount that any stream be above the Feed temperature of the SplitT block.

Examples

Input Specification	SplitT Configuration	Results
Required Mode on (1) Stream
Feed Temperature = 150°C Two outlet streams P411 and P404 P411 = Required Temperature of 130°C AllowHX not enabled The temperature of P404 is not set		P411 will have a temperature of 130°C (as required) P404 T is higher as the energy removed from P411 is added to P404
Required Mode on both Streams
Feed Temperature = 150°C Two outlet streams P411 and P404 P411 = Required Temperature of 130°C P404 = Required T of 140°C AllowHX enabled		P411 will have a temperature of 130°C (as required) P404 will have a temperature of 140°C (as required) The energy change is shown in HeatFlow (the excess energy that is removed)
Change Mode on (1) Stream
Feed Temperature = 150°C Two outlet streams P411 and P404 P411 = Change value of -3°C AllowHX not enabled The temperature of P404 is not set The dT may be limited if ChangeT.Limit is enabled		P411 will have a temperature of (150-3=147)°C (as required) P404 T is higher as the energy removed from P411 is added to P404
FreeDiff Mode on (1) Stream
Feed Temperature = 150°C Two outlet streams P411 and P404 P411 = FreeDiff of 3°C P404 will be 3°C lower than P411 AllowHX not enabled The dT may be limited if ChangeT.Limit is enabled		P411 is 3°C higher than P404 as required
Notes: If AllowHX is enabled, then the user may set the values for ALL of the exiting streams, as SysCAD will either add or remove energy from the unit to maintain an energy balance. The values for each stream may be any value. If AllowHX is NOT enabled, then the user may set the values for N - 1 exiting streams, where N is the total number of exiting streams. SysCAD will then adjust the temperature of the Nth stream to maintain an energy balance. The values for each stream may be any value. The user may set the value for only a single stream, if required, and the other streams will then all be at the same (different) temperature.