[TRNSYS-users] 4 way valve

Dear trnsys users,

I would like to simulate a SDHW System in which a 4 way valve is used to discharge the

store (Type 340) with a fixed mixing temperature from 3 temperature zones.

I’ve attached a project file I’ve used to test the controller.

I’ve tried to use two flow diverter and two tee pieces to realize the system.

Double Port 3 is placed in the top of the storage

Double Port 2 between top and middle of the storage

Double Port 1 in the middle of the storage

Flow diverter 1 outlet flow rate 1 is connected to Double Port 1

Flow diverter 1 outlet flow rate 2 is connected to flow diverter 2 Inlet flow rate

Flow diverter 2 outlet flow rate 1 is connected to Double Port 2

Flow diverter 2 outlet flow rate 2 is connected to Double Port 3

(in the complete system the temperatures are also connected, but in the attached file

I have no system between Flow diverter and mixers… and the input temperatures to the

tee pieces have fixed values to simulate an example for storage temperatures)

The double ports outlet flow rates and temperatures are connected to two tee pieces

Tee Piece 1 inlet temperature 1 and flow rate 1 is connected to Double Port 2

Tee Piece 1 inlet temperature 2 and flow rate 2 is connected to Double Port 3

Tee Piece 2 inlet temperature 1 and flow rate 1 is connected to Double Port 1

Tee Piece 2 inlet temperature 2 and flow rate 2 is connected to outlet temperature and outlet flow

rate of tee piece 1

In the attached file the outlets of the flow diverters are connected to the inlets of the tee pieces.

I’ve tried to control the outlet flow rates from the flow diverters with iterative feedback controllers

to reach the set point temperature as mixing temperature of tee piece 1 and 2.

The first flow diverter is controlled by an iterative feedback controller monitoring the

outlet temperature of tee piece 2 (setpoint 40°C)

the second flow diverter is controlled by a second iterative feedback controller monitoring

the outlet temperature of tee piece 1 (setpoint also 40°C)

the inlet flow rate of flow diverter 1 is fixed

inlet temperature 1 of tee piece 1 is 50°C

inlet temperature 2 of tee piece 1 is 70°C

inlet temperature 1 of tee piece 1 is 30°C

To reach the setpoint the control function of flow diverter 1 has to be zero and

the control function of flow diverter 2 has to be 0.5.

The first iterative feedback controller works fine, control function is set to zero, but the second iterative

Feedback controller doesn’t work, but I don’t know why.

I hope someone can help me or can tell me an easier way to realize the system.

Thanks

Danny