Boiler mass flow rates

Hello,

I am trying to simulate a parabolic trough power plant based on Rankine cycle.
Field HTF fluid: Therminol VP-1
Design loop inlet temp: 293°C
Design loop outlet temp: 391°C

In the "Power Cycle" tab - "Power Block Design Point" Section, I believe that the design inlet & outlet temperatures are automatically copied from the design loop inlet and outlet temperatures from the Solar Field, right?

If Yes, I can assume that those two temperatures - design inlet & outlet temperatures - represent the hot side (or the solar filed HTF) of the boiler. Please correct me if I am wrong.

I have the doubt that the software is also somehow considering that water enters the boiler at 293°C and leaves at 391°C. The problem is, in the case I am simulating, the boiler pressure (water/steam) is 25 bar. Therefore the software considers the water at the boiler inlet is superheated steam which does not make sense!

Moreover when I check the results for both "Field HTF mass flow rate total" and "Cycle HTF mass flow rate" are very similar!

for your reference, I have attached a plot comparing both mass flow rates for one day.

Thanks!

Hello,

Yes, the HTF inlet and outlet design temperatures on the Power Cycle page are the solar field HTF outlet and inlet design temperatures from the Solar Field page. You can edit the values on the Solar Field page, but not on the Power Cycle page.

For modeling purposes in SAM, the boundary of the power cycle is at the solar field inlet and outlet. You can see this clearly in Figure 7 of Wagner (2011) "Technical Manual for the SAM Physical Trough Manual."

Those temperatures are for the HTF, not the steam. Under design conditions, the HTF enters the heat exchanger between the solar field and power cycle at 391°C, and leaves it at 293°C. Table 12 of Wagner (2011) shows the steam conditions at design.

As for the mass flow rates, in my tests using the default trough system for the physical trough model, the field HTF mass flow rate is generally higher than the power cycle HTF mass flow rate.

Best regards,
Paul.