Parabolic trough freeze protection

Paul Gilman
Platinum Member

05 Oct 2012 16:40 #208 by Paul Gilman

Replied by Paul Gilman on topic Parabolic trough freeze protection

That error message means that during the simulation, the HTF temperature exceeded the bounds specified in the HTF property table for more than 50 time steps. You can choose to ignore the message, or either try a different HTF or change the system design to avoid this condition.

Best regards,
Paul.

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vp16
Junior Member

08 Oct 2012 14:03 #209 by vp16

Replied by vp16 on topic Parabolic trough freeze protection

Ok. But one question, The units or the quantity is not mentioned. And I am getting the same error with Therminol VP1. The numbers 393 and 773 are not clear as the lower and upper limit for temperatures are different. Could you please throw some light on this aspect.?

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Paul Gilman
Platinum Member

08 Oct 2012 16:18 #210 by Paul Gilman

Replied by Paul Gilman on topic Parabolic trough freeze protection

I agree that the wording of this error message is unclear and am working with the programmers to improve it in the next version (Fall 2012). It is a little difficult to explain -- those two sentences are trying to convey a lot of information:

The temperature units are all degrees Celsius. The values 393 and 773 are the upper and lower operating temperature limits of the HTF from the fluid property table (stored internally in the code). During simulations, SAM counts the number of instances that the calculated HTF fluid temperature is above or below those limits. If the limits are exceeded more than 50 times, SAM reports the warning message with the HTF temperature in the 50th instance.

In your case, the HTF temperature was either lower than 393 degrees or higher than 773 degrees 50 times. The 50th time that the HTF temperature fell outside of the limits was the 187th times step when the HTF was 857.5 degrees.

Best regards,
Paul.

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vp16
Junior Member

09 Oct 2012 11:54 #211 by vp16

Replied by vp16 on topic Parabolic trough freeze protection

Ok. I understood. Still, isn't the maximum temperature limit in Celsius for Hitc XL 500. Besides for any other HTF or Molten salts the maximum temp. limit is 550 or 600 degrees C but 773 C operating temparature limit is still unclear?
How can these salts have such a higher operating temperature.?

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Paul Gilman
Platinum Member

09 Oct 2012 17:56 #212 by Paul Gilman

Replied by Paul Gilman on topic Parabolic trough freeze protection

SAM is reporting the temperatures in Kelvin, not degrees Celsius. That will be fixed in the Fall 2012 version.

Thanks,
Paul.

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vp16
Junior Member

11 Oct 2012 09:10 #213 by vp16

Replied by vp16 on topic Parabolic trough freeze protection

What is the basic freeze protection mode considered by default in SAM.? When it plots the freeze protection energy and tank freeze protection energy does it calculate the electrical heat tracing of all the pipes (kms and kms of pipes in PT) and tanks.?
I plotted the results on a table for all the 8760 hours in a year and it shows auxiliary heater fuel consumption/parasitic load for all the hours as zero. Normally in PT plants auxiliary heaters are used for freeze protection and in MS PT plants auxiliary heaters and heat tracing in pipes can be provided for redundancy. So what does it consider in SAM BETA model for freeze protection.?

Also, when I plot the 8760 hourly results, what is the start date and start hour.? 1st January and 12:00 midnight.?

SAM BETA Model Feedback: In Thermal Storage page, it still shows values for Heat exchanger derate and temperature drop when we used MS as HTF and MS as storage. This should not appear as we have direct storage so heat exchangers are not there.
Please, share some insights on this.
Thanks in advance.

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