Did you play around at all with the parameters that control the number of nodes in the collector and the number of subtimesteps that the model uses? If not I would start by increasing those values.

If that doesn't solve the problem then my guess as to the problem is that at times when there is little solar radiation the model is trying to slow the flow down to a very small rate so that it can achieve the desired outlet temperature and at those flow rates the temperature changes from node to node might be getting unrealistically large. 

In reality pumps can only turn down to perhaps 10-20% of their rated flow. What I usually do in the case of a collector that is trying to maintain an outlet temperature is to send the collector's "desired" flow rate to a pump that has a minimum turndown imposed on it. The flow rate that the collector actually gets may be higher than it wanted and  the collector may not achieve the desired temperature during low solar radiation periods but that is a more realistic situation anyway. Sometimes I use two instances of the collector model; one instance is calculating the desired flow rate and then the other instance is just getting the actual flow rate from a pump model.

~david

The primary cause of this problem is if you've installed some other software that uses a similar command prompt file, the TESS libraries can get confused and try to reference that other location. Try uninstalling the TESS libraries from the TESSLibs_Uninstall.exe in your TRNSYS directory and reinstalling them. Also make sure that you install the same version of the TESS libraries as you did for TRNSYS (64-bit or 32-bit). If you are in TRNSYS18, I recommend the 64-bit version. With a new PC it may be possible that it no longer supports the 32-bit version.

I hope this helps!

Have you checked the \UserLib\DebugDLLs and \UserLib\ReleaseDLLs folders? My guess is that you need to reinstall Type344 and direct it to install in your TRNSYS18 directory. Be sure to use the 64-bit version of the Type. Copying the dll from your TRNSYS17 directory won't work because TRNSYS17 is 32-bit. If you don't have a Type344 installer for 64-bit or compatible with TRNSYS18, reach out to your distributor and they can help you get the appropriate installer.

Type344 could not be located in either the TRNdll64.dll or in an external dll. Please relink theTRNDll64.dll including this Type or make sure that an external DLL in the \UserLib\DebugDLLs and \UserLib\ReleaseDLLs folders contain the Type.

It works properly in TRNSYS 17 without any errors.

My question is: during the simulation, I very frequently get the error shown in the attached picture. Does anyone know why this error appears?

Thank you very much

While the values you are getting are not exactly the same as printed in the tutorial .pdf, they are close enough to give me confidence you understood the tutorial and followed it correctly. My best guess is a small update may have been made to the weather data reader, the solar collector, or another tutorial component since the .pdf was created, and the values printed in the pdf were not revised accordingly.

Most bug fixes and enhancements that have changed between Trnsys18 releases are logged in the release notes, which you can read by opening the 'readme' file in your main Trnsys18 directory. Unfortunately, I don't know which release version of Trnsys18 was used for the tutorial .pdf, but any release notes pertaining to Type 1, Type 15, or weather file or radiation data processing might give a clue.

You can check your TRNSYS release version by opening Simulation Studio, clicking the '?' in the top menu, and selecting 'About ...'; on the splash screen that follows, at the bottom center, the number following Trnsys Version: gives the release version you are using. 

For reference, I opened Trnsys18.06.0002, ran the example 'Begin' for 168 hours without any other revisions, and got +0.2701936406946902E+006 and +0.3164063593053098E+006 for Qcollector and Qauxiliary, respectively - somewhere between your results and the results published in the tutorial. 

I am using TRNSYS 18 and I am currently following the manual tutorial, specifically Tutorial 9, Section 9.2: “Creating a Simple TRNSYS Project.”

I have followed the instructions carefully step by step, but at the end of the tutorial I am getting results that are different from the results shown in the manual. I have repeated the tutorial twice now, and I am still getting the same incorrect/different results.

I have attached screenshots of the results I am getting, along with my project/input files, so that you can see what I have done.

Could someone please help me check what I might be doing wrong? I would really appreciate any guidance, especially on whether my component connections, parameters, or output setup are incorrect.

Thank you very much

~david