Re: [TRNSYS-users] Question to TRNSYS forum

[Jeff Thornton <thornton@tess-inc.com>]

<You have to modify the fortran code since the properties should be function of temperature. The current form considers them as constant parameter. You can add an input variable and its related formula instead of the constant parameter to consider the effect.>

Unfortunately, that's the easy part.  The model was developed with the concept of fixed properties and when temperature-based fluid properties are used the entire fundamental equation changes.  Take for example a constant volume storage tank.  The governing equation is d(MCpT)/dt = Qin - Qout

The d(MCpT)/dt term can be broken out as:

d(MCpT)/dt = M Cp dT/dt + M T dCp/dt + Cp T dM/dt

For constant properties dCp/dt =0, dM/dt = 0 and it reduces to M Cp dT/dt = Qin + Qout

 

But when Cp = f(T) and Mass = f(T) due to the density change then we have to chain rule everything:

 

dCp/dt = dCp/dT * dT/dt

dM/dt = dM/dT * dT/dt  where M = Density * Volume

 

M Cp dT/dt + M T dCp/dT dT/dt + Cp T dM/dT dT/dt

 

And what was a somewhat easy differential equation to solve is now much more difficult.  So you'll have to derive and solve a brand new equation for the collector.

But then it's critical to remember that every other model that this fluid flows through needs to be changed: pipes, tanks, valves etc....

 

I would strongly suggest that you investigate the performance at the extremes of the properties and see how much of a change the properties make on the system performance.  Hopefully you'll find that it's a small change and constant properties will then work just fine....

 

Jeff

 

 

---
Jeff Thornton
President - TESS LLC
3 N. Pinckney Street, Suite 202, Madison WI USA 53703
Office: (608) 274-2577  Fax: (608) 278-1475
www.tess-inc.com
E-Mail: thornton@tess-inc.com

On 07/14/2021 12:14 am, Arian Bahrami via TRNSYS-users wrote:

Hi,

 

You have to modify the fortran code since the properties should be function of temperature. The current form considers them as constant parameter. You can add an input variable and its related formula instead of the constant parameter to consider the effect.

 

Arian


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On Wednesday, July 14, 2021, 8:05 AM, Sai Ruthwick Madas via TRNSYS-users <trnsys-users@lists.onebuilding.org> wrote:

Hello

 

My name is Sai. I request you to post my following question to the TRNSYS mailing list forum.

 

Dear all,

 

I want to simulate nanofluids in PV-Thermal panels using TRNSYS software. Unfortunately, it appears that the ‘TYPE 50’ module only use fluid specific heat as an input. I believe this specific heat input alone does not satisfy the conditions for nanofluid simulation.

 

In this case, how can I use nanofluids in the PVT simulation?

 

Has anyone ever worked on this particular application of nanofluid into the PVT system with TRNSYS software? If yes, How did you do this?

 

Regards

Sai

 

Sai Ruthwick Madas

Masters (CQU), Bachelors (JNTUH)

Research student | School of Engineering and Technology,

CQ University Bundaberg, Building 13/G.06, University Drive, Bundaberg, QLD 4670

| E s.madas@cqu.edu.au

This communication may contain privileged or confidential information. If you have received this in error, please return to sender and delete. CRICOS: 00219C | RTO Code 40939

 

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