Re: [TRNSYS-users] Type 71 Evacuated tube collector - Control vs. overheating

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

Maverick,

Your 3rd control shuts off the pump when the collector temperature 
exceeds 110 C.  But once the pump shuts off, the collector will stagnate 
and reach very high temperatures with no flow through the collectors.  
In this case, the 3rd control should probably sense the outlet 
temperature of the pipe leaving the collector and not the collector 
itself.  This way you're getting the overheat protection when there is 
flow.

As for the quick temperature rise in winter, I'll point out that Type 71 
does not include the impact of mass.  So temperatures will rise and fall 
very quickly.  The TESS version of the evacuated tube model accounts for 
the mass and should behave much as you expect it to.

Jeff

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


On 02/26/2018 4:49 am, maverickxxx1991 via TRNSYS-users wrote:
> Hi,
>
> I’m using 2 type 71 and I get temperature up to 400°C if I use a
> control. I have 3 Controllers of type 2b:
>
> 1st looks if temperature of collector is higher than secondary inlet
> of heat exchanger with hysteresis (7K and 4K)
> 2nd looks for storage temperature (<95°C with hysteresis again „On“ at 
> 90°C)
> 3rd is for collector protection (collector temperature <110°C with
> hysteresis again „On“ at 95°C)
>
> The collector values are (0.688, 0.583, 0.003) (last in W/(m^2*K) and
> W/(m^2*K^2)).
> Test condition flow rate 0.02 kg/(s*m^2).
> 2x86 m^2 area, no. in series 1, flow rate 2600 kg/hr.
>
> So if the controls says out the temperature in the collectors rise up
> to 400°C. Is it normal? How can I fix it? I even wondering about the
> temperatures rising so fast also in winter from 15 to 80°C.
>
> Thanks for help!
> maverickxxx
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