[TRNSYS-users] Capacity of buffer tank

[Amdi Worm]

Dear Zhe & David

I have discovered the same problem as Zhe. Did you find a solution to the
problem he had? If yes, maybe it could be a solution to my problem too.

Kind Regards
Amdi

2012/12/4 David BRADLEY <d.bradley at tess-inc.com>

>  Dear Zhe,
>   Would you mind sending me project? From your explanation, it certainly
> sounds as though everything is correct. I am curious as to which component
> is generating an error saying that the buffer tank is too small.
> Kind regards,
>  David
>
>
>
> On 12/4/2012 05:03, Zhe Li wrote:
>
>  Dear David,****
>
> ** **
>
> Thank you very much for your reply. ****
>
> ** **
>
> I did a number of calculations followed by your recommendation in
> designing the correct size of buffer tank. However, The answer I am getting
> is far from the size of buffer tank that I am allowed to simulate my model.
> ****
>
> ** **
>
> The rated flow rate I am using is 1548kg/h and time step is 0.1h. For one
> time step, the volume is 154.8kg. I would think the buffer tank having a
> size of 0.2m3 is sufficient to hold one step volume liquid. However, I
> always get error when performing the simulation. The minimum size of buffer
> tank that I have to use is 0.37m3 in order to carry out the simulation
> without error occurring.****
>
> ** **
>
> I have also worked out the total amount liquid is in the loop. I am using
> a pipe inside diameter is 0.022m, the total length of pipe is 60m, this
> gives me a total volume water is 22.8kg, I am not sure how this is related
> to the size of the buffer tank. ****
>
> ** **
>
> Hope you don’t mind to explain to me a little more.****
>
> ** **
>
> Thank you very much.****
>
> ** **
>
> Zhe Li****
>
> ** **
>
> *From:* David BRADLEY [mailto:d.bradley at tess-inc.com<d.bradley at tess-inc.com>]
>
> *Sent:* 03 December 2012 17:56
> *To:* Zhe Li
> *Cc:* trnsys-users at cae.wisc.edu
> *Subject:* Re: Capacity of buffer tank****
>
> ** **
>
> Dear Zhe,
>   In order for the simulation to be numerically stable, the buffer tank
> must be large enough to hold at least one time step of liquid. So the
> answer to your question depends upon the rated flow rate of the pump in the
> loop and on the time step that you have chosen. In the actual system, there
> is liquid volume contained in the piping network. I would recommend that
> you determine how much liquid volume there is (knowing the inside diameter
> and length of each pipe section), then create a buffer tank of equivalent
> size and reduce your time step accordingly.
> Kind regards,
>  David
>
> ****
>
> On 11/28/2012 11:07, Zhe Li wrote:****
>
> Dear David,****
>
>  ****
>
> Thanks for your time.****
>
>  ****
>
> As we discussed before, due to the fact that the current air-water  heat
> pump (Type 941) is a single stage heat pump, a buffer tank is used to
> prevent overheating when a imposed thermal load is employed. Even though
> the desired system is not working with a buffer tank, this does solve the
> original problem I had. However, I have discovered a new problem. What
> would be the right capacity of this buffer tank to built into in order to
> simulate the actual system (system without using buffer tank)? I have tried
> to simulate using varies capacity tank ( from 0.3m3 to 1m3) as the buffer
> tank, the electricity consumption can be different as much as 5% which it
> is significant as far as I am concerned. ****
>
>  ****
>
> Also, I understand there is an auxiliary heater built into the air-water
> heat pump component. Would you recommend to use this auxiliary heater or
> use an external heater built into the circuit where after the buffer tank
> which makes it more realistic?****
>
>  ****
>
> Hope I have explained the problem clearly.****
>
>  ****
>
> Thank you very much.****
>
>  ****
>
> Zhe Li****
>
>
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>
>
>
> ****
>
> -- ****
>
> *******************************
>
> David BRADLEY****
>
> Principal****
>
> Thermal Energy Systems Specialists, LLC****
>
> 22 North Carroll Street - suite 370****
>
> Madison, WI  53703 USA****
>
> ** **
>
> P:+1.608.274.2577****
>
> F:+1.608.278.1475****
>
> d.bradley at tess-inc.com****
>
> ** **
>
> http://www.tess-inc.com****
>
> http://www.trnsys.com****
>
>
> Tá an teachtaireacht seo scanta ó thaobh ábhar agus víreas ag Seirbhís
> Scanta Ríomhphost de chuid Seirbhísí Faisnéise, ITBÁC agus meastar í a
> bheith slán. http://www.dit.ie
> This message has been scanned for content and viruses by the DIT
> Information Services E-Mail Scanning Service, and is believed to be clean.
> http://www.dit.ie
>
>
> --
> ***************************
> David BRADLEY
> Principal
> Thermal Energy Systems Specialists, LLC
> 22 North Carroll Street - suite 370
> Madison, WI  53703 USA
>
> P:+1.608.274.2577
> F:+1.608.278.1475d.bradley at tess-inc.com
> http://www.tess-inc.comhttp://www.trnsys.com
>
>
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