<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:10pt"><div><span>Hi David,</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;"><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;"><span>I don't use any equations for the flow rate just a pump with fixed flow rate and simple controller Type 2. When I put for example a tank Type 60c - 0,3 m3, with internal heat exchanger having area of 1,45 m2 and length 16m I set up flow of 260kg/h with 4 m2 collectors and there are no problems, but if I increase the boiler to 1 m3 exchanger area to 3,5
m2 and length 20m leaving the same flow rate I have convergence problem ( message "1 non -convergences for Hx 1.Final UAHx value = 169.181"), then increasing the flow to 400 kg/h there is no problem, the simulation reaches it end of 8760h. Any idea why this happens? (I assume that there is something influenced by the total volume of the system collector-heat exchanger...)</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;"><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; background-color: transparent; font-style: normal;"><span>Regards</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande',
sans-serif; background-color: transparent; font-style: normal;"><span>Igor </span></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 10pt;"> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12pt;"> <div dir="ltr"> <font size="2" face="Arial"> On Wednesday, April 9, 2014 5:49 PM, David BRADLEY <d.bradley@tess-inc.com> wrote:<br> </font> </div> <div class="y_msg_container"><div id="yiv8290934398"><div>
Igor,<br clear="none">
It is a little worrisome that you get convergence problems at low
flow rates. If you have used equations to set a minimum turndown
ratio on a pump (essentially a minimum flow rate) then you can
certainly run into some situations where your setpoints are not met.
When doing this, however, it is important that you use similar
equations in conjunction with your controller model so that the
controller doesn't try to make the pump do something that it is
unable to do (and thereby lead to convergence problems).<br clear="none">
Kind regards,<br clear="none">
David<br clear="none">
<br clear="none">
<br clear="none">
<div class="yiv8290934398yqt6095701529" id="yiv8290934398yqt59975"><div class="yiv8290934398moz-cite-prefix">On 4/8/2014 13:37, Igor Seso wrote:<br clear="none">
</div>
<blockquote type="cite">
<div style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255); font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 10pt;">
<div id="yiv8290934398">
<div>
<div style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255); font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 10pt;">
<div id="yiv8290934398">
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<div class="yiv8290934398yui_3_13_0_1_1396980912287_5910" id="yiv8290934398yui_3_13_0_1_1396980912287_6014" style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255); font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 10pt;">
<div id="yiv8290934398yui_3_13_0_8_1396980912287_13">
<div id="yiv8290934398yui_3_13_0_8_1396980912287_13" style="margin-top:0.1em;margin-bottom:0.1em;"><span id="yiv8290934398yui_3_13_0_8_1396980912287_20">Thank you David, exactly
that was the problem, I was recording
temperatures above 60 C when there was no flow
through the valve - I put a trigger printer
recording only temp. when there is flow and
the temperatures values were exactly as the
set mixing temp. </span></div>
<div id="yiv8290934398yui_3_13_0_8_1396980912287_13" style="margin-top:0.1em;margin-bottom:0.1em;background-color:transparent;"><br clear="none">
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<div id="yiv8290934398yui_3_13_0_8_1396980912287_13" style="margin-top:0.1em;margin-bottom:0.1em;background-color:transparent;">I
tried to put pipes between the collector the
tank and the pump to get more realistic results
regard outlet temperaturesas a result of the
increased thermal mass and it was ok - but the
only disadvantage is that the pump flow can not
go under certain value (total volume of fluid in
pipes) it gives convergence problems...so it
means that it is not possible to test the
influence of low flow on system efficiency etc..</div>
<div id="yiv8290934398yui_3_13_0_8_1396980912287_13" style="margin-top:0.1em;margin-bottom:0.1em;background-color:transparent;"><br clear="none">
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<div id="yiv8290934398yui_3_13_0_8_1396980912287_13" style="margin-top:0.1em;margin-bottom:0.1em;background-color:transparent;">Regards,</div>
<div id="yiv8290934398yui_3_13_0_8_1396980912287_13" style="margin-top:0.1em;margin-bottom:0.1em;background-color:transparent;">Barto</div>
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<div class="yiv8290934398yahoo_quoted" id="yiv8290934398yui_3_13_0_8_1396980912287_15" style="display: block;">
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<div class="yiv8290934398yqt6608141044" id="yiv8290934398yqt67382">
<div class="yiv8290934398yqt2318821345" id="yiv8290934398yqt17177">
<div dir="ltr"> <font face="Arial" size="2"> On Tuesday, April 8, 2014
7:34 PM, David BRADLEY
<a rel="nofollow" shape="rect" class="yiv8290934398moz-txt-link-rfc2396E" ymailto="mailto:d.bradley@tess-inc.com" target="_blank" href="mailto:d.bradley@tess-inc.com"><d.bradley@tess-inc.com></a> wrote:<br clear="none">
</font> </div>
<div class="yiv8290934398y_msg_container">
<div id="yiv8290934398">
<div> Barto,<br clear="none">
It is not really possible to
diagnose the problem without looking
at the project. I would recommend
using an online plotter to look at
all of the temperatures and flow
rates of all the flows going into
and coming out of the tank. If for
some reason all of the temperatures
in the system are over 60C
(including the temperature of the
tempering water) then Type953 would
not be able to temper the outlet
flow. It could also be that you are
seeing higher than 60C temperature
at the mixing valve when there is no
flow through the valve.<br clear="none">
If you are not able to sort out
the problem using Type65 as a
debugging tool then you should send
your project to your distributor so
that they can have a look at it.<br clear="none">
Kind regards,<br clear="none">
David<br clear="none">
<br clear="none">
<br clear="none">
<br clear="none">
<div class="yiv8290934398yqt6915655950" id="yiv8290934398yqt07530">
<div class="yiv8290934398moz-cite-prefix">On
4/7/2014 08:16, Barto Pene
wrote:<br clear="none">
</div>
<blockquote type="cite">
<div dir="ltr">Hi ,
<div><br clear="none">
</div>
<div>I get some strange result
i.e I can not find logic in
it: I use tank Type 60c only
heated by standard solar
collector installation. I
use the differential
controller(monitoring temp.)
to limit the tank top
temperature to 60C and I'm
also using tempering valve
Type 953 with diverting and
three-wat valves for
controling the outlet temp.
In the simulation I get
temperatures at the outlet
of the three-way valve
(after mixing) higher than
60C (even 80-90C) how is it
possible?</div>
<div><br clear="none">
</div>
<div>When I model the HX in
Type60c with glycol solution
I get convergence problems
and with water there is no
problem...?</div>
<div><br clear="none">
</div>
<div>Thank you</div>
<div><br clear="none">
</div>
<div>Regards</div>
<div>Barto</div>
</div>
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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
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