<HTML><BODY><font face="arial,helvetica,sans-serif" size="2">Dear Ehsan<br /><br />please see further comments below.<br /><br />--------- Original-Nachricht --------<br /> Von: "Ehsan Baharvand" <ebaharvand@yahoo.com><br /> An: "Achim.geissler" <achim.geissler@intergga.ch>, "esp-r@lists.strath.ac.uk" <esp-r@lists.strath.ac.uk><br /> Betreff: Re: AW: [esp-r] solar chimney<br /> Datum: 01/04/11 11:14<br /><br /></font> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><div>Dear Achim,</div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"> </div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt">Please see my answers below:</div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"> </div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2">a) what is "massiv" (your back wall)? </font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><strong>This is the back wall.<br /><em>Sorry, my bad english: What I meant is, "how heavy / massive" is the construction? It does seem to change temperature quite rapidly. What is the solar absorption coefficient you are using on the back wall?</em><br /></strong></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"> </div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2">b) how long is your pre-simulation period, how long is your simulation period and what does "temperature does not change" mean? "Not at all" or "not as much as expected"? </font></div><font size="2"> </font><div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><strong>Pre-simulation = 12 days</strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><strong>Simulation period = 1 day (24h)</strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><strong>Time-step = 60 <em>... so, 1 minute time steps?</em><br /></strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><strong>Integration per hour = yes</strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"> </font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><strong>The temperatures do not change at all. This holds for all the surface, air node temp or thermal db node temperature. </strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><br />c) what do! you mean "wind effect is not included"? An afn takes wind into account by the cp-value table you must define for external nodes.<br /><strong>I excluded the wind effect by using Cp=0 for all the directions.<br /><em>O.K.!</em><br /></strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"> </font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2">d) do the air changes (outside air) change with changed opening sizes?<br /><strong>Yes, see attachtment Infiltration Load / Rate.</strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><br /><br /></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2">e) how large are the air changes befor / after changing the opening sizes?</font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"><strong>See attachtment Infiltration Load / Rate.</strong></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2"> <br /><strong><em>Infiltration rate, load: These profiles look O.K. at first glance. The air flow rate rises significantly with larger openings, the zone-wise load also increases for larger openings (more pronounced stack effect). Have you looked at your temperature stack?<br /><br />The load in zone 1 (the lowermost one, I assume) stays quite similar. This zone has the large external "entry"? How large are the vertical openings between the zones as compared to the external opening at the bottom and the openings at each level?<br /></em></strong><br /></font></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font size="2">f) do you have a bypass in your stack to allow for downward air flow (night time)?</font></div> <div style="font! -family: times new roman,new york,times,serif; font-size: 12pt"><strong>How to do this?But there is no control on the air flow inside the chimney. The control is based on free-floating. Do I need a bypass?</strong><br /><br /><em><strong>I am not sure if you need one, here. Generally, to allow for downward movement of air and upward movement of air at the same time (e.g. cold glass, warm wall) it is a good idea to split such a stack vertically, also.</strong></em><br /><br /></div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt">Thanking you in advance. </div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"> </div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt">Kind regards,</div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt">Ehsan </div> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"><font face="Tahoma" size="2"! > <hr /> <strong><span style="font-weight: bold">From:</span></strong> Achim.geissler <achim.geissler@intergga.ch><br /><strong><span style="font-weight: bold">To:</span></strong> EhsanBaharvand <ebaharvand@yahoo.com>; esp-r@lists.strath.ac.uk<br /><strong><span style="font-weight: bold">Sent:</span></strong> Fri, April 1, 2011 9:26:47 AM<br /><strong><span style="font-weight: bold">Subject:</span></strong> AW: [esp-r] solar chimney<br /></font><br /> <font size="2">Dear Ehsan<br /><br />some questions for clarification to help understand your model:<br />a) what is "massiv" (your back wall)?<br />b) how long is your pre-simulation period, how long is your simulation period and what does "temperature does not change" mean? "Not at all" or "not as much as expected"?<br />c) what do you mean "wind effect is not included"? An afn takes wind into account by the cp-value table you must define for external nodes.<br />d) do the ! air changes (outside air) change with changed opening sizes?<br />e) how large are the air changes befor / after changing the opening sizes?<br />f) do you have a bypass in your stack to allow for downward air flow (night time)?<br /><br />Best<br />Achim<br /><br /></font> <p> </p><font size="2">--------- Original-Nachricht --------<br />Von: "Ehsan Baharvand" <ebaharvand@yahoo.com><br />An: "esp-r@lists.strath.ac.u! k" <esp-r@lists.strath..ac.uk><br />Betreff: [esp-r] solar chimney<br />Datum: 01/04/11 09:05<br /></font><br /> <div style="font-family: times new roman,new york,times,serif; font-size: 12pt"> <div>Dear all,</div> <div> </div> <div> <div><u><strong>Problem</strong></u></div> <div>The free-floating of a solar chimney is simulated and a upward stream due to the solar energy occurs. </div> <div>However when increasing the infiltration (colder ambient air) by increasing the opening area to outside the backw! all inside surface temperature doesn't change!  Other thing is that the heat load inside the chimney is being removed by the infiltration air exchange. Eventhough I increase the infiltration air exchange, the heat load being removed increases, but the surface temperature of the backwall remains the same. </div> <div> </div> <div> <div><strong><u>Question</u></strong></div> <div>Do I forget something? W! hat can be the problem?</div> <div>I'm certain about the configurations and the Air Flow Network. </div></div></div> <div> </div> <div><strong><u>Model</u></strong></div> <div>The 22 zones solar chimney uses a air flow network and has 2 wind pressure boundary nodes at the inlet and the outlet. </div> <div>Each zone has a separate connection with the outdoors through a air flow network connection, which simulates a opening between glazing panels <strong>meant for infiltration</strong>!</div> <div>The inlet and the outlet areas are connect! ed to the ambient air thourgh a orifice with a Cd of 0.67. </div> <div>Between the cubic thermal zones fictitious surfaces are used. </div> <div>The backwall is a massive construction with adiabatic BC at the surface outside node. </div> <div>At 1.8 meter distance from the backwall there is a glazing surface with a G-value of 0.8 and 80% of glass and it has a external BC. </div> <div>The chimney is South oriented for a Cl! imate catagory 3A according to Ashrae 90.l. </div> <div> </div> <div><strong><u>Not included</u></strong></div> <div>Wind effect is not included.</div> <div> </div> <div> </div> <div>Kind regards,</div> <div> </div> <div>E. Baharvand </div> <div> </div></div><br /><br /> <hr /> <br />_______________________________________________<br />esp-r mailing list<br /><a rel="nofollow" href="mailto:esp-r@lists.strath.ac.uk" target="_blank" class="autolink">esp-r@lists.strath.ac.uk</a><br />http://lists.strath.ac.uk/mailman/listinfo/esp-! r </div></div></BODY></HTML>