[TRNSYS-users] Heating Coil: Type 670-1 bug

[David Bradley]

Fred,
 Heating coils are pretty easy because you don't have to worry about 
condensation. With cooling coils, if memory serves, you can't quite use 
the same effectiveness concept because there is both sensible and latent 
cooling going on. Typically what you have to do is to adjust the bypass 
fraction at the coil's rated conditions in order to tune the model to a 
particular coil's performance. The bypass fraction method essentially 
assumes that some of the air comes out of the coil saturated at the coil 
water temperature and some of the air bypasses the coil entirely and 
remixes downstream.
Best,
 David

Fred Betz wrote:
>
> Sorry David, my wording was very poor.
>
>  
>
> What I was trying to get at is that the approach temperatures appear 
> too small.
>
>  
>
> I have 22C air entering the coil and 29C air leaving the coil.
>
>  
>
> I have 32C water entering the coil and 25C water leaving the coil.
>
>  
>
> That is a delta T of just 3C, or 5.4F between the air entering and the 
> water leaving.
>
>  
>
> It should be about 7-10F based on project experience.
>
>  
>
> This might be splitting hairs, but with 500,000 CFM of air flow, 1 
> degree means thousands of dollars. Therefore, every item gets 
> scrutinized.
>
>  
>
> Also, I was hoping there was a way to set the effectiveness on the 
> cooling coil like I was able to on the heating coil.
>
>  
>
> Thanks,
>
>  
>
> Fred
>
>  
>
>  
>
> *Fred Betz**  *PhD., LEED AP
> Sustainable Systems Analyst
>
> 	
>
>  
>
> 	
>
> *AEI* | AFFILIATED ENGINEERS, INC.  
> 5802 Research Park Blvd. | Madison, WI  53719
>
> P: 608.236.1175 | F: 608.238.2614  
> fbetz at aeieng.com <mailto:fbetz at aeieng.com>  |  *www.aeieng.com 
> <http://www.aeieng.com/>*  
>
>  
>
>  
>
> *From:* David Bradley [mailto:bradley at tess-inc.com]
> *Sent:* Monday, March 29, 2010 4:18 PM
> *To:* Fred Betz
> *Cc:* trnsys-users at cae.wisc.edu
> *Subject:* Re: [TRNSYS-users] Heating Coil: Type 670-1 bug
>
>  
>
> Fred,
>  I think you might be confusing efficiency and effectiveness. 
> Effectiveness is actual energy transfer divided by maximum 
> theoretically possible energy transfer. The air and water side heat 
> transfers need to be equal or else there is an energy imbalance across 
> the coil.
> Best,
>  David
>  
>
> Fred Betz wrote:
>
> All,
>
>  
>
> There appears to be a bug in the Type 670-1 heating coil.
>
>  
>
> I set the effectiveness of the coil to 0.70, but the air and water 
> side heat transfer rates are approximately equal.
>
>  
>
> Anyone have a fix?
>
>  
>
> Fred
>
>  
>
>  
>
> *Fred Betz**  *PhD., LEED AP
> Sustainable Systems Analyst
>
> 	
>
>  
>
> 	
>
> *AEI* | AFFILIATED ENGINEERS, INC.  
> 5802 Research Park Blvd. | Madison, WI  53719
>
> P: 608.236.1175 | F: 608.238.2614  
> fbetz at aeieng.com <mailto:fbetz at aeieng.com>  |  *www.aeieng.com 
> <http://www.aeieng.com/>*  
>
>  
>
>  
>
>  
> ------------------------------------------------------------------------
>
>
>   
>  
> _______________________________________________
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>   
>
>
>
> -- 
> ***********************************************************************
> Thermal Energy System Specialists (TESS), LLC 
> David BRADLEY                      22 N. Carroll Street - Suite 370 
> Partner                            Madison, WI 53703 
>                                    USA
> P: +1.608.274.2577 
> F: +1.608.278.1475
> E-mail: bradley at tess-inc.com <mailto:bradley at tess-inc.com> 
> Web Pages:  http://www.tess-inc.com    and      http://www.trnsys.com
>  
> ***********************************************************************

-- 
***********************************************************************
Thermal Energy System Specialists (TESS), LLC 
David BRADLEY                      22 N. Carroll Street - Suite 370 
Partner                            Madison, WI 53703 
                                   USA
P: +1.608.274.2577 
F: +1.608.278.1475
E-mail: bradley at tess-inc.com 
Web Pages:  http://www.tess-inc.com    and      http://www.trnsys.com

***********************************************************************

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