[TRNSYS-users] Type1 Number of identical collectors in series has no effect

Mon Oct 24 01:22:10 PDT 2016

Thanks again David

It is not exactly what I meant though. Please consider the 2 cases below
(all other parameters and inputs being equal) computed with Type1b.

I get the exact same results in the 2 cases: is it physically consistent?

Type

Variable

Case 1

Case 2

Unit

Param

Number in series

1

6

-

Param

Collector area

100

100

m^2

Param

Tested flow rate

70

70

kg/hr.m^2

Input

Inlet flowrate

5000

5000

kg/hr

Best

--

Antoine Gautier

Solamen

+33 6 58 24 02 60

antoine.gautier at solamen.fr

De : David BRADLEY [mailto:d.bradley at tess-inc.com] 
Envoyé : jeudi 20 octobre 2016 23:35
À : Antoine Gautier <antoine.gautier at solamen.fr>; 'TRNSYS users mailing list
at OneBuilding.org' <trnsys-users at lists.onebuilding.org>
Objet : Re: [TRNSYS-users] Type1 Number of identical collectors in series
has no effect

Antoine,

  There is usually some difference in results. The collectors run more
efficiently when all of them are in parallel because there is no efficiency
penalty for the increasing inlet temperature to each collector in series
after the first one. If all of the inputs are set correctly then the flow
rate through any given collector in the two scenarios (12 in parallel or 2
sets of 6 in parallel) should be exactly the same (thus there should not be
any effect of the flow rate on the efficiency). You will, of course, get
some increase in the amount of power drawn by the pump because in the "12 in
parallel" case you have to provide a higher flow rate (although with a lower
pressure drop)

best,

 David

On 10/20/2016 15:09, Antoine Gautier wrote:

Thanks a lot David!

Sorry I had you taking me by the hand like that. 

I must say that my insistence pertains to the following observation: only
changing "number in series" from 6 to 1 leads to the exact same results. 

I find it really strange

The new system modelled should be an array of Ntotal collectors connected in
parallel and thus receiving M/Ntotal flowrate (Nseries=1).

Does this mean that the drop in efficiency due to lower flowrate is exactly
balanced by the raise in efficiency due to lower average temperature (each
collector now being supplied directly with water at array inlet
temperature)?

--

Antoine Gautier

Solamen

+33 6 58 24 02 60

antoine.gautier at solamen.fr <mailto:antoine.gautier at solamen.fr> 

De : David BRADLEY [mailto:d.bradley at tess-inc.com] 
Envoyé : jeudi 20 octobre 2016 21:43
À : Antoine Gautier  <mailto:antoine.gautier at solamen.fr>
<antoine.gautier at solamen.fr>; 'TRNSYS users mailing list at OneBuilding.org'
<mailto:trnsys-users at lists.onebuilding.org>
<trnsys-users at lists.onebuilding.org>
Objet : Re: [TRNSYS-users] Type1 Number of identical collectors in series
has no effect

Antoine,

 That is correct so long as "A" is the area of the full array (12 times the
area of a single module) and so long as "M" is twice the flow rate that you
want to go through each collector. Mathematically:

M = X * Ntotal / Nseries

where M is the pump flow rate, X is the flow rate per collector, Ntotal is
the total number of collectors (12), and Nseries is the number of collectors
in series per parallel path (6).

best,

 David

On 10/20/2016 14:20, Antoine Gautier wrote:

Sorry David I still have some doubts

Here is a schematic.

Within each row, the collectors are connected in series. 

The pump flowrate is M. The total array area is A.

I can model this with Type1 considering:

Number in series=6

Collector area=A

Inlet flowrate=M

Is this correct?

Thanks again.

--

Antoine Gautier

Solamen

+33 6 58 24 02 60

antoine.gautier at solamen.fr <mailto:antoine.gautier at solamen.fr> 

De : David BRADLEY [mailto:d.bradley at tess-inc.com] 
Envoyé : jeudi 20 octobre 2016 20:44
À : Antoine Gautier  <mailto:antoine.gautier at solamen.fr>
<antoine.gautier at solamen.fr>; 'TRNSYS users mailing list at OneBuilding.org'
<mailto:trnsys-users at lists.onebuilding.org>
<trnsys-users at lists.onebuilding.org>
Objet : Re: [TRNSYS-users] Type1 Number of identical collectors in series
has no effect

Antoine,

  I'm not 100% sure that I follow your logic but you can model that array
with a single instance of Type1. If your single module has an area of 1m2
and wants a flow rate of 400kg/h then the full array of 50 modules (10 in
parallel, 5 in series) would have:

area = 50 m2

number in series = 5

flow rate = 4000kg/h (400kg/h x 10 in parallel)

best,

 David

On 10/20/2016 13:30, Antoine Gautier wrote:

Thanks David

Just to be sure

Considering an array of 50 collectors = 10 parallel-connected rows of 5
series-connected collectors, total inlet flowrate of array = M, total area =
A.

I cannot model the whole array with Type1 only: I need to add an equation
multiplying the flowrate and energy rate computed by Type1 by the number of
rows. Type1 parameters and inputs being the following:

Number in series=5

Collector area=A/10

Inlet flowrate=M/10

Right?

--

Antoine Gautier

Solamen

+33 6 58 24 02 60

antoine.gautier at solamen.fr <mailto:antoine.gautier at solamen.fr> 

De : David BRADLEY [mailto:d.bradley at tess-inc.com] 
Envoyé : jeudi 20 octobre 2016 19:24
À : Antoine Gautier  <mailto:antoine.gautier at solamen.fr>
<antoine.gautier at solamen.fr>; TRNSYS users mailing list at OneBuilding.org
<mailto:trnsys-users at lists.onebuilding.org>
<trnsys-users at lists.onebuilding.org>
Objet : Re: [TRNSYS-users] Type1 Number of identical collectors in series
has no effect

Antoine,

  This is a common source of confusion. Two points are important to keep in
mind. First, the collector array area parameter is the area of the entire
array, not just the area of one module in the array. Second, if you add a
second collector you have to be careful about what you do with the flow
rate. If you are adding a second collector in parallel to the first one you
should double the collector array area, leave the "number in series"
parameter set to 1, and double the liquid flow rate to the array. If you are
adding a second collector in series with the first one, you should double
the collector array area, set the number in series to 2, and leave the
liquid flow rate unchanged.

kind regards,

 David

On 10/20/2016 11:46, Antoine Gautier via TRNSYS-users wrote:

Hi

I cannot figure out why the number of collectors in series has no effect on
the collectors array efficiency: see attached project.

Computing equations from source code manually I would state the opposite

Thanks for your help.

Best regards

--

Antoine Gautier

Solamen

+33 6 58 24 02 60

antoine.gautier at solamen.fr <mailto:antoine.gautier at solamen.fr> 

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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 <mailto:d.bradley at tess-inc.com> 

http://www.tess-inc.com
http://www.trnsys.com

-- 
***************************
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 <mailto:d.bradley at tess-inc.com> 

http://www.tess-inc.com
http://www.trnsys.com

-- 
***************************
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 <mailto:d.bradley at tess-inc.com> 

http://www.tess-inc.com
http://www.trnsys.com

-- 
***************************
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 <mailto:d.bradley at tess-inc.com> 

http://www.tess-inc.com
http://www.trnsys.com
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