[bldg-sim] Pump location

[K Emerson]

Varkie, 

I certainly agree with what Eric states.  Plate-frame
heat exchangers are probably not the best choice for
high pressure applications.  In addition, look out for
pressure drop if you are trying to stuff a lot of
water through a few plates.  

Pump location really doesn't matter except that you
have to watch out for what is called "net positive
suction head" or "NPSH".  Basically, if you put the
pump suction in a low pressure situation
(intentionally or unintentionally) you can tear up the
pump with cavitation.  

Keith Emerson

--- "Kirchhoff, Eric" <EKirchhoff at semprasolutions.com>
wrote:
> From design experience, plate-frame heat exchangers
> can be quite expensive,
> particularly when you have to rate the HX for high
> pressures.  There are two
> kinds of plate HXs, gasketed and soldered.  Getting
> a soldered type sort of
> defeats one of the main advantages of a plate-frame
> type HX, its
> expandability.  The gasketed type for high-pressure
> applications are less in
> supply and as a result cost a lot.  The
> highest-pressure rating I've seen
> for a gasketed-type plate-frame HX is 300 psia.
>  
> My following comments apply to a gasketed-type
> plate-frame heat exchanger.
>  
> (1) How high do you want to go?  This is really an
> indirect question related
> to the fill pressure of the system, the location of
> the expansion tank, and
> the location of the HX in the system.  Note that
> when you fill the system,
> you need an addition 2 to 5 psig of pressure to
> allow the water to spit out
> of the top of the system, ensuring the entire system
> is filled and most (if
> not all) of the air is out.  (2) By putting the HX
> at the pump discharge
> means you will feel the full impact of the dynamic
> head of the pump and
> static head of the system at that location.  Not the
> best place in large
> systems like campuses or district energy plants. (3)
> When including the
> comments provided in (2) previously, one can then
> note that you can
> eliminate the dynamic head from the equation.  (4)
> HX exposed to all of the
> static head plus the dynamic head depending upon the
> placement of the pump
> in relation to the HX.  (5) Your static head is
> minimum, and dynamic head is
> again only that contribution depending on the pump's
> placement in relation
> to the HX.  Note this is probably your cheapest
> plate-frame HX since the
> pressure is probably the lowest (assuming the
> expansion tank is also located
> at the suction inlet of the pump).  (6) I don't know
> exactly what you mean
> here.
>  
> As for what are the issues when the HX is replaced
> with other equipment such
> as chillers and boilers:  this will depend upon the
> system you are dealing
> with.  Are there existing chillers and boilers being
> displaced by this
> replacement?  Why?  Is it of economic benefit to the
> owner?  Higher
> efficient device?  Perhaps you are referring to the
> approach temperature.
> Note the closer the approach temperature, the more
> expensive the heat
> exchanger.  However, the closer the approach
> temperature, the more efficient
> the system.  For example, if you have a
> chilled-water system circulating
> water at a 14 delta T, and you have a heat exchanger
> with a 2 degree
> approach, then the load side of the heat exchanger
> operates at a 10 degree
> delta T.  If you have the same chiller system
> circulating water at 14
> degrees delta T and you have a 1-degree approach,
> then your load side of the
> heat exchanger can operate at a 12-degree delta T. 
> As you can intuitively
> see, the one-degree approach HX provides for a more
> efficient system.
>  
>  
> Sincerely,
>  
> Eric Kirchhoff, PE
>  
>  
> -----Original Message-----
> From: Varkie Thomas [mailto:Varkie.Thomas at som.com]
> Sent: Wednesday, December 17, 2003 3:05 PM
> To: bldg-sim at gard.com
> Subject: [bldg-sim] Pump location
>  
> I am looking for information (articles, research
> papers, case studies) on
> the effect of the location of the pump relative to a
> plate and frame heat
> exchanger in a closed piping system.  Some of the
> issues are (1) the
> vertical height of the piping system (1000' to
> 2000'), how high can you go,
> (2) pumping thru HX, (3) pumping away from HX, (4)
> pump and HX located at
> bottom of system, (5) pump and HX at top of system,
> and (6) pump start up.
> What are the issues when the HX is replaced with
> other equipment such as
> chillers and boilers?
>  
> Varkie Thomas
> Skidmore, Owings & Merrill
> 312-360-4467
>  
>  
>  
>
=====================================================You
> received this
> e-mail because you are subscribed 
> to the BLDG-SIM at GARD.COM mailing list.  To
> unsubscribe 
> from this mailing list send a blank message to 
> BLDG-SIM-UNSUBSCRIBE at GARD.COM
> 
> 
>
======================================================
> You received this e-mail because you are subscribed 
> to the BLDG-SIM at GARD.COM mailing list.  To
> unsubscribe 
> from this mailing list send a blank message to 
> BLDG-SIM-UNSUBSCRIBE at GARD.COM


__________________________________
Do you Yahoo!?
New Yahoo! Photos - easier uploading and sharing.
http://photos.yahoo.com/

======================================================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM