DC Pumps [RE-wrenches]

[Allan Sindelar]

----- Original Message -----
From: Jeffrey Wolfe, Global Resources <global at sover.net>

One note for those who may want to size a system with super low friction
drop. Do not decrease the velocity in any heat exchanger below about 3 feet
per second. (This is both in-tank exchangers and fin tube radiation. I'm
not as familiar with radiant heat tubing sizing.) Otherwise, the flow
becomes laminar and the heat transfer goes WAY down, effectively making the
system not work. (You can buy special heat exchangers for lower velocity,
but they need to be designed to create the turbulence required for good
heat transfer.)

There is a related concern that we learned the hard way on one job. Use a
cast iron boiler heat exchanger, not a copper one. The copper transfers
burner heat so quickly to the fluid that is a low-flow situation, such as
with DC circulators, you can get flash boiling in the water jacket that
causes obnoxious banging noises (and maybe other damage as well). We added a
DC circulator loop through a copper boiler that operated in tandem with each
of the DC circulators, in order to increase flow and reduce this.

Allan at Pos Energy

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email To: RE-wrenches-unsubscribe at topica.com
This email was sent to: michael.welch at homepower.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================