Date: Fri, 17 Feb 2012 17:11:21 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Function of Heater Box Baffle Plate????
In-Reply-To: <4f3d633e.4501e70a.565c.1886@mx.google.com>
Content-Type: text/plain; charset="US-ASCII"
In designing heat exchanger systems there are a lot of factors that need to
be considered. There is a lot of science here. There are systems where the
goal is to transfer as much heat as possible. Most are designed this way.
Automotive heaters that only use fresh are more designed to consider air
temperature rise. This is the vanagon front heater for sure. There also is a
consideration for the coolant temperature drop and flow back to the engine.
Performance is often based on approach temperatures. For many systems things
are sized to produce say a 20F rise and have the medium (coolant) outlet
temp drop by also 20F. At 0F outside a 20F rise won't do us any good and we
don't want to send a lot of 40F coolant back to the engine. Also we don't
want the air just blowing through a small part of the coil which it could do
at low fan speeds. So that baffle does serve a number of purposes. I would
leave it in. From experience the front heater works extremely well until the
core is clogged from road dirt on the outside and coolant crud on the
inside. The rear heater is extremely effective as the air source is
recirculated. If getting poor performance up front you need to do some
testing to find out why. There may be a design issue with the Subaru engine
having enough flow to support the two heaters. A booster pump or a plumbing
change can help this.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Derek Drew
Sent: Thursday, February 16, 2012 3:11 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Function of Heater Box Baffle Plate????
There is a baffle plate inside the front heater box that appears to block
most of the air from getting to the heat exchanger.
Only about 1/4 of the heat exchanger is actually getting air because of this
bafffle, which has holes in it, mostly along one side.
Does anybody know what the function is of this baffle plate, or whether
cutting a few more holes in it might increase the heat available?
According to an extremely unscientific polling at samba at
http://www.thesamba.com/vw/forum/viewtopic.php?t=277650 removing the baffle
plate seems to make little difference but might offer a little improvement.
But I cannot imagine that the plate is there for no reason as somebody
obviously went to a lot of trouble to make it.
You can see a picture of a baffle plate where somebody drilled a lot of new
holes in the middle section here:
http://images.thesamba.com/vw/gallery/pix/419753.jpg
Is this a folly idea????????? , or what is the downside????
Notwithstanding the people who said they were happy they removed their
baffle, one person on samba once said: "I have heard that if the baffle is
missing, that the heat output from the front core will be minimal. If the
flow through the core is decent, then I'd be tempted to see if that is
present."
In response to this, Terry K blurted out, as he tends to do in an incendiary
manner, "He-she is dead wrong. You obviously personally haven't been into a
heater box ever."
_______________________________________________
Derek Drew
Washington DC / New York
derekdrew@derekmail.com
Email is best normally but...
PHONE: 202-966-7907 (Call the number at left normally) (alt/cell for
diligent calling only): 703-408-1532
