EV Digest 4865
Topics covered in this issue include:
1) Re: Radiator
by Danny Miller <[EMAIL PROTECTED]>
2) Re: PFC-20 Running off Prius HV Pack
by Lightning Ryan <[EMAIL PROTECTED]>
3) Re: Looking for info about production EVs...
by Evan Tuer <[EMAIL PROTECTED]>
4) RE: Radiator
by "Dewey, Jody R ATC (CVN75 IM3)" <[EMAIL PROTECTED]>
5) RE: Radiator
by Cor van de Water <[EMAIL PROTECTED]>
6) Re: Radiator
by [EMAIL PROTECTED]
7) RE: Battery Analyzer - Keeping track of AHr's w/confidence
by "Mueller, Craig M" <[EMAIL PROTECTED]>
8) Re: Austin mini.
by "steve ollerton" <[EMAIL PROTECTED]>
9) Re: Radiator - optimum coolant flow rate
by "Phil Marino" <[EMAIL PROTECTED]>
10) Re: plugging in at work
by "Joe Strubhar" <[EMAIL PROTECTED]>
11) Re: Bits and Pieces
by "Phil Marino" <[EMAIL PROTECTED]>
12) RE: PFC-20 Running off Prius HV Pack
by "djsharpe" <[EMAIL PROTECTED]>
13) Re: Bits and Pieces - air vs water cooling
by "Phil Marino" <[EMAIL PROTECTED]>
14) Re: Radiator
by "Roland Wiench" <[EMAIL PROTECTED]>
15) Re: Radiator - optimum coolant flow rate
by "Roland Wiench" <[EMAIL PROTECTED]>
16) Heater Options..Heated Water vs Ceramic
by John Wayland <[EMAIL PROTECTED]>
--- Begin Message ---
That is incorrect, with certainty. There is no "sweet spot"; lower flow
rates will always mean a higher heatsink temp. The limiting factor is,
as mentioned before, how much flow it is practical to pump while still
getting enough useful gains to justify the added pressure, pumping
power, and possibly the need to redesign the system with more/wider
passages.
Higher flow rates will mean the heatsink will get cooler. Actually if a
device generates 100W of heat then the system will dissipate 100W of
heat regardless of flow rate, it's a matter of how hot the heatsink and
its semiconductors will be (and the goal here is to keep them cool). A
low flow system not only runs higher heatsink temps but the ultimate
power rating is decreased. A system with good flow might be able to
dissipate 500W without overheating the semiconductors whereas setting
the same system at lesser flow might overheat at 200W.
Danny
Eric Poulsen wrote:
This kinda reminds me of the Amps / Voltage / Power relationship.
Whether you have a high rate of flow, or a low rate of flow, the
dissapated power (heat) is will be the same, while the amount of water
moved, and the temperature differential will be different.
In the end, it appears that a lower rate would be better (to an
extent), since the end goal is to keep the water block (heat sink) at
the lowest temperature possible. At higher flow rates, you'll remove
just as much heat, but the steady-state temperature of the heat sink
will be higher, which is not desirable.
What you have to do is hit the max-power transfer "sweet spot", which
allows low delta T for heat sink / ambient.
--- End Message ---
--- Begin Message ---
The 2004+ Prius's electric "Motor" is rated at 50kW?
Though it actually has 2 motors, MG1 is primarily a
generator and rated at 10kW, MG2 is primarily the traction
motor and rated at 33kW. The battery pack is rated at 21kW.
I might not have these figures right, MG2 might be 50kW and
MG1 might be 13kW or 17kW, can't find the figures at the moment.
Anyway, I'm glad to hear someone has already hooked up
their PFC to a Prius, I always thought that might happen.
L8r
Ryan
ps. We've started a new EAA-PHEV (Plug-in Hybrid EV) project.
Here's the new page for it http://www.seattleeva.org/wiki/EAA-PHEV
Still don't have all the good details there yet, it's only a week old...
--- End Message ---
--- Begin Message ---
PSA group claims that they have sold over 10,000 electric vehicles.
That includes electric versions of the C15 and C25, AX, 106, 205,
Saxo, Partner/Berlingo. Since 2000 I think that the Berlingo is the
only model in production but there are a lot of them about and it is
still on sale as the updated look 2005 model.
Regards
Evan
--
http://www.tuer.co.uk/evs2/myev.html
On 10/28/05, George S. <[EMAIL PROTECTED]> wrote:
> This is a post from Tom Dowling of evchargernews to the rav4ev list earlier
> this year.
>
>
> "Here's what I get, from various sources, searching the archives. Thanks to
> Noel Adams for some corrections to a previous post.
>
> RAV4 EV prior to retail program 1039
> RAV4 EV retail program about 330
> EV1 about 1100
> Ranger EV about 1500
> Ranger EV in USPS body 500
> Chevrolet S10E about 500
> Honda EV Plus about 320
> Nissan Altra about 120
> Chrysler TEVan about 30
> Dodge Epic minivans about 120 Toyota Ecoms about 30 Nissan HyperMinis about
> 50 (maybe more) Th!nk Cities about 550
> The Ranger EV appears to be the record holder.
> Tom Dowling"
>
>
> George S.
>
>
--- End Message ---
--- Begin Message ---
Nope. Two different 160 Thermostats did the same thing. The problem was
the 160 thermostat was ALWAYS open so with the same amount of flow the
radiator couldnt cool it down in the one pass it got. When I put in the 195
thermostat it would close the engine off to the radiator and that gave the
radiator extra time to cool the water before it was pumped back into the
engine. Since my temp sender is right above the thermostat I can watch it
open and close on the dial. When the 160 was in there you could watch the
temps rise to 160 then drop to about 100 as soon as the thermostat opened.
Then the next round it would be 160 open drop to 110. This would continue
until it stayed at 160 and slowly rise all the way to 200. When I switched
to the 195 it would cycle between 200 and 180 and remain relatively
constant. In fact, with the 160 thermostat it was not uncommon for the car
to hit 220-230 when pulling the boat up hills. With the 195 it would go to
210 on the hill and immediately drop to 180-200 after that.
-----Original Message-----
From: Cor van de Water [mailto:[EMAIL PROTECTED]
Sent: Thursday, October 27, 2005 12:55 PM
To: ev@listproc.sjsu.edu
Subject: RE: Radiator
I think your first thermostat was broken.
Cor van de Water
Systems Architect
Email: [EMAIL PROTECTED] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [EMAIL PROTECTED]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3673 eFAX: +31-84-717-9972
Proxim Wireless Networks eFAX: +1-501-641-8576
Take your network further http://www.proxim.com
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Dewey, Jody R ATC (CVN75 IM3)
Sent: Thursday, October 27, 2005 3:08 AM
To: 'ev@listproc.sjsu.edu'
Subject: RE: Radiator
I can speak from experience on that point. My JEEP Cherokee, with a 160
thermostat, ran 210 pulling my boat. When I switched to a 190 thermostat
the engine ran 190 max 195. Giving the radiator time to cool the water
enabled the engine to manage its heat more effeciently.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Wednesday, October 26, 2005 11:01 PM
To: ev@listproc.sjsu.edu
Subject: Re: Radiator
In a message dated 10/26/2005 6:30:22 PM Pacific Standard Time, [EMAIL
PROTECTED]
writes:
<< This should hold true pumping hot water threw a radiator, if you pump it
too fast threw the radiator, it does not stay in long enough for the water
to
cool down. >>
That is an old wives tale.
Faster liquid flow transfers more heat.
(must be my turn to be brusque and borderline inconsiderate..)
Ben
--- End Message ---
--- Begin Message ---
Roland,
In an attempt to bring some science to the stories:
When you move 1 gal/m and lose 60 deg in your floor
or you pump 6 gal/m (6 times as much) and you lose
20 deg in each of those 6 gals, means that although
the temp delta is only 1/3 it happened to 6 times
as much water, so in total you did move twice as
much heat into the floor by pumping 6 gals/min.
Your radator comparable, but it depends on the
relative speeds (as you already indicated):
- if you are pumping fast enough that there is
a "gradient" (constant increase/decrease) of
temperature along the path of water flow, then
your reasoning holds: pumping slower causes a
steeper gradient, so the water coming out of the
radiator is much cooler that it enters, since
the same temp difference happens across the
heat generator, you can also see that the water
exiting the heatsink is much hotter than the water
entering the heatsink when it is moving slower.
That means that in average the heatsink will be
hotter when pumping slower, because your reasoning
that the output temp is lower is false: in practice
the output temp of the radiator will not change so
much (it will go down a little), but the INPUT temp
of the radator will go up and this you will see as
a larger temp delta across the radiator.
In your words:
> This is what I meant, The faster the coolant rate,
> the hotter the coolant is as it exits the radiator.
> Therefore if it's at a slower rated than it must
> exit at a cooler rate. Roland
And I am saying that your BTU calculation is right,
but your reasoning is the wrong direction:
- The faster the coolant flows, the >colder< the coolant
is as it >enters< the radiator. (lower overall temp)
- Therefore if it's at a slower rate, then it must
>enter< at a >higher< temp.
- if you are not pumping fast enough, the transport
of water will affect the heat transfer and no longer
the radiator cooling by air will be the dominant
factor in the cooling.
You will see the effect that the water entering the
radiator will be cooled mainly be the first part of
the radiator, then the temp difference with the
ambient is getting so low that there is no more
cooling in the remainder of the radiator. It does
not help to have such a large radiator that the
water is at ambient temp before is exits, the
cooling is in a limited area, determined by the
flow of water.
Conversely if the flow through the heatsink is too
low, it will quickly heat up the water and the
cooling will mainly be done by the first part
of the heatsink, then the water is at the
heatsink temperature, so only part of the area
is effectively cooling, the termal resistance will
go up and the temp of the transistors will rise.
Again, the cooling is mainly determined by the
speed of water flow at too low speeds.
In all above cases does it make sense to speed up
the flow to achieve better cooling and a larger
heat transfer and lower temperature differences.
That is an effect that you will see everywhere in
nature as it is one of the thermodynamics laws.
NOTE that it depends on *where* you measure temp
to see these effects. For example if you have
the thermometer at the *exit* of the radiator
(I would not know why, maybe install error?)
then you could indeed see the temp go down when
you lower the flow, even though the cooling
would reduce and the *other* side of the cooling
system runs much hotter!
Hope this clarifies,
Cor van de Water
Systems Architect
Email: [EMAIL PROTECTED] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [EMAIL PROTECTED]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3673 eFAX: +31-84-717-9972
Proxim Wireless Networks eFAX: +1-501-641-8576
Take your network further http://www.proxim.com
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Roland Wiench
Sent: Wednesday, October 26, 2005 9:55 PM
To: ev@listproc.sjsu.edu
Subject: Re: Radiator
----- Original Message -----
From: Phil Marino<mailto:[EMAIL PROTECTED]>
To: ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>
Sent: Wednesday, October 26, 2005 9:56 PM
Subject: Re: Radiator
>From: [EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>
>Reply-To: ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>
>To: ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>
>Subject: Re: Radiator
>Date: Wed, 26 Oct 2005 23:00:48 EDT
>
>In a message dated 10/26/2005 6:30:22 PM Pacific Standard Time,
>[EMAIL PROTECTED]
>writes:
>
><< This should hold true pumping hot water threw a radiator, if you pump
>it
>too fast threw the radiator, it does not stay in long enough for the
water
>to
>cool down. >>
>
>That is an old wives tale.
>Faster liquid flow transfers more heat.
>(must be my turn to be brusque and borderline inconsiderate..)
>
>Ben
>
The old wives were right.
Here's why:
The heat that a radiator can lose to the air is predominantly determined
by
the air-to-radiator interface, not the liquid-to-radiator interface, as
long
as you have above a minimum efficient coolant flow. So, the rate of heat
loss ( BTU/hour) of a given radiator is pretty much constant for a given
coolant-air temperature difference, and a given air flow through the
radiator. It doesn't depend on the coolant flow rate.
So, this means that, for example, if you double the liquid coolant flow,
the BTU/hour that the radiator dissipates to the air (and draws from the
liquid coolant) stays essentially the same. But, now twice as much liquid
passes through the radiator per hour. SO, twice as much coolant loses the
same number of BTU's, and the temperature drop of the liquid is about half
of what it was at the lower coolant flow rate.
The faster the coolant rate, the hotter the coolant is as it exits the
radiator. There is no free lunch.
This is what I meant, The faster the coolant rate, the hotter the coolant
is as it exits the radiator. Therefore if it's at a slower rated than it
must exit at a cooler rate. Roland
Phil
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--- End Message ---
--- Begin Message ---
In a message dated 10/28/2005 1:58:08 AM Pacific Standard Time,
[EMAIL PROTECTED] writes:
<< Nope. Two different 160 Thermostats did the same thing. The problem was
the 160 thermostat was ALWAYS open so with the same amount of flow the
radiator couldnt cool it down in the one pass it got. >>
This is a common misconception.
That whole system was designed to run at 195 with the thermostat opening
fairly small to keep pressures high to prevent cavitation at the water pump
impeller blades.
Without the higher pressure, the water pump pushes lots of vapor bubbles into
the engine, and vapor doesnt cool.
Years ago, you could 'band-aid' a poor cooling system with a 160 tstat or
none at all, but it wont always help on modern cars.
Ben
--- End Message ---
--- Begin Message ---
Mueller, Craig M wrote:
>...Have any microprocessors been
>developed to allow users to input vehicle/pack specific variables...
Eric Poulsen Replied:
>>Just about any microprocessor could do this for you. The trick is
>>measuring the values properly, and writing the software to make it
work.
You're exactly right Eric - I plan on using an old laptop with an Ocean
Controls Parallel Port Data Acquisition Module ($85 kit - $125 ready to
go - link below). I use this device to log data in my greenhouse, and OC
provides an excellent, simple to use data logging program which is fully
programmable too. As you state, inputs are the key, but I've had fair
success using simple circuits and calibrating from known sources (e.g.
using a good thermometer in water at several temps to calibrate a
thermister - assuming linearity which is a bit off, but close enough).
I've yet to delve into a ammeter circuit, though.
I've also thought of getting a Z-World microprocessor, but the old
laptop idea is more complete for any given price, and can be far less
expensive (i.e. it isn't too hard to find a 486 laptop for nearly free).
It does seem that there is a bit of a void in the pre-made ranks here.
The only thing close that I've found is the Link 10...our local supplier
(Sun Energy - Mora, MN) quoted me:
Standard Link 10 230.00
0-500 amp prescaler 100.00
500 amp shunt 50.00
or 1000 amp shunt 75.00
Plus shipping
If I progress with the OC stuff, I'll certainly post all the source code
of my program (or, rather, a link to it).
Regards,
Craig M.
http://www.oceancontrols.com.au/data_acquisition/isee.htm
--- End Message ---
--- Begin Message ---
Whats the story with this mini?
I am currently converting a mini to electric. Anyone interested who doesn't
already know? [EMAIL PROTECTED]
Steve
Vehicle needs tranny and motor.
http://www.craigslist.org/nby/car/106878771.html
Lawrence Rhodes
Bassoon/Contrabassoon
Reedmaker
Book 4/5 doubler
Electric Vehicle & Solar Power Advocate
415-821-3519
[EMAIL PROTECTED]
--- End Message ---
--- Begin Message ---
From: Danny Miller <[EMAIL PROTECTED]>
That is incorrect, with certainty. There is no "sweet spot"; lower flow
rates will always mean a higher heatsink temp. The limiting factor is, as
mentioned before, how much flow it is practical to pump while still getting
enough useful gains to justify the added pressure, pumping power, and
possibly the need to redesign the system with more/wider passages.
Higher flow rates will mean the heatsink will get cooler. Actually if a
device generates 100W of heat then the system will dissipate 100W of heat
regardless of flow rate, it's a matter of how hot the heatsink and its
semiconductors will be (and the goal here is to keep them cool). A low
flow system not only runs higher heatsink temps but the ultimate power
rating is decreased. A system with good flow might be able to dissipate
500W without overheating the semiconductors whereas setting the same system
at lesser flow might overheat at 200W.
Danny
You're right - higher coolant flow rates will result in a cooler controller
- but only up to a point. Above a certain flow rate ( which depends on the
radiator, air flow through the radiator, heat sink, and controller heat
generation) it won't help to increase the coolant flow. As the coolant flow
rate increases above that point, the ability of the radiator to lose heat to
the air becomes the limiting factor.
Here is an attempt at describing this as a graph:
*
* x Controller temp
* x
* x
* x
* x
* x
* x
* x
* x
* x
* x
x x x x
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* * * * *
Coolant flow rate
The vertical axis is controller heat sink temperature, and the horizontal
axis is coolant flow rate.
As long as you have enough coolant flow to take full advantage of the
radiator, increasing the flow will not appreciably help. The trick is
determining that optimum flow rate. Above that, you're just wasting pumping
power.
There are two other minor reasons not to pump faster than needed: it would
result in higher system pressure (and reduced reliability) and - this is a
very minor effect - it would actually add unnecessary heat to the system :
the work that the pump does shows up as heat ( frictional pumping losses )
in the system.
Phil
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--- Begin Message ---
I'm afraid that I can't answer that, as most of the bureaucratic nonsense
that we have to put up with defies explanation, in my opinion! You'll have
to ask someone in the NFPA who is responsible for these ideas.
Joseph H. Strubhar
E-Mail: [EMAIL PROTECTED]
Web: www.gremcoinc.com
----- Original Message -----
From: "Eric Poulsen" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Thursday, October 27, 2005 10:23 PM
Subject: Re: plugging in at work
> I'll put this plainly: Why require outdoor outlets?
>
> Joe Strubhar wrote:
>
> >Only on residential buildings, Lee - the NEC does not require outside
> >outlets on commercial buildings.
> >
> >Joseph H. Strubhar
> >
> >E-Mail: [EMAIL PROTECTED]
> >
> >Web: www.gremcoinc.com
> >----- Original Message -----
> >From: "Lee Hart" <[EMAIL PROTECTED]>
> >To: <ev@listproc.sjsu.edu>
> >Sent: Thursday, October 27, 2005 3:44 PM
> >Subject: Re: plugging in at work
> >
> >
> >
> >
> >>[EMAIL PROTECTED] wrote:
> >>
> >>
> >>>Our commercial building where I work does not have a single outside
> >>>outlet... the building company superintendant replied that all the
> >>>company's (many) buildings have no outside outlets so that no-one
> >>>can plug-in a car block heater.
> >>>
> >>>
> >>Check your local building code. Here, outside outlets are *required* by
> >>the building code! It may even be part of the NEC (and so likely to be
> >>required everywhere).
> >>--
> >>"Never doubt that the work of a small group of thoughtful, committed
> >>citizens can change the world. Indeed, it's the only thing that ever
> >>has!" -- Margaret Mead
> >>--
> >>Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
> >>
> >>
> >>
> >>
> >
> >
> >
> >
>
>
--- End Message ---
--- Begin Message ---
From: Danny Miller <[EMAIL PROTECTED]>
When you're talking about these power levels, water cooling is simpler than
trying to manage heat with air cooling.
Even more important, it's nearly impossible to keep semiconductors as cool
with air cooling as they can with water cooling at these power levels.
This directly affects their capabilities, efficiency, and overall
reliability.
This is starting to sound a little like the continuing AC vs DC discussions.
The best choice of cooling method depends on your power levels and your
goals for the vehicle.
For my Echo ( a small, light, low power car with a Curtis controller)
liquid-cooling wouldn't make sense.
I have two small BLDC blowers cooling a finned heat sink on the base of the
controller. As far as reliability, it would be hard to match that with a
liquid cooled system. There is no chance for coolant loss, and the only
possiblity for a single point failure is a loss of the relay that powers the
blowers. (very unlikely at 12V and a few watts) Also, I live in a climate
where the summer temperature is very rarely above 90F, and never above 100F.
For a higher power system,(and/or, in a hotter location) liquid cooling
would certainly be a better - or even, required- choice.
Phil
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--- Begin Message ---
I don't believe these electrical machines have these continuous ratings.
They don't need it anyway. They only provide these levels of power for
short times. Perhaps PHEVs converters might get some surprises.
David
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Lightning Ryan
Sent: Friday, 28 October 2005 7:10 PM
To: ev@listproc.sjsu.edu
Subject: Re: PFC-20 Running off Prius HV Pack
The 2004+ Prius's electric "Motor" is rated at 50kW?
Though it actually has 2 motors, MG1 is primarily a
generator and rated at 10kW, MG2 is primarily the traction
motor and rated at 33kW. The battery pack is rated at 21kW.
I might not have these figures right, MG2 might be 50kW and
MG1 might be 13kW or 17kW, can't find the figures at the moment.
Anyway, I'm glad to hear someone has already hooked up
their PFC to a Prius, I always thought that might happen.
L8r
Ryan
ps. We've started a new EAA-PHEV (Plug-in Hybrid EV) project.
Here's the new page for it http://www.seattleeva.org/wiki/EAA-PHEV
Still don't have all the good details there yet, it's only a week old...
--- End Message ---
--- Begin Message ---
From: Victor Tikhonov <[EMAIL PROTECTED]>
Reply-To: ev@listproc.sjsu.edu
To: ev@listproc.sjsu.edu
Subject: Re: Bits and Pieces
Date: Thu, 27 Oct 2005 22:18:26 -0700
Neon John wrote:
I view that as a great negative. Not having a coolant system to mess
with and maintain is a big benefit of EVs to me. I just can't see a
benefit of water cooling sufficient to offset the hassles and added
complications.
John
I've done it both ways on very the same ACRX. Having stock radiator,
it is so much easier to have water cooled everything. You can keep things
in totally enclosed compartments. Not sure what your
definition of "hassle" is, but I think it would be much more
irritating to slow down on a freeway because your controller or
motor overheats on the long incline.
After comparing both, I'll never do a conversion with air cooled
hardware. BTW, no fans noise ever - only cabin heater blower fan
if in use.
As always, this may not be applicable to some conversions, although
I don't see water cooling to be disadvantage in *any* situation.
Victor
I can see at least one major disadvantage to water cooling - reliability.
In a book about sailing that I read many years ago; - I can't recall the
name of the book - William F Buckley defined a luxury on a sailboat as
anything that " when it breaks down, you can fix it at sea".
In all of my years of driving, I have had to have a car towed ( unrepairable
by me on the side of the road) three times. Once was an electrical problem,
and twice it was cooling system failure ( loss of coolant due to component
failure).
An air-cooled system will never fail because of a leak.
As far as avoiding overheating - that depends on the design of the system,
not on the method.
You can have an inadequate water-cooled system, and you can have a well
designed, more than adequate, air cooled system.
More complex and expensive isn't always better.
Phil
-
'91 ACRX - something different
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--- Begin Message ---
I just turn on my floor heating system on last week. I than went back to see
the difference of heat removable, by adjusting one zone to 1 gallon per minute
vs 6 gallon per minute.
When the zone loop is up to temperature, 140 degrees, it circulates its in own
loop until its gets down to 120 degrees. At 120 degrees, the boiler hot water
is added or in the circulation loop of the boil to bring the temperature back
up to 140 degrees.
I have a elaspe time clock on the boiler startup and shut down and a another
clock on the zone loop. I did this years ago to see how long the boiler is on
per 24 hours a day at a certain outside to inside temperature difference
monitor by outside/inside thermostats. The outside thermo can vary the flow of
the pumps if I put it into Auto position.
I also have floor temperature sensors, one at ceiling and one at 60 inches off
the floor.
I put the pump control on manual position and one zone to 1 gpm. I than time
when the room thermostat come on. The zone temperature was up to 140 degrees
at the feed and in one minute of circulation, the return temperate was at 80
degrees.
The wall thermostats have a 2 degree differential, 1 degree up and 1 degree
down below the set temperature and is set to 72 degrees. The outside
temperature is 39 degrees.
The thermo trip off in 1 minute and 55 seconds.
The zone feed temperature is now 133 degrees, and the return is 83 degrees.
The next day when the same outside temperature was the same and the room
temperature set at 72 degrees. Both days, there is no wind and its cloudy.
I now adjusted the same zone pump to 6 gpm with the same 140 degree feed
temperature. This time the zone return temperature quickly rise to 110 degrees
in 1 minute. The room thermostat took 4 minutes and 23 seconds to turn off
which is the same run time as the zone pumps. The boiler temperature is again
at 133 degrees after that amount of time.
The Heat Way floor heat manual and even talking to one of there engineers, they
say its best to have the zone flow values adjusted so that the temperature
difference between the feed and return not to be less than 20 degrees, other
wise the heat absorbing takes longer making the pumps run longer.
Now, I'am going have to go and test out that 160 degree themostat vs a 195
degree thermostat in my sports car engine. My engine does not used a set in
themostate. It uses a remote electric circulation pump and electric fan, that
is thermostat operated by a thermo sensor on the thermo housing which is a
standard intake manifold.
This type of system shuts down the circulation threw the radiator and the water
is circulated threw the engine only during warm up.
It does seems very logical to me, that the lower thermo will allow higher
temperature water return back to engine, because its does not hold the coolent
longer in the radiator.
It will be awhile, before I test this out, because this car is undergoing a
complete overhauling and customizing.
Roland
----- Original Message -----
From: Cor van de Water<mailto:[EMAIL PROTECTED]>
To: ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>
Sent: Friday, October 28, 2005 4:31 AM
Subject: RE: Radiator
Roland,
In an attempt to bring some science to the stories:
When you move 1 gal/m and lose 60 deg in your floor
or you pump 6 gal/m (6 times as much) and you lose
20 deg in each of those 6 gals, means that although
the temp delta is only 1/3 it happened to 6 times
as much water, so in total you did move twice as
much heat into the floor by pumping 6 gals/min.
Your radator comparable, but it depends on the
relative speeds (as you already indicated):
- if you are pumping fast enough that there is
a "gradient" (constant increase/decrease) of
temperature along the path of water flow, then
your reasoning holds: pumping slower causes a
steeper gradient, so the water coming out of the
radiator is much cooler that it enters, since
the same temp difference happens across the
heat generator, you can also see that the water
exiting the heatsink is much hotter than the water
entering the heatsink when it is moving slower.
That means that in average the heatsink will be
hotter when pumping slower, because your reasoning
that the output temp is lower is false: in practice
the output temp of the radiator will not change so
much (it will go down a little), but the INPUT temp
of the radator will go up and this you will see as
a larger temp delta across the radiator.
In your words:
> This is what I meant, The faster the coolant rate,
> the hotter the coolant is as it exits the radiator.
> Therefore if it's at a slower rated than it must
> exit at a cooler rate. Roland
And I am saying that your BTU calculation is right,
but your reasoning is the wrong direction:
- The faster the coolant flows, the >colder< the coolant
is as it >enters< the radiator. (lower overall temp)
- Therefore if it's at a slower rate, then it must
>enter< at a >higher< temp.
- if you are not pumping fast enough, the transport
of water will affect the heat transfer and no longer
the radiator cooling by air will be the dominant
factor in the cooling.
You will see the effect that the water entering the
radiator will be cooled mainly be the first part of
the radiator, then the temp difference with the
ambient is getting so low that there is no more
cooling in the remainder of the radiator. It does
not help to have such a large radiator that the
water is at ambient temp before is exits, the
cooling is in a limited area, determined by the
flow of water.
Conversely if the flow through the heatsink is too
low, it will quickly heat up the water and the
cooling will mainly be done by the first part
of the heatsink, then the water is at the
heatsink temperature, so only part of the area
is effectively cooling, the termal resistance will
go up and the temp of the transistors will rise.
Again, the cooling is mainly determined by the
speed of water flow at too low speeds.
In all above cases does it make sense to speed up
the flow to achieve better cooling and a larger
heat transfer and lower temperature differences.
That is an effect that you will see everywhere in
nature as it is one of the thermodynamics laws.
NOTE that it depends on *where* you measure temp
to see these effects. For example if you have
the thermometer at the *exit* of the radiator
(I would not know why, maybe install error?)
then you could indeed see the temp go down when
you lower the flow, even though the cooling
would reduce and the *other* side of the cooling
system runs much hotter!
Hope this clarifies,
Cor van de Water
Systems Architect
Email: [EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]> Private:
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-----Original Message-----
From: [EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]> [mailto:[EMAIL PROTECTED]
Behalf Of Roland Wiench
Sent: Wednesday, October 26, 2005 9:55 PM
To: ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>
Subject: Re: Radiator
----- Original Message -----
From: Phil Marino<mailto:[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
To:
ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>>
Sent: Wednesday, October 26, 2005 9:56 PM
Subject: Re: Radiator
>From: [EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]<mailto:[EMAIL
PROTECTED]<mailto:[EMAIL PROTECTED]>>
>Reply-To:
ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>>
>To:
ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>>
>Subject: Re: Radiator
>Date: Wed, 26 Oct 2005 23:00:48 EDT
>
>In a message dated 10/26/2005 6:30:22 PM Pacific Standard Time,
>[EMAIL PROTECTED]
>writes:
>
><< This should hold true pumping hot water threw a radiator, if you pump
>it
>too fast threw the radiator, it does not stay in long enough for the
water
>to
>cool down. >>
>
>That is an old wives tale.
>Faster liquid flow transfers more heat.
>(must be my turn to be brusque and borderline inconsiderate..)
>
>Ben
>
The old wives were right.
Here's why:
The heat that a radiator can lose to the air is predominantly determined
by
the air-to-radiator interface, not the liquid-to-radiator interface, as
long
as you have above a minimum efficient coolant flow. So, the rate of heat
loss ( BTU/hour) of a given radiator is pretty much constant for a given
coolant-air temperature difference, and a given air flow through the
radiator. It doesn't depend on the coolant flow rate.
So, this means that, for example, if you double the liquid coolant flow,
the BTU/hour that the radiator dissipates to the air (and draws from the
liquid coolant) stays essentially the same. But, now twice as much liquid
passes through the radiator per hour. SO, twice as much coolant loses the
same number of BTU's, and the temperature drop of the liquid is about half
of what it was at the lower coolant flow rate.
The faster the coolant rate, the hotter the coolant is as it exits the
radiator. There is no free lunch.
This is what I meant, The faster the coolant rate, the hotter the coolant
is as it exits the radiator. Therefore if it's at a slower rated than it
must exit at a cooler rate. Roland
Phil
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--- Begin Message ---
----- Original Message -----
From: Phil Marino<mailto:[EMAIL PROTECTED]>
To: ev@listproc.sjsu.edu<mailto:ev@listproc.sjsu.edu>
Sent: Friday, October 28, 2005 7:07 AM
Subject: Re: Radiator - optimum coolant flow rate
>From: Danny Miller <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
>
>That is incorrect, with certainty. There is no "sweet spot"; lower flow
>rates will always mean a higher heatsink temp. The limiting factor is, as
>mentioned before, how much flow it is practical to pump while still getting
>enough useful gains to justify the added pressure, pumping power, and
>possibly the need to redesign the system with more/wider passages.
>
>Higher flow rates will mean the heatsink will get cooler. Actually if a
>device generates 100W of heat then the system will dissipate 100W of heat
>regardless of flow rate, it's a matter of how hot the heatsink and its
>semiconductors will be (and the goal here is to keep them cool). A low
>flow system not only runs higher heatsink temps but the ultimate power
>rating is decreased. A system with good flow might be able to dissipate
>500W without overheating the semiconductors whereas setting the same system
>at lesser flow might overheat at 200W.
>
>Danny
>
You're right - higher coolant flow rates will result in a cooler controller
- but only up to a point. Above a certain flow rate ( which depends on the
radiator, air flow through the radiator, heat sink, and controller heat
generation) it won't help to increase the coolant flow. As the coolant flow
rate increases above that point, the ability of the radiator to lose heat to
the air becomes the limiting factor.
Here is an attempt at describing this as a graph:
*
* x Controller temp
* x
* x
* x
* x
* x
* x
* x
* x
* x
* x
x x x x
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* * * * *
Coolant flow rate
The vertical axis is controller heat sink temperature, and the horizontal
axis is coolant flow rate.
As long as you have enough coolant flow to take full advantage of the
radiator, increasing the flow will not appreciably help. The trick is
determining that optimum flow rate. Above that, you're just wasting pumping
power.
There are two other minor reasons not to pump faster than needed: it would
result in higher system pressure (and reduced reliability) and - this is a
very minor effect - it would actually add unnecessary heat to the system :
the work that the pump does shows up as heat ( frictional pumping losses )
in the system.
Phil
Finally, someone shows that a higher flow is needed in a heat sink to get
cooler. The lower flow will increase the heat sink temperature. Therefore
isn't it logical that a radiator being a heat sink needs a lower flow to
increase the radiator temperature.
Would it not be best to have two circulation circuits, one threw the heat
sink at one flow rate and threw the radiator at a different flow rate. You can
used one pump with ball valves to adjust the different flows or use two pumps
with flow adjusters which both loops circulates back to a holding tank.
There is many different diagrams of how this can be done. I don't have any
at the moment. There should be some diagrams under Hot Water Heating Systems
on the WEB.
Roland
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--- Begin Message ---
Hello to All,
I've found the ongoing discussion on heated liquid type vs ceramic type
heaters very interesting.
Ryan Bohm wrote:
How long does it take when using this unit for hot air to begin
flowing on a really cold morning?
Victor Tikhonov wrote:
About 3 min. I do realize people will brag about 3 seconds for
their ceramic heaters. I'm sure they won't die if waiting 3 minutes.
I've always used the things an EV does better than a gas car, as a
selling point with those not yet convinced. The instant-on heat that a
properly done ceramic heater provides, is such an item. I also,
absolutely hate shivering in my car waiting, and waiting, and waiting
for the damn infernal combustion engine to make its water hot enough to
provide warmth.
How often do you hear complaints about that?
All the time, actually. Conversely, especially when I had Red Beastie
with its twin elements, everyone loved the instant heat on those c-cold
frosty Winter mornings. It got to where my wife and I wouldn't want to
be in any of our other cars when it got really cold out, as we'd head
straight for the electric pickup with its instant-on killer heater.
It's sure nice to have as short time as possible, but it is not
acceptable (to me) to jeopardize safety for few more dollars.
I'd have to disagree with you on this, my friend. There is far more
inherent danger in a a temp regulator or pressure switch failing and
having steam build up and burst pipes and or hoses to spray scalding
steam on persons, than in a ceramic element melting things. The key to
both systems though, is a properly done installation. I've always
mounted the ceramic elements with an aluminum shroud around them so that
plastic is not adjacent to the element. An over-temp cutout module can
also be added near the element in the case of a fan failure. Liquid type
heaters, too, can have the appropriate safety protections. I think the
safety aspect comparing both types, is a wash.
Also not worth to reap apart the dash. People accept this of course
to save money, and this is fine - everyone makes choices according
to their priorities.
Not ripping the dash apart by using a warmed liquid type is very
attractive. Ripping the dash apart in order to get instant on heat
without any liquid that can leak and spill, is also very attractive. The
idea of having a bad heater core than can get clogged or leak and ooze,
goes away with a ceramic element, too.
I love my ceramic heater element, but after the first time my safety
system was circumvented and the cabin of my EV stunk of burnt
plastic, I decided your type of system might be worth the few hundred
bones.
In 20+ years of using these elements in perhaps 40-50 EV conversions,
not once, has that problem ever happened to me...that's a pretty good
record. On the other hand, the warmed liquid heaters I've had in EVs
'have' had bad hoses, bad clamps, leaks, etc. And 'all' of them made me
wait for heat and were nearly as miserable on cold mornings as a gas
car's heater.
Wonder why no OEM is even considering something like that. 10x (or more)
cheaper! Who can resist?
Victor, you're wrong on this. The first gen. Prius used a lower power
rated ceramic heater to supplement the warmed liquid type that blew cold
air when the ICE was off. The GM EV1 also had a ceramic element to
supplement its lame heat pump system. If batteries had way more storage
capacity and conserving precious amps wasn't such a high priority, all
factory EVs would have ceramic elements. Hybrids with their ICEs of
course, have all that hot water in them anyway, so of course they'll
always make use of it.
On the flip side... the newer cars are far harder to work on when it
comes to the dash and its often times hidden heater core. The warmed
liquid type heater is a nice option for these, and as Victor says, it
does only take about 3 minutes to get heat output, and for many, that's
an acceptable compromise.
I love using the ceramic elements and vastly prefer using them over
warmed liquid type heating systems. On the other hand, if I ever tear my
Insight apart and convert it over to pure electric, I would consider
using a warmed liquid type system that would allow me to keep the car's
excellent heater-AC system in tact, and then probably complain about
having to wait for the thing to warm up all the time :-)
Those nifty instant heat producing ceramic elements can really spoil you.
See Ya....John Wayland
--- End Message ---
