quote:

---

> Hi, Dave.
>
> Why heating in summer? Unless you're talking Patagonia in the upcoming
> months.

quote:

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> Re the heat exchanger: think "counter-flow." You can get pretty close
> to having the discharge temp of one fluid at the entry temp of the
> other. Much preferable to the simple cross-flow you seem to have been
> thinking of.

quote:

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>
> In other words, given a temperature differential of, say, 10 degrees F,
> between the thermal mass and the air, and an airflow of (number), how
> much can I change the temperature of the air by blowing it through
> said radiator full of cold water?

quote:

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>
> Dave Hinz
>

quote:

---

>
> "Dave Hinz" <DaveHinz@spamcop.net> wrote in message
> news:3ho56bFhtudcU12@individual.net...
>
> First, have you actually measured the temperature differential?

quote:

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> Two
> thoughts; (not that I want to discourage you) (1) Whatever the temperature
> differential is without the system running, it will be significantly less after
> a few hours of operation.

quote:

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> (2) Unless you are able to cool your room air below
> the dew point, you won't get any dehumidification.

quote:

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> On 20 Jun 2005 12:35:54 -0700, barry@sme-online.com <barry@sme-online.com>

quote:

---

>
> No, I'm trying to cool the house by dumping the heat from the upstairs
> air, into the downstairs slab.
>
>
> But, I need a water to air heat exhchanger at some point, because the
> water is how I'll get that heat into the slab. I think?

quote:

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> OK, so I've got hydronic tubing in my basement and kitchen floors, which
> works great for heating those areas in the summer. But, I got to
> thinking - during the summer, the temperature of the slab is _below_ the
> temperature of the air upstairs, and no matter how I pull the forced
> air, the basement is always considerably cooler than the rest of the
> house.
>
> I was wondering if anyone has run a water to air heat exchanger (OK, a
> radiator), similar to an A-coil for A/C, to dump the heat from the air
> into the water (and the slab). Does anyone have any starting points for
> calculations for something like this?
>
> In other words, given a temperature differential of, say, 10 degrees F,
> between the thermal mass and the air, and an airflow of (number), how
> much can I change the temperature of the air by blowing it through
> said radiator full of cold water?

quote:

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> On 20 Jun 2005 12:35:54 -0700, barry@sme-online.com <barry@sme-online.com> wrote:

quote:

---

>
> No, I'm trying to cool the house by dumping the heat from the upstairs
> air, into the downstairs slab.

quote:

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> But, I need a water to air heat exhchanger at some point, because the
> water is how I'll get that heat into the slab. I think?

quote:

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>
>Dave Hinz <DaveHinz@spamcop.net> wrote:
>
>
>These guys make water to air heat exchangers (chiller coils), and they and
>they provide design information in the form of temperatures in and out, flow
>rates etc.

quote:

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> First, have you actually measured the temperature differential? Two
> thoughts; (not that I want to discourage you) (1) Whatever the
> temperature differential is without the system running, it will be
> significantly less after a few hours of operation.

quote:

---

>
> "Dave Hinz" <DaveHinz@spamcop.net> wrote in message
> news:3hokifFi53r3U1@individual.net...

quote:

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>
> Just how is that going to help you? Once the slab warms up then the heat is
> going to rise and ........

quote:

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> Passive cooling works well if you can maintain a temp difference greater
> than 10 F. Since the upstairs is constantly gaining heat you have to have a
> medium that can get rid of it. Storing it below is not an answer.

quote:

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>
[vbcol=seagreen]
> You might be able to make a educated guess from their tables. Their coils
> are typically used the other way around -- cool water through the coils to
> cool warm air, but I don't see why they would not work about the same way in
> reverse.

quote:

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> Bear in mind that you will be heating the basement as you cool the upstairs.

quote:

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> A fan that blows air from the basement to the upstairs would seem to be a
> lot simpler if there is a place to put one?

quote:

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> Another more complex arrangement (but with more benefits) would be to add
> solar collectors on your roof and a storage tank in be basement. In the
> winter the collectors could collect heat and lower your heating bills. In
> the summer you could circulate water through the collectors at night to cool
> the water in the storage tank, then during the day circulate the cooled
> water through the floor. The water circulated through the collectors at
> night will cool by radiation to the sky.

quote:

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> Dave Hinz wrote:

quote:

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>
> Maybe you should simply vent the heat from the upstairs air to the
> outside and bring outside air from ground level into the downstairs
> to be cooled by the slab and then migrate upwards into the home.
> This might present some condensation issues.

quote:

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>
> Hmm... How about using a swamp cooler (even home made) as a pre-cooler
> and then further cool this cool-damp air using, say, auto radiators
> and the water from your basement slab. Use an air-air heat exchanger
> to cool your indoor air with this damp-cool air so that you're not
> putting humid air inside your house. Vent the now-warm-damp air outside.

quote:

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> Just a thought, I'm sure it can be improved on. Perhaps adding some
> thermal mass outside, like those piles of rocks the one fellow was
> suggesting, that you blow air through at night to 'store' the cooling.

quote:

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> Not "significantly". A slab floor holds an enormous amount of heat. We run
> hot (solar heated) air through ours, and it takes more than a day of
> operation to make what I would consider a "significant" different in
> temperature to the slab.

quote:

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> Vaughn wrote:
>
>
> Not "significantly". A slab floor holds an enormous amount of heat. We run
> hot (solar heated) air through ours, and it takes more than a day of
> operation to make what I would consider a "significant" different in
> temperature to the slab.

quote:

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> In article <3fklo2-ink.ln1@othello.pointerstop.ca>,
> Derek Broughton <news@pointerstop.ca> wrote:
>
>
> Just a note but water actually transfers energy significantly better
> than air does, so you would expect any Air/Slab transfers to take
> considerably longer than Water/Slab transfers of the same energy amount.

quote:

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> Me wrote:
>
[vbcol=seagreen]
> Yeah. That didn't hit me until I read Dave's response...

quote:

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> On Wed, 22 Jun 2005 10:17:03 -0300, Derek Broughton <news@pointerstop.ca>

quote:

---

>
> I wasn't confused until just now. If I can get a temperature
> differential across the radiator by blowing warm air through it, that
> means I'm transferring heat to the water, yes? At that point it becomes
> an exercise of balancing air flow vs. water flow to find the most heat
> transfer possible - which should be "as much flow of each as I can
> manage", I think?

quote:

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>
>

quote:

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> Yes, the greater the mass flow rates through any given heat exchanger,
> the greater the heat flow. Of course, increasing mass flow rate takes
> energy and you quickly reach a point of diminishing returns.

quote:

---

> OK, so I've got hydronic tubing in my basement and kitchen floors, which
> works great for heating those areas in the summer. But, I got to
> thinking - during the summer, the temperature of the slab is _below_ the
> temperature of the air upstairs, and no matter how I pull the forced
> air, the basement is always considerably cooler than the rest of the
> house.
>
> I was wondering if anyone has run a water to air heat exchanger (OK, a
> radiator), similar to an A-coil for A/C, to dump the heat from the air
> into the water (and the slab). Does anyone have any starting points for
> calculations for something like this?

quote:

---

> On Wed, 22 Jun 2005 14:50:06 GMT, Vaughn Simon
> <vaughnsimonHATESSPAM@att.net> wrote:
>
>
> So, do I want to maximize differential, or (guessing) differential times
> flow?
>
> At some point, as flow goes up, will the differential go down so much
> that I'm not just diminishing returns, but getting less transfer?

quote:

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> Dave Hinz wrote:
>
> I've just found this thread, and have been thinking along similar lines.
> However, I wanted to add a water to air heat exchanger mounted inside my
> central air enclosure. Then just run about 55 degree well water through
> the exchanger and out to waste (dry well). Just running the blower, and
> not the AC compressor would save money. Of course the well pump would take
> energy, but it would still be cheaper. Maybe tap the warm waste water as
> pre-heat for hot water.
>

quote:

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> I've just found this thread, and have been thinking along similar lines.
> However, I wanted to add a water to air heat exchanger mounted inside my
> central air enclosure.

quote:

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> Then just run about 55 degree well water through
> the exchanger and out to waste (dry well).

quote:

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> Just running the blower, and
> not the AC compressor would save money. Of course the well pump would
> take energy, but it would still be cheaper. Maybe tap the warm waste
> water as pre-heat for hot water.

quote:

---

>
> "Dave Hinz" <DaveHinz@spamcop.net> wrote in message
> news:3htchdFim2l5U1@individual.net...

quote:

---

[vbcol=seagreen]
> Heat exchanger design/usage is a whole science in and of itself. But here
> are a couple of points:
>
> 1) The metal walls in heat exchangers are *not* the major resistance to heat
> transfer. The metal is a good conductor (duh!), but the laminar layer of
> air/water right next to the metal is not as good.

quote:

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> 2) With that in mind, to get the most heat transfer for a given sized heat
> exchanger, you want to minimize the resistance/thickness of the two laminar
> films (remember, one on each side of the metal wall). The easiest thing to
> do this is increase the local velocity of the air/water. But as you
> suspect, there is a point where a further increase in flow doesn't reduce
> the laminar layer much more at all.

quote:

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> 3) And while the differential pressure needed to move water goes up with
> flow-rate squared, the *power* needed goes up with flow-rate cubed. So
> doubling the flow through the system requires *eight* times the power.

quote:

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> 4) A 'rule-of-thumb' we use in industrial heat-exchangers is to target water
> flow for something like 4 to 7 feet/second flow through the actual
> heat-exchanger tubes. This reduces the laminar layer pretty far, and
> doesn't require too much pumping power. The trick is to figure out just
> what the cross-section of the tube is, and the number of tubes that are in
> parallel.

quote:

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> 5) As one increases the flow through the heat exchanger, the temperature
> rise/drop of the water/air will decrease. This is because although the
> amount of heat transferred *increases*, the mass flowrate increases faster
> (the amount of heat Q=<massflowrate>*<heatcapacity>*(Tin - Tout) ) This
> sometimes confuses folks since the outlet temperature approaches the inlet
> temperature and some people suppose this means that *less* heat is being
> transferred.

quote:

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> 6) Counter-flow arrangement is best, but most practical designs are
> 'cross-flow'. Parallel flow is worst (and easily converted to
> counter-flow).

quote:

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> In conclusion, no you will never increase flow the point where heat transfer
> does *down*. But extreme velocities can cause erosion problems and pumping
> power requirements can be enormous.

quote:

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> On Sat, 25 Jun 2005 14:59:18 GMT, daestrom
> <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:

quote:

---

>
> Ah, hence the wrinkles to provide turbulence...

quote:

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>
>
> But, I think I can do a "Here's how good I can get without spending more
> money than this will save" and get _somewhere_. If I do it right, I
> should be able to add heat with this arrangement in the winter as well
> (outside wood furnace / heat exchanger).
>

quote:

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>
> A car radiator is cross-flow, yes?
>

quote:

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>
> So, here's what I'm thinking. I have the pump pushing at a certain flow
> rate. I have a resistance which is currrently 7 loops of tubing through
> various sections of various floors, which act as resistances in parallel.
> That gives me a flow, after the slabs, of a constant value. I'll
> measure that (easy enough given a bucket and a clock), and compare it to
> the cross sections of my radiators to see if it gets the velocity we're
> after. If we're in-range, bolt the sucker to the cold air inlet, plumb
> it in (add another air filter...) and let the furnace blower suck air
> through it. Temperature delta on the water side will tell me how much
> heat I'm moving, since I know the flow, and temperature delta on the air
> side tells me what good it's really doing.
>

quote:

---

>
> "Dave Hinz" <DaveHinz@spamcop.net> wrote in message
> news:3i7optFjsoj9U1@individual.net...
[vbcol=seagreen]
> The only question here is how much pressure drop the radiators would cause.
> If you take the first flow measurements, then connect up to the radiator and
> measure the flow again out the other side of the radiators, then you have a
> better estimate.

quote:

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> Think of it like a series circuit. If the pump puts out 20 psi, and you get
> X gpm with 20 psid drop across the floor tubing, how much pressure drop
> through the radiators with the same X gpm. Of course if the number is < 1,
> you will get pretty close to X with or without the radiators. But if X gpm
> through the radiators requires 10 psi, then you only have 10 psi left for
> the floor tubing, and so the flow will be <<X. You can measure flow/dP of
> the radiators separately, then solve for the combination by iterating
> several times, or just hook it up and see. (me, I like to do both and see
> how good my math was ;-)