[ExI] paradox?

[spike]

From: extropy-chat [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of William Flynn Wallace
Sent: Tuesday, March 22, 2016 8:33 AM
To: ExI chat list <extropy-chat at lists.extropy.org>
Subject: [ExI] paradox?

 

In the winter we set the thermostat during the day at 71 and that's about our feel good temperature.  72 feels just a bit high and 70 a bit low.  I am a bit surprised that we can tell the temp of just a degree or two.  Night setting is 68….No change is made according to outside temp.  There is a factor that is probably irrelevant:  persistence of cold.  When we come in from the cold our feeling of coldness lasts much longer than it takes to warm our skin.  Not understood.  There is no persistence of warmth…If we wanted the difference to be the smallest, we'd set it just like we do now. But maybe the difference is not a controlling factor here….However, I don't know what is.  Any of you notice the difference in settings between summer and winter, and if, so, is it like ours or different????bill w

 

 

BillW, this took me years to figure out, even though I had all the requisite formal training, with the math and all.

 

The answer to your paradox is in that there is more to HVAC than the air temperature and humidity.  Those are the ones we think about immediately, but if you try to create a mathematical model it turns out to be crazy complicated.  Consider factors such as you wear more clothing in the winter.  That one is difficult to equalize, but it is still more complicated.

 

Your comfort is not only a factor of convection from the surrounding air, but also conduction into the furniture you touch and radiation from the walls.  A room measured at 70F by your thermostat on a blustery winter day and the same room measured at 70F by your thermostat on a sultry Mississippi July afternoon.  In that same room, the air is stirring in July because the AC is running full blast, so you get more evaporative cooling from the air.  The furniture is colder in that room in January because it radiates heat into the cold walls.

 

To show what I am saying, get one of those IR temperature devices.  Set the room to 70F in January, measure the inside wall temp.  Probably get about 60F.  Repeat experiment in July, probably get about 80F.  Your walls are radiating heat to your furniture and stuff you touch a lot more in July than in January.

 

But wait, there’s more.  It also depends on what kind of heat you have.  Some go for reversible heat pumps.  This warms the air, but it also stirs the air, so it doesn’t feel as good as a crackling fireplace, which radiates heat (aaah so comforting it is.)  If you have ever been to a big jolly bonfire or at the scene of a house fire where something is burning really hot, you can feel that heat from waaaay far away: radiation.  I have felt the heat from a forest fire from a quarter of a mile away.  Imagine being inside a house where it is cold goddam hell outside.  Your paradox is sorta the flip side of that coin: the wall temperature counts.  If you are in a reeeeally cold place like Spokane, it counts a lot.

 

Once I really put my head to this, it caused me to realize why I was always so cold in Spokane Washington at Christmas even though the thermostat read the same as mine at home: the walls were a lot colder there.  I was radiating heat into them and getting very little back.  Once you really start drilling way down on this paradox and doing the math, you realize why I concluded that an MBrain would need to reflect most of its energy in a low-entropy form (so it mostly isn’t used to do computation.)  Otherwise the inboard nodes overheat.  Alternative: they need to be waaaay out there.  So by my calcs, an MBrain must either be huge or wasteful, and I fear both.  I found that by wondering why it is so cold indoors in Spokane Washington, even when the thermostat is telling me I should be comfortable.

 

Thanks for the reminder BillW.  See what cool stuff you can discover by pondering HVAC paradoxes?

 

spike

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