How to temporary chill a car with non-working AC.

|
| A system does not contain "heat". Heat is simply a method of
| transfering energy between the system and it's surroundings.

I thought that *any* material with a temperature above "absolute zero" contains
"heat".

 

| On Fri, 24 Sep 2004, Kathy and Erich Coiner wrote:
|
| > > An air conditioner generates neither heat nor cold. All it does is *move*
| > > heat.
|
| > But it moves the energy at less than 100% efficiency. That means there is
| > some extra work that shows up as heat.
|
| Sure, but the fact remains, an aircon does not "generate" heat or cold.
|
| > You have a closed,well insulated room with a refrigerator in it. It is
| > running and you hold the door open. What happens to the air temp in the
| > room?
|
| Of course the ambient temp increases.
|
| Now here's a fun one: It is common knowledge that there is no such thing
| as a 100 percent efficient machine. Given that, consider an electric space
| heater with a 20-foot electric cord and a high-speed motor-driven blower.
| Is the efficiency of such a device 100 percent, or some lesser figure?
| Support your answer.

No for several reasons:

o Losses in the generation of electricity at the power plant
o Losses due to electrical transmission line losses between the
generator and the heater
o Losses in step-down transformers along the electrical
transmission route.
o Losses at each connection point, switch/fuse/breaker

 

It does naturally generate heat due to the energy lost in moving the
energy in the hot air.

Otherwise it would consume almost zero watts...

 

"No" is not a valid answer; the question is not of the yes/no variety.
Also, we're talking about efficiency at converting the electricity *at the
wall socket* into heat.

 

So are clapped-out '89 Hondas. Perfect match.

 

| On Fri, 24 Sep 2004, James C. Reeves wrote:
|
| > |
| > | On Wed, 22 Sep 2004, Burt Squareman wrote:
| > |
| > | > The A/C system in an `89 old Honda is completely dead.
|
| > | Find and get an automotive swamp cooler. They were popular before car A/C
| > | became common.
|
| > Swamp coolers are relatively ineffective
|
| So are clapped-out '89 Hondas. Perfect match.
|

Good point! ;-)

 

I thought that *any* material with a temperature above "absolute zero"
contains

Except for my ex-wife.

 

If you let the condensate down the drain instead of evaporating inside
the room, you have the most efficient heater.

Bye,
Leon

 

No, the a/c is a heat pump. Think about it as a pump pumping water
between two tanks. It takes energy to pump water up to the higher
tank. The pump is also inefficient.

Bye,
Leon

 

No, a material can not contain heat. Heat, as Threeducks said, applies
only to thermal energy in transit. From Halliday / Resnick: Fundamentals
of Physics, 3rd edition, Wiley 1988:

Page 464: "Heat is energy that flows between a system and its
environment by virtue of a temperature difference that exists between
them"

Page 465: "Both heat and work represents energy-in-transit between a
system and its environment. Heat and work, unlike temperature, pressure
and volume, are not intrinsic properties of a system. They have meaning
only as they describe energy transfers into or out of a system, adding
or subtracting from the system's store of internal energy. (...) It is
without meaning to say: "This system contains 450 J of heat" or "This
system contains 385 J of work""

 

That definition is bullshit. It is wrong.

They should correct their book, if it contains such nonsense.

By that definition, if you heat a rock to 200 F, and then
place it in 200 F water, the rock no longer contains heat energy at
the moment you submerse it, because none will transfer to the water,
which is already at the same temperature. Once you take it out of the
water, now it suddenly contains heat energy again ???? Nonsense.

IE, their definition attempts to define heat energy as a
relative thing, dependant on flow to exist. It is not.

Don't believe everything you read in books

That is bullshit. That is a possible description ( although a
poor one ) of heat flow, not HEAT.

True. At least they got ONE part right.



Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

 

Perhaps you can cite authoritative sources for your definition.
Encyclopedia Britannica agrees with Halliday / Resnick, see
http://www.encyclopediabritannica.com/ebc/article?tocId=9366782&query=heat&ct=
as does Encarta,
http://encarta.msn.com/encyclopedia_761575286/Heat_(physics).html

The rock never *contained* heat, in or out of the water. Heat is defined
as *flow* of thermal energy.

They are defining "heat" not "heat energy".

The book goes on to say (page 465) "In popular usage, "heat" is often
used where "temperature" is intended, as in the cookbook instruction:
"Put in na oven at 300 degrees of heat." We also say that when we add
heat to something it gets "hotter", by which we mean its temperature
increases. When we say: "It's a hot day." we are referring to
temperature and not heat. Do not confuse these totally different
quantities."

 

No, that is heat TRANSER or FLOW.

The rock contains energy imparted to it by a heat source (
there was transfer or flow at the time that happened ), and currently
reflected in the increased molecular movement. That increase in
motion did not slow down when you submerged it in water of the same
temperature. That added energy is still in the rock. That is what I
am referring to as 'heat energy contained in the rock'.

This is true.


Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

 

pjm@see_my_sig_for_address.com wrote:

No, heat is defined as transfer of thermal energy.

Absolutely, it contains thermal energy, it does not contain heat.

Sure, it contains the same amount of thermal energy, it still does not
contain heat.

 

OK, I don't draw a line between the two terms.

Put your hand on it and tell me that It contains LOTS of
heat, just WAITING to meet you

The HEAT was there before you touched it, and some of it will
still be there after your screams of pain die down


Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

 

Nope. Any undergraduate text in thermodynamics will explain it to you.

 

Then they must need to correct every text book on thermodynamics ever
written.

No, that is your misunderstanding of thermodynamics. Heat is one way
energy can be transfered from one object to another. For heat transfer
to exist, you need a finite temperature difference between objects.

The rock never contained "heat" energy. It had an internal energy,
which is based on temperature and its heat capacity.

Yes it is.

It is the correct definition and is the one that has been agreed upon by
the thermodynamics community for approximately 100 years.

 

Sounds like they have some work to do ;-)

I'm too busy to play with the semantics. And that's all it
is.

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

 

And you are wrong. What you are saying is on the order of defining your
own color system and expecting everyone to go along with it.

The transfer of energy through a finite temperature difference is
"heat", but the rock doesn't "contain" heat. It contains a lot of
internal energy, which is related through the heat capacity dU=CvdT.

<snip>

 

Spazzing on about "semantics" is the mark of an idiot caught with his
intellectual pants not only down, but torn and full of poo.

But sure, fine, whatever, I'll play: You're right and the entire rest of
the world is wrong. Here's a cookie. While I've got your omniscient
attention, perhaps you can share with us your correct definitions of
"green" and "wet" and "42"? I've been just slavishly adhering to the
explicitly defined definitions for those terms, just goin' along with the
rest of the world, but I'm sure you have more accurate definitions, so
please elucidate!

DS