I.Lewis on fri 15 oct 99
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To: Subscribers Clayart clayart=40lsv.uky.edu
From: Ivor Lewis. iandol=40pirie.mtx.net.au
Heat and temperature
Perhaps I may be mistaken, but from time to time it seems from reading =
postings
that there may be some confusion as to the meanings of Heat and Temperature.=
My
own opinion is that use of Pyrometric Cones may have something to do with =
this,
partly because each cone value is given a several temperature ratings. I =
believe
these are related to the rate at which temperature rises.
Delving into scientific books or reading dictionary definitions is not =
entirely
helpful in clearing up this confusion.
The simplest way I can put it is to say that Temperature is about the =
intensity
or lack of it. It is about the degree of hotness or coldness of an object or
anything else. Temperature is measured on convenient scales. You cannot buy =
or
sell a temperature.
Heat is a form of kinetic energy, energy on the move, which is measured as a
quantity. We measure it in British Thermal Units, Joules, Calories. This is =
the
calorific value of our fuels. Measuring those values is an involved =
laboratory
process. It is natural for heat to move from places where there is a high
intensity to places where there is a low intensity. You can buy or sell a
substance with a calorific value.
So, when we discuss cone values, we should remember about the intensity of =
our
heating and the quantity of heat we are supplying. Playing with the position=
of
the gas cock or throwing more wood on the fire changes the rate at which we
supply the quantity. Playing with the dampers, increasing and decreasing the
draught changes intensity because the amount of oxygen supplied affects the
efficiency with which fuel burns. Low efficiency means lower flame =
temperature
or slower rates of fuel consumption.
I did have a look at some values for flame temperatures. Neutral =
Oxy-Acetylene
flames are about 2500deg C-=7E4500F. Oxy- Hydrogen is lower. Oxy- Propane =
about
2400degC-=7E4300F. Replace Oxygen with air and the temperature falls =
dramatically.
Displace the air with steam and the fire goes out.
Regards to all, with apologies to the knowledgeable
Ivor.
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