Opel 1900 1973, Руководство по обслуживанию

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1973 OPEL SERVICE MANUAL
DESCRIPTION AND OPERATION
FUNDAMENTAL PRINCIPLES OF REFRIGERATION
We all know what air conditioning does for us, but
very few understand how or why it works. An air
conditioner is functionally very similar to a refrigera-
tor, so let’s take a look at refrigeration. A refrigerator
is a simple mechanism which, surprisingly enough,
works quite a bit like a tea-kettle boiling on a stove.
That may sound far-fetched, but there is more
similarity between the two than most of us would
suspect. In fact, a modern refrigerator can make ice-
cubes and keep food cool and fresh only because a
liquid called the refrigerant boils inside the freezer.
Of everyone knows a boiling tea-kettle is
“hot” and a refrigerator is “cold”. However, this is
where most of us are apt to get confused. We usually
think of “cold” as a definite, positive condition. Ac-
tually though, there is no such thing as “cold”. The
only way we can
it is in a rather negative sort
of way by saying “cold” is simply the lack of
heat
just
as darkness is the lack of light. We make
things cold directly. All we can do is remove some
of the heat they contain and they will become cold
as a result. And that is the main job of any ice-box
or refrigerator. Both are simply devices for removing
heat.
All substances contain some heat. Theoretically, the
lowest temperature that any substance could obtain
is 459 degrees Fahrenheit below Zero. This may be
called “Cold”, and anything warmer than this con-
tains heat. Since man has never succeeded in getting
all the heat out of an object, we must think about the
transfer of heat from one object to another when
talking about controlling temperatures.
Figure Transfer of Heat
Transfer of Heat
The only thing that will attract heat is a colder ob-
ject. water, which always flows down-hill, heat
always flows down a temperature scale from a
warm level down to a colder one. When we hold our
hands out toward the fireplace, heat flows from the
hot fire out to our cold hands (Fig. When we
make
a snowball, heat always flows from our warm
hands to the colder snow. In an ice-box, the ice al-
ways is colder than the stored food, so heat naturally
is drawn out of the warm food
by
the colder ice.
Measurement of Heat
Everyone thinks he knows how heat is measured.
Thermometers are used in most: homes. Whenever
we speak of temperature from now on, we will mean
Fahrenheit. They can tell how hot a substance is, but
they can’t tell us everything about heat.
Figure Applied Temperature Alone is Not the
Sole Measurement of Heat
When we put a tea-kettle on a stove, we expect it to
get
and hotter until it finally boils. All during
the process, we can tell exactly how hot the water is
by means of a thermometer (Fig.
However,
our thermometer will show us that the flame is just
as hot when we first put the tea-kettle on the stove
as it is when the water finally boils. Why doesn’t the
water boil immediately then? Also, why does it take
longer to boil a quart of water than a cupful? Obvi-
ously temperature isn’t the only measurement of
heat.
Even heat is intangible, it can be measured by
quantity as well as intensity. It is recognized that
thermometers indicate only the intensity of heat. The
unit for measuring quantity of heat is specified as
that amount necessary to make 1 pound of water 1
degree warmer (Fig. We call this quantity of
heat a British Thermal Unit. Often it is abbreviated
to Btu.
Perhaps we can get a better idea of these two