GROUPE COMPRESSEUR DE REFRIGERATION

COMPRESSOR REFRIGERATION PLANT

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
The present invention relates to a compressor refrigera-
tion plant comprising a throttling device between the condenser
and evaporator and, associated with the throttling device, an
intermittently operable electric heating resistor, a chamber
being disposed upstream of at least a part of the throttling
device and the electric heating resistor being a PTC resistor
which is arranged in the chamber and which, when a temperature
range between the evaporating temperature of the refrigerant
associated with the pressure in the chamber and the coking
temperature of the refrigerant oil is exceeded, goes over from
a low to a high resistance.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A compressor refrigeration plant comprising a
throttling device between the condenser and evaporator and,
associated with the throttling device, an intermittently operable
electric heating resistor, a chamber being disposed upstream of
at least a part of the throttling device and the electric heating
resistor being a PTC resistor which is arranged in the chamber
ant which, when a temperature range between the evaporating
temperature of the refrigerant associated wtih the pressure in
the chamber and the coking temperature of the refrigerant oil is
exceeded, goes over from a low to a high resistance, characterized
in that the part of the throttling device downstream of the
chamber is formed by an axially short throttling element such
as a fixed nozzle or diaphragm.
2. A compressor refrigeration plant according to
claim 1, characterized in that a part of the throttling device
upstream of the chamber is also formed by an axially short
throttling element such as a fixed nozzle or diaphragm.

Description

~)46~4
The present invention relates to a compressor refrigera-
tion plant comprising a throttllng dev~ce between the condenser
and evaporator ~nd, a~sociated with the throttling device, an
intermittently operable electric heating resistor, a chamber
being disposed upstream of at least a part of the throttling
device and the electric heating resis~or being a PTC resistor
which is arranged in the chamber and which5 when a temperature
range between the evaporating temperature of the refrigerant
associated with the pressure in the chamber and the coking
temperature of the refrigerant oil is exceeded, goes over from
a low to a high re~istance.
In the parent patent, the parts of the throttling
device consist of capillary tube sections. If, under the same
pressure conditions, one passes a liquid refrigerant through one
cspillary tube section and a refrlgerant vapour to the other,
the mass of liquid pas~ing through per unit time is substantially
three or four times larger than that of the vapour. This already
produces a very good blocking effect which can for example be
utllized for defrosting.
According to the invention, the consumption of vapour
can be redured still further if the part of the throttling device
downstream of the chamber is formed by an axially short throttling
element such as a fixed nozzle or diaphragm.
With such short throttling slements, the mass of liquid
passing through per unit time is six to eight times larger than
that of the vapour. Under otherwise identical conditions, there-
fore, only half the amount of vapour passes through such a
throttling element as compared with a capillary ~ube section that
i9 equivalen~ly deslgned with respect to the liquid. Consequently,

l~J46784
an even better blocking effect is obtalned, as a result of which
le8s vapour flows off to the evapora~or. Less vapour means less
energy, not only with respect to the evaporation by means of the
PTC re~istor but also for the required subsequent condensation.
If part of the throttling device is also disposed up-
stream of the chamber, whlch is not absolutely necessary, this
may optionally be a capillary tube section or likewise an axially
short throttling element such as a fixed nozzle or diagphram.
The latter is recommendable for the purpose of a uniform construc-
tion.
An example of the invention is diagrammaticallyillustrated in the drawing. It is the circuit diagram for a
compressor refrigeration plant.
In lts cycle, the circuit comprises a compressor 1,
a condenser 2 and an evaporator 3. The latter is accommodated
in a refrigerated space 4. Its temperature is monitored by a
thermostat 5 which switches the compressor 1 on and off when
required. Between the condenser 2 and evaporator 3 there i9 a
throttling device 6 consisting of a fixed nozzle 7, a chamber 8
and a down~tream diaphragm 9. The fixed nozzle 7 and the diaphram
9 are dimensioned with respect to their throttling resistance
80 that the liquid refrigerant from the condenser 2 and under
the pressure of the condenser reaches the evaporator 3 in an
expanded amount designed for normal operation and there evaporates
by absorbing heat.
In the chamber 8 there is a heating resistor in the
form of a PTC resistor 10 which can be applied to main terminals
12 by a switch 11. The switch 11 is actuated by a time-clock 13
whlch lnitlates a defrosting period of, for example, one hour
'~3

`` 16346784
at predetermined time intervals, e.g. every 72 hours. By means
of the PTC resistor, the refrigerant in the chamber 8 is heated
80 that it evaporates without any coking taking place.
The vapour has a considerably larger volume. Under
ldentical pressure conditions, the mass of refrigerant flowing
out of the chamber 8 per unit time is six to eight times smaller
than during normal operation. The desired blocking effect is
consequently obtained and this is greater than when using a
capillary tube section. The vapour is sufficiently hot to melt
the frost on the evaporator 3.