CA1046784A

CA1046784A - Compressor refrigeration plant

Info

Publication number: CA1046784A
Application number: CA265,124A
Authority: CA
Inventors: Bent Karll
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1975-11-28
Filing date: 1976-11-08
Publication date: 1979-01-23
Also published as: GB1562627A; FR2333209A1

Abstract

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.

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.

Claims

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.