Refrigeration – Automatic control – Refrigeration producer
Patent
1990-11-27
1991-11-12
Wayner, William E.
Refrigeration
Automatic control
Refrigeration producer
62510, 4182012, F01C 116
Patent
active
050637509
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a rotary positive displacement compressor comprising at least one rotor forming compression chambers in a working space, the compressor having an inlet port communicating with a low pressure channel, an outlet port communicating with a high pressure channel, intermediate port means communicating with an intermediate pressure channel and bleed port means selectively connectable to said low pressure channel through a return channel, said intermediate port means and said bleed port means being located such that they face a compression chamber within said working space in a compression chamber, which chamber is sealed from communication with said inlet port as well as said outlet port by said at least one rotor.
The invention further relates to a plant of refrigeration type comprising such a compressor and having a condenser communicating with said high pressure channel, an evaporator communicating with said low pressure channel, a vessel for an intermediate pressure communicating with said intermediate pressure channel, a channel connecting said condenser to said vessel, said channel having first pressure reducing means for decreasing the high pressure in said condenser to the intermediate pressure in said vessel and a channel connecting said vessel to said evaporator, said channel having second pressure reducing means decreasing the intermediate pressure in said vessel to the low pressure in said evaporator.
A compressor and a plant of such types are earlier known from U.S. Pat. No. 3,913,346. The intermediate pressure zone in such plants is used for internal cooling purposes within the plant at a temperature level above that of the evaporator. The main cooling purpose is to precool the liquified refrigerant before the supply thereof to the evaporator which results in a more effective use of the evaporator area so that the dimensions thereof can be minimized for a certain capacity simultaneously as the swept volume of the compressor and thus its dimensions can be reduced correspondingly. Furthermore the power required for recompression of the gaseous refrigerant supplied at the intermediate pressure will be less than that if all the refrigerant were supplied at the evaporator pressure.
In order to vary the volumetric capacity the compressor in U.S. Pat. No. 3,913,346 is provided with a selectively adjustable valve controlling a bleed port in the wall of the working space so that a certain amount of the working fluid supplied to the compressor may be returned to the inlet channel of the compressor. This bleed port is disposed within the same phase of the compression cycle as the intermediate port means. When the bleed port is opened the pressure level inside the compressor working space decreases to such an extent that the back pressure within the area of the intermediate port means will be practically the same as that in the low pressure channel. The bleed port must in order to avoid throttling losses be provided with a large area corresponding to what is required not only for the recirculation of the surplus fluid supplied through the inlet port but also for draining the fluid supplied through the intermediate port means. The size of the valve member will thus be too large for location in the end wall with regard to its area compared with the limited space available outside the rotor bearings. For this reason the valve has to be located in the barrel wall of the working space. Such a valve will consequently be complicated in shape and expensive to manufacture as it not only has to sealingly cooperate with its seat in the housing but also has to sealingly cooperate with the confronting rotor or rotors in order to avoid internal leakage within the compressor, especially when running under maximum capacity conditions.
In the PCT-application with International Publication Number W086/06798 a compressor is disclosed, where the discussed problems related to a compressor and a refrigeration plant of the type in question are overcome by providing a conne
REFERENCES:
patent: 3568466 (1971-03-01), Brandin et al.
patent: 3913346 (1975-10-01), Moody, Jr. et al.
patent: 4727725 (1988-03-01), Nagata et al.
patent: 4748831 (1988-06-01), Shaw
patent: 4799865 (1989-01-01), Oscarsson
Svenska Rotor Maskiner AB
Wayner William E.
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