GB2143019A - Refrigeration apparatus - Google Patents
Refrigeration apparatus Download PDFInfo
- Publication number
- GB2143019A GB2143019A GB08414033A GB8414033A GB2143019A GB 2143019 A GB2143019 A GB 2143019A GB 08414033 A GB08414033 A GB 08414033A GB 8414033 A GB8414033 A GB 8414033A GB 2143019 A GB2143019 A GB 2143019A
- Authority
- GB
- United Kingdom
- Prior art keywords
- heat rejection
- heat
- screw compressor
- oil
- condenser stage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
- F25B1/047—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of screw type
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
- F25B43/02—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat for separating lubricants from the refrigerant
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Power Engineering (AREA)
- Applications Or Details Of Rotary Compressors (AREA)
Abstract
A refrigeration apparatus comprises a screw compressor 1, an evaporator 6, and an oil separator 3 disposed downstream of a first condenser stage 2 and before a second condenser stage 4. The first condenser stage 2 is provided with a variable rate heat rejection means connected to a control means 9 arranged for varying the heat rejection rate of said heat rejection means in accordance with the screw compressor discharge temperature. <IMAGE>
Description
SPECIFICATION
Refrigeration apparatus
The invention relates to refrigeration apparatus and in particular to improvements in the performance thereof.
The invention is particularly applicable to refrigeration plants incorporating screw compressors which have quantities of oil injected to them in order to improve the efficiency of the sealing against vapour leakage within the compressor. A disadvantage associated with the injection of oil for sealing purposes is that very efficient oil separation methods are required in the discharge of the compressor in order to prevent the carry over of unacceptable quantities of oil into the rest of the refrigeration system where it would impair the efficiency of heat transfer. The refrigerant evaporator is particularly vulnerable to impairment of heat transfer because of unacceptable quantities of oil.
In conventional screw compressor refrigerating systems there is usually provided a large and efficient oil separator in the compressor discharge.
The separated oil is returned to the compressor through an oil coolerwhich may be water cooled or cooled directly by refrigerant. Significant quantities of heat relative to the refrigerating capacity may be removed from the oil at this stage. The amount of heat rejected at this stage in conventional apparatus varies considerably according to fluctuations in ambient temperature. As a result the temperature of the oil returned to the screw compressor varies correspondingly so that the operation of the screw compressor becomes subject to significant fluctuations whereby it becomes necessary to make special provision for injection of variable amounts of liquid refrigerant to smooth these out. Nevertheless a significant loss in the overall efficiency of the system occurs.In other screw compressor designs liquid refrigerant is injected at high pressure into the compressor discharge, thus cooling the oil by direct contact between evaporating refrigerant and hot oil.
This has the disadvantage though of diluting the oil.
It is an object of the present invention to avoid or minimize one or more of the above disadvantages.
The present invention provides a refrigeration apparatus having a screw compressor, an evaporator and an oil separator disposed downstream of a first condenser stage and before a second condenser stage, wherein said first condenser stage is provided with a variable rate heat rejection means connected to a control means arranged for varying the heat rejection rate of said heat rejection means in accordance with the screw compressor discharge temperature.
Further, preferred, details of the invention will appear from the following description of one embodiment of a refrigeration apparatus according to the present invention illustrated with reference to the accompanying schematic drawing.
The apparatus comprises a screw compressor 1 which is followed in the downstream direction of refrigerant fluid circulation by a first condenser stage 2, an oil separator 3, a second condenser stage 4, an expansion valve 5 and an evaporator 6.
Some specific and latent heat is removed from the mixture of oil and refrigerant in the first condenser stage condenser 2. Within this stage, there is considerable condensation of oil vapour on the cold condensating surfaces. The resulting mixture of refrigerant vapour and oil is then passed from the first stage condenser 2 to an oil separator 3 whose efficiency is considerably increased compared to the efficiency of a separator placed immediately downstream of the compressor discharge before the condenser, for various reasons. Firstly the specific volume of the refrigerant oil mixture is considerably reduced due to the lowering of the temperature of the mixture and some condensation of refrigerant.
Secondly, the oil will be more readily separated because a significant proportion of it will have coalesced on the cold surfaces within the first stage condenser. As a result of this the oil separator can be made significantly smaller than one used in conventional refrigeration apparatus in which the separator is placed immediately downstream at the compressor discharge.
The oil collected in the separator 3 is normally returned to the screw compressor 1 through an oil return line 7. Any small quantities of condensed refrigerant which are returned with the oil to the compressor 1 do not effect the pumping capacity of the compressor 1 because they are returned to the compression space after compression has begun.
These small quantities of refrigerant may evaporate within the compressor 1 and the oil to some extent and provide additional cooling to the compressor 1.
The substantially oil-free refrigerant issuing from the oil separator 3 is fed into a second stage condenser 4 where it is substantially condensed to high pressure liquid refrigerant which may then be fed to the evaporator 6through the expansion valve 5 in conventional manner. Within the evaporator 6 the refrigerant extracts heat by vaporisation thereof providing cooling in conventional manner and is then returned to the inlet side of the compressor 1.
In accordance with the present invention the first condenser 2 is provided with an adjustable rate heat rejection means 8 controlled by a control unit 9 provided with a temperature sensor 10 which is arranged for sensing the temperature of the discharge from the screw compressor 1. By this means the temperature of the discharge from the first condenser 2 may be more or less accurately controlied so that the temperature of the oil recovered in the oil separator 3 is in turn controlled whereby the oil is returned to the screw-compressor 1 at or close to the optimum temperature. In a typical system the temperature of the oil injected into the screw compressor 1 would be from 25 to 35"C in order to obtain a screw compressor discharge temperature in the range from 40 to 60"C, the control unit being arranged so that in the event of a higher discharge temperature, the air flow or other heat exchange medium flow is increased to lower the temperature of the oil recovered from the separator and vice versa in the case of a lower discharge temperature.
Claims (6)
1. Arefrigeration apparatus having a screwcom- pressor, an evaporator and an oil separator disposed downstream of a first condenser stage and before a second condenser stage, wherein said first condenser stage is provided with a variable rate heat rejection means connected to a control means arranged for varying the heat rejection rate of said heat rejection means in accordance with the screw compressor discharge temperature.
2. Apparatus as claimed in claim 1 wherein said control means includes a temperature sensor disposed in substantially direct thermal contact with the compressed hot gas discharge from the screw compressor.
3. Apparatus as claimed in claim 1 or claim 2 wherein said variable rate heat rejection means comprises a heat exchanger and variable speed heat exchange medium flow induction means formed and arranged for inducing, in use of the apparatus, a variable speed flow of the heat exchange medium across said heat exchanger.
4. Apparatus as claimed in claim 3 wherein said flow induction means comprises a fan formed and arranged for blowing air across said heat exchanger.
5. Apparatus as claimed in any one of claims 1 to 4 wherein the control unit is arranged so as to maintain the screw compressor discharge temperature substantially in the range from 40 to 60"C, increasing or reducing the heat rejection rate at said variable rate heat rejection means in the case of excursions above or below said range, respectively.
6. A refrigeration apparatus substantially as described hereinbefore with particular reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08414033A GB2143019A (en) | 1983-06-03 | 1984-06-01 | Refrigeration apparatus |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB838315359A GB8315359D0 (en) | 1983-06-03 | 1983-06-03 | Refrigeration apparatus |
| GB08414033A GB2143019A (en) | 1983-06-03 | 1984-06-01 | Refrigeration apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8414033D0 GB8414033D0 (en) | 1984-07-04 |
| GB2143019A true GB2143019A (en) | 1985-01-30 |
Family
ID=26286298
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08414033A Withdrawn GB2143019A (en) | 1983-06-03 | 1984-06-01 | Refrigeration apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2143019A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6250099B1 (en) * | 1998-07-31 | 2001-06-26 | Zexel Corporation | Refrigerating device |
| CN103175338A (en) * | 2011-12-21 | 2013-06-26 | 同方人工环境有限公司 | Hydraulic-filling-type screw rod water-cooling cold water unit with heat recovery function |
-
1984
- 1984-06-01 GB GB08414033A patent/GB2143019A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6250099B1 (en) * | 1998-07-31 | 2001-06-26 | Zexel Corporation | Refrigerating device |
| CN103175338A (en) * | 2011-12-21 | 2013-06-26 | 同方人工环境有限公司 | Hydraulic-filling-type screw rod water-cooling cold water unit with heat recovery function |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8414033D0 (en) | 1984-07-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |