US3012413A

US3012413A - Refrigeration systems

Info

Publication number: US3012413A
Application number: US789014A
Authority: US
Inventors: Anderson Norman
Original assignee: Sir George Godfrey and Partners Holdings Ltd
Current assignee: Sir George Godfrey and Partners Holdings Ltd
Priority date: 1958-01-25
Filing date: 1959-01-26
Publication date: 1961-12-12
Anticipated expiration: 1978-12-12
Also published as: ES246785A1; DE1102186B; GB915124A

Description

Dec. 12, 1961 N. ANDERSON REFRIGERATION SYSTEMS Filed Jan. 26, 1959 FIG. 2.

INVENTOR A a/(MAN 4/vokso/v ATTO R N EY United States Patcffif 3,012,413 REFRIGERATION SYSTEMS Norman Anderson, Hanworth, England, assignor to Sir George Godfrey & Partners (Holdings) Limited, Hanworth, England 7 Filed Jan. 26, 1959, Ser. No. 789,014 Claims priority, application Great Britain Jan. 25, '1958 2 Claims. (Cl. 62-272) This invention relates to refrigeration systems and is 0 more particularly, though not exclusively, concerned with systems operating on the air-cycle principle as used, for example, for cooling the cabins of aircraft. The object of the invention is to provide means to overcome the difliculties caused by ice formation in refrigeration systems generally and which may have particularly serious effects in the case of airborne systems supplying cooled air to aircraft cabins, and also systems in which such difliculties are substantially overcome.

In air-cycle refrigeration systems of the type used for cooling aircraft cabins pressure air for supply to the cabin is expanded across the turbine of arr air-cycle refrigerator, consisting of a turbine driving acompressor or fan mount-j ed on a common shaft with the turbineyto do work ant? thereby loseheat, such pressure air. eitherrpassingdirectly 25 through t'h'e'tu'rbinejwith the compressor or fan'operating in free air merely .t'i'constitute an atmospheric brake or servinglto draw air across an air-.to-air .heat exchanger through which the'pressure air passes on its way to the turbine, or passing first through the compressor and then through a heat exchanger before being expanded across the turbine with further loss of heat.

Systems of the foregoing type usually have a water extractor inserted in the air duct near the downstream end of the system so that Water is removed immediately before the air enters the cabin, and the main difliculty which has been experienced under icing conditions is blockage of the water extractor which seriously impedes the air flow to the cabin and gives rise to high pressures in the duct. The trouble originates with frost formation in the water extractor but in addition, when thawing takes place, slush which has collected in the duct upstream of the water extractor is blown into the latter causing even more severe blockage.

According to the invention means for overcoming these difliculties take the form of an ice guard adapted for connection in a duct of a refrigeration system circuit and comprising a foraminous element of such small hole size that the least frost deposit thereon causes considerable blockage of the duct and builds up a pressure therein to compress the refrigerant to produce self heating of the refrigerant and so maintain a delivery temperature above the freezing point of water, the total area of the element being so chosen that an acceptable pressure drop across the element is obtained when the element is free of frost deposit.

The invention also includes a refrigeration system wherein there is connected in circuit a foraminous element having the above characteristics.

The foraminous element provides a simple and effective ice guard and it preferably comprises a metal gauze of very fine mesh in order to ensure that the smallest degree of frost deposit thereon causes blockage. If desired the gauze may be backed with a perforated plate in order to give it the required mechanical strength to resist rupture under the high pressure drop which obtains during frosting.

When applied to an air-cycle refrigeration system the foraminous element is preferably placed immediately downstream of the turbine of the aircycle refrigerator in order to limit the length of air duct at high pressure and to avoid effects due to heat transfer into the ducting.

The invention will now be further described with refer; ence to the accompanying drawings which illustrate, by way of example, one way of carrying the invention into eftectin connection with an airborne air-cycle refrigeration system for supplying cooled air to an aircraft cabin, and in which FIGURE 1 is a diagrammatic flow diagram of the system, and

FIGURE 2 is a cross-sectional view of an ice guard of the system according to the invention.

In the circuit of FIGURE 1 charge air for pressurizing and ventilating the cabin is obtained from a tapping 1 of the compressor of a gas turbine engine of the aircraft. Air from this tapping passes along a duct 2 through an air-toair primary heat exchanger 3 which reduces its temperature, and thence through a duct 4 to a valve 5. As the temperature of the charge air leaving the primary heat exchanger 3 is usually still too high it is brought to an acceptable level by expanding the air across the turbine of a cold air unit 6 in the form of a turbo-compressor.

The turbo-compressor has an inward-flow radial turbine 7 driving a centrifugal compressor 8 on a common shaft. Charge air passesfrom the valve 5 through the compressor 8, through a duct 9 to a secondary air-to-air heat exchanger 10, through. a duct 11 to the turbine 7 across which it is expanded and into a cabin supply duct12. During passage of the charge air through the turbo-compressor it is compressed and heated by the compressor 8, heat then being removed in the secondary heat exchanger 10 after which it is expanded across the turbine 7 which drives the compressor 8 and consequently removes energy from the charge air to cool the latter.

An ice guard 13 is located in the supply duct 12 immediately downstream of the turbine 7 between the latter and a water extractor 14 inserted in the duct 12 before its entry into the aircraft cabin, the cabin wall being shown diagrammatically at 15. A non-return valve 16 is located in the duct 12 immediately before its entry into the cabin.

Referring more particularly to FIGURE 2, the ice guard 13 comprises a tubular body 17 of double-conical form having coaxial inlet and outlet connections, 18 and 19 respectively, by means of which it is connected into the supply duct 12. The double-conical form of the body 17 results from the assembly together of inlet and outlet body portions, 20 and 21 respectively, each of outwardly flared form and radially flanged at their wider ends 20a and 21a so that when connected by means of a ring of bolts such as 22 pasing through the mating flanges an airtight assembly results.

To ensure the foregoing airtight assembly, the flange 20a on the inlet portion 20 of the body is turned axially at its radially outer edge 20b in order to embrace the thicker radial flange 21a of the outlet portion 21. The periphery of the flange 21a is grooved to receive a sealing ring 23 which seals against the inner surface of the axially turned portion 20b of the inlet body portion 20. Sandwiched between the radial faces of the flanges 20a and 21a is a foraminous element 24 comprising a metallic gauze of a very fine mesh, or a plurality of such metallic gauzes superimposed one upon the other. At the outlet or delivery side of the gauze or gauzes a perforated metal backing plate 25 is arranged, such plate also being sandwiched at its periphery between the flanges 29a and 21a.

The foraminous element 24 constitutes a simple and effective ice guard, its hole size being such that the least frost deposit thereon causes considerable blockage of the duct 12 and builds up a pressure therein, such pressure rise compressing the air to produce self heating of the charge air upstream of the ice guard 13 to maintain a delivery temperature above the freezing point of water.

Patented Dec. 12, 1961 The total area of the foraminous element 24 is so chosen that an acceptable pressure drop across the element is obtained when the latter is free of frost deposit.

The water extractor 14 removes water present in the charge air after leaving the ice guard 13, and due to the latter it has been found in practice that the charge an entering the water extractor 14 contains only water and not slush or ice. For his reason the water extractor 14 need not embody the usual relief valve, as a result of which it can be-made of more simple and efficient design.

For heating purposes air is taken from the tapping 1 along a duct 26, through the valve 5, a flow controller 27 and a duct 28 which feeds into the supply duct 12'immediately upstream of the Water extractor 14. For full cooling the only charge air entering the supply duct 12 passed through the heat exchanger 3, valve 5 and turbo-compressor 6, whereas for full heating all this charge air passes through the valve 5 and flow controller 27. A Thus the valve 5 acts, in efiect, as a mixing valve and its S'ZttlHg dGiEI- mines the degree of cooling and/or heating of the total charge air entering the cabin.

The main flow of the cooled air is limited by the r102 zles of the turbine 7, and the flow controller 27 controls the subsidiary flow of hot air in dependence upon the supply pressure to the cabin. 7

When the aircraft isfly'ing, cooling air for the primary and secondary heat exchanges 3 and 10 is obtained by ram efieet, but when the system is used on the ground it necessary to induce a flow of cooling air isobtained by opening normally closed valves 29 Opening these valves supplies air under pressure from the tapping 1 to galleries 30 associated respectively with the heat exchanges 3 and 10, and the pressure air is ejected from these galleries to provide a jet pump efiect' which induces a flow of cooling air over' the heat exchangers.

1. A ventilating system having means for supplying comparatively warm air and incorporating a refrigeration system having a circuit including a turbo-compressor unit comprising a turbine and a compressor, a heat exchanger arranged in the circuit between said turbine and said compressor; an ice guard arranged in the circuit downstream of said compressor and comprising in combination a foraminous element of such small hole size that frost deposit thereon causes considerable blockage of the duct resulting in a pressure rise therein which compresses the refrigerant upstream of the element to produce self-heating of the refrigerant and maintain a delivery temperature in the duct above the freezing point of water, two generally f'rustoconical body portion arranged with their wider ends adjacent each other and provided with substantially coaxial inlet and outlet connectionsat their narrower ends, and a perforated plate, which backs said element and with said plate is sandwiched between said wider ends of the body portions; said circuit of the refrigeration system also including a water extractor upstream of which said ice guard is placed and means for mixing refrigerated air with said comparatively warm air at a point in the circuit between said element and said water extractor.

2. A ventilating'syster'n according to claim 1 wherein said foraminous elenlent comprises a fiat sheet of metal gauze of very fine mesh.

References- Cited indie file or this atent