The heat exchanger

 

(57) Abstract:

The invention is intended for use for gasification cryogenic fuel in aircraft gas turbine engines. The heat exchanger contains are parallel to one another tube connected with the inlet and outlet manifolds and placed in the shell, which forms a cavity with inlet and outlet for flow of the heat carrier, and according to the invention the heat exchanger is mainly used for the gasification of cryogenic fluid flowing within the tubes, and the tubes are located one after the other with a step S and have an outside diameter of dnin addition, tubes are installed in groups step between groups S1determined from the ratio of 1.5 S1/dna 2.5 with a step S, determined from the ratio of 1.5>S/dn1,1. The invention improves the efficiency of the heat exchanger, reduces the external resistance and keeps it from freezing from the coolant. 1 C.p. f-crystals, 3 ill.

The invention relates to the field of heat exchangers and is intended primarily for gasification cryogenic fuel in aircraft gas turbine engines (AHTD). In AGTD working on cryogenic fuel required is CLASS="ptx2">

A known heat exchanger - gasifier fuel AHTD installed at the entrance of the compressor (GB N 1022952, CL F 4 S, publ. 1966). The disadvantage of this heat exchanger is its low reliability due to possible freezing of the tubes of the heat exchanger. The engine of this heat exchanger is almost unusable at low flight speeds, when the air temperature at the inlet is close to the ambient temperature. The heat exchanger in this case is inefficient because of its freezing.

The location of the heat exchanger at the inlet to the compressor also reduces the reliability of the engine due to the probability of seal failure in flight. In this case, the path AHTD formed an explosive fuel-air mixture, such as "explosive gas" hydrogen fuel.

This disadvantage is eliminated in the heat exchanger in the form of a tubular coil that is installed in the exhaust stream (US N 1799249, CL 165-60, publ. 1974 ). The disadvantage of this heat exchanger is freezing the surface of the tube-side fluid, containing water vapor, due to the high heat transfer from the cryogenic environment and its low temperature.

From theory of heat transfer is known that the higher the ratio talek possible formation of a solid phase (ice, frost) due to condensation and freezing of water vapor contained in the coolant.

Large speed cryogenic environment in the series connected coils of the coil induce a higher heat transfer coefficient and, consequently, the formation of ice.

These disadvantages of these heat exchangers is fixed in the heat exchanger containing spaced parallel to one another tube connected with the inlet and outlet manifolds and placed in the shell, which forms a cavity with inlet and outlet for flow of the heat carrier (SU 434251 A, F 28 D 7/16, 30.10.1974).

The disadvantage of this heat transfer is increased hydraulic losses in the flow of coolant flow over the heat exchanger from the outside. The above solution is the closest analogue of the invention.

It is known that losses in the external flow, flowing consistently located tube, increase with increasing spacing between the tubes S to a value of more than 1.5 of its diameter dH, i.e., the ratio S/dHmust be < 1,5 (see I. E. Idelchik. Handbook of hydraulic resistance. M: mechanical engineering, 1975, page 397, and A. M. Krapivin and other Hydraulic resistance of a homogeneous tubes of the Oia and resistance, as a consequence, increase efficiency, if the heat exchanger is located in the path of AHTD, it is necessary to perform heat exchangers with a compact arrangement of tubes, with S/dH1,5.

However, when a large number of tubes in a bundle over along the beam becomes similar to the flow along a rough plate and on the surface of the beam is formed thick cooled layer of fluid, which due to its thermal resistance reduces the efficiency of heat exchange between the coolant and the cryogenic fluid. In "Calculation and experimental investigation of hydraulic and heat transfer in tube bundles, streamlined unlimited flow" (of Those. the report CIAM N 30208/3, 1989) shows that reducing the number of tubes in a bundle from 11 to 6 of the Nusselt number (Nu), describing the heat transfer from the outer side of the beam increases by approximately 2 times. The probability of freezing shesticlennogo beam is virtually eliminated due to its very high efficiency.

The problem to which the invention is directed, is to create a highly efficient heat exchanger on all modes, with a small external resistance and lack of freezing tubes from Talana task is solved by the heat exchanger contains are parallel to one another tube connected input and output manifolds and placed in the shell, which forms a cavity with inlet and outlet for flow of the heat carrier, and according to the invention the heat exchanger is mainly used for the gasification of cryogenic fluid flowing within the tubes, and the tubes are located one after the other with a step S and have an outside diameter of dHin addition, tubes are installed in groups step between groups S1determined from the ratio of 1.5 S1/dH2,5.

In addition, the tubes in groups installed in increments of S, determined from the ratio of 1.5 > S/dH1,1.

The calculations are confirmed by experimental data showed that the heat transfer (criterion Nu) 20 of the tube bundle, consisting of four groups of five tubes in each group with a relative spacing between groups S1/dH= 2,33 and the relative spacing between tubes in the groups S/dH= 1,17, 2 times more heat 20 of the tube bundle, made in the usual way with a step between the pipes S/dH= 1,17.

The present invention is represented by the drawings, where

in Fig. 1 shows a General view of the heat exchange is piping set and step between them.

The heat exchanger consists of a shell 1 with an internal cavity 2 for flow of fluid from the inlet 3 and outlet 4. In the cavity 2 is the inlet manifold 5 with a cavity 6 to enter the cryogenic fluid and an outlet manifold 7 with a cavity 8 for the outlet of the cryogenic fluid. The inlet 5 and outlet 7 collectors connected in parallel spaced rows of tubes 9 with an outer diameter of dHlocated one after the other in increments of S. Tubes 9 are arranged in separate groups in increments of S1between the groups.

The inlet manifold 5 is provided with a nozzle 10 for supplying a cryogenic liquid 11 and the outlet manifold 7 is supplied by a pipe 12 to exit the heated cryogenic fluid 13. The input 3 of the cavity 2 is designed to supply hot fluid 14 (for example, products of combustion after the turbine GTE), and the output of the 4 - for chilled coolant 15.

In Fig. 3 shows that the heat transfer (criterion Nu) increases with decreasing number of tubes nTrin the beam, reaching a maximum value at nTr= 3. For example, if , when nTr= 10 Nu = 300, and nTr= 5 Nu = 500, i.e., heat dissipation is increased in 1.7 times.

The heat exchanger works as follows.

Cryogenic fuel 11 in the liquid sustaina with the coolant 14 gasified, and in the gaseous state is supplied into the cavity 8 of the output manifold 7 through the pipe 12 in the direction of arrow 13 is sent to the consumer, for example the combustion chamber. On the last tube of each group breaks formed the boundary layer of the coolant, resulting in the efficiency of the heat exchanger increases, prevents its freezing from the outside and reduces the hydraulic resistance.

1. A heat exchanger containing spaced parallel to one another tube connected with the inlet and outlet manifolds and placed in the shell, which forms a cavity with inlet and outlet for flow of fluid, wherein the heat exchanger is mainly used for the gasification of cryogenic fluid flowing within the tubes, and the tubes are located one after the other with a step S and have an outside diameter of dnin addition, tubes are installed in groups step between groups S1determined from the ratio of 1.5 S1/dn2,5.

2. The heat exchanger under item 1, characterized in that the tubes in groups installed in increments of S, determined from the ratio of 1.5>S/dn1,1.

 

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