SU1122143A1 - Heat-exchanging member - Google Patents

Abstract

HEAT EXCHANGE ELEMENT, containing tubes placed inside, transverse solid fins, characterized in that, in order to increase the critical mass at the dispersed-annular and dispersed modes of flow of heat-transfer fluid or holes, and the area of the holes is 15-76% of the area of the solid edge, and the area of the cavities is 25-76% of the area of the solid edge. -I /

Description

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oo 1 The invention relates to the field of nuclear energy and can be used in steam generators, heat exchangers of nuclear reactors, namely for heat exchange tubular surfaces of fuel elements, steam generators, heat exchangers. The following elements are known: heat insulation elements, inner pipes: the shell of which is equipped with coffer corrugations. The corrugation is internal. The tubular surface creates a turbulence. to the invention is a heat exchange element containing transverse solid fins placed inside the pipe. The turbulization of the flow of heat-transfer fluid caused by these fins leads to the critical power (critical heat flux), and the maximum increase is observed with the frequent arrangement of the ribs. The prototype has a small critical power of the heat exchanger element in the dispersed-ring and dispersed flow regimes of the coolant. flow and microfilm of the liquid on the heat transfer surface, and in the dispersed flow regime there is no film. The aim of the invention is to increase the critical power in the dispersed-annular and dispersed flow regimes. This goal is achieved by the fact that in the heat exchange element containing transverse flat ribs placed inside the pipe, between the solid fins at a distance of not more than one hundred pipe diameters there is an edge with holes or depressions, the area of the holes from 15 to 76% of the area of the solid edge, and the area of the depressions is from 25 to 76% of the area of the solid edge. FIG. 1 shows a longitudinal section of the heat exchange element; in fig. 2 - section A-A of the heat exchanging element equipped with an edge with 3 2 holes; in fig. 3 shows a section A-A of the heat exchange element provided with a ridge with depressions in FIG. 4 is a section BB in FIG. one; in fig. 5-8 - physical characteristics of the heat exchange element. The heat exchange element has the usual solid edge 1 and edge 2, which has holes or cavities. Holes and hollows may have a different configuration. For example, in FIG. Figures 2 and 3 depict ribs with semicircular holes and rectangular depressions. The edge with cavities can be replaced by a set of nuclei applied along the circumference on the surface of the pipe, and the edge is corrugated. FIG. 4 shows a cross section of a heat exchange element with a conventional rib. FIG. Figures 5-6 show the dependences of the critical heat flux q on the dimensionless distance on the diaphragm of the z / d caliber (z is the distance from the diffraction, d is the channel diameter). FIG. Figure 7 shows the dependence of the critical heat flux at a distance of 50 calibers on the diaphragm. From the relative size of the area of the FoTfe holes 100% (, is the area of the holes, Fpgj is the rib area). This figure also shows the pressure drop across the diaphragm. FIG. Figure 8 shows the dependences of the heat flux (in the presence of a liquid film in front of the diaphragm) on the dimensionless distance from the diaphragm. Figures 3-15 in FIG. 5-8 indicate the characteristics for the following conditions: smooth pipe 3 (diaphragm with internal diameter equal to the diameter of smooth pipe d); common edge 4 simulated by diffraction; regular edge 5, simulated by a split washer; ribs with holes (6 - 0.3, 7 - & 0.5-10 m); two conventional ribs 8 located 25–10 m apart from each other, 9–11 — a combination of a rib with holes and a conventional rib (9–0.3; W –5 0.5; 11 O, 7510 m) ; 12, 13 - an edge with hollows (12th 1j13-P 240); 14, 15 — edge combination with trough3

mi and ordinary ribs (14 - P 2j 15 - E 2.5-10 m).

The element works as follows. A coolant with specified input parameters is supplied to the entrance to the heat exchange element. The direction of flow of the coolant is shown in FIG. 1 arrow. Depending on the amount of heat flow supplied, the coolant may have different steam content at the element outlet.

FIG. 5-6, the installation of a conventional solid rib leads to an increase in the critical heat flux compared to a smooth pipe, and with increasing number of ribs, the efficiency increases. The presence of holes or cavities in the rib reduces its efficiency, but a combination of a rib with valleys or holes and a conventional solid rib can increase the increase in critical heat flux compared to the increase in critical heat flux Caused by the total turbulizing effect of two ordinary solid edges.

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Based on the data shown in FIG. 5, 6, 7, to conclude that the increase in the critical heat of the flow occurs when the area from the holes from 15 to 76 of the area of a solid edge or the area of depressions from 25 to 76% of the area of a continuous edge, and the flow disturbance produced turbulizer tangibly

10 at a distance of not more than one hundred pipe diameters, i.e. an increase in the critical quantity (critical heat flux) is possible only in the specified interval. Thus, the installation of turbulizers at a distance of more than 100 pipe diameters does not lead to a positive effect (1). In the presence of a liquid film in front of the diaphragm (the thermal current of 20 in the input area is less than the critical one), the noted effect disappears (see Fig. 8). The proposed heat exchange element in the field of dispersed-ring and dispersed

The 25 flow regimes of the coolant significantly increase the critical power (critical heat flux) with the same operating parameters.

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Claims (1)

HEAT EXCHANGE ELEMENT containing internally placed pipes continuous river ribs, characterized in that, in order to increase the critical power in the dispersion-annular and dispersed flow regimes of the coolant, between the solid ribs at a distance from them no more than a hundred pipe diameters, an edge with holes or hollows is installed, and the hole area is 15-76 % of the area of a solid rib, and the area of the depressions is 25-76% of the area of a solid rib. ί 11