Air-cooled surface condenser

This First Page has been artificially created and is not part of the CIPO Official Publication

This invention relates to a surface condenser, which is cooled by a positively moved current of air and the condenser elements of which, disposed in double rows, form in crosssection an approximately equilateral triangle the apex of which is directed in the downward direction and at the base of which is provided a covering which connects the upper ends of the condenser elements and which is equipped with screw fans disposed at intervals from one another In the longitudinal direction of the double row and which have a suction action. The condenser elements disposed in an arrangement whereby they are inclined in the form of a V in relation to one another are in these circumstances connected by their mutually remote ends to steam distributor conduits extending in the longitudinal direction of the double while the mutually facing ends of the condenser elements are connected to condensate collector conduits extending In the same direction. The condenser elements have in each case a relatively large number of condenser tubes, which are preferably equipped with outer fins and which are connected in a parallel arrangement to a common steam distributor chamber and a common condensate collector chamber. The outer surfaces of the condensate tubes, which are usually disposed successively In a plurality of rows, are In this case subject to the action of a current of cooling air which Is drawn in from the atmosphere by the screw fans provided above the condenser elements. In these circumstances, two or four or even more rows of condenser tubes are disposed one after the other in the direction of flow of the cooling air and as a rule they are constructed as finned tubes having an elliptical cross-section. The

<img file="CA677166A_D0001.tif" />

number of condenser elements connected together to form a double row can be varied within wide limits, while In addition two or more double rows can be provided side by side in an approximately parallel arrangement.

In comparison with the usual roof-shaped arrangement, the aforesaid V-shaped arrangement of the condenser elements has the advantage of a considerably smaller overall height, since in contrast to the roof-shaped arrangement the intake apertures for the cooling air and the condenser elements are disposed in the same region as regards height. The reduction of the overall height results in a considerable saving of weight, so that the foundation and the supports can be made considerably lighter. The covering connecting the upper ends of the condenser elements protects the condenser elements, the lower ends of which face one another, in advantageous manner from dirt, rain and snow and from direct irradiation by the sun, which, especially during the hot seasons, may result in a considerable reduction of the cooling capacity. In consequence, with the V-shaped arrangement of the condenser elements it is possible to dispense with the capacity reserves which are necessary in the case of a roof-shaped arrangement for the contigency of direct solar irradiation. The special advantage of this arrangement of the condenser elements and of the screw fans Is, however, that there is a reliable separation of hot and cold air, since the hot air blown off in the upward direction by the screw fans flows off in the upward direction without special precautions owing to its kinetic energy and its lower specific weight, so that a fresh Intake of heated air with the resultant reduction of the cooling capacity is dependably avoided.

- 3 677166

A disadvantage of these air-cooled condensers having a V-shaped arrangement of the condenser elements, however, Is that In the case of low outside temperatures, especially in the case of severe frost, an unnecessary and impermissibly considerable under-cooling of the condensate readily occurs and may result in complete icing of the condenser. This naturally occurs first of all In the rows of tubes of the condenser elements which are first engaged by the cold air, so that these tubes are gradually clogged up by Ice plugs at the lower end connected to the condensate collector conduit. After the tubes of the rows of tubes first engaged by the current of cooling air have become clogged in this way through icing, the cooling air passes at a lower temperature to the region of the second row of tubes, so that ice plugs also form at the lower end of these tubes connected to the condensate collector conduit owing to the greater temperature gradient available. The same process ls repeated at very low outside temperatures, for example those of about 20°C, in some cases with the next rows of tubes as well, so that either the condenser becomes completely iced up or at least Its throughput capacity is greatly reduced. The mutually facing ends of the condenser elements connected to the condensate collector conduit are particularly liable to icing in these circumstances.

This sensitivity to low outside temperatures can be obviated according to the invention if the sides of the triangle formed by the condenser elements are connected in the middle or lower region of their height by an intermediate cover which is disposed preferably approximately in parallel relationship to the base of said triangle and which ls equipped with circulating air fans, which are

- 4 677166 adapted to be put into and out of operation optionally and which deliver in opposition to the direction of delivery of the main fans. These circulating air fans are put Into operation only at extremely low outside temperatures at which there is a risk of the condensate tubes icing up, while they are out of operation at medium and higher temperatures of the outside air. Owing to the fact that their direction of delivery is opposed to the direction of delivery of the main fans, the circulating air fans suck in air, which has already been heated by heat exchange with the condenser elements, from the inner space situated between the upper oovering and the intermediate covering, and force said air out through the lower region of the height of the condenser elements. In these conditions this air experiences a repeated temperature increase and is then sucked ln again for the major part by the main fans through the middle to upper region of the height of the condenser elements. Depending on the ratio between the delivery and pressure head of the main fans to the corresponding data of the circulating air fans a varying amount of the already repeatedly heated cooling air is then again sucked in by the circulating air fans and again forced out through the lower part of the height of the condenser elements.

Since, in the condenser proposed according to the invention, even in the case of a particularly severe frost the cooling air sucked in by the main fans through the upper and middle region of the height of the condenser elements is in every case heated to beyond the freezing point of the condensate, the fact that the lower ends of the condenser elements which are particularly sensitive

- 5 677166 to icing are subjected to the action of the hot air dependably avoids the latters* becoming clogged through Ice plugs. Since the hot air forced through the lower region of the height of the condenser elements by the circulating air fans undergoes a repeated heating at least at the Inner rows of tubes, there ls always available In the region of the particularly sensitive outer rows of tubes an air temperature which is so high that Icing of the same or undeslred under-cooling of the condensate ls dependably avoided.

In order to ensure that the lower region of the height of the condenser elements ls adequately subjected to the action of the current of cooling air drawn In by the main fans, when the outside temperatures have medium and fairly high values, that Is to say when the circulating air fans are out of operation, the Intermediate covering ls provided with closable passage apertures of large cross-section. These passage apertures are opened when the circulating air fans are put out of operation, so that the cooling air drawn In by the main fans through the lower region of the height of the condenser elements can flow through these and through the stationary circulating air fans.

In order to keep the resulting flow losses as low as possible and to ensure the most effective possible action of air on the lower ends of the condenser elements as well, It ls as a rule most advantageous for a considerable part - for example half to two-thlrds - of the surface of the Intermediate covering to comprise air flaps which can be moved Into the open and closed position.

In one advantageous embodiment, the condenser elements are divided by the Intermediate covering from the bottom to the top approximately In the ratio of 1:2.

- 6 677166

The effect thus achieved is that only the bottom third of the condenser elements, which Is particularly sensitive to undercooling of the condensate and lcing-up, is subjected to the action of the hot air at extremely low outside temperatures, while a mixture of cold air and circulated hot air is drawn in through the top two-thirds of the condenser elements. To enable very extensive adjustment to existing conditions to be carried out ln these circumstances, it ls advantageous to make the main fans and/or the circulating fans adjustable as regards speed.

As a rule, each main fan has associated with it a circulating air fan of smaller diameter which rotates ln approximately co-axial relationship to said main fan and with an approximately parallel plane of rotation. It ls, of course, possible to select some other arrangement and association if required, for example to associate with each main fan two circulating air fans which are staggered ln the longitudinal direction of the double row and which have a smaller diameter. In order to ensure the maximum uniformity ln the action of the air over the entire range of the height of the condenser elements when the circulating air fans are out of operation, It is also advantageous for the intermediate covering to be formed substantially by air flaps on both sides of the circulating air fans.

According to a further feature of the invention the circulating air fans are adapted to be put into and out of operation automatically ln dependency on the temperature of the outside air and/or of the condensate. In these circumstances it ls further advantageous for the air flaps also to be moved automatically into the open and closed position ln dependency on the temperature of the outside air

- 7 677166 and/or of the condensate. At the same time, the speed of revolution of the main fans is preferably adjustable automatically in dependency on the temperature of the outside air and/or of the condensate. This enables the changing-over of the condensing installation to fresh air and circulating air operation to be effected fully automatically in dependency on the temperature of the outside air and/or the condensate, so that even ln the case of relatively considerable fluctuations in the outside temperatures any undesirable or impermissible under-cooling of the condensate is dependably avoided without any maintenance and observation of the condenser installation. For this purpose, for example, lt ls possible to use a thermostatic control which, if a preferably adjustable outside air temperature and/or condensate temperature Is not attained, puts the circulating air fans into operation, closes the air flaps and throttles the speed of the main fans, while if a preferably likewise adjustable temperature of the outside air and/or of the condensate is exceeded lt puts the circulating air fans out of operation, opens the air flaps and changes the main fans to the full speed.

Since the amount of air to be circulated by the circulating air fans ls less than the amount of cooling air drawn ln by the main fans ln the case of fresh air operation, but on the other hand the circulating air fans have to operate against the negative pressure produced by the main fans, the circulating air fans are designed for a considerably smaller delivery, for example smaller by two-thirds, but for a greater pressure head than the main fans. When the circulating air fans are put into operation, the delivery of the main fans can ln addition usually be reduced to less than half - preferably to about one-third - 8 677166 of their delivery In the case of fresh air operation.

One exemplified embodiment of the invention is illustrated in the drawing, in which:

Figure 1 is a cross-section through a double row of the condenser,

Figure 2 is a plan view of Figure 1, the upper covering and the main fans being omitted,

Figure 3 is a condenser of the kind shown in Figures 1 and 2, partially in longitudinal section and partially in side view.

As will be apparent from the drawing, a relatively large number of condenser elements 1,2 disposed in such manner as to be inclined in the form of a V in relation to one another are disposed one after the other in double rows. The condenser elements 1,2 In the exemplified embodiment illustrated in the drawing comprise a relatively large number of finned tubes 3 of elliptical cross-section, which are of identical construction to one another and which are connected by their ends to common steam distributor chambers 4 and common condensate collector chambers 5. As illustrated diagrammatically in Figure 1, the steam distributor chambers 4 are connected to steam distributor conduits 6 extending in the longitudinal direction of the double row. As will be apparent especially from Figures 2 and 3« the steam distributor conduits 6 have a cross-section tapering conically in the direction of flow of the steam.

The condensate collector chambers 5 provided at the mutually facing ends of the condenser elements 1,2 are connected by connections 7 to a common condensate collector conduit 8 extending in the longitudinal direction of the double row.

The condenser elements 1,2, which are inclined in the

- 9 677166 form of a V in relation to one another, form in cross-section an approximately equilateral triangle, the corner points of which are formed by the steam distributor conduits 6 and the condensate collector conduit 8. The steam distributor conduits 6 are mounted on supports 9 which are disposed at Intervals from one another in the longitudinal direction of the double row. Since the supports need have only a relatively small cross-section and, as shown in Figure 3, may be disposed at relatively large intervals in the longitudinal direction of the steam distributor conduits 6, practically the entire opening between the steam distributor conduits 6 and the base 10 is available for the drawing in of the cooling air.

The top ends of the condenser elements 1,2, as will be apparent especially from Figure 1, are connected by covering hoods 11, which narrow upwardly in the form of a funnel or taper conically. In these circumstances, as will be seen in Figure 3, a common cover hood 11 formed with a circular intake aperture of large cross-section in the middle ls associated with a plurality of condenser elements 1,2 disposed successively in the longitudinal direction of the double row. The said intake aperture is bounded by an outwardly projecting annular flange 11a, on which ls flanged the flanged fan housing 12 of one of the main fans 14 disposed at Intervals from one another in the longitudinal direction of the double rows. An upwardly conically widening diffuser 13 ls flanged on the opposite end face of the cylindrical fan housing 12.

The main fan 14 is driven at an adjustable speed by a motor 15 which is indicated only diagrammatically in the drawing. The speed of the main fans 14 is to be at least reduced in comparison with its normal speed in such manner that the amount of air delivered from within ls reduced to about one-third of its normal delivery.

<img file="CA677166A_D0002.tif" />

As will be apparent especially from Figures 1 and 3, the condenser elements 1,2 are connected in the lower region of their height by an intermediate cover 16 which is disposed approximately in parallel relationship with the base of the triangle formed by the condenser elements 1, 2 and which extends over the entire length of the double row and is equipped with a number of circulating air fans 17 corresponding to the number of main fans 14. In the exemplified embodiment illustrated in the drawing the condenser elements 1,2 are divided approximately ln the ratio of 1:2 from the bottom to the top by the intermediate cover 16.

The most advantageous arrangement of the intermediate cover 16 will depend on the conditions at any given time, so that in other cases a different sub-division of the condenser elements will be preferable, for example ln the ratio of 1:3 or 2:3· In comparison with the main fans 14, the circulating air fans 17 have a smaller diameter and a much lower delivery, but are designed for a greater pressure head than the main fans 14. They are driven by motors 18, indicated only diagrammatically ln the drawing, with a axis of rotation which, if required, ls adjustable.

The fan housing 19 for the circulating air fans 17, as will be apparent especially from Figures 2 and 3, is provided with an approximately square base plate 20, which bears directly on the condenser elements by its sides facing the said condenser elements 1,2. The entire intermediate space between the base plates 20 of the circulating air fans 17 disposed at intervals from one another ln the longitudinal direction of the double row consists of rockably mounted air falsp 21, 22 of large cross-section, which can be moved optionally into the closed position illustrated In Figure 2 and into the open position indicated by broken lines in Figure 1 and solid lines in Figure 3. The operating devices serving for opening and closing the air flaps 21, 22 are not shown in the drawing.

When the outside air has medium and relatively high temperatures the circulating air fans 17 are put out of operation and the air flaps 21, 22 are opened. The main fans 14 rotating at the full operating speed draw fresh air in from outside over the entire height of the condenser elements 1,2 and force it through the diffuser 13 in the direction of the arrows χ_χ upwardly in these circumstances. When the outside temperatures are extremely low, a temperature-dependent control (not shown in the drawing) simultaneously closes the air flaps 21, 22 over the entire length of the double row, puts the circulating air fans 17 into operation and throttles the speed of the main fans 14. In these circumstances, as indicated by the arrows Xg, the circulating air fans 17 draw in heated air from the region situated between the upper cover 11 and the intermediate cover 16 and force it in the direction of the arrows x^ through the lower region of the height of the condener elements 1,2 in the outward direction. The major part of this circulating air, as indicated by the arrows x^, ls drawn in again by the circulating air fans 17 and main fans 14 acting jointly on the middle and upper region of the height of the condenser elements 1,2. Moreover, especially in the upper region of the height adjoining the steam distributor chamber 4, as indicated by the arrows x^, fresh air ls additionally drawn in.

Of the total amount of air drawn in laterally in the direction of the arrows xjp x^, by the main fans 14 and the circulating air fans 17, in the case of circulating air operation approximately half is drawn in in each case in the direction of the arrows Xg by the

A circulating air fans 17 and the other half in the direction of the arrows x^ by the main fans 14. It ls of course possible to provide some other ratio between the delivery of the main fans 14 and of the circulating air fans 17 by appropriate differentiation of the speed of the main fans 14 and of the circulating air fans 17. Regulation of the speed of the main fans 14 and of the circulating air fans 17 can In these circumstances likewise be effected by a fully automatic control which is controlled In dependency of the temperature of the outside air and/or of the condensate.

In this way It ls not only possible to avoid Icing up of the condenser elements at extremely low outside temperatures but also any undeslred and unnecessary under-cooling of the condensate.

If a preferably adjustable temperature of the outside air and/or of the condensate .Is exceeded, the thermostatic control (not shown in the drawing) puts the circulating air fans 17 out of operation, opens the air flaps 21, 22 and again switches the main fans 14 over to the full operating speed. The largest possible open position of the air flaps 21, 22 In these circumstances le so selected that they are disposed In approximately parallel relationship to the direction of flow of the fresh air drawn In by the main fane 14.

A further advantage of the Invention ls that In the case of relatively cool outside temperatures It ls in some cases possible even without putting the circulating air fans 17 Into operation, simply by complete or partial closure of the air flaps 21, 22, to avoid under-cooling of the condensate In the region of the end of the condenser elements 1,2 connected to the condensate collector chambers

5. By such a complete or else partial closure of the air flaps 21, 22 the current of cooling air drawn in hy the main fans 14 is throttled to a varying degree in the region of the height of the condenser elements 1,2 situated below the intermediate base 16, so that there is correspondingly less cooling of the condenser tubes·

- 14 677166 'ΠΙΕ EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS