US2717767A - Heat exchanger - Google Patents

Description

HEAT EXCHANGER Georges Servau Cantacuzene and Carmen Marguerite Cantacuzenc, born Skeletti, Paris, France Application July 29, 1952, Serial No. 301,508

Claims priority, application France August 2, 1951 8 Claims. (Cl. 257-236) This invention relates in general to heat exchangers and more particularly to improved means for increasing the total heat transfer coeflicient between fluids flowing the one externally and the other internally of a nest of tubes.

According to the invention adequate means are provided for on the one hand forcing the external liquid along a path substantially at right angles to the tube axes, on the other hand suppressing the zones wherein, as observed in conventional arrangements, eddies occur in the liquid due to the use of deflectors or baffle means, and finally for increasing the velocity of flow of the fluid to be heated between the inlet and outlet of the heat exchanger.

In order that the invention may be clearly understood there is shown in the accompanying drawing by way of example a typical embodiment thereof consisting of a fuel oil heater operated by the steam condensing within the bundle of tubes. In the drawings:

Figure 1 shows diagrammatically a longitudinal vertical section of the apparatus;

Figures 2, 3, 4 are cross-sectional views of same taken upon the lines AB, CD and EF of Fig. 1;

Figure shows at a reduced scale a heater according to the invention mounted in the bottom portion of a large storage tank.

In the drawings, 1 is the cylindrical metal shell of the heater, 2 the tubes of the heating unit, 3 the front cover and 4 the rear cover of the heater. Steam is introduced at 5, condensed water is expelled at 6 and cold fuel is fed through the orifices 7 provided along the bottom portion of shell 1. The heated-fuel outlet fitting is shown at 8. The chamber formed inside the cover 3 is divided into an upper and lower front header by a horizontal plate 9 engaging the vertical plate 10 in which are secured the front ends of the tubes. Steam is fed to the tubes above this partition 9 and the condensed Water flows from the tubes beneath this partition. The bulged rear cover 4 is fixed through its peripheral edge to that of a vertical perforated plate 11, the rear ends of tubes 2 passing freely through the orifices in this plate to allow for linear expansion. This arrangement for circulating steam and condensed water (or any other fluids as currently used in heat exchanger practice) has no specific features and corresponds to the usual technique.

A sheet-metal trough 12 having its rear edge in fluid tight engagement with the rear plate 11 is open at the front (see cross-section CD Fig. 3) and constitutes a means for collecting the fuel fed through the orifices which is thereby caused to flow from the rear end to the front end of the apparatus. The front edge of trough 12 is in sealed engagement with the edge of a notch formed in the upper portion of a perforated vertical front plate 13 shown in section Fig. 3, the tubes passing through this plate 13 which has its peripheral edge in fluid-tight engagement with the inner wall of the shell 1 so as to form a free passage for the fuel through the aforesaid notch the shape of which corresponds to the cross-sectional area of the trough.

2,717,767 Patented Sept. 13, 1955 ice The above-described apparatus operates as follows:

The heat exchanger is fastened to the side wall of a storage tank, by means of a flange (Fig. 3) located at the section C-D of Fig. 1 and as the tank is filled with fuel to a level higher than that of the orifices 7, fuel penetrates into the apparatus through these orifices up to a level which is a function of the fuel level in the tank and of the viscosity of this fuel. As a consequence, the air trapped in the upper portion of shell 1 is compressed. When the operation of the device is started by introducing steam through the tubes and exhausting the fuel by means of a suction pump connected to the outlet fitting 8, the fuel level in the heater is adjusted by means of a valve 15 adapted either to vent air with the assistance of the hydrostatic pressure produced in the fuel, or to allow external air to penetrate into the device on account of the vacuum produced by the pump. When normal working conditions are reached the fuel level stabilizes itself below a free zone 14 in the cylindrical space bound by plates 13 and 10 and can be controlled by means of a gauge-level 16 or equivalent device. A pressure gage 29 can be adopted in order to check the relative vacuum and/or pressure in space 14. Since the relative vacuum developed by the pump suction in zone 14 is equal throughout the length of the preheater the suction produced across the various fuel inlet orifices 7 will be equal, irrespective of the distances between each orifice on the one hand and the front end of the heater on the other hand. Therefore, at all points of the device the fuel movement will take place substantially at right angles to the tubing. The fuel will flow by gravity over the longitudinal edges of trough 12 and then in and along the latter toward the header formed between plates 13 and 10 from which it is discharged through the outlet 8. Constructionally, there are no local eddy-forming zones. Besides, as the total areas of the inlet orifices 7 is a multiple of the cross-sectional area of the outlet aperture 8 and as the cross-sectional area between the tubes, as defined by the inner Wall of shell 1 and the lateral walls of trough 12, decreases in the upward direction, the velocity of flow of the fuel will be accelerated with its temperature, that is with its decreasing viscosity.

Whatever the type of suction heater utilized in the fuel tank, it is current practice to dispose a preheating coil 17 on the bottom of the tank (Fig. 6) for promoting the circulation of fuel toward the heater 19.

If needed, and still according to the invention, a horizontal metal plate 18 will be mounted above the exchanger 19 to prevent the preheated fuel from rising too high in the tank and escaping from the suction exerted by the exchanger 19.

It will be noted that the invention, in addition to the increase in the thermal transfer coefficient it provides, is also advantageous in that it makes it possible to adjust the steam/fuel output ratio to the optimal value. In fact, if for a given thermal output the amount of fuel taken by the pump is excessive, the fuel level in the trough zone 14 will decrease and the steam input must therefore be increased. Conversely, if the thermal output is too high for the suction capacity of the pump, said fuel level will increase and it will be necessary to reduce the steam input (or to augment the suction if the pump is of the variable-output type). The heat exchanger according to the invention may be used as a cooler by circulating the liquid to be cooled in the shell and the cooling medium through the tubing. It will also be possible to utilize the exchanger according to this invention as a condenser by circulating the steam to be condensed through the tubing and the cooling medium in the shell.

Of course, the free space 14 may be dispensed with without departing from the invention, but this would reduce the efliciency of the device.

On the other hand, the abovedescribed form of embodiment constitutes but a mere example given-for explanatory purposes. Other forms of embodiments may be devised by varying as most convenient for each case the arrangement of the inlet orifices for the fluid to be heated or cooled, the shape of the shell, the arrangement and shape of the wall by which the fluid path is deflected externally of the nest of tubes toward a trough or like channel, the arrangement and means for controlling the upper free zone of fluid, etc.

What we claim is:

1. A heat exchanger comprising a horizontal closed cylinder, a bundle of longitudinal tubes mounted in said cylinder for circulating a first fluid in said cylinder, an inlet and an outlet for said first fluid in said tube bundle, orifices spaced along the cylinder at the lower portion thereof to enable a second fluid to enter said heat exchanger, a longitudinal partition having a substantially horizontal upper edge and forming in said cylinder a space into which said second fluid admitted through said orifices can enter only by flowing over the upper edge of said longitudinal partition, said upper edge being positioned at a level higher than at least the major part of said longitudinal tubes, and means for discharging said second fluid from the bottom of said space.

2. A heat exchanger according to claim 1, in combination with means for drawing said second fluid into said heat exchanger through said orifices disposed at the lower portion thereof, a level gage for checking the height of the second fluid in said space formed by said longitudinal partition, a pressure gage for checking the vacuum produced in said heat exchanger above the level of said second fluid and a valve for limiting said vacuum.

3. A heat exchanger according to claim 1 comprising at its upper portion a valve for limiting the pressure of the air trapped above the level of said second fluid.

4. A heat exchanger according to claim 1 comprising at its upper portion a valve for limiting the air pressure above the level of said second fluid and a pressure gauge for checking said air pressure.

5. A heat exchanger according to claim 1 comprising a measuring instrument visible from the outside for checking the level of said second fluid inside said cylinder.

6. A fluid heater according to claim 1 wherein the total of the cross-sectional areas of said inlet orifices is substantially greater than the cross-sectional area of said exhausting means.

7. A heat exchanger comprising a horizontal cylinder, headers closing said cylinder at either end thereof, a pair of vertical plates forming with said headers a chamber at each end of said cylinder, and a set of longitudinal tubes the ends of which pass through said vertical plates in fluid-tight engagement therewith so as to connect said chambers with each other, means for circulating a first fluid through said tubes, orifices spaced along the lower portion of said cylinder, between said vertical plates, to enable a second fluid to enter into said heat exchanger, means for drawing said second fluid through said orifices, a longitudinal trough disposed in the upper portion of said cylinder, said trough comprising at least one longitudinal edge over which the second fluid may flow to enter said trough, and means for discharging said second fluid from said trough.

8. A heat exchanger comprising a horizontal cylinder, headers closing said cylinder at either end, a pair of vertical plates forming a chamber at either end of said cylinder, a set of longitudinal tubes the ends of which pass through said vertical plates in fluid-tight relationship therewith so as to connect said end chambers with each other, means for circulating a first fluid through said tubes from one chamber to the other chamber, a vertical partition forming with one of said vertical plates another chamber for collecting a second fluid, orifices spaced along the lower portion of said cylinder between said vertical partition and the other vertical plate for enabling the second fluid to enter said heat exchanger, a longitudinal trough provided at the upper portion of said cylinder and in fluid-tight engagement with said vertical partition at one end and with said other vertical plate at the other end, said trough comprising at least one edge over which the second fluid may flow to enter into said trough, a passage in said vertical partition to allow the second fluid to flow from said trough to the fluid collecting chamber, and means at the bottom of said fluid collecting chamber for discharging said second fluid from said heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS 1,604,988 Gilchrist Nov. 2, 1926 2,060,078 Hobbs Nov. 10, 1936 2,145,614 Stambaugh Jan. 31, 1939 2,499,302 Emhardt Feb. 28, 1950

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