US2239685A - Heat exchanger - Google Patents

Description

April 29, 1941.

w. G. NoAcK HEAT EXCHANGER I Fi led March s, 1946 Patented Apr. 29, 1941 UNITED STATE HEAT EXCHANGEB Walter GustavNoaok, Baden, Switzerland, as-

signor to Aktiengesellscliaft Brown, Boveri &

Cie, Baden, Switzerland Application March 5, 1940, Serial N 322,385 In Germany March 15, 1938 4 Claims. (01. 257-238) This invention relates to heat exchangers andparticularly to high pressure, high velocity heat exchangers for the production of steam.-

In heat exchangers that are heated by hot gases at high pressure and high velocity in order to increase the rateoi heat exchange and espegcially the heat transfer per unit of surface, particularly when the product (V. D.) of the velocity in meters per second and the density in kilograms per cubic meter exceeds 30 kg./sec. m for exv ample, it is desirable that the hot gases flow par- I allel' to the tubes. The; more favorable the construction in the active heat exchanging section of the device, the more difiicult it is to provide a satisfactory and practicable construction for the inlet and outlet ends. At the two ends of the heat exchange device, the entering and leaving stream of hot gas must cross the stream of liquid tion;

and must be forced between the tubes, which are very narrow due to the high V. D. value, whereby great pressure losses are caused and .the rates of .flow are decreased.

In heat exchange devices for vaporizing liquids, however, bundles of pipe of a number of parallel sections or coils of pipe traversed successively, such as are commonly used, for instance, in super-heaters, cannot be used since the pipes will be comparatively short due to the high heat conversions. The entire length of pipe therefore consists generally only of one pipe section or at most two, and the number of inlet and outlet connections is therefore at least as great as the number of pipe sections. An important condition for the efliciency of heat exchange devices with high V. D. values, however, is particularly the unhindered admission of hot gases into the heating passages, in order to prevent loss of pressure and fouling o! deposits of cinders.

Tubes have already been described inwhich the admission and removal of the liquid, to and from the heated section is effected at one and,

the same end of the tube, in that a second tube is built into the tube forming the actual heating ,surface, through which the'liquid is conducted to the opposite end. In this way, a certain strucnot extending past the gas inlet the other portions not extending past the gas outlet,

whereby gas inlet and outlet passages of substantially increased area are provided.

The invention will be more particularly described with reference to the accompanying drawing in which: a

Fig. 1 is an elevation in partial section of a steam generating devioeincluding a heat exchanger embodying the principles of the inven- Fig. 2 is a section on line 1-2" of Fig. 1;

Fig. 3 is a partial elevation of a modified form of the invention; and

Fig. 4 is a fragmentary enlarged sectional view of the device or the invention. I

In Fig. 1, l is the combustion chamber, the air being admitted at 2, and the fuel, such as gas, oil or coal dust, at I. 4 isthe actual'vaporizing device that is constructed according to the invention. It consists of two groups- oi tubes 30 and 30 that are collected in the manifold chambers,

5 and 5'. Feed water is admitted to the manifold chambersat 6 and 8', and the steam or steam and water mixture are withdrawn at I or-l'.

The feed water is conducted to'the end of the tubes through tubes of smaller diameter located inside the actual vaporizing tube, and then flows back in the annular space between the inner and outer tube to the manifold chambers, as is shown at the right in Fig. 4. The tubes of the two groups end at the inlet and outlet cross-sections,

respectively, of the hot gas passage. The inlet opening is preferably enclosed by a nozzle ring 8 which decreases irregularities of flow. This is made possible by the large inlet cross-section that is provided by the termination'of a part of the tubes at the inlet section of the gas passage.

Fig. 2 is a section through the outlet gas passage on a lar r scale. The mi ing a of the tubes assures good inlet and outlet ratios, especially in 'tural simplification is attained, but this con-- heating tubes with a high -V. D. value '(over30 connection with the comparatively great widths v b and b. The hot gas leaves the heat exchange device at 9.

Fig. 3 shows a similar vaporizing device. The

feed or the water and the discharge of the steam and'water mixture to and from the second manifold chamber 5' takes place through two concentric tubes III and II that are connected to thecorresponding chambers of the manifold chamber 5.

kg/s e. m), m which a'plurality of straight axis heating tubes are provided, a portion of the tubes In the enlarged fragmentary section shown in Fig. 4, I2 is the outer tube and I1 is the inner tube. li is a part of the manifold chamber.

From chamber It the feed water passes"through the inner tube I! to the end thereof and thence screw closures 20, or suitable covers, are provided.

I claim:

1. A heat exchange device, especially for the production of steam from hot gases at high pressures and velocities, comprising means forming an elongated chamber, said chamber having a gas inlet adjacent one end of said chamber and a gas outlet adjacent the other end of said chamber, and a plurality of tubes extending lengthwise of said chamber, inner tubes substantially. concentrically positioned within the first-mentioned tubes for the flow of fluid to the ends of the outer tubes whereby fluid may be supplied to and withdrawn from one end of said tubes, and at least a portion of said tubes terminating in said chamber short of the gas inlet thereof and the other portion of said tubes terminating in said chamber short of the gas outlet thereof.

2. A heat exchange device, especially for the production of steam from hot gases at high pressures and velocities, comprising means forming a chamber, said chamber having a gas inlet adjacent one end of said chamber and ages outlet adjacent the other end of said chamber, a manifold at each end of said chamber, a plurality of concentric tubes extending from each of said manifolds lengthwise of saidchamber and terminating short of the ends of said chamber, and means in said manifolds for supplying fluid to the inner tubes of said concentric tubes and withdrawing fluid from the outer tubes of said concentric tubes, and a large tube and a concentric tube within said large tube passing through said chamber and connecting the inlet and outlet portions of one of said manifolds with the corresponding portions of the other of said manifolds.

3. A heat exchange device, especially for the production of steam from hot gases at high pressures and velocities, comprising'means forming an elongated cylindrical chamber, said chamber having a gas inlet adjacent one end of said chamber and a' gas outlet adjacent the other end of said chamber, a plurality of tubes extending lengthwise of said chamber, inner tubes substantially concentrically. positioned within said first-mentioned tubes for the flow of fluid to the ends of the outer tubes whereby-fluid may be supplied to and withdrawn from one end of said tubes, at least a portion of said tubes terminating in said chamber short of the gas inlet thereof, and the other portion of said tubes terminating in said chamber short of the gas outlet thereof, and a flow-directing nozzle-like member positioned at the entrance to said chamber.

4. A heat exchange device, especially for the production of steam from hot gases at high pressures and velocities, comprising means forming a chamber, said chamber having a gas inlet adjacent one end of said chamber and a gas outlet adjacent the other end of said chamber, a manifold at each end of said chamber, a plurality of concentric tubes extending lengthwise of said chamber, means in said manifolds for supplying fluid to the inner tubes of said concentric tubes and withdrawing fluid from the outer tubes of said concentric tubes, at least a portion of said tubes terminating in said chamber short of the gas inlet thereof and the other portion of said tubes terminating in said chamber short of the gas outlet thereof, and removable closure mem- Eezs in said manifolds opposite the ends of said u es.

WALTER GUSTAV NOACK.

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