US1456255A - Apparatus for hkat exchange - Google Patents

Description

May 22, 1923. Y v 1,456,255

E. SHAW APPARATUS 'FOR 'HEAT EXCHANGE Filed Jan. 25 1918 a Sheets-Sheet 1 I I 5 Y l j N f a P p [0; @mmwm h w m I! S I I I a I n May 22. 1923,

' 1,456,255- E. SHAW Patented May 22, 1923.

EDWARD SHAW, F TORONTO, ONTARIO, CANADA.

APPARATUS FOR HEAT EXCHANGE.-

Application filed January 25, 1918. Serial No. 213,756.

To all whom it may concern:

Be it known that I, EDWARD SHAW, a subject of the King of Great Britain and Ireland, residing at Toronto, in the Province of Ontario, Canada, have invented certain new and useful Improvements inApparatus for Heat Exchange, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to improvements in the apparatus for heat exchange of which the following is a description.

The present improvement has relation to the transferring of heat from one fluid to another fluid, through an intervening heat conducting wall, in a new and improved way, whereby there is a large increase in efliciency over the methods and apparatus heretofore used and known to me.

The invention pertains to an apparatus, wherein the two fluids are in motion at opposite sides of a suitable wall, through which the heat is conveyed from the fluid at one side of the wall, to the fluid at the other side of the wall.

My'invention may be used for either heat ing or cooling liquids.

It is well known that among the obstructions to the rapid flow of heat between fluids having different temperatures on either side of a metal wall, is the existence of films which tend to cling to the walls.

These films are of small depth, but appear 5 to operate almost as if they were a different nature from the bulk of the liquid and when in motion tend to follow the wall surfaces. 7

They appear to move slowly over the surface andthey appear also, in the case of a liquid, to interchange their particles very slowly, if at all, with the bulk ofthe liquld, and it is probable that the flow of the heat is mainly obtained through their conductivity, which is small.

These films, further, are objectionable on account of their providing an almost stagnant layer in which the liquid tends to evaporate and thus cause the. deposit of solids on the metal surface.

The primary object of my presentinvention is to break up these fluid films in the flowing liquids, thus avoiding the consequent obstruction to therapid transfer of heat between the wall engaging surfaces of the two fluids, located at opposite sides of the wall, whereby there is a marked increase of efliciency in the transfer of heat between the two fluids.

I attain my object by employing tubes each having a plurality of reverse bends formed longitudinally thereof and by causing the fluid to flow through said tubes at high velocity. The fluid is thus caused to exert a violent scouring action alternately against opposite sides of the walls of the tubes which tends 'to break up the films which always tend to form on the walls.

By this arrangement I attain great efficiency as compared with ordinary straight or spirally coiled tubes. This breaking up of the films is no doubt partly due to friction on the walls of the tube and partly also to the fact that in passing round a bend the fluid tends to take up a rolling movement in one direction, whereas on reaching the reverse bend a force immediately begins to act on it tending to cause a rolling movement in the reverse direction. ,This

movement not only tends to break up the films, but also causes such disturbances in the main body of the fluid as to tend to cause every particle therein to be brought repeatedly close to or into contact with wall surfaces.

The apparatus hereinafter described, disclosed and claimed, is more particularly adapted for eflicient use in connection with viscous or thick fluids where the adhesion of the particles of the fluid tends to utilize the general movement of the fluid in tearing away and reducing the thickness of the film, or in some cases the coagulated layer of fluid which is being forced through the pipe. Owing to the peculiar movements given the fluid by this method and apparatus, it can aptly be designated as the wriggle heat exchange.

The apparatus here disclosed and claimed, can of course be advantageously used as a heat exchange for other fluids than those for which it is more particularly constructed as above stated.

The invention is hereinafter more fully described and is illustrated in the accompanying drawings in which Fig. 1, is a perspective view of one form of my device with the face plates or cover removed.

Fig. 2, is an enlarged longitudinal sectional detail taken through one section of my device.

Fig. 3, is an end view of one of the section casings showing the position of the duct by dotted lines.

Fig. et, is a sectional view showing an alternative construction of inlet.

Fig. 5, is an alternative construction of my device, the outer casing being broken away and in section to show the arrangement of the coils.

Fig. 6, is a perspective detail of one of the coil elements shown in Fig. 5 and intermediately broken away of its length.

Fig. 7 is an enlarged sectional view of part of Fig. 2..

1 Referring now to Figs. 1, 2 and 3:

1, 2, 3 and 4 indicate a series of casings or coil containers in each of which is formed a serpentine duct 5 formed by two series of alternately arranged bosses 6 and 7. Each boss comprises a narrow neck portion 8 and a head 9 of cylindrical form, the head of one series being located in the space formed between the neck portions 8 of two adjacent bosses of the opposing series and thereby forming a serpentine passage extending longitudinally of each casing 1, 2, 3 and 4 and composed of a series of alternately arranged convolutions, each of which is in i the form substantially of a three quarter circle. Through the ends of each casing, l, 2, 3 and 4 extend a series of copper tubes 10, each of which is bent in a series of convolutions, the radius of which is as small as possible, the convolutions arranged in such a manner that in its final form the tube consists of a series of partial circles, which after describing about three quarters of a convolution, take an opposite curvature to the same extent.

The tubes 10 pass through the duct 5 and fit freely therein to form a surrounding passage between the exterior wall of the tubes 10 and the interior wall of the duct.

It will be seen that a liquid forced through suchatube 10 will be subject to an increased resistance on the concave surface of the interior of the tube when passing around abend and would tend to roll, the continued v forward movement of the liquid will take it through the bend of reverse curvature, where the liquid pressure against the new concave surface will tend to reverse the direction of the rolling action.

A similar action occurs when fluid is forced through the ducts 5 producing the alternate reverse rolling action to scour the outer surface of the tubes 10. In order to increase this action I sometime find it advisable to place in the outer passage, bars or ribs 11, which have the effect when alternately placed on the interior of the duct 5 on opposite sides of the tubes 10, and extending inward towards the said tubes, of deflecting the fluid across the tubes, so that a scouring effect is produced on the tubes not merely from the rotary movement of the water but from its movement in a confined space across the direction of the tubes. In Fig. 7 the fluid is deflected in the manner shown by arrow g. It will be understood that in the absence of the ribs 11, the fluid would flow undisturbed through the duct 5, but by placing the ribs 11 as above described, the flow is deflected causing the scouring action above referred to.

Apparatus constructed in this manner for a transfer of heat between liquids has been found to give a heat transfer of 420 B. T.

I]. per square foot, per hour, per degree surfaces are kept almost clean, and in practice it is necessary to wash out the tubes only once every twelve hours. Straight tubes in straight ductsunder similar conditions gave less than 200 B. T. U. transference.

In the construction shown in Figure 1 the tubes 10 "of the casing sections 1 are connected by unions 14 and 15 and tubes 16 to an exterior header 12 to which the supply pipe 13 is connected controlled by a suitable valve 17. The opposite end of the tubes 10 of the casing section 1 are connected by unions 18 and 19 and connecting pipes 20 to the tubes 10 of section casing 2. Similarly the tubes of the section casings 2 and 3 and 4 are connected re spectively by connecting pipes 20 and 21, the opposite end of the tubes 10 of the easing 4 being connected by pipes 22 and suitable unions to a header 23 from which leads the discharge pipe 24. V

By this means a continuous passage is formed for fluid through the interior of the tubes 10 from the inlet header 12 to the discharge 23. i

A similarand preferably reverse flow is formedthrough the ducts 5 from the inlet pipe 25 leading into one end of the casing 4 the fluid passing through the passage 5 of the casing l to the opposite end and to a discharge pipe 26 leading into the casing 3, the fluid passing similarly througlrthe casing 3 and discharging through the pipe 27 into the casing 2 and to the opposite end to the discharge 28 into the casing 1 and passing at the opposite end ofthe casing 1 into the final discharge pipe 29.

By having the liquids flow .in opposite directions, the fluid to be cooled or heated (as the case may be) gradually changes in temperature from its entrance to its exit, and before reaching the exit it is subjected to the most effective temperature (greatest heat or cold) of the other fluid at its inlet zone.

In Fig. 4 is shown an alternative form of head. In this form the head 30 is tubular and extends across the interior of the casing, the outer end being reduced at 31 to form a shoulder 31* suitably packed, the reduced portion passing through the orifice 32, the reduced portion is threaded and provided with a securing nut 33.

Another form in which the pipe may be bent is shown in Figs. 5 and 6, in which case the pipe 34: is bent as at 34 to a further degree around a circle, at the same time having a spiral direction in the form of a figure 8, so that the final form of the pipe is much more compact, and the direction of the fluid is not in one plane but moves through a path nearly at right angles to the circular convolutions, which as before stated approximates to a figure 8.

The conditions existing between the inner surface of the tube and the liquid are nearly the same in both cases but the construct-ion admits of two totally different ways of dealing with the fluid circulation outside the pipes. The former method is advantageous where it is desired tomaintain a low temperature difference between the two fluids, while the latter is more useful where a large temperature difference is not objected to, as in the-case of cooling a hot liquid where an abundance of cold water is available. In the latter case a much greater amount of hot liquid can be cooled per foot of copper surface. The figure 8 formations extend spirally crosswise of the container 35 and are arranged in sections extending longitudinally of the container inter-connected alternately at each side of the container to form a unit having its inlet at 36 and its outlet at 37. 38 indicates the inlet for the cooling fluid and 39 the outlet, thereby carrying the cooling fluid in the reverse direction to the fluid passing through the pipes 34. The units are piled one on top of the other in the container. 40 indicates dummy cooling sect-ions de signed to fill in and guide the cooling fluid.

The sections are packed to interengage and form substantial serpentine interspaces through which the cooling fluid is forced.

A cooler of the latter kind can be made by combining the convolutions of the tubes in such a way that they form a fairly compact mass which can be inserted in a suitably constructed box (see Fig. 5) the water in this case being obstructed in its passage either lengthways or to and fro across the box by the copper tubes only. This form,

while giving very good results so far as the cooling of the liquid is concerned, is not so satisfactory as regards the efliciency of the water circuit.

The apparatus herein described is particularly adapted for use in connection with fluids possessing considerable viscosity, which are particularly liable to form films in contact with the surface of the conduit through which they are forced, but which are not so well adapted to be treated in the manner described in my co-pending application No. 313,124. Owing to the nature of the movement given the fluid in the apparatus shown in the said application it may aptly be referred to as the jolt tube device.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. Apparatus for transferring heat from one fluid to another comprising a tube having a plurality of reverse bends formed longitudinally thereof without straight connecting portions whereby fluid flowing through the same at high velocity flows always in curved paths and is caused to, exert a violent scouring action alternately against opposite sides of the walls of the tube, and a casing, in which the tube is enclosed, paralleling the bends of the exterior wall of the tube and forming narrow passages at opposite sides of the tube for the flow of a second fluid, whereby any films tending to form at either side of the walls through which heat transference takes place are broken up and the transfer of heat facilitated.

2. Apparatus for transferring heat from one fluid to another comprising a plurality of tubes constructed as set forth in claim 1 and located side by side, the enclosing casing being provided with a serpentine duct conforming substantially to the bends of the tubes and having its curved walls spaced therefrom but sufficiently close to produce the outside scouring action set forth. 7 3. Apparatus for transferring heat from one fluid to another as set forth in claim 2 provided with transverse inclined ribs on the curved walls of the duct serving to space the tubes from said walls and to cause a partial transverse movement of fluid in the duct.

4. Apparatus for transferring heat from one fluid to another constructed as set forth in claim 1 in which each bend subtends substantially an arc of 270.

In testimony whereof I hereunto affix my signature in the presence of two witnesses.

EDWARD SHAW.

Images