US3884297A

US3884297A - Annular flow heat exchanger

Info

Publication number: US3884297A
Application number: US331514A
Authority: US
Inventors: Clark E Fegraus; Jimmy G Sundahl
Original assignee: Automotive Environmental Systems Inc
Current assignee: Clayton Manufacturing Co
Priority date: 1973-02-12
Filing date: 1973-02-12
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20

Abstract

Gas of constant or widely varying temperature enters an integral plenum from which the gas is caused to flow radially. The radial flow alternates between outward and inward flow with short axial displacements between cycles which lead the gas to an integral outlet plenum. These flow paths are determined by transverse discs which act as heat transfer fins and baffles where required. A number of axial tubes which pass through the fins at right angles carry a cooling liquid which controls the temperature of these tubes and the transverse discs. As the gas flows along the surface of the fins and over the tubes it gains or loses heat until its temperature closely matches that of the liquid in the tubes, thus the gas exits the heat exchanger at a controlled temperature. This arrangement lends itself to an application where hot exhaust gas and ambient air are mixed as they enter the inlet of the heat exchanger. The gas mixture then flows around a number of axially spaced heat transfer fins in a path that includes radial and axial directions. This action thoroughly mixes the gases for sampling and analysis. The attachment of a positive displacement pump at the exchanger outlet maintains a constant mass flow of the gas mixture for quantitative determination.

Description

United States Patent [1 1 Fegraus et al.

[451 May 20, 1975 1 1 ANNULAR FLOW HEAT EXCHANGER [75] Inventors: Clark E. Fegraus; Jimmy G.

Sundahl, both of San Bernardino. Calif.

[73] Assignee: Automotive Environmental Systems,

Inc., San Bernardino, Calif.

[22] Filed: Feb. 12, 1973 [21] Appl. No.: 331,514

[52] US. Cl 165/145; 165/158 [51] Int. Cl F285 9/22 [58] Field of Search 165/141, 145, 51, 157-161,

[56] References Cited UNITED STATES PATENTS 1,948,550 2/1934 Voorheis 165/161 2,138,001 11/1938 Fluor, Jrv 60/320 3,700,029 10/1972 Thrun 165/51 Primary Examiner-Charles Sukalo Attorney, Agent, or FirmMorris Liss [57] ABSTRACT Gas of constant or widely varying temperature enters an integral plenum from which the gas is caused to flow radially. The radial flow alternates between outward and inward flow with short axial displacements between cycles which lead the gas to an integral outlet plenum. These flow paths are determined by transverse discs which act as heat transfer fins and baffles where required. A number of axial tubes which pass through the fins at right angles carry a cooling liquid 4 which controls the temperature of these tubes and the transverse discs. As the gas flows along the surface of the fins and over the tubes it gains or loses heat until its temperature closely matches that of the liquid in the tubes, thus the gas exits the heat exchanger at a controlled temperature.

This arrangement lends itself to an application where hot exhaust gas and ambient .air are mixed as they enter the inlet of the heat exchanger. The gas mixture then flows around a number of axially spaced heat transfer fins in a path that includes radial and axial directions. This action thoroughly mixes the gases for sampling and analysis. The attachment of a positive displacement pump at the exchanger outlet maintains a constant mass flow of the gas mixture for quantitative determination.

6 Claims, 7 Drawing Figures PATENTED MAY 2 01975 SHEET 2 OF 3 ANNULAR FLOW HEAT EXCHANGER FIELD OF THE INVENTION The present invention is related to a heat exchanger, which mixes two gases entering an inlet. More particu larly, the invention is related to a heat exchanger which employs liquid coolant to control the temperature of the gases while internal tube and fin heat exchangers facilitate high gas flow rates. The gases flow together through the exchanger via radial and axial directions.

THE PRIOR ART In pursuance of the analysis of automotive emissions, it is imperative to achieve a constant mass flow of internal combustion engine exhaust gas and ambient air that is mixed with the gas such that the mass flow of the mixture is constant while the proportions of either gas vary. The mix; are is cooled or heated by a heat exchanger as required to maintain a fixed outlet temperature and has an outlet that should deliver a constant density flow therefrom.

Because the temperature of this mixture may vary over a large range at the inlet of the exchanger, but must be constant within a tolerance at the outlet, the heat exchanger is called upon to perform an extremely precise heat transfer function. Previously available heat exchanger designs have not met these requirements. A primary deficiency in many previously tried heat exchangers comes about because these heat exchangers lack sufficient tortuous path directions to effect the mixing of gases as they are cooled by heat exchanger fins. Furthermore, previously tried heat exhangers lack the large surface area on the gas side of the heat exchanger to effect proper heat transfer. Those which do meet these requirements are invariably either too large or suffer too high a pressure drop in the flow of the gas.

The prior art, as exemplified by US. Pat. No. 2,625,l38, discloses a heat exchanger, and more particularly a stand boiler having annular axially spaced baffles which causes water within the boiler housing to traverse a symmetrical path between the baffles. The path includes alternating radial and vertical directions for producing greater thermal efficiency and a considerably more even temperature distribution throughout the body of heated water. Vertical fluid tubes pass through the baffles to promote heat exchange. The design exposes hot gas to the smaller inside surface area of the tubes and water to the larger outside area. The design has no provisions such as fins or extended surface areas to increase heat transfer from the gas to the tubes which are exposed to the liquid. It must be in a vertical position to operate.

Although the prior art, such as the mentioned patent, achieves desirable heat exchanger results, this type of exchanger does not provide for allowing the gas to flow radially over fins and the outside surface of tubes. Since heat transfer from a liquid to a tube is far more rapid than from a gas to a tube, it is necessary to have an improved heat exhanger wherein the gas is exposed to far greater surface area including fins than the liquid. Moreover, it is necessary to provide for the mixing of two gases, namely ambient air and hot emission exhaust. Accordingly, an improved exchanger is required to achieve the improved heat transfer for precise temperature control applications, and the mixing and commensurate constant mass flow of mixed gases as required by pollution analysis applications.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention includes a heat exchanger having a symmetrical flow path with alternating radial and axial directions and may be oriented in any operating position. However, the heat exchanger not only includes the axially spaced annular baffles but also fins which exchange heat during radial flow and specially designed inlet means for causing simultaneous delivery of air and emission exhaust gases. Further, the fin as sembly within the exchanger provides for many divisions and blendings of the gas for promulgating mixture of the incoming gases. To insure that a constant mass flow of air and internal combustion engine exhaust gases is maintained, the heat exchanger has its outlet coupled to a positive displacement gas pump. The combination of these components achieve the desired constant results. However, constant mass flow would be extremely difficult to achieve were it not for the homogeneity of the air/exhaust mixture produced by the heat exchanger. Analysis of the gas requires homogeneity also. Moreover, constant mass flow could not be achieved without constant pressure drop and outlet temperature. This precise temperature control is augmented by provisions for symmetrical coolant flow and reverse flow where the coolant enters the end of the heat exchanger from which the gas exits. This feature is essential for precise temperature control because the coolant temperature is affected by further heat transfer with the gas as it travels through the heat exchanger. It is desirable to have the last interchange of the gas to be the first interchange with the coolant whose temperature is controlled by other means.

In operation of the present invention, the radial flow heat exchanger is used to mix a varying proportion of internal combustion engine exhaust gas and clean ambient air whose mass sum is constant. The temperature of this mixture varies over a large range on the inlet end but must be constant within a tolerance on the outlet end of the heat exchanger. The gas flow pressure drop must be low, ideally less than 3 inches water, and constant. Since the mass of a gas is a function of the pressure times the volume divided. by the temperature, and a pump maintains a constant volume, pressure divided by temperature must be held constant by the heat exchanger.

The present heat exchanger controls gas temperatures in two ways. First, the heat exchanger acts as a heat sink. Secondly, gas temperature is controlled by controlling fin temperature to regulate gas temperature with a controlled coolant temperature.

The inlet gases are mixed by an internal header adjacent the inlet which acts as a mixing surface for the inlet gases. Further, the fins of the heat exchanger split gas into radially flowing discs which are blended back into a flowing column and alternately, a flowing annulus. The design of the heat exchanger interior is symmetrical so all these mixing functions are concentric and symmetrical about the axis of the heat exchanger thus assuring homogeneity.

A further advantage of the present invention is its capability to reduce noise propagated through the inlet ducting by a positive displacement gas pump coupled to the heat exchanger outlet. The particular fin configuration in the heat exchanger interior prevents line of sight noise propagation and provides volume changes which reflect noise pressure waves.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic block diagram illustrating the present heat exchanger in connection with pump means for achieving the desired constant mass flow of sampled gas.

FIG. 2 is a cross-sectional view of the heat exchanger exposing the interior components thereof.

FIG. 2A is a cross-sectional view taken along section lines 2A2A in FIG. 2.

FIG. 3 is an alternate sectional view illustrating the heat exchanger operating in a single gas pass and single coolant pass mode with reverse flow.

FIG. 4 is a cross-sectional view taken along a plane passing through section line 44 of FIG. 2.

FIG. 5 is an additional alternate embodiment of the present invention illustrating the coaxial alignment of two inlets and the outlet from the heat exchanger and a single gas pass.

FIG. 6 is still another alternate view that illustrates a reciprocal structural relationship between inlets and the outlet as shown in FIG. 5 and four gas passes to illustrate how easily the number of passes can be arranged.

DETAILED DESCRIPTION OF THE INVENTION Referring to the figures, and more particularly FIG. 1 thereof, reference numeral 10 generally indicates a constant volume sampling system. A heat exchanger 16 which constitutes the basis for the present invention,

has a first inlet 12 for delivering automobile exhaust gas to the heat exchanger 16. A second inlet 14 delivers clean air to the heat exchanger 16. The exchanger mixes and controls exit gas temperature. The temperature conditioned gas mixture exits from the heat exchanger at outlet 18. A positive displacement pump is connected to the outlet 18 through pipe 20. A parallel pipe connection 22 allows direct communication between the oulet I8 and a smaller sample pump 24 which fills a sample bag 26 at a constant mass flow rate. The sample bag 26 is then subjected to gas analysis to determine the pollution constituentsof the exhaust gas.

Referring to FIG. 2, the casing 28 of the heat exchanger 16 is shown as a cylindrical body. The casing may be fabricated from two mating parts that are held together by fasteners and a gasket (not shown). This would enable the casing to be opened rapidly for easy cleaning, while the inlet and outlet tubes remained connected to ducting. The casing serves to protect the fins located in the interior thereof. The casing also serves as the outer duct. The ability to open the casing also permits baffles discussed hereinafter to be moved thereby altering the flow path of gas flowing through the exchanger. The inlet of the casing is indicated by 30 and a first inlet pipe 32 is seen to communicate directly with the inlet opening 30. The first inlet pipe 32 carries clean air. A second inlet tube 36 is positioned concentrically inwardly of the tube 32. Both inlet tubes are concentric with the axis of the cylindrical casing 28. The inner opened end 38 of the inlet tube 36 provides entrance for hot automotive emission exhaust gas. As will be noticed, the inner end 38 of this tube extends inwardly of the inlet opening 30 and as exhaust gas is delivered through the tube opening 38 it becomes mixed with the air delivered through the tube 32. As

mentioned in the previous discussion, through mixing of these gases is extremely important to produce desired homogeneity of air and exhaust gas.

An annular cylindrical fin assembly 40 is concentri- 5 cally mounted within the casing 28. A resulting axial passageway 42 extends along the length of the fin assembly 40. At the left end of the fin assembly is a coolant header 44 which is disc shaped and like the fin assembly 40 is axially disposed within the casing 28. The

1O header 44 connects the left ends of coolant pipes that run through the fin assembly 40. A second coolant header is shown at 46. This header differs from coolant header 44 in that it is divided into two concentric annuluses by a ring-shaped baffle 49. The inner annulus distributes the coolant, entering the heat exchanger among the inner set of tubes, and flows to the left. The outer annulus collects the coolant flowing to the right through the outer set of tubes. Coolant flows out of the heat exchanger from the outer annulus. The fin assembly 40 is positioned in the location shown by annular baffles or

spacers

48 and 50. In addition to supporting the fin assembly in the illustrated position, the baffles govern the path of the gas mixture flowing through the fin assembly 40. By making the baffle 48 slideably adustable, variations in the flow path can be created.

Referring to FIGS. 3 and 4, the fin assembly 40 is seen to include a plurality of annular shaped fins 52 that are positioned in longitudinally spaced relationship with respect to a central axis. The fins 52 are parallel to each other and spaced sufficiently to resist clogging. Coolant tubes such as 54 run through the fins 52 thereby effecting heat exchange between the hotter gases flowing around the exterior surfaces of the fins and the cooler coolant fluid running through the tubes 54. The individual fins 52 may be arranged in a helical orientation rather than the illustrated orientation. Referring once again to FIG. 2, coolant liquid flows into coolant tube 56 and after traversing the length of the fin assembly 40, the coolant is reversed at the head 44 and executes a reverse flow to header 46 and then out through coolant tube 58. It should be noted that the coolant header 46 is separated into inner and outer chamber so that they may respectively function for coolant inlet and

coolant outlet tubes

56 and 58. Thus the coolant flow is at all points symmetrical about the axis. The coolant tubes may be arranged so that multiple passes through the fins occur. In a preferred embodiment, a high flow rate of the liquid occurs commensurate with a low pressure drop thereby reducing required pumping power.

As mentioned in the previous text, the coolant header 44 confronts the inlet of tubes 32 and 36 with a surface against which the inlet gases can impinge. By so impinging, the gases mix further and increase homogeneity. After this mixing, the gas mixture flows radially outwardly along the left passageway 61 where the air flow from tube 32 shears the flow in passageway 61 to again increase the mixing effect. As will be noted in the figure, the flow path is symmetrical about the axis at all points between the inlet and outlet of the heat exchanger. The gas mixture then passes through a second passageway 62 defined between the interior wall of the casing 28 and the exterior surface of the fin assembly 40. It will be remembered that a positive displacement pump is connected to the heat exchanger outlet so that a continuous flow is insured between the inlet and outlet.

As shown in FIG. 2, the gas mixture then flows radially inwardly through the individual fins of the fin assembly 40. The gas mixture contained between adjacent fins can be visualized as an annular disc. As the gas mixture flows through the fins, heat exchange is effected as well as additional mixing of the original exhaust gas and air components. The first section of the fin assembly 40 through which the gas mixture passes is generally indicated by reference numeral 64. After the gas passes through this fin assembly section 64 it collects in and flows throughthe axial passageway 42 where additional mixing is accomplished. The baffle 48 defines the section 64 and prevents the gas mixture from flowing into an adjacent section 66 of the fin assembly prior to having traversed the passageway 42. After the gas mixture flows radially outwardly through the fin section 66 it collects in a second annular cylindrical passageway 68 that further directs the gas mixture in a longitudinal direction. The baffle 50 restrains the longitudinal flow through the passageway 68 and forces the gas mixture to continue its flow through a final fin assembly section 70. After passage through the fin assembly section 70 where the gas is mixed further, the gas mixture collects in an axial passageway 74 that is adjacent the passageway 42 and separated therefrom 'by an axial baffle 72. The final temperature conditioned gas mixture flows through the axial opening 74 into an end passageway '76 bounded between the right end of the casing 28 and the confronting surfaces of coolant headers 46, 59 and the baffle 50.

The resulting radial flow path expands and contracts which alternately rarifies and compresses, accelerates and decelerates the flowing gas in such a way as to dampen other pressure and velocity cycles, including sound waves generated by associated machinery.

An outlet tube 78 is connected to the casing 28 and communicates directly with the passageway 76. The inlet tubes 32, 36 and the outlet tube 78 may be installed in a length of straight ducting by removing a length of duct equal to the length of the heat exchanger and substituting the exchanger for the duct section. A poppet valve assembly 80 is positioned at the inward end of the outlet tube 78 to control outlet flow. The poppet valve augments gas mixing by generating turbulence and directional changes within the gas stream yet does not generate density strata in downstream ducting. Specific utilization of this valve will be explained hereinafter. However, as will be noticed, the embodiment illustrated in FIG. 2 presents the gas mixture with three passes through the fin assembly 28 where the inlet gases are cooled and mixed. In addition, passageways or plenums present themselves alternately between the passes, by the gas mixture, through the fin assembly 28. Further mixing in these passageways occurs.

Thus, far, it should be appreciated that the described embodiment of FIG. 2 exhibits a symmetrical flow pattern which maintains thermal and physical symmetry that improves flow distribution and augments heat transfer and gas mix homogeneity. This symmetry also results in a zero strat discharge gas flow that is suitable for sampling and analysis. Although the previous discussion referred to the liquid as a coolant, this need not be so. The temperature of the gas exiting from the heat exchanger is controlled by the fin and coolant tube temperature which in turn is maintained by liquid flowing through the tubes. This liquid may be hotter or The valve assembly includes a poppet valve head 82 that cooperates with the valve seat 84. The seat is formed in the left end of the outlet tube 78. An elongated valve stem 86 is axially disposed along the length of the outlet tube 78 and has threads 88 formed along an intermediate portion thereof. A mating threaded sleeve 90 supports the valve stem 86 in its illustrated position, the sleeve 90 being itself secured to the outlet tube 78 by welding (92) or the like. A first 0 ring 94 is located at the left end of the sleeve 90 and serves to protect the interior threads from corrosive constituents of the exhaust gas. A second 0 ring 96 is located at the opposite end of the sleeve 90 to achieve the same result. It is to be emphasized that other means may be employed to mount the poppet valve member 82 in its illustrated position. However, for purposes of clarity and brevity, the valve mounting members have been explained as set forth above. In order to adjust the seating of the poppet valve member 82, a driven gear 98 cooperates with a mating driving gear 100 that is in turn driven by motor 102. By energizing motor 102, rotational motion of the

gears

98 and 100 is translated to axial displacement of the poppet member 82.

As illustrated in the figure, the outlet tube 78 extends to a right angle elbow portion 104 which terminates at a positive displacement pump (not shown) which draws the gas mixture through the heat exchanger.

The poppet valve assembly 80 is primarily utilized during calibration of the sampling system shown in FIG. 1. During calibration, pressure differential of the displacement pump versus volume displaced by the pump per revolution of a pump cycle is plotted over a range of valve positions. This is repeated during a second calibration cycle and if repeatability is good and the plot compares favorably with a predetermined standard plot, the system is operating satisfactorily.

FIG. 3 illustrates an alternate embodiment of the present invention wherein baffles are not used along an intermediate length of the fin assembly 40. This produces a single pass of gas mixture through the fin assembly 40, as illustrated. The disposition of an axial baffle or header plate 106 immediately inwardly of the inlet causes mixing of the gas components introduced at the inlet, as previously described. A plenum or passageway 108 directs the gas mixture radially outwardly where additional mixing takes place. Asecond path direction of the gas mixture is the annular cylindrical passageway or plenum 110. From this passageway, the gas mixture flows radially inwardly through the fins 52 of the fin assembly 40 during which time the gas mixture undergoes heat exchange and additional mixing. Finally, the gas mixture collects and flows axially through the central passageway 114 which communicates directly with the outlet of the heat exchanger. An annular baffle 112 at the right end of the fin assembly 40 restricts the longitudinal flow of the gas mixture. As clearly shown in FIG. 4, a number of spaced coolant tubes 54 pass through the individual fins 52 of the fin assembly 40. This is to achieve the most efficient and even heat transfer.

FIG. 5 shows an alternate embodiment of the present invention. In this embodiment, the outlet tube is positioned at the same end of the heat exchanger as the inlet tubes. To add clarity to this figure, header details and coolant pipes have not been shown.

More specifically, a cylindrical casing 116 is provided with an interiorly disposed annular fin assembly 118 of the type previously discussed. An outlet opening 120 is formed in the left end of the casing 116. An elbow shaped outlet tube 122 communicates directly with the inlet opening 120. The opposite end of this tube is connected to a positive displacement pump which forces the temperature conditioned gas mixture through the heat exchanger. A second tube 124, which serves as an inlet tube, is positioned in inward concentric relation to the tube 122. The tube 124 is connected to the left end of the fin assembly 118 at point 128. An opposite end of the tube 124 passes outwardly at 126 through the elbow tube 122. This second tube 124 carries clean air to be mixed with exhaust gas that is delivered to the heat exchanger by a third inlet tube 130. This latter mentioned tube is concentrically disposed within the air inlet tube 124. The inward end of tube 130 is offset from the left end of fin assembly 118, and as a result, the air flow shears through the exhaust gas flow, at the inlet plenum 132 thereby mixing the gases. After this initial mixing of the gases, the mixture travels through the axially located passageway 134. By applying displacement pressure at the outlet tube 122, the gas mixture is drawn through the fin assembly 118. As the gas passes through the axial passageway 134, additional mixing is obtained. Still further mixing is obtained as the gases pass through the individual fins of the fin assembly 118. In addition, as previously explained, as the gas mixture passes through the fin assembly heat exchanger is effected. The gas mixture collects in the axial cyclindrical plenum or passageway 134 where once again mixing occurs. Finally, the gas mixture flows to the opening 120 where the mixture is delivered to the interior 136 of the outlet tube 122.

Reference numerals

137 and 138 indicate inlet and outlet headers. Seals at 127 and 131 permits the removal of the casing 116 without disturbing ducts and plumbing. Thus, access is provided to the gas and liquid passages for cleaning purposes. A V-band clamp 129 retains the seal 129 in place.

FIG. 6 illustrates an additional embodiment which is somewhat similar to the embodiment of FIG. but represents a reciprocal arrangement of inlet and outlet tubes.

Again, a cylindrical casing 140 surrounds an inwardly disposed cylindrical annular fin assembly 142. Annular baffles 144 and 146 support the fin assembly 142 in its illustrated position as well as defining the path through which the gas mixture is to flow. A large inlet opening 148 is formed in the left end of the casing 140. An elbow shaped inlet tube 150 communicates directly with the opening 148. The inlet tube 150 provides for the delivery of filtered air to the heat exchanger. A concentric and radially inward tube 152 has its inward end coplanar with the inlet opening 148. An intermediate length of the tube 152 passes outwardly through the elbow of the inlet tube 150. Thetube 152 carries exhaust gas to the heat exchanger. A third concentric tube 156 is positioned radially inwardly of the second mentioned tube 152. As in the case of tube 152, the tube 156 passes outwardly through the elbow portion 154 of the inlet tube 150 while the inward end of the tube 156 is attached to the left end of the fin assembly 142. The tube 156 is outwardly connected to a positive displacement pump for drawing the gas mixture introduced at the heat exchanger inlet through the length of the exchanger.

In operation of the embodiment shown in FIG. 6, exhaust gas flowing through tube 152 is indicated at 162. Filtered air delivered by the inlet tube shears the flow of the exhaust gas and produces mixing of the air and exhaust gases. The coolant header surface 164 presents a mixing surface as previously discussed in connection with FIG. 2 which causes further mixing of the gases. In order to add clarity to FIG. 6, the header details and coolant tubes have been left out of the figure. An initial plenum or passageway 166 is created to cause the gas mixture to flow radially outwardly to the annular cylindrical passageway 168 which directs the gas mixture flow to a first section of the fin assembly 142. After the gas mixture has passed through this fin assembly section, it is collected in the axial passageway 170. As in the previously discussed embodiments, the gas mixture undergoes heat exchange as the mixture passes through the fin assembly section. Additional mixing occurs in the axial passageway 170 and by virtue of an annular axially positioned baffle 176 the mixture is redirected through the fin assembly 142, through a second section thereof, until the gas collects in a second passageway or plenum 172. Additional mixing occurs and from this passageway the gas flow is redirected once again through the fin assembly 142, through a third section thereof. The placement of baffle 146 inwardly from the right end of the fin assembly causes the gas mixture that has collected in the axial passageway 174 to flow once again through the fin assembly 142, through a fourth section thereof. Finally, the gas mixture traverses the plenum 178 and returns through the axial opening 180 to the outlet tube 156. Thus, the embodiment shown in FIG. 6 effects four passes of the gas mixture through the fin assembly.

In each embodiment, the heat exchanger casing is designed to allow simple removal so that the fin assembly and other interior components may be cleaned and inspected. Deep drawn stampings make light casings which contribute to compact outside dimensions for a given fin assembly heat transfer surface. The radial flow at the ends of the casing eliminates the need for large distribution plenums. Therefore, not only is the heat exchanger compact, but its installation is compact as well. The casing, fins, and coolant tubes can be made of any material desired so that the exchanger can be subjected to extreme temperatures and chemicals. Once again, it is reiterated that the invention contemplates the ability to add or remove baffles so that the number of passes by a temperature conditioned gas mixture can be altered after the heat exchanger is built. This ability is an advantage many heat exchangers lack.

All passes of the mixtured gas are symmetrical because the heat exchanger is cylindrical. Flow is alternately axial and radial but always symmetrical about the center line of the heat exchanger. The symmetrical flow improves flow distribution which augments heat transfer and gas mix homogeneity.

The coolant flow path for a particular embodiment is not restrictive. Thus, coolant flow may be reversed from the directions shown, such as in FIG. 2. The coolant tubes may be manifolded with tube fittings, fed from headers as shown, or may form a series flow path. The fin structure may be varied so that it includes a serpentine" arrangement of fin tubes which may be wrapped in any-convenient manner to form the fin assembly.

By having the flow as constituting an alternate series of radial and axial directions, the line of sight transmission of noise from the displacement pump is blocked.

Although the figures have been discussed in terms of multiple inlet gases, it is essential to note that the heat exchanger embodiments shown will also achieve superior heat exchange with a single inlet gas.

It should be understood that the invention is not limited to the exact details of construction shown and described herein for obvious modifications will occur to persons skilled in the art.

Wherefore, we claim the following:

1. A heat exchanger having a housing and comprismg:

a heat exchanger fin assembly symmetrically mounted in the housing, the fin assembly including an annular cylindrical body comprisedof axially spaced fin members, the assembly being radially spaced from the housing;

inlet means having a plurality of concentric inlet tubes connected to the exchanger for delivering respective fluids to the exchanger, simultaneous entry of the fluids causing turbulent mixing of the fluids to occur;

a first axial passageway formed between the fin assembly and the housing to alternately direct the flow of mixed fluids radially and axially between the inlet means and an outlet means;

a second axial passageway being formed along the axis of the fin assembly; the fluid mixture alternately flowing between the first axial passageway, the annular space between the individual fin members, and the second axial passageway;

coolant means connected to the fin assembly for effecting desired heat transfer between the fin assembly and the fluid mixture, resulting in temperature conditioning of the fluid mixture which is homogeneous when delivered to the outlet means;

at least one annular baffle to block the first axial passageway at a preselected point therealong; and

at least one baffle disposed at a preselected point along the second axial passageway;

the presence of the annular and axial baffles forcing the fluid flow to make several passes through the fin assembly between the inlet and outlet means thereby increasing the temperature conditioning of the fluids and the homogeneity thereof.

2. The structure of claim 1 wherein the coolant means further include at least one header for manifolding a plurality of coolant tubes passing through the fin members, the header having a mixing surface adjacent the inlet tubes against which the inlet fluids impinge.

3. The structure of claim 1 wherein at least one preselected baffle is removably mounted within the exchanger.

4. The structure of claim 1 wherein an adjustable number of baffles are located within the exchanger, the

number of baffles commensurately changing the number of passes across the fins.

5. The subject matter of claim 1 wherein the outlet means includes:

a plenum; and valve means interposed between the plenum and an outlet pipe for symmetrically throttling the gas flow through the exchanger and for generating turbulence in the gases as they pass across the valve thereby enhancing mixing of the gases. 6. The subject matter of claim 1 wherein the inlet means includes an inlet plenum for receiving inlet gases and further wherein the header is aligned with the plenum for causing impingement of the inlet gases thereagainst thus redirecting the inlet gases through the exchanger in a turbulent manner to enhance the mixing of the gases.

Claims

1. A heat exchanger having a housing and comprising: a heat exchanger fin assembly symmetrically mounted in the housing, the fin assembly including an annular cylindrical body comprised of axially spaced fin members, the assembly being radially spaced from the housing; inlet means having a plurality of concentric inlet tubes connected to the exchanger for delivering respective fluids to the exchanger, simultaneous entry of the fluids causing turbulent mixing of the fluids to occur; a first axial passageway formed between the fin assembly and the housing to alternately direct the flow of mixed fluids radially and axially between the inlet means and an outlet means; a second axial passageway being formed along the axis of the fin assembly; the fluid mixture alternately flowing between the first axial passageway, the annular space between the individual fin members, and the second axial passageway; coolant means connected to the fin assembly for effecting desired heat transfer between the fin assembly and the fluid mixture, resulting in temperature conditioning of the fluid mixture which is homogeneous when delivered to the outlet means; at least one annular baffle to block the first axial passageway at a preselected point therealong; and at least one baffle disposed at a preselected point along the second axial passageway; the presence of the annular and axial baffles forcing the fluid flow to make several passes through the fin assembly between the inlet and outlet means thereby increasing the temperature conditioning of the fluids and the homogeneity thereof.

4. The structure of claim 1 wherein an adjustable number of baffles are located within the exchanger, the number of baffles commensurately changing the number of passes across the fins.

5. The subject matter of claim 1 wherein the outlet means includes: a plenum; and valve means interposed between the plenum and an outlet pipe for symmetrically throttling the gas flow through the exchanger and for generating turbulence in the gases as they pass across the valve thereby enhancing mixing of the gases.

6. The subject matter of claim 1 wherein the inlet means includes an inlet plenum for receiving inlet gases and further wherein the header is aligned with the plenum for causing impingement of the inlet gases thereagainst thus redirecting the inlet gases through the exchanger in a turbulent manner to enhance the mixing of the gases.