US 2587720 A
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March 1952 H. FRITZBERG ,7
HEAT EXCHANGE DEVICE Filed March 11, 1946 2 SHEETS-SHEET l Will Rw l N VEN TOR.
Match 4, 1952 H. FRITZBERG 2,587,720
HEAT EXCHANGE DEVICE Filed March 11, 1946 2 SHEETS-SHEET 2 Patented Mar. 4, 19 52 UNITED STATES PATENT OFFICE HEAT EXCHANGE DEVICE Lawrence H. Fritzberg, Minneapolis, Minn.
Application March 11,1946, Serial N 0. 653,564
This invention relates to heat exchangers and particularly to such devices as are used in heating, ventilating and air conditioning systems.
In conventional heat exchange devices they are provided with tubes arranged in a number of rows running parallel from one side of the exchanger to the other with the ends of the tubes connected to a common supply header and a common condensate return. It has been found that where the tubes make a single pass across the unidirectional air flow area there is an unequal heat transfer load, the transfer being greatest where the air enters the heat exchanger and becoming progressively less as the outlet side of the exchanger is approached. This unequal heat transfer loading between rows of tubes from the approach to the outlet side of the exchanger permits the steam to flow more quickly through the more lightly loaded tubes, and the steam flowing through these latter tubes reaches the return header more quickly than that flowing through the more heavily loaded tubes. Steam in the return header then enters the return ends of the more heavily loaded tubes, thereby producing an improper condition of balance of flow through the tubes. Steam backflowing from the return header to the more heavily loaded tubes lowers their heat transfer efiiciency by hindering the drainage of condensate and the enective removal of noncondensable gases until finally there is a condition of pronounced ineffective areas in that portion of the heat exchanger having more heavily loaded tubes. Furthermore, expansion and contraction strains will be set up by the unequal transfer loading on the difierent rows of tubes. These difficulties are not overcome by the use of difierent orifice restriction in the steam inlet ends of the tubes, particularly where the tubes are long, and they also cause a considerable drop in the steam pressure.
It is a general object of the invention to provide a construction, wherein the heat transfer load is substantially balanced throughout all of the tubes of a heat exchange unit.
Another object of the invention is to provide a construction whichwill control and reduce the internal pressure drop in each row of tubes, and for improving the removal of noncondensable as well as better drainage of condensate.
A further object of the, invention is to provide a construction which will reduce expansion and contraction strains in a heat exchange unit.
The above and other objects and advantages of the invention will more fully appear from the following description made in connection with the accompanying drawings, wherein like reference characters refer to the same parts throughout the views, and, in which:
Figure 1 is a sectional view taken on the. line II of Figure 2;
Figure 2 is a side elevational view of the embodiment of the invention;
Figure 3 is a sectional View similar to Figure l but of another embodiment of the invention;
Figure 4 is a front elevational view of another embodiment;
Figure 5 is a view of the structure in Figure 4;
Figure 6 is a section taken approximately 0-11 the line 6-6 of Figure 4 Figure 7 is a top plan view of still another form of device; and
Figure 8 is an enlarged section taken approximately on the line 8--8 of Figure '7.
In Figures 1 and 2 there is shown an intake or supply header I0 and a return or exhaust header II. Steam is supplied to the header I0 through an intake connection I2 and condensate is carried oif through an outlet connection I3.
Extending between the headers I0 and II are heat exchange tubes I 4 and I5, these being shown alternating in the unit from top to bottom. Preferably the tubes are provided with heat radiating =fins I6.
As indicated by the arrows in Figure 1 the near side of the heat exchange unit may be considered an air inlet side I5a for air passing through the unit and around and between the tubes I4 and I5. The other side I5b, of course, is the air outlet for the purpose of illustration, although it is to be 'understood that air may be passed through the heat exchange unit in either direction. The tube .I4 is shown with its inlet end located at the rear or outlet side of the heat exchange unit. The tube I4 is provided with an offset bend I1, and the right hand portion of the tube I4 is shown lying at the near or inlet side of the heat exchange unit.
Following the same idea, the left hand inlet of the tube I5 lies at the near or inlet side of the unit and at its central portion the tube crosses tube I4 in a rearward direction, and the right hand end of the tube I 5 lies at the rear or outlet side of the heat exchange unit. Consequently, each of the tubes I4 and each of the tubes I5 has portions which are acted on equally by the external heat exchange medium or flow of air through the unit. Neither tube has its entire length subjected to the same heat transfer conditions throughout and they are balanced in such a way that condensation in each tube is the same as that in all of the others.
In Figure 3 there is shown another construction for carrying out the invention. There is illustrated an intake header i8 and an exhaust or return header Hi. There is also shown a pair of tubes 20 and El which cross each other so that each has a section at the air inlet side of the unit and a section at the air outlet side thereof. It will be noted, however, that the headers l8 and H! are disposed horizontally and that the outlet ends of the tubes 29 and 2i are lower than their inlet ends. This arrangement is provided to facilitate drainage of condensate from the tubes to the header l9.
Figures 4, 5 and 6 illustrate another form of the invention which shows an intake header 22 and a return or exhaust header 23. Tubes 2% and 25 are shown in a tortuous arrangement across the unit to provide a multi pass construction from top to bottom. The tube 2% has its upper portion at the air inlet side of the unit and then it crosses to the rear or outlet side of the unit. The upper portion of the tube 25 lies behind the upper portion of tube and at the air outlet side of the unit and then crosses to the front so that the lower portion of the tube 25 lies at the air inlet side.
In Figures 7 and 8 there is shown an arrangement of tubes 26, El and 28 in sets of three rather than in pairs as in the previously described embodiments. It will be readily seen in Figure '7 that each tube has a front section as related to the air intake of the unit, that it has an intermediate section and a rear section, and in this respect it is the same as in the previously described constructions.
From the foregoing description it will be seen that I have provided a heat exchange unit, wherein there is a more evenly balanced flow 01 steam or other heat exchange medium through each tube so that flow and pressure conditions are maintained more nearly equal in the tubes than is the case in a heat exchanger having two or more banks of tubes where one bank lies in front of another bank throughout the entire length ofeach tube.
It is, of course, to be understood that various changes may be made in the form, details, ar-
. unit, the second conduit having its inlet section.
rangements and proportions of the various parts without departing from the scope of my invention.
What I claim is:
In a steam unit heater adapted to conduct steam therethrough in heat exchange relation with an external heat exchange medium, a unit comprising at least a pair of conduits adapted conduct the steam, each conduithavmg an in let section, an outlet section and an intermediate section connecting the inlet and outlet sections, said unit having an inlet side and an outlet side for the external heat exchange medium which passes transversely therethrough in a substantial- 1y horizontal direction and about the conduits, each conduit extending substantially horizontally in the unit across the path of flow of the external heat exchange medium, one conduit having its inlet section at the inlet side of the unit and its outlet section at the outlet side of the at the outlet side of the unit and its outlet sec: tion at the inlet side of the unit, the intermediate section or" the secondv conduit extending across the intermediate section of the first conduit in a substantially horizontal direction across. the path of flow or" the external heat exchange medium to place its outlet section at the inlet side of the unit, the inlet section of the second conduit being placed rearwardly of the inlet section of the first conduit in the direction of flow of the external heat exchange medium, the outlet section of the first conduit being placed rearwardly of the outlet section of the second conduit in the direction of the flow of the external heat exchange medium.
LAWRENCE H. FRITZBERG.
Number Name Date 1,194,909 White Aug. 15, 1916 2,180,85 Soule Nov; 21, 1939