Heat exchanger apparatus having heat exchanger pipes and sheetmetal plates
This application is a continuation of copending U.S. patent application Ser. No. 893,394, filed on Aug. 5, 1986 now abandoned. 
    
    
     The invention relates to a heat exchanger apparatus comprising heat exchanger pipes and sheet metal plates which have bores and whose edge configuration comprises the side edges of an elongate strip and parallel base edges which cut through the strip inclinedly beside the bores, wherein the heat exchanger pipes extend through the bores whose diameter (da) comprises the outside diameter of the heat exchanger pipes and which are arranged in a rectangular grid whose longitudinal grid lines extend in parallel relationship to the side edges of the edge configuration of the plates and whose transverse grid lines extend in normal relationship to said side edges, wherein the grid lines are at constant pitches in the two mutually perpendicular grid directions, and wherein adjacent grid lines are displaced relative to each other by half the grid line pitch (s 1  /2). 
     Heat exchanger apparatuses of that kind, having sheet metal plates whose edge configuration comprises the side edges of a strip and base edges which extend parallel to each other and which cut through the rectangle inclinedly beside the bores, are known. In the known heat exchanger apparatus, the angle which each base edge includes with the longitudinal edge of the strip is given by the arc tg of the quotient of the pitch of the transverse grid lines, relative to the pitch of the longitudinal grid lines. The base edges which cut through the elongate strip inclinedly beside the bores serve in that arrangement to reduce the overall height of the heat exchanger, such height being measured perpendicularly to the base edges which cut through the strip inclinedly beside the bores. In such a heat exchanger apparatus, the displaced configuration of the heat exchanger pipes, due to the arrangement of the base edges which cut through the elongate strip inclinedly beside the bores, becomes an aligned arrangement, thereby giving a reduction in the level of thermal efficiency of the heat exchanger apparatus. 
     The object of the present invention is therefore that of providing a heat exchanger apparatus of the kind set forth in the opening part of this specification, in which a suitable selection in respect of the cut through the elongate strip can provide that the overall height of the heat exchanger apparatus is further reduced and at the same time adjacent heat exchanger pipes are not aligned with each other, in an advantageous manner. 
     In accordance with the present invention, that object is attained in that the base edge includes with the side edge of the edge configuration an angle A which is given by the following formula: ##EQU4## and that the base edge lies between the bores in a strip region whose width c is given by the following formula: ##EQU5## wherein the diameter da and the pitches are related in such a relationship that the following applies: ##EQU6## 
     By virtue of the recurring cut through the strip along the base edges, in accordance with the last-mentioned formulae, that arrangement gives the advantage that the heat exchanger pipes are not aligned with each other but are displaced relative to each other, as considered in the direction of flow to the heat exchanger apparatus. That gives a comparatively high level of thermal efficiency in the heat exchanger apparatus. A considerable advantage of the heat exchanger apparatus in accordance with the present invention is that the overall installation height thereof, over the base edge which extends at an inclined angle with respect to the edge configuration, is smaller with a corresponding level of thermal efficiency, than in a known heat exchanger apparatus of the genral kind set forth. 
     The bores in each plate may have a collar therearound, wherein the collars extend perpendicularly away from the plate and point in the same direction. With such a construction, the diameter (da) of the bores include double to wall thickness or gauge of the collar portion disposed around the bore, that is to say, it comprises the inside diameter of the bore which corresponds to the outside diameter of the heat exchanger pipe, and double the wall thickness or gauge of the collar portion. 
    
    
     Further details, features and advantages will be apparent from the following description of a heat exchanger apparatus according to the invention, as shown in the drawings in which: 
     FIG. 1 is a view in cross-section through a portion of a heat exchanger apparatus illustrating the manner in which its sheet metal plates are formed from a strip of sheet metal, 
     FIG. 2 is a view in section taken along line II--II in FIG. 1, showing only portions of a plate and a heat exchanger pipe which is mounted in the plate, and 
     FIG. 3 is a plan view of a sheet metal plate of a heat exchanger apparatus formed from the strip of sheet metal of FIG. 1. In FIG. 3 the collars of the bores are not shown. 
    
    
     Referring to FIG. 1 shown therein is a portion of an elongate band or strip from which sheet metal plates 10 are cut out. The plates 10 have bores 12. The edge configuration of each sheet-like plate 10 comprises the elongate side edges 16 which extend in parallel relationship to each other, and base edges 18 which cut through the strip inclinedly beside the bores 12. 
     As can be seen from FIG. 2, the heat exchanger pipes 20 extend through the bores 12 in the plates 10, only a portion of a heat exchanger pipe 20 being illustrated in FIG. 2. The inside diameter of the bores 12 in the plates 10 corresponds to the outside diameter of the heat exchanger pipes. The bores 12 are arranged in the plate 10 in a rectangular grid which is indicated in FIG. 1 by the dash-dotted lines 22 and 24. The longitudinal grid lines 22 and the transverse grid lines 24 have constant pitches or spacings s 2  and s 1  respectively, wherein adjacent transverse lines 24 are displaced relative to each other by half the grid pitch s 1  /2. 
     In the heat exchanger apparatus in accordance with the invention, the base edge 18 which cuts inclinedly through the strip includes with the elongate side edge 16 an angle A which is given by the following formula: ##EQU7## 
     The cut line lies within a strip-like region 26 which is illustrated in FIG. 1 by the crossed hatching and which is for example of a width C=2 mm. That width is predetermined by the width of the cutting tool which is to be used to cut through the strip. With a narrower tool, the parameter c may also be 1 mm and below. The width c is determined by the dimensions of the bores and the arrangement thereof in a rectangular grid; it is given by the formula: ##EQU8## 
     As can be clearly seen from FIG. 2, the bores 12 in the plate 10 each have a collar 28 therearound, which is produced from the material of the sheet-like plate 10 by a flanging operation. Each collar 28 projects perpendicularly away from the plate 10, all collars pointing in the same direction away from the plate 10. If the plates 10 have bores 12 with collars 28, then the diameter da of the bores 12 comprises the inside diameter of the bore 12 and double the wall thickness or gauge of the collar 28 disposed around the bore 12 (see FIG. 2). 
     In FIG. 1 reference `H` denotes the installation height of the heat exchanger apparatus in accordance with the invention; in an advantageous manner, with virtually the same number of heat exchanger pipes 12 as in a known heat exchanger apparatus, the installation height H of the heat exchanger apparatus according to the invention is smaller than the installation height of a known heat exchanger apparatus of the general kind set forth. The arrows `B` which extend in parallel juxtaposed relationship indicate the direction of flow to the heat exchanger apparatus of a fluid which undergoes exchange in respect of its energy with the fluid flowing through the heat exchanger pipes 20. 
     As can be clearly seen from FIG. 1, the flow direction B is in parallel relationship to the base edges 18 of the plate, which is oriented at least approximately horizontally in the normal position of use of the heat exchanger.