TUBE HEAT EXCHANGER AND A METHOD OF PRODUCTION OF ITS HEAT EXCHANGING ELEMENTS

Abstract: Tube heat exchanger provided with heat exchanging surface formed by uniform slender helical heat exchanging tubes (1) that are oriented in tube plates equally or alternately in two azimuths forming an angle (G) lower than 180 DEG and having their contour diameter (DE) greater than their pitch (T) in tube plates. Therefore, in case of the corresponding helix led in the heat exchanging surface numerous uniformly situated contact spots are formed.

Description: Tube Heat Exchanger and a Method of Production of its Heat Exchanging Elements Field of the Invention The invention relates to a heat exchanging apparatus sub¬ stantially consisting of a tube heat exchanging surface, tube plates, a shell, usually of the cylindrical shape, bottoms at the ends and the appropriate input and output nozzles situated in the bottoms and in the shell. State of the Art The already disclosed tube heat exchangers are provided with a heat exchanging surface made most often from straight heat exchanging tubes, eventually from traditional helically wound tubes situated alternately in right-handed and left-handed coaxial cylindrical layers. The heat exchanging tubes having their ends fastened in the tube plates are mounted in the support and distance design elements that may be considered from the hydraulic and thermal points of view as passive elements. The existence of such elements as well as of the simultaneously used various hydraulic partitions in the most commonly used heat exchangers with straight heat exchanging tubes is a design, production and operational disadvantage of the existing tube heat exchangers. Summary of the Invention The above mentioned disadvantage of the disclosed technical solutions is removed by the presented invention which is SUBSTITUTESHEET ISA/EP based on a new geometry ' of the heat exchanging elements an which consists substantially in that the heat exchangin surface of the heat exchanger is formed by slende right-handed and/or left-handed helical heat exchangin tubes that are preferably identical. The tubes are oriente in the tube plates equally or alternately and ar mutually turned a little bit. It is preferable if the eve or odd tubes are turned by the same angle that is belo 180°. At the same time their external or contour diameter i bigger than their pitch in the tube plates. Thereby, i case of the appropriate helix lead numerous uniformly space contact spots are established in the heat exchanging surfac and significant hydraulic and heat exchanging intensifica tion effects are observed. The frequency of the contac points and the magnitude of the intensification effects ar proportional also to the spatial curvature of the helica heat exchanging tubes. Progressiveness of the presented tube heat exchanger desig is given by its main advantages. The new heat exchangin surface is self-supporting, eliminates the vibration possi bility of the individual heat exchanging tubes. Thereby their service life and reliability of their attachment t the tube plates with regard to the long-time tightness ar increased. Therefore, the heat exchanging surface can b very thin-walled what contributes together with the signi ficant heat transfer intensification to a substantia increase in the specific heat transfer capacity. The helica heat exchanging tubes have both very good self-compensatin properties and substantially shorter design length at th same "thermal" length that is roughly equal to the length o the straight tube used for manufacture. The square patter SUBSTITUTE SHEET ISA/EP of holes in the tube plates makes possible that each dimen¬ sional type of the helical heat exchanging tubes can for differently compact heat exchanging surfaces. E. g. a mer slight turning of all even or "second" helical heat exchan¬ ging tubes in the tube plates makes possible to change th pitch of the square pattern in a large extent given by th geometric parameters of the respective helical heat exchan ging tube. Apart from the tubes of the classical helical geometry it is also possible to use the quasi-helical tubes for some modified designs of the heat exchanging surface. Such tubes consist of straight and plane bends sections positioned alternately. The quasi-helical heat exchanging tube of square contour is suitable for low pressure heat exchangers with rectangula or squarish cross section of the shell. A consequence of the intensifying effects and the design advantages is that the new tube heat exchanger is smaller, lighter and cheaper tha the existing tube heat exchanger. Secondary but also valu¬ able advantages are savings of the floor surface and con¬ struction space for installation of such smaller and lighter heat exchanging apparatuses. Besides, the presented design of the heat exchanging surface is highly compatible with the progressive design of the tube heat exchangers with th doubled tube plates and the two-wall heat exchanging tubes. Owing to the substantially increased turbulence outside an inside the helical heat exchanging tubes caused by their bi spacial curvature, fouling of the heat exchanging surface by impurities of the operational heat transferring media will be decreased. The increased effectiveness of the hea SUBSTITUTESHEET ISA/EP transfer positively effeόts the thermal effectiveness of th circuits or systems where this tube heat exchanger will b installed. This fact means also the corresponding fue savings. Owing to the all-welded construction this hea exchanging apparatus finds application also in the fields o the medium and high temperatures and/or pressures and thi also in case of the phase transitions of the heat transfe media. A design, assembly and operational advantage is th possibility to assembly big heat exchanging apparatuses fro the pre-fabricated unified modules. The new heat exchangin surface is very suitable for such apparatuses. The new geometry of the heat exchanging elements require also new methods of their production. The methods depend o the required slenderness of the helical heat exchangin tubes that can be defined here only by the ratio between th contour diameter of the manufactured helix and the externa diameter of the applied straight tube. The optimal slender ness is in the range from 2 to 5. The helical heat exchan ging tubes having different slenderness are less suitable o inapplicable. The method of production of the very slende helical heat exchanging tubes having the slenderness equa or near to 2 consists in principle in twisting at best tw or three tubes simultaneously in their full length. In cas of production of less slender helical heat exchanging tube it is suitable to wind the tube on a thin bar and sub sequently axially stretch the formed helix to diminish it contour diameter i.e. to increase its slenderness. SUBSTITUTE SHEET ISA/ EP Explanation to the Drawings It is characteristic for the present invention that i offers a wide variety of design modifications. The inventio is further explained in greater detail by means of th attached drawing where the Figure 1 shows a small section o the compact heat exchanging surface formed only b right-handed helical heat exchanging tubes and the Figur 2 shows schematically a section of the hybrid heat exchan ging surface formed by combined heat exchanging tubes. Examples Illustrating the Invention The compact heat exchanging surface according to Figure 1 i as an example formed by right-handed heat exchanging tube 1 . oriented uniformly azimuthally in the holes of the tub plates situated near above and deep below to the depicte horizontal cross section. The helical heat exchangin tubes 1. have external diameter D = 20 mm, wall thicknes S = 1 mm and contour diameter of the helix D E = 60 mm wha corresponds to the slenderness equal to number 3. The tube are spaced in the tightest possible square pattern wha means that the minimal pitch is T = 29 mm. The pitch i evidently determined also by the led of the helix, not show in this figure, which is in this example 120 mm. The rati D : T is the sine of the central helix angle having diamete D s . The pitch between holes in the tube plates is M = 9 mm Each helical heat exchanging tube 1 . with the exception o the peripheral ones touches in each coil in two spots eac of the four adjacent helical heat exchanging tubes 1. Iden tical turning of all even or "second" helical heat exchan SUBSTITUTE SHEET ISA/EP ging tubes 1 , in the holes of the tube plates to the dire tion as shown by the arched arrow G pointing to the rig can make any looser square patterns up to the maximum pit T = D E = 60 mm. By any turning G without axial movement t two-spot contacts of each coil of the helical heat excha ging tubes 1. change into one-spot ones. Thereby, the tot amount of the contact spots in the heat exchanging surfa diminish to a half, whereby, the uniformity of their spaci is maintained. A hybrid heat exchanging surface according to the schemat Figure 2 showing partial longitudinal section is formed fr uniform combined heat exchanging tubes 3_> τtιe tubes a fastened in the tube plates 2 alternately always on t opposite side in a square pattern. The combined heat excha ging tubes 3_ have helical about one half of the total desi length and the other half is straight. A geometric conditi of the realization of such hybrid heat exchanging surface to fulfil two trivial relations: D E = D + 2M and T = D + The characteristic dimensions are marked identically both the Figure 1 and the Figure 2. H in the Figure 2 means t led of the helix. Another and likely the most important example of the embod ment of the invention, which is however not shown as it very similar to that in the Figure 1, is the design with t same helical heat exchanging tubes with the exception th they are oriented identically in the holes of the tube pla spaced in a triangular pattern corresponding to the minim pitch. Such design makes possible to make the most compa heat exchanging surfaces of the homogenous helical conce tion. SUBSTITUTE SHEET ISA/EP Industrial Application Progressiveness of the design according to the presen invention predetermined by its above specified advantages is a guarantee of the future broad application of this hea exchanging apparatus in the most various heat transferrin circles and heat energy systems. An example of it can be th heat pumps and the refrigerating equipment, the centralize heat supplying systems, the system of industrial and housing air conditioning, the classical and atomic power stations of all designs, the chemical and food industries. Further applications may be found in the heat controlling parts of various ecological projects and energy saving programs. As a specific attractive application case from the atomic electric power industry the once-through flow stea generator with slightly superheated steam can be named which can be used in the advanced pressure-water nuclear power plants. In the classical electric power industry the apparatus according to the invention can be used in the feed water recovery systems, in the steam-gas cycles in the utilization of waste heat from industrial ovens, from offgas of the gas turbines and the piston gas engines as well as from the supercharged Diesel engines of big or medium output. In the chemical industry it can be utilized also in all technological processes that require output or input of heat to or from apparatuses where exothermic or endothermic chemical reactions are carried out. SUBSTITUTESHEET ISA/EP

Claims: C l a i m s 1. Tube heat exchanger substantially consisting of a tube heat exchanging surface, tube plates, a shell usually of longitudinal shape, end bottoms and of the appropri¬ ate input and output nozzles in the bottoms and/or the shell, characterized in that its heat exchanging surface is formed by slender right-handed and/or left-handed helical heat exchanging tubes (1) that are oriented in the tube plates equally or alternately and are mutually turned a little bit whereby their external or contour diameter (D E ) is bigger then their pitch (T) in the tube plates (2) to form substantially uniformly placed contact spots in the heat exchanging surface. 2. Tube heat exchanger according to claim 1 characterized in that the heat exchanging surface is formed by uniform slender right-handed or left-handed helical heat exchanging tubes. 3. Tube heat exchanger according to claim 1 characterized in that the heat exchanging surface is formed substan¬ tially of uniform quasi-helical tubes consisting of straight sections and spatially a little bit uniformly turned plane bends placed alternately against each other. 4. Tube heat exchanger according to claims 1, 2 or 3 characterized in that the even or odd tubes (1) of the heat exchanging surface are turned by the same angle that is lower than 180°. SUBSTITUTE SHEET ISA/EP 5. Tube heat exchanger according to point 1, 2 or 3 characterized in that the shell of the tube exchanger is of cylindrical shape. 6. Method of production of very slender helical heat exchanging tubes from straight tubes characterized in that - the tubes are prepared by a known process for bending and thereafter - at least a pair of tubes is fixed in opposite clamping elements, - by turning one clamping element the tubes are symmet¬ rically bent, thereafter - the groups of tubes are separated by unwinding and their ends are finally shaped according to require¬ ments or at least one straight tube is wound on a rod having diameter maximally three-times greater than as is the diameter of the tube and after releasing and removal from the rod the tube is axially stretched to the desired dimensions, whereby - the bent tubes are further shaped according to needs. 7. Method of production according to claim 6 characterized in that the tubes are turned or wound in groups of two or three at once. 8. Method of production according to claim 6 or 7 characterized in that during turning the tubes are clamped at end into a firm or turning clamp and the other end is clamped into a moving clamp which is turnable in case the first clamp is firm . SUBSTITUTESHEET ISA/EP Abstract Title of the Invention: Tube Heat Exchanger and a Method of its Heat Exchangin Elements Production The presented tube heat exchanger is provided with hea exchanging surface formed by uniform slender helical hea exchanging tubes (1) that are oriented in tube plate equally or alternately in two azimuths forming an angle (G lower then 180°. Their contour diameter (D E ) is greater the their pitch (T) in tube plates. Therefore, in case of th corresponding helix led in the heat exchanging surfac numerous uniformly situated contact spots are formed. There fore, the new heat exchanging surface is self-supported prevents vibrations of individual elements, has greate service life, provides substantially increased specific hea output, is less fouling by impurities from the media an makes realization of a number of design modification including the high compact ones possible. The respectiv heat exchangers are smaller, lighter and therefore als cheaper in comparison to the traditional tube hea exchangers. An alternative advantage consists in th possibility to transfer heat at lower temperature differenc what leads to the increase of thermal effectiveness in th relevant thermal circle and to the corresponding fue savings. The industrial application possibilities ar enormously broad as it concerns also thermal circles o energy producing systems operating at high temperature Oand/or pressures of heat transfer media where also pha SUBSTITUTE SHEET ISA/EP transition can be observed, i.e. vaporization or condens tion. Above all the application field is the classical a atomic energy production, metallurgy, the chemical and fo industries and the parts concerning heat technology various ecological projects and the energy saving ener producing programs. SUBSTITUTE SHEET ISA/EP

Inventors: S KORA DALIBOR, S KOROVA ILONA, S¦KORA, DALIBOR, S¦KOROVA, ILONA
Applicants: KORA DALIBOR S, KOROVA ILONA S, PLUTO, S¦KORA, DALIBOR, S¦KOROVA, ILONA
Application year: 1993
Main classification: F28D7
IPC codes: B21D53, F28D7