RU2039921C1 - Heat exchanger - Google Patents

Abstract

FIELD: heat exchange apparatus. SUBSTANCE: hollow spacers 7 are provided with inclined connectors-turbulators 8 in zone of each hole 6 of plates 5. They are laid on holes of plates at turn angle of 180 deg every other plate. Surfaces of plates 5 in between spacers 7 in passages for cross flow of heat-transfer agent are provided with turbulizing members made in form of projections, for example, located at angle of 45 to 90 deg relative to axes of passages. EFFECT: intensification of heat exchange and facilitated manufacture. 2 cl, 4 dwg

Description

 The invention relates to recuperative heat exchangers of refrigeration, cryogenic and other heat transfer equipment. The invention is particularly suitable when used as a radiator for a motor vehicle for cooling charge air, oil and antifreeze, as well as a condenser, evaporator and other recuperative heat exchangers with a counter-current and cross-flow heat transfer scheme.

Known heat exchanger containing collectors and a channel for two coolants, organized by a package of heat-conducting plates separating the coolant, and spacers ribs, developing a heat transfer surface and artificially turbulent flows of each coolant [1]
The disadvantages of the known heat exchanger are the difficulty of using it in the presence of a significant difference in the pressures of the coolants (for example, more than 1 MPa), low reliability and poor manufacturability due to the relatively large number of assembly units of parts.

1,6·ζ·G²/(2·ρ·n²·d $\genfrac{}{}{0ex}{}{\text{2}}{\text{э}}$ )
то ухудшается интенсивность теплоотдачи. Для поддержания ее надо увеличивать расстояние между пластинами (или толщину проставок), которое, как правило, больше d_э. Это приводит к существенному уменьшению компактности теплообменника S/V, м²/м³ (величины теплообменной поверхности на единицу объема).Known heat exchanger, selected as a prototype, containing collectors and channels for at least two coolants, organized by a package of heat-conducting plates with rows of holes and spacers between rows of holes that separate the coolant [2]
The known design partially eliminates the disadvantages of the analogue, however, compared with it it has increased pressure loss (ΔP) in the channels under the same operating conditions and dimensions (frontal section) of the heat exchanger, which greatly limits the scope of use of such heat exchangers. This is due to the fact that in this design it is advisable to use holes with an equivalent diameter d _{e of} only less than 2 mm. If you increase the diameter of the hole d _e > 2 mm (for example, in order to reduce ΔP / ΔL under other identical conditions according to the known dependence
ΔP / ΔL = ζ · G ² / (2 · ρ · F $\genfrac{}{}{0ex}{}{\text{2}}{\text{at}}$ _s · d _e )

1,6 · ζ · G ² / (2 · ρ · n ² · d $\genfrac{}{}{0ex}{}{\text{2}}{\text{uh}}$ )
then the heat transfer rate deteriorates. To maintain it, it is necessary to increase the distance between the plates (or the thickness of the spacers), which, as a rule, is greater than d _e . This leads to a significant decrease in the compactness of the heat exchanger S / V, m ² / m ³ (the magnitude of the heat exchange surface per unit volume).

 The problem to be solved is the intensification of heat transfer, the expansion of functionality, in particular the expansion of the range of working pressure and the field of effective use, as well as increasing the manufacturability of manufacturing a heat exchanger by simplifying and reducing the number of assembly units of parts.

 A search has been conducted. No analogues defaming the distinctive part of the formula were found, on the basis of which it was concluded that this heat exchanger is new and has significant differences.

To solve the problem in a heat exchanger containing collectors and channels for at least two heat carriers, organized by a package of heat-conducting plates with rows of holes and spacers between rows of holes separating the heat carriers, according to the invention, the spacers are hollow with inclined jumpers-turbulators in the area of each hole of the plates and superimposed on the holes of the plates with an angle of 180 ^° through each plate, and the surface of the plates between the spacers in the channels for the cross-flow of the coolant t turbulent elements in the form of, for example, protrusions located at an angle of 45-90 ^about to the axis of the channels.

 In FIG. 1 shows a heat exchanger in the form of a radiator; bunks of fig. 2 node I in FIG. 1; in FIG. 3, section AA in FIG. 2; in FIG. 4 a section BB in FIG. 3; in FIG. 5 heat exchanger in the form of a condenser-evaporator; in FIG. 6 countercurrent cross-flow heat exchanger; in FIG. 7 counterflow heat exchanger.

The heat exchanger contains collectors (or collector plates) 1 and channels 2 and 3 for at least two coolants. These channels are organized by a package of 4 heat-conducting plates 5 with rows of holes 6 and spacers 7 separating the coolants. The spacers 7 are hollow with inclined jumper-turbulators 8 in the area of each hole 6 of the plates and are superimposed on the holes of the plates with an angle of 180 ^° through each plate 5. In the channels 3 for cross current, the surface of the plates 5 between the spacers 7 has turbulent elements 9 in the form , for example, protrusions located at an angle of 45-90 ^about to the axis of the channels 3.

The plates 5 and spacers 7 are made of a heat-conducting material, for example, aluminum alloy, copper, brass or steel. The plates 5 are made of a metal tape with a thickness of δ _l = 0.1-0.4 mm by passing between two special grooves, which provide an orderly cutting of the holes 6 and forming (or knurling) of the turbulence elements 9 on the surface of the plate of the desired width. The plates 5 can have additional local punctures 10 with a one-side bending of the shoulder (up to the thickness of the spacers 7) for fixing the spacers 7 on the outer end on the sheets during assembly, and also, if necessary, in areas with turbulent elements 9 to maintain the shape of the sheets during the soldering process 4 Spacers 7 with jumpers-turbulators 8 are made of a metal sheet with a thickness of δ _ol = 0.5-2 mm by stamping. To ensure sealing between the coolants, the plates 5 and the spacers 7, assembled in the package 4, can be compressed or glued, or welded. The design of channels 2 and 3 and the presence of 7 jumpers-turbulators in the hollow spacers 7 allow you to expand the possible range of operating pressures (or the possible difference in pressures between the coolants 2 and 3), for example, up to 20 MPa.

A², зависят от сочетания геометрических параметров турбулизирующих элементов, главными из которых являются относительная высота элементов (выступов) h/R h/(h + 0,05 a_уз) и расстояние между ними по оси потока t/h. Здесь а_уз расстояние между противоположными турбулизаторами (стенками) в узком проходном сечении канала. В частности, для канала 2, образованного отверстиями 6 в пластинах совместно с перемычками-турбулизаторами 8 проставок, это эквивалентный диаметр в узком проходном сечении единичного канала (a_уз)

d_э2= 4F_{i уз}/п_iуз, а для канала 3 с противоточным током теплоносителя (фиг. 2-4) (a_уз)₃= δ_пр-2h

d_э3/2 (δ_пр- толщина проставки). Высота турбулизаторов h₂ в канале 2 может быть различной по периметру единичного канала (п_iуз)₂) и равна или половине ширины перемычек 8 проставок, или половине ширины перемычки между отверстиями 6 в пластинах, или половине ширины перемычки между отверстием и внутренним торцом проставки на соответствующих частях периметра единичных каналов. При этом расстояние между турбулизаторами t₂ изменяется от δ_пр до 2 (δ_пр+δ_л).The invention provides in the channels of the heat exchanger with only two assembly units of parts (plate 5 and spacer 7) with a relatively simple manufacturing technology, achieving an effective combination of geometric parameters of turbulators to obtain rational intensification of heat transfer, as well as the development and ratio of heat exchange surfaces of channels 2 and 3 to various heat exchanger working conditions. It is known that in nonsmooth channels the increase in the average heat transfer intensity due to artificial turbulization of the flow (Nusselt number Nu) relative to heat transfer in a smooth channel (Nu _2l ), i.e. the value of Nu / Nu _hl A, as well as an increase in the coefficient of hydraulic resistance (ζ) compared with the average value of the resistance of a smooth channel (ζ _hl . _avg = 0.02), i.e. value ζ /

A ² depend on a combination of geometrical parameters of the turbulizing elements, the main of which are the relative height of the elements (protrusions) h / R h / (h + 0.05 a _knot ) and the distance between them along the flow axis t / h. Here a _{bond is the} distance between opposite turbulators (walls) in a narrow passage section of the channel. In particular, for channel 2 formed by holes 6 in the plates together with jumper-turbulators 8 spacers, this is the equivalent diameter in a narrow passage section of a single channel (a _knot )

d _e2 = 4F _{i knots} / p _iuz , and for channel 3 with countercurrent coolant current (Fig. 2-4) (a _knots ) ₃ = δ _pr -2h

d _{E3 / 2} (δ _ave - the thickness of the spacer). The height of the turbulators h ₂ in channel 2 can be different along the perimeter of a single channel (n _iuz ) ₂ ) and is equal to either half the width of the jumper 8 of the spacers, or half the width of the jumper between the holes 6 in the plates, or half the width of the jumper between the hole and the inner end of the spacer corresponding parts of the perimeter of single channels. The distance between the turbulators t ₂ varies from δ _CR to 2 (δ _CR + δ _l ).

To achieve rational intensification of heat transfer in the channels, i.e. for example, the values Nu / Nu _ch 2-4.5 and ζ / ζ _ch . _cp = 3-16, certain combinations of the values of (t / h) _rac are needed (for example, in the range from 2 to 6) depending on the accepted value of h / R (in particular, from 0.7 to 0.1, respectively).

α₃·S_*3,2·η_р2 или (при газообразных теплоносителях)
S_*3,2·η_р2

≈

на заданные условия работы (массовые расходы G₂ и G₃, тепловая нагрузка Q, средний температурный напор ΔТ_ср между теплоносителями, их теплофизические свойства и потери давления в каналах ΔР). Здесь η_p- эффективность оребрения, в частности, пластин между проставками.Heat exchanger construction provides a wide variation in geometric parameters turbulence and obtaining effective combination of all channels to achieve efficient heat transfer enhancement and the development of the heat exchange surface S (e.g., for channel 2S _{* 2} S ₂ / S _2gl. 5-6 _kt) and relations surfaces between channels (e.g. S _{* 3.2} S ₃ / S ₂ 1-3). This is important, in particular, in order to satisfy the well-known conditions for optimal heat transfer between heat carriers.

α ₃ · S _{* 3,2} · η _p2 or (with gaseous coolants)
S _{* 3,2} · η _p2

≈

for specified operating conditions (mass flow rates G ₂ and G ₃ , heat load Q, average temperature head ΔТ _cf between heat carriers, their thermophysical properties and pressure losses in channels ΔР). Here η _p is the efficiency of the fins, in particular, of the plates between the spacers.

 In the proposed heat exchanger, it is possible to realize the movement of heat carriers with cross current (Fig. 1), with countercurrent-cross current (Fig. 6) and with a clean countercurrent (Fig. 7).

 The heat exchanger operates as follows.

In cross-flow (Fig. 1), one of the coolants (for N ₂ ) can be a liquid or gas with increased pressure, condensing or boiling refrigerant, and as another coolant (for N ₃ ), for example, atmospheric air with forced movement from a fan. The coolant N ₂ is supplied through the input collector 1 to the channels 2 formed by rows of holes 6 in the plates 5 and the internal cavity of the spacers 7 with jumpers-turbulators 8, and leaves these channels 2 through the output collector. Heat carrier N ₃ (atmospheric air) enters and passes in channels 3 between spacers 7 and plates with turbulence elements 9. As the heat carriers flow in the channels, heat (Q) transfers from a warmer heat carrier, for example, in channel 2 to a cooler one in the channel 3 along the jumper-turbulators 8 and the walls of the spacers 7 and along the jumper plates located in the channel 2, and further along the plate-ribs with the turbulizing elements 9 of the channel 3. In this case, the plates and spacers must be sufficiently heat-conducting so that in working conditions oviyah efficiency of their fins η _p was close to unity.

A cross-flow heat exchanger can also be effectively used as a condenser-evaporator (Fig. 5). In this case, the axis of the flow in the channels 3 (between the spacers 7 and the plates with turbulent elements 9) is desirable to orient at an angle of 10-20 ^about to the vertical. Then, boiling liquid is introduced into these channels 3 from below, which in the channels 3 forms a lifting two-phase flow with an upper steam outlet after leaving the channels. 2 the channels are oriented at an angle ^of 10-20 to the horizontal, and in which steam is fed from above, which is condensed efficiently in the channels 2 and as condensate flows from the channel and discharged.

The heat exchanger can be performed with a clean counterflow (Fig. 7). Moreover, the channels 2 and 3 for coolants have a similar design (i.e., they are formed by rows of holes 6 in the plates 5 and the internal cavity of the spacers with jumpers-turbulators 8) with a possible difference in the size of the surface development S ₃ / S ₂ and the intensification of heat transfer in depending on the given working conditions.

The organization of countercurrent-cross current (Fig. 6) is especially advisable when creating large heat exchangers (with a volume of up to 10 m ³ ) from individual heat exchanging units with a cross current, as in FIG. 1. These blocks 4 can be manufactured in series and have certain sizes (for example, l _i x B _i x H 150 x 650 x H mm) with installed thermo-hydraulic characteristics. When calculating a large heat exchanger, the height (N) and the number of blocks for organizing at least five cross passages are optimized, which is equivalent to a clean countercurrent with direct and reverse flows. It is convenient to pass a direct flow with increased pressure through channels 2, and a reverse flow through channels 3 (between spacers 7 and plates with turbulent elements 9). Blocks 4 are joined sequentially in the direction of the axis of the channels 3 by welding the outer edge of the collector plates 1, and then, after assembly of the entire apparatus, the collectors are welded for direct flow. This assembly allows, in comparison with the existing technology with the soldering (or gluing) of large counterflow plate heat exchangers, to minimize material and monetary losses from possible defects during soldering (or gluing), as well as to eliminate axial thermal conductivity and possible uneven redistribution of flow in the channels.

 The proposed heat exchanger is competitive with the existing best heat exchangers in terms of thermo-hydraulic characteristics and compactness for specified operating conditions.

 The invention provides a rational intensification of heat transfer, expansion of functionality (in particular, expanding the range of working pressure and the field of effective use), as well as increasing the manufacturability of manufacturing a heat exchanger by simplifying and reducing the number of assembly units of parts.

Claims (1)

HEAT EXCHANGER containing collectors and channels for at least two heat carriers, organized by a package of heat-conducting plates with rows of holes and spacers between rows of holes separating the heat carriers, characterized in that the spacers are hollow with inclined jumpers-turbulators in the area of each hole of the plates and superimposed on the holes of the plates with a 180 ^° flip through each plate, and the surface of the plates between the spacers in the channels for the cross-flow of the coolant has turbulent elements Tapes in the form of, for example, protrusions located at an angle of 45 90 ^o to the axis of the channels.

Images