DE3219128A1 - Multi-circuit liquefier - Google Patents

Abstract

The invention relates to a multi-circuit liquefier for refrigerating installations with mutually independent liquefier trains which are arranged in parallel, two and more trains being connected to form mutually independent liquefier circuits. In order to avoid numerous difficulties of the previous system, the aim of the invention is to manufacture a multi-circuit liquefier which constitutes a considerable improvement both with regard to the material requirement and with regard to the capacity. To this end, the multi-circuit liquefier (cf Fig. 4) is constructed from elements which are in each case constructed from 1.5; 2; 2.5; 3; 4; 6; 8 or 9 trains which, in relation to pipe diameter, connection, as well as structures in the inside of the tubes which create pressure losses, are calculated in such a manner that at nominal capacity all elements, via the refrigerant-side pressure loss, are assigned precisely that refrigerant mass flow which can be completely liquefied in the elements. The refrigerant mass flow is in this case adapted to the tube diameter and the tube length in such a manner that the product of the inner heat-transfer number and the logarithmic temperature difference between refrigerant and air represents an optimum.

Description

Our reference: Th / Ham-ve THERMAL-Werke

Heating, cooling and air conditioning GmbH Ebertstrasse 2 ■ 4

69o9 Halldorf

MULTI-CIRCUIT CONDENSER

The invention relates to a multi-circuit condenser according to the preamble of the main claim. Have condensers of the type mentioned here depending on the size up to approximately 25o side by side strings of the same size with power per string between 500 and 3oo watts. By combining different numbers of strands, they become independent of each other Generated condenser elements, which are then operated in separately working refrigeration systems. Condensers of the type mentioned are preferably used in food wholesalers, where, for example, a large number of Cold locations are to be operated. These cold spots can be cold rooms, refrigerators, freezers, etc. So far, such multi-circuit condensers have been combined primarily for reasons of a simple structure of the entire heat exchanger from strands of the same power and size. This arrangement had mainly in a relief of the Calculation and interpretation of different services make sense. With the circuit that has been customary up to now, a performance optimization per strand or per Circuit (the latter grouped from strands) no consideration. The small power available per condenser line in this system is system-related, because you want the lowest possible line output to achieve the required cooling output of the individual compressors as precisely as possible To be able to interconnect a certain number of strands. V? Because of the very low line performance per element and the resulting from it resulting in a very low flow rate of the refrigerant inside of the pipes, the condenser will work in a range of very low internal heat transfer coefficients.

One could avoid the above disadvantages of this system

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a) reduce the pipe diameter

b) increase the refrigerant mass flow.

The measure a) leads to an increase in the cost of the heat exchanger, since the inner area is reduced linearly with the diameter and the decrease in innörer Surface is not compensated for by improving the internal heat transfer.

Measure b), namely an increase in the power per line, is due of the market requirements mentioned, namely a fine company. 'Possibility of splitting is also not possible.

Due to the low output per condenser line and the resulting in Connected small circuit along the refrigerant-side pressure loss of the condenser is very low without including the header pipes (e.g. approx. 0.006 bar) and, depending on the header pipe diameter used, is still below the pressure loss of these header pipes. This leads to a very poor distribution of the refrigerant hot gas flow over the individual condenser lines, see above that in practice the strands closest to the entry into the hot gas manifold due to the lower pressure loss that the refrigerant in the short header pipe section experiences the greatest refrigerant mass flow. Since the external heat transfer in the named strands is no better than in the strands further out, not all of the gaseous refrigerant can be liquefied here, so that a liquid-gas mixture of state 2 ' (see Fig. 1) reaches the liquid storage tank via the refrigerant outlet manifold and only condenses there. This heats up the liquid reservoir. Since the heat dissipation from the liquid storage container to the environment is negligibly small, the resulting Heat of condensation of the "penetrating" strands (i.e. those strands which are closest to the entry into the hot gas manifold) can only be removed by the fact that the refrigerant leaves the condenser in a large number of strands further away from the hot gas inlet State 2 "(see Fig. 1).

This subcooling comes from the accumulation of refrigerant in the condenser

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comes about as a result of the above-mentioned construction. Through this damming up of refrigerant in part of the condenser tubes takes up valuable space lost for condensation. There is therefore a considerable reduction in performance, both due to the accumulation of refrigerant in part of the condenser tubes, and due to the poor internal heat transfer the too low refrigerant speed.

The invention has set itself the task of avoiding the difficulties of the previous system indicated above and of producing a multi-circuit condenser which represents a significant improvement both in terms of material requirements and in terms of performance. For this ftteck, the multi-circuit condenser is built up from elements, each of which consists of 1.5; 2; 2.5; 3; 4; 6; 8 or 9 strings are constructed, which are calculated with regard to pipe diameter, circuit, and pressure loss-generating internals inside the pipes in such a way that at rated output all elements are allocated the refrigerant mass flow that can be completely liquefied in the elements via the pressure loss on the refrigerant side. The refrigerant mass flow is matched to the pipe diameter and the pipe length in such a way that the product of the internal heat transfer coefficient and the logarithmic temperature difference between refrigerant and air represents an optimum.

To achieve the aforementioned benefits, it can be useful to use in In a multi-circuit condenser, circuits with different pipe diameters and fin geometries can also be used.

About the even distribution of the refrigerant on the individual lines To ensure a cycle, individual strands can be inside everyone Pipes contain elements to increase the pressure drop on the refrigerant side.

If necessary, however, only some of the tubes of a strand can be used be provided with elements to increase the pressure loss on the refrigerant side.

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As elements to increase the pressure loss on the refrigerant side for the Displacement tubes have been found to be optimal in the present invention.

In the case of a Mahrkreislauf condenser, the amount of air available to remove the condensation heat is determined by the installation of axial or radial fans. A multi-circuit condenser of a certain size has a certain predetermined amount of air and a predetermined overall width to accommodate all independent refrigerant circuits consisting of individual lines. Since there are numerous possibilities in dividing the available strands into individual circuits, it is necessary that all elements from which the circuits are composed and which in turn have between 1.5 to 9 strands are designed so that for one For a certain condenser output, the same air volume and condenser length are always available, with tolerances in the range of ί Jo% permissible for the width of the elements. The sum of all the widths of the elements results in the total ribbed length of the multi-circuit condenser. The maximum tolerances are already taken into account for the overall length of the multi-circuit condenser.

In the drawings are exemplary embodiments of the subject matter of the invention shown:

Fig. 1: Mollier-h, Ig p diagram for refrigerants with a drawn in Chiller process.

Fig. 2: shows a multi-circuit condenser of the type discussed here.

Fig. 3: shows a section of the strands lying next to one another composite refrigeration circuits of the previously common type.

Fig. 4: shows the layout of the same multi-circuit condenser as in Fig. 3, but with elements according to the invention.

Fig. 5: shows further elements according to the invention shown individually.

Fig. 6: shows the construction of the refrigerant-side Pressure loss according to the invention used displacement pipe.

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The multi-circuit condenser according to Fig. 2 consists of a heat exchanger with a number of adjacent circuits (1). The heat exchanger is ventilated here by radial fans (2) which convey the cooling air from the bottom through the ribbing of the heat exchanger. In order to have enough space under the condenser for the air supply and possibly other elements of the circuit , sufficiently high feet (3) are attached under the heat exchanger.

Fig. 3 shows that a number of strands (4) through manifolds for the hot gas inlet (5) and such manifolds for the liquid outlet (6) Circuits (7) are interconnected. As has already been explained in the preceding description, the strands (8) which in the Exit from the hot gas manifold (5) near the inlet area (9), so strongly loaded that at the end (8a) of the strands (8) still uncotxolliert Gaseous refrigerant escapes, while in the strands (lo) located at a distance from the refrigerant inlet there is already a back pressure of refrigerant. When using elements according to the invention, as it is shown in Fig. 4, the circuits are built up only from elements, which by switching or pipe diameter or additionally by using displacement pipes inside are matched in their pressure loss so that this over the pressure loss of the header pipes, which results in a uniform refrigerant distribution; that means, that elements with a circuit at the fewer pipes are one behind the other by using displacement pipes or by corresponding interconnection to the required pressure loss to be brought.

In Fig. 4 an element with 2 strands (11) is shown, as well as another Element with 4 strands (12), which have a different tube diameter and a different lamellar geometry than the strands (13) also shown and (14). The element (13) corresponds to an output of 3 strands, the element (14) to an output of 8 strands of the previous design. In the case of element (14), the circuit is made so that a double-flow switched first part is switched to single-flow circulation.

Fig. 5 shows further elements, whereby the element in Fig. 5a the power of 1.5 strands of the previous design, the element in Fig. 5b the power of 2.5 strands, the element in Fig. 5c the power of 6 Strands and the element in Fig. 5d corresponds to the power of 9 strands of the previous design.

Fig. 6 shows a displacement pipe according to the invention, which is designed so that ss only a pressure loss ^f ind produces only a slight reduction in performance. If other internals are used inside the tube, for example twisted sheet metal strips or sheet metal strips with lateral stampings, many more tubes of an element must be fitted than with a displacement tube according to the invention. Considered publications:

The state of the art relates to the applicant's technical documents, as well as the companies KUBA and Güntner.

Claims (1)

Claim ^ / f?) Claim 1 . · Multi- circuit condenser for refrigeration systems with independent, parallel-arranged condenser lines of the same power, whereby two or more lines are connected to form independent condenser circuits, characterized in that the multi-circuit condenser consists of elements consisting of - each 1.5; 2; 2.5; 3; 4; 6; 8 of the 9 strings (heat exchanger modules) have thawed, which are calculated with regard to pipe diameter, circuitry and pressure loss-generating installations inside the pipes in such a way that, at nominal output, all elements are allocated the refrigerant mass flow that is currently in the elements can be completely liquefied, the refrigerant mass flow being matched to the pipe diameter and pipe length so that the product of the internal heat transfer coefficient and the logarithmic temperature difference between refrigerant and air is an optimum. Claim 2: Multi-circuit condenser according to Claim 1, characterized in that it has circuits which are separate from one another at the same time each contains different pipe diameters and fin geometries. Claim 3: According to claim 1, characterized in that all Tubes of a string contain elements to increase the pressure loss in the refrigerant. Claim 4: Multi-circuit condenser according to claim 1, d a d u r c h characterized in that some of the tubes of a string have elements inside to increase the refrigerant-related pressure loss. Claim 5: Multi-circuit condenser according to one of Claims 3 or 4, characterized characterized in that the elements are designed as displacement tubes to increase the pressure loss associated with the refrigerant.