RU2495321C1 - Cryogenic liquid evaporator - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: cryogenic liquid evaporator includes a housing with cooling agent inlet and outlet chambers, heat exchange elements containing a liquid cooling agent chamber and a central tube equipped with an ejector. Cooling agent inlet and outlet chambers are divided with a partition wall with a hole, heat exchange elements are installed in the partition wall and interconnected with the central tube; the central tube is installed into the hole made in the partition wall with a gap, and the ejector has an insert that controls gaseous cooling agent from liquid cooling agent chambers. Cryogenic liquid evaporator is equipped with a recuperator. Evaporator allows increasing cooling agent use efficiency due to repeated use of cooling agent and arrangement of two-stepped cooling of working substance.

EFFECT: absence of any additional heat source for evaporation of liquid cooling agent and absence in the design of massive heat exchange head pieces additionally increases evaporator operating efficiency and reduces hydraulic resistance of an evaporator.

1 cl, 3 dwg

Description

The invention relates to cryogenic techniques, namely to evaporators of cryogenic liquid, and can be used in gasification plants.

Known vaporizer cryogenic liquid [and.with. USSR No. 1275182, F17C 9/02. Publ. 12/07/86, bull. No. 45], comprising a housing with inlet and outlet distribution devices, a main heat exchange element located inside the housing in the form of a regular nozzle with channels for the cryogenic liquid flow, and an additional heat exchange element with a bulk nozzle installed behind the main heat exchange element along the cryogenic liquid flow.

The cryogenic liquid enters through the inlet switchgear into the evaporator body, where in the main heat exchange element the cryogenic liquid is completely evaporated in the film boiling mode. An additional heat-exchange element is designed to evaporate droplets that have remained in the stream, return them to the evaporation zone and maintain a given pressure drop between the evaporation zone and the outlet of the evaporator.

The disadvantage of this evaporator is that the evaporation of cryogenic liquid occurs due to the heat stored from the pre-heating with hot gas, which leads to additional energy consumption. In addition, this device does not allow you to return the heated vapor of the cryogenic liquid for re-cooling, which leads to an excessive consumption of cryogenic liquid.

Known evaporator of cryogenic liquid [RU No. 2239121, F17C 9/02, F25B 39/02. Otub. 10/27/2004, bull. No. 30], adopted for the prototype. The cryogenic liquid evaporator comprises a housing with units for supplying and dispensing refrigerant and a heat exchange unit. The refrigerant supply unit includes a nozzle forming an annular cavity in communication with the liquid refrigerant chamber with the outer wall of the central pipe. The heat exchange unit is made in the form of a tube bundle, the annular space of which contains a bulk nozzle. The refrigerant dispensing unit is made in the form of a central pipe equipped with an ejector, the receiving chamber of which is in communication with the annulus, and the nozzle is connected to the gaseous refrigerant chamber.

Cryogenic liquid (for example, liquid nitrogen) enters through the inlet pipe, the annular cavity and the lower chamber of the liquid refrigerant into the tubes of the heat exchange element, where the complete evaporation of the cryogenic liquid. The resulting vapor through the upper chamber of the gaseous refrigerant and the pipe enters the nozzle of the ejector. Vapors of cryogenic liquid from the nozzle pick up gas (at the initial moment of time) air from the receiving chamber of the ejector, mixing with it and cooling it, transport it through the central pipe and then to the cooled apparatus. From the cooled apparatus, the heated (spent) vapors of the cryogenic liquid again enter the evaporator. In the evaporator, due to the discharge in the receiving chamber created by the ejector, the vapor passes through the holes in the cylindrical shell, the bulk nozzle and enters the receiving chamber of the ejector. In this case, the vapors are cooled, giving off heat to the bulk nozzle and to the heat exchange element. From the chamber, the cooled vapors are directed by the ejector to the central tube, from where, simultaneously mixing and additionally cooling with the cryogenic vapor from the ejector nozzle, they exit the evaporator to cool the apparatus.

The design of the evaporator does not allow efficient use of the refrigerant (especially at the time of starting the evaporator) due to the large mass and, accordingly, the high heat capacity, the bulk nozzle, which takes a large amount of refrigerant to cool. The presence of a bulk nozzle also negatively affects the efficiency of using the refrigerant during the operation of the evaporator, making the process of adjusting the temperature of the gaseous refrigerant inertial, it is necessary to wait until the entire volume of the nozzle has reached the required temperature. In addition, the nozzle creates significant hydraulic resistance for the passage of gaseous refrigerant.

The objective of the invention is a more efficient use of refrigerant by reducing overhead costs of the refrigerant, reducing the inertia of the process of regulating the temperature of the gaseous refrigerant at the outlet of the evaporator and reducing the hydraulic resistance of the evaporator.

The problem is solved in that the cryogenic liquid evaporator comprises a housing with refrigerant supply and discharge chambers, heat exchange elements containing a liquid refrigerant chamber and a central pipe equipped with an ejector, moreover, the refrigerant supply and discharge chambers are separated by a partition with an opening, the heat exchange elements are installed in the partition and communicate with a central pipe jumpers, the central pipe is installed in the hole in the partition with a gap, and the ejector has an insert that regulates the flow of gaseous refrigerant cient of liquid coolant chambers. In addition, the cryogenic liquid evaporator is equipped with a recuperator.

Figure 1 shows a longitudinal section of the proposed evaporator of cryogenic liquid; figure 2 - remote element A, figure 3 - external element B.

The evaporator comprises a thermally insulated body 1 (see FIG. 1), divided by a partition 2 into a chamber 3 for supplying waste (warm) refrigerant and a chamber 4 for dispensing refrigerant. In the partition there is a hole in which the central pipe 5 is inserted, the outer surface of which forms an annular gap 6 with the partition 2 (see figure 2). Heat exchange elements 7 with a chamber 8 for liquid refrigerant, a nozzle 9 for supplying liquid refrigerant and a control valve 10 are installed on the partition. The number of heat exchange elements is determined based on the required capacity of the evaporator. The chamber 8 is connected to the central pipe 5 by means of a jumper 11. The chamber 3 has a nozzle 12 for entering the spent (warm) refrigerant from the cooled apparatus (not shown), the chamber 4 has a nozzle 13 for exiting the refrigerant with a given temperature into the cooled apparatus. The temperature of the refrigerant is controlled by the sensor 14. The amount of cryogenic liquid in the chamber 8 is controlled by level gauges 15. The central pipe 5 is equipped with an ejector 16 (see figure 2), in which the flow rate of the ejection flow is controlled by changing the width of the annular gap 17 by means of the conical insert 18 and the rod 19 s threaded shank 20 (see figure 3). The refrigerant discharge chamber 4 is connected by a pipe 21 (see FIG. 1) to a recuperator 22. The recuperator is equipped with some kind of heat exchange element 23 (for example, a coil) with a nozzle 24 for inlet and a nozzle 25 for the outlet of the cooled working medium and a nozzle 25 for the exhaust refrigerant with valve 26.

The evaporator operates as follows.

Cryogenic liquid (for example, liquid nitrogen) enters through the pipe 9 into the chamber 8 of the liquid refrigerant. Nitrogen begins to evaporate, its vapors through the jumper 11 enter the central pipe 5 and are ejected through the annular gap 17 into the chamber 4. The resulting stream of flow begins to eject gas from the chamber 3 through the gap 6. Gas (exhausted, warm refrigerant) enters the chamber 3 through a pipe 12 from a refrigerated apparatus (not shown). Thanks to ejection, the warm refrigerant is mixed with the cold gaseous refrigerant. By adjusting the flow rates of warm and cold gases, the necessary temperature of the refrigerant is set, and then it is directed from the chamber 4 through the pipe 13 to a cooled device (not shown). In addition, the ejector creates a pressure differential between chambers 3 and 4, which is the driving force for moving the gaseous refrigerant located in the refrigerated apparatus. The warm gas entering the evaporator from the cooled unit is a heat source for evaporating liquid nitrogen in the heat exchange element 7. The ejected gaseous refrigerant circulates through the chamber 4 along the outer walls of the heat exchange elements 7 and the amount of heat transferred from the gaseous refrigerant stream in the chamber 4 to the liquid refrigerant in the chamber 8 depends on the height of the liquid column H (see figure 1). With a decrease in this height, the boiling area of the liquid refrigerant decreases, the amount of vapor of the evaporated liquid decreases, and therefore, the temperature of the gaseous refrigerant at the outlet of the evaporator increases. As the height of the liquid column H increases, the reverse process occurs, as a result of which the temperature of the gaseous refrigerant decreases. The level of liquid refrigerant in the chamber 8 is controlled by a level gauge 15 and is regulated by a valve 10. The intensity of gas circulation in the chamber 4 is controlled by the width of the gap 17, which is changed using a conical insert 18 with a rod 19 by moving up and down by rotating the threaded shank 20.

During the mixing of warm and cold flows, an excess of refrigerant is formed. This excess gas from the chamber 4 of the gaseous refrigerant enters through the pipe 21 to the recuperator 22. In the recuperator, the refrigerant contacts the heat exchange element 23 and cools the working medium in the heat exchanger 23. This working medium receives pre-cooling in the recuperator, after which it is finally cooled in the apparatus (not shown), where the refrigerant coming from the evaporator branch pipe 13 is used.

Thus, when using the proposed evaporator of cryogenic liquid, two-stage cooling of the working medium with sequential cooling at the first (preliminary) stage in the recuperator and final cooling in the apparatus (not shown) is organized. In this case, one part of the spent refrigerant after mixing with the cold refrigerant is returned through the pipe 13 to a device (not shown) for final cooling of the working medium, and the other part, before being discharged from the evaporator, goes to the recuperator to the first stage of cooling of the working medium. In addition, heat for evaporation of the liquid refrigerant in the heat exchange elements 7 is taken from the spent refrigerant, and not from an additional heat source. The amount of refrigerant discharged from the evaporator and, therefore, the intensity of the recuperator is controlled by valve 26.

The use of the invention allows to increase the efficiency of use of the refrigerant due to the reuse of the refrigerant and the organization of two-stage cooling of the working substance. The absence of any additional heat source for evaporation of the liquid refrigerant and the absence of massive heat transfer nozzles in the design further increase the efficiency of the proposed evaporator and reduce the hydraulic resistance of the evaporator.

Claims (2)

1. The evaporator of cryogenic liquid, comprising a housing with chambers for supplying and dispensing refrigerant, heat exchange elements containing a chamber of liquid refrigerant, and a central pipe equipped with an ejector, characterized in that the chambers for supplying and dispensing refrigerant are separated by a partition with an opening, the heat exchanging elements are installed in the partition and jumpers communicate with the central pipe, the central pipe is installed in the hole in the partition with a gap, and the ejector has an insert that controls the flow of gaseous refrigerant from the liquid chambers th refrigerant. 2. The cryogenic liquid evaporator according to claim 1, characterized in that it is equipped with a recuperator.

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