RU2659839C1 - Low-temperature refrigeration machine on carbon dioxide - Google Patents

Abstract

FIELD: refrigerating equipment.

SUBSTANCE: invention relates to refrigeration technology and can be used in freezing of biomaterials, food products, low-temperature processing of metals and alloys, in technological processes where artificial cooling is required in low temperature range from minus 60 to minus 130 °C. Low-temperature refrigerant on carbon dioxide contains three-stage small-sized compressor, on injection of which there are finned pipelines for cooling vapors after their compression, condenser at outlet of compressor third stage, for removing heat from carbon dioxide, followed by its condensation, sequentially located throttle valves and intermediate vessels for lowering pressure, separating steam from steam direction to first and second stages of compressor at intermediate pressures. Process of heat extraction from cooled product located on external surface of heat exchanger-load is carried out during sublimation of carbon dioxide from solid state, due to presence of vacuum pump, providing reduced pressure in hermetic volume of heat exchanger-load. System of throttling and uniform spraying of liquid carbon dioxide followed by its transformation into solid state in form of liquid pipeline with nozzles installed on it throttle. Internal heat exchange surface of heat exchanger-load for uniform distribution of solid carbon dioxide and its sublimation in process of heat extraction from cooled product.

EFFECT: technical result is to improve environmental friendliness, simplify design and achieve lower temperatures while reducing energy consumption.

1 cl, 2 dwg

Description

The invention relates to the field of power engineering, in particular refrigeration, specifically to compressor-type refrigeration, and can be used for freezing biomaterials, food, low-temperature processing of metals and alloys, in technological processes that require the consumption of artificial cold in the low temperature range from minus 60 to minus 130 ° C.

The vapor compression low-temperature refrigeration systems are known from the prior art, for example, a low-temperature refrigeration machine consisting of upper and lower stages (RU 122159 U1, 2012), this installation requires the use of synthetic working substances (chladones) that have a negative impact on the environment, it is distinguished by a high energy consumption and structural complexity due to the presence of many equipment in each cascade (compressors, condensers, oil separators, liquid separators, etc.), which increases the cost of installation at. In this case, the minimum temperatures achieved are determined by the selected working medium for the lower stage, so for R-13 freon the minimum temperature will be from minus 80 to minus 100 ° C.

Of interest is the scheme of a hybrid low-temperature refrigeration and freezer installation (US 20060144073 A1, 2004).

The refrigeration unit according to patent US 20060144073 A1 consists of a thermoelectric module that takes heat from the cooled volume and a vapor compression circuit that removes heat from the heated part of the thermoelectric module. This unit is able to maintain temperatures in a refrigerated volume up to minus 80 ° C.

The disadvantage of the installation is the increased energy consumption, pa compared with vapor compression systems, the need for a powerful current-stabilized power source for power supply of the thermoelectric module.

Currently, the trend continues to reduce the impact of human activities on the environment in refrigeration, this is reflected in the transition to the use of natural working substances: ammonia, hydrocarbons, carbon dioxide, water, which is confirmed by the publications:

Lorentzen G. “The use of natural refrigerants: a complete solution to the CFC / HCFC predicament”, International journal of refrigeration Vol 18, No. 3 (1995);

Yamaguchi H, Zhang H-R “A novel CO2 refrigeration system achieved by CO2 solid-gas two-phase fluid and its basic study on system performance)). International journal of refrigeration No. 32 (2009).

The closest analogue (prototype) of the invention is defined as a low-temperature two-stage compressor-type chiller based on hydrocarbon in the upper cascade and carbon dioxide in the lower cascade (JP 2001091074 A, 1999), containing two independent hydraulic circuits (cascade) connected by a heat exchanger-condenser, in which boils the working substance of the upper cascade with the absorption of heat from the cooled object and the condensation of the working substance of the lower cascade with the release of heat into the environment. Heat absorption in this installation is carried out due to the boiling of the working substance in the lower cascade, while the minimum attainable temperature is minus 56.6 ° C, which is determined by the triple point of carbon dioxide.

The disadvantages of the installation are the presence of two independent circuits with two compressors, the need to refuel with two working substances, which makes it more expensive to maintain, and the minimum temperature reached is minus 56.6 ° C.

The objective of the present invention is to provide an energy-efficient low-temperature refrigeration machine using an environmentally friendly natural working substance - carbon dioxide.

The technical result obtained from the use of the invention is to improve the environmental friendliness of the low-temperature refrigeration machine, simplify the design of the low-temperature refrigeration unit, achieve lower temperatures and reduce energy consumption.

The essence of the invention lies in the fact that the low-temperature refrigeration machine using natural working substance carbon dioxide circulating in a closed sealed hydraulic circuit of the machine contains a heat exchanger-load with a sealed internal space connected to the hydraulic circuit of the refrigeration machine, in which the working substance is sublimated with a supply heat from the cooled product, a vacuum pump that pumps carbon dioxide vapors from the heat exchanger-load at low pressure, a three-stage small-sized compressor that compresses carbon dioxide vapor, intermediate vessels that separate liquid carbon dioxide, an air-cooled condenser to remove heat from carbon dioxide to the environment during the phase transition from vapor to liquid, a liquid distribution pipeline, which supplies liquid carbon dioxide to cooling devices, throttle nozzles located directly on the liquid pipe, providing throttling of liquid carbon dioxide and spraying it onto the internal heat exchanger surface of the heat exchanger-load, during which the phase transformation is liquid-solid, where when heat is supplied from the cooled product located on the external surface of the heat exchanger-load due to heat transfer through the walls of the heat exchanger - load is the sublimation of the working substance.

To achieve the specified technical result in a low-temperature refrigeration machine, through the use of the solid-vapor phase transition (sublimation) sprayed onto the heat exchange surface in the heat exchanger-load, carbon dioxide under reduced pressure created by a vacuum pump, it is possible to achieve low sublimation temperatures in the range from minus 60 ° C to minus 130 ° C,

while the heat exchanger-load is made in such a way that the internal sealed space connected to the hydraulic circuit of the refrigeration machine has a heat exchange surface,

at the same time, liquid carbon dioxide obtained as a result of heat exchange with the environment is supplied through liquid pipelines and sprayed into the internal cavity on the developed surface of the heat exchanger-load, with a decrease in pressure, as a result of which carbon dioxide turns into a solid state in a finely dispersed form.

The proposed low temperature carbon dioxide chiller is illustrated in the drawings, where in FIG. 1 shows a schematic diagram of the installation, in FIG. Figure 2 shows the design of a heat exchanger-load with an inside liquid pipe and spray throttle nozzles for use in a low-temperature refrigeration machine.

The proposed low-temperature carbon dioxide refrigeration machine contains a closed hydraulic circuit of a vapor compression refrigeration machine operating in the reverse thermodynamic cycle with carbon dioxide as a working substance and low pressure in the heat exchanger-load.

The circuit of the refrigeration machine consists of a heat exchanger-load 1, a vacuum pump 2, a three-stage compact compressor 3, an air condenser 4, throttle valves 5, intermediate vessels 6, throttle nozzles 7 connected hydraulically by a piping system, on the discharge piping there are finned sections of pipelines 8.

The heat exchanger-load consists of a sealed volume 1, a finned surface 2 on which the cooled product 3 is placed on the outside, a pipeline for supplying a liquid working substance 4, throttle nozzles 5, a fitting for connecting a vacuum pump 6.

The proposed low-temperature refrigeration machine on carbon dioxide (Fig. 1) operates as follows. Carbon dioxide in a finely dispersed solid-state state sublimates when heat is supplied from a cooled object in a heat exchanger-load 1, it goes into a vapor state, then it is sucked into a vacuum pump 2, then it is pumped into the first stage of a three-stage compact compressor 3, when passing through each stage of the compressor to the compressible pair is mixed with saturated vapors from the intermediate vessels 6 at intermediate pressures; after passing through the third stage of the compressor 3, the vapor enters the condenser 4, where Due to the removal of heat into the environment, it condenses, passing from vapor to liquid, liquid carbon dioxide is throttled sequentially in throttle valves 5 and separated from steam in intermediate vessels 6, saturated liquid enters heat exchanger-load 1, saturated vapors are sucked into the compressor stage at intermediate pressures in the heat exchanger-load 1, saturated liquid enters through a liquid pipe and is sprayed in nozzles 7, the cycle closes.

In the heat exchanger-load (Fig. 2), the following processes occur: liquid carbon dioxide is supplied through the liquid pipe 1, is sprayed through the throttle nozzles 2, while it goes into a solid state in the form of snow, evenly distributed on the heat-exchange surface 3, from the outside of the heat exchanger - the load is the cooled product 4, sublimated carbon dioxide vapor is discharged along the suction line 5.

Claims (1)

A low-temperature carbon dioxide chiller operating on the principle of a vapor compression chiller, containing a three-stage small-sized compressor, at the discharge of which there are finned pipelines designed to cool the vapors after they are compressed, a condenser located at the outlet of the third compressor stage, designed to remove heat from the dioxide carbon with its subsequent condensation, sequentially located throttle valves and intermediate vessels designed for I reduce pressure, steam separation with the direction of steam in the first and second stages of the compressor at intermediate pressures, characterized in that the process of heat extraction from the cooled product located on the outer surface of the heat exchanger-load, is carried out in the process of sublimation of carbon dioxide from a solid state, due to the presence of a vacuum pump that provides reduced pressure in the sealed volume of the heat exchanger-load, a throttling system and uniform atomization of liquid carbon dioxide, followed by by turning it into a solid state in the form of a liquid pipeline with throttle nozzles installed on it, and an internal heat exchanger surface of the heat exchanger-load for uniform distribution of solid carbon dioxide and its sublimation in the process of heat extraction from the cooled product.

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