RU2327087C1 - Low-temperature chamber - Google Patents

Abstract

FIELD: heating, refrigerating engineering.

SUBSTANCE: invention relates to refrigerating engineering, particularly, to domestic and commercial low-temperature chambers (SLTC) with absorption-diffusion refrigerating machines (ADRM). Low-temperature chamber comprises a thermal-insulated housing of bin-type with internal metal chamber and refrigerating unit, evaporator of which is located beyond the usable volume of the chamber and is thermally connected with the usable volume. Two ADRMs installed at the side walls of housing are used a refrigerating unit. The side walls have openings where thermal-insulated units are installed. Thermal-insulated units are made of a high heat-conductivity metal in the form of box. From one side the box bottom is thermally connected to ADRM evaporator, from the other side - to the internal metal chamber. Rear and front walls of the internal metal chamber are additionally thermally-connected to the side walls by means of heat transfer equipment. Heat-removal sections of this equipment are installed at the area of thermal connection to ADRM evaporators. Heat pipes and two-phase or single-phase thermal siphons are used as heat transfer equipment. ADRM components, located beyond the housing, are closed with jackets having air openings at the upper and lower parts. Air fans are installed at the channels formed by jackets and side walls of the housing.

EFFECT: enhancement of low-temperature chamber performance characteristics on repairability.

10 cl, 3 dwg

Description

The invention relates to refrigeration, in particular to household and commercial low-temperature chambers (NTK) with absorption-diffusion refrigeration machines (ADXM).

Known NTK (Lepaev D.A. Repair of household refrigerators: Handbook. 2nd ed., Rev. And add. - M .: Legprombytizdat, 1989, p. 169 ... 171), containing a heat-insulated cabinet with a vertical door, divided partitions with guides on which the boxes (baskets) are installed, and a compression refrigeration unit installed on the rear wall of the cabinet. The evaporator of the refrigeration unit has a thermal connection with the useful volume of NTK.

A disadvantage of the well-known NTK is the inefficient design of the "cabinet" type in terms of heat influx from the environment. Moisture condenses on the surface of the evaporator of the refrigeration unit and freezes, forming an ice crust (fur coat), which leads to an increase in thermal resistance between the evaporator and the air in the chamber.

It should also be noted that the design of the well-known NTK uses a compression refrigeration unit, the operation of which is carried out only due to electric energy.

Known NTK (Small refrigeration units and refrigeration transport: Handbook. - M .: Food industry, 1978, S.80 ... 82), adopted as a prototype. The prototype contains a heat-insulated casing of the "chest" type with an internal metal chamber and a refrigeration unit, the evaporator of which is outside the useful volume of the chamber and has a thermal connection with the useful volume.

The design of the prototype uses a case of the type "chest", which eliminates the problems associated with air exchange between the cooled volume and the environment. When the cover is lifted, cold air, having a higher density than indoor air, remains in the chamber. In this case, the frost growth on the inner walls of the chamber is significantly reduced. However, the design of the prototype is not repairable in terms of replacing the refrigeration unit compression action. This affects the performance of the prototype. In the event of a breakdown of the refrigeration unit, its replacement is associated with significant financial costs.

The objective of the invention is to improve the operational properties of NTK in terms of maintainability by providing the ability to replace failed ADXM without destroying the heat-insulating housing of the NTK.

The problem is solved in that in a low-temperature chamber containing a heat-insulated casing of the "chest" type with an internal metal chamber and a refrigeration unit, the evaporator of which is outside the useful volume of the chamber and has a thermal connection with the useful volume, according to the invention, two absorption units are used as a refrigeration unit diffusion chillers (ADXM), which are installed on the side walls of the housing, and the side walls have openings in which heat-insulated blocks are installed, made They are in the form of a duct made of highly heat-conducting material, and the bottom of the duct has thermal connection with the ADXM evaporator on the one hand, and with the internal metal chamber on the other.

The rear and front walls of the inner metal chamber have additional thermal communication with the ADXM evaporators using heat transfer devices, and the heat sink sections of these devices are installed in the heat communication zone with the ADXM evaporators.

As heat transfer devices use heat pipes.

As heat transfer devices, single- or two-phase thermosiphons are used, with the thermosiphon heat sink section installed above the heat supply section.

Vertical ribs are installed on the inner surfaces of the side walls of the metal chamber in the area of thermal communication with ADXM evaporators.

Vertical ribs are installed on the back and front walls of the inner metal chamber.

The ADXM elements located outside the enclosure are covered by casings having openings for the passage of air in the lower and upper parts.

In the channels formed by the casings and side walls of the housing, fans are installed.

The essence of the proposed solution is illustrated by drawings.

Figure 1 shows a General view of NTK with ADXM (front view).

Figure 2 is a top view (section aa).

Figure 3 is a side view with ajar lid (section BB).

The low-temperature chamber contains a thermally insulated body 1 with a top cover 2 and with an internal metal chamber 3, as well as two ADXM 4 with heat-insulated blocks 5 installed in the openings of the side (end) walls of the housing 1. The evaporators 6 of the ADXM 4 are completely located in the volume of the heat-insulated block 5, made in the form of a box, and thermally connected with the bottom 7 of the insulated block 5.

On the surfaces of the inner metal chamber installed vertical ribs 8 (see figure 1 ... 3).

Heat transfer devices 9 connect the front and rear walls of the inner metal chamber with the bottom 7 of blocks 5.

The ADXM elements located outside the housing 1 are closed by covers 10. For operation in harsh thermal conditions, fans 11 are installed in the lower part of the covers.

Heat transfer devices 9 provide effective thermal communication between the rear and front walls and side walls of the inner metal chamber 3 with a sufficiently long NTK.

As heat transfer devices, heat pipes and thermosiphons can be used.

Heat pipes have a low internal thermal resistance. Heat transfer to them is carried out using the heat of vaporization of the coolant over considerable distances with a minimum temperature head. The return of the liquid coolant is ensured by capillary forces, which allows the use of heat pipes in heat transfer systems with a heat sink "from top to bottom" (Chi S. Heat pipes: Theory and practice. - M .: Mashinostroenie, 1981).

In the case of using thermosiphons as heat transfer devices, the heat siphon heat sink section should be installed above the heat supply section.

The advantage of thermosiphons is their simplicity and high reliability due to the lack of capillary-porous systems. Heat transfer in thermosyphons is carried out in the mode of natural convective movement of the coolant - its "cold" end (heat sink) should be located above the site of the "hot" end (heat supply).

In two-phase thermosyphons, heat transfer is carried out in the mode of vaporization, and condensate return by gravity. In this case, two positive qualities of heat pipes and thermosiphons are combined - high heat transfer characteristics, simplicity, reliability and low cost.

Single-phase thermosiphons are almost completely filled with a liquid coolant that circulates in the natural convection mode.

Compared with two-phase, they are simpler to manufacture and reliable in operation.

Vertical ribs 8 installed on the inner surfaces of the side walls in the area of thermal communication with the ADXM evaporators reduce the thermal resistance during heat transfer from the air in the useful volume of the NTC to the walls thermally connected with the ADXM evaporators.

Vertical ribs 8 installed on the rear and front walls of the inner metal chamber 3, allow to minimize thermal resistance during cooling of the loaded products.

The installation of the casing 10 allows you to form an air cavity, inside which are located the heat dissipating elements of the ADXM - reflux condenser, absorber, condenser. Heat removal from these elements is carried out in the air in the cavity. Its temperature is always higher than the temperature of the air outside the casing.

The temperature difference creates a lifting (Archimedean) force. Warm air exits through the upper openings of the casing, and cooler air from the room enters through the lower openings. A peculiar column of warm air is created, the vertical characteristic size of which determines the magnitude of the additional driving pressure. The speed of the air washing the heat dissipating elements is higher than in the case of the natural convective cooling mode.

In this case, additional supercooling of the flows of the working fluid in the heat-dissipating elements of the ADXM is carried out. In the condenser, additional subcooling of liquid ammonia reduces the cost of cold in the regenerative heat exchanger of the evaporator. Lowering the temperature level in the absorber allows for higher purification of the vapor-gas mixture entering the evaporator inlet. It also increases the refrigeration capacity of the evaporator without additional energy costs.

To an even greater extent, the intensity of heat transfer from the outer surfaces of the ADXM heat-dissipating elements can be increased if fans 11 are installed in the air cavity formed by the casing 10 and the side walls of the housing.

Fans create forced circulation of air in the channels. The air velocity in this case becomes an order of magnitude higher.

The most effective use of fans (even with additional energy consumption) at elevated room temperatures (in the summer) and at the initial moment of loading the chamber with “warm” products.

The low temperature chamber operates as follows.

When the ADCM is turned on, the generation of ammonia begins, followed by liquefaction and feeding into evaporator 6. In evaporator 6, ammonia evaporates into a hydrogen (inert gas) medium at a low partial pressure, i.e. at low temperatures, and, thus, provides the production of artificial cold. The evaporator cools the bottom 7 of unit 5. Cold air is lowered into the lower part of the inner metal chamber, while cooling objects placed in it. The installation of two ADXM 4 on the end walls provides high cooling capacity at a temperature level minus (24 ... 18) ° C and a symmetrical heat sink (due to the initial temperature of the loaded products and heat influx from the environment) through an internal metal chamber to the ADXM evaporators.

At the bottom 7 of block 5, condensation sections of heat transfer devices (TPU) 9 are fixed, which, when the ADXM operates, are subjected to cooling. Cooling causes condensation of the coolant vapor in the case of using heat pipes or two-phase thermosiphons or a temperature difference is created that causes the coolant to move in a single-phase thermosiphon, i.e. in any case, heat is transferred from the heat-absorbing zone of the TPU 9 located on the rear or front walls of the inner metal chamber 3.

The location of the ribs 8 around the perimeter of the inner metal chamber 3 provides a uniform cooling process, which is especially important with a dense load of the usable volume, when the natural circulation of air is difficult.

When the ambient temperature rises above 32 ° C or when loading a large number of uncooled products into storage, fans 11 are turned on, which provide a forced air circulation mode in the casing cavity 10. A sharp increase in heat transfer from the condenser and ADXM absorber leads to an increase in the cooling capacity of evaporators and a decrease temperature level on them. All this allows for the implementation of intensive cooling and freezing.

The case of an STC of the "chest" type contributes to the preservation of cooled air in the usable volume and does not allow air from a room with a humidity of at least 70 ... 80% to fall on heat-conducting surfaces. This allows you to significantly reduce the intensity of freezing of the snow coat and, thereby, improve the operational characteristics of the NTC.

The advantage of the proposed NTK with the location of the ADXM evaporators in separate heat-insulated blocks with a front heat-receiving surface made of highly heat-conducting material consists of:

- a significant increase in the maintainability of the NTK design - if any ADXM fails, it is easily removed from the side wall without destroying the NTK heat-insulating casing;

- to increase the usable volume due to the removal of the evaporator beyond its limits;

- in increasing the overall dimensions of the evaporator, i.e. refrigerating power ADXM;

- in the exclusion from the technological cycle of ADCM production of galvanizing, which requires significant environmental and sanitary measures;

- the ability to work on various sources of thermal energy - the operation of the STC in transport and in inaccessible areas where there is no electric energy.

Claims (10)

1. A low-temperature chamber containing a heat-insulated casing of the "chest" type with an internal metal chamber and a refrigeration unit, the evaporator of which is outside the useful volume of the chamber and has a thermal connection with the useful volume, characterized in that two absorption diffusion refrigeration units are used as the refrigeration unit machines (ADXM), which are installed on the side walls of the housing, and the side walls have openings in which heat-insulated blocks made in the form of a box are made of high heat metal, while the bottom of the box, on the one hand, has a thermal connection with the ADXM evaporator, and on the other, with the internal metal chamber. 2. The low-temperature chamber according to claim 1, characterized in that the rear and front walls of the inner metal chamber have additional thermal communication with the side walls using heat transfer devices, and the heat sink sections of these devices are installed in the heat communication zone with ADXM evaporators. 3. The low-temperature chamber according to claim 2, characterized in that heat pipes are used as heat transfer devices. 4. The low-temperature chamber according to claim 2, characterized in that thermosiphons are used as heat transfer devices, wherein the thermosiphon heat sink section is installed above the heat supply section. 5. The low-temperature chamber according to claim 4, characterized in that two-phase thermosyphons are used. 6. The low-temperature chamber according to claim 4, characterized in that single-phase thermosyphons are used. 7. The low-temperature chamber according to claim 2, characterized in that vertical fins are installed on the inner surfaces of the side walls in the area of thermal communication with the ADXM evaporators. 8. The low-temperature chamber according to claim 7, characterized in that the vertical ribs are mounted on the rear and front walls of the inner metal chamber. 9. The low-temperature chamber according to claim 8, characterized in that the ADXM elements located outside the housing are closed by casings having openings for air passage in the lower and upper parts. 10. The low-temperature chamber according to claim 9, characterized in that in the channels formed by the casings and side walls of the housing, fans are installed.

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