WO2012125068A1

WO2012125068A1 - Evaporator

Info

Publication number: WO2012125068A1
Application number: PCT/RU2011/000642
Authority: WO
Inventors: Сергей Иванович ПЕТРОВ
Original assignee: ГРАМШ, Владимир Анатольевич
Priority date: 2011-03-16
Filing date: 2011-08-25
Publication date: 2012-09-20

Abstract

The claimed utility model relates to the field of refrigeration engineering and can be used as an evaporator in a domestic refrigerator, and also as an evaporator in any refrigerating device for industrial or commercial purposes. The proposed evaporator comprises a heat accumulator which constitutes a metallic plate formed from aluminium by a casting method. A channel for the evaporation of refrigerant is arranged in the plate body, wherein the thickness of the plate sections which are arranged between rectilinear sections of the evaporation channel is less than the thickness of the plate sections which are arranged around the evaporation channel. The combination of essential features of the claimed evaporator ensures an increase in the density of the heat flow supplied to the evaporable refrigerant.

Description

Evaporator.

Technical field

The inventive utility model relates to the field of refrigeration and can be used as an evaporator of a domestic refrigerator, as well as an evaporator of any refrigeration device for industrial or commercial use.

State of the art

Currently, the main task in the field of refrigeration is to reduce the amount of electricity consumed by a household refrigerator and other refrigeration devices. The amount of electricity consumed is directly dependent on the operating time of the refrigeration unit, during which the process of cooling the air contained in the cavity of the refrigerating cabinet is carried out, as well as on the length of the time interval between shutting down the refrigerating unit and its subsequent switching on.

The essence of the problem is that in most household refrigerators manufactured by modern industry, evaporators are used that are functionally designed to cool the air by means of a refrigerant evaporated in the cavity of the evaporator channels. In this case, heat is supplied to the evaporated refrigerant through the wall of the evaporation channel directly from the cooled air. Therefore, the cooling capacity of the refrigeration unit and its operating time is determined by the amount of heat flow supplied to the evaporated refrigerant from the cooled air. The value of the specified heat flux is directly dependent on its density, which is determined by the formula:

ς = α _Β ^χ ΔΤ ^Β (W / m ² ) (1), where

and „is the heat transfer coefficient of the cooled air, and ΔΤ ^Β is the gradient between the temperature of the cooled air and the temperature of the evaporator.

Under conditions of a free convention of cooled air, its heat transfer coefficient a „is 5–8 W / (m ·,), which provides a relatively low density and heat flux supplied to the evaporated refrigerant directly from the cooled air. According to (1), the density of the heat flux q supplied to the evaporated refrigerant is directly dependent on the temperature gradient ΔΤ ^Β . When the refrigeration unit is turned on after a long period of shutdown, the temperature of the air contained in the cavity of the refrigerating chamber is equal to the ambient temperature (for example, + 25 ° C), and the temperature gradient ΔΤ "reaches its maximum value of 35 - 40 degrees. Maximum ΔΤ ^Β provides the maximum density and value of the heat flux supplied to the evaporated refrigerant from the cooled air, while the cooling capacity of the refrigeration unit also reaches its maximum . imalnogo value equal to the maximum cooling capacity of the compressor However, after the refrigerator in the operating mode the average temperature contained in the cavity of the refrigerating compartment drops to + 5 ° C The value ΔΤ ^Β temperature gradient is reduced to 15 -. 20 degrees, and the density and the amount of the heat flux supplied to the evaporated refrigerant from the cooled air is reduced by a factor of 2–2.5, and the cooling capacity of the refrigeration unit is correspondingly reduced.

The low density of the heat flux supplied to the evaporated refrigerant directly from the cooled air is the main reason for the relatively low cooling capacity of the refrigeration unit. A direct consequence of the low cooling capacity of the refrigeration unit is an increase in the time it takes to complete one air cooling cycle.

An evaporator is known in the art for use in the refrigeration compartment of a BOSCH KGS 39V25 domestic refrigerator. Consider the evaporator described in patent DE 102004027706, as well as in patent RU 2 386 087 C2. The evaporator is an aluminum tube that is glued to the aluminum sheet and acts as an evaporation channel. Butyl rubber is used as an adhesive. To increase the area of contact between the tube and the plane of the aluminum sheet, the cross section of the tube is shaped like an ellipse. The evaporator in question is located in the rear wall of the refrigerator, while the aluminum sheet is glued to the facing panel of the refrigerator. The specified facing panel performs the function of a cooling surface with respect to the air contained in the cavity of the refrigerating chamber. Despite the cross-sectional shape of the evaporator tube, the area of its contact with the surface of the aluminum sheet is not more than 1 - 3% of the area of the evaporation channel. Therefore, the bulk of the heat is supplied to the evaporation channel through a layer of butyl rubber, which covers 40-50% of the outer surface of the tube. Butyl rubber is characterized by good adhesion and low permeability, which creates the necessary conditions for the transfer of heat from the aluminum sheet to the surface of the evaporation channel. The density of the heat flux supplied to the surface of the evaporation channel through the butyl rubber layer is directly dependent on its heat conductivity coefficient, the value of which is 0.091 ΒΤ / (Μ · Κ). The average thickness of the butyl rubber layer in the evaporator in question is 0.002 meters; therefore, its thermal conductivity does not exceed 45 W / (m ² -K), which is about 20 times less than the heat transfer coefficient of the evaporated refrigerant.

The relatively low thermal conductivity of the butyl rubber layer reduces the density and magnitude of the heat flux supplied to the evaporated refrigerant. This heat flow can be increased by increasing the length of the evaporation channel, and / or by lowering the temperature of evaporation of the refrigerant. In the evaporator in question, the length of the tube of the evaporation channel is more than 10 meters, but the area of its contact with the aluminum sheet and a layer of butyl rubber is still not large enough to provide the necessary amount of heat flow to the evaporated refrigerant. Therefore, in order to increase said heat flux, the temperature gradient between the cooling surface and the air being cooled is increased. An increase in the indicated temperature gradient can only be achieved by lowering the temperature of evaporation of the refrigerant, which in the considered evaporator is reduced to -25 ° C, which provides an increase in the heat flux supplied to the evaporated refrigerant. However, the value of the obtained technical result is reduced due to the fact that as the temperature of evaporation of the refrigerant decreases, the cooling capacity of the compressor decreases, which determines the cooling capacity of the refrigeration unit as a whole. In addition, a direct consequence of a decrease in the temperature of the evaporator is an increase in the heat flux supplied to the evaporated refrigerant from the environment through a thermal insulation layer with which the rear surface of the evaporator in contact is in contact. This reduces the amount of heat supplied to the evaporated refrigerant from the cooled air contained in the cavity of the refrigerating chamber, and accordingly, the operating time of the refrigeration unit is increased.

In addition, in the considered evaporator, the straight sections of the evaporation channel are located horizontally. Therefore, the evaporated refrigerant, which is a mixture of liquid and steam, can move along the horizontal sections of the evaporation channel only under the influence of the compressor, which limits the speed of movement of the liquid refrigerant through the vaporization channel. A direct consequence of the relatively low velocity of the liquid refrigerant is its intensive evaporation in the upper part of the evaporation channel, into which the liquid refrigerant enters from the condenser. The process of intensive evaporation of the refrigerant in the top part of the evaporator is stopped, when the evaporator temperature of the material decreased to a value close to the evaporation temperature of the refrigerant that provides the delivery of non-evaporable (liquid) refrigerant in the lower part of the evaporator. After turning on the refrigeration unit in the refrigerating chamber under consideration, the upper part of the evaporator is cooled to -15 ° С, and only after that the liquid refrigerant starts to flow to the lower part of the evaporator, the temperature of which at this time is + 4 ° С. Therefore, the cooling process of the lower part of the evaporator begins when the temperature of evaporation of the refrigerant is -20 ° C, which is below the optimal temperature of evaporation by at least 10 degrees. At the same time, a lower refrigerant vaporization temperature corresponds to a lower compressor cooling capacity. A direct consequence of the reduction in compressor cooling capacity is an additional increase in the operating time of the refrigeration unit, which is necessary for cooling the lower part of the evaporator, as well as for cooling the air contained in the lower part of the refrigerator.

Disclosure of invention

The claimed utility model is based on the task of creating an evaporator, the essential features of which provide a reduction in the amount of electricity consumed by the refrigeration device. The problem is solved by creating an evaporator containing a heat accumulator and a channel for evaporating the refrigerant made of steel or copper pipe, and according to a utility model, the heat accumulator is a metal plate, preferably made of cast aluminum, in the body of which there is a channel for evaporating the refrigerant the thickness of the plate sections located between the straight sections of the evaporation channel is less than the thickness of the plate sections located around the evaporative channel.

In the inventive evaporator, an accumulating substance is tightly in contact with the outer surface of the tube of the evaporation channel, which is cooled by heat exchange with the evaporated refrigerant. The storage material used is preferably aluminum or an aluminum alloy. The heat transfer coefficient of aluminum exceeds the heat transfer coefficient of the evaporated refrigerant a _x . Therefore, the density of the heat flux supplied to the evaporated refrigerant is defined as the product α _χ * ΔΤ, where ΔΤ is the gradient between the temperature of the storage substance and the temperature of evaporation of the refrigerant. The heat transfer coefficient of the evaporated refrigerant a _x can reach a value of 1000 W / (m ² -K), which is two orders of magnitude higher than the heat transfer coefficient of the cooled air, the value of which in the refrigerator does not exceed 5 - 8 ΒΤ / (Μ ² · Κ) . A high value of a _x provides a higher (compared with the prototype) the density of the heat flux supplied to the evaporated refrigerant. In this case, regardless of the temperature gradient ΔΤ, the heat flux supplied to the evaporated refrigerant will increase to a value equal to the maximum refrigerating capacity of the compressor.

In addition, a high value of a _x provides the maximum value of the heat flux supplied to the evaporated refrigerant, with a smaller (in comparison with the prototype) surface area of the evaporation channel. The reduction in the area of the evaporation channel is achieved by reducing its length. A direct consequence of reducing the length of the evaporation channel is a decrease in its hydraulic resistance. In this case, the ratio of the discharge pressure at which the compressor outlet valve opens to the suction pressure at which the compressor inlet valve opens, which accordingly ensures an increase in the useful volume of the compressor working cylinder, as well as a corresponding increase in its cooling capacity.

The increase in heat flow supplied in the inventive evaporator to the evaporated refrigerant, reduces the operating time of the refrigeration unit required to cool the evaporator plate to a predetermined temperature.

The operating time of the refrigeration unit is also directly dependent on the value of the heat flux - Q supplied from the cooled air to the storage substance. The value of the specified heat flux will be determined by the formula:

Q = S x a _in x ΔΤ ^Β (W) (2),

where S is the area of the side surface of the evaporator plate, which is a cooling surface with respect to the cooled air. In the inventive evaporator, the thickness of the plate sections located between the rectilinear sections of the evaporation channel is less than the thickness of the plate sections located around the evaporation channel, which provides an increase in the side surface area of the plate S with a constant mass of storage material. Moreover, in accordance with formula (2), the value of the heat flux Q also increases.

In addition, the value of the heat flux Q, is directly dependent on the temperature gradient ΔΤ ^Β . The value of the indicated temperature gradient increases as the temperature of the evaporator plate decreases, and the faster the temperature of the plate decreases, the higher the average value ΔΤ ^Β . Moreover, in accordance with formula (2), the average heat flux Q also increases. Most of the lateral surface of the evaporator plate consists of sections located between the straight sections of the evaporation channel. The cooling rate of these sections of the plate is directly dependent on their mass. Therefore, the smaller the thickness of the plate sections located between the straight sections of the evaporation channel, the faster their temperature decreases and the average heat flux Q increases.

The set of essential features of the claimed evaporator provides an increase in the heat flux supplied from the accumulating substance to the evaporated refrigerant, as well as an increase in the heat flux supplied from the cooled air to the accumulating substance. A direct consequence of the increase in these heat flows is a reduction in the operating time of the refrigeration unit required for cooling the evaporator plate, as well as reducing the operating time of the refrigeration unit, necessary for cooling the air contained in the cavity of the refrigerator.

In order to maximize the heat flux supplied to the vaporizing refrigerant, when the minimal length of the evaporation channel is necessary that the thickness of the plate portions located around the evaporating channel was equal at least to the diameter of the vaporization channel.

The proposed thickness of the plate sections located around the evaporation channel provides heat exchange of the evaporated refrigerant only with the aluminum of which the evaporator plate is made. Therefore, along the entire perimeter of the evaporation channel, the density of the heat flux supplied to the evaporated refrigerant will reach its maximum value, since its value will be determined by the heat transfer coefficient of the evaporated refrigerant. Therefore, the magnitude of the heat flux supplied to the evaporated refrigerant through the walls of the evaporation channel can reach a value equal to the maximum refrigerating capacity of the compressor, with a smaller area of the evaporation channel in comparison with the prototype. In addition, it is advisable to reduce the area of the evaporation channel by reducing its length, which reduces the hydraulic resistance of the channel. A direct consequence of the reduction in the hydraulic resistance of the evaporation channel is an increase in the cooling capacity of the refrigeration unit, and a corresponding reduction in the time it takes to cool the evaporator plate.

To further increase the compressor's cooling capacity, it is advisable that the declared evaporator contain straight sections of the evaporator channel located in the body of the evaporator plate with a slope, while the inlet of the channel is located in the upper part of the evaporator plate, and its outlet is located above the level of liquid refrigerant contained in the lower part of the evaporation channel after turning off the refrigeration unit.

The inlet of the evaporation channel is located in the upper part of the heat accumulator, and the straight sections of the channel are made with a slope. The slope of the straight sections provides an additional effect of gravity on the liquid refrigerant, which moves from top to bottom along the inclined channel at a higher speed compared to the evaporator of the prototype. Higher speed the movement of liquid refrigerant through the evaporation channel in combination with a shorter length of the specified channel creates the necessary conditions for a faster flow of liquid refrigerant to the lower part of the evaporation channel. Therefore, the process of evaporation of the refrigerant will be carried out simultaneously along the entire length of the evaporation channel, which ensures more uniform cooling of all parts of the evaporator plate compared to the prototype evaporator. In this case, the cooling process of the lower part of the evaporator plate can be carried out at a higher (in comparison with the prototype) value of the temperature of evaporation of the refrigerant, and a higher cooling capacity of the compressor corresponds to a higher temperature of evaporation of the refrigerant.

After turning off the refrigeration unit, all liquid refrigerant is displaced from the condenser into the cavity of the evaporation channel. The location of the inlet and outlet openings of the channel ensures after concentration of the refrigeration unit that all incoming refrigerant is concentrated in the lower part of the evaporation channel. After turning on the refrigeration unit, the cooling of the upper part of the heat accumulator will be carried out by evaporating the refrigerant entering the cavity of the evaporation channel through the capillary tube. At the same time, by evaporation of the refrigerant located in the lower part of the evaporation channel, the lower part of the evaporator plate will be cooled, which also provides more uniform cooling of all parts of the claimed evaporator compared to the prototype.

The industrial applicability of the claimed evaporator is ensured by the fact that for its manufacture technologies that are widely used in modern industry can be used. For example, the evaporator plate may be made by die casting or die casting. In addition, the use of the claimed utility model as an evaporator of a refrigeration unit does not require changes to the design of the refrigerator or refrigeration machine, which facilitates the implementation of the inventive evaporator.

Brief Description of the Drawings

For a more complete understanding of the essence of the utility model, the following is a description of the claimed evaporator with reference to the accompanying drawings, in which: FIG. 1 schematically depicts an evaporator made in accordance with a utility model;

FIG. 2 schematically depicts an embodiment of an evaporator made according to a utility model.

An embodiment of the invention

The claimed evaporator 1 (Fig. 1) is located in the rear wall of the refrigerator 2 and contains a metal plate 3, which is made by casting of aluminum or aluminum alloy. The plate body 3 is disposed a channel 4 for evaporating the refrigerant, which is a hollow copper tube or bstalnoy 5. The material of the plate 3 is formed, is in contact with the outer surface of the tube 5, which transmits heat from the plate material 3 through the tube wall 5 to the refrigerant vaporized in the cavity of the channel 4. The thickness of the sections of the plate 3 located between the straight sections of the tube 5 is less than the thickness of the sections of the plate 3 located around the tube 5. One of the side surfaces of the plate 3 is a plane st, which is in contact with the facing plate 6. In this case the thermal conductivity of the panel 6 exceeds the heat transfer coefficient of air located in the cavity 7.

The inventive evaporator shown in FIG. 2, contains an evaporation channel 8. Straight sections 9 of the specified channel are located with a slope. The inlet 10 of the duct 8 is arranged in the upper part of the plate evaporator 1 is 1, and its outlet 12 is situated above the level of the liquid refrigerant which after disconnection of the refrigeration unit is contained in the bottom of the channel 8. The thickness of the plate portions 13 a 1: 1 located between the rectilinear portions 9, less than the thickness of the sections of the plate 11 located around the evaporation channel 8.

The inventive evaporator, located, for example, in the rear wall 2 of the refrigerating chamber 7 (Fig. 1), operates as follows. When the temperature of the air contained in the cavity of the refrigerating chamber 7 rises to a predetermined value of + 10 ° C, the refrigeration unit is turned on and the plate 3 is cooled by the refrigerant vaporized in the cavity of the channel 4, while its temperature is lowered to -15 ° C. As the plate 3 cools, the heat transfer process between the cooled air and the plate material 3 begins. The air temperature decreases. The refrigeration unit is turned off when the temperature of the stove 3 is cooled to - 15 ° C. After turning off the refrigeration unit, the air cooling process continues. As the temperature of the plate 3 increases, the temperature gradient between the cooled air and the plate 3 will decrease, and accordingly, the amount of heat flow removed from the cooled air will decrease. When the value of the specified heat flux decreases to a value equal to the magnitude of the heat flux entering the cavity of the refrigerating chamber 7 from the environment, the temperature of the cooled air will reach its minimum value. Then, the temperature of the cooled air will increase under the influence of the heat supplied to it. In this case, part of the heat supplied to the air will be diverted to the material of the plate 3, which will increase the time interval necessary to increase the temperature of the air contained in the cavity of the refrigerating chamber 7 to a predetermined maximum value. Then, the refrigeration unit is turned on and the next process of cooling the stove 3 and the air contained in the cavity of the refrigerating chamber 7 is carried out.

Industrial applicability

The set of essential features of the claimed evaporator provides an increase in the density of the heat flux supplied to the evaporated refrigerant.

Claims

FORMULA OF A USEFUL MODEL.

1. Evaporator comprising heat accumulator and the refrigerant evaporation passage made of steel or copper pipes, characterized in that the heat accumulator consists of a metal plate, preferably made from aluminum by casting, which is located in the body passage for evaporating the refrigerant, the thickness sections of the plate located between the straight sections of the evaporation channel, less than the thickness of the sections of the plate located around the evaporation channel.

2. The evaporator according to claim 1, characterized in that the thickness of the sections of the plate located around the evaporation channel is equal to at least the diameter of the evaporation channel.

3. Evaporator according to claim 1 or 2, characterized in that it comprises rectilinear portions vaporization channel located in the body of the evaporator plate with slope, wherein the inlet channel is disposed in the upper part of the evaporator plate, and its outlet is situated above the liquid refrigerant level contained in the lower part of the evaporation channel after turning off the refrigeration unit.