KR101573592B1 - Cooling element for refrigerator - Google Patents

Abstract

The direct cooling and refrigeration system includes a freezer compartment 102 that includes a refrigerating compartment 101 and an evaporator plate 106 in contact with a plurality of coils or tubes 113 having a refrigerant circulating therein. A plurality of cooling devices are provided inside the refrigerator, and at least one of the cooling devices is in contact with the evaporator plate 106. The cooling device has a freezing point lower than 0 ° C and above the evaporator plate average temperature and includes a phase change material (PCM) surrounded by the elastic case 110.

Description

[0001] COOLING ELEMENT FOR REFRIGERATOR [0002]

The present invention relates to a cooling device for a refrigerator, and more particularly to a cooling device containing a phase change material for a direct cooling and refrigeration system.

The basic principle of an AC power refrigerator is that the inside of the refrigerator is made up of a (mechanical, electronic, or chemical) compressor that transfers heat from the inside of the insulated room and the refrigerator to the outside environment so that the inside of the refrigerator is cooled to a temperature lower than the ambient temperature of the room. Cooling is a popular food storage technology worldwide and works by reducing the rate of bacterial regeneration. Because bacteria are a major cause of food corruption, refrigerators help reduce food corruption.

The problem of blackout is very common in developing countries, and irregular power supplies lead to a drastic reduction in the cooling efficiency of the refrigerator. This negatively affects the quality of the perishable articles stored in the refrigerator cabinet due to poor cooling retention. If a power outage lasts for several hours, it will adversely affect the food stored in the freezing area. In the case of high power consumption or low voltage in the home, the refrigerator does not provide sufficient cooling for stored goods. Therefore, it is important to find a way to maintain cooling inside the refrigerator during situations such as high power consumption, low voltage, power failure, and the like.

One way to overcome this problem is to use phase change material (PCM) in the freezer compartment of the refrigerator. PCM has been used for many years to store latent heat through solid-solid, solid-liquid, solid-gas and liquid-gas phase transformations. However, the phase transformation used for PCM is solely solid-liquid phase transformation. The liquid-gas phase transformation has a higher thermal change than the solid-liquid phase transformation, but is not actually applied due to the high pressure involved. Several types of PCM can be used, such as eutectic mixtures, organic PCMs, inorganic PCMs, and the like.

For refrigerators adopting latent heat storage of PCMs, the cooling of the evaporator freezes the PCM when power is available. In the case of a power failure, the refrigeration cycle is stopped, and the evaporator plate does not have any cooling source. Therefore, the temperature inside the refrigerator starts to rise. However, due to the presence of frozen / partially frozen PCM, the rate of temperature rise is greatly reduced. Thus, the cooling potential of the PCM is used to cool the air inside the refrigerator and to maintain the article stored at sufficiently low temperatures. Generally acceptable temperatures are 0 ° C for refrigerated areas and 10 ° C for refrigerated areas. If the temperature rises above the allowable temperature for a long period of time, the stored product will be destroyed.

However, existing methods face at least one or more problems. For example, if the freezing point of the PCM is too low, it can not be frozen completely. If the freezing point of the PCM is too high, the PCM is completely frozen but has a very low cooling potential in terms of latent heat. Therefore, it is important to use PCM with freezing point within the correct temperature range according to the average plate temperature of the evaporator.

Another problem in existing methods is that the PCM is provided in a hard plastic case / housing. Thus, the thermal resistance between the PCM and the evaporator plate is high. In addition, the contact area between the PCM and the evaporator plate is not sufficient to slow the freezing of the PCM and / or cause high energy consumption during power availability. Likewise, in the case of a power failure, the cooling provided by the PCM is very slow. It is therefore important to provide a high contact area and low thermal resistance between the PCM case and the evaporator plate.

European Patent No. 152155 discloses a number of cooling storage devices for chest freezers, each comprising a case made of a plastic material containing a eutectic solution, for example polyethylene. In particular, the storage device can be used in such a way that the eutectic solution is frozen by virtually continuous operation of the compressor during the time (night) during which the charge of the main power is reduced. The heat energy stored by such a device is utilized during the time (day) during which the charge of the main power is at its maximum, avoiding the operation of the refrigerator compressor during this time. However, due to contact of the unsuitable area, the compressor must be operated continuously to freeze the PCM. Moreover, since the cooling storage devices must be aligned with one another by bonding, the case must be thick and rigid to lead to high thermal resistance.

It is an object of the present invention to avoid or alleviate the aforementioned disadvantages.

According to one embodiment of the present invention, there is provided a direct cooling refrigeration system comprising a refrigerating chamber and a freezing chamber comprising an evaporator plate in contact with a plurality of coils or tubes having a refrigerant circulating therein, Wherein at least one of the cooling devices is in contact with the evaporator plate, the cooling device has a freezing point of less than 0 ° C and the evaporator plate has an average temperature higher than the average temperature, and the phase change material PCM). ≪ / RTI >

According to another embodiment of the invention, the flexible refrigeration system is characterized in that the flexible case comprises at least a pair of thin, flexible, spaced apart walls joined together to form a closed surface to provide.

According to another embodiment of the present invention, the flexible walls increase the area of the flexible case in contact with the evaporator case in conformity with the shape of the evaporator plate.

According to another embodiment of the present invention, there is provided a direct cooling refrigeration system characterized in that said flexible walls are thin.

According to still another embodiment of the present invention, there is provided a cooling system, further comprising a fresh room or TFR having another cooling device disposed therein, wherein the cooling device has a freezing point higher than the minimum reaching temperature inside the TFR, Or a phase change material surrounded by a flexible case.

According to another embodiment of the present invention, the rigid case comprises at least a pair of rigid, mutually spaced walls joined together.

According to another embodiment of the present invention, the apparatus further includes a support case (108) disposed inside the evaporator plate and in contact with at least one wall of the elastic case (110), wherein the support case And means for controlling the temperature of the refrigerant.

According to another embodiment of the present invention, the cooling device (s) are divided into a plurality of zones.

According to a further embodiment of the present invention, the evaporator plate is characterized in that the evaporator plate comprises a metal sheet comprising one surface folded into any desired shape, a metal sheet comprising two surfaces having an L shape, a U- A metal sheet having three sides, a metal sheet having three sides, four sides having an O shape, or a metal sheet having more sides.

According to another embodiment of the present invention, the support case may have one surface spaced apart from the sides / surfaces of the evaporator plate, or may have two surfaces formed in an L shape, or U The present invention provides a direct cooling and refrigeration system having four sides or more surfaces that are formed in an O shape.

According to another embodiment of the present invention, the support case has three surfaces (U-shape), and the cooling device is in contact with one or more surfaces of the support case. to provide.

According to another embodiment of the present invention, the phase change material (s) in the cooling device (s) are partly or completely frozen during normal operation of the refrigeration system and provide cooling during power interruption / Lt; RTI ID = 0.0 > refrigeration < / RTI >

According to another embodiment of the present invention, the phase-change material is any organic or inorganic PCM or eutectic solution having a freezing point within a given temperature range.

According to another embodiment of the present invention, the elastic case is made of a plastic material such as polyvinyl chloride (PVC), polypropylene, polyethylene, polystyrene, acrylonitrile butadiene styrene (ABS) Cooling and refrigeration system.
According to another embodiment of the present invention, an evaporator plate having a plurality of tubes or coils attached to a surface thereof; A support case disposed in an inner space of the evaporator plate; And a stretchable case which is seated on the support case and is disposed in a space between the evaporator plate and the support case and has a phase change material (PCM); And attachment means for fixing the position of the elastic case seated on the support case.
The elastic case seated on the support case can contact the evaporator plate.
The attaching means includes at least one protrusion formed on the support case, and at least one receptacle formed in the flexible case, in which the at least one protrusion is received.
The support case includes an upper wall and first and second sidewalls extending downward from both sides of the upper wall, and the flexible case is in contact with the upper wall, the first sidewall and the second sidewall.
The elastic case includes a first case seated on the upper wall, a second case contacting the first side wall, and a third case contacting the second side wall.
The at least one projection is formed in the upper wall, and the at least one receiving portion is formed in the first case.
The first case and the third case are independently connected to each other by a first connection part and the first case and the third case are connected by a second connection part .
The evaporator plate has three or more surfaces facing the first case to the third case.
A plastic case of a hard, semi-rigid or stretchable material disposed on one side of the evaporator plate and having a phase change material, and a tray fresh chamber on which the plastic case is seated.
The surface of the support case facing the plastic case includes an opening.
The phase change material is organic or inorganic PCM or eutetics with freezing points within a given temperature range.
The flexible case is made of a plastic material such as polyvinyl chloride (PVC), polypropylene, polyethylene, polystyrene, acrylonitrile butadiene styrene (ABS), or nylon.
According to another embodiment of the present invention, an evaporator plate having a plurality of tubes or coils attached to a surface thereof; A flexible case disposed in an inner space of the evaporator plate and having a phase change material (PCM); And a support case for supporting the elastic case in an inner space of the evaporator plate.
The support case includes an upper wall and first and second sidewalls extending downward from both sides of the upper wall, wherein the elastic case includes a first case seated on the upper wall, A second case in contact with the first side wall, and a third case in contact with the second side wall.
According to another aspect of the present invention, there is provided a food processing apparatus comprising: a storage chamber defining a space for storing food; An evaporator plate disposed in the storage chamber and formed by bending plate-shaped plates; A support case disposed in a space defined by the evaporator plate; A case of a soft material which is seated on the support case and is disposed between the evaporator plate and the support case and incorporates a phase change material therein; A through hole penetrating the case of the soft material; And a protrusion formed on the support case, the protrusion being coupled to the through hole to prevent the flow of the case of the soft material.

The present invention provides a cooling device for a refrigerator that contains PCM with freezing point within a desired temperature range and achieves complete freezing of PCM during normal operation. Moreover, the cooling device is designed to have a high contact area and low thermal resistance between the PCM and the evaporator plate. This cooling system, which contains the proper PCM, can deliver maximum heat between the evaporator and the cooling storage medium through the use of a flexible PCM case. Thus, in the case of power failure, high power consumption or low voltage, a sufficiently low temperature is maintained in the furnace for a long time. The cooling system can also reduce the amount of PCM required. The efficient use of cooling provided to the refrigerator during normal operation also reduces the operating cost of the refrigerator.

1 (a) is a front view of a direct cooling and refrigeration system according to an embodiment of the present invention.
1 (b) is a perspective view of a freezer compartment and a tray fresh room (TFR) according to an embodiment of the present invention.
1 (c) is an exploded perspective view of a freezing chamber and a tray fresh room according to an embodiment of the present invention.
2 (a) is a perspective view showing the attachment of the elastic plastic case to the upper side of the support case.
2 (b) is a view of a flexible plastic case according to an embodiment of the present invention.
Fig. 2 (C) is an enlarged view of the TFR of Fig. 1 (b) with a hard plastic case embedded therein.
Figure 3 shows a temperature versus time graph for freezing two phase change materials (PCMs) having freezing points of -12 [deg.] C and -5 [deg.] C.
4 is a temperature versus time graph for freezing a PCM with freezing point of -12 [deg.] C by the cycle operation of the refrigerator.
5 (a) is a perspective view showing a hard plastic case containing a PCM in contact with an evaporation plate of a freezing chamber.
5 (b) is a view showing a section taken along the line A-A 'of FIG. 5 (a) showing a part of the evaporator plate, the hard plastic case, the PCM and the freezing chamber.
Fig. 5 (c) is an enlarged view of the enclosed portion of Fig. 5 (b).
6 (a) is an enlarged sectional view showing a part of an evaporator plate, a hard plastic case and a PCM.
Figure 6 (b) is a schematic diagram showing the thermal resistance provided by the components of Figure 6 (a).
Fig. 6 (c) is a schematic diagram showing the relationship between the thermal resistances in Fig. 6 (b).
Figure 7 is also a diagram showing the response of (UA) ₂ , which also changes some parameters.
Figure 8 (a) is a schematic view showing a hard plastic case in contact with an evaporator plate.
8 (b) is a schematic view showing a stretchable plastic case in contact with an evaporator plate.
9 is a temperature versus time graph for freezing the same PCM in a flexible plastic case and a hard plastic case.
It should be noted that the above-mentioned drawings refer to a direct cooling refrigerator. However, the teachings of the present invention can be applied to other types of refrigerators with or without some modification.

Some representative embodiments of the present invention are disclosed below. In its broader aspects, the invention is not limited to the specific details, representative apparatus and methods, and illustrative embodiments shown and described in connection with the embodiments and methods herein. The invention in its various aspects is particularly pointed out and distinctly claimed in the appended claims and their equivalents in light of the present disclosure.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Throughout this specification, the term "x ° C phase change material (PCM)" refers to a phase change material (PCM) having freezing / melting points at x ° C, where "x" to be.

A number of PCM's at any point in the temperature range of -5 [deg.] C to 190 [deg.] C may be used. PCM useful for domestic refrigerators generally has a freezing point below 0 ° C. The effects of PCM can be judged based on thermodynamic, kinetic, economic and chemical characteristics. An important prerequisite is that the melting temperature should be within the operating range of the refrigerator. Two important factors in determining the effect of PCM in a refrigerator are the time taken to completely freeze the PCM and the amount of sensible heat and latent heat stored during the phase transformation.

1 (a) is a front view of a local natural convection or single door or direct cooling and refrigeration system 100 according to an embodiment of the present invention. The freezing chamber 102 is located above the refrigerator. The temperature inside the freezer is maintained at a lower temperature than any point in the water to form ice or provide freezing storage of other items. The tray draw chamber or TFR (103) is disposed directly below the freezer compartment. The temperature in the freezer compartment is generally close to some point in the water. Thus, the articles that are cooled to a low temperature, but preferably not frozen, are stored in this area. The main refrigerator compartment 101 includes a plurality of trays for placing food or other items. The temperature in this zone is maintained at a temperature slightly lower than the ambient temperature. The bottom portion of the refrigerator may have a vegetable storage tray 105 for storing fresh fruits and vegetables.

1 (b) is a perspective view of the freezing chamber 102 and the TFR 103 shown in FIG. 1 (a), and FIG. 1 (c) is an exploded perspective view of a freezing chamber and a tray fresh room according to an embodiment of the present invention . The refrigerator includes an evaporator plate 106 that provides cooling to the entire refrigerator and a frame of the evaporator 107 that fixes the temperature regulator, the bulb, and the refrigerator door. The support case 108 for fixing the elastic plastic case is disposed inside the freezing chamber 102. The PCM is stored in a flexible plastic case disposed in a space between the evaporator plate and the support case. Therefore, the support case 108 prevents the elastic plastic case containing the PCM from being damaged. It also prevents the stretchable plastic case from stretching or protruding with its own weight, which occurs when large amounts of PCM are stored within them. Another PCM or the same PCM is disposed inside the TFR (103). The PCM placed inside the TFR is stored in a flexible plastic case or a hard plastic case.

Fig. 2 (a) is a perspective view showing the attachment of the elastic plastic case 110 to the upper side of the support case 108. Fig. The PCM is stored inside the elastic plastic case. In the present embodiment, the support case has three sides bent in a U-shape. Therefore, one side of the support case is opened by the opening. At this time, the surface on which the opening is formed is a surface facing the plastic case 109 to be described later. Two of the three planes are parallel to each other and perpendicular to the third plane. In order to prevent warping of the support case, a strip 117 is provided between two parallel sides. Therefore, the articles to be stored inside the freezer are surrounded by the support case. The support case 108 is an attachment means in the form of a plurality of projections 111 formed or formed on the support case so that the elastic plastic case can be pressed or attached thereto.

FIG. 2 (b) is a view of a flexible plastic case 110 having three configuration zones for storing a PCM according to an embodiment of the present invention. The spaces have a small gap therebetween to accommodate the corners of the support case 108 when the support case 108 is placed thereon. These three sides complement the corresponding sides of the support case 108 in which they are placed. A plurality of through holes 112 (also referred to as receptacles) may also be provided to allow the protrusions 111 of the support case to be intimately pressed or attached thereto. In this case, a portion of the stretchable plastic case that is seated on the upper surface of the support portion case may be referred to as a first case, and a portion located on both sides of the support portion case may be referred to as a second case and a third case. The portion connecting the first case and the second case may be referred to as a first connecting portion, and the portion connecting the first case and the third case may be referred to as a second connecting portion. Therefore, the second case and the third case can be bent from the first case by the respective connecting portions.

Fig. 2 (c) is an enlarged view of the TFR 103 in Fig. 1 (b). The PCM can be stored in a rigid, semi-rigid or flexible case inside the TFR. And is stored in the hard plastic case 109 in this embodiment. The case is divided into a number of zones to facilitate faster freezing of the PCM. The hard plastic case 109 is disposed inside the TFR 103, and can be detached or removed as needed. This acts as an additional cooling source during power outage and also helps prevent the temperature rise of the refrigerating chamber 101. [

Figure 3 shows a temperature versus time graph for the freezing of two PCMs having freezing points of -12 [deg.] C and -5 [deg.] C. At ambient temperature (approximately 30 ° C), the liquid PCM is attached to the evaporator plate, and the compressor operates continuously. Due to the continuous operation of the compressor, the temperature of the evaporator plate is lower than -30 ° C. The PCM is frozen at different times and is further cooled to a solid state at approximately -30 ° C. The graph clearly shows that the PCM with low freezing point shows a longer completion time for phase transformation. Therefore, -12 ° C PCM emits more heat before freezing than -5 ° C. In the case of blackout, the -12 ° C PCM is expected to perform better because it can absorb more heat before melting than the -5 ° C PCM. It can be concluded that the PCM with longer completion time for phase conversion can store more cooling potential or latent heat (ignoring sensible heat).

4 is a temperature versus time graph for freezing PCM with freezing point of -12 [deg.] C by cycle operation in a direct cooling refrigerator. The cycle is a general mode for operating a direct refrigerated refrigerator wherein the compressor is operated on and off cycles to allow the evaporator plate temperature to increase and decrease between any set temperatures. The same is shown by the notches in the evaporator plate temperature graph. When the PCM is attached to the evaporator of the direct cooling refrigerator, the PCM is frozen by fixing the heat to the evaporator plate. On the other hand, the evaporator plate is cooled by emitting heat to the refrigerant flowing through the plurality of tubes or coils attached to the evaporator plate. The refrigerant enters the tube at a low temperature, but is discharged at a higher temperature because it receives heat from the evaporator plate. Thus, temperature differences may occur somewhat in various portions of the evaporator plate. Thus, the temperature profile of the PCM placed in contact with other parts of the evaporator plate may vary.

When the notch is in the normal position, the average temperature of the evaporator plate is -13 ° C. The graph showing the temperature of the PCM shows that the temperature varies within a narrow temperature range. It can be seen that PCM with freezing point of -12 ° C can not be completely frozen when the average temperature of the evaporator plate is -13 ° C. Therefore, the melting point of the PCM attached to the evaporator should be higher than -12 ° C. Direct cooling method For a normal notch cycle of a refrigerator, the average temperature of the TFR is -1.5 ° C. Therefore, the melting point of the PCM placed in the TFR should be greater than -1 ° C. Thus, PCM with a melting point between -12 ° C and 0 ° C is effective in the freezer, and PCM with a freezing point above -1 ° C is particularly effective in the TFR of this particular direct cooling refrigerator.

5 (a) is a perspective view of a direct evaporator plate 106 according to one embodiment of the present invention. The cooling plate is essentially a metal sheet bent into a suitable shape with a plurality of tubes or coils 113 attached to its surface. In the given example, we have a tube network on four sides. The refrigerant flows into the tube from one end and flows out from the other end to collect heat in the above process. The hard plastic case 116 is disposed to contact one of the sides of the evaporator plate 106.

5 (b) is a view showing a section taken along the line A-A 'of FIG. 5 (a) showing a part of the evaporator plate, the hard plastic case, the PCM and the freezing chamber. The evaporator plate portion 115 has several tubes 113 passing therethrough. The refrigerant passes through these tubes and collects heat from the evaporator plate to lower its temperature. The cooled evaporator plate operates as a cooling source inside the freezer. Thus, the air inside the cooler loses heat or is cooled by the evaporator plate. A hard plastic case 116 containing a PCM disposed adjacent to the evaporator plate portion 115 can be seen as a pair of parallel walls 104 and 114 with a PCM 120 disposed therein . The wall 104 is adjacent to the evaporator plate portion 115 and may have several air gaps because it is not stretchable. The second wall 114 may contact the support case or may be in direct contact with the air inside the refrigerator.

Fig. 5 (c) is an enlarged view of the enclosed portion of Fig. 5 (b). The arrows in the given figure show the flow direction of the column. Q ₁ represents the heat flow from the interior of the refrigerator to the PCM 120. Q ₂ represents the heat flow from the PCM 120 to the evaporator plate 115. Thus, heat flows from the interior of the refrigerator to the evaporator plate.

In order to theoretically determine which of the PCM's is appropriate, energy balancing for the freezer can be performed. Energy balance is provided in the embodiment shown in Figures 5 (a), (b) and (c) during the phase transformation operation of the PCM. It can be assumed that the amount of hypochlorite consumed and released during the phase transformation is consumed when the temperature of the PCM changes in the solid or liquid state and is much higher than the sensible heat released. For example, during freezing of the PCM, the heat released to cool the PCM from the liquid to the liquid at the freezing point at ambient temperature, compared to the heat released during the phase transformation from the liquid at any point to the solid at that freezing point It can be assumed that it is insignificant enough to be neglected. Likewise, the sensible heat emitted to cool the solid PCM lower than its freezing point is also insignificant compared to the heat released during the phase transformation.

The freezing rate of the PCM stored in a hard plastic case placed in direct contact with the evaporator in the refrigerator is determined according to the following energy balance equation: Small position changes at the temperature of the evaporator plate can also be ignored. As used herein, the term " cabinet " refers to the interior of the refrigerator. It can be assumed that the cabinet is empty, i. E. No food or other items are placed in the cabinet.

The freezing rate of the PCM stored in the hard plastic case arranged to contact the evaporator in the direct cooling refrigerator is determined according to the energy balance equation.

……(1)

... ... (One)

here,

Q ₁ : Absorption rate of heat by PCM from cabinet

Q ₂ : Heat release rate from PCM to evaporator

m: mass of PCM

h _sf : latent heat of PCM

t: Phase change time

Heat absorbed from the cabinet (Q _One ):

……(2)

... ... (2)

here,

(UA) ₁ : product of total heat transfer efficiency and heat transfer area for heat absorption by PCM from cabinet

A ₀ : area of hard plastic case in contact with refrigerator cabinet

T _F : Average temperature of the cabinet

T _PCM : Freezing point of PCM

h _i : convection heat transfer efficiency

k _rp : thermal conductivity of hard plastic case

t _rp : thickness of hard plastic case

R _{1, th} : Equivalent thermal resistance for heat absorption from the cabinet

Here, it is assumed that the cabinet temperature is kept constant throughout the phase transformation of the PCM. The temperature of the PCM is regarded as a freezing point since the temperature changes very little during the phase transformation, as shown in Fig.

It was also assumed that there was no significant positional change in the temperature of the PCM or the temperature of the cabinet. Thus, TF and TPCM mean the mean temperatures inside the freezer and PCM, respectively.

Heat released to the evaporator (Q ₂ )

6 (a) is an enlarged cross-sectional view showing a portion of the evaporator plate 115, the hard plastic case 116, and the PCM 120. Q ₂ represents the heat flow from the PCM 120 to the evaporator plate 115. The thickness and thermal conductivity of the evaporator plate, air, hard plastic case and PCM are categorized in the figure. Some thermal resistances can be sealed during heat transfer from the PCM to the evaporator plate. The formula of Q ₂ can be derived as:

A _i = A ₁ + A ₂ , r = A ₂ / A _i (area ratio)

R _c : Thermal contact resistance

here,

(UA) ₂ : product of total heat transfer efficiency and heat transfer area for heat release from PCM to evaporator

A _i : total available area of the evaporator plate

A1: area of the evaporator plate not contacting the hard plastic case

A ₂ : area of the evaporator plate in contact with the hard plastic case

T _Eva : Average temperature of the evaporator plate

k _rp , k _air , k _Eva , k _PCM : Thermal conductivity of hard plastic case, air, evaporator plate material, PCM

R _{2, th} : Equivalent thermal resistance for heat release from the PCM to the evaporator.

Figure 6 (b) is a schematic diagram showing the thermal resistance provided by the components of Figure 6 (a). The resistance R ₁ means the total heat resistance for heat transfer through the area A ₁ not in contact with the hard plastic case. It comprises thermal resistance provided by the corresponding area of the hard plastic case which is not in contact with the thermal resistance of the air, and the area (A ₁₎ of the evaporator between the evaporator plate area (A1) heat resistance, an evaporator plate and a hard plastic case.

The resistance R ₂ means the total heat resistance for heat transfer through the area A _{2 in} contact with the hard plastic case. The thermal resistance of the evaporator plate area A ₂ , the thermal resistance provided by the area A ₂ of the hard plastic case in contact with the evaporator, and the thermal contact resistance between the evaporator plate and the hard plastic case. The thermal contact resistance (R _c ) is very small compared to the other two conditions included in the calculation. Therefore, it was ignored in other calculations. The resistance (R ₃ ) refers to the thermal resistance to heat transfer through the PCM based on the width of the PCM enclosed within the rigid plastic.

The total heat resistance (R _{2, th} ) was calculated based on the combination of the resistances shown in FIG. 6 (C). Fig. 6 (c) is a schematic diagram showing the relationship between the thermal resistances in Fig. 6 (b). The resistors R ₁ and R ₂ are parallel to each other and their combination is in series with the resistor R ₃ . It is clear from the obtained equation that the thermal resistance can increase with increasing width of PCM. For a given heat transfer area, reducing the amount of PCM can reduce the width of the PCM enclosed within the layers of hard plastic, thereby reducing thermal resistance to heat transfer.

Example 1: The experiment was run for a direct cooling refrigerator with a steel evaporator plate. A PCM with a thermal conductivity of 0.5 W / mK was used. A ₀ is considered equal to A ₁ , but in practice it may be slightly higher. 8 (a) is a schematic view showing a hard plastic case 116 in contact with an evaporator plate. The areas of the evaporator plate contacting the hard plastic case are classified as A ₂ . For a rigid plastic case, it would be reasonable to assume an areal ratio (A ₂ / A ₁ ) of 0.5, which means only half of the area of the hard plastic case that is in direct physical contact with the evaporator plate. In practice, the area ratios are lower than 0.5 for rigid plastic cases because of the spaced tubes or coils.

The values for the various variables used in the calculation of (UA) ₁ and (UA) ₂ were found as follows.

h ₁ = 8 W / m 2 k k _steel = 70 W / mK

t _rp = 2.5 mm k _air = 0.26 W / mK

k _rp = 0.1 W / mK k _rp = 0.1 W / mK

A ₀ = 0.037 m 2 k _PCM = 0.5 W / mK

t _steel = 0.55 mm

t _air = 1.4 mm

t _rp = 2.5 mm

t _PCM = 17 mm

A ₁ = 0.0185 m 2

A ₂ = 0.0185 m ₂

A _i = 0.037 m 2

r = 0.5

By substituting these values, we get

(UA) ₁ = 0.247 W / K,

(UA) ₂ = 0.514 W / K

The parameters associated with Q ₁ (heat absorption from the cabinet) affect both latent heat storage (LHS) and electrostatic performance, i. E., Performance during power outage. Because the evaporator does not have any cooling source during power outage, it exchanges only a small amount of heat with the ambient environment during power outage. This is very small compared to the heat treated by PCM before melting and can be ignored. Thus, during power outage, heat transfer from the chiller cabinet to the PCM plays an important role, and thus the rate of heat absorption (Q ₁ ) from the inside of the chiller is an important factor in the refrigerator's electrostatic performance. Parameters related to Q1 are h is _1, t _rp, k, and _rp A _0. For a given value of A ₀ , the thickness of the plastic case is a very important feature that can be controlled by the designer. The use of hard plastic limits the thickness reduction of the case. However, if flexible plastics such as PVC are used, the thickness can be reduced to a large extent.

The parameters associated with Q ₂ (heat uptake to the evaporator) are important only during latent heat storage, that is, only when the PCM is frozen. Sensitivity analysis was performed for various factors affecting (UA) ₂ of the equation obtained from equation (3). The results are graphically represented in FIG. The hard plastic case of Example 1 is considered as the base case, where (UA) ₂ is 0.514 W / K. As expected, a direct relationship is observed with the heat transfer area or the area (A _i ) of the evaporator plate. A 10% increase in evaporator plate increases by 10% (UA) ₂ . For a given evaporator plate area, the contact area of the PCM case and the thickness of the PCM are important reaction factors in the sensitivity analysis.

It is possible to extend the contact area between the evaporator and the PCM case and to reduce the thickness of the PCM by using a flexible plastic case. The thickness of the elastic plastic case is less than 90% less than the hard plastic case, and its elasticity increases the contact area.

Example 2: The rigid plastic case in Example 1 was replaced with a flexible plastic case. The conductivity of hard and stretch plastics can be considered the same. Case thickness is reduced by 90% by stretch plastic. Due to the reduced thickness of the case and the increased stretchability, the area of contact between the evaporator plate and the case increases. 8 (b) is a schematic view showing a stretchable plastic case 110 in contact with an evaporator plate. As can be seen from the figure, the stretchable plastic can closely follow the shape of the evaporator plate, and a large portion of the case is in direct contact with the evaporator plate. Only small portions of the evaporator plate classified as A ₁ do not contact the hard plastic case. Therefore, it is reasonable to assume that the area ratio r = 0.8.

Substituting in equation (3)

t _fp = 0.25 mm

r = 0.8

A ₁ = 0.0074 m ₂ , A ₂ = 0.0296 m ₂ , A _i = 0.037 m ₂

here,

t _fp : thickness of elastic plastic case

(UA) _{2 '} = 0.997 W increased by 94% over the value (UA) ₂ = 0.514 W / K obtained in Example 1 (assuming that the same energy balance is actually present / K can be obtained. Thus, by using the flexible plastic case of Example 2, the heat release from the PCM to the evaporator plate increases nearly twice.

Figure 9 is a temperature vs. time graph for freezing the same phase change material in a flexible plastic case and a hard plastic case. You can see which point is reached faster in the elastic plastic case. The completion time for phase conversion in the elastic plastic case is also less. In all examples, the temperature of the flexible plastic case is lower than the hard plastic case due to better heat transfer. Thus, for the same amount of PCM, the freezing time is reduced by almost two-thirds by using a flexible plastic case.

This should allow the designer to choose between better electrostatic performance and faster PCM freezing. If the PCM has very high latent heat storage characteristics, it will be able to provide long term cooling during power outage, and electrostatic performance will be better. However, it takes a lot of time and energy to completely freeze these PCMs, which may not be possible in the case of frequent outages. On the other hand, if the PCM has low latent heat storage characteristics, it will be able to provide cooling for a limited time after power outage, and electrostatic performance will not be very good. However, this PCM can be completely frozen faster. In this method using PCM in the refrigerator, complete freezing is achieved due to low latent heat storage and at the same time low contact area and high heat resistance of the PCM case and / or very large amounts of PCM to be frozen and / or improper freezing of PCM Sometimes it is not possible.

Thus, the present invention provides a direct cooling refrigerator with at least one cooling device enclosing a flexible or rigid plastic case provided in at least one location inside the refrigerator, and in particular comprising a phase change material having a suitable freezing point. The refrigerator provides excellent electrostatic performance and at the same time guarantees quick freezing of PCM stored in them.

Several modifications are possible within the scope of the present invention. For example, the PCM in the TFR may also be provided inside the elastic plastic case. Elastic and rigid plastic cases have any suitable number of zones. If desired, the PCM may be additionally provided at other locations inside the refrigerator. The support case may or may not be present. It is noted that the terms " elastic plastic " and " hard plastic " are not limited to plastics, but may be any material having similar characteristics to elastic and hard plastics. Some suitable elastic plastics include polyvinyl chloride (PVC), polypropylene, polyethylene, polystyrene, acrylonitrile butadiene styrene (ABS), nylon and the like. The shapes of the various components can also be modified as needed. For example, if the evaporator plate is L-shaped instead of a hollow rectangular parallelepiped, the PCM case may also be provided in a similar configuration that approximates one or more surfaces on which the evaporator plate is present. This is because it is difficult to completely freeze the PCM if the PCM is placed on the other side of the inside of the refrigerator where the evaporator plate is not in direct contact with the PCM. Likewise, the shape of the support case is also determined based on the shape of the evaporator plate and / or the PCM case. For example, if the evaporator plate is U-shaped, that is, if any one of the surfaces is removed from the evaporator plate 106 of Figure 5 (a), the support case may also have three similar surfaces , The PCM case may be provided in contact with at least one side of the evaporator plate. Any suitable means may be used to attach the PCM case to the support case.

The present invention is not limited to the embodiments described and illustrated by way of example, and various changes and modifications may be suggested without departing from the scope of the appended claims. The teachings of the present invention may be applied to other types of refrigerators, refrigerators, and refrigerator shelves, with or without minor modifications.

100. Direct cooling system
101. Refrigerator
102. Freezer
103. Tray fresh room (TFR)
104 and 114. The walls of the hard plastic case
105. Vegetable storage tray
106. Evaporator plate
107. Evaporator frame
108. Support case
109. Hard Plastic Case for TFR
110. Elastic plastic case
111. Protrusions on the support case
112. Through holes in the elastic plastic case
113. Tubes or coils
115. Evaporator plate section
Hard plastic case for refrigerator
117. Support Case Strip
120. Phase change material (PCM)

Claims (14)

A storage room forming a space for storing food;
An evaporator plate disposed in the storage chamber and formed by bending plate-shaped plates;
A support case disposed in a space defined by the evaporator plate;
A case of a soft material which is seated on the support case and is disposed between the evaporator plate and the support case and incorporates a phase change material therein;
A through hole penetrating the case of the soft material; And
And a protrusion formed on the support case, the protrusion being coupled to the through hole to prevent the flow of the case of the soft material. The method according to claim 1,
And the case of the soft material seated on the support case contacts the evaporator plate. The method according to claim 1,
The support case includes an upper wall and first and second sidewalls extending downward from both sides of the upper wall,
And the case of the soft material is in contact with the upper wall, the first side wall and the second side wall. The method of claim 3,
The case of soft material includes a first case to be seated on the upper wall, a second case to be in contact with the first side wall, and a third case to be in contact with the second side wall. 5. The method of claim 4,
The protrusion is formed on an upper wall of the support case,
And the through-hole is formed in the first case. 5. The method of claim 4,
The phase change material is independently accommodated in each of the first case to the third case,
The first case and the second case are connected by a first connecting portion,
And the first case and the third case are connected by a second connection portion. 5. The method of claim 4,
Wherein the evaporator plate has three or more surfaces facing the first case to the third case. delete The method according to claim 1,
A plastic case of a hard, semi-rigid or stretchable material disposed on one side of the evaporator plate and having a phase change material,
And a tray fresh room on which the plastic case is seated. 10. The method of claim 9,
And a surface of the support case facing the plastic case includes an opening. 10. The method of claim 1 or 9,
Wherein the phase change material is organic or inorganic PCM or eutetics having freezing points within a given temperature range. The method according to claim 1,
The case of the flexible material is made of a plastic material such as polyvinyl chloride (PVC), polypropylene, polyethylene, polystyrene, acrylonitrile butadiene styrene (ABS), or nylon. delete delete

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