JPH08254385A - Defrosting method for refrigerated showcases - Google Patents

Abstract

(57) [Summary] [Purpose] During defrosting, the evaporator itself functions as a heat siphon, and heat is applied to the evaporator from the high temperature side of the refrigerant circuit of the refrigerator to allow efficient defrosting. Provide defrosting method. An electromagnetic valve 13 is provided in a refrigerant pipe 12 on the inlet side of the evaporator 8, and a refrigerant pipe 14 on the outlet side is branched from a high temperature side pipe line between a compressor 5 and a condenser 6 of a refrigerator. The hot gas pipe 16 that has been drawn out is connected via the three-way valve 15, and the solenoid valve 13 on the evaporator inlet side is closed during defrosting,
The three-way valve is switched so that the outlet of the evaporator leads to the hot gas pipe. In this state, the evaporator is made to function as a heat siphon, and the frost is melted by the latent heat of condensation of the high-temperature refrigerant gas flowing into the evaporator from the high temperature side pipe through the hot gas pipe, and the refrigerant liquid condensed and liquefied in the evaporator is on the high temperature side. Defrosting is repeated by repeating the evaporation / condensation cycle so that it is returned to the pipeline and evaporated again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting system for a cold air circulation type freezing / refrigerating showcase.

[0002]

2. Description of the Related Art First, FIG. 3 shows the structure of a two-layer air curtain type multi-stage open showcase as a cold air circulation type freezing / refrigerating showcase to which the present invention is applied. In the figure, 1 is a front open type case main body, 2 and 3 are an inner ventilation duct and an outer ventilation duct which are formed between an outer box and an inner box of the case main body 1 to surround an internal display room,
The inner ventilation duct 2 has a compressor 5 of a refrigerator, a fin tube type evaporator 8 connected to a condenser 6 through an expansion valve 7, and an inner ventilation fan 9, and the outer ventilation duct 3 has outer ventilation. A fan 10 is provided. Reference numeral 11 denotes a product display shelf provided in the product display room 4.

With such a configuration, during the cold insulation operation (the compressor 5 and the blower fans 9 and 10 are operated), a cool air curtain (inner air curtain) that exchanges heat with the evaporator 8 is provided on the front surface of the case body 1 and protection. An air curtain (outer air curtain) blows out and keeps the showcases arranged on the product display shelf 7 cool while blocking the entry of outside heat into the warehouse. by the way,
In the above-mentioned freezing / refrigerating showcase, frost forms on the surface of the evaporator 8 with the cold insulation operation, and the amount of frost grows over time. Moreover, when frost forms on the surface of the evaporator 8, the frost serves as heat transfer resistance to reduce heat exchange between the evaporator and the air, and frost serves as air resistance to obstruct the flow of circulating cold air. , This reduces the cold insulation performance of the showcase.

Therefore, normally, the showcase is switched from the cold-keeping operation to the defrosting several times a day to melt and remove the frost adhering to the evaporator 8. As the defrosting method in this case, various defrosting methods using a heater, hot gas, and a heat pipe are known.

[0005]

The various defrosting methods described above have their advantages and disadvantages, and the following problems remain. That is, (1) In the heater defrosting method, circulating air heated by a defrosting heater installed on the upstream side of the evaporator is passed through the evaporator to defrost, but in this case, it passes through the evaporator. Since the air also flows into the inside of the cabinet as it is, the temperature inside the cabinet rises and the temperature of the displayed products rises, and if there is a large amount of frost, the ventilation resistance to the defrost air also increases, so the defrosting time increases. I have a problem.

(2) The hot gas defrosting method is a method of performing defrosting by directly supplying a high temperature refrigerant gas (hot gas) discharged from a compressor to an evaporator without bypassing a condenser and an expansion valve. Yes, compared to the above heater defrosting that defrosts the evaporator by heating the circulating air in the refrigerator, high defrosting efficiency,
Besides, it has the advantage that defrosting can be completed in a short time by suppressing the rise in temperature inside the refrigerator, but on the other hand, it is necessary to continuously operate the compressor of the refrigerator during the defrosting time, and the liquid condensed in the evaporator There is also a problem of liquid bag in which the refrigerant is sucked into the compressor as it is, so a countermeasure is required.

(3) Incorporating a heat pipe into the evaporator,
The method of defrosting by applying the heat applied to the evaporator of the heat pipe from the heater to the evaporator in the form of latent heat (the compressor of the refrigerator is stopped during defrosting) is the heater defrosting described above. The defrosting efficiency is higher than that of the method, and defrosting can be performed by suppressing the rise in the internal temperature, but a heater for heating that evaporates the working fluid of the heat pipe is required.

The present invention has been made in view of the above points. While utilizing the advantages of the hot gas defrosting method described above, the evaporator itself functions as a heat siphon during defrosting and the compressor of the refrigerator is stopped. It is an object of the present invention to provide a new defrosting method for a freezer-refrigerating showcase that can be defrosted even as it is.

[0009]

To achieve the above object, in the defrosting method of the present invention, a stop valve is connected to the refrigerant pipe on the inlet side of the evaporator, and the refrigerant pipe on the outlet side is frozen. The hot gas pipe branched from the high temperature side pipe between the compressor and the condenser of the compressor is connected through a switching valve, and at the time of defrosting, the stop valve on the evaporator inlet side is closed and the evaporator The switching valve is switched so that the outlet communicates with the hot gas pipe, and in this state, the high temperature refrigerant gas flowing into the evaporator through the hot gas pipe is heat-transported for defrosting.

In the above-mentioned defrosting method, hot gas is used as a means for preventing the refrigerant gas flowing from the hot gas piping and the refrigerant liquid condensing and flowing down in the refrigerant piping of the evaporator from intermingling and interfering with each other. A bypass pipe with a stop valve is provided between the middle of the gas pipe and the evaporator inlet, and at the time of defrosting, the high temperature refrigerant gas is introduced into the evaporator from the inlet side through the bypass pipe, and inside the evaporator. The liquid refrigerant that condenses and flows down can also be returned from the outlet of the evaporator to the high temperature side conduit.

The hot gas pipe switching valve includes:
It can be implemented using a three-way valve.

[0012]

In the above defrosting method, the inside of the evaporator is at low temperature and low pressure at the start of defrosting, whereas the discharge side of the compressor and the condenser are hot and the pressure is higher than inside the evaporator. Since there is a large amount of refrigerant gas, the high temperature refrigerant gas flows into the evaporator through the hot gas pipe, diffuses in the evaporator, dissipates heat and is condensed, and then the refrigerant liquid flows down in the evaporator. Evaporation / condensation is carried out from the outlet through a hot gas pipe to the high temperature part of the refrigerator (high temperature side line between the discharge side of the compressor and the condenser), where it is evaporated again and sent to the evaporator. Repeat the cycle. When the refrigerant gas dissipates heat and condenses in the evaporator, latent heat melts the frost adhering to the surface of the evaporator for defrosting.

In this case, a bypass pipe with a stop valve is provided so as to branch from the middle of the hot gas pipe to the inlet of the evaporator so that the high temperature refrigerant gas can pass through the bypass pipe during defrosting. Flows in from the inlet and diffuses into the evaporator. On the other hand, the refrigerant liquid condensed inside the evaporator does not intermingle with the refrigerant gas, flows down by gravity in the refrigerant pipe of the evaporator and exits from its outlet, and then returns to the discharge side of the compressor through the hot gas pipe. . As a result, the circulation amount of the refrigerant flowing in the evaporator during defrosting is significantly increased, and more defrosting heat can be efficiently applied to the evaporator to complete defrosting in a short time.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings of the embodiments, the same members corresponding to FIG. 3 are designated by the same reference numerals. Example 1 FIGS. 1A and 1B show an example corresponding to claim 1 of the present invention, in which FIG.
(B) shows the state of defrosting. That is, for the evaporator 8 having the coil 8a and the plate fins 8b arranged in a meandering shape and arranged with the refrigerant inlet on the upper side and the refrigerant outlet on the lower side, the refrigerant pipe 12 connected between the condenser 6 and Is connected to a solenoid valve (stop valve) 13 in series with the expansion valve 7, while a three-way valve 15 is provided in the middle of a suction-side refrigerant pipe 14 that connects the outlet of the evaporator 8 and the compressor 5. Compressor 5
A hot gas pipe 16 drawn out from a high temperature side pipe line between the discharge side and the condenser 6 is connected. The piping shown in the drawing is schematically shown. In practice, the hot gas piping 16 is arranged at a level lower than that of the evaporator 8 and at substantially the same height as the compressor 5, the condenser 6, and the three-way valve 15. There is.

With such a structure, during the cold-keeping operation of the showcase, the solenoid valve 13 connected to the inlet side of the evaporator 8 is "opened" and the three-way valve 15 is connected to the outlet side of the evaporator 8 as shown in FIG. The connected refrigerant pipe 14 is set at a port position where it communicates with the suction side of the compressor 1, and the compressor 5 is operated to perform a refrigeration cycle. On the other hand, when the cold insulation operation is switched to the defrosting at a predetermined time cycle by timer control or the like, the operation of the compressor 5 is stopped by a command from a control unit (not shown), and the solenoid valve 13 as shown in FIG. Is closed, and the three-way valve 15 is switched to a port position where the refrigerant pipe 14 and the hot gas pipe 16 communicate with each other.

As a result, defrosting is performed as described below. That is, in the state shown in FIG. 2B, the hot refrigerant gas from the compressor 5 and the condenser 6 is passed through the hot gas pipe 16, the three-way valve 15, and the refrigerant pipe 14 to the evaporator 8 in the low temperature and low pressure state. The refrigerant gas flowing in rises and diffuses in the coil 8 and radiates heat to the plate fins 8b to be condensed. Further, the condensed and liquefied refrigerant liquid flows down in the coil 8a, and from the outlet thereof, traces the path in the reverse direction and returns to the discharge side high temperature portion of the compressor 5, where it is evaporated again and flows into the evaporator 8. Then, the evaporation / condensation cycle is repeated so as to radiate heat, and in this process, the evaporator 8 is given defrosting heat in the form of latent heat for defrosting. That is, at the time of this defrosting, the evaporator 8 itself functions as a heat siphon.

In addition, unlike the conventional heater defrosting method in which this defrosting directly heats the circulating air in the refrigerator that ventilates the evaporator 8, the evaporator 8 is heated from the inside to defrost. As a result, it is possible to prevent the temperature of the inside air from rising and prevent the freshness of the displayed products from deteriorating. Further, it is not always necessary to continue operating the compressor 5 of the refrigerator during defrosting as in the conventional hot gas defrosting method, and even if the operation of the compressor is stopped during defrosting, The heat accumulated in the compressor 5 and the condenser 6 can be utilized to perform defrosting without trouble.

In a showcase facility in which a plurality of showcases are kept cold by one compressor,
While the compressor continues to operate, the one showcase can be defrosted as described above and the remaining showcases can be kept cold. In this case, the discharge side of the compressor is in a high temperature and high pressure state. Therefore, the defrosting ability for the showcase during defrosting is further enhanced.

Embodiment 2 FIG. 2 shows an application embodiment corresponding to claim 2 of the present invention, which is an improvement of the embodiment 1 described above. In this embodiment, in addition to the configuration described in the first embodiment, a bypass pipe 18 that branches from an intermediate point of the hot gas pipe 16 and has an electromagnetic valve 17 as a stop valve between the hot gas pipe 16 and the inlet of the evaporator 8 is provided. Are connected.

With such a structure, the solenoid valve 17 and the three-way valve 15 are set to the positions shown in FIG. 1 (a) in the same manner as in the first embodiment with the solenoid valve 17 kept "closed" during the cold-keeping operation of the showcase. The compressor 5 is operated. On the other hand, at the time of defrosting, the solenoid valve 13 on the evaporator inlet side is switched to “closed”, the solenoid valve 17 of the bypass pipe 18 is switched to “open”, and the three-way valve 15 is replaced with the refrigerant pipe 14 on the evaporator outlet side by the hot gas pipe 16 Switch to a port position that leads to. This allows hot gas piping 1
6, the high temperature refrigerant gas is passed through the bypass pipe 18 to the evaporator 8
The liquid refrigerant introduced from the inlet side to the inside of the evaporator 8 and condensed and flowed down from the outlet of the evaporator is a refrigerant pipe 14, a three-way valve 15,
Example 1 is carried out by refluxing to the high temperature side of the refrigerator via the hot gas pipe 16 and the evaporation / condensation cycle of this refrigerant.
Similarly to the above, the evaporator 8 functions as a heat siphon, and the heat from the compressor 5 and the condenser 6 is applied to the evaporator 8 as defrost heat for defrosting. Moreover, in this embodiment, the bypass pipe 18 serves as a supply line for the high-temperature refrigerant gas to the evaporator 8, and the refrigerant liquid condensed and liquefied in the evaporator flows down the coil 8a of the evaporator 8 and exits from its outlet. Bring to reflux.
Therefore, unlike in the first embodiment, the refrigerant gas that rises and diffuses in the pipe of the coil 8a inside the evaporator 8 and the refrigerant liquid that condenses and liquefies and flows down do not interfere with each other to prevent the flow. As a result, the circulation amount of the refrigerant flowing through the evaporator 8 is significantly increased, and more heat for defrosting can be applied to the evaporator 8 to effectively perform defrosting.

[0021]

As described above, the present invention has the following effects. 1) At the time of defrosting, the evaporator itself can function as a heat siphon, and the heat of the refrigerator and the condenser can be applied to the evaporator for efficient defrosting. 2) Moreover, unlike the conventional hot gas defrosting method, it is not always necessary to operate the compressor during defrosting, and even if the compressor is stopped at the time of shifting from the cold insulation operation to the defrosting, the compressor and the condensation are condensed. Defrost can be performed without trouble using the heat stored in the vessel.

3) Further, unlike the conventional heater defrosting method, the circulating air in the refrigerator is not directly heated, so that the temperature rise in the refrigerator during defrosting can be suppressed and deterioration of the freshness of the displayed products can be prevented. It has an excellent effect as a defrosting method for refrigerated showcases. 4) Furthermore, if the heat siphon defrosting method of the present invention is adopted for showcase equipment in which a plurality of showcases are kept cool by one compressor, the It is possible to perform defrosting with one showcase while keeping the remaining number of showcases cool. In this case, the discharge side of the compressor is maintained at high temperature and high pressure. The defrosting ability against is further enhanced.

[Brief description of drawings]

FIG. 1 is a piping diagram of a refrigerant circuit corresponding to a first embodiment of the present invention, in which (a) is a diagram showing a state of a cold insulation operation and (b) is a diagram showing a state during defrosting.

FIG. 2 is a piping diagram of a refrigerant circuit showing a defrosting state corresponding to Example 2 of the present invention.

FIG. 3 is a configuration diagram of a cold air circulation type freezing / refrigerating showcase to which the present invention is applied.

[Explanation of symbols]

 5 Compressor 6 Condenser 7 Expansion valve 8 Evaporator 12 Inlet side refrigerant pipe 13,17 Solenoid valve (stop valve) 14 Outlet side refrigerant pipe 15 Three-way valve 16 Hot gas pipe 18 Bypass pipe

Claims (3)

[Claims] 1. A refrigerator evaporator in a cold air circulation duct in a refrigerator,
In a freezer-refrigerator showcase that has a blower fan and circulates the cool air that has exchanged heat with the evaporator during cold storage operation to cool the products displayed in the refrigerator, a stop valve is installed on the refrigerant pipe on the inlet side of the evaporator. In addition to the connection, the refrigerant pipe on the outlet side is connected via the switching valve to the hot gas pipe that is branched and drawn from the high temperature side pipe between the compressor and the condenser of the refrigerator, and the evaporator is used during defrosting. While closing the stop valve on the inlet side, switch the switching valve so that the outlet of the evaporator communicates with the hot gas pipe, and in this state heat transfer with the high temperature refrigerant gas flowing into the evaporator through the hot gas pipe for defrosting. A defrosting method for a refrigerating showcase, which is characterized by performing 2. The defrosting method according to claim 1, wherein a bypass pipe with a stop valve is provided branching from the middle of the hot gas pipe to the inlet of the evaporator, and the high temperature refrigerant is passed through the bypass pipe during defrosting. Defrosting of a freezer-refrigerating showcase, characterized in that gas is introduced into the evaporator from its inlet side, and liquid refrigerant that condenses and flows down inside the evaporator is returned from the outlet of the evaporator to the hot side pipeline. method. 3. A defrosting method for a refrigerating and refrigerating showcase according to claim 1, wherein the switching valve of the hot gas pipe is a three-way valve.