JPH07159018A - Defrosting system for freezing cold storage display case - Google Patents

Abstract

PURPOSE:To provide a novel defrosting system for a freezing cold storage display case in which defrosting can be efficiently conducted in a short time. CONSTITUTION:A freezing cold storage display case has a fine tube type evaporator 6 of a freezer and a fan 7 disposed in a cold gas circulating duct 2 surrounding an indoor commodity display chamber 4 of a case body 1 to cold insulate commodities displayed in the case by circulating and supplying cold gas heat exchanged with the evaporator at the time of cold insulation and operation, and comprises a heat pipe 10 laid at the plate fin of the evaporator as defrosting means, and an electric heater 11 provided as a defrosting power source at an evaporating part of the heat pipe. Defrosting heat is applied from the heater to the evaporator through the heat pipe at the time of defrosting to defrost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting method for a freezing / refrigerating showcase intended for an open showcase or the like.

[0002]

2. Description of the Related Art A fin-tube type evaporator of a refrigerator and a blower fan as a cooler are housed in a cool air circulation duct defined so as to surround a product display room of a case body, and heat is exchanged with the evaporator during a cool operation. In a freezing / refrigerating showcase that circulates the cooled air to cool the products displayed in the refrigerator, frost forms on the fin surface of the evaporator along with the cold insulation operation, and the amount of frost grows with the lapse of the cold insulation operation. To do.

By the way, when frost forms on the fin surface of the evaporator, the frost acts as a heat resistance to lower the heat transfer property, and the frost blocks the flow of air to blow air in the cool air circulation duct and the evaporator. In addition to not being able to exchange heat, the amount of cold air that circulates inside the showcase compartment becomes insufficient. Especially in the open showcase, the characteristics of the cold air curtain that blows off on the open surface of the case body deteriorates and It causes a decrease in cold insulation performance.

Therefore, in the refrigerating and refrigerating showcase, the refrigerating operation is switched from defrosting operation to defrosting several times a day to melt and remove the frost formed on the evaporator. As defrosting methods in this case, various defrosting methods such as off-cycle defrosting, heater defrosting, and hot gas defrosting have been conventionally known. Generally, defrosting is started by timer control, and the temperature sensor placed in the evaporator or the ventilation duct on the outlet side of the evaporator finishes defrosting (when the frost adhering to the surface of the evaporator is melted, the plate of the evaporator is melted). The temperature of the fins themselves or the temperature of the airflow that has passed through the evaporator rises), and the operation mode of the showcase is switched from defrosting to resumption of cold insulation operation.

[0005]

By the way, in the case of foods such as meat and fresh fish handled in a freezer-refrigerated showcase, if the temperature inside the showcase rises, the product temperature rises and the quality of the food deteriorates rapidly. When performing the defrosting by stopping the operation of No. 3, it is an important condition in operation management to finish the defrosting in a short time in order to suppress the rise in the internal temperature during the defrosting as low as possible.

From the above viewpoint, when examining the above-mentioned various conventional defrosting methods, first, in the off-cycle defrosting method, defrosting takes a long time because defrosting is performed by using the heat of the outside air as a defrosting heat source. During that time, the temperature inside the warehouse and the temperature of the displayed products rise, making it difficult to maintain freshness. In addition, in the heater defrosting method, an electric heater is installed on the inlet side of the evaporator, and during defrosting, the fan inside the refrigerator is operated to continue blowing air and send heated air that has exchanged heat with the electric heater to the evaporator. There are a method of defrosting and a method of directly wiring an electric heater to the plate fins of the evaporator. In the former method, however, the defrosting time is long because the frost that has frosted on the plate fins of the evaporator serves as ventilation resistance and prevents ventilation of the air heated by the heater. In particular, since the amount of frost on the fin plate is not uniform, the heating and ventilation flow concentrates on the portion with a small amount of frost, that is, the portion with a low ventilation resistance. Is almost clogged with frost)
The progress of defrosting is greatly delayed. Also, in the latter method, the heater is heated in the same manner in the part with a large amount of frost and the part with a small amount of frost. Defrosting the part with a small amount of frost is completed first, and this part is heated more than necessary. In other words, defrosting does not proceed uniformly throughout the evaporator, which causes the defrosting time to increase and the temperature inside the refrigerator to rise.At the same time, the pull-down characteristic (internal temperature The time during which the temperature is lowered to a predetermined cooling temperature is deteriorated. In addition, wasteful energy consumption is large and defrosting efficiency is low.

On the other hand, the hot gas defrosting method is a method in which the high temperature refrigerant gas discharged from the compressor of the refrigerator is directly sent to the refrigerant tube of the evaporator for defrosting.
While there is an advantage that defrosting can be done in a short time compared to off-cycle and heater defrosting methods, switching control of the refrigerant circuit is required, and processing of the refrigerant liquid condensed by the evaporator must also be considered. The refrigerant circuit of the refrigerator becomes complicated.
In addition, there is a problem in that the power consumption increases because the compressor of the refrigerator is continuously operated even during defrosting.

The present invention has been made in view of the above points, and an object thereof is to provide a novel defrosting method for a freezer-refrigerating showcase which solves the above problems and enables defrosting to be performed efficiently in a short time. To do.

[0009]

In order to achieve the above object, the defrosting method of the present invention is such that a heat pipe is installed in the evaporator as a defrosting means and the evaporator is removed from the outside through the heat pipe during defrosting. Defrosting shall be performed by applying frost heat. Further, the specific configuration of the heat pipe for defrosting in the above is to disperse a plurality of heat pipes with respect to the plate fins of the evaporator, and to use an electric heater as a defrosting heat source in the evaporation part of the heat pipe drawn out from the evaporator. Can be attached and implemented. The working fluid sealed in the heat pipe is a working fluid having a low boiling point whose freezing point is lower than the cold-keeping operation temperature of the evaporator.

[0010]

In the above defrosting method, when the operation mode of the refrigerating and refrigerating showcase is switched from the cold insulation operation to the defrosting and the electric heater (defrosting heat source) attached to the evaporation part of the heat pipe is energized, it is enclosed in the heat pipe. The working fluid evaporates by heating with the heater, and the working fluid vapor diffuses and moves into the heat pipe condensing part (portion connected to the plate fin of the evaporator) and dissipates heat to the plate fin of the evaporator. After condensing, the evaporation / condensation cycle is repeated so as to flow back to the evaporation section and evaporate.
Then, the defrosting heat input to the electric heater is applied to the evaporator in the form of latent heat of condensation to heat it, and the frost adhering to the fin plate is melted and defrosted.

Moreover, as is well known, when the heat pipe has a high temperature portion and a low temperature portion on the heat radiating side, the heat input from the evaporation portion operates so as to transfer to the low temperature portion. Therefore, even if the plate fin of the evaporator has a portion with a large amount of frost and a portion with a small amount of frost, a large amount of defrost heat is concentrated on the portion with a large amount of frost, so defrosting is performed on the entire evaporator. While proceeding uniformly, wasteful energy consumption can be suppressed and defrosting can be performed efficiently in a short time.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention for a two-layer air curtain type multi-stage open showcase. In the figure, 1 is a front open case body, and 2, 3
Are inner ventilation ducts and outer ventilation ducts that surround the product display room 4 and are defined between the outer and inner boxes of the case body 1. The inner duct 2 has fins connected to the condensing unit 5 of the refrigerator. A tube-shaped evaporator 6 and a blower fan 7 are provided, and a blower fan 8 is provided in the outer duct 3. In addition, 9 is a product display shelf provided in the product display room 4.

With such a configuration, during the cold-keeping operation (the condensing unit 5 of the refrigerator and the blower fans 7 and 8 are operated), the cool air that exchanges heat with the evaporator 6 on the front surface of the case main body 1 to ventilate the inner duct 2. It is well known that air curtains (inner air curtains) and protective air curtains (outer air curtains) are blown out to block the entry of heat from the outside air while keeping the displayed products in the refrigerator cool.

On the other hand, as a defrosting means for the fin-tube type evaporator 6 described above, a heat pipe 10 is provided in the evaporator 6 according to the present invention, and a defrosting heat source is provided in the evaporation portion of the heat pipe 10 as an electric heater 11. Is attached. Next, the detailed structure is shown in FIG.
It shows in (b). That is, the fin-tube type evaporator 6 includes a large number of plate fins 6a and a refrigerant tube 6b.
Is connected to the condensing unit 5 (composed of a compressor, a condenser, etc.) of the refrigerator via an expansion valve (not shown). . The evaporator 6 is sewn between the refrigerant tubes 6b, and the plate fins 6a have a plurality of heat pipes 11a.
Are distributed and piped. Further, an evaporating portion 10b containing the working fluid 10a is connected to the other end of each heat pipe 10 drawn out from the evaporator 10, and an electric heater 11 serving as a defrost heat source is provided around the evaporating portion 10b of the heat pipe 10. Is attached. In addition, heat pipe 1
The working fluid 10a sealed in 0 is a working fluid having a low boiling point whose freezing point is lower than the refrigerating operation temperature, such as a halogenated hydrocarbon refrigerant (HFC-134a, HCFC-), so as not to freeze during the refrigerating operation of the showcase. CFC-based alternative refrigerant such as 22), fluorocarbon, alcohol, etc. are used. Reference numeral 12 shown in the drawing denotes an energization control unit of the heater 11, which energizes the heater 11 together with a defrost start command by timer control or the like, and energizes the heater based on a signal from a temperature sensor that detects the end of defrost. Stop.

With this configuration, when a defrosting start command is given,
The operation of the condensing unit 5 of the refrigerator is stopped, or the solenoid valve of the refrigerant pipe leading to the evaporator 6 is closed to stop the refrigerant supply to the evaporator to interrupt the cold insulation operation, and the control unit 12 The electric heater 11 is energized to heat the evaporation portion 10b of the heat pipe 10. Thereby, the hydraulic fluid 10 of the heat pipe 11
As a vaporizes, the vapor diffuses in the pipe and moves to the condenser section piped to the evaporator 6, where it radiates heat to the plate fins 6a of the evaporator to be condensed and then returns to the evaporator section 10b by gravity. The evaporation / condensation cycle is repeated so as to evaporate again. As a result, the defrosting heat input from the heater 11 is radiated to the evaporator 6 via the heat pipe 10, and the frost formed on the plate fins 10a is melted and defrosted.

In this case, the heat released from the heat pipe 10 to the evaporator 6 is efficiently transferred in the form of latent heat of condensation of the working liquid vapor, and the working liquid vapor diffused in the heat pipe has a low temperature portion, that is, frost formation. Since the condensation heat is concentrated on a large amount of the condensation heat, the entire evaporator 6 is uniformly heated and defrosting proceeds uniformly. As a result, the defrosting is completed within a short time in which the temperature inside the showcase, and thus the temperature of the displayed products, does not rise so much. In addition, the temperature of the refrigerant tube 6b of the evaporator 6 is -1 during the cold keeping operation.
The heat pipe 11 connected to the plate fins 10a is also cooled to about -5 to + 5 ° C at around 0 ° C, but if the working liquid having a low boiling point as described above is used as the working liquid 10a of the heat pipe 10, There is no risk of the working fluid solidifying or freezing during the cold-keeping operation, whereby the heat transfer capacity of the heat pipe 10 can be fully exerted at the start of defrosting.

When the defrosting end temperature sensor detects the defrosting end temperature, the energization of the heater 11 is stopped based on this signal, and the cooling operation by the refrigerator is restarted. During defrosting, the blower fan 7 arranged in the inner duct 2 in FIG. 1 is stopped, and the blower fan 8 arranged in the outer duct 3 is continuously operated to blow out a protective air curtain on the front surface of the case body 1. It is good to prevent outside heat from entering the refrigerator.

[0018]

As described above, according to the present invention, the heat pipe is adopted as the defrosting means, and the defrosting heat is applied to the evaporator through the heat pipe.
Compared with the conventional defrosting method, defrosting can be completed in a short time and efficiently without wasting energy, which is extremely effective in maintaining the freshness of products such as meat and fresh fish displayed in showcases. Defrosting method can be provided.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a freezing-refrigerating open showcase adopting the defrosting method of the present invention.

FIG. 2 is a diagram showing an assembly structure of an evaporator and a defrosting heat pipe in FIG. 1, (a) is a side view,
(B) is a front view

[Explanation of symbols]

 1 Case Main Body 4 Product Display Room 5 Refrigerator Condensing Unit 6 Evaporator 6a Plate Fin 6b Refrigerant Tube 7 Blower Fan 10 Heat Pipe 10a Working Liquid 10b Evaporator 11 Electric Heater

Claims (3)

[Claims] 1. A fin-tube type evaporator of a refrigerator and a blower fan are provided in a cool air circulation duct surrounding an in-compartment product display room of a case body, and cool air that has exchanged heat with the evaporator is circulated and blown to the inside of the cooler during a cold insulation operation. In a freezer-refrigerating showcase that keeps the displayed products cool, a heat pipe is piped to the evaporator as a defrosting means, and at the time of defrosting, defrosting heat is given to the evaporator from the outside through the heat pipe to perform defrosting. The defrosting method of the freezer refrigeration showcase. 2. The defrosting method according to claim 1, wherein a plurality of heat pipes are distributed and distributed to the plate fins of the evaporator, and an electric heater is used as a defrosting heat source in the evaporation portion of the heat pipe drawn out from the evaporator. A defrosting method for a refrigerated showcase characterized by being attached. 3. The refrigerating method according to claim 1, wherein the working liquid enclosed in the heat pipe is a working liquid having a low boiling point whose freezing point is lower than the cold-keeping operation temperature of the evaporator. Defrosting method for refrigerated showcases.