JP3362596B2 - Cooler defroster - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defroster for a chiller for a fin tube type evaporator of a refrigerator mounted on a freezing or refrigerated open showcase or the like. About. 2. Description of the Related Art First, the configuration of a cool air circulation type open showcase to which the present invention is applied is shown in FIG. In the figure, 1 is a front open case body, 2 and 3 are an inner ventilation duct and an outer ventilation duct defined between an outer box and an inner box of the case body 1 surrounding a product display room 4 in the refrigerator. The inner duct 2 has a fin-tube evaporator (cooler) 5 connected to a condensing unit 7 of a refrigerator via an expansion valve 6, and an inner blower fan 8.
However, the outer ventilation duct 3 is provided with an outer ventilation fan 9. Reference numeral 10 denotes a product display shelf arranged in the product display room 4. [0003] With such a configuration, during the cold-holding operation of the showcase (the condensing unit 7 and the blowing fans 8, 9 are operated), the cool air that has exchanged heat with the evaporator 5 circulates through the ventilation duct and the case body. A cold air curtain is blown out on the front face of 1 to keep the products arranged on the product display shelf 10 cool while shielding the outside air heat from entering the inside of the refrigerator. By the way, in the above showcase, the evaporator 5
Frost adheres to the surface of the surface, and the amount of frost increases with time. In addition, when frost forms on the surface of the evaporator 5, the frost acts as a heat transfer resistance, lowering the heat exchange performance between the evaporator and the circulating air. Lower. Therefore, usually, the showcase is switched from the cooling operation to the defrosting several times a day so that the frost adhering to the evaporator 5 is melted and removed. [0004] As a defrosting method in this case, the following method has been conventionally known. 1) An electric heater for defrosting is arranged on the upstream side of the evaporator 5, and circulating air heated and heated by the heater is sent to the evaporator for defrosting. 2) The above-described electric heater for defrosting is disposed inside the evaporator and is thermally coupled to the fins, and the fins of the evaporator are directly heated by energizing the heater to perform defrosting. [0005] 3) As proposed in JP-A-5-346284, a heat pipe is incorporated in an evaporator.
The defrosting heat is applied to the evaporator via the heat pipe from an electric heater which is thermally coupled to the evaporator of the heat pipe drawn from the evaporator. [0006] The above-mentioned various conventional defrosting methods have their respective advantages and disadvantages, and the following problems remain. That is, in the method 1),
Since the airflow that has passed through the evaporator during defrosting also circulates and flows to the inside of the refrigerator as well, the temperature of the displayed products arranged in the refrigerator increases and the freshness of the products is deteriorated. In addition, when the amount of frost formed on the evaporator is large, the ventilation resistance against the defrosted air increases, so that the defrosting time is prolonged. In the method 2), since the fins are laid directly inside the evaporator and directly heated by the electric heater, the defrosting efficiency is high and the defrosting can be completed in a short time. In addition, it is structurally difficult to bring an electric heater into close contact with the fins and heat-transfer them. For example, as shown in FIG. 4, an electric heater 12 is inserted into a heat transfer pipe 11 which is expanded so as to be in close contact with the fins 5a of the evaporator 5 and is piped into the evaporator.
When the electric heater 12 is energized to melt the frost 13 adhering to the surface of the fin 5a, the heat transfer efficiency is low unless the heat transfer pipe 11 and the electric heater 12 are in close contact with each other. As a result, the heater becomes abnormally
The fins 5a and the surrounding air are heated by the heat capacity of the heater 12 for a while after the completion of the defrosting, and a long pull-down time is required until the inside temperature decreases to a predetermined cooling temperature after the cooling operation restarts. [0008] Further, the defrosting method using a heat pipe of 3) has a higher defrosting efficiency than the methods of 1) and 2), and there is no problem of overheating of the electric heater. -To secure piping space for heat pipes around the evaporator, especially below the evaporator, like an evaporator placed at the bottom of the showcase, so that it can be drawn out of the tube evaporator for piping. It is difficult to apply when it is difficult. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to solve the above-mentioned problems of the various defrosting methods, and particularly to a compact and defrosting efficiency suitable for a cooler mounted on a showcase. An object of the present invention is to provide a high novel defrosting device. According to the present invention, there is provided a heat pipe having a structure in which an electric heater is built in a sealed pipe in which a low-boiling-point working fluid is sealed. Heat transfer coupling and piping almost horizontally inside the cooler,
And so that the electric heater is immersed in the working fluid, laid on the bottom side in the pipe along the longitudinal direction of the heat pipe, heating the working fluid by energizing the electric heater when defrosting the cooler, The defrosting heat is applied to the fins by the cycle of evaporating and condensing the hydraulic fluid to melt and remove the frost formed on the cooler surface. [0011] As described above, the electric heater is built in the heat pipe which is arranged in a substantially horizontal direction inside the cooler, and the electric heater is immersed in the working fluid. By laying it on the bottom side, the working fluid enclosed in the heat pipe is directly heated by the electric heater laid in the pipe and boiled, and the fins of the cooler are made uniform from the heat pipe by the latent heat when the vapor condenses And the defrosting can be efficiently performed by heating to a high degree, and high heat conductivity can be secured between the electric heater and the working fluid, thereby improving the heating efficiency. In addition, since the defrosting heat provided by the electric heater is transferred by a cycle of evaporating / condensing the working fluid, a large amount of heat is transferred with a small temperature difference between the evaporating part and the condensing part. As a result, there is no rise in the internal temperature due to overheating of the electric heater. In addition, since it is not necessary to draw a heat pipe from the cooler to the outside, a compact configuration is provided. Embodiments of the present invention will be described below with reference to the drawings. In each embodiment, the same members corresponding to FIG. 4 are denoted by the same reference numerals. Embodiment 1 In FIGS. 1 and 2, a fin-tube type evaporator 5 including a fin 5a and a refrigerant pipe 5b is mounted on, for example, the open showcase shown in FIG. A heat pipe 14 with a built-in heater according to the present invention, which is thermally coupled to the fins 5 a, is laid substantially inward over the entire width of the evaporator 5. The heat pipe 14 is sealed off at both ends and encloses the working fluid 14b while leaving a condensing space in a highly heat-conductive sealed tube 14a such as copper.
Further, an electric heater 12 is provided on the bottom side along the longitudinal direction of the sealed tube 14a so as to be immersed in the working fluid 14b. In order to incorporate the heat pipe 14 into the evaporator 5, a copper pipe is first inserted into a hole drilled in the fin 5a, and the pipe is expanded in this state, and its peripheral surface is brought into close contact with the fin. , An electric heater 12, and the inside of the pipe is evacuated to an appropriate amount of the working fluid 14.
b, and then the pipe is sealed off. The working liquid 14b is a liquid having a low boiling point whose freezing point is lower than the refrigerant evaporation temperature during the cold-holding operation, and is, for example, a halogenated hydrocarbon-based refrigerant (HFC-134).
a, a chlorofluorocarbon refrigerant such as HCF-22), fluorocarbon,
Alcohol can be adopted. In addition, 15 is a power supply of the electric heater 12. In such a configuration, in order to switch the showcase equipped with the evaporator 5 from the cold-holding operation to the defrosting operation, the operation of the refrigerator is stopped and the electric heater 12 is energized at the same time. As a result, the working fluid 14b sealed in the heat pipe 14 is heated and boiled, and its vapor is dispersed as a vapor stream as shown by an arrow P in FIG. After the heat is radiated from the wall surface to the fins 5a and condensed into a liquid, the evaporation / condensation cycle is repeated so that the liquid flows back to the bottom in the heat pipe. Then, when the vapor of the working fluid condenses, the latent heat is radiated to melt and remove the frost 13 attached to the surface of the fin 5a. In addition, the vapor of the working fluid diffused in the pipe concentrates on the low-temperature part, so that the entire evaporator is uniformly heated,
Defrosting can be performed without causing partial melting of frost. As can be seen from the above description, the electric heater 1
2 is incorporated in the above-mentioned Japanese Patent Application Laid-Open No. 5-3 / 1993.
As in the configuration disclosed in Japanese Patent No. 46284, there is no need to draw out the evaporator of the heat pipe to the outside of the fin-tube evaporator and connect it to the electric heater. It can be configured compact by incorporating it. As described above, according to the structure of the present invention, the following effects can be obtained as compared with the conventional various defrosting methods. 1) The entire chiller can be uniformly heated to efficiently melt and remove frost formed on the fins. 2) For the heat transfer between the electric heater and the frost adhering to the cooler surface, the latent heat generated by the evaporation and condensation of the working fluid is utilized, so that the heat resistance of the heat transfer path is very small, and There is no abnormal overheating of the heater. This allows
In the cooler of the showcase, the pull-down time at the time of restarting the cold-holding operation after the defrost can be reduced while suppressing the rise in the internal temperature during the defrost. 3) The evaporator of the heat pipe is drawn out of the cooler as in the conventional heat pipe defrosting system by using a configuration in which an electric heater serving as a defrost heat source is built in the heat pipe and incorporated in the cooler. Therefore, even when it is difficult to secure extra space below the cooler, such as a cooler arranged in the ventilation duct on the bottom side of the inside of the cabinet of the showcase, there is no need to connect the electric heater to the electric heater. , And can be implemented without being limited by space.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram in which a defrosting device corresponding to a first embodiment of the present invention is incorporated in a cooler. FIG. 2 is an explanatory diagram of a defrosting operation by the configuration of FIG. FIG. 3 is a schematic configuration diagram of an open showcase to which the present invention is applied. FIG. 4 is a configuration diagram of a conventional defrosting apparatus using a heater defrosting system. [Description of References] 5 Fin-tube type evaporator 5a Fin 5b Refrigerant pipe 12 Electric heater 13 Frost 14 Heat pipe 14a Sealed pipe 14b Hydraulic fluid

Claims (1)

(57) [Claim 1] A defroster for a cooler intended for a fin-tube type evaporator of a refrigerator mounted on an open showcase or the like, wherein a low-boiling-point hydraulic fluid is supplied. A heat pipe with a built-in electric heater in the sealed tube is heat-coupled to the fins and is piped in a substantially horizontal direction inside the cooler, and the electric heater is immersed in the working fluid, It is laid on the bottom side inside the pipe along the longitudinal direction of the heat pipe. When the cooler is defrosted, the electric heater is energized to heat the working fluid, and the fin is defrosted by the cycle of evaporation and condensation of the working fluid. A defroster for a cooler, which melts and removes frost formed on the surface of the cooler by applying heat.