FI68314B - FOERFARANDE OCH ANLAEGGNING FOER SMAELTNING AV FROST FRAON EVAPORATOR VID KOMPRESSORKYLANLAEGGNING - Google Patents

Description

6831 4

Method and apparatus for defrosting frost from an evaporator of a compressor-refrigeration engine - Förfarande och aniäggning för smältning av frost fr & n evaporator vid kompressorky1anläggning

The invention relates to a method for defrosting frost from an evaporator of a compressor refrigeration machinery, as further defined in the preamble of claim 1. In addition, the invention relates to an apparatus for exploiting the method. In particular, the method and apparatus are intended for use in so-called in connection with hot gas melting, in which case the accumulated frost and ice are periodically melted from the evaporator of the refrigeration machinery.

In order to defrost the frost from the freezer in the freezer room, one of the following is most often used according to known procedures: 1) defrosting with electricity and 2) defrosting with hot cooling steamers.

In known electric melting devices, the melting device is an electrical resistor separate from the cooling mechanism, the melting rods of which are placed between the tubes of the evaporator. The resistor generates a certain amount of heat to melt the ice that has accumulated on the evaporator. The disadvantage of such a defrosting device is that the defrosting of the frost takes a long time and requires a lot of electrical energy, because the rods have to be placed between the evaporator tubes. In this case, in addition, the space to be cooled is heated during defrosting, because part of the thermal energy generated by the electric resistors is transferred to said space.

This invention belongs more closely to the so-called hot gas smelting processes. Of these, the most commonly used is the so-called. an inverted system in which the refrigerant cycle during defrosting is arranged to reverse, relative to the cooling circuit. In this case, the evaporator acts as a condenser during defrosting and, correspondingly, the condenser acts as a vaporizer during defrosting 6831 4 2. Such a system using hot gas for defrosting is in itself fast and efficient. However, the inverted system has structural changes in the evaporator and condenser feeders required by the smelting method, with the result that standard evaporators and condensers are not suitable for use. In addition, the special valves required are expensive and susceptible to failure.

In known hot gas smelting methods, in which the heat of superheating of the hot gas and the heat of evaporation are used for smelting, the partially impeded circulating material leaving the evaporator must be evaporated before it is fed to the compressor. This extraction can be done in many ways, such as by a heat exchanger, electricity or by using a second cooling evaporator surface or by using a special heat of 1 ampere heat, in which the liquid in storage is heated during the cooling cycle. The disadvantage of these evaporation methods is the high cost of the components required for smelting and their space requirements.

In addition, a hot gas smelting method is known in which the smelting is carried out only by utilizing the superheat heat of the hot gas without condensing the steam itself. The disadvantage of said method is the high cost of the flow control valve required to prevent condensation.

The object of the present invention is to provide a method and an apparatus for melting frost from an evaporator of a compressor refrigeration machinery, in which the disadvantages of various known methods are eliminated. According to the invention, the coolant is superheated throughout the defrosting, in which case only the superheated heat of the gas is used for defrosting.

The method and apparatus according to the invention are characterized by what is not shown in the characterizing parts of the appended claims.

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By implementing the method and apparatus according to the invention according to the claims, an efficient and fast melting operation is achieved at a low structural cost without complicated and expensive control devices.

The invention is illustrated by means of an application example in the following description with reference to the accompanying drawing, in which Figure 1 schematically shows a compressor refrigeration apparatus applying the defrosting method and apparatus according to the invention and Figure 2 shows the defrost circuit in a refrigerant drawing p-h.

The diagram of one of four major parts shown in kompressorikylmäko-maintenance material, namely: a compressor 1, a condenser 2, a pressure reducing device 3, and placed in a cold room evaporator 4, wherein the refrigerant cooling cycle takes place in the direction of arrow J of.

The periodic defrosting of the frost from the evaporator of the refrigeration machinery is carried out by means of a defrosting cycle (arrow S) connected to the refrigeration circuit J. The defrosting cycle is implemented in such a way that the strongly superheated steam compressed by the compressor 1 (coolant state change 9-10 in Fig. 2) is passed through the bypass pipe 8 past the condenser 2 and the pressure reducing device 3 directly to the evaporator 4. The cooling line is at the start of defrosting. When flowing in the evaporator piping, the superheated steam releases its heat of heat, which melts the ice accumulated on the pipes and lamellae efficiently and quickly, as all the heat is transferred from inside the pipe to the frost or ice layer on the outer surface of the pipe. Thus, the heat load entering the cold room remains low 4,631 4 because the heat of melting can be used almost completely to melt frost and ice. In this case, the refrigerated products do not have time to heat up harmfully.

The change in state of the coolant in the evaporator is illustrated in Figure 2 by line 10-11, where it is observed that the final state of the coolant after the evaporator is in the superheated area close to the saturated steam boundary curve 15.

The main suction line between the evaporator 4 and the compressor 1 is provided with a bypass line 5 connected to the suction side of the compressor 1. The main line is closed by a valve 6 during defrosting, whereby the supercharger 4 which conducts its superheat is passed along the bypass line 5 to the compressor 1. The main part of the bypass line is formed by The change of state of the coolant in the bypass line 5 and the capillary tube 7 is shown in Fig. 2 by line 11-12. As can be seen from Figure 2, the coolant is in position 12, i.e. on the suction side of the compressor 1, in a clearly superheated area, thus avoiding the entry of liquid refrigerant to the suction valve of the compressor. In this embodiment, the control member 7 formed in the bypass line 5 is a capillary tube, but it can also be any other control member implementing a change of state of the coolant, which is dimensioned to fit with other equipment according to the operating conditions.

The heat required for smelting is obtained mainly from the pressing work of the hermetic compressor. At the beginning of the defrost cycle, the steam heats up in the compressor suction duct from the waste heat of the motor windings (state change 12-9 in Fig. 2) and the compression work of the compressor cylinder greatly increases the superheat of the steam. According to the operating principle of the system, there is no risk of liquid droplets entering the compressor suction valve. The device arrangement has thus eliminated the so-called Compressor fluid shock hazard. The advantage, in addition to the simple structure, is that it does not

Claims (2)

5 6831 4 no additional, external heat source is required to generate the melting heat, nor is it necessary to store heat during the cooling cycle. The defrost system can be easily connected to the automatic defrost cycle end as required. When the ice formed on the surface of the evaporator has melted, the hot gas no longer cools and the pressure and temperature of the coolant flow leaving the evaporator increase. This situation is schematically represented by the state change curve shown in broken lines in Figure 2. The impulse required to end the defrost cycle can be taken either from the compressor suction side or from the compressor pressure side to the pressure switch 16, i.e. at points 13 and 14 in Figure 2. Respectively, the required impulse for the temperature switch terminates the defrost cycle. The control methods are therefore alternative. Embodiments of the invention may vary within the scope of the appended claims. A method for defrosting frost from an evaporator of a compressor refrigeration apparatus, wherein the refrigeration apparatus comprises a compressor (1), a condenser (2), a pressure reducing device (3) and an evaporator (4) and wherein a so-called hot gas smelting, in which the coolant is led to the evaporator (4) and the defrosting is stopped when the ice formed on the surface of the evaporator has melted, whereby the defrosting can be carried out, for example, by increasing the temperature and / or pressure of the refrigerant on the basis of an impulse, the method being known from the following steps. 6 6831 4 - removing the coolant that has transferred its superheating heat to the evaporator (4) from the evaporator (4) in the superheated state near the saturated steam boundary curve (state change 10-11, Fig. 2), so that the coolant does not condense in the State change 11-12-, Figure 2). Apparatus for using the method according to claim 1, the apparatus comprising a bypass pipe (8) through which the superheated coolant is passed past the condenser (2) and the pressure relief device (3) directly to the evaporator (4), characterized by a bypass line (5) through which the cooling steam is steamed (4) to the compressor (1), the main suction line being closed, e.g. by a valve (6) and a possible control device (16), which terminates the defrosting cycle immediately after the ice formed on the surface of the evaporator (4) has dried. characterized in that the bypass line (5) is provided with a melting capillary (7) or a similar pressure relief device. A method for cleaning the frost fr & n evaporator from a compressor cooling unit, a color cooling unit with a compressor (1), a color measure (2), a reducing arrangement (3) and an evaporator (4) and colors for the heating suction. varmgaesmältning, där kylmedlet leds kraftigt överhettat direkt fr4n kompressorn (tilletändsäniring 12-10, fig. 2) account for the evaporator (4) and the color of the evaporator, d4 iset som