Vapor compression-type refrigerator and method for controlling same

Abstract

The present invention is provided with an extraction device (40) including: a cooling unit for cooling gas that has been extracted from a condenser (5) and condensing condensed gas; and an exhaust pump (48) for discharging, to the exterior, uncondensed gas that has been isolated without having been condensed by the cooling unit. A current temperature difference, which is the difference between the current saturation temperature in the condenser (5) and the current outlet temperature of a cooling water heat transfer tube (5a), and a planned temperature difference, which is a planned value, are computed. Using information on an in-tube fouling temperature difference elevation, which is a difference between the saturation temperature in the condenser (5) and the outlet temperature of the cooling water heat transfer tube (5a) and which is predetermined assuming in-tube fouling of the cooling water heat transfer tube (5a), the temperature difference elevation due to the current in-tube fouling is computed. The extraction device (40) is operated if the elevation of the current temperature difference from the planned temperature difference is greater by a predetermined value or more than the temperature difference elevation due to the current in-tube fouling.

1 . A vapor compression-type refrigerator, comprising:
 a compressor which compresses a refrigerant;   a condenser which condenses the refrigerant compressed by the compressor;   a cooling water heat transfer tube through which cooling water which performs heat exchange between the cooling water and the refrigerant in the condenser flows;   an expansion valve which expands a liquid refrigerant introduced from the condenser;   an evaporator which evaporates the refrigerant expanded by the expansion valve;   an air bleeding device which bleeds gas from the condenser, and includes a cooling unit which cools the gas so as to condense the condensed gas and a discharge unit which discharges an uncondensed gas, which is separated without being condensed by the cooling unit, to an outside; and   a controller which controls the air bleeding device,   wherein the controller calculates a current temperature difference which is a difference between a current saturation temperature in the condenser and a current outlet temperature of the cooling water heat transfer tube, and a planned temperature difference which is a planned value,   wherein the controller calculates an increase in a temperature difference caused by current in-pipe contamination using information on an increase in a temperature difference which is caused by in-pipe contamination and is a difference between a saturation temperature in the condenser predetermined by assuming the in-pipe contamination of the cooling water heat transfer tube and an outlet temperature of the cooling water heat transfer tube, and   wherein in a case where an increase of the current temperature difference from the planned temperature difference is larger by a predetermined value or more than the increase in the temperature difference caused by the current in-pipe contamination, the controller operates the air bleeding device.   
     
     
         2 . The vapor compression-type refrigerator according to  claim 1 , further comprising:
 a differential pressure sensor which detects a differential pressure between an inlet and an outlet of the cooling water heat transfer tube in the condenser,   wherein the increase in the temperature difference caused by the in-pipe contamination is determined based on an increase of a current differential pressure obtained by the differential pressure sensor from the planned value.   
     
     
         3 . The vapor compression-type refrigerator according to  claim 2 , further comprising:
 a cooling water flow rate sensor which measures a flow rate of cooling water which flows through the cooling water heat transfer tube,   wherein the increase in the temperature difference caused by the in-pipe contamination is determined based on the flow rate obtained by the cooling water flow rate sensor.   
     
     
         4 . The vapor compression-type refrigerator according to  claim 2 , further comprising:
 a cold water heat transfer tube through which cold water which performs heat exchange between the cold water and the refrigerant in the evaporator flows; and   a cold water flow rate sensor which measures a flow rate of the cold water flowing through the cold water heat transfer tube,   wherein the controller calculates a flow rate of the cooling water which flows through the cooling water heat transfer tube from a heat balance, based on the cold water flow rate obtained by the cold water flow rate sensor, a cold water inlet/outlet temperature difference of the cold water heat transfer tube in the evaporator, power input to the compressor, and a cooling water inlet/outlet temperature difference of the cooling water heat transfer tube in the condenser, and   wherein the increase in the temperature difference caused by the in-pipe contamination is determined based on the cooling water flow rate.   
     
     
         5 . A method for controlling a vapor compression-type refrigerator,
 the vapor compression-type refrigerator including   a compressor which compresses a refrigerant,   a condenser which condenses the refrigerant compressed by the compressor,   a cooling water heat transfer tube through which cooling water which performs heat exchange between the cooling water and the refrigerant in the condenser flows,   an expansion valve which expands a liquid refrigerant introduced from the condenser,   an evaporator which evaporates the refrigerant expanded by the expansion valve, and   an air bleeding device which bleeds gas from the condenser, and includes a cooling unit which cools the gas so as to condense the condensed gas and a discharge unit which discharges an uncondensed gas, which is separated without being condensed by the cooling unit, to an outside,   the method comprising:   calculating a current temperature difference which is a difference between a current saturation temperature in the condenser and a current outlet temperature of the cooling water heat transfer tube, and a planned temperature difference which is a planned value;   calculating an increase in a temperature difference caused by current in-pipe contamination using information on an increase in a temperature difference which is caused by in-pipe contamination and is a difference between a saturation temperature in the condenser predetermined by assuming the in-pipe contamination of the cooling water heat transfer tube and an outlet temperature of the cooling water heat transfer tube; and   operating the air bleeding device in a case where an increase of the current temperature difference from the planned temperature difference is larger by a predetermined value or more than the increase in the temperature difference caused by the current in-pipe contamination.