Evaporator and centrifugal chiller provided with the same

Abstract

Provided is an evaporator capable of, in a centrifugal chiller using a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG, preventing dry-out of a group of heat transfer pipes in an evaporator to increase heat transfer performance and to suppress reduced efficiency due to carryover of the low pressure refrigerant in a liquid phase to a turbo compressor side and a centrifugal chiller provided with same. An evaporator ( 7 ) comprises a pressure container ( 21 ) into which a refrigerant is compressed and introduced, a refrigerant inlet ( 22 ) provided on a lower portion of the pressure container, a refrigerant outlet ( 23 ) provided on an upper portion of the pressure container, a group of heat transfer pipes ( 25 ) that exchange heat with the refrigerant through the interior of the pressure container and a tabular refrigerant distribution plate ( 26 ) installed between the refrigerant inlet and the group of heat transfer pipes and in which refrigerant flow holes ( 26 a ) are drilled. The surface ratio of the refrigerant flow holes per unit area on the refrigerant distribution plate in an area (A 1 ) corresponding to a position near the upstream side of the group of heat transfer pipes is greater than that in another area (A 2 ).

1 . An evaporator comprising:
 a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed;   a refrigerant inlet which is provided in a lower portion of the pressure container;   a refrigerant outlet which is provided in an upper portion of the pressure container;   a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and   a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored,   wherein an area ratio of the refrigerant circulation holes per unit area in the refrigerant distribution plate in a region corresponding to the vicinity of a position on an upstream side of the group of heat transfer pipes is greater than the area ratio thereof in the remaining region.   
     
     
         2 . The evaporator according to  claim 1 ,
 wherein the refrigerant inlet is provided at an intermediate portion in the longitudinal axial direction of the pressure container, and   wherein the area ratio of the refrigerant circulation holes in the refrigerant distribution plate in regions at end portions of the refrigerant distribution plate in the longitudinal axial direction is greater than the area ratio thereof in a region at the intermediate portion in the longitudinal axial direction.   
     
     
         3 . An evaporator comprising:
 a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed;   a refrigerant inlet which is provided in a lower portion of the pressure container;   a refrigerant outlet which is provided in an upper portion of the pressure container;   a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and   a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored,   wherein a plurality of the refrigerant inlets are provided in a dispersed manner along the longitudinal axial direction of the pressure container.   
     
     
         4 . An evaporator comprising:
 a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed;   a refrigerant inlet which is provided in a lower portion of the pressure container;   a refrigerant outlet which is provided in an upper portion of the pressure container;   a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and   a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored,   wherein a cross-sectional flow channel area from an outer opening portion of the refrigerant inlet to the pressure container is enlarged from the outer opening portion toward the pressure container.   
     
     
         5 . An evaporator comprising:
 a pressure container which extends in a horizontal direction and into which a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG is introduced after being condensed;   a refrigerant inlet which is provided in a lower portion of the pressure container;   a refrigerant outlet which is provided in an upper portion of the pressure container;   a group of heat transfer pipes which passes through an inside of the pressure container in a longitudinal axial direction and causes a cooling target liquid to circulate inside the group of heat transfer pipes so as to heat exchange the cooling target liquid with the low pressure refrigerant; and   a tabular refrigerant distribution plate which is installed between the refrigerant inlet and the group of heat transfer pipes inside the pressure container and in which refrigerant circulation holes are bored,   wherein the refrigerant inlet has a shape of a pipe connected to the pressure container, and a flow velocity attenuation member attenuating a flow velocity of the low pressure refrigerant is provided inside the pipe.   
     
     
         6 . The evaporator according to  claim 1 ,
 wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and   wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.   
     
     
         7 . The evaporator according to  claim 1 ,
 wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.   
     
     
         8 . The evaporator according to  claim 7 ,
 wherein the refrigerant circulation holes bored in the refrigerant distribution plate are disposed vertically below the gaps.   
     
     
         9 . The evaporator according to  claim 1 ,
 wherein a demister positioned between the refrigerant outlet and the group of heat transfer pipes inside the pressure container and performing gas-liquid separation of the low pressure refrigerant is disposed immediately above the group of heat transfer pipes.   
     
     
         10 . The evaporator according to  claim 9 ,
 wherein the demister is provided such that the entire circumference thereof is in contact with an inner circumference of the pressure container.   
     
     
         11 . The evaporator according to  claim 1 ,
 wherein each of the heat transfer pipes configuring the group of heat transfer pipes is installed while penetrating a plurality of heat transfer pipe support plates having a plane direction intersecting the longitudinal axial direction of the pressure container and being disposed at intervals in the longitudinal axial direction of the pressure container, and installation intervals of the heat transfer pipe support plates in the vicinity of a position on an upstream side of the group of heat transfer pipes are narrower than the installation intervals of the heat transfer pipe support plates in the remaining position.   
     
     
         12 . A centrifugal chiller comprising:
 a turbo compressor which compresses a low pressure refrigerant used at a maximum pressure of less than 0.2 MPaG;   a condenser which causes the compressed low pressure refrigerant to be condensed; and   the evaporator according to  claim 1  which causes the expanded low pressure refrigerant to evaporate.   
     
     
         13 . The evaporator according to  claim 2 ,
 wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and   wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.   
     
     
         14 . The evaporator according to  claim 3 ,
 wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and   wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.   
     
     
         15 . The evaporator according to  claim 4 ,
 wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and   wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.   
     
     
         16 . The evaporator according to  claim 5 ,
 wherein the group of heat transfer pipes includes a group of outbound pipes extending from one end to the other end in the longitudinal axial direction inside the pressure container, and a group of inbound pipes communicating with the group of outbound pipes at the other end in the longitudinal axial direction inside the pressure container and returning from the other end to the one end in the longitudinal axial direction inside the pressure container, and   wherein the group of outbound pipes is disposed below and the group of inbound pipes is disposed above inside the pressure container.   
     
     
         17 . The evaporator according to  claim 2 ,
 wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.   
     
     
         18 . The evaporator according to  claim 3 ,
 wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.   
     
     
         19 . The evaporator according to  claim 4 ,
 wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.   
     
     
         20 . The evaporator according to  claim 5 ,
 wherein in the group of heat transfer pipes, a plurality of heat transfer pipe bundles each having a plurality of heat transfer pipes bundled therein are arrayed in a horizontal direction and gaps extending in a vertical direction are formed across the heat transfer pipe bundles.