Method and apparatus for staged startup of air-cooled low charged packaged ammonia refrigeration system

Abstract

Apparatus for staged startup of air-cooled low charged packaged ammonia refrigeration system includes motorized valves on condenser coil inlets, a main compressor discharge motorized valve, a bypass pressure regulator valve in the main compressor piping, check valves on the condenser outlets and speed control of the condenser fans. The condenser inlet motorized valves provide precise control of gas feed to the condensers, so pressure can build without collapsing the oil pressure. The condenser coil outlet contains inline check valves to prevent liquid backflow when a coil is isolated. The compressor discharge line contains a single motorized valve for regulating discharge pressure at start-up. The motorized valve in the compressor discharge piping also includes a bypass with a mechanical pressure regulator to allow precise regulation at the minimum discharge pressure. Once discharge pressure rises above the minimum setpoint, the condenser inlet solenoid coils will open one at a time. The discharge pressure regulating motorized valve will simultaneously regulate the discharge pressure until the condenser coil has warmed up enough to maintain discharge pressure.

1 . A refrigeration system comprising:
 a refrigerant evaporator coil,   vapor/liquid separation structure connected to an outlet of said evaporator coil via refrigerant line configured to separate low pressure refrigerant vapor from low pressure refrigerant liquid;   a refrigerant compressor connected to an outlet of said liquid-vapor separation device via refrigerant line and configured to compress refrigerant vapor from said vapor liquid separation structure;   a compressor discharge motorized valve connected to an outlet of said refrigerant compressor via refrigerant line and configured for coarse regulation of discharge pressure during system start-up;   a bypass pressure regulator valve connected to an outlet of said refrigerant compressor via refrigerant line and configured for precise regulation of discharge pressure during start-up;   an air-cooled refrigerant condenser comprising a plurality of condenser coils connected to said compressor discharge motorized valve and said bypass pressure regulator valve via refrigerant line and configured to condense refrigerant vapor produced in said compressor to refrigerant liquid,   a motorized valve connected to an inlet of at least one of said condenser coils configured to provide control of gas feed to the condenser coil to allow pressure to build without collapsing oil pressure;   vertically oriented inline check valve connected to an outlet of at least one of said condenser coils configured to prevent liquid backflow;   a collection vessel connected to an outlet of said condenser via refrigerant line for receiving refrigerant liquid from said condenser;   refrigerant line connecting an outlet of said collection vessel to an inlet of said vapor/liquid separation structure and configured to deliver refrigerant liquid to said separation structure;   said vapor/liquid separation structure having a liquid outlet that is connected via refrigerant line to an inlet of said evaporator coil;   and wherein said vapor/liquid separation structure, said compressor, and said collection vessel, are situated inside a pre-packaged modular enclosure.   
     
     
         2 . A refrigeration system according to  claim 1 , wherein said refrigerant is ammonia. 
     
     
         3 . A refrigeration system according to  claim 1 , wherein said vapor/liquid separation structure comprises a recirculator vessel. 
     
     
         4 . A refrigeration system according to  claim 1 , wherein said collection vessel comprises an economizer. 
     
     
         5 . A refrigeration system according to  claim 1 , further comprising an oil separator vessel configured to separate compressor oil from refrigerant vapor received from said compressor. 
     
     
         6 . A refrigeration system according to  claim 1 , wherein said air-cooled condenser comprises condenser fans and is located on top of or adjacent to said pre-packaged modular enclosure. 
     
     
         7 . A refrigeration system according to  claim 1 , wherein said air-cooled condenser comprises an adiabatic air-pre-cooling system. 
     
     
         8 . A refrigeration system according to  claim 1 , wherein said evaporator coil is mounted in a prefabricated modular evaporator room. 
     
     
         9 . A refrigeration system according to  claim 1 , wherein said evaporator coil is mounted in a refrigerated space adjacent to or below said transportable prefabricated modular enclosure. 
     
     
         10 . A refrigeration system according to  claim 1 , which requires less than ten pounds of refrigerant per ton of refrigeration capacity. 
     
     
         11 . A refrigeration system according to  claim 1 , which requires less than four pounds of refrigerant per ton of refrigeration capacity. 
     
     
         12 . A refrigeration system comprising:
 an air-cooled refrigerant condenser comprising a plurality of condenser coils;   a motorized valve connected to an inlet of at least one of said condenser coils configured to provide control of gas feed to the condenser coil to allow pressure to build without collapsing oil pressure;   vertically oriented inline check valve connected to an outlet of at least one of said condenser coils configured to prevent liquid backflow; and   a transportable prefabricated modular enclosure sized to allow entry of a technician therein for servicing, said transportable prefabricated modular enclosure containing:
 a vapor/liquid separation structure configured to be connected to an outlet of an evaporator via refrigerant line; 
 a refrigerant compressor connected to an outlet of said vapor/liquid separation structure via refrigerant line and connected to an inlet of said condenser via refrigerant line; 
 a compressor discharge motorized valve connected to an outlet of said refrigerant compressor via refrigerant line and configured for coarse regulation of discharge pressure during system start-up;
 a bypass pressure regulator valve connected to an outlet of said refrigerant compressor via refrigerant line and configured for precise regulation of discharge pressure during start-up; 
 
 said compressor discharge motorized valve and said bypass pressure regulator valve connected to said air-cooled refrigerant condenser via refrigerant line, 
 a collection vessel connected to an outlet of said air-cooled refrigerant condenser via refrigerant line; 
 refrigerant line connecting an outlet of said collection vessel to an inlet of said vapor/liquid separation structure; 
 wherein said vapor/liquid separation structure has an outlet that is configured to be connected via refrigerant line to an inlet of an evaporator; 
   said refrigeration system further comprising refrigerant in an amount of less than ten pounds of refrigerant per ton of refrigeration capacity.   
     
     
         13 . A refrigeration system according to  claim 12 , further comprising an evaporator connected to an inlet of said vapor/liquid separation structure and connected to an outlet of said vapor/liquid separation structure. 
     
     
         14 . A refrigeration system according to  claim 13 , wherein said evaporator is mounted in a prefabricated modular evaporator room. 
     
     
         15 . A refrigeration system according to  claim 13 , wherein said evaporator is mounted in a refrigerated space adjacent to or below said transportable prefabricated modular enclosure. 
     
     
         16 . A refrigeration system according to  claim 12 , further comprising a recirculator pump situated in a refrigerant flow path between a fluid outlet of said vapor/liquid separation structure, and an inlet of an evaporator. 
     
     
         17 . A refrigeration system according to  claim 12 , wherein said air-cooled condenser comprises a fan and is configured to be mounted on top of or adjacent to said transportable prefabricated modular enclosure. 
     
     
         18 . A method for start-up of an air-cooled low charged packaged ammonia refrigeration system having an evaporator, liquid/vapor separator, a compressor, an air-cooled condenser having a plurality of condenser coils, and a collection vessel without the need for a stand-alone oil pump to maintain oil pressure during start-up, said method comprising:
 starting refrigerant flow through said condenser coils one at a time until each condenser coil is warm enough to maintain discharge and oil pressure;   using a motorized valve in a discharge line from said compressor for course control of gas flow out of said compressor;   using a bypass pressure regulator valve in said discharge line from said compressor for fine control of gas flow out of said compressor;   using motorized valves at an inlet of at least one condenser coil in said air-cooled condenser to control gas feed to said condenser coil;   using check valves at an outlet of at least one condenser coil to prevent liquid backflow during coil isolation;   monitoring gas pressure in said discharge line from said compressor and controlling the opening of said motorized valves at an inlet of at least one condenser coil based on said monitored gas pressure using a microcontroller or programmable logic controller.   
     
     
         19 . A method for modifying an air-cooled low charged packaged ammonia refrigeration system having an evaporator, liquid/vapor separator, a compressor, an air-cooled condenser, and a collection vessel, said method comprising:
 installing a motorized valves in at least one condenser coil inlet, installing a motorized valve in a main compressor discharge line;   installing a bypass pressure regulator valve in said main compressor discharge line, and   installing inline check valves on at least one condenser coil outlet.   
     
     
         20 . A method according to  claim 19 , comprising installing motorized valves in all but one condenser coil inlet.