CA3036846A1 - Transcritical co2 rink refrigeration system with transcritical energy recovery ejector - Google Patents

Transcritical co2 rink refrigeration system with transcritical energy recovery ejector Download PDF

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CA3036846A1
CA3036846A1 CA3036846A CA3036846A CA3036846A1 CA 3036846 A1 CA3036846 A1 CA 3036846A1 CA 3036846 A CA3036846 A CA 3036846A CA 3036846 A CA3036846 A CA 3036846A CA 3036846 A1 CA3036846 A1 CA 3036846A1
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liquid
rink
gas
inlet
pressure receiver
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Shahin Ss Sadigh Tehrani
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B31/00—Compressor arrangements
    • F25B31/002—Lubrication
    • F25B31/004—Lubrication oil recirculating arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25C—PRODUCING, WORKING OR HANDLING ICE
    • F25C3/00—Processes or apparatus specially adapted for producing ice or snow for winter sports or similar recreational purposes, e.g. for sporting installations; Producing artificial snow
    • F25C3/02—Processes or apparatus specially adapted for producing ice or snow for winter sports or similar recreational purposes, e.g. for sporting installations; Producing artificial snow for ice rinks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/04—Refrigeration circuit bypassing means
    • F25B2400/0401—Refrigeration circuit bypassing means for the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/06—Several compression cycles arranged in parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/16—Receivers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/02—Humidity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/04—Refrigerant level
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/195—Pressures of the condenser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2106—Temperatures of fresh outdoor air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2116—Temperatures of a condenser
    • F25B2700/21163—Temperatures of a condenser of the refrigerant at the outlet of the condenser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2117—Temperatures of an evaporator
    • F25B2700/21171—Temperatures of an evaporator of the fluid cooled by the evaporator

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Control Of Positive-Displacement Pumps (AREA)

Abstract

A C02 rink refrigeration system that injects liquid CO2 from a low-pressure receiver to the rink floor pipes to absorb heat from the rink floor, vaporize, and return to the low- pressure receiver; compresses CO2 vapor from the low-pressure receiver by a low-temperature compressor to enter a CO2 gas cooler; transfers CO2 vapor from the low-pressure receiver by an energy recovery ejector to an intermediate-pressure receiver; transfers liquid CO2 from intermediate-pressure receiver to low-pressure receiver, compresses CO2 vapor from the intermediate-pressure receiver by an intermediate- temperature compressor to enter the CO2 gas cooler; cools CO2 vapor in the gas cooler; delivers CO2 gas cooled by the gas cooler to the high-pressure inlet of the energy recovery ejectors to be directed to the intermediate pressure receiver along with the vapor enters to the energy recovery ejector from the low-pressure receiver where the CO2 will be recirculated in die system.

Description

Description:
A transcritical (note I) CO2 rink refrigeration system with low and intermediate temperature compressor units, transcritical energy recovery ejector unit and direct CO2 cooled rink pipes (note 2) consisting of the following components. This transcritical CO2 rink refrigeration system with low and intermediate temperature compressor units, transcritical energy recovery ejector unit and direct CO2 cooled rink pipes has significant energy consumption, safety and sustainability advantages including substantially high energy efficiency rating (EER) while using nontoxic, nonflammable, recaptured (R744) natural refrigerant with zero global warning potential (GWP).
1) Low pressure receiver: Low pressure receiver holds saturated CO2 liquid and gas, separates CO2 liquid and gas and holds normal CO2 liquid surge volume. The liquid outlet connection of low pressure receiver is connected to CO2 pump unit inlet, the gas outlet of it is connected to inlet of low temperature suction heat exchanger and suction inlet of' energy recovery ejector unit, the liquid and gas inlets of it are connected to rink return header and outlet of liquid make-up valve.
Low pressure receiver is also connected to a pressure sensor and a liquid level probe (sensors).
2) CO2 pump unit: CO2 pump unit circulates CO2 liquid from low pressure receiver to rink supply header via liquid recirculating valve. The inlet of this pump unit is connected to the liquid outlet of low pressure receiver and the outlet of it is connected to the inlet of liquid recirculating valve. The CO2 pump unit requires external power source (electric or other) to operate. CO2 pump unit may not be required if low pressure receiver is sufficiently located above rink supply header (in this case the liquid outlet of low pressure receiver may be connected to inlet of liquid recirculating valve).
3) Liquid recirculating valve: Liquid recirculating valve stops/starts/regulates liquid CO2 flow to rink supply header. The inlet of liquid recirculating valve is connected to outlet of CO2 pump unit and the outlet of it is connected to inlet of rink supply header.
4) Rink supply header: Rink supply header uniformly distributes CO2 liquid to rink cooling pipes. The outlets of rink supply header are connected to supply side of rink cooling pipes and the inlet of it is connected to outlet of liquid recirculating valve.
5) Rink cooling pipes: Rink cooling pipes are placed in rink floor, receive liquid from rink supply header, absorb heat from rink floor, partially evaporate CO2 liquid and convey CO2 liquid and gas to rink return header. The inlets of rink cooling pipes are connected to rink supply header and the outlets of rink cooling pipes are connected to rink return header.
6) Rink return header: Rink return header uniformly collects CO2 liquid and gas from rink cooling pipes. The inlets of rink return header is connected to outlet of rink cooling pipes and the outlet of it is connected to liquid and gas inlet of low pressure receiver.
7) Transcritical energy recovery ejector unit: Transcritical energy recovery ejector unit transfers CO2 gas from low pressure receiver (e.g. around 315 psia or other practical design values) to intermediate pressure receiver (e.g. around 515 psia or other practical design values) by generating sufficient suction at suction inlet of it as a result of high pressure gas flows from gas cooler (e.g. around 1,088 psia or other practical design values) to intermediate pressure receiver based on Bernoulli's principle, regulates gas flow at the high pressure inlet of it to maintain pressure at gas cooler outlet at transcritical operation at proper operating pressure, and prevents reverse flow at suction inlet of it to permit proper transcritical and subcritical operations. The high pressure inlet of the ejector unit is connected to outlet of gas cooler, the outlet of the unit is connected to liquid and gas inlet of intermediate pressure receiver, and suction inlet of it is connected to gas outlet of low pressure receiver. Transcritical energy recovery ejector unit may be made of a single ejector or a group of parallel ejectors including required flow regulating valves.
8) Low temperature refrigeration compressor unit (compressor and motor): Low temperature refrigeration compressor unit transfers CO2 gas from low pressure receiver (e.g. around 315 psia or other practical design values) via suction heat exchanger to gas cooler inlet (e.g. around 1,109 psia or other practical design values) via oil separator. The CO2 outlet of low temperature refrigeration compressor unit is connected to inlet of oil separator (note 4) and the CO2 suction inlet of it is connected to outlet of low temperature suction heat exchanger.
Low temperature refrigeration compressor unit is capable of modulating suction flow to maintain pressure in low pressure receiver around design operating pressure.
The low temperature refrigeration compressor unit requires external power source (electric or other) to operate.
9) Intermediate pressure receiver: Intermediate pressure receiver holds saturated CO2 liquid and gas, separates CO2 liquid and gas and holds normal CO2 liquid surge volume. The gas outlet of it is connected to inlet of intermediate temperature suction heat exchanger, the liquid and gas inlet of it is connected to outlet of ejector unit and the liquid outlet of it is connected to inlet of liquid make-up valve. Intermediate pressure receiver is also connected to a pressure sensor and a high liquid level sensor.
10) Liquid make-up valve: Liquid make-up valve stops/starts/regulates liquid flow from intermediate pressure receiver to low pressure receiver to maintain liquid level in low pressure receiver at design operating level. The inlet of liquid make-up valve is connected to intermediate pressure receiver liquid outlet and the outlet of it is connected to low pressure receiver liquid and gas inlet.
11) Intermediate temperature refrigeration compressor unit (compressor and motor):
Intermediate temperature refrigeration compressor unit transfers CO2 vapor from intermediate pressure receiver (e.g. around 515 psia or other practical design values) via suction heat exchanger to gas cooler inlet (e.g. around 1,109 psia or other practical design values) via oil separator (note 4). The CO2 outlet of intermediate temperature refrigeration compressor unit is connected to oil separator inlet, the CO2 suction inlet of it is connected to intermediate temperature suction heat exchanger outlet. Intermediate temperature refrigeration compressor unit is capable of modulating suction flow to maintain pressure in intermediate pressure receiver around design operating set point. Intermediate temperature refrigeration compressor unit requires external power source (electric or other) to operate.
12) CO2 gas cooler unit: CO2 gas cooler unit (or units) rejects heat from CO2 gas from compressor units discharge temperature to design gas cooler outlet temperature (e.g. around 86 F or other practical design values) and transfers rejected heat from CO2 gas to ambient air and/or heat recovery fluid (to be used for useful heating applications). The CO2 gas cooler may be dry, adiabatic, evaporative and/or fluid cooled. The inlet of CO2 gas cooler unit is connected to outlet of oil separator, and the outlet of CO2 gas cooler unit is connected to high pressure inlet of ejector unit. The CO2 gas cooler unit may require external power source (electric or other) to operate.
13) Discharge oil separator/reservoir unit (note 4) This unit separates compressor carry over oil from discharge gas, returns it to compressor units via oil level sensing devices/oil make-up valve or store it in the reservoir.
14) Oil level sensing devices/oil make-up valves (note 4) Oil level sensing devices/oil make-up valves sense oil level in compressor units and feed oil from oil reservoir to compressor units to maintain oil level in compressor unit at desired operating level.
15) Oil recovery valve (note 4): Oil recovery valve feeds a small stream of liquid from discharge of CO2 pump to inlet of low temperature suction heat exchanger to prevent creation of high concentration of oil in CO2 liquid in the low pressure receiver and rink pipes.
16) Low temperature suction heat exchanger: Low temperature suction heat exchanger provides heat to saturated suction gas and possibly liquid entering low temperature suction heat exchanger to evaporate liquid and slightly superheat gas leaving heat exchanger. The heat source may be external (electricity etc.) or internal (compressor discharge gas upstream or downstream of the gas cooler).
17) Intermediate temperature suction heat exchanger: Intermediate temperature suction heat exchanger provides heat to saturated suction gas and possibly liquid entering intermediate temperature suction heat exchanger to evaporate liquid and slightly superheat gas leaving heat exchanger. The heat source may be external (electricity etc.) or internal (compressor discharge gas upstream or downstream of the gas cooler).
18) Bypass pressure regulator (recommended component): Bypass pressure regulator maintains pressure in intermediate pressure receiver at desired value when low temperature compressor unit is operating, and intermediate temperature compressor unit is not operating. The inlet of this component is connected to gas outlet of intermediate pressure receiver and the outlet of it is connected to gas outlet of low pressure receiver.
19) Refrigeration control system: Refrigeration control system (a central or multiple standalone mechanical, pneumatic, electrical, electronic and/or other style systems) controls components of the refrigeration system. Refrigeration control system senses rink floor temperature, CO2 temperature at high pressure inlet of ejectors, ambient air temperature, ambient humidity (note 6), CO2 pressure in low pressure receiver, CO2 pressure in intermediate pressure receiver, CO2 pressure at high pressure inlet of ejector unit, liquid levels (low, operating, high) in low pressure receiver, high liquid level in intermediate pressure receiver.
Refrigeration control system controls operation of low and intermediate temperature compressor units, CO2 pump unit, gas cooler unit, ejector unit, liquid make-up valve, liquid recirculating valve, oil recovery valve and bypass regulator to maintain rink floor temperature, pressure in low pressure receiver, pressure in intermediate pressure receiver, pressure in high pressure inlet of ejector unit and CO2 liquid level in low pressure receiver at desired design values and monitor high liquid levels in intermediate and low pressure receivers. Note that above sensing and control points are the minimum required/recommended for proper operation of this refrigeration system so applicable local regulatory safeties, desired monitoring and other preferred sensing points and control functions that are not noted on this document shall/may be added to above parameters. The refrigeration control systems may require external power source (electric or other sources) to operate.
20) Interconnecting piping: Interconnecting piping connects the described units and components by this document and depicted by the representative drawing (note 5).
Notes:
Note 1: This system can also operate at subcritical mode when ambient conditions permit.
Note 2: This transcritical CO2 rink refrigeration system with low and intermediate temperature compressor units, transcritical energy recovery ejector unit and direct CO2 cooled rink pipes has significant energy consumption, safety and sustainability advantages including substantially high energy efficiency rating (EER) while using nontoxic, nonflammable. recaptured CO2 (R744) natural refrigerant with zero global warning potential (GWP).
Note 3: CO2 pump may not be required if low pressure receiver is adequately elexated above rink supply header.
Note 4: Oil separator/reservoir, oil level sensing devices/oil make-up valves and oil recovery valve may not be required if oil free compressor units are used.
Note 5: For simplicity service valves. filters, dryers, safety and optional components may not be described by this document and representative drawing.
Note 6: Ambient humidity sensor may be required if adiabatic or evaporative gas cooler is used.

Claims (20)

Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follow:
A transcritical (note 1) CO2 rink refrigeration system with low and intermediate temperature compressor units, transcritical energy recovery ejector unit and direct CO2 cooled rink pipes (note 2) consisting of:
1) Low pressure receiver: Low pressure receiver holds saturated CO2 liquid and gas, separates CO2 liquid and gas and holds normal CO2 liquid surge volume. The liquid outlet connection of low pressure receiver is connected to CO2 pump unit inlet, the gas outlet of it is connected to inlet of low temperature suction heat exchanger and suction inlet of energy recovery ejector unit, the liquid and gas inlets of it are connected to rink return header and outlet of liquid make-up valve.
Low pressure receiver is also connected to a pressure sensor and a liquid level probe (sensors).
2) CO2 pump unit: CO2 pump unit circulates CO2 liquid from low pressure receiver to rink supply header via liquid recirculating valve. The inlet of this pump unit is connected to the liquid outlet of low pressure receiver and the outlet of it is connected to the inlet of liquid recirculating valve. The CO2 pump unit requires external power source (electric or other) to operate. CO2 pump unit may not be required if low pressure receiver is sufficiently located above rink supply header (in this case the liquid outlet of low pressure receiver may be connected to inlet of liquid recirculating valve).
3) Liquid recirculating valve: Liquid recirculating valve stops/starts/regulates liquid CO2 flow to rink supply header. The inlet of liquid recirculating valve is connected to outlet of CO2 pump unit and the outlet of it is connected to inlet of rink supply header.
4) Rink supply header: Rink supply header uniformly distributes CO2 liquid to rink cooling pipes. The outlets of rink supply header are connected to supply side of rink cooling pipes and the inlet of it is connected to outlet of liquid recirculating valve.
5) Rink cooling pipes: Rink cooling pipes are placed in rink floor, receive liquid from rink supply header, absorb heat from rink floor, partially evaporate CO2 liquid and convey CO2 liquid and gas to rink return header. The inlets of rink cooling pipes are connected to rink supply header and the outlets of rink cooling pipes are connected to rink return header.
6) Rink return header: Rink return header uniformly collects CO2 liquid and gas from rink cooling pipes. The inlets of rink return header is connected to outlet of rink cooling pipes and the outlet of it is connected to liquid and gas inlet of low pressure receiver.
7) Transcritical energy recovery ejector unit: Transcritical energy recovery ejector unit transfers CO2 gas from low pressure receiver (e.g. around 315 psia or other practical design values) to intermediate pressure receiver (e.g. around 515 psia or other practical design values) by generating sufficient suction at suction inlet of it as a result of high pressure gas flows from gas cooler (e.g. around 1,088 psia or other practical design values) to intermediate pressure receiver based on Bernoulli's principle, regulates gas flow at the high pressure inlet of it to maintain pressure at gas cooler outlet at transcritical operation at proper operating pressure, and prevents reverse flow at suction inlet of it to permit proper transcritical and subcritical operations. The high pressure inlet of the ejector unit is connected to outlet of gas cooler, the outlet of the unit is connected to liquid and gas inlet of intermediate pressure receiver, and suction inlet of it is connected to gas outlet of low pressure receiver. Transcritical energy recovery ejector unit may be made of a single ejector or a group of parallel ejectors including required flow regulating valves.
8) Low temperature refrigeration compressor unit (compressor and motor): Low temperature refrigeration compressor unit transfers CO2 gas from low pressure receiver (e.g. around 315 psia or other practical design values) via suction heat exchanger to gas cooler inlet (e.g. around 1,109 psia or other practical design values) via oil separator. The CO2 outlet of low temperature refrigeration compressor unit is connected to inlet of oil separator (note 4) and the CO2 suction inlet of it is connected to outlet of low temperature suction heat exchanger.
Low temperature refrigeration compressor unit is capable of modulating suction flow to maintain pressure in low pressure receiver around design operating pressure.
The low temperature refrigeration compressor unit requires external power source (electric or other) to operate.
9) Intermediate pressure receiver: Intermediate pressure receiver holds saturated CO2 liquid and gas, separates CO2 liquid and gas and holds normal CO2 liquid surge volume. The gas outlet of it is connected to inlet of intermediate temperature suction heat exchanger, the liquid and gas inlet of it is connected to outlet of ejector unit and the liquid outlet of it is connected to inlet of liquid make-up valve. Intermediate pressure receiver is also connected to a pressure sensor and a high liquid level sensor.
10) Liquid make-up valve: Liquid make-up valve stops/starts/regulates liquid flow from intermediate pressure receiver to low pressure receiver to maintain liquid level in low pressure receiver at design operating level. The inlet of liquid make-up valve is connected to intermediate pressure receiver liquid outlet and the outlet of it is connected to low pressure receiver liquid and gas inlet.
11) Intermediate temperature refrigeration compressor unit (compressor and motor):
Intermediate temperature refrigeration compressor unit transfers CO2 vapor from intermediate pressure receiver (e.g. around 515 psia or other practical design values) via suction heat exchanger to gas cooler inlet (e.g. around 1,109 psia or other practical design values) via oil separator (note 4). The CO2 outlet of intermediate temperature refrigeration compressor unit is connected to oil separator inlet, the CO2 suction inlet of it is connected to intermediate temperature suction heat exchanger outlet. Intermediate temperature refrigeration compressor unit is capable of modulating suction flow to maintain pressure in intermediate pressure receiver around design operating set point. Intermediate temperature refrigeration compressor unit requires external power source (electric or other) to operate.
12) CO2 gas cooler unit: CO2 gas cooler unit (or units) rejects heat from CO2 gas from compressor units discharge temperature to design gas cooler outlet temperature (e.g. around 86°F or other practical design values) and transfers rejected heat from CO2 gas to ambient air and/or heat recovery fluid (to be used for useful heating applications). The CO2 gas cooler may be dry, adiabatic, evaporative and/or fluid cooled. The inlet of CO2 gas cooler unit is connected to outlet of oil separator, and the outlet of CO2 gas cooler unit is connected to high pressure inlet of ejector unit. The CO2 gas cooler unit may require external power source (electric or other) to operate.
13) Discharge oil separator/reservoir unit (note 4) This unit separates compressor carry over oil from discharge gas, returns it to compressor units via oil level sensing devices/oil make-up valve or store it in the reservoir.
14) Oil level sensing devices/oil make-up valves (note 4) Oil level sensing devices/oil make-up valves sense oil level in compressor units and feed oil from oil reservoir to compressor units to maintain oil level in compressor unit at desired operating level.
15) Oil recovery valve (note 4): Oil recovery valve feeds a small stream of liquid from discharge of CO2 pump to inlet of low temperature suction heat exchanger to prevent creation of high concentration of oil in CO2 liquid in the low pressure receiver and rink pipes.
16) Low temperature suction heat exchanger: Low temperature suction heat exchanger provides heat to saturated suction gas and possibly liquid entering low temperature suction heat exchanger to evaporate liquid and slightly superheat gas leaving heat exchanger. The heat source may be external (electricity etc.) or internal (compressor discharge gas upstream or downstream of the gas cooler).
17) Intermediate temperature suction heat exchanger: Intermediate temperature suction heat exchanger provides heat to saturated suction gas and possibly liquid entering intermediate temperature suction heat exchanger to evaporate liquid and slightly superheat gas leaving heat exchanger. The heat source may be external (electricity etc.) or internal (compressor discharge gas upstream or downstream of the gas cooler).
18) Bypass pressure regulator (recommended component): Bypass pressure regulator maintains pressure in intermediate pressure receiver at desired value when low temperature compressor unit is operating, and intermediate temperature compressor unit is not operating. The inlet of this component is connected to gas outlet of intermediate pressure receiver and the outlet of it is connected to gas outlet of low pressure receiver.
19) Refrigeration control system: Refrigeration control system (a central or multiple standalone mechanical, pneumatic, electrical, electronic and/or other style systems) controls components of the refrigeration system. Refrigeration control system senses rink floor temperature, CO2 temperature at high pressure inlet of ejectors, ambient air temperature, ambient humidity (note 6), CO2 pressure in low pressure receiver, CO2 pressure in intermediate pressure receiver, CO2 pressure at high pressure inlet of ejector unit, liquid levels (low. operating. high) in low pressure receiver, high liquid level in intermediate pressure receiver.
Refrigeration control system controls operation of low and intermediate temperature compressor units, CO2 pump unit, gas cooler unit, ejector unit, liquid make-up valve, liquid recirculating valve, oil recovery valve and bypass regulator to maintain rink floor temperature, pressure in low pressure receiver, pressure in intermediate pressure receiver, pressure in high pressure inlet of ejector unit and CO2 liquid level in low pressure receiver at desired design values and monitor high liquid levels in intermediate and low pressure receivers. Note that above sensing and control points are the minimum required/recommended for proper operation of this refrigeration system so applicable local regulatory safeties, desired monitoring and other preferred sensing points and control functions that are not noted on this document shall/may be added to above parameters. The refrigeration control systems may require external power source (electric or other sources) to operate.
20) Interconnecting piping: Interconnecting piping connects the described units and components by this document and depicted by the representative drawing (note 5).
Notes:
Note 1: This system can also operate at subcritical mode when ambient conditions permit.
Note 2: This transcritical CO2 rink refrigeration system with low and intermediate temperature compressor units, transcritical energy recovery ejector unit and direct CO2 cooled rink pipes has significant energy consumption, safety and sustainability advantages including substantially high energy efficiency rating (EER) while using nontoxic, nonflammable, recaptured CO2 (R744) natural refrigerant with zero global warning potential (GWP).
Note 3: CO2 pump may not be required if low pressure receiver is adequately elevated above rink supply header.
Note 4: Oil separator/reservoir, oil level sensing devices/oil make-up valves and oil recovery valve may not be required if oil free compressor units are used.
Note 5: For simplicity service valves, filters, dryers, safety and optional components may not be described by this document and representative drawing.
Note 6: Ambient humidity sensor may be required if adiabatic or evaporative gas cooler is used.
CA3036846A 2019-03-15 2019-03-15 Transcritical co2 rink refrigeration system with transcritical energy recovery ejector Pending CA3036846A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114459179A (en) * 2021-12-27 2022-05-10 华北理工大学 Carbon dioxide direct evaporation type ice making system for artificial ice rink and using method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114459179A (en) * 2021-12-27 2022-05-10 华北理工大学 Carbon dioxide direct evaporation type ice making system for artificial ice rink and using method thereof
CN114459179B (en) * 2021-12-27 2023-05-12 华北理工大学 Artificial ice rink carbon dioxide direct evaporation type ice making system and application method thereof

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