PEOPLE

CANADA INFRASTRUCTURE BANK PARTNERS WITH JOHNSON CONTROLS The Canada Infrastructure Bank (CIB) and Johnson Controls have signed an agreement that commits more than $125 million to accelerate private sector decarbonization retrofit projects across Canada.

The agreement sees the CIB investing up to $100 million toward commercial, industrial, manufacturing and multi-residential buildings leveraged through Johnson Controls OpenBlue Net Zero Buildings as a Service offering.

“We are delighted to partner with Johnson Controls … to enable large-scale retrofit projects that will be carried out with no upfront investment from building owners,” said Ehren Cory, CEO, Canada Infrastructure Bank, in a media release.

The CIB’s Commercial Building Retrofit Initiative targets building retrofit projects with a minimum of 30% greenhouse gas (GHG) emission reduction at the building level.

Johnson Controls will identify and manage the retrofit projects and participating organizations will be provided with capital, expertise and solutions.

Over the next five years, the collaboration is expected to reduce GHG emissions by more than 48,000 tonnes per year from the decarbonization of retrofitted buildings. In addition, according to the project parners, the projects are expected to create more than 900 jobs in the trade. <> cib-bic.ca

IN MEMORIAM – Sadly we announce the passing of Pierre Dandurand, who lost his fight with cancer on April 14th. Dandurand was 59. Pierre was devoted to the HVAC industry, and many knew him through Victaulic where he worked since 1990. He was also on the board of the Canadian Institute of Plumbing & Heating (CIPH-Québec) for 10 years, including a term as president in 2008-2010. Bradford White Canada has named Mark Williamson as general manager/sales director and Ian Spalding has been named the company’s assistant general manager/controller. Williamson has more than 30 years of experience in industrial and consumer goods industries, joining Bradford White in 2017 as national sales manager, most recently serving as director of sales and marketing. Spalding has more than 30 years of experience in manufacturing finance and has worked at Bradford White as controller since 2000. Jean-François Charest has joined Thermo 2000 as national sales manager for Canada. Charest brings many years of experience as a sales manager in the HVAC business. He will develop the company’s expansion across Canada. Bob Bettles has taken on the role of senior technical advisor with Powrmatic Canada. Bettles will be responsible for training both sales teams and clients in all six of the company’s branches. He brings experience in trade and wholesale public speaking and training roles. Eric Bodanis is now Ontario sales manager with Calefactio. After 20 years with The Morgan Group, Bodanis joins the Calefactio family to take on new challenges in Ontario.

Dandurand Stelpro has appointed Patrick Charest as vice president, sales and business development. Charest will provide leadership in the planning and execution of sales and customer service strategies across all distribution channels and territories. He has over 25 years’ experience in the manufacturing industry in sales, marketing, and general management. John Galyen, president of Danfoss North America since 2011, has announced his retirement, and Rick Sporrer, vice president sales America for Danfoss Power Solutions, has been appointed to take over the role. Galyen and Sporrer will work together during with transition, with Sporrer fully assuming the position on July 1. Galyen joined Danfoss in 2001 holding various management-level positions prior to his appointment to president. During his 21-year career with Danfoss, he oversaw the company’s grow in North America – from $100 million in annual sales to $3 billion. Sporrer brings more than 30 years of customer and regional expertise and leadership to the new role. Steve Hocurscak has joined Watts as the senior product manager, regulators and automatic control valves (ACVs). He will have overall responsibility for developing and executing new strategies focused on business growth.

Williamson Spalding

J-F. Charest

Bettles Bodanis

P. Charest

Galyen Sporrer

SHOW REPORT > LIVE AND IN PERSON

The HVAC and plumbing industries gather at Spring events. HPAC STAFF

CMPX, the national trade show in Canada, returned after four years. The MEET Show in Moncton attracted nearly 6,000 people. OGC town-hall panel: (l-r) Jeff Hunter, Jim Bolger, Martin Luymes, and Tim Weber.

As pandemic restrictions lifted earlier this year the opportunity for large gatherings returned, and this Spring the HVAC and plumbing industries in Canada were happy to embrace the chance to reconnect and take advantage of trade shows and conferences.

CMPX

The Canadian Mechanical & Plumbing Expo (CMPX) successfully returned to the Metro Toronto Convention Centre March 23-35. The show received 16,059 registrations, more than 1,000 over its 2018 numbers, and just under 9,000 people attended the event over the three days.

“You could feel the energy in the aisles,” said Sandy MacLeod, president/CEO of HRAI. “We were thrilled to hear from so many industry leaders that they were seeing old and new customers at CMPX.”

A total of 2,899 exhibitor representatives spread out over the 68,000 sq. ft. in the North Hall of the convention centre for the show. New this year was the Podcast Hub, which hosted live conversations by HVAC Know it All (Gary McCreadie) and Refrigeration Mentor (Trevor Matthews). The Learning Forum hosted 15 sessions over the three-day show covering a wide range of topics.

“CMPX proved if planned and executed properly tradeshows will continue to be a key element to meet the marketing needs of exhibitors,” reported Ralph Suppa, president and general manager of the Canadian Institute of Plumbing and Heating (CIPH).

MEET SHOW

Atlantic Canada’s largest trade show for the mechanical industry, the Mechanical Electrical Electronic Technology (MEET) Show, returned for two days, May 4 and 5, at the Moncton Coliseum in Moncton, New Brunswick.

Nearly 6,000 attendees made their way to the event, making it a very successful show. “We saw professionals from all across the country showcase the latest technology - from robots to heating units and smart building innovations, there was a lot to take in over the course of two days. We are hearing lots of positive feedback from exhibitors and attendees alike,” said Shawn Murphy, show manager.

ONTARIO GEOTHERMAL ASSOCIATION

tractors, designers, drillers, manufacturers/distributors and industry advocates make up the Ontario Geothermal Association, and the industry came out in force for the association’s 'Closing the Loop Conference,' held Tuesday, April 26th, at the Hilton Mississauga.

OGA president Jeff Hunter welcomed the crowded conference room, acknowledging the strong attendance as a sign of the growing interest in geoexchange technology.

On-hand to introduce the keynote was Carlyle Coutinho, CEO of Enwave (the event’s lead sponsor) who announced the official launch of the company’s Geo-Communities business.

The keynote included highlights from ground source heat pump research projects commissioned by HRAI and OGA, and Martin Luymes of HRAI explained how details of the research is being shared with governments and utilities across the country.

The day-long conference featured a series of educational sessions highlighting the benefits and efficiencies of geoexchange systems, the opportunities ahead for the technology, along with the ongoing challenges the sector faces in building momentum and fulfilling its climate-friendly promise. <>

SHIFTING GEARS, SLOWLY

More hybrid and electric options are joining the service vehicle line-ups, but if you want one today the choices are still limited. BY JIL McINTOSH

Last year was an unusual one for the auto industry, as companies struggled with pandemic-related supply chain issues and, most notably, a shortage of microprocessor chips that stalled production. If you order a new vehicle, you may wait longer for delivery. It may also be missing certain features, such as heated seats, that dealers will retrofit once the chips come in.

Many companies are bringing in electric work vehicles, and some are listed among the brands below. Electric options will bring down your fuel bills and cost less to maintain, but remember that their stated range is an estimate and cold weather reduces it, and you’ll have to install charging stations to keep them going. Following is a complete listing of your service truck and van choices for 2022.

FORD

An all-new model for 2021, the F-150 receives only minor upgrades for 2022. New features include onboard scales, which can measure the payload weight, and Smart Hitch, which measures tongue weight. The 3.0-liter Power Stroke diesel has been discontinued.

Cab choices are regular, supercab, and supercrew. Turbocharged engine choices, called EcoBoost, are a 2.7-litre V6 or 3.5-litre V6; non-turbo engines are a 3.3-litre V6 and 5.0-litre V8. The F-150 hybrid uses the turbo 3.5-litre, and automatically switches between gas, electricity, or a combination.

The newest F-150 is the all-electric Lightning. Depending on the model, it’s expected to have a range of 370 to 515 km on a charge, make up to 775 lb-ft of torque, and tow up to 10,000 lbs.

Super Duty models, the F-250, F-350 and F-450, receive minor upgrades for 2022, including an available 12-in. touchscreen, while King Ranch and Platinum trims come only with 4x4. Cab choices are regular, supercab and supercrew, and engine choices are a 6.2-litre V8, 7.3-litre V8, or 6.7-litre Power Stroke diesel that makes 1,050 lb-ft of torque.

The full-size Transit van gets some new features, including an automatic idle shut-off with timer and new shelving options. It comes with two versions of a 3.5-litre V6, one turbocharged; with available crew van seating; and in three lengths and three roof heights. New this year is the E-Transit all-electric version. It has the same configurations and interior dimensions, gets approximately 203 km on a charge, and offers an available on-board generator.

The compact Transit Connect cargo van comes with a 2.0-litre four-cylinder engine and can be ordered with a rear liftgate or cargo doors.

F-150

F-150 LIGHTNING PRO E-TRANSIT TRANSIT CONNECT

GENERAL MOTORS

SILVERADO EXPRESS

SAVANA

The mechanically-twinned Chevrolet Silverado and GMC Sierra receive a refresh for 2022, including new styling and interiors, new driver safety-assist technologies, 20% more torque on the 2.7-litre engine, and a 4,000-lb towing increase on diesel-equipped trucks to a maximum 13,300 lbs.

Both brands are available in regular, double and crew cab. Engine choices are a 2.7-litre turbo four-cylinder; 5.3-litre V8; 6.2-litre V8; and 3.0-litre inlinesix turbodiesel. The last-generation models are also being built as the lower-priced Silverado Limited and Sierra Limited. There will also be an allelectric Silverado by 2024. It will feature an integrated bed and “mid-gate” cargo bed extension, similar to the discontinued Chevrolet Avalanche.

The heavy-duty Silverado and Sierra are unchanged for 2022, and come in 2500 and 3500 configurations, in regular, double and crew cab. The two available engines are a 6.6-litre V8, or a 6.6-litre V8 Duramax turbodiesel that makes 910 lb-ft of torque. Available features include eight cameras, with hitch views and a “transparent trailer” view of what’s behind the trailer.

The Chevrolet Express and GMC Savana cargo vans come in 2500 or 3500 configurations, in regular or extended wheelbase. It’s a very old design and with no major updates for 2022, but it’s a proven vehicle and upfits can be easily moved from older versions. Available engines are a 4.3-litre V6, a 6.6-litre V8, or 2.8-litre Duramax four-cylinder turbodiesel.

GM’s new BrightDrop division will produce all-electric delivery vans at its facility in Ontario. The EV600 light-duty van is expected to have a 400-km range and be available to order this year.

BRIGHTDROP

The full-size Sprinter comes with a choice of a 2.0-litre four-cylinder gasoline engine; a 2.0-litre turbodiesel engine; or 3.0-litre V6 turbodiesel engine. Available configurations are 2500, 3500, 3500XD heavy-duty, and 4500. The cargo version comes in three lengths, and with a standard or high roof. There’s also a five-passenger crew van, in high-roof and with two lengths.

Some models are available with all-wheel drive, which is updated for 2022. While the old system split the torque 35/65 front to rear, the new system varies the power distribution as needed for traction. There’s also a new Speed Delivery Door that automatically opens and closes when unloading, but it’s more suited for parcel delivery.

An electric eSprinter is sold in Europe, and it’s expected to be available in Canada in 2023 or 2024, built in the U.S. The Metris is the only midsize cargo van in our market, and is unchanged for 2022. Available in two lengths, it uses a 2.0-litre turbocharged four-cylinder with nine-speed automatic, and is rear-wheel-drive. The van can be optioned with a liftgate, or with a choice of dual cargo doors that open either 180 degrees or 270 degrees.

SPRINTER

METRIS

RAM

The Ram 1500 gets new trim packages for 2022 and options including an LED light that illuminates the hitch. The truck comes only in Quad or Crew Cab. Engine choices are a 3.6-litre V6, a 5.7-litre V8, or a 3.0-litre V6 turbodiesel. Standard on the gasoline V6, and optional on the V8, is a mild hybrid system called eTorque. The self-charging system adds electric torque on acceleration to improve fuel economy, but can’t run on its battery alone. Ram is planning an all-electric truck, expected to arrive for 2024.

The last-generation Ram from 2018 is still being built as the lower-cost 1500 Classic. It comes in regular, quad and crew cab, with 3.6-litre V6 or 5.7-litre V8 but without eTorque, and the diesel isn’t available.

The Ram 2500 and 3500 come in regular, crew, or mega cab, which devotes most of its extra length to storage behind the rear seat. Updates for 2022 include an all-new infotainment system and an LED light for the trailer hitch. Engine choices are a 6.4-litre V8 or 6.7-litre Cummins turbodiesel, which makes 850 lb-ft of torque. The 3500 further offers a high-output 6.7-litre diesel that makes 1,075 lb-ft of torque. An optional rear air suspension levels the truck when it’s loaded.

Ram’s full-size ProMaster cargo van upgrades its six-speed automatic to a nine-speed for 2022, and adds a fivepassenger crew van. New features include wireless phone connectivity and Wi-Fi capability.

The ProMaster uses a 3.6-litre V6 and is front-wheel-drive. That’s unique in the full-size segment and gives it a lower step-in height. It comes in 1500, 2500 and 3500 rating, with three wheelbase lengths, four body lengths, and two roof heights.

The compact ProMaster City cargo van receives some new standard features for 2022, including driver’s-seat height and lumbar adjustment, cruise control, and backup sensors. It uses a 2.4-litre four-cylinder engine and can tow up to 2,000 lbs.

3500 HEAVY-DUTY

1500 PROMASTER

PROMASTER CITY

TOYOTA

The Toyota Tundra is an all-new model for 2022, with a fullyboxed frame and redesigned suspension. The “i-Force” uses a new twin-turbocharged 3.5-litre V6, while the “i-Force Max” adds a hybrid system. Both use a 10-speed automatic transmission, and the hybrid is self-charging and can run on its battery alone at lower speeds. Both engines are available in 4x2 or 4x4. Maximum towing is 12,000 lbs for the i-Force, and 11,170 lbs for the hybrid.

The i-Force comes in double cab or crewmax, while the hybrid is crewmax only. Both come standard with driver-assist technologies including adaptive cruise control, emergency front braking, and lane-keeping assist.

MIDSIZE TRUCKS

FORD RANGER FORD MAVERICK TUNDRA

CHEVROLET COLORADO

While midsize trucks won’t handle the big jobs, they could be just right for lighter-duty such as service calls where a big truck isn’t necessary. There are a number of models to choose.

Ford’s midsize Ranger is unchanged for 2022, and uses a turbocharged 2.3-litre four-cylinder engine with standard 4x4. It’s available in supercab with six-foot bed, or supercrew with five-foot bed, and can tow up to 7,500 lbs. There’s also the all-new compact Maverick, with gasoline engine or hybrid powertrain, and while it’s intended primarily for consumers, some companies are successfully using it for business.

General Motors offers the mechanically-twinned Chevrolet Colorado and GMC Canyon in extended cab, or in crew cab with two box lengths. Along with a 2.5-litre four-cylinder and 3.6-litre V6, these two trucks offer a 2.8-litre turbodiesel, and that gives you up to 7,700 lbs of towing capacity.

The Honda Ridgeline is also more consumer than commercial, but it’s still a very capable worker with its 3.5-litre V6 and standard all-wheel drive, and a dual-hinged tailgate that opens conventionally or sideways like a door, for easy access to cargo.

Nissan has a new Frontier, its only truck now that the Titan has been discontinued in Canada. It comes in king cab or crew cab, with a 3.8-litre V6, standard 4x4, and a top towing capacity of 6,490 lbs.

The Toyota Tacoma comes in access cab or double cab, with 3.5-litre V6 and standard 4x4, and can tow up to 6,500 lbs. <>

GMC CANYON NISSAN FRONTIER TOYOTA TACOMA

Jil McIntosh is an automotive writer and reviewer with a specialty in trucks and commercial vehicles. McIntosh writes for several outlets and is a member of the Automobile Journalists Association of Canada (AJAC). Her work can be found at WomanOnWheels.ca.

WHY CO2?

– PART II

Re-visiting the return of CO2 as a refrigerant solution for supermarket applications.

BY DAVE DEMMA

In the last issue of HPAC (March 2022) I wrote about the re-emergence of CO2 as a refrigerant being used in supermarket applications in North America. I’ve returned to share more on the subject, specifically some of the key differences between a CO2 system and our more common HCFC/ HFC refrigerant systems in place today, and also to share some potential system set-ups required to work with CO2.

CO2 DIFFERENCES

1. Higher Pressures: while CO2 pressures are higher than those experienced with HCFC/HFC refrigerants, this is not the first refrigerant to enter the marketplace with substantially higher pressures than the industry’s mainstay refrigerants.

See Table A for a comparison between former mainstay refrigerants and the new refrigerant designed to replace it. The most recent example of this would be the higher pressures seen in an R-410A system as compared to an R-22 system. While it’s not of the same magnitude as the increase between CO2 (R-744) and R-404A, it’s still a good example. 2. At a given saturation temperature, the CO2 pressure will be substantially higher than HCFC/HFC refrigerants. For example, at a -20F SST, the corresponding pressure will be 200 PSIG. Because of the higher pressures, you may see Type K copper, steel, stainless steel, or hybrid copper-steel piping, depending on the application.

For example, the maximum allowable working pressure for the CO2 LT Secondary system is 400 PSIG. This would be the rating for the system relief valves. As such, the copper tubing will need to have a MAWP rating of at least 400 PSIG. The 1-⅝-in. and 2-⅛-in. Type L copper tubing does not meet that rating, requiring Type K to be used for those two sizes. 3. The CO2 might be used as a secondary heat transfer fluid. 4. Insulation wall thickness will be 1-in. in mild conditions (80F dry bulb, 50% RH), 1-½-in. in normal conditions (85F dry bulb, 70% RH), and 2-in. in severe conditions (90F dry bulb and 80% RH). 5. Piping in display cases must be insulated. 6. Available in several different purity grades (as opposed to a single grade for HCFC/HFC refrigerants). The Coleman Grade, with a purity of 99.99%, is the recommended minimum grade for refrigeration applications. 7. CO2 has a greater volumetric cooling capacity as compared to common HFCs. For example, in a -20F application, R-404A has a latent heat of vaporization of 81 Btu/lb-min. In the same application CO2 has a latent heat of vaporization of 130 Btu/lb-min. The resulting mass flow requirement for CO2 will be approximately 38% less, with the benefit of smaller compressor displacement and smaller pipe sizes. 8. Due to the high operating pressures you will see more pressure relief valves. Anyplace in the system where liquid CO2 could be trapped with an isolation valve closure will require a relief valve piped in parallel. This allows a flow path for the potential high pressure CO2 in the isolated portion of the system to vent back to the main receiver vessel. 9. System Charging: after evacuating, break system vacuum with vapour only. The triple point occurs at 75 PSIG, charging liquid into a system which is at a pressure less than 75 PSIG will allow triple point conditions, meaning that some portion of the liquid will turn into a solid. This is known as deposition (or desublimination). It would certainly be unfortunate if dry ice were to form inside the system piping during charging. The system should be pressurized to somewhere between 200 PSIG to 250 PSIG to avoid this scenario.

In the previous article I covered a series of important definitions including: critical point, critical temperature, critical

Table A. Pressure comparisons between refrigerants.

Table B. Pipe requirements CO2 secondary.

pressure, triple point, sublimation, subcritical and transcritical. Before we walk through four types of CO2 systems that might be present in a new application, let’s cover a few more system-related definitions: • Direct Expansion: A refrigeration system which includes a compressor, condenser, evaporator coil and some variety of expansion device. • Primary Refrigerant: A refrigerant which is used to lower the temperature of a secondary heat transfer fluid. For example, R-407A or R-448A could all be applied as a primary refrigerant. • Secondary Heat Transfer Fluid: A fluid used to transfer heat from the refrigerated space to the primary refrigerant. • Single-Phase Secondary Heat Transfer Fluid: A secondary fluid which absorbs heat by experiencing a sensible heat gain (temperature increase, but no change of state) • Two-Phase Secondary Heat Transfer

Fluid: A secondary fluid absorbs heat by experiencing a latent heat gain, resulting in change of state. • Cascade System: A system having two (or more) refrigerant circuits, where the evaporator of one circuit provides the heat transfer capacity necessary to accomplish condensing in the second circuit. The cascade evaporator/condenser will typically be of the brazed plate heat exchanger type. • Upper Cascade: The refrigerant circuit in the cascade system which provides heat transfer capacity to the condenser in the second circuit.

The heat transferred to the refrigerant in this system is rejected to some type of heat sink, typically an air cooled condenser, evaporative condenser, or water cooled condenser. • Lower Cascade: The refrigerant circuit in a cascade system which transfers heat from the refrigerated

Figure 1: CO2 Secondary – Liquid Overfeed System

spaces, and transfers that heat to the upper cascade.

CO2 SECONDARY – LIQUID OVERFEED SYSTEM

This system will use a separate direct expansion system, whose purpose is to maintain a secondary heat transfer fluid at a specific temperature. It is similar in concept to a chiller system cooling down propylene glycol, which is then pumped to the various display cases and walk-in boxes, and used as the medium to transfer heat from those refrigerated spaces. The obvious difference being that CO2 has replaced the propylene glycol as the secondary fluid.

Why bother using CO2 for this application?

Glycol has been used with success as a secondary fluid in medium temperature applications. While a second stage of heat transfer will add some inefficiency, because the chiller negates pumping refrigerant to each display case and walk-in box, it does allow a huge reduction in refrigerant charge. Unfortunately, glycol is not suitable as a secondary fluid for low temperature applications. So, this method of reducing the refrigerant charge has not been an option for low temperature systems.

CO2 allows secondary systems to become a viable option for low temperature applications. As opposed to the sensible heat transfer process which propylene glycol offers, CO2 offers the added heat transfer benefit of a fluid experiencing a change of state, which makes it a more efficient process. This, plus the fact CO2 has a greater volumetric cooling capacity, will allow for the use of smaller pipe sizes.

Figure 1 shows a typical piping/component diagram for a CO2 Secondary – Liquid Overfeed System. This being a cascade system, an HFC system will provide the heat transfer capacity necessary to condense the CO2 vapour into a liquid. Note that the lower cascade (the CO2 portion) does not use a compressor.

We’ll start at the Liquid Vapour Separator, which receives the liquid/ vapour mixture returning from the evaporators, and separates the two phases in the vessel.

Liquid from the bottom of the vessel enters the pump inlet, which provides

necessary pressure differential to supply liquid CO2 to the various evaporators connected to the system. As with any other refrigeration system, a main liquid filter-drier will be used to remove harmful contaminants from the CO2. From there, the CO2 enters a liquid header, where individual liquid circuits will supply CO2 to each evaporator.

This is a liquid overfeed system where the CO2 flowing to the evaporators is already at the design SST. As such, no expansion device is required.

In addition, the evaporators are circuited for the overfeed application. A solenoid valve at the inlet of the evaporator, controlled by either a standalone temperature controller, or the system’s central energy management controller, will regulate the flow of CO2 to each evaporator.

When the temperature is above the set-point, the solenoid valve coil will be energized, allowing the valve to open. Liquid CO2 will flow through the evaporator, changing state as it absorbs heat from the refrigerated space. A mixture of liquid and vapour CO2 will flow back to the Liquid Vapour Separator, with the liquid settling to the bottom, and the vapour rising to the top.

The cooler temperature occurring in the cascade evaporator/condenser will facilitate the flow of vapour from the separator to the condenser, resulting in a change of state from vapour to liquid, replenishing the liquid supply in the separator.

CO2 LT DIRECT EXPANSION CASCADE – SUBCRITICAL

Think of this as a typical vapour compression cycle, with CO2 as the refrigerant in the system. The only difference between a standard vapour compression cycle and the DX Cascade – Subcritical system is the fact that the heat transfer capacity necessary to condense the high temperature/high pressure vapour leaving the compressor into a high pressure/high temperature liquid is provided by an HFC refrigeration system, with the heat transfer taking place in a cascade evaporator/condenser (Figure 2).

Starting at the compressor: low temperature/low pressure vapour flows from the evaporators to the suction manifold, where it is then dispersed to whichever compressors happen to be operating at any given time.

The compressors will compress the vapour, with a high temperature/high pressure vapour exiting the compressor. As common in a typical HFC multicompressor rack, the discharge vapour flows to an oil separator before entering the condenser.

Figure 2: CO2 Low Temperature Direct Expansion Cascade – Subcritical System

Figure 3 – CO2 MT Liquid Overfeed/LT DX Cascade – Subcritical.

Again, the main difference in this system is that rather than a traditional condenser, the discharge vapour enters the cascade evaporator/condenser. Here the HFC system provides the heat transfer capacity necessary to condense the CO2 discharge vapour mass flow into a liquid.

From here on, the system is nearly identical to a standard HFC system, with the liquid refrigerant flowing into a receiver, through a filter-drier and sight glass, then onto a liquid header.

Here the individual system branches are supplied liquid as necessary. Electric expansion valves have become a standard feather in LT CO2 applications, taking the high temperature/high pressure liquid and allowing it to experience a pressure drop to bring the liquid to the design SST.

The liquid vapour mixture enters the evaporator, absorbing heat from the refrigerated space, and fully changing state into a vapour before the evaporator outlet. In the diagram in Figure 2, an electric suction line regulator is shown as the method for maintaining constant discharge air temperature.

CO2 MT LIQUID OVERFEED/LT DX CASCADE – SUBCRITICAL

The system in Figure 3 shows a hybrid system, a combination of the two previously discussed systems.

The addition of the MT liquid overfeed portion requires the receiver to be of the liquid/vapour separator design. Liquid from the separator is pumped to both the LT and MT evaporator systems, with the MT operating as flooded evaporators and the LT operating as DX evaporators.

The liquid/vapour mixture leaving the MT evaporators and the discharge vapour leaving the LT compressors are piped together via a tee, and then flow into the liquid/vapour separator. From here, vapour condensation is accomplished as the lower temperature in the cascade evaporator/condenser draws the vapour from the top of the separator.

CO2 BOOSTER – SUBCRITICAL/ TRANSCRITICAL SYSTEM

The final system is the granddaddy of sustainability, as it eliminates the need for any refrigerant other than CO2.

As such, in ambient conditions where the resulting saturated condensing temperature will be greater than 87.9F the system must operate in the transcritical region. Since above the critical point the CO2 will not exist as a liquid, this presents a challenge that must be dealt with by different system design/components (Figure 4).

This is a two stage (compound) compression system, which in principle isn’t unlike the many R-22 two-stage that saw use after R-502 was phased out.

The idea is that compressing the vapour from the low temperature evaporator systems in two stages allows for greater compressor efficiency by reducing the operating compression ratio of all compressors.

Vapour from the LT evaporator systems enter the LT compressors, which raise the low pressure to an intermediate pressure corresponding with the MT vapour pressure. The discharge vapour from the LT compressors flow through an oil separator, and then enters the suction manifold to the MT compressors.

Here, the LT discharge vapour is joined by the vapour leaving the MT evaporator systems, and the entire system mass flow then enters the MT compressors.

The discharge vapour leaving the MT compressors will first flow through an oil separator before entering the gas cooler.

Now, if the ambient conditions are such that the SCT is less than 87.9F, the CO2 vapour will indeed condense into a liquid. In this condition, the system will operate similar to a typical vapour compression cycle, with the liquid leaving the gas cooler flowing into the receiver, and supplying the liquid header as needed.

But for those times when the SCT is above 87.9F, the gas cooler transfers heat from the discharge vapour without a change of state taking place. This “neither liquid nor vapour” mixture enters the flash tank, where the “flash tank bypass valve” will vent the high pressure to the suction manifold of the MT compressors.

Continued on p53

22_0883_HPAC_MAY_CN Mod: April 4, 2022 9:54 AM Print: 04/19/22 2:50:33 PM page 1 v7

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