16 minute read
Refrigeration
from March 2022
In heat pump systems, energy is rejected to a hot reservoir at the desire temperature while using as little energy as possible.
Refrigeration systems and heat pumps are similar in theory; the difference is based on which portion of the heat transfer is of interest to the expert. By Greg Scrivener
As promised in the previous issue, the discussion on heat pumping continues. Since we want to have a more in-depth look at several of the more challenging aspects of heat pumps in commercial and industrial settings in future issues, we are going to take a quick step back and go through a few of the fundamentals.
Most of us were probably taught the second law of thermodynamics in several of its forms at some point in our lives. Maybe this lesson was done in school or maybe it was an outcome of some life experience. I remember vividly one particular instance of putting my thumb into a car lighter as a young boy (it had such cool-looking red circles; how could I resist?). As soon as my thumb touched that glowing red heating element, the energy from the hot element moved into my thumb
Continued on page “45”
Continued from page “43”
and burnt my skin badly. As I jumped out of the car and put my thumb in a puddle, I was certainly not thinking as Rudolf Clausius did in 1854 when he was laying a foundation for the second law of thermodynamics — that “heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time.” Yet, I certainly knew that the “hot” moved from the lighter into the “cold” of my thumb. The fact that energy transfers as heat from hot to cold is intuitive to most people – the warm drink doth not make the ice cube colder. Figure 1 best represents this energy transfer.
Transferring energy from cold to hot takes some other change, connected therewith, occurring simultaneously. The way to do this is to have an engine or machine that can force the heat to move in the other direction; probably the most common type of machine we have that works in this way is the vapour compression refrigeration cycle we talk about all the time. Figure 2 represents the energy movement with a refrigeration system added. Engines and machines require some form of energy to accomplish this effect.
Balanced system
You may also remember that conservation of energy is necessary for any closed system. In our case here, the machine in Figure 2 cannot magically produce or destroy energy. This means that the sum of the energy coming in from the cold reservoir and the energy being used to run the machine must equal the energy leaving into the hot reservoir. In other words:
If we substitute a simple vapour compression system into our “machine,” we end up with Figure 3. This theory is now approaching something we have discussed many times here before: the amount of heat we need to reject in our condenser is equal to the amount of energy we put in our compressor plus the heat we absorbed in the evaporator.
A refrigeration system and a heat pump are conceptually the same thing; the differences lay in which portion of the heat transfer we really care about. In a refrigeration system, we want to optimize the energy absorbed from a cold reservoir at some desired temperature using as little energy as possible. In a heat pump system, we want to optimize the energy rejected to a hot reservoir at some desired temperature using as little energy as possible. These desires can lead to different challenges and applications of technology to enhance refrigeration and heat pump systems differently. And of course, nothing is stopping us from wanting both the heat rejection and the cooling effect at the same time.
Heat pump dryers
The application of heat pump technology is increasing and there is a drive to push the technology in an increasing number of applications and in colder climates. Three
Figure 1: Heat will spontaneously move from hot to cold and not the other way around. Figure 2: A machine, like a vapour compression refrigeration system, can move energy from cold to hot. Figure 3: A system that moves heat from cold to hot using vapour compression.
Continued on page “47”
Continued from page “45”
main applications that are currently standard fare in residential applications: 1. Space heating 2. Water heating 3. Clothes drying
Products using heat pumps are widely available for each of these applications. In the last issue, we discussed some of the challenges with residential space heating applications and, particularly, how the outdoor climate affects their performance. Just as we did with the space heating, we need to pay attention to details in order to understand which type of system is good for a specific application.
Heat pump clothes dryers are expensive to buy and repair but they operate more efficiently than their resistance heating element. We will be going through the
rationale behind a lot of the energy-saving associated with using heat pumps in an upcoming issue but in simple terms, a heat pump dryer uses about 50 per cent less energy per load of laundry compared to a standard resistance electrical model.
Venting for heat pumps
This analysis is complicated because you must add the effects the dryer has on the house. For example, a normal clothes drier requires that air from the house is exhausted outside which means that you have to bring in fresh air to your house to replace this exhaust. A heat pump dryer doesn’t have a vent outside so there is not the same need to bring in and heat/cool outside air. However, as we have learned about refrigeration systems, our condenser must reject both the energy put into the compressor and the energy absorbed in the evaporator. This means that a refrigeration system running in a closed room (i.e., put a fridge in a sealed room and leave the fridge door open) will always heat up the room.
One of the ways that evaporators absorb energy is by condensing water in the air, which is obviously the main purpose of the evaporator in a heat pump dryer. If you put electricity into a heat pump clothes dryer and you remove water onto the evaporator while cooling the air, there must be a net heat energy input into your home. In the winter this would help with heating costs and in the summer, it would add to the air conditioning load. Whether this technology makes sense depends on how much laundry you do and how much your electricity costs. For high laundry volumes in areas with expensive electricity, this technology becomes quite appealing. And if you have no way to install a vent it’s a no-brainer.
You may be wondering why we spent so long talking about clothes dryers in a refrigeration article. Well, in short, this is the exact same thing we can do with commercial and industrial heat pumps in large commercial laundries, indoor agricultural facilities, ice rinks and many other industrial processes. As we continue to move forward with decarbonization, there will be more and more applications that use these types of systems. In the next issue, we will talk about water heating with heat pumps. :
Greg Scrivener is the lead refrigeration engineer and a partner at Laporte Consultants, Calgary, and works throughout Canada and the U.S. He is a professional engineer and journeyperson refrigeration mechanic. He can be reached at GScrivener@laporteconsultants.com.
FOR USE ON THREADED: ABS, PVC, CPVC, Delrin*, Zytel*, Fiberglass, Nylon, Polypropylene, Polybutylene, Polyethylene, Celcon**, Cycolac***, and all types of metals including: Stainless Steel, Iron, Copper, Galvanized, Brass and Aluminum.
PRESSURE RANGE USE: Gases: Up to 5,000 PSI (351.5 kg/cm2) Liquids: Up to 10,000 PSI (703.1 kg/cm2)
TEMPERATURE RANGE USE:
PART NO. SIZE: 507125 118ml Brush top can 507250 237ml Brush top can
*Dupont registered trademark **Celanese registered trademark ***General Electric Plastics registered trademark
disassembly after years of service. • Zero VOC • Triple Lubricating • Adheres to Oily Threads • Nontoxic / Noncombustible • Safe for PVC & CPVC • Taste and Odor-Free
than typical thread paste reduces the need
Graphite reduces friction d between the thread of the pipe and thread of the fitting.
Approved for Natural Gas, and Butane
Ceramic Microspheres Ce act like mini ball bearings that lubricate then compress to form a positive seal.
pw-G/dwv/sw
Suitable for use on systems carrying:
Ammonia Fatty Acids Jet Fuel Refrigeration Gases †
Upgraded camera reel Ridgid, Elyria, Ohio, has introduced the SeeSnake rM200 camera reel with TruSense to the market. Ideal for tackling lines up to 200 ft. in length and one-and-a-half to eight inches in diameter, the rM200’s new camera functionality features TruSense technology with high dynamic range imaging and TiltSense inclinometer for in-pipe vision. The use of TruSense establishes a two-way datalink between the camera head and a connected Ridgid SeeSnake Wi-Fi enabled monitor. The rM200 also has enhanced transport and storage features. Ridgid www.ridgid.com Flexible shaft drain cleaner General Pipe Cleaners, McKees Rocks, Pennsylvania, unveiled the Flexi-Root 100, its latest flexible shaft drain cleaner. The Flexi-Rooter 100 shaft spins more than 10 times faster than drum machines, reaching up to 2,200 RPM. The Flexi-Rooter 100 offers a stronger shaft with the strength to cut through roots in four-inch lines yet flexible enough to negotiate two-inch lines. It features an integral variable speed motor with a foot pedal to allow contractors the ability to use both hands to safely guide the flexible shaft into the line. General Pipe Cleaners www.drainbrain.com
Power tube expander Navac, Mississauga, Ont, unveiled its latest product — the NTE11L BreakFree power tube expander. The NTE11L features a longlasting rechargeable lithium battery that allows up to 200 expansions on a single charge. The battery and charger are also compatible with Navac’s NEF6LM BreakFree power flaring tool. The NTE11L comes with quick connect heads sizing in 3/8-inches, 1/2 inches, 5/8 inches, 3/4 inches, 7/8 inches, one-inches and one-anda-eighth inches. The NTE11L also comes with a two-year warranty. Navac www.navacglobal.com
An ammonia leak could cause lethal results if not contained properly, making safety training essential for refrigeration
mechanics. (Photo courtesy of the Ammonia Safety Training Institute)
The hole left by the phasing down of HFCs presents the opportunity for lower GWP refrigerants to fill in that supply gap. By Leah Den Hartogh
Countries around the world are phasing down higher global warming potential (GWP) refrigerants in favour of those that offer lower levels of GWP. This presents the refrigeration industry the opportunity to lead the built environment into the net-zero era. “In the past 35 years, we have seen trerefrigerants available at the most basic level. Within each of those categories, it gets much more complicated. Synthetic refrigerants are broken down into mainly four types: chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and the newest
addition, hydrofluoroolefin (HFOs). Each containing its own generation of refrigerants; HFOs have the lowest GWP amongst the synthetics, followed by HFCs, HCFCs, and CFCs.
Natural refrigerants have been commer-
Both natural and synthetic refrigerants will be important in filling the supply gap left open by the phase-down of high GWP refrigerants.
mendous change in our industry as countries around the world have chosen to move to products and refrigerants that are less damaging to our environment and impact global warming, ” said Dennis Kozina, director of sales for Canada at Emerson.
When it comes to products within the marketplace, there are synthetic and natural
Continued on page “53”
From Exploring New Frontiers To Energy Efficiency Pioneers
At Mitsubishi Electric, the innovative thinking that we put into manufacturing satellites for space is the same thinking we put into the sustainability of our HVAC systems. From heating and cooling in the most extreme Canadian climates to the utmost flexibility in HVAC design, we’ve been raising the bar for close to 100 years. Because we believe that “amazing” should apply to everything you do.
The Mitsubishi Electric Advantage
• Quality And Reliability You Can Trust •Efficient Products Designed For The Canadian Climate •Complete Sustainable HVAC Solutions • Over 30 Years Of Successful Installation •Strong Canadian Customer Support Team
Learn more at
www.mitsubishielectric.ca/en/hvac/professionals
Continued from page “51”
cially used for a lot longer than synthetics. The most common is ammonia (R717; GWP of zero) followed by carbon dioxide (R744; GWP of one) and hydrocarbons, which features quite a few but the main one would be propane (R290; GWP of three).
“We’re seeing propane in tons of equipment. For example, in grocery stores or smaller bar fridges, there are a lot of them that are carbon dioxide or a hydrocarbon,” explains Trevor Matthews, founder of Refrigerationmentor.com. “You are also see-ing them in heat pumps. It’ s growing and I believe it’ s just going to continue to grow at a rapid pace. ” This is just one opportunity that natural refrigerants have in advancing the HVAC industry.
Read the warning label
Carbon dioxide was first patented as a refrigerant in 1850 and even predates ammonia by more than 20 years. It was largely used in marine applications for both refrigeration and air conditioning on ships. This diminished once refrigerants like R12 (CFC) and R22 (HCFC) came onto the scene and then later commercialized in the 1930s. “These refrigerants could operate at lower pressures and were easier to handle, apply, andinstall, ” explainsKozina.“Carbondioxide has regained popularity over the past 10 to 15 years due to its low GWP of one. ”
A concern associated with carbon dioxide is that it operates at a very high pressure. This means that if there was a leak, the system would lose its refrigerant gas in a matter of minutes and with it, all the cooling capacity. In theory, a customer could potentially lose the entire inventory at a supermarket in just one night, explains John Keating, vice president and general manager of stationary refrigerants at Honeywell. There ’ s more time with an HFO to fix the situation before getting to the stage of losing produce. Still, in the right situation, any refrigerant could pose a danger, says Matthews.
HFCs are to be phased down in Canada due to their high global warming potential levels.
Qualified-only
This takes us onto how important proper training can be for the refrigeration industry. Some refrigerants, like ammonia, are toxic and flammable; they can be corrosive to skin, eyes, and lungs. According to Kozina, “Only qualified and experienced technicians should be used to install, commission and service equipment using R717. Systems that use R717 must also be designed to mitigate the risks associated with it.”
It is best to err on the side of caution with flammable refrigerants, like propane and ammonia. An open flame or spark could potentially cause ignition if a leak leads to a flammable concentration.
Natural refrigerants do pose safety concerns; yet due to their low GWP levels,
Continued on page “55”
Continued from page “53”
they are still increasing in popularity. That isn’t to say that one-day natural refrigerants will completely replace synthetic refrigerants. “We are seeing natural refrigerants gain popularity, but because of the caveats mentioned previously, we believe synthetic refrigerants will also continue to play a key role in moving to lower GWP,” explains Kozina. “We have used synthetics for almost 100 years quite safely, and new synthetic refrigerants with lower GWP ratings continue to be developed.”
“When you compare HFOs to naturals, I think certainly both provide lower GWP options compared to the other choices like HFCs,” explains Keating. On Dec. 27, 2020, the U.S. enacted the American Innovation and Manufacturing (AIM) act, which directs the U.S. Environmental Protection Agency (EPA) to address HFCs by providing new authorities to phase down the production and consumption of listed HFCs, manage HFCs and their substitutes, and facilitate the transition to next-generation technologies.
In Canada, the Ozone-depleting Substances and Halocarbon Alternatives Regulations were amended to control HFCs through a phase-down of consumption, according to the Government of Canada.
Back in 1987, Canada signed the international treaty referred to as the Montreal Protocol on Substances that Deplete the Ozone. It was designed to protect the ozone layer and phase out the manufacturing and consumption of ozone-depleting substances. In 2016, the Kigali Amendment was adopted which included an HFC phasedown amendment.
All in this together
When it comes to replacing refrigerants within a system, HFOs have the benefit that they can be simply dropped on for some of the older HFCs. Whereas if the desire was to switch to a natural refrigerant, the entire system would need to be redesigned, reports Keating. “You couldn’t use existing equipment, you ’d have to put a whole new system in because natural refrigerants, particularly carbon dioxide, operate at very, very high pressures.” HFOs don’t pose these same risks.
At the end of the day, both natural and synthetic refrigerants will be important in filling the supply gap left open by the phasedown of high GWP refrigerants, explains Keating. “It is not possible to drop in a natural refrigerant into an existing synthetic refrigeration system, therefore an end-user who chooses to go “natural” would need to replace equipment in an existing system.
In Canada, the Refrigerant Management Canada (RMC) program was created to properly dispose of fluorinated refrigerant waste. The program establishes standards and guidelines for every part of the disposal process. :
WHERE CONNECTIONS HAPPEN.
The MEET (Mechanical Electrical Electronic Technology) Show returns to Moncton... This iconic biennial event draws exhibitors and visitors from throughout Canada and the US, showcasing the very latest products and services available to the mechanical and electrical industries in today’s market.
TO RESERVE YOUR SPACE AT THIS PREMIER EVENT, PLEASE CONTACT: Shawn Murphy, Show Manager smurphy@mpltd.ca • 1.888.454.7469
