MOTOR Magazine

A MOTOR Magazine Newsletter
April 10, 2018

Contributed by Bob Chabot
MAHLE Shares A/C Trends and Opportunities

See the future and grow your mobile a/c service-readiness

MOTOR recently met with MAHLE Service Solutions experts Timothy Craig, Lindsey Leitzel and Eric Shultz. Together, they shared several new trends and technologies that are being implemented in mobile a/c systems. For a/c service professionals, these insights serve as a guide as they prepare for, and discover how to take advantage of the rapid pace of technological change.

The MAHLE experts also described many of the roles that new technologies being implemented in today's mobile a/c systems must fill. These included:

  • Various heat-scavenging and thermal storage strategies, such as heat pumps and powertrain chillers.
  • Battery heating and cooling technologies, as well as high voltage electronics cooling.
  • Pre-conditioning the cabin, battery and other systems to save energy and extend driving range.
  • Cutting edge technologies to emerge — such as sub-cooling of turbocharger air, new leak detection methodology and R-152a mobile a/c systems — each of which will be described more fully in sidebars below.

Pre-Cooling Turbocharger Air

Vehicles with smaller turbocharged engines have become the norm. In conjunction with conventional charge air coolers for these gasoline or diesel engines, many automakers are adding a refrigerant-to-coolant chiller. This subsystem uses compressor energy to sub-cool turbocharged air even further below the ambient air temperature. Sub-cooling provides a number of benefits. It significantly increases charge air density, low-end torque and fuel efficiency. In addition, thermal energy can be stored during braking to augment the compressor’s capacity to precondition the charge air coolant, with a minimal impact on cabin comfort. (All Images — MAHLE Service Solutions)

Different Powertrains Have Different Thermal Management Needs
“Vehicle refrigeration systems are changing to adapt to the demands of evolving powertrain types,” shared Leitzel, a MAHLE analysis and development engineer. “These include optimizing efficiencies for powertrains and other vehicle systems, improved cabin comfort, and thermal management of battery and power electronics.”

“So let increasing system and component complexity be your friend,” he continued. “Expect, prepare for and then leverage the opportunities presented by increasing complexity in vehicle refrigerant systems and associated hardware. For example, recognize that your customers’ service demands will increasingly be on new advanced controls and sensors, parts and components, more functions and clearly, more service needs.”

“Architectures for mobile air conditioning systems continue to evolve rapidly in response to the ongoing quest for improved efficiency and lower environmental impact,” Leitzel stated. “System layouts will continue to be in a state of flux, so expect variation in vehicle mobile refrigerant systems and subsystems to increase before any level of commonality shows up in the market. For instance, there is a lot of interest currently from automakers in supercharged batteries for electric vehicles, and other electrified components, which may well lead to larger compressors, battery chillers, multimode HVAC systems and other heating/cooling innovations. Opportunity is knocking for those who are astute and prepare for it.”

Using Forming Gas to Detect A/C Leaks

Mobile air conditioning (MAC) system leaks have commonly been detected using two traditional methods. One utilizes UV dye that, when mixed with compressor oil, is injected into the system either during the OEM factory filling or during A/C system servicing. A technician then visually pinpoints the leak using a U/V light.

The other method utilizes an electronic leak detector that relies on a sample of the refrigerant leak to highlight where the system pressure is escaping. Both methods rely upon the pressure of the refrigerant to present the leak to the atmosphere for detection. This is costly from a refrigerant, safety and environmental standpoint.

“Today, an all-new leak detection method, using forming gas, is now an option,” shared Eric Shultz, the engineering manager for MAHLE Service Solutions in the U.S. “It is already being extensively used in Europe to meet legislative mandates. In addition, one U.S. automaker has already approved this new method for use. Other automakers are considering the new approach, but have yet to state a position publicly.”

Instead of using standard automotive refrigerant, Shultz explained this method detects leaks by using a pressurized mixture of nitrogen and helium. After a technician removes any remaining A/C system refrigerant using a certified RRR unit, a forming gas of regulated pressure is charged into the vehicle A/C system. Leaks are found using a specialized detector designed to pinpoint any forming gas that is escaping.

“One advantage of this new method is the pressure for testing with forming gas is near the high side pressures (approximately 150 psig at ambient 70° F),” Shultz noted. “This enables detection of potential leaks at close to normal operating pressures. In addition, as long as the pressure does not exceed the standard maximum A/C system design pressure and liquid is not being used, there is no risk for compressor damage, whether it’s conventional or electric.”

“Service professionals need to understand forming gas is one method of pinpointing the physical location of a leak, ideal for its applications,” he advised. “For other situations, such as refrigerant leakage due to vibration, UV dye and an electronic leak detector would be better suited. It’s really a matter of matching the correct test to a specific scenario. Once pinpointed, solving the leak is the next step in the repair process.”

Shultz emphasized that MAHLE’s forming gas leak detection solution is new, and that it may be several years before the technology is available in the U.S. But service repair professionals should be looking for training to prepare for it should the U.S. Environmental Protection Agency (EPA) follows its European counterpart and make forming gas leak detection mandatory.

Regional Market Forces Influence Development and Implementation
A quick look at various markets around the globe reveals how regional market forces can influence the development and implementation of alternative a/c systems,” noted Craig, head of HVAC Systems Engineering for MAHLE North America. “As most in North America know, the current rage is R-1234yf, a more expensive but very environmentally-friendly new refrigerant. It is currently being widely introduced in new vehicle models and will dominate MAC systems here when the use of R-134a ends in May (?) 2020.”

Craig shared that R-1234yf is also the dominant refrigerant being used in new vehicles sold in Europe, although Daimler AG continues to develop and push for R-744 (a carbon dioxide based refrigerant) systems to be approved. Currently, the European Commission has referred Germany to the Court of Justice of the EU for a ruling, alleging Germany has infringed EU law by allowing the car manufacturer Daimler AG to place automobile vehicles on the EU market that were not in conformity with the EU’s MAC Directive, and for failing to take remedial action once notified of the infraction.

“Third World countries, however, present much different challenges than North American and European markets do,” Craig advised. “In India, for example, automobiles sell in the neighborhood of $3,000 each or less. Hence, the cost of expensive refrigerants and systems can be prohibitively unaffordable. As a result, alternative and more affordable MAC systems, such as those based on R-152a, are being considered.

Less Expensive R-152a Secondary Loop System Gains Traction

A year ago, at the 2017 Mobile Air Conditioning Society Worldwide (MACS) annual event, Craig informed attendees that MAHLE, Indian automaker Tata Motors Limited and other partners were jointly developing a prototype Secondary Loop Mobile Air Conditioning (SL-MAC) system that uses R-152a. Under the aegis of the United Nations Environment Initiative, the project aims to make affordable differences in the areas of climate comfort, public health, and food and energy security. Craig recently updated the peer design team earlier this year.

Two months ago at the 2018 MACS event, Steve Schaeber, the manager of technical training for MACS, reported on progress to date. “R-152a systems are much more affordable, as is the refrigerant, when compared to R-1234yf systems. Compared to R-134a, which has a global warming potential (GWP) value of 1,430, both R-1234yf (GWP = 4) and R-152a (GWP = 124) are more environmentally-friendly. However, R-152a is more flammable than R-1234yf, and requires Secondary Loop Mobile Air Conditioning (SL-MAC) technology to keep R-152a fumes out of vehicle passenger cabins.”

“In the SL-MAC schematic above (circled in yellow), the primary refrigerant, R-152a, is used to cool a safer secondary fluid/coolant — in this case glycol — which in turn cools the air actually directed into the cabin,” he added. “This occurs entirely underhood, so R-152a refrigerant never enters the passenger compartment. This process enables R-152a to be used safely to take advantage of its affordability, high cooling capacity and lower energy losses to achieve an optimized overall thermodynamic efficiency. In addition, the R152a SL-MAC system also has the potential to provide cabin air cooling for powertrains that incorporate start-stop technology. While no automaker has announced plans to use R152a systems for passenger car passenger cabins in the U.S., some have developed R152a based battery pack cooling systems for electrified vehicles (e.g. Chrysler Pacifica Minivan). Expect to hear more about R-152a in the coming months.”

Expect MAC Technology to Continue Evolving
“It’s important for service professionals to understand that with the growing variety of powertrains in today’s vehicle market, MAC systems have taken on new roles well beyond merely supporting vehicle operation,” explained Leitzel. “In addition to basic vapor compression cooling to provide passenger comfort, examples include the refrigeration system being called upon to temper the electrical energy storage system, pre-heat the vehicle interior and even car seats in extreme cold ambient conditions, and provide thermal management for new technologies.”

“Expect the growing complexity of mobile air conditioning and refrigeration systems management to impact the industry with more parts, more sensors, more functions and systems, and clearly, more service needs," added Craig. "In addition, heating and cooling communications are being networked through many vehicle systems, which is pushing a/c shops and technicians to using good quality scan and other diagnostic tools.”

"But remember, it’s also important to stay grounded in the basics — such as critical thinking, electrical theory and reading wiring diagrams — to fully understand and adapt to incoming change," Shultz counseled. "To leverage change, maintaining and growing your competencies is essential. That’s what positions you as the “go-to” shop for resolving customer mobile a/c problems.

[Editor's note: Visit MOTOR.com for the latest diagnostic and service insights.]

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