R744 air conditioning is faster to cool down a car, has a better efficiency than R134a, and is safe for passengers, extensive tests with a 100+ vehicle fleet by Behr and leading OEMs have shown.
In more than 1.2 million kilometres of on-the-road and bench testing under extreme conditions, CO
2 Mobile Air Conditioning has proved to be at least as reliable and efficient as current technology, with faster cool down, higher comfort levels, and better cooling capacity. Furthermore, it was proved that there is no safety risk for passengers.
These are main findings from tests performed by German air conditioning systems specialist Behr and leading carmakers earlier this year. In an extensive article published by the German specialized magazine ATZ, Behr explains how it conducted tests with a 100+ car fleet equipped with R744. Given the positive results, Behr is currently preparing for a mass production of CO
2 systems, after German carmakers officially announced in September 2007 to adopt CO
2 in next-generation vehicles.
As a conclusion, Behr states: “The successful fleet test and our product experience point to a smooth transition from R134a to R744. The new systems outperform today’s R134a systems in terms of environmental friendliness, cooling performance and energy efficiency. Regarding operational safety, acoustics, packaging, vehicle integration, and durability they are at least at the same levels as today’s systems. A smooth servicing of R744 refrigerant circuits is ensured.”
Detailed Results
Most relevant conclusions from Behr’s testing are:
- More Efficient: Tested under severe conditions simulated on test benches, through virtual thermal dummies, and in state-of-the art wind-climate tunnels, Behr found that the Coefficient of Performance of R744 systems is at least as high as that of R134a MAC. Under all conditions, CO2 outperformed R134a in terms of cool down dynamic and cooling capacity, which led to significant fuel savings.
- Safe for passengers: In terms of pressure and leakage safety the evaporator, located inside the vehicle cabin, is the most critical component within an R744 refrigerant circuit. Fully protected by a cross rail, a potentially harmful leakage of CO2 from the evaporator is only possible through corrosion. Starting with a small hole, around 1.5 cm3 of CO2 per minute will escape from the evaporator, up to 60 cm3 / minute if corrosion spreads. In the same time, a human exhales around 333 cm3 of CO2 - five times the amount of CO2 an evaporator leakage could produce. Depending on the damage, it could take 2-84 days to empty a complete CO2 MAC system. The findings thus effectively counter the argument that CO2 MAC could pose a potential health risk to passengers.
- Highly Reliable: Based on the leakage tests, the reliability of CO2 MAC was calculated. As a result, CO2 evaporators will work with a reliability of 99.4%, meaning they will operate without any problems to perform their task.
- Higher Comfort: CO2 systems cooled down the passenger compartment from 70°C to 25°C fourteen minutes earlier than R134a systems. On average, and taking all vehicle classes into account, R744 MAC reached comfort levels 8 minutes faster than current systems, making driving safer and more pleasant.
- Complete Servicing Infrastructure: Behr announced to offer a complete R744 servicing infrastructure before 2011, when high-global warming refrigerants will be banned in the EU. Behr’s product and services range, currently under preparation, will include the delivery of spare parts and servicing equipment as well as the training and certification of staff, technical support, the publishing of repair manuals and a fully automatic R744 servicing station.
Background
The tests, including equipment used and detailed results, were analysed in the German edition of ATZ (Automobiltechnische Zeitschrift) – the world’s oldest existing automotive magazine. ATZ is specialized on in-depth technical articles providing an insight into progress in automotive engineering. It is read by engineers worldwide.
