Carrier Unveils Breakthrough in Container Refrigeration

Carrier Transicold has debuted the world's first container refrigeration system to use the natural refrigerant CO2, exactly one year after the company announced it had developed and begun testing the technology.

The new NaturaLINE design has been engineered to deliver efficiencies equal to Carrier Transicold's best-in-class PrimeLINE unit.

"The NaturaLINE design provides the global shipping industry with the most environmentally sound alternative for refrigerated transport," says David Appel, president, Carrier Transicold. "NaturaLINE stands apart as the only one to offer a natural refrigerant-based solution."

By using CO2 as a natural refrigerant, the NaturaLINE design improves upon the PrimeLINE unit's ability to reduce carbon dioxide emissions 28 percent compared to previous units. Carrier Transicold's PrimeLINE and now the NaturaLINE unit significantly reduce on-board power generation requirements, helping shipping lines save fuel used in generation of electricity. This, in turn, helps hold down operating costs and reduce emissions related to power generation.

"NaturaLINE demonstrates how technological innovation can reduce the impact on climate change, continuing Carrier's long-standing commitment to providing sustainable solutions," Mr. Appel says.

"Addressing the special thermodynamic properties of CO2 necessitated the development of an innovative refrigerant management system, including a new purpose-built, multi-stage compressor with variable-speed drive, a 'gas cooler' with a wrap-around design and a flash tank," says Mike Griffin, new product development program manager, Carrier Transicold. "The patented reciprocating multi-stage compressor maximizes capacity and minimizes power consumption."

NaturaLINE uses two stages of compression, which improves the overall efficiency of the unit. Its unique cylinder unloading capability allows the compressor to save energy in light-load conditions.

The variable-speed drive that controls the compressor is a first for a Carrier container refrigeration unit. The custom-designed drive electronically adjusts the compressor's speed to provide the precise amount of cooling capacity to meet demand, saving considerable energy compared to conventional units.

NaturaLINE technology replaces the condenser assembly found in conventional refrigeration units with a new heat exchanger called the gas cooler. The gas cooler coil wraps around the fan, maximizing heat-transfer surface area for greater efficiency in a design that is both compact and lightweight.

"The gas cooler makes the overall refrigeration system more versatile in responding to the thermodynamic properties of CO2, providing gas cooling after each compression stage for better efficiency," says Griffin.

The flash tank, a new component in a container refrigeration system, is designed to manage the flow and phase change of the refrigerant after leaving the gas cooler. For efficient cooling performance, the patented Carrier design enables final separation of CO2 from its gas phase to the liquid state before entering the evaporator.

While introducing many industry firsts, the NaturaLINE design remains consistent with other Carrier Transicold'units. The basic frame, the evaporator and evaporator fans, and the controller and control box are virtually identical to existing Carrier Transicold models. The easy-to-use control interface works the same as on other container refrigeration units. Also, serviceability will be similar to existing Carrier Transicold products, and will be supported by a new comprehensive training program.