A New Technology for Large Capacity ULT Chiller Using Neon Refrigerant and Turbo-Brayton Cycle

Ultra-low temperature (ULT) chillers are cooling systems that can achieve temperatures below -80°C, which are useful for applications such as semiconductor manufacturing, pharmaceutical and botanical extraction, and superconducting cable cooling. However, conventional ULT chillers have limitations in terms of cooling capacity, efficiency, and environmental impact. A new technology that uses neon as the refrigerant and Turbo-Brayton as the cooling cycle has been developed by researchers from the Korea Institute of Machinery and Materials (KIMM), which promises to overcome these challenges and offer a large capacity ULT chiller with superior performance and sustainability.

What is neon and why is it a good refrigerant?

Neon is a rare gaseous element that is present in the atmosphere at a very low concentration of about 0.0018%. It is a very inert element that does not react with other substances, and it is not toxic or harmful to the environment. Neon has a very low boiling point of -246°C, which makes it suitable for ULT applications. It also has a high specific heat capacity and a low viscosity, which means it can transfer heat efficiently and flow easily through the system. Compared to other cryogenic refrigerants, such as liquid helium and liquid hydrogen, neon has over 40 times more refrigerating capacity per unit volume and more than three times that of liquid hydrogen. This means that neon can provide more cooling power with less refrigerant and less space.

What is Turbo-Brayton and how does it work?

Turbo-Brayton is a cooling technology that uses a high-speed turbine and a compressor mounted on a single shaft and rotating at speeds of tens to hundreds of thousands of rpm. The basic principle of Turbo-Brayton is to compress the refrigerant gas, which increases its temperature and pressure, and then expand it through a turbine, which decreases its temperature and pressure. The expansion process cools down the refrigerant to the desired temperature, and the heat is removed by a heat exchanger. The refrigerant then flows back to the compressor to complete the cycle. The advantage of Turbo-Brayton is that it can control the temperature and capacity over a wide range, and it does not require any moving parts other than the shaft, which reduces the risk of leakage and maintenance.

What are the benefits of the new ULT chiller?

The new ULT chiller that uses neon as the refrigerant and Turbo-Brayton as the cooling cycle has been developed by the research team from the Department of Energy Storage Systems of KIMM. The team has designed and fabricated its own centrifugal compressor and turbo expander for the chiller, and has conducted performance tests to verify its feasibility and reliability. The results have shown that the new ULT chiller can achieve a cooling temperature of -100°C and a cooling capacity of 10kW, which are much higher than the existing ULT chillers. The new ULT chiller can also adjust the capacity within the range of 5.5 to 11kW, depending on the load and the ambient conditions. The new ULT chiller has several benefits over the conventional ULT chillers, such as:

  • Higher efficiency: The new ULT chiller has a coefficient of performance (COP) of 0.15, which is about 50% higher than the conventional ULT chillers that use cascade refrigeration cycles. This means that the new ULT chiller consumes less energy and reduces the operating cost.
  • Lower environmental impact: The new ULT chiller uses neon as the refrigerant, which is a natural and harmless gas that does not contribute to global warming or ozone depletion. The new ULT chiller also does not use any lubricants or oil, which eliminates the possibility of contamination and pollution.
  • Smaller size and weight: The new ULT chiller has a compact and lightweight design, thanks to the use of neon as the refrigerant and Turbo-Brayton as the cooling cycle. The new ULT chiller has a volume of 0.6 m3 and a weight of 300 kg, which are about 70% and 50% smaller than the conventional ULT chillers, respectively. This means that the new ULT chiller can be easily installed and transported.

The following table summarizes the comparison between the new ULT chiller and the conventional ULT chillers:

Parameter New ULT chiller Conventional ULT chiller
Refrigerant Neon Mixed refrigerants
Cooling cycle Turbo-Brayton Cascade refrigeration
Cooling temperature -100°C -80°C
Cooling capacity 10kW 2kW
Capacity control 5.5 to 11kW Fixed
COP 0.15 0.1
Volume 0.6 m3 2 m3
Weight 300 kg 600 kg
Environmental impact Low High

What are the future prospects of the new ULT chiller?

The new ULT chiller that uses neon as the refrigerant and Turbo-Brayton as the cooling cycle is a breakthrough technology that can provide large capacity ULT cooling with high efficiency and low environmental impact. The research team from KIMM plans to further develop the system so that it can be applied to various industrial fields, such as semiconductor manufacturing, pharmaceutical and botanical extraction, and superconducting cable cooling. The team also intends to replace neon with nitrogen as the refrigerant, which is more abundant and cheaper than neon, and to improve the performance and reliability of the system. The new ULT chiller is expected to contribute to the advancement of science and technology, as well as the enhancement of energy and environmental sustainability.

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