Development of World's First Water Vapor Chiller with Axial Compressor- A big step toward the commercial development of a chiller that uses water, the ultimate natural refrigerant -
January 19, 2011
Kobe Steel, Ltd.
The Tokyo Electric Power Co., Inc.
Chubu Electric Power Co.,Inc.
The Kansai Electric Power Co., Inc.
Kobe Steel, Ltd., The Tokyo Electric Power Co., Inc., Chubu Electric Power Co., Inc., and The Kansai Electric Power Co., Inc., have completed a prototype of the world's first water vapor chiller. The chiller incorporates an axial compressor that uses water as the refrigerant, and can be applied to various applications such as air conditioning and cooling processes at buildings and factories. The prototype was developed with the help of the Danish Energy Agency*1 and in cooperation with the Central Research Institute of Electric Power Industry, Danish Technological Institute*2 and Johnson Controls Denmark ApS*3. This has marked a big step toward the practical use of water vapor chillers.
Against a background of global warming, recently developed air conditioning chillers and refrigerators often use refrigerants such as HFC*4, which is more environmentally friendly than other fluorocarbons, and natural refrigerants like CO2, ammonium and isobutane. Unlike these systems, our new prototype employs water, natural refrigerant, whose ozone depletion potential is zero and which is non-toxic and non-flammable.
A type of water vapor chiller that utilizes a centrifugal compressor*5 already exists, but it is structurally so large that it is difficult to downsize. Incorporating a newly developed axial compressor*6, our prototype that utilizes the Direct Heat Exchanger*7 has a footprint approximately one-third (or one-half in the case of the prototype with the Indirect Heat Exchanger*8) that of a conventional water vapor chiller utilizing a centrifugal compressor*9. We expect to achieve cooling performance of around 5.4 in COP*10 with the Direct Heat Exchanger type (about 4.8 with the Indirect Heat Exchanger type), which is equal to the COP of chillers using fluorocarbon refrigerants, and will be subsequently confirmed by performance tests.
We will continue to improve the prototype and to perform reliability tests with a view to launching the product onto the market as soon as we can.
The main characteristics of the water vapor chiller utilizing an axial compressor are as follows:
1 Use of water, the ultimate natural refrigerant
Using water as a refrigerant solves the issues of ozone depletion, global warming, flammability, and toxicity. Water is also used as the bearing lubricant in the compressor.
2 Significant downsizing
With the development of the axial compressor, the current prototype has achieved significant downsizing and has a footprint approximately one-third (or one-half for the Indirect Heat Exchanger) that of a conventional water vapor chiller with a centrifugal compressor.
3 Comparable performance to fluorocarbon refrigerant chillers
The cooling performance target is around 5.4 (4.8 for the Indirect Heat Exchanger
type) in COP.
An inverter control system was adopted to enhance the part load condition.
4 Adaptable to various needs
The prototype is adaptable to various needs thanks to the development of the Indirect Heat Exchanger for applications combined with other chillers, and the Direct Heat Exchanger for standalone operations.
*1 Danish Energy Agency
Danish Government agency responsible for energy.
*2 Danish Technological Institute
A non-profit laboratory approved by the Danish government for the purposes of developing a wide range of commercial and industrial technologies for domestic and foreign businesses, and disseminating them.
*3 Johnson Controls Denmark ApS
A Danish manufacturer of chillers operating as a member of the Johnson Controls Inc., which is a corporate group that spans 150 countries. The company's world headquarter is in the U.S., and the company provides products and technologies to optimize the energy efficiency of buildings.
*4 HFC: Hydro-fluorocarbon
Environmentally friendly refrigerant with zero ozone depletion. Nowadays chillers manufactured in Japan usually use this type of refrigerant.
*5 Centrifugal compressor
A compressor that makes pressure by utilizing centrifugal force created by gas discharged to the perimeter of the blades. Also known as a turbo compressor.
*6 Axial compressor
A compressor takes in gas from one side of the axis and compresses it in the direction of the other side of the axis. It has a structure similar to that of jet engines. The axial compressor has a greater capacity than a centrifugal compressor with the same outside diameter, and is therefore more suitable for the situations that require the handling of a large amount of gas.
*7 Direct Heat Exchanger
A type of heat exchanger that mixes the refrigerant and water. In the water vapor chiller that uses water as refrigerant, the passage of refrigerant does not have to be separated between cold water and coolant.
*8 Indirect Heat Exchanger
A type of heat exchanger that has different passages for the refrigerant and water. As in heat exchangers used in conventional fluorocarbon refrigerant chillers, the passage of the refrigerant is physically separated from the cold water and coolant by the heat exchanger tube walls.
*9 Conventional water vapor chiller utilizing a centrifugal compressor
This refers to the chiller installed in the LEGO toy factory in Denmark. It has the same capacity as our prototype, and its dimension is 12.2 m length, 5.2 m width, and 10.9 m height.
*10 COP (coefficient of performance = cooling capacity/energy consumption)
A higher COP value indicates higher energy efficiency.
COP values are calculated under the water temperature conditions defined in the Japanese Industrial Standard JIS B 8621: 12°C at the cold water inlet and 7°C at the outlet; 32°C at the cooling water inlet and 37°C at the outlet. When a device has a COP of 5.4, it can generate 5.4 times greater thermal energy than energy input (power).