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.
-----------------------------------------------------------------------------
Appendix 1: Development Organization (PDF 7.12KB)
Appendix 2: Outline of water vapor chiller with axial compressor (PDF 88.9KB)
*1 Danish Energy Agency
Danish Government agency responsible for energy.
*2 Danish Technological Institute
A nonprofit 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 12.2m
length, 5.2m width, and 10.9m 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).
