2a sessione

1. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
Development of CO2-CO2 cascade
refrigeration system
9th,June/2017
Yukio YAMAGUCHI

2. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P-1/9Back Ground
1. Climate change by Global warming
2. Increasing of Global warming gas
3. Issue on recovering of Global warming gas
Source: UNEP A Critical Link in Protecting
Climate and the Ozone Layer HFC (2011)
Fig.1 F-Gas emission

3. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P-2/9Back Ground
 Refrigerating show case that is installed to supermarket and other small food store
such as Convenience Store (CVS) are equipped direct expansion refrigeration system
with high GWP refrigerant such as R404A and R410A.
 Leakage rate and market stock of such high GWP refrigerant are cause of global
warming as direct impact. Thus, natural refrigerants are considering as alternative
refrigerant.
 Carbon dioxide is most likely alternative refrigerant in the sector because of non-
toxicity and non-flammability.
 Efficiency of refrigeration system contributes to global warming as indirect impact.
 In the previous development, cascade cycle system of HFC-CO2 refrigerants are
commonly used.
 Several refrigeration systems which are equipped with CO2 refrigerant, has been
developed and installed to supermarket and CVS.
 The relatively high C.O.P system should be constructed by the optimizations of
binary cycle using CO2-CO2 refrigerant.

4. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P-3/9System over view
Fig.2 Typical layout of Japanese CVS
Fig.3 Practical connection with Refrigeration
showcase and condensing unit

5. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P-4/9System configuration
Gas cooler
Evaporator
7
1
2
3
5
SLHEX
CompressorLT
Expansion
Valve
6
Gas cooler
Evaporator
12
8
9
10
CompressorHT
Expansion Valve
11
Pre-
cooler
4
SLHEX
Fig.4 Binary Cycle with CO2 -CO2
refrigerant
Fig.5 p-h Diagram of Binary Cycle with CO2- CO2
Refrigeration system
Enthalpy [kJ/kg]Pressure[Mpa]
1
2
34
5
6
7
8
910
11 12
PdHT
PdLT
PSHT

6. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P5/9Optimization of SLHEX
Fig.6 Annual COP vs Heat transfer ratio of
SLHEX @ Milan condition
Fig.7 Annual COP vs Heat transfer ratio of
SLHEX @ New Delhi condition

7. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P6/9System Optimization
Fig. 8 COP vs Discharge pressure of LT cycle Fig.9 COP vs Discharge pressure of HT cycle

8. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P-7/9Result of Optimization
Fig.10 System C.O.P vs ambient temperature of each refrigeration system

9. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
P-8/9Result of OptimizationCoefficientofperformance[-]Ambient
temperature[oC]
Coefficientofperformance[-]
Ambient
temperature[oC]Fig. 11 Monthly COP of CO2-CO2 cascade
system and HFC system @ Milan
Fig. 12 Monthly COP of CO2-CO2 cascade
system and HFC system @ New Delhi

10. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
EndConclusion
• Configuration of SLHEX should be considered form annual COP
point of view.
• Pressure setting on low side refrigeration cycle makes better
COP
• Binary (cascade) system makes effort to C.O.P in all ambient
temperature (10-40℃) that is compared with HFC404A Single
cycle
• CO2-CO2 cascade system can be one of candidate of alternative
solution for small supermarket and CVS

11. Latest Technology in Refrigeration and Air Conditioning - XVII European Conference Milano, 9 - 10 June 2017
Thank you
Grazie