The key parameters of a CO2 booster refrigeration system serving a supermarket in Italy were monitored from January to June 2019. The system provided cooling capacities of 20 kW at low temperature and 90 kW at medium temperature evaporators as well as heat recovery for space heating, hot water, and air conditioning. During the winter period, the system operated in transcritical mode to satisfy space heating demands. Monitoring data showed the cooling loads remained constant and will be used to validate models to analyze the performance of different system configurations annually. Simulations predicted up to a 10% reduction in yearly compressor energy use with an optimized overfed evaporator design.

2. Monitoring of a CO2 commercial
refrigeration system serving a
supermarket in Southern Europe
Frascold SpA

3. AGENDA
• Frascold profile
• System Description
• Results of the monitoring period
• Simulation results
• Conclusions

4. MORE THAN
EMPLOYEES
200
PRESENT IN
86 countries
6 business
units
ITALY, USA, CHINA,
INDIA, RUSSIA and
AUSTRALIA
70.000
COMPRESSORS PER YEAR
Production
Capacity
Wide range
of
applications
Innovation
&
Technology
Global
Presence
Tailored
solutions
RefrigerationValue
brand
air
conditioning
Natural
Refrigerants

5. -10
0
10
20
30
40
0 730 1460 2190 2920 3650 4380 5110 5840 6570 7300 8030 8760
Externalambient
temperature
(°C)
Average Temperature = 14.8°C
Max. Temperature = 39°C
Min. Temperature = -6°C
Monitoring Period
Jan 2019 – Jun 2019
Location
Monticello Brianza, Milan
(ITALY)

6. System layout
Booster system with parallel compression
NOMINAL COOLING CAPACITIES
20 kW at low temperature (LT)
90 kW at medium temperature (MT)
HEAT RECOVERY
Sanitary hot water: 22 kW
delivered at 65°C
Space heating: 100 kW
delivered at 55°C
Air conditioning: 130 kW
delivered at 6°C

7. PRESSURE MEASUREMENTS
1) Low pressure
2) Medium pressure
3) High pressure after MT compressors
4) High pressure after the Gas-Cooler
5) Intermediate pressure at the flash
tank
TEMPERATURE MEASUREMENTS
Inlet/Outlet compressors
Inlet/Outlet heat exchangers
MASS FLOW RATE MEASUREMENTS
Water mass flow rate at the SHWHE
Water mass flow rate at the SHHE
Water mass flow rate at the ACHE
ELECTRICAL POWER CONSUMPTIONS
Measurements layout
p
T
V
pow

8. The average pressure at the MT
evaporators is 27.5 bar
(saturation temperature -9°C)
Monitored pressures
During the winter period, to
increase the amount of heat
available for heat recovery, the
pressure is increased at around
85 bar
The average pressure at the
intermediate pressure receiver is
35.8 bar. At external temperature
lower than 2.5°C, the intermediate
pressure is reduced to avoid the
presence of subcooled liquid
The average pressure at the LT
evaporators is 13 bar (saturation
temperature -33°C)

9. EVLT = Evaporator LT load
EVMT = Evaporator MT load
Beginning of
January
End of
June
Externaltemperature[°C]
Heatflowrate[kW]
Time [weeks]
Monitored Heat Loads

10. Beginning of
January
End of
June
Sanitary Hot Water Heat Exchanger = SHWHE
Space Heating Heat Exchanger = SHHE
Air Conditioning Heat Exchanger = ACHE
Monitored Heat Recovery

11. Beginning of
January
End of
June
CLT = Compressors LT power
CMT = Compressors MT power
CAUX = Compressors AUX power
Monitored Electrical Power

12. 𝐂𝐎𝐏 𝐑𝐄𝐅'𝐇𝐑'𝐀𝐂=
*+,'*-,' *./0'*0./ '*12
)4+,'4-,'(4167
Monitored COP

13. Software simulation results
Energyconsumptions[kWh]
-3.2% -5.5% -7.2% -10.8%
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
200000
220000
Booster system
(Constant interm.
Pressure)
and Heat Recovery
Booster and overfeed
MT evaporators (opt.
Interm. Pressure)
and Heat Recovery
Booster system with
Parallel compression
(Const. interm.
Pressure) and Heat
Recovery
Booster system with
Parallel compression
(Opt. interm.
Pressure) and Heat
Recovery
Booster system with
Parallel compression
and overfeed MT
evaporators
(Opt. interm.
Pressure) and Heat
Recovery
LT compressors MT compressors AUX compressors All compressors
Booster
system
Booster system
and
overfed MT
evaporators
Booster system
and
parallel
compression
(const. IP)
Booster system
and
parallel
compression
(opt. IP)
Booster system,
parallel compression
(opt. IP) and
overfed MT
Evaporators
Baseline
consumption
All the configurations match the same loads and use the same models of compressors

14. • The key parameters of a CO2 booster system with parallel compression located in Milan
(Italy) have been monitored from January 2019 to June 2019.
• In addition to the cooling loads at the MT and LT evaporators, the system can provide all the
thermal needs: space heating, sanitary hot water production, air-conditioning.
• During the winter period the system works most of the time in transcritical conditions to
satisfy the demand for space heating.
• The cooling capacity at the LT evaporators is constant during the monitored period (around
10 kW). The average cooling load at the MT evaporators during the winter period is equal to
35 kW.
• These data will be used for the model validation which will be a tool for the yearly
performance analysis of different system solutions. For example, some numerical results
predict that the yearly electrical energy compressor consumption could be 10% lower in the
case of the booster system with overfed evaporators (compared to the standard booster
system).
Conclusions