1) Semi-welded plate heat exchangers are increasingly being used in R717 (ammonia) / R744 (CO2) cascade systems due to their safety and efficiency. 2) Two case studies are presented of semi-welded plate heat exchangers in the Netherlands that have operated reliably for over 10 years in coffee and poultry processing plants. 3) The semi-welded design eliminates the risk of media intermixing and has very high fatigue resistance, making it the most reliable solution for R717/R744 cascade applications.

2. Semi welded plate heat exchanger as
R717/R744 cascade heat exchanger
Alfa Laval

3. Why we see an increasing number of R717 Ammonia /
R744 CO2 Cascade installations
1) Benefit the use of the very efficient natural refrigerant ammonia R717 :
- using a secondary fluid in the refrigeration system limiting the ammonia
charge to increase safety
2) Increasing efficiency in low temperature two stage cascade applications
- benefitting the relatively better thermal properties of CO2 at low temperature
side and of Ammonia at high temperature (ambient) side
3) Benefit the advantages of CO2 R744 compared to glycol or chloride brines
- requiring smaller pipe and pump dimensions to reduce cost
Two cases of installations currently in operation in Netherlands will be
presented.

4. The Cascade Heat Exchanger – one of the most
important components*
Is handling a challenging duty of high
importance and must deliver:
1) efficient close temperatures approach
2) high design pressure CO2 side
3) resistance against high fatigue forces
from cyclical patterns of temperature
and pressure.
4) low risk of intermixing R744 and R717.
>It is a well-known fact that ammonia and carbon dioxide
mixing results in an ammonium carbamate powder*
Ammonia
Condensor
CO2
Evaporator
R717/R744 Cascade Heat Exchanger
CO2
Receiver
CO2
Compressor
Ammonia
Compressor
*Source: Zahid Ayub, M. Sultan Khan, Amir Jokar, Tariq S. Khan & Niel Hayes (2013) Recent Developments in Plate Exchangers—
Ammonia/Carbon Dioxide Cascade Condensers, Heat Transfer Engineering, 34:5-6, 401-408,

5. Plate Heat exchanger –efficient alternatives
Factor Fully Welded
Plate HEX
Semi Welded
Plate HEX
Temperature approach 2-3 K Yes Yes
Design Pressure min 40 Bar Yes Yes
Fatigue resistance Depends Very high
Risk of intermixing Yes* Very low
Reliability factors
* Source: Zahid Ayub, M. Sultan Khan, Amir Jokar, Tariq S. Khan & Niel Hayes (2013) Recent Developments in Plate Exchangers—
Ammonia/Carbon Dioxide Cascade Condensers, Heat Transfer Engineering, 34:5-6, 401-408,

6. Semi welded plate heat exchanger - the most reliable
solution*
- The Gaskets absorbs metal plate or
frame movements, eliminating any risk
of fatigue failures.
… and in case of sealing failure, all the
gaskets and welds are facing the external
atmosphere
à Eliminating the risk of fatal media
intermixing
*Source: Alfa Laval,

7. Case- Coffee factory
service after 10 years operation
© Alfa Laval
Finding:
Plates and gaskets looking fresh and functional
Result:
Heat exchanger back to as-good-as-new state after
cleaning and re-gasketing
Next planned opening and gasket maintenance:
Extended to about 15 years thus in year 2033
Douwe Egberts Coffee factory, Netherlands.
Installer: ENGIE
• Installed 2x Alfa Laval M10-BWFT in 2007
• After 10 years of trouble-free operation first planned
maintenance in May 2018
Alfa Laval semi-welded heat exchanger duty
Side 1
Capacity 1200 kW
Media Ammonia NH3
Evap. temp. -12 ° C
Design pressure 20 bar
Side 2
Media Carbondioxide CO2
Temp in/cond. temp. 15 ° C / -8 ° C
Design pressure 40 bar
Case

8. Case- Poultry process plant
© Alfa Laval
Request:
A trouble free heat exchanger operations at high pressure
with no risk of intermixing
Chicken Poultry Processor, Netherlands.
Installer: Bort de graaf BV
• Ammonia with secondary / CO2 cascade system for max.
safety and efficiency
• Process line for freezing 110 ton of fresh chicken every day
down to -18 °C.
Alfa Laval semi-welded heat exchanger duty
Side 1
Capacity 870 kW
Media Ammonia NH3
Evap. temp. -12° C
Design pressure 17 bar
Side 2
Media Carbondioxide CO2
Temp in/cond. temp. 50 ° C / -8 ° C
Design pressure 52 bar
Case
Result:
The plant is running very well in accordance with
specification since installation in 2017.

9. Reliable R717/R744 Cascade Heat Exchangers –
Available as standard
Customers can increasingly benefit the
advantages of this kind of system for industrial
refrigeration with:
- No global warming refrigerants
- High efficiency
- High safety