Low Charge NH3 Refrigeration Systems

1. Low Charge NH3
Refrigeration Systems
Stefan S. Jensen
B.Sc.Eng. FIEAust, CPEng, NER, RPEQ, F.AIRAH
ssjensen@scantec.com.au
Scantec Refrigeration Technologies Pty. Ltd.
HVACR Energy efficiency Seminar 2016

2. HVACR Energy efficiency Seminar 2016
Options Paper – Review of the
OPSGG Management Programme,
October 2015
“A reduction in hydrofluorocarbon (HFC) emissions
is an important part of Australia’s commitment.
Australia will fast track work to reduce domestic
HFC emissions by 85 per cent by 2036, in line with
the most ambitious phase-down proposals under
the Montreal Protocol.”
The Hon Greg Hunt MP
Minister for the Environment
The HFC situation

3. HVACR Energy efficiency Seminar 2016
Where to from here?
Low GWP refrigerants
Synthetic or natural refrigerants?
What are natural refrigerants?
Ammonia (NH3) or R717
Carbondioxide (CO2) or R744
Hydrocarbons (HC)
Air or R729
Water (H2O) or R718

4. HVACR Energy efficiency Seminar 2016
Natural or synthetic?
- Are the two refrigerant families distinguishable by
flammability?
- Are the two refrigerant families distinguishable by toxicity?
NO – low GWP refrigerants are all flammable excepting
water, CO2 and air (R718, R744, R729)
NO – many low GWP refrigerants are toxic and/or have toxic
combustion products excepting water, CO2 and air (R718,
R744, R729)

5. HVACR Energy efficiency Seminar 2016
Business case
If you have one of these:
Industry standard, single stage HFC
based, air cooled refrigeration plant
and can continue to pay this
every month for this:

6. HVACR Energy efficiency Seminar 2016
you can own one of these:
State of the art low charge NH3
refrigeration system
IN FIVE YEARS PAID
FOR WITH ENERGY
COST SAVINGS
Business case
and pay this per month after that:
for this

7. HVACR Energy efficiency Seminar 2016
- Estimated SEC reduction from 143 to 38 kWh/m3*a
- Annual cost savings A$400,000 (energy & maintenance)
- Retrofit from multiple air cooled HFC units to central low
charge NH3 plant with glycol loop for medium temperature
- Investment ~A$1,900,000 (refrigerated volume ~21,000 m3)
- Current monthly electricity account A$43,000-A$48,000
Simple pay-back k$1900/k$400 < 5 years
Business case

8. HVACR Energy efficiency Seminar 2016
$42,000/month
$13,500/monthConversion cost $2,000,000
ROI = (42,000-13,500)*12/2,000,000*100=17%
Business case

9. HVACR Energy efficiency Seminar 2016
Source: California Energy Commission 2008
Tamworth
Perth
Energy Efficiency

10. HVACR Energy efficiency Seminar 2016
NH3 versus NH3
33.3 m
Low
charge
NH3

11. HVACR Energy efficiency Seminar 2016
Plant Annual energy
consumption
[MWh]
Recording
period
Refrigerated
volume
[m³]
Spec. energy
consumption (SEC)
[kWh/m³*a]
Low NH3 410 1.7.14-
30.6.15
9,474 43.2
Screw 1,135 1.7.14-
30.6.15
10,748 105.6
Notes:
- Both building layouts ~identical
- Energy consumption is for entire facility not only NH3 plant
NH3 versus NH3

12. HVACR Energy efficiency Seminar 2016
- Single stage compression
- Twin screw compressors in parallel with economizer
- No compressor speed control
- No floating condensing pressure
- Medium temperature serviced from low temp. segment
- Superheat controlled NH3 injection for medium temp.
- Poor material selection for medium temp. DX NH3 coolers
Floating condensing pressure reduced SEC by approximately 1/3.
- Refrigerant feed retrofit
What’s wrong?

13. HVACR Energy efficiency Seminar 2016
43 kWh/m3*a 106 kWh/m3*a$8,000/mth.
$22,000/mth.
NH3 low charge, dual stage,
reciprocating compressors with VFD’s
NH3 flooded, single stage
economized screw compressors
NH3 versus NH3

14. HVACR Energy efficiency Seminar 2016
What’s the message?
Use of natural refrigerants does not
guarantee superior energy performance
What does?
System design for energy efficiency or “Energy
Efficiency Engineering”

15. HVACR Energy efficiency Seminar 2016
Item Energy conservation factor Impact
[%]
1 Selection of compressor type 15-25
2 Evaporator fan speed control 15-25
3 Evaporator design 5-25
4 Compressor capacity control 10-20
5 Quality of match between compressor turn-down ratios and heat load
variations
0-15
6 Condenser size, condenser fan speed control and condenser efficiency 5-10
7 Liquid injection control into the evaporators 5-10
8 Elimination of liquid within suction lines 2-4
9 Use of low friction loss 304SS schedule 10 refrigerant pipe lines in lieu
of carbon steel
1-2
Factors influencing efficiency?

16. HVACR Energy efficiency Seminar 2016
What’s new here?
- Overall charge reduction from 3.5-4 kg/kW to 1.0-1.2 kg/kW; NH3 inventory in
air coolers 30-50 times less than LR; potential NH3 concentration in warehouse
<200 ppm
- Specific energy consumption values in kWh/m3*a are 0.45 to 0.60 times the
values recorded by CEC in 2008 (163 RDC’s)
- Quality based refrigerant injection control (0.95 < x < 0.99)
- High pressure liquid based oil separation combined with automatic oil return;
oil content < 1 ppm
- Hot gas defrost sequence with two hot gas supplies

17. HVACR Energy efficiency Seminar 2016
What’s new here?
- Internal surface enhancement promoting capillary action
- Conventional, Küba style and tank distributors
- Interconnecting 304SS pipe lines with reduced absolute roughness
- Infiltration and frost management
- Variable frequency drives on everything
- Injection control based on evaporator exit quality enabling
exceptionally low entering temperature differences
- Modern reciprocating compressors with low oil carry-over

18. HVACR Energy efficiency Seminar 2016
What is SH/X control?
Electronically controlled refrigerant injection
based on refrigerant quality at evaporator exit
Quality or
“x” sensor
The dielectric spectroscopy
(capacitance) measurement method
uses the difference in dielectric
properties of gases and liquid

19. HVACR Energy efficiency Seminar 2016
System charge 480 kg; LT/HT≈ 170/250 kW
Low charge: 1-1.2 kg/kW
Conventional liquid overfeed: 3-4 kg/kW
304SS
NH3 charge reduction

20. HVACR Energy efficiency Seminar 2016
- NH3 “inconveniences” gradually minimized/eliminated (oil drainage, moisture,
operators, specialist maintenance)
- Low charge NH3 costs about the same as NH3 liquid overfeed
- ~20% return for retrofits of HFC plants with new low charge NH3
(based on unit electrical energy cost $200-$300/MWh)
- ~30-50% return on Δ investment between new low charge NH3 and new
industry standard HFC (HFC=0.6*NH3)
- Lower than expected energy bills drive market acceptance
“ONCE YOU GO AMMONIA YOU NEVER GO BACK”
Discussion

21. HVACR Energy efficiency Seminar 2016
QUESTIONS?