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Our Refrigerant Focus series delves into the history, properties, suitable applications, and pros and cons of some of today’s popular or otherwise noteworthy refrigerants. This installment will focus on R-407A.
Check out some of our refrigerant focus posts below.
R-407A – often sold under tradenames like Freon® (Chemours), Genetron® (Honeywell), and others – is the first “replacement replacement” that we’ve covered in the Refrigerant Focus series. It was designed to replace R-404A (Pentafluoroethane, 1,1,1-Tetrafluoroethane, 1,1,1,2-Tetrafluoroethane), which was developed as a replacement for R-22 (Chlorodifluoromethane).
R-407A is a zeotropic hydrofluorocarbon refrigerant blend composed of 20% R-32 (difluoromethane), 40% R-125 (Pentafluoroethane), and 40% R-134a (1,1,1,2 – Tetrafluoroethane). More properties for R-407A can be found in the table below.
|
R-407A Properties |
|
|
Formula |
R-32 (20%) R-125 (40%) R-134a (40%) |
|
Molecular weight (g/mol) |
90.1 |
|
Boiling temperature °F (°C) |
-49 (-45) |
|
Critical temperature °F (°C) |
180 (82.3) |
|
Critical pressure, PSI, (Bar) |
655 (45.1) |
|
Gas heat capacity Btu/lb·°F, (kJ/(kg∙°C)) |
0.198 (0.829) |
|
Liquid heat capacity @ 1 atm, 30°C Btu/lb·°F (kJ/(kg∙°C)) |
0.363 (1.52) |
|
Temperature Glide °F (°C) |
8 (-4.4) |
|
Global Warming Potential |
2100 |
|
Ozone Depletion Potential |
0 |
|
ASHRAE Safety Group |
A1 |
To compare their performance, we’ve designed a theoretical coil and run it through Enterprise, our coil selection software.
We’ll use a 40” x 80” 4-row, 9FPI copper/aluminum evaporator coil designed for a refrigerated display case application. It features 0.375” OD copper tubes with a wall thickness of 0.15” and rifled walls. The fins are .0075” aluminum with a corrugated enhancement for added air turbulence.
The design conditions are shown below along with the performance rating for that coil using R-22, R-404A, and R-407A.
| Inputs | |||
|
Airside |
Tube-side |
||
|
Air flow |
4,000 SCFM |
Degrees superheat |
6°F |
|
Target capacity |
312,212 Btu./hr. |
Liquid temperature |
100°F |
|
Entering air temp. |
85°F/78°F (WB) |
Refrigerant suction temp. |
35°F |
|
Leaving air temp. |
55°F/45°F (WB) |
||
|
Air pressure |
14.696 PSIG |
||
|
Performance Comparison: R-404A vs. R-407A |
||||
|
R-404A |
R-407A |
Difference (%) |
Difference (abs.) |
|
|
Coil capacity |
408,937 Btu/hr. |
397,971 Btu/hr. |
-2.7% |
10,966 Btu/hr. |
|
Leaving air temp. |
46.1°F |
47.3°F |
2.6% |
1.2°F |
|
Refrigerant inlet temperature |
18.6°F |
24°F |
29% |
5.4°F |
|
Refrigerant pressure drop |
0.620 PSI/coil |
0.346 PSI/coil |
-44% |
0.274 PSI/coil |
|
Refrigerant mass flow |
9,384 lb./hr. |
6,426 lb./hr. |
-31% |
2,958 lb./hr. |
|
Circuit loading |
6,390 Btu/hr. |
6,281 Btu/hr. |
-1.7% |
109 Btu/hr. |
|
Performance Comparison: R-22 vs. R-407A |
||||
|
R-22 |
R-407A |
Difference (%) |
Difference (abs.) |
|
|
Coil capacity |
391,531 Btu/hr. |
397,971 Btu/hr. |
-1.6% |
6,440 Btu/hr. |
|
Leaving air temp. (WB) |
47.9°F |
47.3°F |
-1.25% |
0.6°F |
|
Refrigerant inlet temperature |
18.6°F |
24°F |
29% |
5.4°F |
|
Refrigerant pressure drop |
0.282 PSI/coil |
0.346 PSI/coil |
23% |
0.064 PSI/coil |
|
Refrigerant mass flow |
5,646 lb./hr. |
6,426 lb./hr. |
14% |
780 lb./hr. |
|
Circuit loading |
6,118 Btu/hr. |
6,281 Btu/hr. |
2.6% |
163 Btu/hr. |
*Note: the same circuiting was used for all three coils
R-407A is primarily used for medium to low temperature refrigeration applications.
The main benefits of R-407A are:
The chief benefit of R-407A is its low-GWP relative to those substances that it was developed to replace. In addition to being less environmentally harmful, R-407A’s performance is fairly similar to R-404 and R-22 as you can see in the performance table above.
If you’re switching from R-404A to R-407A, you’ll gain some efficiency. An R-407A coil will have a lower pressure drop through the coil and requires less refrigerant per hour to meet the theoretical requirement, making it a cheaper long-term option. Also, unlike R-404A, R407A isn’t currently a major target of regulators (virgin R-404A is no longer allowed to be used to service or refill systems in Europe as of January 1, 2020 and several U.S. states have adopted legislation that includes similar mandates.)
It should be noted that while R-407A’s GWP of roughly 2000 is a major improvement over R-404, it’s certainly not considered “low.” And it's unclear to what extent R-407A will be regulated in the future.
The main drawbacks of R-407A are:
As a multi-part zeotropic blend, R-407A’s glide isn’t so much a con as it is an added variable. This 8-degree boiling temperature “lag” must be accounted to properly size equipment like compressors.
Also, at temperatures below roughly -20°F, R-407A’s efficiency drops dramatically. According to this theoretical cycle performance table from Chemours (a manufacturer of R-407A), an R-407A system would need 38% more compression power than an R-404A system to meet that requirement.
For comparison, a medium-temperature R-407A application (~20°F) would require a roughly 31% higher compression ratio than R-404A to meet the same requirement. While that’s not ideal, R-407A’s efficiencies in the other areas we’ve covered can offset that increase in power consumption.
If you're designing a system and can't decide which refrigerant is the best option, give us a call. We have multiple refrigerant experts on staff that can help you make the right choice to get the most out of your heat transfer equipment.
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