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Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A in a 4-RT Unitary Rooftop Heat Pump
Ken SchultzPrinciple Research Engineer
La Crosse, WI
2Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Equipment Used
Precedent Rooftop Heat Pump
o48,500 Btu/hr @ 11.0 EERC
o44,000 Btu/hr @ 3.40 COPH
oAlliance scroll compressor‒ Emkarate RL32H POE oil
‒ TR200 P5K5 VFD installed
‒ Power measurements made upstream of VFD.
‒ η ~ 0.97 (varies little over range of speeds and loads encountered)
oFixed TXVs replaced w/adjustable TXVs of the same size
Replaced outdoor coil before testing began.
See supplementary slides at end of deck for more details.
oTested in Controlled Ambient Chambers
oWell instrumented
‒ Air-side & Refrigerant-side
3Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Refrigerants Selected
name R32 R125 R1234yf
R410A 50% 50%
DR-55 67% 7% 26%
R32 100%
DR-5A 68.9% 31.1%
name GWP(AR4)
GWP(AR5)
R410A 2088 1924
DR-55 698 675
R32 675 677
DR-5A 466 466Refrigerant properties used are consistent with NIST REFPROP v9.1 with mixture interaction parameters supplied by DuPont (now Chemours).
4Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Tests Conducted
Followed AHRI Standard 210/240 (2012) …
Additional tests in cooling mode
ooutdoor temperature sweep‒ 65F .. 125F in 10Fd inc’s
‒ 80F/67F ent indoor coil
‒ included in Report #56
ovary indoor conditions‒ 80/67, 75/63, 70/58.5
(DB/WB in F) (~50%RH)
‒ 82F outdoor (B condition)
‒ new data taken after Report #56 was submitted
o check for fractionation and leak/recharge behavior (new)
5Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Test Procedure
Baseline tests w/R410A
oRefrigerant charge sweep at “A” conditions w/VFD @ 60 Hz‒ Maximum EER was near catalog charge of 9.0 lbm.
‒ Superheat at compressor suction was determined to be ~13Fd.
‒ Subcooling leaving condenser was determined to be ~15Fd.
Tests with alternative refrigerants
oRefrigerant charge sweep at “A” conditions w/VFD @ 60 Hz‒ Adjusted TXV to match R410A suction superheat.
‒ Selected refrigerant charge that maximized EER (and coincidentally
closely matched R410A subcooling).
oAdjusted VFD/compressor speed to match R410A capacity at “A” conditions.
Used the selected charge, TXV setting, and VFD frequency for all other test points (both cooling and heating).
6Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results
Settings
Refrig# of runs
Charge (lbm)
TXV(turns)
VFD (Hz)
CAPwrt
R410AEER
wrt R410A
R410A 5 9.0 0 60 50,241 – 11.32 –DR-55 5 8.2 1 CW 60 50,213 0.1% 11.81 4.3%R32 4 7.25 3 CW 55 50,637 0.9% 11.98 5.8%DR-5A 1 8.2 3 CW 61 50,627 0.8% 11.84 4.6%CW is clockwise (in/closed), CAP is Capacity in BTU/hr, EER is in BTU/W·hr
Refrigerant charge, TXV position, and compressor speed selected for each refrigerant, along with the average capacity and EER obtained at the “A” point for each.
−9%
−19% −8%
+1.7%−9%
7Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Repeatability
Capacity at “A” was repeatable within ±1%..±2%
Efficiency was repeatable within ±1%..±2%
8Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“A” conditions (95F ambient)
Capacities closely matched by selection
of VFD speed.
ave of 5 5 4 1 runs
9Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“A” conditions (95F ambient)
Alternatives gave higher efficiencies
by 4.5% to 6%.
ave of 5 5 4 1 runs
10Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“A” conditions (95F ambient)
Latent capacities follow total capacities.
11Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“A” conditions (95F ambient)
Compressor Discharge Temperature (CDT)
• DR-55 and DR-5A have modest ↑.
• R32 has larger ↑.
ave of 5 5 4 1 runs
See supplementary slides at end of deck for results at the B, C, and D conditions.
12Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
Outdoor Temperature Sweep to High Ambient
o Sensitivity of capacity to Tamb is slightly lower for the alternatives than for R410A.
13Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
Outdoor Temperature Sweep to High Ambient
oCompressor power is more sensitive to Tamb for R32 than for others. Compressor power is 4% to 5% lower than R410A for DR-55 and DR-5A over Tamb range.
14Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
Outdoor Temperature Sweep to High Ambient
o Sensitivity of efficiency to Tamb is slightly lower for the alternatives than for R410A. R32 EER tailing off at high Tambbecause of increasing power draw.
15Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
Outdoor Temperature Sweep to High Ambient (2)
oCompressor discharge temperatures
oR32 reached max CDT at Tamb ~ 120F
DR-55 & DR-5A:+6..+12Fd over R410A
R32:+20..+45Fd over R410A
16Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Heating Mode
H1 – 47F/43F H3 – 17F/15F
Small reductions in heating mode capacity when match capacity at cooling “A” conditions.
17Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Heating Mode
H1 – 47F/43F H3 – 17F/15F
Equal or small increases in heating mode efficiency when match capacity at cooling “A” conditions.
18Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Heating Mode
H2 – 35F/33F Cyclic Defrost Test
o More variability between repeat runs –±10%.
o Significant differences between refrigerants.
‒ R32 performed exceptionally well – very short defrost periods.
‒ Based on other results, expect similar behavior for this condition as well.
o Outdoor coil temperature measurement (entrance to bottom circuit) not consistent between refrigerants.
See supplementary slides at end of deck for more details.
Not understood at this time – needs further study.
19Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Leak/Recharge w/DR-55
oPulled refrig samples from subcooled liquid line while running.
o “Leaked” vapor from compressor discharge line while running.‒ ~2 lbm of refrigerant “leaked” each time. (8.2 lbm full charge)
‒ Subcooling ~ 14Fd..16Fd with “full” charge, ~ 2Fd..4Fd after each “leak”.
oCompositions measured after each “leak/recharge” cycle.
oCapacity drops 3% to 5% after “leaking” 2 lbm. Capacity returns to within 1% of starting point after recharge.
oEfficiency drops 0.5% to 2% after “leaking” 2 lbm. Efficiency returns to within 0.5% of starting point after recharge.
oCirculating composition matched composition charged to unit within ±0.5% ⇒ little fractionation while running.
‒ Circulating composition changed very little (<0.5%) over the course of four leak/recharge events (all while unit was running).
See supplementary slides at end of deck for more details.
20Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Conclusions
Soft-optimized tests conducted on 4-RT RTU Heat Pump with R410A, DR-55, R32, and DR-5A.‒ Adjusted TXVs to match compressor suction superheat obtained
w/R410A.
‒ Selected charge to maximize EER @ “A” (essentially matching subcooling w/R410A.)
oMatched capacities @ “A” to R410A baseline by adjusting compressor speed.‒ DR-55 and DR-5A required no/little adjustment to compressor
displacement.
‒ R32 required an 8% reduction in compressor displacement to match heat exchanger capacities.
21Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Conclusions (2)
All three alternatives performed similarly wrt capacities and efficiencies at the various rating points.
oCapacities were within −4% to +1% of R410A baseline (matching at “A”).
oEfficiencies ran −1% to +6% compared to R410A baseline (+4% to +6% at “A”).
oAll three alternatives were slightly less sensitive to variations in ambient temperature resulting in somewhat higher capacities and efficiencies at high ambient temperatures compared to R410A.
22Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Conclusions (3)
Difference in compressor discharge temperatures.
oDR-55 and DR-5A produced CDTs only ~10Fd higher than R410A.
oR32’s CDTs ran ~20Fd higher than R410A at normal rating conditions and up to 40Fd hotter at 120F ambient temperature, reaching the maximum operating temperature.
23Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
SUPPLEMENTARY MATERIAL
Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A in a 4-RT Unitary Rooftop Heat Pump
24Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Equipment Used
Precedent Rooftop Heat Pump – WSC048E3
o AHRI Check-Test Unit
o 48,500 Btu/hr @ 11.0 EERC
o 44,000 Btu/hr @ 3.40 COPH
o Alliance scroll compressor, SXA044B2BPA
‒ 2.56 in³/rev = 311 ft³/min @ 60 Hz input → 3500 RPM
‒ Emkarate RL32H POE oil
‒ TR200 P5K5 VFD installed
‒ Power measurements made upstream of VFD.
‒ η ~ 0.97 (varies little over range of speeds and loads encountered)
o Fixed TXVs replaced w/adjustable TXVs of the same size
o Outdoor Coil
‒ 5/16" tube, 3 rows, 16 FPI
‒ 10.96 ft² face area
o Indoor Coil
‒ 5/16" tube, 4 rows, 16 FPI
‒ 7.71 ft² face area
Replaced outdoor coil before testing began.
25Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Instrumentation
Refrigerant-side
o Pressures and temperatures (TCs) at entrance and exit of major components.
o Turbine flow meters upstream of TXVs.
o Temperatures at entrance and exit of individual circuits on indoor and outdoor coils.
Air-side
o Dry-bulb and wet-bulb temperature measurements (RTDs) via sampling system.
o Indoor air flow rate measured by flow nozzle
Cooling Mode Heating Mode
26Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“A” conditions (95F ambient)
Capacities matched by selection of VFD speed.
Latent capacities
follow total capacities.
Alternatives gave higher efficiencies by 4.5% to
6%.
• DR-55 and DR-5A have modest ↑.
• R32 has larger ↑.
ave of 5 5 4 1 runs
27Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“B” conditions (82F ambient, wet coil)
Capacities matched
w/selected VFD speeds.
Latent capacities
were down ~5%.
Alternatives gave higher efficiencies by 2.5% to
4%.
• DR-55 and DR-5A have modest ↑.
• R32 has larger ↑.
ave of 2 4 2 1 runs
28Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“C” conditions (82F ambient, dry coil)
Capacities matched
w/selected VFD speeds.
Alternatives gave higher efficiencies
by 2% to 6%.
29Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
“D” conditions (82F ambient, dry coil, cyclic)
R4
10
AD
R-5
5R
32
DR
-5A
o DR-5A’s advantage might come from initial 30 seconds (during damper manipulation)?
o Repeatability of transient behavior?
o Good repeatability to steady-state “C” conditions.
‒ DR-5A going to overshoot capacity?
o Why the apparently different time constants?
30Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Cooling Mode
Vary Air Temperature Entering Indoor Coil‒ Entering dry-bulb temperatures = 80F, 75F, 70F. – Tamb = 95F.
‒ Kept entering air relative humidity fixed at 50%rh.
Capacity and Efficiency:All refrigerants showed similar
sensitivity to return air condition.
Latent Capacity:R32 generated slightly lower latent capacities than R410A and DR-55.
31Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Heating Mode
H1 – 47F/43F H3 – 17F/15F
Small reductions in heating mode capacity when match capacity at “A” conditions.
Equal or small increases in heating mode efficiency when match capacity at “A” conditions.
Elevation in CDTs over R410A are similar to cooling mode. Well within operating boun-daries when in heating mode.
32Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Results – Heating Mode
H2 – 35F/33F Cyclic Defrost Test
o More variability encountered than for other conditions – up to ±10%.
o DR-55’s and R32’s higher capacity and COP are due to of shorter defrost intervals.
o Signal from outdoor coil temperature sensor to controller?
‒ Temperatures measured near sensor at mode change points are not consistent between refrigerants.
‒ OCT sensor signal to controller was not recorded.
‒ How does controller know which refrigerant is present??
o Would expect similar perfor-mance for all refrigerants if controller reacted consistently.
33Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Fractionation & Leak/Recharge w/DR-55
o Pulled refrigerant samples from subcooled liquid line while running.
o “Leaked” refrigerant vapor from compressor discharge line while running.
‒ ~2 lbm of refrigerant “leaked” (collected into cylinders) each time. (8.2 lbm full charge)
‒ Subcooling ~ 14Fd..16Fd with “full” charge, ~ 2Fd..4Fd after each “leak”.
o Capacity drops 3% to 5% after “leaking” 2 lbm. Capacity returns to within 1% of starting point after recharge.
o Efficiency drops 0.5% to 2% after “leaking” 2 lbm. Efficiency returns to within 0.5% of starting point after recharge.
Have now leaked ~8# of the ~14# charged to
the unit.↓
34Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Fractionation & Leak/Recharge w/DR-55
o Refrigerant samples were pulled from subcooled liquid line while running.
o “Leaks” occurred from compressor discharge line while running (collected into 1# cylinders).
Initial charge taken from “small” (15#)
cylinder.
Refills done from “large” (30#)
cylinder.
o Circulating composition closely matched composition charged to unit ⇒ little fractionation occurring within the unit while running.
o Circulating composition changed very little over the course of four leak/recharge events (all while unit was running).
“Leaks” collected here (added to
residual charge).
35Soft-Optimized System Test of R410A, DR-55, R32, and DR-5A
in a 4-RT Unitary Rooftop Heat Pump
Fractionation & Leak/Recharge w/DR-55
REFLEAK – Crude Simulation of Full Fractionation (eg, cylinder discharge/recharge)
DR-55 nominal
composition
R32 = 0.67
R125 = 0.07
R1234yf = 0.26
fractionationafter initial charge
fractionationafter 1st leak
fractionationafter 4th leak
DR-55 has ~2F condenser glide at “A” conditions.
6.5 pt drop in R32%.
6.5 pt incin R1234yf.
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