soft-optimized system test of r410a, dr-55, r32, and dr-5a ... · soft-optimized system test of...

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



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).



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)



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).



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%



Repeatability

Capacity at “A” was repeatable within ±1%..±2%

Efficiency was repeatable within ±1%..±2%



Results – Cooling Mode

“A” conditions (95F ambient)

Capacities closely matched by selection

of VFD speed.

ave of 5 5 4 1 runs





Alternatives gave higher efficiencies

by 4.5% to 6%.

ave of 5 5 4 1 runs





Latent capacities follow total capacities.





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.




Outdoor Temperature Sweep to High Ambient

o Sensitivity of capacity to Tamb is slightly lower for the alternatives than for R410A.





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.





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.




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



Results – Heating Mode

H1 – 47F/43F H3 – 17F/15F

Small reductions in heating mode capacity when match capacity at cooling “A” conditions.




H1 – 47F/43F H3 – 17F/15F

Equal or small increases in heating mode efficiency when match capacity at cooling “A” conditions.




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.


Not understood at this time – needs further study.



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).




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.



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.



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.



SUPPLEMENTARY MATERIAL

Soft-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.



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





Capacities matched by selection of VFD speed.

Latent capacities

follow total capacities.

Alternatives gave higher efficiencies by 4.5% to

6%.



ave of 5 5 4 1 runs




“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%.



ave of 2 4 2 1 runs




“C” conditions (82F ambient, dry coil)

Capacities matched

w/selected VFD speeds.

Alternatives gave higher efficiencies

by 2% to 6%.




“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?




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.




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.




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.



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.↓




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).




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.

soft-optimized system test of r410a, dr-55, r32, and dr-5a ... · soft-optimized system test of...

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