Soft-optimization test of R-410A alternative refrigerant R-32 in a split condensing unit - Phase II

Transcription

1 Soft-optimization test of R-410A alternative refrigerant R-32 in a split condensing unit - Phase II Stephen Li Daikin / Goodman Manufacturing Jan

2 2 Test objectives See the impact of R-32 on air conditioning system; Extend to extreme conditions in cooling mode and observe the degradation of different refrigerants; Check impact of compressor lubrication oil on system performance;

3 Test combinations & steps Tests performed Test unit:ssx ARPT36D14; Rating w/ original compressor ZP29K5E-PFV: 34,000 btu/hr, EERA 12, SEER 14.5; ANSI/AHRI 210/240 cooling conditions A/ B/ C/ D & (115 o F/ 84, 66 o F)/ (125 o F/ 84, 66 o F), required by AHRI; Tested with compressor ZP31K6E-PFV; Test 1 (baseline) - R410A, POE oil, 4T TXV, charge determination; Test 2 - R-32, POE oil, 3T TXV, charge determination; Test 3 R-32, prototype R-32 POE oil, 3T TXV, charge determination; Test / optimization steps ID TXV was adjusted based on superheat (SH) out of evaporator (E/O) = 3 o F; Charge was adjusted based on subcool (SC) at liquid service valve (LSV)= 8 o F; ID low speed w/ static pressure 0.23 H2O; 3

4 4 Lubrication oil comparison Copeland POE Copeland Prototype R32 oil Supplier Emkarate RL 32-3MAF Chemtura density g/cm3 at 20 degc viscosity Flash point Pour point -40 Water content ppm 40 slightly soluble Polyol ester % >99 Additives % <1 Color clear yellow clear Form liquid liquid Odor No data typical ester-like Stability Stable avoid heater, strong acids and strong bases, hazardous decomposition products: carbon oxides

5 5 Test setup & instrumentation T #5 T#7 T #14 P, T #17 OD coil ID coil P, T #1 TXV comp dryer P, T #13 Sight glass P, T #24 m P, T #11 Flow meter OD ROOM P, T #19 ID ROOM cooling

6 Pressure & temperature measurement locations 6 data locations in refrigeration system P T Comp discharge (#1) x1 x1 OD coil common in (#5) x1 OD coil out (#7) x1 OD SV (#11) x1 x1 Before ID TXV (#13) x1 x1 ID coil in (#14) x1 ID coil common TXV bulb (#17) x1 x1 OD SV (#19) x1 x1 Comp suction (#24) x1 x1 Total x6 x9

7 7 What happened during test Compressor was tripped when testing R-32 (test 2) at 125 o F OD ambient by compressor overload protector and maybe by HPS as well, therefore, no test of 125 o F in test 2; Another compressor of same model was used in test 3 with prototype R-32 POE oil, therefore, an unknown compressor-tocompressor variation was introduced; Difference of heat balance is larger than the improvement of EER of R-32, therefore, refrigerant side capacity and efficiency are calculated for comparison; test # compressor oil refrigerant TXV test conditions optimization 1 ZP31K6E-PFV #1 POE R410A 4T A/B/C/D/ (115, 84/66) / (125, 84/66) E/O SH = 3 F, LSV SC = 8 95 F 2 ZP31K6E-PFV #1 3 ZP31K6E-PFV #2 POE R32 3T A/B/C/D/ (115, 84/66) / (125, 84/66) prototype POE R32 3T A/B/C/D/ (115, 84/66) / (125, 84/66) E/O SH = 3 F, LSV SC = 8 95 F E/O SH = 3 F, LSV SC = 8 95 F

8 System capacity air side For each combination of ref. and oil, capacity decreases as OD ambient temp increases; R-32 has better capacity than R410A at rating conditions +4% w/ POE and 7% w/ the prototype R-32 oil; At high ambient conditions, R-32 shows even better capacity (up to +14%); R-32 has less HAT degradation than R410A; 8

9 9 System efficiency air side For each combination of ref. and oil, system eff. decreases as OD ambient temp increases; Due to heat balance, R-32 shows same EER A, EER B, and SEER, but better efficiency (+0.5) w/ prototype R-32 oil;

10 10 System capacity refrigerant side For each combination of ref. and oil, capacity decreases as OD ambient temp increases; By eliminating the impact of heat balance, R-32 has better capacity than R410A at rating conditions +6% w/ POE and ~ 8% w/ prototype R-32 oil; At high ambient, R-32 capacity is even higher (+13%); R-32 has lower high ambient temperature conditions (HAT) degradation than R410A;

11 System efficiency refrigerant side For each combination of ref. and oil, system eff. decreases as OD ambient temp increases; R-32 shows better EER A, EER B, and SEER (+0.1 ~ 0.5) by eliminating the impact of heat balance; At high ambient conditions, R-32 efficiency is even higher than R410A (+0.7); 11

12 Charge & cyclic degradation coefficient R410A + POE oil R32 + POE oil R32 + prototype oil M (oz) Cd Charge reduction is about 12-14% in this air conditioning unit; Cd of R-32 w/ prototype R-32 oil is within test accuracy; 12

13 13 Refrigerant flow rate R-32 flow rate is consistently ~30% lower than R410A;

14 Outdoor coil pressure drop p OD = discharge pressure LSV pressure Due to lower flow rate, R-32 has 2 ~ 4 psi lower pressure drop across the OD coil; 5mm HP may be possible with R-32 application; 14

15 Indoor coil pressure drop p ID = after expansion pressure suction pressure Due to lower flow rate, R-32 has 2 ~ 4 psi lower pressure drop across the ID coil; Smaller tube size may be possible for R-32 application; 15

16 Compressor discharge pressure R-32 discharge pressure is approximately 10 psi higher than R410A at rating conditions; At high ambient conditions, R-32 discharge pressure is 15 ~ 18 psi higher than R410A; 16

17 Compressor discharge temperature R-32 discharge temperature is approximately 20+ o F higher than R410A; At high ambient conditions, R-32 discharge temperature is over 30 o F higher than R410A which could be the reason that R-32 test trips at 125 o F; Further optimization of oil, compressor, & system may be needed to reduce discharge temperature; 17

18 Compressor isentropic efficiency ɳ s = (h out,s - h in ) / (h out - h in ) R-32 shows higher compressor isentropic efficiency that R410A; 18

19 Compressor volumetric efficiency ɳ v = m ref / (ρ V RPM) Overall, R-32 shows lower compressor volumetric efficiency w/ POE oil than R410A at rating condition, but better w/ prototype R-32 oil; At HAT, R-32 has better compressor volumetric efficiency than R410A; 19

20 20 Conclusions R-32 works in existing R410A system, including extreme conditions; Due to R-32 high discharge temperature, there is risk of compressor tripping at 125 o F ambient, the compressor needs to be modified to adapt to high ambient operation; Heat balance has big impact on the comparison of air side capacity and efficiency, therefore refrigerant side capacity and efficiency need to be considered; R-32 has higher capacity by 4 ~ 8% and efficiency by +0.1 ~ 0.4 at rating conditions; R-32 shows higher capacity (up to +14%) and efficiency (up to +0.8) at HAT conditions. The HAT degradation of R-32 is less than R410A; R-32 has higher discharge pressure (+10 psi) and discharge temperature (+25 o F) than R410A at rating conditions; At HAT, R-32 discharge pressure and temperature is even higher, +20 psi and +50 o F, respectively; Cd of R-32 is within test accuracy; Charge of R-32 is 13% lower than R410A for this condensing unit; R-32 flow rate is 30% lower than R410A, therefore, pressure drop of OD and ID unit is 2 ~ 4 psi lower; R-32 shows higher compressor isentropic efficiency and lower volumetric efficiency w/ POE oil than R410A at rating conditions, but better in both w/ prototype R-32 oil; R-32 has better compressor isentropic efficiency and volumetric efficiency than R410A at HAT; Although there is compressor-to-compressor variation, the prototype R-32 oil from Copeland shows positive impact on system performance with R-32 refrigerant;