Compressor Explosion Accident at Pump-Down of Air Conditioners

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1 Compressor Explosion Accident at Pump-Down of Air Conditioners Tomohiro HIGASHI a, Sho TAMAI a, Shizuo SAITOH b, Chaobin DANG a and Eiji HIHARA a a Department of Human and Engineered Environmental Studies, The University of Tokyo b Department of Mechanical Engineering, The University of Tokyo th IEA Heat Pump Conference 7

2 Refrigerants for Air conditioner Kigali amendment to the Montreal Protocol was published (Oct. 6) Refrigerant GWP Refrigerant GWP HFC-4 HFC-45ca 69 HFC-4a 4 HFC-4-mee 64 HFC-4 5 HFC- 675 HFC-45fa HFC-5 5 HFC-65mfc 794 HFC-4a 447 HFC-7ea HFC-4 9 HFC-6cb 4 HFC-5 5 Kigali amendment (EIA: Environmental investigation agency) HFC-6ea 7 HFC-5a 4 新たな制限のかかった冷媒リスト HFC-6fa 98 HFC- 48 Refrigerants regulated in Kigali amendment GWP: Global Warming Potential Transition to low GWP refrigerants is required

Refrigerants for Air conditioner Transition of refrigerants in air conditioning applications CFC HCFC R (CFCl ) R (CHF Cl) HFC R4A (CH F + C HF 5 ) R4a (C H F 4 ) Non-flammable (A) GWP and burning

3 Refrigerants for Air conditioner Transition of refrigerants in air conditioning applications CFC HCFC R (CFCl ) R (CHF Cl) HFC R4A (CH F + C HF 5 ) R4a (C H F 4 ) Non-flammable (A) GWP and burning velocity ( Lower GWP Higher burning velocity Zero ODP New Lower GWP Refrigerant R (CH F ) R4yf (CH =CF-CF ) Mildly flammability (AL) Lower GWP Low flammability = High stability = High GWP Mildly flammability = Low stability = Low GWP Lower GWP, but mildly flammable Safety evaluation is required

ICR5Workshop http://www.jsrae.or.jp/committee/bi nensei/risk_jap.

4 Safety evaluations of Mildly flammable refrigerants Many studies have been conducted on the flammability of low GWP refrigerants Ref. ICR5Workshop nensei/risk_jap.html Diesel combustion of oil and refrigerant mixture during pump down of air conditioners 4

evaporator are packaged in single unit Object of this research l l http://www.iceageheatingairconditioning.

5 Air conditioners Separate air conditioner Packaged air conditioner l l l Indoor unit and outdoor unit are separated Refrigerant line connects them Need to collect refrigerants when moving the air conditioner l Condenser and evaporator are packaged in single unit Object of this research l l nditioners_installations.html packaged-air-conditioners-types-of-packaged-ac/ 5

6 Heat Pump and Pump Down Cooling operation Evaporator Indoor unit Flow of refrigerant Outdoor unit Condenser Compressor Pressure: around.5-.mpa Expansion valve Valve To close the outlet valve of the outdoor unit Compulsorily drive the air conditioner Refrigerant gets condensed in the outdoor unit 6 =Pump Down

7 Heat Pump and Pump Down Vacuumed Air may be drawn into the compressor Evaporator Indoor unit Flow of refrigerant Outdoor unit Condenser Compressor Valve Expansion valve Refrigerant condensed To close the outlet valve of the outdoor unit Compulsorily drive the air conditioner Refrigerant gets condensed in the outdoor unit 7 =Pump Down

8 Accident during Pump Down Explosion of outdoor unit happened during pump down. According to report of Tokyo metropolitan government, the accidents were caused by the air leakage into the refrigerant tube by operation error during pump down. (Diesel explosion) PURPOUSE. To investigate the conditions of self explosion of air, refrigerant and lubricating oil mixture in the compressor of an air conditioner.. To estimate the safety of the new refrigerants by comparing to conventional refrigerants Explosion accident (Tokyo metropolitan government) 8

9 Experimental Apparatus Refrigerant line Refrigerant cylinder Mass flow controller Scrubber FT-IR Air line Heater Gas cell Compressor (model engine) Lubricating oil line Air compressor Oil tank Dehumidifier Mass flow meter Mass flow controller Oil injection system T P Stroke sensor Heater Encoder Compressor (model engine) Motor Stroke volume: 5.4 cc Compression ratio:6. Four-stroke engine 9

10 Experimental Apparatus Refrigerant cylinder Mass flow controller Adiabatic Scrubber compression by model engine Analysis of exhaust gas by FT-IR FT-IR Heater Gas cell Compressor (model engine) Air compressor Dehumidifier Mass flow meter Mass flow controller Oil injection system T P Heater Motor Encoder Stroke sensor Oil tank Mix refrigerant, air and lubricating oil Stroke volume: 5.4 cc Compression ratio:6. Four-stroke engine

11 Experimental conditions Rotational speed of engine: 5 [rpm] Inlet gas temperature: 6 [ ] Refrigerants: R4yf (CH =CFCF ), R (CH F ) (Low GWP, Mildly flammable) R4A (Conventional, Non-flammable, Mixture of R and R5) R (CHF Cl) (Non-flammable, pure) Refrigerant concentration: - [vol. %] Lubricating oil:pag (Polyalkylene glycol) oil, POE (Polyol ester) oil R4yf R R4A R

12 Experimental conditions Stroke sensor Oil injection Intake valve to FT-IR Intake port Exhaust valve Engine Intake valve to FT-IR Oil injection was controlled by using encoder and stroke sensor Inlet gas Injector Oil injection 9 (at clank angle)

13 Lubricating oil properties Properties of lubricating oils: PAG oil POE oil CHO ratio, mass % 6.7:.5:6. 7.:.8:9. Flash point, 6 54 Ignition point, 5 48 Theoretical air fuel ratio, kg kg Oil flow rate: The standard flow rate was calculated so that the oil flow rate became the theoretical air fuel ratio at which air was %. Ratio, [-] PAG oil flow rate [l min - ] POE oil flow rate [l min - ] (standard flow rate) Investigated the effect of the oil and its amount for flammability of the mixture Injector

14 Experiment Engine Exhaust gas (to FT-IR) Refrigerant and Air Motor Encoder Oil injector 4

15 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Oil.6 Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio Angle[degree] No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 5 The pressure rose drastically

16 Analysis of Exhaust gas R4yf concentration % Oil flow ratio:. FT-IR HF (4-6cm - ) Oil flow ratio:.6 CO (-cm - ) COF (98-88cm - ) Gas cell of FT-IR C H F 4 (R4yf) + 5/ O + x H O (+x) CO + (+x) HF + (-x) COF HF are COF are main reactive products of the combustion of R4yf The refrigerant itself burned 6

17 Flammable Range and Oil Flow Ratio R 4yf / PAG R / PAG Oil raito / Refrigerant concentration / vol. % Oil raito / Refrigerant concentration / vol. % non-flammable flammable non-flammable flammable R 4A / PAG R / PAG Oil raito / Refrigerant concentration / vol. % Oil raito / Refrigerant concentration / vol. % non-flammable flammable non-flammable flammable 7

18 Flammable Range and Oil Flow Ratio Oil raito / - Oil raito / R 4yf / PAG Refrigerant concentration / vol. % non-flammable flammable R 4A / PAG Refrigerant concentration / vol. % Oil raito / Lower refrigerant concentration Larger oil flow ratio More likely to burn Oil raito / R / PAG Refrigerant concentration / vol. % non-flammable flammable R / PAG Refrigerant concentration / vol. % non-flammable flammable non-flammable flammable 8

19 Maximum Pressure and Oil Flow Ratio Maximum pressure against different R4yf concentrations and PAG oil flow ratios p max /-.5.5 Oil. Oil.7 Oil. Oil. Oil.6 pth Flammable range and the maximum pressure increased as oil flow ratio became larger.5 Air % Refrigerant concentration /vol. % Air penetration The maximum pressure : normalized p max [-] = p max [MPa] / p [MPa] Refrigerant % (Normal operation) Theoretical value (assuming adiabatic compression based on the specific heat ratio of mixture) κ " = ρ %&'xκ %&' + ρ *+% x κ *+% ρ %&' x + ρ *+% ( x) P = P γ 6 9

20 .5 Maximum Pressure and Oil Flow Ratio Maximum pressure against different R4yf concentrations and PAG oil flow ratios Oil. (without Oil. pth p max /-.5 Flammable range and the maximum pressure increased as oil flow ratio became larger.5 Air % Refrigerant concentration /vol. % Air penetration The maximum pressure : normalized p max [-] = p max [MPa] / p [MPa] Refrigerant % (Normal operation) Theoretical value (assuming adiabatic compression based on the specific heat ratio of mixture) κ " = ρ %&'xκ %&' + ρ *+% x κ *+% ρ %&' x + ρ *+% ( x) P = P γ 6

21 .5 Maximum Pressure and Oil Flow Ratio Maximum pressure against different R4yf concentrations and PAG oil flow ratios Oil.7 Oil. Oil.7 pth p max /-.5 Flammable range and the maximum pressure increased as oil flow ratio became larger.5 Air % Refrigerant concentration /vol. % Air penetration The maximum pressure : normalized p max [-] = p max [MPa] / p [MPa] Refrigerant % (Normal operation) Theoretical value (assuming adiabatic compression based on the specific heat ratio of mixture) κ " = ρ %&'xκ %&' + ρ *+% x κ *+% ρ %&' x + ρ *+% ( x) P = P γ 6

22 p max /-.5.5 Maximum Pressure and Oil Flow Ratio Maximum pressure against different R4yf concentrations and PAG oil flow ratios Oil. Oil. Oil.7 Oil. pth Flammable range and the maximum pressure increased as oil flow ratio became larger.5 Air % Refrigerant concentration /vol. % Air penetration The maximum pressure : normalized p max [-] = p max [MPa] / p [MPa] Refrigerant % (Normal operation) Theoretical value (assuming adiabatic compression based on the specific heat ratio of mixture) κ " = ρ %&'xκ %&' + ρ *+% x κ *+% ρ %&' x + ρ *+% ( x) P = P γ 6

23 p max /-.5.5 Maximum Pressure and Oil Flow Ratio Maximum pressure against different R4yf concentrations and PAG oil flow ratios Oil. Oil. Oil.7 Oil. Oil. pth Flammable range and the maximum pressure increased as oil flow ratio became larger.5 Air % Refrigerant concentration /vol. % Air penetration The maximum pressure : normalized p max [-] = p max [MPa] / p [MPa] Refrigerant % (Normal operation) Theoretical value (assuming adiabatic compression based on the specific heat ratio of mixture) κ " = ρ %&'xκ %&' + ρ *+% x κ *+% ρ %&' x + ρ *+% ( x) P = P γ 6

24 p max /-.5.5 Maximum Pressure and Oil Flow Ratio Maximum pressure against different R4yf concentrations and PAG oil flow ratios Oil.6 Oil. Oil.7 Oil. Oil. Oil.6 pth Flammable range and the maximum pressure increased as oil flow ratio became larger.5 Air % Refrigerant concentration /vol. % Air penetration The maximum pressure : normalized p max [-] = p max [MPa] / p [MPa] Refrigerant % (Normal operation) Theoretical value (assuming adiabatic compression based on the specific heat ratio of mixture) κ " = ρ %&'xκ %&' + ρ *+% x κ *+% ρ %&' x + ρ *+% ( x) P = P γ 6 4

25 Comparison between PAG oil and POE oil R4yf,PAG R4yf,POE *UFL: Upper Flammable Limit 4 4 Oil. Oil..5 Oil.7 Oil..5 Oil.7 Oil. Oil. Oil.6 Oil. Oil.6.5 p'th.5 p'th p max / - p max / Refrigerant concentration / vol. % UFL:5vol.% Results with PAG oil performed wider flammable range than that with POE oil Refrigerant concentration / vol. % UFL:5vol.% 5

26 Comparison between PAG oil and POE oil R,PAG R,POE *UFL: Upper Flammable Limit 4 4 Oil. Oil..5 Oil.7 Oil..5 Oil.7 Oil. Oil. Oil.6 Oil. Oil.6.5 p'th.5 p'th p max / - p max / Refrigerant concentration / vol. % UFL:4vol.% Results with PAG oil performed wider flammable range than that with POE oil Refrigerant concentration / vol. % UFL:vol.% 6

27 Comparison between PAG oil and POE oil R4A,PAG R4A,POE *UFL: Upper Flammable Limit 4 4 Oil. Oil..5 Oil.7 Oil..5 Oil.7 Oil. Oil. Oil.6 Oil. Oil.6.5 p'th.5 p'th p max / - p max / Refrigerant concentration / vol. % UFL:vol.% Results with PAG oil performed wider flammable range than that with POE oil Refrigerant concentration / vol. % UFL:.5vol.% 7

28 Comparison between PAG oil and POE oil R,PAG R,POE *UFL: Upper Flammable Limit 4 4 Oil. Oil..5 Oil.7 Oil..5 Oil.7 Oil. Oil. Oil.6 Oil. Oil.6.5 p'th.5 p'th p max / - p max / Refrigerant concentration / vol. % UFL:5vol.% Results with PAG oil performed wider flammable range than that with POE oil Refrigerant concentration / vol. % UFL:5vol.% 8

29 Conclusions Ø Phenomena of diesel combustion during a pump down operation were experimentally investigated. Ø An adiabatic compression operation was carried out to reproduce the pump down process. Ø The flammable range of the refrigerant expanded and maximum pressure increased as the oil flow ratio increased. This tendency was observed with all refrigerants, R4yf, R, R4A, and R with the PAG oil. Ø The flammable range may vary widely with the use of different lubricating oils, which suggests that the properties of both the refrigerant and oil are significant factors that can contribute to accidents during pump down operations. Accident probability can be decreased by adjusting the flammability of the lubricating oil. 9

30 Acknowledgements This study has been conducted a part of research project on the Technology Development of High-efficiency Nonfluorinated Air Conditioning Systems conducted by New Energy and Industrial Technology Development Organization (NEDO)

31 Thank you very much for your attention! Department of Human and Engineered Environmental Studies, Graduate school of frontier science, The University of Tokyo (Kashiwa campus)

33 Accident during Pump Down Explosion of outdoor unit happened during pump down. According to report of Tokyo metropolitan government, the accidents were caused by the air leakage into the refrigerant tube by operation error during pump down. (Diesel explosion) (Tokyo metropolitan government) How to operate pump down ( エアコン処分 com) Explosion accident (Tokyo metropolitan government)

34 Purpose Background Flammability of Refrigerants Low GWP Mild flammability Background Accident during Pump Down Accidents happen during pump down No research have been conducted about conditions of explosion PURPOUSE. To investigate the conditions of self explosion of air, refrigerant and lubricating oil mixture in the compressor of an air conditioner.. To estimate the safety of the new refrigerants by comparing to conventional refrigerants 4

35 Previous Research Compressor explosion accidents are caroused by air penetration into the compressor Lubrication oil self ignite, then refrigerant itself burns Low refrigerant concentration Combustion, Pressure rises, HF production High refrigerant concentration No combustion.6 Maximum pressure [-] Production of HF and COF Refrigerant itself burns Refrigerant concentration [vol. %] Air penetration with oil without oil R4yf P_th HF[vol%] HF concentration [vol. %] JSRAE mildly flammable refrigerant RA committee nensei/final_report_6_jp.pdf This research: Investigated the effects of the lubricating oil on combustion through experiments with different kinds of oils and oil flow rates 5

36 リスク評価の話 FTA 6

37 Refrigerants for Air conditioner Kigali amendment to the Montreal Protocol ODP: Ozone Depleting Potential GWP: Global Warming Potential HFC R4A (CH F + C HF 5 ) R4a (C H F 4 ) Low flammability = High stability = High GWP Mildly flammability = Low stability = Low GWP New Lower GWP Refrigerant R (CH F ) R4yf (CH =CF-CF ) Mildly flammability Lower GWP R GW 7

Refrigerants for Air conditioner Transition of refrigerants in air conditioning applications ODP: Ozone Depleting Potential GWP: Global Warming Potential Ammonia

flammability Lower GWP Low flammability = High stability = High GWP Mildly flammability = Low stability = Low GWP Ozone depletion material reduction schedule based

38 Refrigerants for Air conditioner Transition of refrigerants in air conditioning applications ODP: Ozone Depleting Potential GWP: Global Warming Potential Ammonia CFC HCFC R (CFCl ) R (CHF Cl) HFC R4A (CH F + C HF 5 ) R4a (C H F 4 ) Toxic, Flammability Lower ODP New Lower GWP Refrigerant R (CH F ) R4yf (CH =CF-CF ) Mildly flammability Lower GWP Low flammability = High stability = High GWP Mildly flammability = Low stability = Low GWP Ozone depletion material reduction schedule based on Montreal Protocol (Ministry of the Environment) R,R4yf are promising replacements as lower GWP refrigerants, but have mildly flammability Safety evaluation is required 8

39 Flammability of refrigerants Effect of humidity for flammable range Effect of humidity for flammable range Burning velocity 9

40 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % 6 5 Pressure[MPa] 4 Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 4 The pressure rose drastically

41 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % 6 5 Pressure[MPa] 4 Oil. Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 4 The pressure rose drastically

42 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % 6 5 Pressure[MPa] 4 Oil. Oil.7 Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 4 The pressure rose drastically

43 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % 6 5 Pressure[MPa] 4 Oil. Oil.7 Oil. Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 4 The pressure rose drastically

44 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % 6 5 Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 44 The pressure rose drastically

45 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Pressure[MPa] 4 Oil. Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio Angle[degree] No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 45 The pressure rose drastically

46 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Pressure[MPa] 4 Oil. Oil.7 Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio Angle[degree] No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 46 The pressure rose drastically

47 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Pressure[MPa] 4 Oil. Oil.7 Oil. Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio Angle[degree] No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 47 The pressure rose drastically

48 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Oil.6 Pressure[MPa] 4 Oil. Oil.7 Oil. Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio Angle[degree] No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 48 The pressure rose drastically

49 Pressure inside engine with different amounts of PAG oil Refrigerant concentration % (Only air and oil) 7 R4yf, Refrigerant concentration % Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Pressure[MPa] 4 Oil. Oil.7 Oil. Oil. Oil.6 Oil Angle[degree] No combustion was observed when oil flow ratio was lower than.7. Maximum pressure increased with increasing oil flow ratio Angle[degree] No combustion occurred when the oil flow ratio was lower than.. Combustion occurred when the oil flow ratio was larger than.. 49 The pressure rose drastically

50 Analysis of Exhaust gas R4yf concentration % Oil flow ratio:. R4yf (8~cm - ) Oil flow ratio:.7 FT-IR Oil flow ratio:. CO (~cm - ) Gas cell of FT-IR 5

51 Analysis of Exhaust gas Oil flow ratio:. HF (4~6cm - ) Oil flow ratio:.6 COF (98~88cm - ) Decrease of R4yf (8~cm - ) C H F 4 (R4yf) + 5/ O + x H O (+x) CO + (+x) HF + (-x) COF HF are COF are main reactive products of the combustion of R4yf The refrigerant itself burned 5

52 Comparison between PAG oil and POE oil Flammable range (PAG>POE) Refrigerant UFL with PAG oil / vol.% UFL with POE oil / vol.% R4yf 5 5 R 4 R4A.5 R 5 5 Flammability of lubricating oils PAG oil POE oil Flash point, 6 54 Ignition point, 5 48 The properties of both the refrigerant and the oil are important factors. Accident probability can be decreased by adjusting the flammability of the lubricating oil.

Performance Testing of a Semi-Hermetic Compressor with HFC-236ea and CFC-114 at Chiller Conditions

Purdue University Purdue e-pubs International Refrigeration and Air Conditioning Conference School of Mechanical Engineering 1994 Performance Testing of a Semi-Hermetic Compressor ith HFC-236ea and CFC-114