Solubility, Miscibility, and Liquid Viscosity of Lubricants with CO 2 and Propane

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1 Solubility, Miscibility, and Liquid Viscosity of Lubricants with CO and Propane Chris Seeton Seeton C&P University of Illinois at Urbana-Champaign Chicago 03 ASHRAE Winter Meeting

2 Viscosity Temperature Chart ASTM D (1998) Kinematic Viscosity, cst

3 Viscosity Temperature Chart ASTM D (1998) 000 Viscosity Naphthene Mineral Oil Kinematic Viscosity, cst %

4 Viscosity Temperature Chart ASTM D (1998) 000 Viscosity and Vapor Pressure Naphthene Mineral Oil / Propane Kinematic Viscosity, cst % % % propane

5 Solubility Naphthenic Mineral Oil 3 / Propane 0 40 % % Pressure (bar) Pure Propane 1% Propane % % Temperature (C) 1

6 Viscosity Temperature Chart Daniel Chart Viscosity and Vapor Pressure Naphthene Mineral Oil / Propane Kinematic Viscosity, cst P = bar P = 4 bar P = bar P = 6 bar 0% P = 1 bar % % propane

7 Naphthenic Mineral Oil 3 / Propane Daniel Chart Viscosity and Vapor Pressure Naphthene Mineral Oil / Propane Assume: Evaporator = -6 C Suction Pressure = 4 bar 6 C Superheat C Suction Line HX C Rise in Compressor Kinematic Viscosity, cst P = bar P = 4 bar P = bar P = 6 bar P = 1 bar 0% % % propane Bearing Lubrication Temp. C Pure Lubricant Viscosity 6 cst Mixture Viscosity cst

8 POE- / R-134a Daniel Chart 000 Kinematic Viscosity, cst P = 1 bar P = bar P = 3 bar P = bar 0% POE- 90% 80% 70% Assume: Evaporator = -6 C Suction Pressure =.3 bar 6 C Superheat C Suction Line HX C Rise in Compressor Bearing Lubrication Temp. C Pure Lubricant Viscosity 8 cst Mixture Viscosity 48 cst

9 Viscosity Comparison ISO 3 Lubricants with Propane 0 Viscosity (cst) 40 0 AB MO POE PAG POE/R134a Test Condition: -6 C Evaporating, 6 C Superheat, C Suction Line HX, C Compressor Heating

10 Density Naphthenic Mineral Oil 3 / Propane Density of Naphthene Mineral Oil / Propane Density (g/cc) % Pure MO % % 1% % %Propane Temperature (C)

11 Density Polyalkylene Glycol 46 / Propane Density (g/cc) Density of Polyalkylene Glycol / Propane Temperature (C) 0% Pure PAG % % 1% % % Propane

12 Propane Miscibility POE, AB, and MO showed excellent solubility with propane PAG showed a saturated pressure close to pure propane for % compositions Could be a sign of possible immiscibility More testing is necessary

13 Solubility PAO > AB > PAG > POE 0 40 Pure CO Vapor Pressure 90% by weight Lubricant Concentration PAO- AB- PAG- POE- Pressure (bar) Modified Clausius-Clapeyron E log + T F T ( P) = D Temperature (C)

14 Mixture Viscosities 90% Lubricant PAG > PAO > POE > AB Pure Lubricants Absolute Viscosity, mpa*sec A B- PAG- PAO- POE- PA G PA O POE MO A B

15 POE- / CO Daniel Chart 000 Kinematic Viscosity, cst P = bar P = 1 bar P = bar P = 3 bar 0% POE- 9% 90% 8% Assume: Evaporator = 0 C Suction Pressure = 3 bar C Superheat C Internal Heat Exchanger C Rise in Compressor Bearing Lubrication Temp. 40 C Pure Lubricant Viscosity cst Mixture Viscosity. cst

16 Miscibility in CO 1 Immiscible PA O Miscible M temperature / o C PO E POE Miscible PA G A B W t % L u b rican t in C O

17 CO Miscibility Based on miscibility data design concerns should be based on the cycle operation for the AB, MO, PAO, and PAG lubricants It is expected that the POE lubricant will not experience these miscibility problems HOWEVER, serious design considerations must be weighed to account for the reduction in the mixture viscosity

18 Lubricants with CO - Conclusions POE Lubricant type showed good miscibility Severe viscosity reduction possibly limits its use to low temperature cascade systems PAG, PAO, MO and AB are only partially soluble in CO Transcritical AC systems Ø evaporators, receivers, Int. HX Transcritical Heat Pump systems Ø evaporators, receivers, compressor sump However, the PAG type lubricant seems to give the best lubricity for transcritical applications PAG maintained the highest mixture lubricity in this study High efficiency oil separators may make MO a viable lubricant in some cascade systems

19 Lubrication Influence of CO - Roller Bearing Prototype AC Compressor hrs Repeatable POE-

20 Polyol Ester 3 / Propane Daniel Chart Viscosity and Vapor Pressure Polyol Ester / Propane Assume: Evaporator = -6 C Suction Pressure = 4 bar 6 C Superheat C Suction Line HX C Rise in Compressor Kinematic Viscosity, cst P = bar P = 4 bar P = bar P = 6 bar 0% % % propane Bearing Lubrication Temp. C Pure Lubricant Viscosity 6 cst Mixture Viscosity 38 cst

21 Polyalkylene Glycol 46 / Propane Daniel Chart Kinematic Viscosity, cst P = bar P = 4 bar P = bar P = 6 bar Viscosity and Vapor Pressure Polyalkylene Glycol / Propane 0% % % propane Assume: Evaporator = -6 C Suction Pressure = 4 bar 6 C Superheat C Suction Line HX C Rise in Compressor Bearing Lubrication Temp. C Pure Lubricant Viscosity 83 cst Mixture Viscosity 1 cst

22 Alkylbenzene 3 / Propane Daniel Chart Viscosity and Vapor Pressure Alkylbenzene / Propane Assume: Evaporator = -6 C Suction Pressure = 4 bar 6 C Superheat C Suction Line HX C Rise in Compressor Kinematic Viscosity, cst P = bar P = 4 bar P = bar P = 6 bar 0% % % propane Bearing Lubrication Temp. C Pure Lubricant Viscosity cst Mixture Viscosity cst