Investigation of New Low-GWP Refrigerants for Use in Two-Phase - PowerPoint PPT Presentation

Investigation of New Low-GWP Refrigerants for Use in Two-Phase Evaporative Cooling of Electronics Alexis Nicolette-Baker, Elizabeth Garr, Abhijit Sathe, and Steve O'Shaughnessey Precision Cooling Systems Parker Hannifin Corporation

Background  Global warming from refrigerants a major environmental concern  Kyoto Protocol  AHRI Low-GWP Alternative Refrigerants Evaluation Program identifies several candidates for replacement of R134a  Four fluids – R1234ze, R1234yf, N-13a and N-13b are among 12 candidates identified by AHRI for R134a replacement Parker Precision Cooling Systems www.parker.com/pc 2

Candidate Fluid Overview Name R134a R1234ze R1234yf N-13a N-13b Type Pure fluid Pure fluid Pure fluid Blend Blend R134a: 42 Composition R134a: 42 R1234ze: 40 (% Mass) R1234ze: 58 R1234yf: 18 Enthalpy of 182.28 170.50 149.29 168.71 173.51 Vaporization GWP 1430 6 4 604 604 (100 Years) Parker Precision Cooling Systems www.parker.com/pc 3

Vapor Pressure vs. Temperature 4.5 4 R134a R1234yf 3.5 R1234ze N ‐ 13a 3 N ‐ 13b Pressure (MPa) 2.5 2 1.5 1 0.5 0 150 200 250 300 350 400 Temperature (K) Parker Precision Cooling Systems www.parker.com/pc 4

Saturated Pressure vs. Enthalpy 10000 Pressure (kPa) 1000 R134a R1234yf R1234ze N ‐ 13a N ‐ 13b 100 150 200 250 300 350 400 450 Enthalpy (kJ/kg) Parker Precision Cooling Systems www.parker.com/pc 5

Parker 2-Phase Cooling System Microchannel Heat Sink Inverter Drive Cooling Unit Condenser Accumulator Pump Parker Precision Cooling Systems www.parker.com/pc 6

Parker 2-Phase Cooling System 5000 70°C Pressure [kPa] 2000 50°C 1 2 3 1000 30°C 0.2 0.4 0.6 0.8 500 50 100 150 200 250 300 Enthalpy [kJ/kg] P-h diagram with R134a System schematic Parker Precision Cooling Systems www.parker.com/pc 7

Testing Goals  Determine what system changes need made for alternative refrigerants » Refrigerant line sizes – Tubing – Hosing – Inter connects » Refrigerant flow rates – Pump – Condenser – Heat sink Parker Precision Cooling Systems www.parker.com/pc 8

Experimental Setup T – Thermocouple (9) P – Pressure sensor (6) Parker Precision Cooling Systems www.parker.com/pc 9

Test Procedure  Heat load to heat sink was controlled by adjusting input voltage to electric heaters  Refrigerant subcool of 2 °C was maintained by adjusting condenser fan speed  Refrigerant exit quality was calculated by energy balance on heat sink  Exit quality was varied by changing the liquid pump speed which in turn varied refrigerant volume flow rate Parker Precision Cooling Systems www.parker.com/pc 10

� Test Matrix Heat load Q 500 550 600 650 700 750 800 850 900 950 1000 (W) Refrigerant exit quality X 30 40 50 60 70 80 (%) Refrigerant mass flow rate � 5.5 7 8.5 (g/s)  Uncertainties for pressure, temperature and volume flow rate are ± 1 %, ± 1 °C and ± 3 %, respectively. Parker Precision Cooling Systems www.parker.com/pc 11

Data Reduction  Refrigerant quality � �� � � �� � � � � �� Q � ��� � � �� � � � � � ��  Heat transfer coefficient � � ���� � � ���� ,���� ∙ ∆� �� �� � ∆� 2 � ∆� 1 ∆� �� �∆� 2 1 � ∆� Parker Precision Cooling Systems www.parker.com/pc 12

Refrigerant Flow Rate vs. Heat Load 35 70% exit quality 30 25 Volume flow rate [LPH] 20 R134a 15 R1234ze R1234yf 10 N ‐ 13a N ‐ 13b 5 0 400 500 600 700 800 900 1000 1100 Heat load (W) Parker Precision Cooling Systems www.parker.com/pc 13

Refrigerant Flow Rate vs. Exit Quality 40 500 W heat load 35 R134a R1234ze 30 R1234yf N ‐ 13a Volume flow rate [LPH] N ‐ 13b 25 20 15 10 5 0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Exit quality Parker Precision Cooling Systems www.parker.com/pc 14

Refrigerant Flow Rate Comparison 40 % change in required R1234ze R1234yf N ‐ 13a N ‐ 13b volume flow rate of 35 candidate fluids % Increase in volume flow rate over R134a compared with R134a 30  R1234yf required ~ 34% 25 more flow than R134a  N-13b required ~ 8% 20 more flow than R134a 15 10 5 0 0.3 0.4 0.5 0.6 0.7 0.8 Exit quality Parker Precision Cooling Systems www.parker.com/pc 15

Pump Pressure Rise vs. Exit Quality 25 Mass flow rate = 0.007 kg/s 20 Pump pressure rise [kPa] 15 10 R134a R1234ze R1234yf N ‐ 13a 5 N ‐ 13b 0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Exit quality Parker Precision Cooling Systems www.parker.com/pc 16

Heat Transfer Coefficient vs. Exit Quality 23 Average heat transfer coefficient at mass flow Average heat transfer coefficient [kW/m 2 ‐ K] rate of 0.007 kg/s 22 21 R134a R1234ze 20 R1234yf N ‐ 13a N ‐ 13b 19 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Exit quality Parker Precision Cooling Systems www.parker.com/pc 17

Average Heat Transfer Coefficient Comparison Exit quality % change in average 0.3 0.4 0.5 0.6 0.7 0.8 0 heat transfer coefficients of candidate fluids % change in heat transfer coefficiens compared to R134a ‐ 1 compared with R134a ‐ 2 ‐ 3 ‐ 4 ‐ 5 ‐ 6 ‐ 7 ‐ 8 R1234ze R1234yf N ‐ 13a N ‐ 13b ‐ 9 ‐ 10 Parker Precision Cooling Systems www.parker.com/pc 18

Conclusions  R1234ze, R1234yf, N-13a, N-13b were experimentally tested for possible replacement of R134a in Parker’s two phase liquid cooling system  R134a performed the best in terms of volume flow rate, pressure drop and heat transfer coefficient  All candidate fluids exhibited significant drop in system performance  No clear alternative to replace R134a » Selection of alternate fluid depends on design criteria Parker Precision Cooling Systems www.parker.com/pc 19

Conclusions  Important system design parameters and suitable refrigerant(s) Criteria Importance Candidate R1234yf and GWP Environment R1234ze Volumetric Flow Rate Pump Sizing N-13b Pump Power Pressure Drop R1234yf Consumption Heat Transfer Heat Sink Thermal R1234yf Coefficient Resistance Parker Precision Cooling Systems www.parker.com/pc 20

Acknowledgements  We thank Honeywell, Inc. for supplying the fluids for testing. Questions Parker Precision Cooling Systems www.parker.com/pc 21