Investigation of New Low-GWP Refrigerants for Use in Two ...€¦ · Investigation of New Low-GWP...

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 SystemsParker Hannifin Corporation

Parker Precision Cooling Systems www.parker.com/pc 2

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

Background


Candidate Fluid Overview

Name R134a R1234ze R1234yf N-13a N-13b

Type Pure fluid Pure fluid Pure fluid Blend Blend

Composition (% Mass)

R134a: 42R1234ze: 40R1234yf: 18

R134a: 42R1234ze: 58

Enthalpy of Vaporization 182.28 170.50 149.29 168.71 173.51

GWP(100 Years) 1430 6 4 604 604

Parker Precision Cooling Systems www.parker.com/pc

Vapor Pressure vs. Temperature

4

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

150 200 250 300 350 400

Pressure (M

Pa)

Temperature (K)

R134a

R1234yf

R1234ze

N‐13a

N‐13b


Saturated Pressure vs. Enthalpy

5

100

1000

10000

150 200 250 300 350 400 450

Pressure (k

Pa)

Enthalpy (kJ/kg)

R134a

R1234yf

R1234ze

N‐13a

N‐13b


Parker 2-Phase Cooling System

Microchannel Heat Sink

Cooling UnitCondenserAccumulatorPump

Inverter Drive


Parker 2-Phase Cooling System

50 100 150 200 250 300500

1000

2000

5000

Enthalpy [kJ/kg]

Pres

sure

[kPa

] 70°C

50°C

30°C

0.2 0.4 0.6 0.8

12

3

System schematic P-h diagram with R134a


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

8


Experimental Setup

T – Thermocouple (9)P – Pressure sensor (6)


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


Test Matrix

Q (W) 500 550 600 650 700 750 800 850 900 950 1000

Heat load

X (%) 30 40 50 60 70 80

Refrigerant exit quality

Uncertainties for pressure, temperature and volume flow rate are ± 1 %, ± 1 °C and ± 3 %, respectively.

(g/s) 5.5 7 8.5

Refrigerant mass flow rate


Data Reduction

Refrigerant quality

Q

Heat transfer coefficient

, ∙ ∆

∆∆ 2 ∆ 1

∆ 2∆ 1


Refrigerant Flow Rate vs. Heat Load

70% exit quality

0

5

10

15

20

25

30

35

400 500 600 700 800 900 1000 1100

R134aR1234zeR1234yfN‐13aN‐13b

Volumeflo

w ra

te [LPH

]

Heat load (W)


Refrigerant Flow Rate vs. Exit Quality

500 W heat load

0

5

10

15

20

25

30

35

40

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9


Volumeflo

w ra

te [LPH

]

Exit quality


Refrigerant Flow Rate Comparison

0

5

10

15

20

25

30

35

40

0.3 0.4 0.5 0.6 0.7 0.8

% Increase in

volum

e flo

w ra

te over R

134a

Exit quality

R1234ze R1234yf N‐13a N‐13b % change in required volume flow rate of candidate fluids compared with R134a R1234yf required ~ 34%

more flow than R134a N-13b required ~ 8%

more flow than R134a


Pump Pressure Rise vs. Exit Quality

Mass flow rate = 0.007 kg/s

0

5

10

15

20

25

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9


Pump pressure rise

[kPa]

Exit quality


Heat Transfer Coefficient vs. Exit Quality

Average heat transfer coefficient at mass flow rate of 0.007 kg/s

19

20

21

22

23

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9


Average he

at transfer coe

fficien

t [kW

/m2 ‐K]

Exit quality


Average Heat Transfer Coefficient Comparison

% change in average heat transfer coefficients of candidate fluids compared with R134a

‐10

‐9

‐8

‐7

‐6

‐5

‐4

‐3

‐2

‐1

00.3 0.4 0.5 0.6 0.7 0.8

% change in heat transfer coe

fficien

s com

pared to R134a

Exit quality

R1234ze R1234yf N‐13a N‐13b


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

19


Conclusions

Important system design parameters and suitable refrigerant(s)

20

Criteria Importance Candidate

GWP Environment R1234yf and R1234ze

Volumetric Flow Rate Pump Sizing N-13b

Pressure Drop Pump Power Consumption R1234yf

Heat Transfer Coefficient

Heat Sink Thermal Resistance R1234yf


Acknowledgements

21

We thank Honeywell, Inc. for supplying the fluids for testing.

Questions

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