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HEAT TRANSFER IN NANOCHANNELS, MICROCHANNELS, AND MINICHANNELS

Flow Boiling Characteristics for R1234ze(E) in 1.0 and 2.2 mm Circular Channels

[+] Author and Article Information
Cristiano Bigonha Tibiriçá, Gherhardt Ribatski, John Richard Thome

 Department of Mechanical Engineering, University of São Paulo, Av. Trabalhador São Carlense, 400, 13566-970, São Carlos, SP, Brazilbigonha@sc.usp.br Laboratory of Heat and Mass Transfer (LTCM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 9, Lausanne CH 1015, Switzerland e-mail:john.thome@epfl.chbigonha@sc.usp.br

J. Heat Transfer 134(2), 020906 (Dec 19, 2011) (8 pages) doi:10.1115/1.4004933 History: Received December 17, 2010; Revised July 21, 2011; Published December 19, 2011; Online December 19, 2011

Experimental flow boiling heat transfer results are presented for horizontal 1.0 and 2.2 mm I.D. (internal diameter) stainless steel tubes for tests with R1234ze(E), a new refrigerant developed as a substitute for R134a with a much lower global warming potential (GWP). The experiments were performed for these two tube diameters in order to investigate a possible transition between macro and microscale flow boiling behavior. The experimental campaign includes mass velocities ranging from 50 to 1500 kg/m2 s, heat fluxes from 10 to 300 kW/m2 , exit saturation temperatures of 25, 31 and 35 °C, vapor qualities from 0.05 to 0.99 and heated lengths of 180 mm and 361 mm. Flow pattern characterization was performed using high speed videos. Heat transfer coefficient, critical heat flux and flow pattern data were obtained. R1234ze(E) demonstrated similar thermal performance to R134a data when running at similar conditions.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Test facility diagram used for experiments (LTCM – EPFL)

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Figure 2

Test section details and thermocouple positions for 1.0 mm tube

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Figure 3

Test section details and thermocouple positions for 2.2 mm tube

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Figure 4

Single-phase energy balance for R1234ze(E) including pre-heater and test section in 1.0 and 2.2 mm tube

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Figure 5

Single phase heat transfer comparison for 1 and 2.2 mm tube

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Figure 6

Wall superheating for R1234ze(E) at G = 400 kg/m2 s, Tsat  = 31°C, Lheated  = 180 mm, ΔTsub  = 4 K, D = 1.0 mm

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Figure 7

Effect of the mass velocity on the heat transfer coefficient for the 1.0 mm tube, Tsat  = 31 °C for R1234ze(E)

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Figure 8

Comparison between heat transfer coefficient of R1234ze(E) and R134a for 1.0 mm tube at Tsat  = 31°C

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Figure 9

Comparison between heat transfer coefficient of R1234ze(E) and R134a for 2.2 mm tube at Tsat  = 31°C

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Figure 10

CHF for R1234ze(E) in 1.0 mm tube. Effect of mass velocity, saturation temperature and subcooling.

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Figure 11

CHF for R1234ze(E) in 2.2 mm tube. Effect of mass velocity, saturation temperature and subcooling.

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Figure 12

Comparison between CHF of R1234ze(E) and R134a [21] in 1.0 mm tube, Tsat  = 31°C, ΔTsub  = 4 K

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Figure 13

Comparison between CHF of R1234ze(E) and R134a in 2.2 mm tube, Tsat  = 31°C, ΔTsub  = 4 K

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Figure 14

Flow pattern map for R1234ze(E) in 1.0 mm channel, Tsat  = 31°C, transition lines from Ong and Thome [24]

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Figure 15

Flow pattern map for R134a in 1.0 mm channel, Tsat  = 31°C, transition lines from Ong and Thome [24]

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Figure 16

Flow pattern map for R1234ze(E) in 2.2 mm channel, Tsat  = 31 °C, transition lines from Ong and Thome [24]

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