1. Solar Energy Lab
Description and validation of the Little correlation for boiling zeotropic mixtures in horizontal tubes from cryogenic to room temperature
Rodrigo Barrazaa,b, Gregory Nellisa, Sanford Kleina, Douglas Reindla
aDepartment of Mechanical Engineering, University of Wisconsin, USA
bDepartment of Mechanical Engineering, Universidad Tecnica Federico Santa Maria, Chile

2. Overview Motivation Little correlation Similar correlations
Model derivation
Little model final form
Validation
Applicability criteria
Acknowledgements

3. Features of the zeotropic gas mixtures studied
The hydrocarbon mixtures are formed by 3 and 4 components. The synthetic refrigerant mixtures have 4 and 5 components.
Generally, the phase change is experienced from 150 K to room temperature. We are focus in the boiling process.
x = 0.75
P = 0.2 MPa
x = 0.25
P = 1.2 MPa
Tglide over 80 K
x = 0.50
45% methane, 35% ethane, and 20% propane (molar base)

4. Multi-Refrigerant Joule-Thomson5
after-cooler
P = 200bar 1 T
P = 20bar T
recuperator HX
room temperature 1 5
room temperature 1
P = 1bar 5 2
throttle
valve 2 4 3
evaporator
JT:
low thermal efficiency
low cost
high reliability
Scalable to small loads
cold temperature 2
cold temperature 4 3 4 3 h h
MRJT applications: cryosurgical probes, cooling infrared sensors, cryopreservation, liquefaction, biomedical samples, and current leads
Understand the Thermodynamics of mixture, phase diagrams
Heat Exchanger - Crucial component and understand the thermal behavior of gas mixtures.
MRJT:
higher thermal efficiency
low cost AC compressor

5. Little correlation (2008)
Based on annular flow
Specific heat of the mixture
Apparent specific heat of the mixture
htcl and htcv single phase heat transfer coefficients are calculating using Dittus-Boelter
Chisholm void fraction model is recommended to determine the hydraulic diameter for the liquid and vapor fraction
Validated using Nellis et al. (2004) data.
It is not clear shown how the correlation is obtained and how it should be applied.

6. Similar correlations Silver (1947) and Bell and Ghaly (1972)
Granryd (1991)

7. Little derivation Mixing pot temperature
Liquid vapor temperature difference

8. Little derivation (continuation)

9. Dittus-Boelter for the liquid film
Little derivation (continuation)
(Annulus)
Dittus-Boelter for the liquid film

10. Little correlation final form
Dittus-Boelter for the liquid film
Dittus-Boelter for the vapor core
Chisholm void fraction model

11. Validation using Nellis et al (2004) data
(6) Nitrogen, methane, ethane, propane and isobutane mixtures.
horizontal tube (ID= mm).
Mass fluxes = kg/m2-s
Pressures = kPa
constant heat flux of 80 kW/m2 .
AAD = 19%

12. Validation using Barraza et al (2015) data
2, 3, 4 and 5 components mixtures.
Nitrogen-hydrocarbons mixtures
Argon-Fluorochemical refrigerants mixtures.
Temperatures between 100 K and room temperature.
horizontal tubes (0.5 to 3.0 mm)
heat fluxes = kW/m2
mass flux = 140 to 250 kg/m2-s
pressure of 270 and 790 kPa
surface roughness effects

13. Validation using Barraza et al (2015) data

14. Data prediction

15. Applicability criteria
Assuming Cicchitti et al. (1959) homogeneous model a dimensionless factor is defined:

16. Acknowledgements
This work was sponsored by ASHRAE, Research Project 1602-TRP.

17. Solar Energy Lab
Description and validation of the Little correlation for boiling zeotropic mixtures in horizontal tubes from cryogenic to room temperature
Rodrigo Barrazaa,b, Gregory Nellisa, Sanford Kleina, Douglas Reindla
aDepartment of Mechanical Engineering, University of Wisconsin, USA
bDepartment of Mechanical Engineering, Universidad Tecnica Federico Santa Maria, Chile