Abstract

Phase separation has been proven to be beneficial to air-cooled parallel flow microchannel condensers for air conditioning systems. The inlet to the condenser with phase separation is at the middle of the condenser height. After the first pass, in the vertical second header of the condenser, refrigerant vapor separates from liquid mainly due to gravitational effects. In ideal case, vapor should go to the top exit and liquid to the bottom exit, resulting in increased heat transfer. Due to interaction between vapor and liquid, separation is not perfect, expressed through the separation efficiency. This paper presents a parametric study of phase separation efficiency in the intermediate headers, with the target to improve separation efficiency. Header prototypes which have two exits are made with transparent polyvinyl chloride (PVC) to simulate the real header and provide visual access. Using R-134a as a baseline, the measurement of separation efficiency and its general trend will be shown first. The experimental results are compared to the simulation of a mechanistic model based on flow regime and force balance analysis. Inlet mass flux in simulation is controlled at 87–311 kg · m−2 · s−1 and inlet quality at 0.05–0.25. The observed flow patterns in header are compared with the modeling results. Then, the header diameter is increased, which effectively improves the separation efficiency due to reduction of vapor velocity in header. Finally, R245fa and R32 are modeled in comparison with R-134a to discuss the effect of fluid properties on separation efficiency.

References

References
1.
Li
,
J.
, and
Hrnjak
,
P.
,
2017
, “
Separation in Condensers as a Way to Improve Efficiency
,”
Int. J. Refrig.
,
79
, pp.
1
9
.10.1016/j.ijrefrig.2017.03.017
2.
Li
,
J.
, and
Hrnjak
,
P.
,
2017
, “
Improvement of Condenser Performance by Phase Separation Confirmed Experimentally and by Modeling
,”
Int. J. Refrig.
,
78
, pp.
60
69
.10.1016/j.ijrefrig.2017.03.018
3.
Kuo
,
W. S.
,
Lie
,
Y. M.
,
Hsieh
,
Y. Y.
, and
Lin
,
T. F.
,
1999
, “
Condensation Heat Transfer and Pressure Drop of Refrigerant R-410A Flow in a Vertical Plate Heat Exchanger
,”
Int. J. Heat Mass Transfer
,
42
(
4
), pp.
697
708
.10.1016/S0017-9310(98)00195-1
4.
Cavallini
,
A.
,
Censi
,
G.
,
Del Col
,
D.
,
Doretti
,
L.
,
Longo
,
G. A.
, and
Rossetto
,
L.
,
2001
, “
Experimental Investigation on Condensation Heat Transfer and Pressure Drop of New HFC Refrigerants (R134a, R125, R32, R410A, R236ea) in a Horizontal Smooth Tube
,”
Int. J. Refrig.
,
24
(
1
), pp.
73
87
.10.1016/S0140-7007(00)00070-0
5.
Bandhauer
,
T. M.
,
Agarwal
,
A.
, and
Garimella
,
S.
,
2006
, “
Measurement and Modeling of Condensation Heat Transfer Coefficients in Circular Microchannels
,”
ASME J. Heat Transfer
,
128
(
10
), pp.
1050
1059
.10.1115/1.2345427
6.
Xiao
,
J.
, and
Hrnjak
,
P.
,
2016
, “
Heat Transfer and Pressure Drop of Condensation From Superheated Vapor to Subcooled Liquid
,”
Int. J. Heat Mass Transfer
,
103
, pp.
1327
1334
.10.1016/j.ijheatmasstransfer.2016.08.036
7.
Li
,
J.
, and
Hrnjak
,
P.
,
2018
, “
Visualization and Quantification of Separation of Liquid-Vapor Two-Phase Flow in a Vertical Header at Low Inlet Quality
,”
Int. J. Refrig.
,
85
, pp.
144
156
.10.1016/j.ijrefrig.2017.09.018
8.
Li
,
J.
, and
Hrnjak
,
P.
,
2019
, “
Phase Separation in Vertical Header of Microchannel Condensers: A Mechanistic Model
,”
ASME
Paper No. FEDSM2018-83311.10.1115/FEDSM2018-83311
9.
Wallis
,
G. B.
,
1969
,
One-Dimensional Two-Phase Flow
,
McGraw-Hill
,
New York
.
10.
Beale
,
J. C.
, and
Reitz
,
R. D.
,
1999
, “
Modeling Spray Atomization With the Kelvin-Helmholtz/Rayleigh-Taylor Hybrid Model
,”
Atomization Sprays
,
9
(
6
), pp.
623
650
.10.1615/AtomizSpr.v9.i6.40
11.
Turner
,
R. G.
,
Hubbard
,
M. G.
, and
Dukler
,
A. E.
,
1969
, “
Analysis and Prediction of Minimum Flow Rate for the Continuous Removal of Liquids From Gas Wells
,”
J. Pet. Technol.
,
21
(
11
), pp.
1475
1482
.10.2118/2198-PA
12.
Gas Processors Suppliers Association (GPSA)
,
2004
,
Engineering Data Book
,
Gas Processors Suppliers Association
,
Tulsa, OK
.
13.
Zivi
,
S. M.
,
1964
, “
Estimation of Steady-State Steam Void-Fraction by Means of the Principle of Minimum Entropy Production
,”
ASME J. Heat Transfer
,
86
(
2
), pp.
247
251
.10.1115/1.3687113
14.
Friedel
,
L.
,
1979
, “
Improved Friction Pressure Drop Correlations for Horizontal and Vertical Two Phase Pipe Flow
,”
3R Int.
,
18
(
7
), pp.
485
491
.https://jglobal.jst.go.jp/en/detail?JGLOBAL_ID=201002057597311499&rel=0
15.
Li
,
J.
, and
Hrnjak
,
P.
,
2018
, “
An Experimentally Validated Model for Microchannel Condensers With Separation Circuiting
,”
17th International Refrigeration and Air-Conditioning Conference at West Lafayette
,
IN
,
July 9–12
, Paper No. 2658.
16.
Li
,
J.
, and
Hrnjak
,
P.
,
2018
, “
Design for Microchannel Condensers With Separation Circuiting
,”
17th International Refrigeration and Air-Conditioning Conference at West Lafayette
,
IN
,
July 9–12
, Paper No. 2684.
You do not currently have access to this content.