This paper presents a review of the available methods for prediction of forced convective boiling of mixtures. Some of the widely used correlations and design ...
A Review of Heat and Mass Transfer in Boiling of Binary Mixtures
by: J.R. Barbosa, Jr., V.V. Wadekar* and G.F. Hewitt Department of Chemical Engineering and Chemical Technology, Imperial College, London, SW7 2BY *HTFS, AEA Technology, Harwell
ABSTRACT This paper presents a review of the available methods for prediction of forced convective boiling of mixtures. Some of the widely used correlations and design methods are reviewed and compared with more sophisticated approaches that give a detailed description of mass transfer effects as well as of phenomenological aspects of the flow field (Barbosa and Hewitt, 1999). The theoretical predictions are compared with experimental data obtained from the High Pressure Boiling Rig using binary hydrocarbon mixtures (Kandlbinder, 1997). The results point out that, in the annular flow regime, the consideration of combined effects due to droplet interchange and mass transfer resistance at regions adjacent to the liquid/vapour interface lead to a considerable improvement of the predictions of wall temperature and heat transfer coefficient.
OBJECTIVES To review the available calculation methodologies for forced convective boiling of binary mixtures; heat transfer coefficient
Single Component Mixture
Heat transfer coefficient decreases with increasing quality!
quality
Methods are presented in order of increasing complexity, i.e., how complex are the mass transfer calculations.
METHODS REVIEWED Correlations (Chen, 1966; Bennett and Chen, 1980; Palen, 1983; Kandlikar, 1998);
Equilibrium (SBG) Methods (Palen et al., 1980; Sardesai et al., 1982; Murata and Hashizume, 1993);
Film (Colburn) Methods (Shock, 1976; Barbosa and Hewitt, 1999).
EXPERIMENTAL DATA Primary circuit
High Pressure Boiling facility. Pentane and iso-octane mixtures;
Vent Condenser, C1 C6
BD3
V38
V90 Test
Dump
Section
Cooler
NRV4
V43
C5 PS4
BD1
C7
V88 PS9
V36
Flame Arrester
C8
V32
Compare the results with data obtained by Kandlbinder (1997) for wall temperature and heat transfer coefficient.
Degasing circuit
Pressurising circuit
Sampling device Density meter Cooling
Pre-heater
TA1
Storage tank
Heating
Pressure Control valve
Flowmeter
V2
V14 Pressurising pumps P1
P9
Circulating pump, P8 P11
Seal pumps
P10
Vacuum Pump P6
HEAT TRANSFER COEFFICIENT q! w α= ( Tw − TE ) inner wall temperature;
heat flux to the tube wall; equilibrium temperature (local enthalpy);
Increase in wall temperature due to mixture effects, e.g., preferential evaporation of the more volatile component.
INTERPHASE TRANSFER Correlations; No direct account for mass transfer effects; Equilibrium Methods; Mass transfer resistance assumed equal to resistance to heat transfer;
Film Methods; Direct account for mass transfer effects; Droplet entrainment and deposition (Barbosa and Hewitt, 1999).
RESULTS
380.00
Kandlbinder ,1997
Temperature [K]
376.00
Wall temperature predictions
Barbosa and Hewitt (1999)
~ xov ,1 = 0.7;
372.00
p = 0.23 MPa;
Sardesai et al. (1982)
368.00
! T = 292.8 m q! w = 49.8
Palen (1983)
364.00
Kandlikar (1998) 360.00 2.00
4.00
6.00
distance [m]
8.00
10.00
kg 2
m s kW m2
.
;
RESULTS 440.00
Kandlbinder, 1997
Temperature [K]
430.00
Wall temperature predictions
Barbosa and Hewitt (1999) Sardesai et al. (1982)
420.00
~ xov ,1 = 0.7; p = 0.61 MPa;
Palen (1983)
! T = 295.0 m
Kandlikar (1998)
410.00
q! w = 60.2
400.00 2.00
4.00
6.00
distance [m]
8.00
10.00
kg 2
m s kW m2
.
;
RESULTS Heat transfer coefficient [W/m2K]
5000
Heat transfer coefficient predictions
Kandlikar (1998)
4000
Palen (1983)
~ xov ,1 = 0.7; p = 0.23 MPa;
3000
Sardesai et al. (1982)
! T = 292.8 m Barbosa and Hewitt (1999)
2000
q! w = 49.8
Kandlbinder, 1997 1000 2.00
4.00
6.00
distance [m]
8.00
10.00
kg 2
m s kW m2
.
;
RESULTS 4500
Kandlbinder, 1997
Heat transfer coefficient [W/m2K]
4000
Heat transfer coefficient predictions
Kandlikar (1998)
~ xov ,1 = 0.7;
Palen (1983) 3500
p = 0.61 MPa; 3000
! T = 295.0 m
2500
Barbosa and Hewitt (1999)
Sardesai et al. (1982)
2000 2.00
4.00
6.00
distance [m]
8.00
10.00
q! w = 60.2
kg 2
m s kW m2
.
;
CONCLUSION Review of the available methodologies for calculation of forced convective boiling of binary mixtures at high qualities; Methods reviewed were correlations, equilibrium methods and film methods; Results were compared with experimental data for boiling of a pentane/iso-octane mixture obtained at the High Pressure Boiling facility; As in condensation, a more detailed methodology (Film Method), incorporating phenomenological features of the flow gave better predictions.
