A Review of Heat and Mass Transfer in Boiling of

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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.