Boiling liquids maximum flux

For liquid boiling the designer is limited by a maximum flux q/A. This handbook cannot treat this subject in detail. For most applications assuming a limiting flux of 10,000 will give a ballpark estimate. 

Maximum Flux at Critical Temperature Difference for Various Liquids Boiling in Pools Heated by Steam Condensing inside Submerged Tubes... 

Clinch, J. M., andH. B. Karplus, 1964, An Analytical Study of the Propagation of Pressure Waves in Liquid Hydrogen-Vapor Mixtures, Report IITRI-N-6054-6, IIT Research Inst., NASA-CR-54015. (3) Cobb, C. B., and E. L. Park, Jr., 1969, Nucleate Boiling—A Maximum Heat Flux Correlation for Corresponding States Liquids, Chem. Eng. Prog. Symp. Ser. 65(92) 188—193. (4)... 

Number of researchers reports the liquid forced convection inside narrow channels is a most valuable form of heat removal from heat sinks [13-16]. However, the respective key issues are the maximum attainable heat flux by using liquid forced convection, and its value in comparison with the preeminent alternatives of boiling critical heat fluxes. We believe that maximum heat flux could be accomplished by using the inverted meniscus principle of evaporation coupled with excluding of vapor... 

Similar results have been obtained by Bonilla and Perry 79>, Insinger and Bliss 801, and others for a number of organic liquids such as benzene, alcohols, acetone, and carbon tetrachloride. The data in Table 9.9 for liquids boiling at atmospheric pressure show that tile maximum heat flux is much smaller with organic liquids than with water and the temperature difference at this condition is rather higher. In practice the critical value of AT may be exceeded. Sauer et al.m] found that the overall transfer coefficient U for boiling ethyl acetate with steam at 377 kN/m2 was only 14 per cent of that when the steam pressure was reduced to 115 kN/m2. 

Table 9.9. Maximum heal flux for various liquids boiling at atmospheric pressure...

The position of the meniscus within the micro-channel defines the type of temperature distribution. In the first case, when the meniscus is near the outlet, the temperature gradient of the vapor region is small. The rate of evaporation is determined mainly by the heat flux in the liquid region. Therefore, the necessary condition of the evaporation consists of the existence of the region (near the meniscus), where the water is overheated (its temperature is higher than the temperature of boiling). The heat losses to the inlet tank cause the existence of the temperature maximum. 

Point C in Figure 15.14 is termed the critical heat flux or maximum boiling flux or peak boiling flux as bubbles coalesce on the surface creating a vapor blanket. Critical heat flux occurs because insufficient liquid is able to reach the heat transfer surface due to the rate at which vapor is leaving. Beyond Point D, the surface is dry and entirely blanketed by vapor and heat is transferred by conduction and radiation. 

A test of Eq. (21), or (20), is shown in Fig. 14. The same maximum heat-flux data of Cichelli and Bonilla (C2) for three organic liquids which produced three separate lines by Rohsenow s correlation give a single line on the Forster-Zuber plot. The data of Kazakova (Kl) for water boiling at pressures varying from 10 to 80% of the critical pressure also fit the line nicely. 

Rohsenow, W. M.. and P. Griffith Correlation of Maximum Heat Flux Data for Boiling of Saturated Liquids, AlChE-ASME Heat Transfer Symp., Louisville. Ky.. 1955. 

Kettle reboilers generate vapor for process purposes by boiling the liquid outside a bundle of horizontal tubes. This process was historically considered to be an example of pool boiling, with the coefficient calculated by a typical nucleate boiling correlation and a maximum heat flux either fixed by experience [48] or by some modification of Equation (6.94) reflecting the size of the tube bundle [49, 50]. 

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