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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

THE EFFECT OF THE TEMPERATURE PULSATIONS ON THE RATE OF HOMOGENEOUS NUCLEATION DURING BULK VAPOR CONDENSATION

Get access (open in a dialog) DOI: 10.1615/IHTC11.460
pages 367-372

要約

Now an interaction of phase transition process and turbulence are an object of attentive consideration (see review Zaichik and Pershukov, 1996). The process of bulk vapor condensation in turbulent flows may be accompanied by temperature pulsations. In connection with it the mixture of the supersaturated vapor and the noncondenced gas is considered. It is proposed that temperature has the small pulsations relatively to its average mean. It is proposed also that the nucleation rate corresponds to the instant temperature at the any maximal frequency of pulsations. It may be prove that influence of pressure pulsation and vapor concentration may be neglected in by comparison with temperature pulsations at a first approximation.
It was considered large and small supersaturating ratio. It was founded the expression for average nucleation rate by the large supersaturating ratio. In its the pulse part is in proportion to average square of relatively pulse temperature, that is the average nucleation rate is not depended on sign of temperature deviation from its average significance. It was obtained the formula for the nucleation rate with negative deviation of temperature for the small supersaturating ratio. The nucleation rate is zero for positive deviation of temperature for the small supersaturating ratio. It was founded the condition for application of obtained formulas.
It was made numerical estimates on base of obtained results.lt was demonstrated, that the nucleation rate may be increase on 50-100 % for the large supersaturating ratio with temperature pulse take into account, and that nucleation rate increase considerably, when temperature deviation is negative for the small supersaturating ratio. Thus influence of temperature pulse on the nucleation rate decrease, when the supersaturating ratio increase. Besides that, when nucleation rate increased with small supersaturation, it may be proposed, that the condensation process with temperature pulse start more early then it take please without temperature pulse. Its corresponds with results of other authors (Vatazhin et al,1986) qualitatively. The recently article (Karyakin et al, 1996), where is presented the experimental data about the temperature pulsations in nonisothermal turbulent flows, gives new possibility for application of the authors results.
The algorithm and computer code was realized for numerical solution by Kutta-Merson method of the system of gas-dynamic and condensation equations. The modeling of the vapor condensation process were made by moment method. The test solutions were made for the condensation process in caesium vapor and argon mixture for one-dimension flow in wedge-formed nozzle. The temperature of the mixture has the small (amplitude = ± 5 %) random pulsations.The stop parameters were chosen for the condensation process in supersonic region of nozzle. From obtained results it is follow, that calculation with temperature pulse displace condensation region to meet flow. The concentration of the drops with temperature pulse is smaller, then without pulse, and average radius - is larger. The degree of condensation (ratio of the mass of the drops to the initial mass of vapor) for both versions in condensation region is identical. The distribution function for drop sizes with temperature pulse have a look of the δ - function row.