Kan-ei Shinzato

LAMINAR FORCED CONVECTION CONDENSATION OF SATURATED VAPORS IN THE NEAR-CRITICAL REGION

Abstract A numerical analysis is presented for laminar forced convection condensation of saturated vapors of water and carbon dioxide on a flat surface in the reduced temperature range Tsxa0/xa0Tcxa0=xa00.990-0.999. The heat transfer coefficient in the region Tsxa0/xa0Tcxa0<xa00.998 can be correlated by using Fujii and Ueharas equation when the representative physical properties art evaluated at the film temperature. The reduction of the condensation mass flux or the heat flux at the vapor-liquid interface due to the convection term in the condensate film is expressed as a function of the phase change number with the average isobaric specific heat.

Various formulas and their accuracy concerning convective heat and mass transfer in the vapor boundary layer in the case of laminar film condensation of binary vapor mixtures

Abstract The equations of convective mass transfer are derived from the equations of convective heat transfer by replacing Nuc with Sh and Prv with Sc and also (χ+/ω)Gr with (χ/ω)Gr for free- condensation. As for forced-convection condensation, the equations of Rose and Fujii el al. and the newly presented equation for mass transfer have almost the same accuracy, although their functional forms are quite different from each other. The accuracy of Roses equation for heat transfer decreases as the effect of the enthalpy diffusion term increases. As for free-convection condensation, the newly presented equation for mass transfer is applicable in a wider range of WR or M in comparison with the previous equation of Fujii et al.

二成分混合蒸気の凝縮における気相境界層の代表物性値 : II 層流自由対流凝縮の場合

The numerical analysis is made for free-convection condensation of binary vapor mixtures quite similarly as the case of forced-convection condensation. The physical properties which are evaluated at the arithmetic mean of the mass concentrations at the vapor-liquid interface and the bulk and the corresponding saturation temperature are recommended as the representative ones in the case of the algebraic solution.

Laminar Forced-Convection Condensation of Saturated Vapors in the Subcritical Region.

A numerical analysis is presented for laminar forced-convection condensation of saturated vapors of water and carbon dioxide on a flat surface in the reduced temperature range TS/TC=0.990∼0.999. The heat transfer coefficient in the region TS/TC<0.998 can be correlated by using Fujii and Ueharas equation for constant physical properties when the representative physical properties are evaluated at the film temperature. The reduction of condensation mass flux or the heat flux at the vapor-liquid interface due to the convection term in the film is expressed as a function of the phase change number with the average isobaric specific heat.

Experimental verification of a method for simultaneous measurement of the fouling factor and water velocity inside a condenser tube.

The fouling factor and mean water velocity inside a condenser tube, which is artificially fouled, are simultaneously measured by means of local heating from the outside of the tube with two heaters of different lengths. The principle of the measurement is based on heat-transfer characteristics which depend on heater length. A titanium tube of 24.16 mm i.d. and an aluminum brass tube of 22.77 mm i.d. are used for the test. The test ranges of water velocity and fouling factor are 0.8-2.5 m/s and 0-2×10-4 m2K/W, respectively. Prior to the test, dimensionless relations among tube wall temperature at the heated area, mean water velocity and fouling factor along with their dependence on water temperature are derived from the results of numerical calculation of the temperature distribution near the heated area. The maximum errors for water velocity ΔU and fouling facter ΔR in the test are as follows ; ΔU=2.4% for clean tubes, ΔR=0.5×10-5 m2K/W for given water velocity, and ΔR=2×10-5 m2K/W and ΔU=±20% for the simultaneous measurement.

Laminar forced convective heat transfer inside a locally heated tube.

Forced convective heat transfer to fully developed laminar flow inside a tube which is uniformly heated along a finite length from the outer surface is numerically analysed as a conjugated problem. The four prescribable dimensionless parameters in this analysis are : heated length to inner diameter ratio L*, outer to inner diameter ratio Ro, wall to fluid conductivity ratio Λ, and Peclet number Pe. Effects of the parameters on the distributions of heat flux and wall temperature at the inner surface of the tube, the mixing-cup temperature of fluid and the local Nusselt number are graphically demonstrated. The region affected by axial heat conduction in the wall is discussed with respect to the heat flux distribution and the length of the region is expressed by a function of Λ, Ro and Pe.

On pressure loss of tube banks in cross flow.

There are shown considerable discrepancies among existing diagrams, tables and empirical equations concerning pressure loss coefficient, Euler number, for tube banks of ten or more rows. In the sake of practical application, simple expressions are proposed for the diagrams of typical in-line and staggered tube arrangement in Heat exchanger Design Handbook in the range 10 ≤ Re ≤ 2 × 105 ∼106 within an accuracy of ±3%. Procedure of the formulation and an interpolation technique for applying to the cases of the other tube arrangement, namely the other pitch to diameter rations, are shown by using some examples. Also in proposed a new method of correlation for experimental data on tube banks with small number of rows.