A method is given, with results, for establishing recommendations in the form of a table and analytical relationships to describe critical heat fluxes in annular channels. The analytical method was developed for a restricted parameter range and has been used up to the present time in engineering design calculations for concentric annular channels. The table makes it possible to determine critical heat fluxes in smooth concentric and eccentric annular channels with unilateral and bilateral heating over a wide parameter range relatively quickly and quite reliably. The method of calculation is presented. Appropriate algorithms and programs are available at the Power Physics Institute.
SEMIEMPIRICAL METHOD FOR A LIMITED PARAMETER RANGEA semiempirical method for critical heat fluxes was developed on the basis of experimental data for smooth annular channels with unilateral (internal or external) heating, consisting of 2906 experimental points held in the data bank of the Physics and Power Institute. The method was established in the 1970's and improved in the 1980"s. It can be applied in a relatively narrow range of parameters and geometric dimensions.The system of dependences for critical heat fluxes is of the formwhere K I = alp 2 + a2p + a3; m = a4p 2 + a5p + a6; K x = a7p 2 + a8p + a9, mx = al0p + all, p = P/Per; Per is the critical water pressure; g = O/1000; O is the mass flow velocity in units of I kg.m-2.sec-t; K d = (0.007/dT)0-t'/(0.93 -0.07dh/0.0I?5) is a correction to the thermal diameter; K t = I + 1.28exp(-3.6L/Lsf) is a correction to the heated length: Lsf = 0.8"/ -0.59p. In these equations L is the heated length; d T is the thermal diameter in meters; d h is the heated diameter. The coefficients al-al I differ for two different regions of X: for X < Xii m one has al, a2, a3, a4, a5, a6, a7, a8, a9, at0, and all, respectively, equal to 5.17, -13.13, 9.4], 0, 0, 0.7, -0.9'/, I, 0.47, 0.41, and -0.8; for X > Xii m one has al, a2, a3, a4, a5, a6, a'/, ag, a9, at0, and all, respectively, equal to 4.48, -16.49, 12.9, -0.88, 1.795, -0.202, 0, 0, 0.6, 0, and -0.44, where Xli m = (0.'/5p 2 -1.2"/5p + 0.7)g -0,4. The method is recommended for pressures from "/ to 20 MPa, mass velocities from 250 to 3500 kg.m-2.sec -I, steam contents from -1. I to 0.5, heated diameters from 0.004 to 0.045 m, and heated lengths from 0. ! to 1.5 m. The rootmean-square spread here is less than 17% in the output parameters for zero mean deviation. Verification of the method for a new data array in a wider parameter range (P > 7 MPa, X between -I.1 and 0.9, G between 150 and 6000 kg.m-2.sec -l) has shown that it describes the experimental data with an error (in the input parameters): for external heating (1721 points) the mean deviation is 0%, and the root-mean-square spread is 10%; for internal heating (3094 points) these figures are 4 and 15%, respectively. On the average the experimental data are higher than the calculated data.In recent times, especially in connection with the accident at the Chernobyl nuclear power station, the n...
