ISSN Online: 2377-424X
ISBN Print: 0-89116-909-1
International Heat Transfer Conference 9
CRITICAL HEAT FLUX DURING NATURAL CONVECTIVE BOILING IN VERTICAL UNIFORMLY HEATED TUBES SUBMERGED IN SATURATED LIQUID
Аннотация
An experimental study has been made of critical heat flux (CHF) of natural convective boiling in vertical uniformly heated tubes. The experiment was performed at a pressure of P = 0.1 to 3.1 MPa for the tube diameter of D = 1.12 to 18.4 mm, the tube length of L = 23 to 960 mm and three kinds of liquids. The effects of the pressure which corresponds to the density ratio ρG/ρL ranging from 6.24 × 10−4 to 0.236 and of the ratio of L/D = 5 to 857 on the CHF, are mainly discussed. The experiment shows that the characteristics of the CHF can be first divided into two regimes at a point that a nondimensional parameter of D* = D/√(σ/g(ρL-ρG)) is equal to about 13. In addition, the CHF in D* < 13 can be divided into two regimes: the CHF of L/D < 240 takes place under the condition of slug or annular flow and then the CHF data can be predicted with an accuracy of ± 20 % by [2], and the CHF of L/D = 857 may be caused by a flooding. On the contrary, the CHF in D* > 13 occurs under the same condition as the CHF in pool boiling. Then the CHF data are also correlated by [4], in which the tube diameter has no effect on the CHF.