Numerizing of Heat Transfer Coefficient between Water Spray and Heated Metal Specimens

Abstract

The author made four kinds of water spray cooling experiments to numerize heat transfer coefficient h between water spray and a heated specimen as a function of water flux W, water pressure P and specimen surface temperature θ_s. In this report, the author described numerizing of the equation: h=f (W, P, θ_s). The specially fixed water flux W_d (W1 to W4), water pressure P_d (P1 to P4), specimen surface temperature θ_sd (50, 75, to 900°C), and the most probable values of heat transfer coefficient h_sa obtained from these experiments were introduced for numerizing of the above-mentioned equation.
The principal contents are as follows: (1) In each θ_sd, the exponents n1 to n4 of the equation: h_sa=AWⁿ_d corresponding to P_d: P1 to P4 respectively were obtained (A is constant). The mean exponent n is (n1+…+n4)/4. (2)In each θ_sd, the exponents m1 to m4 of the equation: h_sa=BP^m_d corresponding to W_d: W1 to W4 respectively were obtained (B is constant). The mean exponent m is (m1+…+m4)/4. (3) By using n and m, the equation: h=C(WⁿP^m) among arbitrary W, arbitrary P and h was numerized in every θ_sd (C is constant). (4) h_i and h_i+1 corresponding to θ_sd: θ_sdi and θ_sdi+1 respectively were calculated by using the equation: h=C(WⁿP^m). Next, by using the relations: [h_i vs. θ_sdi] and [h_i+1 vs. θ_sdi+1], the equation: h_x=f(θ_sx) to obtain h_x corresponding to an arbitrary θ_sx between θ_sdi and θ_sdi+1, was numerized.