CRITICAL HEAT-FLUX INVESTIGATION FOR RECOVERY BOILER FLOOR TUBES

The critical heat flux (CHF) behavior of recovery boiler floor tubes h as been studied for three different slopes at a heat flux of about 210 kW/m(2). With a tube slope of 5 degrees, full cooling was achieved at all tested water velocities and at all locations along the tested tub e. For a horizontal tube, however, loss of cooling because of vapor bl anketing appeared at a water velocity of 1 m/s at the 75-bar system pr essure. With an intermediate tube slope of 2 degrees, temperature upse t reaching 40 degrees C was observed both at low and at high steam qua lity conditions, indicating partial vapor blanketing of the top of the tube.