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# hw_4 - J Buongiorno Spring 2005 22.313J 2.59J 10.536J...

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J. Buongiorno / Spring 2005 22.313J, 2.59J, 10.536J THERMAL-HYDRAULICS IN POWER TECHNOLOGY Homework Set 4 Pool Boiling in a Stainless Steel Kettle You are to analyze the pool boiling characteristics of water at atmospheric pressure in a kettle for making coffee or tea. The heated surface is horizontal and made of stainless steel. The contact angle for water on stainless steel, θ , is 60 degrees in the temperature range of interest. The saturation properties of water at 0.1 MPa are reported in Table 1. Bubble nucleation at a small re-entrant cavity Consider the active cylindrical re-entrant cavity (r c = 1 μ m) shown in Figure 1. i) First assume that the system is at room temperature, i.e., 20 ° C. This is the situation in Figure 1(A). Calculate the distance x from the edge of the cavity neck. (The vapor pressure and the surface tension at 20 ° C are 2.34 kPa and 0.073 N/m, respectively) ii) Calculate the superheat required for the bubble to rise to the cavity mouth (Figure 1(B)).

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