Chapter 10: Problem 99
Consider a non-boiling gas-liquid two-phase flow in a tube, where the ratio of the mass flow rate is \(\dot{m}_{l} / \dot{m}_{g}=300\). Determine the flow quality \((x)\) of this non-boiling two-phase flow.
Chapter 10: Problem 99
Consider a non-boiling gas-liquid two-phase flow in a tube, where the ratio of the mass flow rate is \(\dot{m}_{l} / \dot{m}_{g}=300\). Determine the flow quality \((x)\) of this non-boiling two-phase flow.
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Get started for freeSaturated ammonia vapor at \(25^{\circ} \mathrm{C}\) condenses on the outside of a 2 -m-long, \(3.2\)-cm-outer-diameter vertical tube maintained at $15^{\circ} \mathrm{C}\(. Determine \)(a)\( the average heat transfer coefficient, \)(b)$ the rate of heat transfer, and \((c)\) the rate of condensation of ammonia. Assume turbulent flow and that the tube diameter is large, relative to the thickness of the liquid film at the bottom of the tube. Are these good assumptions?
Water is to be boiled at sea level in a 30 -cm-diameter mechanically polished AISI 304 stainless steel pan placed on top of a \(3-\mathrm{kW}\) electric burner. If 60 percent of the heat generated by the burner is transferred to the water during boiling, determine the temperature of the inner surface of the bottom of the pan. Also, determine the temperature difference between the inner and outer surfaces of the bottom of the pan if it is \(6 \mathrm{~mm}\) thick. Assume the boiling regime is nucleate boiling. Is this a good assumption?
Water is boiled at atmospheric pressure by a horizontal polished copper heating element of diameter \(D=0.5\) in and emissivity \(\varepsilon=0.2\) immersed in water. If the surface temperature of the heating element is \(788^{\circ} \mathrm{F}\), determine the rate of heat transfer to the water per unit length of the heating element.
Consider a two-phase flow of air-water in a vertical upward stainless steel pipe with an inside diameter of \(0.0254\) \(\mathrm{m}\). The two-phase mixture enters the pipe at \(25^{\circ} \mathrm{C}\) at a system pressure of $201 \mathrm{kPa}\(. The superficial velocities of the water and air are \)0.3 \mathrm{~m} / \mathrm{s}\( and \)23 \mathrm{~m} / \mathrm{s}$, respectively. The differential pressure transducer connected across the pressure taps set $1 \mathrm{~m}\( apart records a pressure drop of \)2700 \mathrm{~Pa}$, and the measured value of the void fraction is \(0.86\). Using the concept of the Reynolds analogy, determine the two-phase convective heat transfer coefficient. Use the following thermophysical properties for water and air: $\rho_{l}=997.1 \mathrm{~kg} / \mathrm{m}^{3}, \mu_{l}=8.9 \times 10^{-4} \mathrm{~kg} / \mathrm{m} \cdot \mathrm{s}, \mu_{s}=4.66 \times\( \)10^{-4} \mathrm{~kg} / \mathrm{m} \cdot \mathrm{s}, \operatorname{Pr}_{l}=6.26, k_{l}=0.595 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K}, \sigma=0.0719 \mathrm{~N} / \mathrm{m}\(, \)\rho_{g}=2.35 \mathrm{~kg} / \mathrm{m}^{3}$, and \(\mu_{g}=1.84 \times 10^{-5} \mathrm{~kg} / \mathrm{m} \cdot \mathrm{s}\).
Design the condenser of a steam power plant that has a thermal efficiency of 40 percent and generates \(10 \mathrm{MW}\) of net electric power. Steam enters the condenser as saturated vapor at \(10 \mathrm{kPa}\), and it is to be condensed outside horizontal tubes through which cooling water from a nearby river flows. The temperature rise of the cooling water is limited to \(8^{\circ} \mathrm{C}\), and the velocity of the cooling water in the pipes is limited to \(6 \mathrm{~m} / \mathrm{s}\) to keep the pressure drop at an acceptable level. Specify the pipe diameter, the total pipe length, and the arrangement of the pipes to minimize the condenser volume.
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