Steam at a pressure of 0.08 bar and a quality of 93.2% enters an insulated shell
ID: 1816998 • Letter: S
Question
Steam at a pressure of 0.08 bar and a quality of 93.2% enters an insulated shell-and-tube heat exchanger where it condenses on the outside of the tubes through which cooling water flows. The steam exits the heat exchanger as a saturated liquid at 0.08 bar. The mass flow rate of the condensing steam is 3.4 x 105 kg/hr. Cooling water enters the tubes at 15 °C and exits at 35 °C with negligible change in pressure. Neglecting kinetic and potential energy effects, determine the mass flow rate of the cooling water (kg/hr) for steady-state operation.Explanation / Answer
from question i suppose that ms = 3.4 x 105 kg/hr
from tables, hfg = 2250.99 kj/kg and cp = 4.2 kj/kg
clearly energy of steam is transferred to water so
ms * x * hfg = mw * cp * (dt)
3.4 x 105 * 0.932 * 2250.99 = mw * 4.2 * (35-15)
mw = 84.9 * 105 kg/hr