5.2. A liquid-level system, such as the one shown in Fig. 5–1, has a cross-sectional area of 3.0 ftº. The
valve characteristics are
9 =
8 vh
where q = flow rate, cfm, and h = level above the
valve, ft. Calculate the time constant for this system
if the average operating level above the valve is
(a) 3 l
(b) 9 fu

Ahe-xe mixture containing a 0.75 mole fraction of helium is used for cooling electronics in an avionics application. at a temperature of 300 k and atmospheric pressure, calculate the mass fraction of helium and the mass density, molar concentration and molecular weight of the mixture. if the cooling capacity is 10 l, what is the mass of the coolant?