Suppose a boil water notice is sent out advising all residents in the area to boil their water before drinking it or using it for cooking. You need to boil 10.5 L10.5 L of water using your natural gas (primarily methane) stove. What volume of natural gas is needed to boil the water if only 17.3%17.3% of the heat generated goes towards heating the water. Assume the density of methane is 0.668 g/L0.668 g/L, the density of water is 1.00 g/mL1.00 g/mL, and that the water has an initial temperature of 22.1 °C22.1 °C. Enthalpy of formation values can be found in this table. Assume that gaseous water is formed in the combustion of methane.

21. A large containment is filled with steam, air, and nitrogen. The containment also has a pool of water, which is sprayed in the containment atmosphere. Heat is added to the con- tainment at a specified rate. Use the given data to find a) the initial containment pressure and b) the time it takes for the containment pressure to reach the pressure limit of 145 psia (1 MPa). Total mass of water (water in the pool and steam) m,, = 3.42E6 lbm (1.55E6 kg) Water-steam quality x = 0.03 Air mass m, = 0.132E6 lbm (6E4 kg) Nitrogen mass m, = 2200 lbm (998 kg) Containment initial temperature T; = 688 R (109 C) Initial relative humidity ø = 100% Rate of heat addition to containment atmosphere Q = 1.02E8 Btu/h (30 MW) [Ans.: 7.66 h].

Pure oxygen (O2) at high pressure is sometimes used in chemical processes instead of air to avoid the high cost of pressurizing all the N2 that inevitably comes with use of air as well as additional cost of capital equipment such as heat exchangers, reactors, etc. through which the (generally unnecessary) nitrogen flows. The decision of which to use (pure O2 or air) is based on the tradeoff between the cost of obtaining the pure O2 (via cryogenic distillation or membrane separation) versus the cost of all the unnecessary N2 running through the process. Your process utilizes O2 at -70°C and 10.2 atm absolute. If the mass flow rate of O2 is 8.0 kg/min, determine the volumetric flow rate of the O2 stream using (a) the ideal gas EOS and (b) the SRK EOS.

2. Fruit is impeded from ripening when it reaches high temperatures (>32°C). Farmer Joe is roo worried that Princeton's summer heat wave will affect the ripening of his ground cherries. The spherical fruit (1 cm in diameter) is surrounded by a spherical papery husk (husk = 0.3 W/m K) with an inner diameter of 2 cm and an outer diameter of 2.1 cm. The air in between the fruit and the husk is stagnant (air = 0.03 W/m K). On a calm day in July, the Princeton air (outside of the husk) is very warm, with a temperature of ~38°C and a heat transfer coefficient of hPrinceton,calm = 10 W/m².K. (a) Sketch the system, labeling all temperatures, dimensions, and proportionality constants.