After the carbon is placed inside the bomb the

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Unformatted text preview: (a) Draw a schematic of the water heater and name its most important elements. (b) Using Cantera, determine the amount of heat generated from burning of 1 kg of methane. (c) Calculate the temperature of the hot water if the heat exchanger were to have an efficiency of 1.0, i.e., perfect heat transfer. 2.6 An acetylene-oxygen torch is used in industry for cutting metals. (a) Estimate the maximum flame temperature using average specific heat cp. (b) Measurements indicate a maximum flame temperature of about 3,300 K. Compare with the result from (a) and discuss the main reasons for the discrepancy. 2.7 A space heater burns propane and air with intake temperature at T0 ¼ 25 C and pressure at 1 atm (see Fig. 2.5). The combustible mixture enters the heater at an equivalence ratio f ¼ 0.8. The exhaust gases exit at temperature T1 ¼ 500 K and contain CO2, H2O, O2, and N2 only at station 1. In order to use a 3-way catalyst for exhaust treatment, additional propane is injected into the exhaust to consume all the remaining oxygen in the exhaust such that the gases entering the catalyst contain only CO2, H2O, and N2 at station 2. Assume that the entire system is at P ¼ 1 atm and complete combustion occurs in both the heater and in the exhaust section. (a) The volumetric flow rate of propane entering the heater is 1 L/min. Determine the injection rate of propane into the exhaust between station 1 and station 2 (see Fig. 2.5). Note that the propane at the injection station is at the same conditions as heater inlet, i.e., T ¼ 25 C and P ¼ 1 atm. (b) With the assumption of constant specific heats for the gases, estimate the temperature at station 2, T2. The specific heat can be approximated by that ^ of N2 at 700 K as cp ¼ 30:68 kJ =kmol À K , 46 2 Thermodynamics of Combustion Fuel: Tfuel = 25°C Pfuel = 1 atm Air: Tair = 427°C Pair = 1 atm Products . Qloss Fig. 2.6 Exercise 2.9 2.8 Two grams of solid carbon, C(s), are combusted with pure oxygen in a 500 cm3 bomb calorimeter initially at 300 K. After the carbon is placed inside the bomb, the chamber is evacuated and then filled with gaseous oxygen from a pressurized tank. (a) Determine the minimum O2 pressure inside the bomb necessary to allow complete combustion of the solid carbon. (b) When the bomb is cooled back to it...
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This document was uploaded on 01/20/2014.

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