Problem 186
A Carnot cycle operates between the temperature limits of 300 and \(2000 \mathrm{K},\) and produces \(600 \mathrm{kW}\) of net power. The rate of entropy change of the working fluid during the heat addition process is \((a) 0\) (b) \(0.300 \mathrm{kW} / \mathrm{K}\) \((c) 0.353 \mathrm{kW} / \mathrm{K}\) \((d) 0.261 \mathrm{kW} / \mathrm{K}\) \((e) 2.0 \mathrm{kW} / \mathrm{K}\)
Problem 187
Air in an ideal Diesel cycle is compressed from 2 to \(0.13 \mathrm{L},\) and then it expands during the constant pressure heat addition process to 0.30 L. Under cold air standard conditions, the thermal efficiency of this cycle is (a) 41 percent (b) 59 percent \((c) 66\) percent \((d) 70\) percent \((e) 78\) percent
Problem 188
Helium gas in an ideal Otto cycle is compressed from \(20^{\circ} \mathrm{C}\) and 2.5 to \(0.25 \mathrm{L},\) and its temperature increases by an additional \(700^{\circ} \mathrm{C}\) during the heat addition process. The temperature of helium before the expansion process is \((a) 1790^{\circ} \mathrm{C}\) (b) \(2060^{\circ} \mathrm{C}\) \((c) 1240^{\circ} \mathrm{C}\) \((d) 620^{\circ} \mathrm{C}\) \((e) 820^{\circ} \mathrm{C}\)
Problem 189
In an ideal Otto cycle, air is compressed from \(1.20 \mathrm{kg} / \mathrm{m}^{3}\) and 2.2 to \(0.26 \mathrm{L},\) and the net work output of the cycle is \(440 \mathrm{kJ} / \mathrm{kg} .\) The mean effective pressure (MEP) for this cycle is \((a) 612 \mathrm{kPa}\) \((b) 599 \mathrm{kPa}\) \((c) 528 \mathrm{kPa}\) \((d) 416 \mathrm{kPa}\) \((e) 367 \mathrm{kPa}\)
Problem 190
In an ideal Brayton cycle, air is compressed from \(95 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\) to \(1100 \mathrm{kPa} .\) Under cold-air-standard conditions, the thermal efficiency of this cycle is \((a) 45\) percent (b) 50 percent \((c) 62\) percent \((d) 73\) percent \((e) 86\) percent
Problem 191
Consider an ideal Brayton cycle executed between the pressure limits of 1200 and \(100 \mathrm{kPa}\) and temperature limits of 20 and \(1000^{\circ} \mathrm{C}\) with argon as the working fluid. The net work output of the cycle is \((a) 68 \mathrm{kJ} / \mathrm{kg}\) \((b) 93 \mathrm{kJ} / \mathrm{kg}\) \((c) 158 \mathrm{kJ} / \mathrm{kg}\) \((d) 186 \mathrm{kJ} / \mathrm{kg}\) \((e) 310 \mathrm{kJ} / \mathrm{kg}\)
Problem 192
An ideal Brayton cycle has a net work output of \(150 \mathrm{kJ} / \mathrm{kg}\) and a back work ratio of \(0.4 .\) If both the turbine and the compressor had an isentropic efficiency of 85 percent, the net work output of the cycle would be \((a) 74 \mathrm{kJ} / \mathrm{kg}\) \((b) 95 \mathrm{kJ} / \mathrm{kg}\) \((c) 109 \mathrm{kJ} / \mathrm{kg}\) \((d) 128 \mathrm{kJ} / \mathrm{kg}\) \((e) 177 \mathrm{kJ} / \mathrm{kg}\)
Problem 193
In an ideal Brayton cycle, air is compressed from \(100 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\) to \(1 \mathrm{MPa}\), and then heated to \(927^{\circ} \mathrm{C}\) before entering the turbine. Under cold-air-standard conditions, the air temperature at the turbine exit is \((a) 349^{\circ} \mathrm{C}\) (b) \(426^{\circ} \mathrm{C}\) \((c) 622^{\circ} \mathrm{C}\) \((d) 733^{\circ} \mathrm{C}\) \((e) 825^{\circ} \mathrm{C}\)
Problem 194
In an ideal Brayton cycle with regeneration, argon gas is compressed from \(100 \mathrm{kPa}\) and \(25^{\circ} \mathrm{C}\) to \(400 \mathrm{kPa}\), and then heated to \(1200^{\circ} \mathrm{C}\) before entering the turbine. The highest temperature that argon can be heated in the regenerator is (a) \(246^{\circ} \mathrm{C}\) (b) \(846^{\circ} \mathrm{C}\) \((c) 689^{\circ} \mathrm{C}\) \((d) 368^{\circ} \mathrm{C} \quad(e) 573^{\circ} \mathrm{C}\)
Problem 195
In an ideal Brayton cycle with regeneration, air is compressed from \(80 \mathrm{kPa}\) and \(10^{\circ} \mathrm{C}\) to \(400 \mathrm{kPa}\) and \(175^{\circ} \mathrm{C}\), is heated to \(450^{\circ} \mathrm{C}\) in the regenerator, and then further heated to \(1000^{\circ} \mathrm{C}\) before entering the turbine. Under cold-air-standard conditions, the effectiveness of the regenerator is (a) 33 percent \((b) 44\) percent \((c) 62\) percent \((d) 77\) percent \((e) 89\) percent
