Thermodynamics

If the initial temperature of the egg is 5°C, the maximumamount of heat transfer to the egg is(a) 12 kJ(d ) 18 kJ(b) 30 kJ(e) infinity(c) 24 kJ4–162 An apple with an average mass of 0.18 kg and averagespecific heat of 3.65 kJ/kg · °C is cooled from 22°C to5°C. The amount of heat transferred from the apple is(a) 0.85 kJ (d ) 11.2 kJ(b) 62.1 kJ (e) 7.1 kJ(c) 17.7 kJ4–163 The specific heat at constant pressure for an ideal gasis given by c p 0.9 (2.7 10 4 )T (kJ/kg · K) where T is inkelvin. The change in the enthalpy for this ideal gas undergoinga process in which the temperature changes from 27 to127°C is most nearly(a) 90 kJ/kg (d ) 108.9 kJ/kg(b) 92.1 kJ/kg (e) 105.2 kJ/kg(c) 99.5 kJ/kg4–164 The specific heat at constant volume for an ideal gasis given by c v 0.7 (2.7 10 4 )T (kJ/kg · K) where T isin kelvin. The change in the internal energy for this ideal gasundergoing a process in which the temperature changes from27 to 127°C is most nearly(a) 70 kJ/kg (d ) 82.1 kJ/kg(b) 72.1 kJ/kg (e) 84.0 kJ/kg(c) 79.5 kJ/kg4–165 A piston–cylinder device contains an ideal gas. Thegas undergoes two successive cooling processes by rejectingheat to the surroundings. First the gas is cooled at constantpressure until T 2 – 3 4 T 1 . Then the piston is held stationarywhile the gas is further cooled to T 3 – 1 2 T 1 , where all temperaturesare in K.1. The ratio of the final volume to the initial volume of thegas is(a) 0.25 (d ) 0.75(b) 0.50 (e) 1.0(c) 0.672. The work done on the gas by the piston is(a) RT 1 /4 (d ) (c v c p )T 1 /4(b) c v T 1 /2 (e) c v (T 1 T 2 )/2(c) c p T 1 /23. The total heat transferred from the gas is(a) RT 1 /4 (d ) (c v c p )T 1 /4(b) c v T 1 /2 (e) c v (T 1 T 3 )/2(c) c p T 1 /24–166 Saturated steam vapor is contained in a piston–cylinderdevice. While heat is added to the steam, the piston is heldstationary, and the pressure and temperature become 1.2 MPaand 700°C, respectively. Additional heat is added to the steamChapter 4 | 217until the temperature rises to 1200°C, and the piston moves tomaintain a constant pressure.1. The initial pressure of the steam is most nearly(a) 250 kPa (d ) 1000 kPa(b) 500 kPa (e) 1250 kPa(c) 750 kPa2. The work done by the steam on the piston is most nearly(a) 230 kJ/kg (d ) 2340 kJ/kg(b) 1100 kJ/kg (e) 840 kJ/kg(c) 2140 kJ/kg3. The total heat transferred to the steam is most nearly(a) 230 kJ/kg (d ) 2340 kJ/kg(b) 1100 kJ/kg (e) 840 kJ/kg(c) 2140 kJ/kgDesign, Essay, and Experiment Problems4–167 Using a thermometer, measure the boiling temperatureof water and calculate the corresponding saturation pressure.From this information, estimate the altitude of yourtown and compare it with the actual altitude value.4–168 Find out how the specific heats of gases, liquids, andsolids are determined in national laboratories. Describe theexperimental apparatus and the procedures used.4–169 Design an experiment complete with instrumentationto determine the specific heats of a gas using a resistanceheater. Discuss how the experiment will be conducted, whatmeasurements need to be taken, and how the specific heatswill be determined. What are the sources of error in your system?How can you minimize the experimental error?4–170 Design an experiment complete with instrumentationto determine the specific heats of a liquid using a resistanceheater. Discuss how the experiment will be conducted,what measurements need to be taken, and how the specificheats will be determined. What are the sources of error inyour system? How can you minimize the experimental error?How would you modify this system to determine the specificheat of a solid?4–171 You are asked to design a heating system for aswimming pool that is 2 m deep, 25 m long, and 25 m wide.Your client desires that the heating system be large enough toraise the water temperature from 20 to 30°C in 3 h. The rateof heat loss from the water to the air at the outdoor designconditions is determined to be 960 W/m 2 , and the heater mustalso be able to maintain the pool at 30°C at those conditions.Heat losses to the ground are expected to be small and can bedisregarded. The heater considered is a natural gas furnacewhose efficiency is 80 percent. What heater size (in kWinput) would you recommend to your client?4–172 It is claimed that fruits and vegetables are cooled by6°C for each percentage point of weight loss as moisture