Questions and Answers of Introduction To Chemical Engineering Thermodynamics

As part of a refrigeration cycle, Freon 134a is adiabatically compressed from the saturated vapor at –60°C (note the negative sign on temperature) to 1017 kPa and 100°C.(a) How much work is
An ideal gas stream (Stream A), CP = 5R / 2, 50 mole/h, is heated by a steady-state heat exchanger from 20°C to 100°C by another stream (Stream B) of another ideal gas, CP = 7R / 2, 45 mole/h,
Steam is produced at 30 bar and some unknown temperature. A small amount of steam is bled off and goes through an adiabatic throttling valve to 1 bar. The temperature of the steam exiting the
An inventor has applied for a patent on a device that is claimed to utilize 1 mole/min of air (assumed to be an ideal gas) with temperature independent CP = (7/2)R which enters at 500 K and 2 bar,
Two streams of air are mixed in a steady-state process shown below. Assume air is an ideal gas with a constant heat capacity CP = 7R / 2.(a) What is the temperature of the stream leaving the tank?(b)
Suppose the expansion in problem P2.19 was completely adiabatic instead of isothermal and CP = 7 cal/(mol-K). How would the height of the piston be affected? Must we generate heat or consume heat to
It is desired to determine the volume of an initially evacuated tank by filling it from an 80 liter cylinder of air at 300 bar and 300 K. The final pressure of both tanks is 5 bars. Estimate the
Air is flowing at steady state through a 5 cm diameter pipe at a flow rate of 0.35 mole/min at P = 5 bar and T = 500 K. It flows through a throttle valve and exits at 1 bar. Assume air is an ideal
An insulated cylinder is fitted with a freely floating piston, and contains 0.5 kg of steam at 9 bar and 90% quality. The space above the piston, initially 0.05m3, contains air at 300 K to maintain
A common problem in the design of chemical processes is the steady-state compression of gases from a low pressure P1 to a much higher pressure P2. We can gain some insight about optimal design of
A well-insulated cylinder, fitted with a frictionless piston, initially contained 9 kg of liquid water and 0.4 kg of water vapor at a pressure of 1.4 MPa. 2 kg of steam at 1.6 MPa was admitted to the
Steam flowing at steady state enters a turbine at 400°C and 7 MPa. The exit is at 0.275 MPa. The turbine is 85% efficient. What is the quality of the exiting stream? How much work is generated per
Many action movies show gas cylinders that have their caps knocked off. The tanks go flying around wreaking havoc (only on the bad guys, of course). How much velocity could a tank like that really
An adiabatic steam turbine inlet is to be 4 MPa. The outlet of the turbine is to operate at 0.01 MPa, and provide saturated steam. The turbine has an efficiency of 85%. Determine the superheat which
Steam is fed to an adiabatic turbine at 4 MPa and 500°C. It exits at 0.1 MPa.(a) If the turbine is reversible, how much work is produced per kg of steam?(b) If the turbine is 80% efficient, how much
Methane is compressed in a steady-state adiabatic compressor (87% efficient) to 0.4 MPa. What is the required work per mole of methane in kJ? If the flow is to be 17.5 kmol/h, how much work must be
Methane is to be compressed from 0.05 MPa and -120°F to 5 MPa in a two stage compressor. In between adiabatic, reversible stages, a heat exchanger returns the temperature to -120°F. The
A steady stream (1000 kg/hr) of air flows through a compressor, entering at (300 K, 0.1 MPa) and leaving at (425 K, 1 MPa). The compressor has a cooling jacket where water flows at 1500 kg/hr and
Propane is to be compressed from 0.4 MPa and 360 K to 4 MPa using a two-stage compressor. An interstage cooler returns the temperature of the propane to 360 K before it enters the second compressor.
(a) A steam turbine in a small electric power plant is designed to accept 5000 kg/h of steam at 60 bar and 500°C and exhaust the steam at 1 bar. Assuming that the turbine is adia batic and
Steam is used in the following adiabatic turbine system to generate electricity; 15% of the flow from the first turbine is diverted for other use.(a) How much work (in kJ/h) is generated by the first
Liquid nitrogen is useful for medical purposes and for research laboratories. Determine the minimum shaft work needed to liquefy nitrogen initially at 298 K and 0.1013 MPa and ending with saturated
Propane flows into a steady-state process at 0.2 MPa and 280 K. The final product is to be saturated liquid propane at 300 K. Liquid propane is to be produced at 1000 kg/h. The surroundings are at
Propane (1000 kg/hr) is to be liquefied following a two-stage compression. The inlet gas is to be at 300 K and 0.1 MPa. The outlet of the adiabatic compressor I is 0.65 MPa, and the propane enters
A steam power plant operates on the Rankine cycle according to the specified conditions below. Using stream numbering from Fig. 5.2, for each of the options below, determine:(a) The work output of
A steam power plant operates on the Rankine cycle with reheat, using the specified conditions below. Using stream numbering from Fig. 5.3, for each of the options below, determine(a) The work output
An ordinary vapor compression cycle is to operate a refrigerator on R134a between -40°C and 40°C (condenser temperatures). Compute the coefficient of performance and the heat removed from the
A modified Rankine cycle using a single feedwater preheater as shown in Fig. 5.7 has the following characteristics.(a) The inlet to the first turbine is at 500°C and 0.8 MPa.(b) The feedwater
A simple Rankine cycle is to operate on steam between 200°C and 99.6°C, with saturated steam exhausting from the turbine. What is the maximum possible value for its thermodynamic efficiency?
A modified Rankine cycle uses reheat and one closed feedwater preheater. The schematic is a modification of Fig. 5.7 obtained by adding a reheater between the T-joint and turbine II. Letting stream 3
An ordinary vapor compression cycle is to be operated on methane to cool a chamber to 112 K. Heat is rejected to liquid ethylene at 160 K. The temperatures in the coils are 168 K and 100 K.(a) Write
A regenerative Rankine cycle uses one open feedwater preheater and one closed feedwater preheater. Using the stream numbering from Fig. 5.6, and the specified conditions below, the plant capacity is
A house has an effective heat loss of 100,000 Btu/hr. During the heating season of 160 days the average inside temperature should be 70°F while the outside is 45°F. Freon-134a is the working fluid
A regenerative Rankine cycle utilized the schematic of Fig. 5.6. Conditions are as follows: stream 1, 450°C, 3 MPa; stream 2, 250°C, 0.4 MPa; stream 3, 150°C, 0.1 MPa; stream 4, 0.01 MPa; stream
A regenerative Rankine cycle uses three closed feedwater preheaters. Using the stream numbering from Fig. 5.5, and the specified conditions below, the plant capacity is to be 80 MW. Other constraints
An adiabatic turbine is supplied with steam at 300 psia and 550°F that exhausts at atmospheric pressure. The quality of the exhaust steam is 95%.(a) What is the efficiency of the turbine?(b) What
An ordinary vapor compression refrigerator is to operate on refrigerant R134a with evaporator and condenser temperatures at -20°C and 35°C. Assume the compressor is reversible.(a) Make a table
The low-temperature condenser of a distillation column is to be operated using a propane refrigeration unit. The evaporator is to operate at -20°C. The cooling duty is to be 10,000,000 kJ/ hr. The
An ordinary vapor compression cycle using propane operates at temperatures of 240 K in the cold heat exchanger, and 280 K in the hot heat exchanger. How much work is required per kg of propane
Solve problem 5.11 using an economizer at the intermediate pressure and referring to Fig. 5.10 for stream numbers.Data from problem 5.11:The low-temperature condenser of a distillation column is to
A refrigeration process with interstage cooling uses refrigerant R134a. The outlet of the condenser is to be saturated liquid at 40°C. The evaporator is to operate at -20°C, and the outlet is
A refrigeration process with interstage cooling uses refrigerant R134a, and the outlet of the condenser is to be saturated liquid at 40°C. Refer to Fig. 5.10 for stream numbers in your solution. The
The Claude liquefaction process is to be applied to methane. Using the schematic of Fig. 5.13 for stream numbering, the key variables depend on the fraction of stream 3 that is liquefied, ṁ8/ṁ3,
A Brayton gas turbine typically operates with only a small amount of fuel added so that the inlet temperatures of the turbine are kept relatively low because of material degradation at higher
The thermal efficiency of a Brayton cycle can be increased by adding a regenerator as shown in the schematic below. Consider a Brayton cycle using air under the following conditions: TA = 298 K, PA =
A hexane (ρ ≈ 0.66 kg/L, μ = 3.2 E-3 g/(cm-s)) storage tank in the chemical plant tank farm is 250 m from the 200 L solvent tank that is to be filled in 3 min. A pump is located at the base of
Consider problem 5.16(a). Determine the amount of fuel required per mole of air if the fuel is modeled as isooctane and combustion is complete.Data from problem 5.16(a)A Brayton gas turbine typically
Consider problem 5.18(a). Determine the amount of fuel required per mole of air if the fuel is modeled as isooctane and combustion is complete.Data from problem 5.18(a):Consider the air-standard Otto
In the event of an explosive combustion of vapor at atmospheric pressure, the vapor cloud can be modeled as adiabatic because the combustion occurs so rapidly. The vapor cloud expands rapidly due to
(a) Derive the energy balance for a closed, constant-volume, adiabatic-system vapor phase chemical reaction, neglecting the energy of mixing for reactants and products, and assuming the ideal gas
Consider the air-standard Otto cycle explained in the online supplement. At the beginning of the compression stroke, P1 = 95 kPa, T1 = 298 K. Consider air as an ideal gas stream with CP = 0.79·CP,N2
If U is considered a function of T and P, the “natural” heat capacity is neither CV nor CP, but rather the derivative (∂U/∂T)P . Develop the following connections between (∂U/∂T)P , CP,
A steam plant operates on the cycle of Fig. 8.4. The pressure levels are 10 kPa and 6000 kPa, and steam leaves the turbine as saturated vapor. The pump efficiency is 0.70, and the turbine efficiency
Which is the more effective way to increase the coefficient of performance of a Carnot refrigerator: to increase TC with TH constant, or to decrease TH with TC constant? For a real refrigerator, does
Helium-laced gases are used as breathing media for deep-sea divers. Why? Table 13.2 may provide useful data. Table 13.2: Henry's Constants for Gases Dissolved in Water at
A system formed initially of 2 mol CO2, 5 mol H2, and 1 mol CO undergoes the reactions:Develop expressions for the mole fractions of the reacting species as functions of the reaction coordinates for
For the ammonia synthesis reaction written: With 0.5 mol N2 and 1.5 mol H2 as the initial amounts of reactants and with the assumption that the equilibrium mixture is in the ideal gas state, show
Carbon black is produced by the decomposition of methane:For equilibrium at 650°C and 1 bar, (a). What is the gas-phase composition if pure methane enters the reactor, and what fraction of the
Compute the emf and work output per mole of fuel for a reversible fuel cell that uses methanol as fuel and air as the source of oxygen, operating at 50°C.
Consider a binary system of species 1 and 2 in which the liquid phase exhibits partial miscibility. In the regions of miscibility, the excess Gibbs energy at a particular temperature is expressed by
A dead-weight gauge with a piston diameter of 1 cm is used for the accurate measurement of pressure. If a mass of 6.14 kg (including piston and pan) brings it into balance, and if g = 9.82 m·s−2,
An astronaut weighs 730 N in Houston, Texas, where the local acceleration of gravity is g = 9.792 m·s−2. What are the astronaut’s mass and weight on the moon, where g = 1.67 m·s−2?
At 27°C the reading on a manometer filled with mercury is 60.5 cm. The local acceleration of gravity is 9.784 m·s−2. To what pressure does this height of mercury correspond?
A team from Engineers Without Borders constructs a system to supply water to a mountainside village located 1800 m above sea level from a spring in the valley below at 1500 m above sea level.(a).
Verify that the SI unit of kinetic and potential energy is the joule.
Energy costs vary greatly with energy source: coal @ $35.00/ton, gasoline @ a pump price of $2.75/gal, and electricity @ $0.100/kW·h. Conventional practice is to put these on a common basis by
Consider a microwave that is rated 1100 W and that at full power heats 250 mL of water from 20°C to 95°C in 2 minutes.(a). What is the total change in internal energy of the water? (b). If the
How many phase-rule variables must be specified to fix the thermodynamic state of each of the following systems? (a). Liquid water in equilibrium with its vapor. (b). Liquid water in equilibrium
For liquid acetone at 20°C and 1 bar, For acetone, find: (a). The value of (∂P/∂T)V at 20°C and 1 bar. (b). The pressure after heating at constant V from 20°C and 1 bar to 30°C. (c). The
Express the volume expansivity and the isothermal compressibility as functions of density ρ and its partial derivatives. For water at 50°C and 1 bar, κ = 44.18 × 10−6 bar−1. To what
Generally, volume expansivity β and isothermal compressibility κ depend on T and P. Prove that: (x) =-( ), дк ЭТ др T P
An evacuated tank is filled with gas from a constant-pressure line. Develop an expression relating the temperature of the gas in the tank to the temperature T′ of the gas in the line. Assume the
A tank of 0.1 m3 volume contains air at 25°C and 101.33 kPa. The tank is connected to a compressed-air line which supplies air at constant conditions of 45°C and 1500 kPa. A valve in the line is
For steady flow in a heat exchanger at approximately atmospheric pressure, what is the heat transferred: (a). When 10 mol of SO2 is heated from 200 to 1100°C?(b). When 12 mol of propane is heated
A direct-fired dryer burns a fuel oil with a lower heating value of 19,000(Btu) (lbm)−1. [Products of combustion are CO2(g) and H2O(g).] The composition of the oil is 85% carbon, 12% hydrogen, 2%
An egg, initially at rest, is dropped onto a concrete surface; it breaks. Prove that the process is irreversible. In modeling this process treat the egg as the system, and assume the passage of
Work the preceding problem for mole fractions z1 = 0.32, z2 = 0.45, z3 = 0.23.
The qualitative features of SVE at high pressures shown in Fig. 15.6 are determined by the equation of state for the gas. To what extent can these features be represented by the two-term virial
Any equation of state valid for gases in the zero-pressure limit implies a full set of virial coefficients. Show that the second and third virial coefficients implied by the generic cubic equation of
With respect to the virial expansions, Eqs. (3.33) and (3.34), show that:where ρ ≡ 1/V.Equation (3.33)Equation (3.34) ze, B' = ze and B = др TP=0 Tp=0
PVT data may be taken by the following procedure: A mass m of a substance of molar mass ℳ is introduced into a thermostated vessel of known total volume Vt. The system is allowed to equilibrate,
Consider an ethanol(1)/ethyl acetate(2) mixture with x1 = 0.20, initially at 80°C and 100 kPa. Describe the evolution of phases and phase compositions as the temperature is gradually reduced to
Consider an ethanol(1)/ethyl acetate(2) mixture with x1 = 0.80, initially at 80°C and 100 kPa. Describe the evolution of phases and phase compositions as the temperature is gradually reduced to
Consider a binary liquid mixture for which the excess Gibbs energy is given by GE/RT = Ax1x2 (x1 + 2x2). What is the minimum value of A for which liquid/liquid equilibrium is possible?
A single P–x1 data point is available for a binary system at 35°C. Estimate from the data:(a) The corresponding value of y1.(b) The total pressure at 35°C for an equimolar liquid mixture.(c)
Consider a binary mixture for which the excess Gibbs energy is given by GE/RT = 2.6x1x2. For each of the following overall compositions, determine whether one or two liquid phases will be present. If
Work Prob. 13.47 for the NRTL equation.Prob. 13.47For one of the binary systems listed in Table 13.10, based on Eq. (13.19) and the Wilson equation, make the following calculations:(a) BUBL P : t =
Consider a binary mixture for which the excess Gibbs energy is given by GE/RT = 2.1x1x2 (x1 + 2x2). For each of the following overall compositions, determine whether one or two liquid phases will be
Figures 15.1, 15.2, and 15.3 are based on Eqs. (A) and (F) of Ex. 15.3 with CEP assumed to be positive and given by CEP ∕ R = 3 x1 x2. Graph the corresponding figures for the following cases,
An absolute upper bound on GE for stability of an equimolar binary mixture is GE = RT ln 2 . Develop this result. What is the corresponding bound for an equimolar mixture containing N species?
In Ex. 15.2 a plausibility argument was developed from the LLE equilibrium equations to demonstrate that positive deviations from ideal-solution behavior are conducive to liquid/liquid phase
The system water(l)/n-pentane(2)/n-heptane(3) exists as a vapor at 101.33 kPa and 100°C with mole fractions z1 = 0.45, z2 = 0.30, z3 = 0.25. The system is slowly cooled at constant pressure until it
In Ex. 15.8, Henry’s constant for adsorption k, identified as the intercept on a plot of n∕P vs. n, was found from a polynomial curve-fit of n∕P vs. n. An alternative procedure is based on a
It is demonstrated in Ex. 15.5 that the Wilson equation for GE is incapable of representing LLE. Show that the simple modification of Wilson’s equation given by:can represent LLE. Here, C is a
Use results reported in Ex. 15.8 to prepare plots of Π vs. n and z vs. n for ethylene adsorbed on a carbon molecular sieve. Discuss the plots.Ex. 15.8Nakahara et al.11 report data for ethylene
The UNILAN equation for pure-species adsorption is:where m, s, and c are positive empirical constants.(a) Show that the UNILAN equation reduces to the Langmuir isotherm for s = 0.(b) Show that
It was assumed in the development of Eq. (15.39) that the gas phase is ideal, with Z = 1. Suppose for a real gas phase that Z = Z (T, P). Determine the analogous expression to Eq. (15.39) appropriate
It has been suggested that a value for GE of at least 0.5 RT is required for liquid/liquid phase splitting in a binary system. Offer some justification for this statement.
It is possible in principle for a binary liquid system to show more than one region of LLE for a particular temperature. For example, the solubility diagram might have two side-by-side “islands”
Consider a ternary system comprising solute species 1 and a mixed solvent (species 2 and 3). Assume that:Show that Henry’s constant H1 for species 1 in the mixed solvent is related to Henry’s

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