# Recent questions and answers in Applications

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A steam power cycle with regeneration as shown below on the $T-s$ diagram employs a single open feedwater heater for efficiency improvement. The fluid mix with each other in an open feedwater heater. The turbine is isentropic and the input (bleed) to the feedwater heater from ... bled from the turbine as a percentage of the total mass flow rate at the inlet to the turbine at state $1$ is _______
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A circular disk of radius $r$ is confined to roll without slipping at $P$ and $Q$ as shown in the figure. If the plates have velocities as shown, the magnitude of angular velocity of the disk is $\dfrac{V}{r} \\$ $\dfrac{V}{2r} \\$ $\dfrac{2V}{3r} \\$ $\dfrac{3V}{2r}$
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For an air-standard Diesel cycle, heat addition is at constant volume and heat rejection is at constant pressure heat addition is at constant pressure and heat rejection is at constant pressure heat addition is at constant pressure and heat rejection is at constant volume heat addition is at constant volume and heat rejection is at constant volume
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Consider a flow through a nozzle, as shown in the figure below. The air flow is steady, incompressible and inviscid. The density of air is $1.23 \: kg/m^3$. The pressure difference, $(p_1-p_{\text{atm}})$ is _________ kPa (round off to $2$ decimal places)
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Air is contained in a frictionless piston-cylinder arrangement as shown in the figure. The atmosphere pressure is $100$ kPa and the initial pressure of air in the cylinder is $105$ kPa. The area of piston is $300 \: cm^2$. Heat is now added and the piston ... N/mm. Considering the air inside the cylinder as the system, the work interaction is _________ J (round off to the nearest integer)
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Moist air at $105$ kPa, $30^\circ C$ and $80\%$ relative humidity flows over a cooling coil in an insulated air-conditioning duct. Saturated air exits the duct at $100$ kPa and $15^\circ C$. The saturation pressures of water at $30^\circ C$ and $15^\circ C$ ... air is $28.94$ g/mol. The mass of water condensing out from the duct is ______ g/kg of dry air (round off to the nearest integer).
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In a steam power plant, superheated steam at $10$ MPa and $500^\circ C$, is expanded isentropically in a turbine until it becomes a saturated vapour. It is then reheated at constant pressure to $500 ^\circ C$. The steam is next expanded isentropically in another turbine until it reaches the condenser ...
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Keeping all other parameters identical, the Compression Ratio (CR) of an air standard diesel cycle is increased from $15$ to $21$. Take ratio of specific heats $=1.3$ and cut-off ratio of the cycle $r_c=2$ ... $\%$ (round off to one decimal place).
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The compressor of a gas turbine plant, operating on an ideal intercooled Brayton cycle, accomplishes an overall compression ratio of $6$ in a two-stage compression process. Intercooling is used to cool the air coming out from the first stage to the inlet temperature ... gas are constant, the intercooling pressure for minimum compressor work is __________ $kPa$ (rounded off to $2$ decimal places).
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For a Kaplan (axial flow) turbine, the outlet blade velocity diagram at a section is shown in the figure. The diameter at this section is $3\:m$.The hub and tip diameters of the blade are $2\:m$ and $4\:m$ ... $300\:rpm$. The blade outlet angle $\beta$ is ________ degrees (round off to one decimal place).
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An engine operates on the reversible cycle as shown in the figure. The work output from the engine (in (kJ/cycle) is ____ (correct to two decimal places).
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The figure shows a heat engine (HE) working between two reservoirs. The amount of heat $(Q_2)$ rejected by the heat engine is drawn by a heat pump (HP). The heat pump receives the entire work output $(W)$ of the heat engine. If temperatures, $T_1 >T_3>T_2$ ... $\text{COP}= 1 + \eta$ $\text{COP}= \eta^{-1}$ $\text{COP}= \eta^{-1} -1$
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An air standard Otto cycle has thermal efficiency of $0.5$ and the mean effective pressure of the cycle is $1000 \: kPa$. For air, assume specific heat ratio $\gamma=1.4$ and specific gas constant $R=0.287 \: kJ/kg \cdot K$. If the pressure and temperature at the ... and $300 \: K$, respectively, then the specific net work output of the cycle is _____ $kJ/kg$ (round off to two decimal places).
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As per common design practice, the three types of hydraulic turbines, in descending order of flow rate, are Kaplan, Francis, Pelton Pelton, Francis, Kaplan Francis, Kaplan, Pelton Pelton, Kaplan, Francis
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Consider an ideal vapor compression refrigeration cycle. If the throttling process is replaced by an isentropic expansion process, keeping all the other processes unchanged, which one of the following statements is true for the modified cycle? Coefficient of performance is ... of performance is the same as that of the original cycle Refrigerating effect is lower than that of the original cycle
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The rotor of a turbojet engine of an aircraft has a mass $180 \: kg$ and polar moment of inertia $10 \: kg \cdot m^2$ about the rotor axis. The rotor rotates at a constant speed of $1100 \: rad/s$ in the clockwise direction when viewed from the front of the aircraft. The aircraft while ... and the nose goes down $162.9 \: N \cdot m$ and the nose goes up $162.9 \: N \cdot m$ and the nose goes down
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A gas turbine with air as the working fluid has an isentropic efficiency of $0.70$ when operating at a pressure ratio of $3$. Now, the pressure ratio of the turbine is increased to $5$, while maintaining the same inlet conditions. Assume air as a perfect gas ... both the cases, the isentropic efficiency of the turbine at the pressure ratio of $5$ is ___________ (round off to two decimal places)
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A refrigerator operates between $120$ kPa and $800$ kPa in an ideal vapor compression cycle with $R-134a$ as the refrigerant. The refrigerant renters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is $0.2$ kg/s. Properties for $R-134a$ are as follows: The power required for the compressor in kW is $5.94$ $1.83$ $7.9$ $39.5$
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A refrigerator operates between $120$ kPa and $800$ kPa in an ideal vapor compression cycle with $R-134a$ as the refrigerant. The refrigerant renters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is $0.2$ kg/s. ... The rate at which heat is extracted, in Kj/s from the refrigerated space is $28.3$ $42.9$ $34.4$ $14.6$
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A room contains $35$ kg of dry air and $0.5$ kg of water vapor. The total pressure and temperature of air in the room are $100$ kPa and $25^{\circ}$C respectively. Given that the saturation pressure for water at $25^{\circ}$ C is $3.17$ kPa, the relative humidity of the air in the room is $67 \%$ $55 \%$ $83 \%$ $71 \%$
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Steam enters an adiabatic turbine operating at steady state with an enthalpy of $3251.0 \: kJ/kg$ and leaves as a saturated mixture at $15 \:kPa$ with quality (dryness fraction) $0.9$. The enthalpies of the saturated liquid and vapor at $15 \: kPa$ ... $6.5$ $8.9$ $9.1$ $27.0$
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At the eye tip of a centrifugal impeller, blade velocity is $200 \: m/s$ while the uniform axial velocity at the inlet is $150 \: m/s$. If the sonic velocity is $300 \: m/s$, then the inlet Mach number of the flow will be $0.75$ $0.66$ $0.90$ $0.83$
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A necessary percaution in selection of pumps for parallel operations is that H-Q characteristics of both should be identical Both pumps should be centrifugal type Both pumps should be identical' There should not be change from positive to negative slope in H-Q curve
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The correct sequence of the centrifugal pump components through which the fluid flows is Impeller, Suction pipe, Foot valve and strainer, Delivery pipe Foot valve and strainer, Suction pipe, Impeller, Delivery pipe Impeller, Suction pipe, Delivery pipe, Foot valve and strainer Suction pipe, Delivery pipe, Impeller, Foot valve and strainer
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A vehicle powered by a spark ignition engine follows air standard Otto cycle ($\gamma =1.4$). The engine generates $70$ kW while consuming $10.3$ kg/hr of fuel. The calorific value of the fuel is $44,000 \: kJ/kg$. The compression ratio is _________ (correct to two decimal places.
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A test is conducted on a one-fifth scale model of a Francis turbine under a head of $2 \: m$ and volumetric flow rate of $1 \: m^3/s$ at $450 \: rpm$. Take the water density and the acceleration due to gravity as $10^3 \: kg/m^3$ ... and prototype turbines. The power (in MW) of a full sized turbine while working under a head of $30 \: m$ is _______ (correct to two decimal places)
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Air is held inside a non-insulated cylinder using a piston (mass $M=25 \: kg$ and area $A=100 \: cm^2$) and stoppers (of negligible area), as shown in the figure. The initial pressure $P_i$ and temperature $T_i$ of air inside the cylinder are $200 \: kPa$ ... temperature of the air inside the cylinder ($^{\circ}C$) at which the piston will begin to move is ______ (correct to two decimal places).
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Select the correct statement for $50\%$ reaction stage in a steam turbine. The rotor blade is symmetric The stator blade is symmetric The absolute inlet flow angle is equal to absolute exit flow angle The absolute exit flow angle is equal to inlet angle of rotor blade
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An engine working on air standard Otto cycle is supplied with air at $0.1 MPa$ and $35^{\circ} \: C$. The compression ratio is $8$. The heat supplied is $500 \: kJ/kg \: K$. The maximum temperature (in $K$) of the cycle is _______ (correct to one decimal place)
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Steam flows through a nozzle at a mess flow rate of $m=0.1 \: kg/s$ with a heat loss of $5 \: kW$. The enthalpies at inlet and exit are $2500 \: kJ/kg$ and $2350 \: kJ/kg$, respectively. Assuming negligible velocity in inlet ($C_1 \approx 0$), the velocity ($C_2$) of steam (in $m/s$) at the nozzle exit is _____ (correct to two decimal places).
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For a Pelton wheel with a given water jet velocity, the maximum output power from the Pelton wheel is obtained when the ratio of the bucket speed to the water jet speed is _____ (correct to two decimal places)
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An ideal gas undergoes a process from state $1 \: (T_1 = 300\: K, \: p_1 = 100 \: kPa)$ to state $2 \: (T_2 = 600 \; K, \: p_2 = 500 \: kPa)$. The specific heats of the ideal gas are: $C_p = 1 \: kJ/kg-K$ and $C_v = 0.7 \: kJ/kg-K$. The change in specific entropy of the ideal gas from state $1$ to state $2$ (in $kJ/kg-K$) is ______ (correct to two decimal places).
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In the Rankine cycle for a steam power plant, the turbine entry and exit enthalpies are $2803 \: kJ/kg$ and $1800 \: kJ/kg$, respectively. The enthalpies of water at pump entry and exit are $121 \: kJ/kg$ and $124 \: kJ/kg$, respectively. The specific steam consumption (in $kg/kW.h$) of the cycle is _________.
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A calorically perfect gas (specific heat at constant pressure $1000 \: J/kg .K$) enters and leaves a gas turbine with the same velocity. The temperatures of the gas at turbine entry and exit are $1100 \: K$and $400 \: K$, respectively. The power produced is $4.6\: MW$ and heat ... the turbine casing. The mass flow rate of the gas (in $kg/s$) through the turbine is $6.14$ $7.00$ $7.50$ $8.00$
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Which one of the following statements is TRUE? Both Pelton and Francis turbines are impulse turbines. Francis turbine is a reaction turbine but Kaplan turbine is an impulse turbine. Francis turbine is an axial-flow reaction turbine. Kaplan turbine is an axial-flow reaction turbine.
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Air contains $79\%$ $N_{2}$ and $21\%$ $O_{2}$ on a molar basis. Methane $(CH_{4})$ is burned with $50\%$ excess air than required stoichiometrically. Assuming complete combustion of methane, the molar percentage of $N_{2}$ in the products is _______.
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Moist air is treated as an ideal gas mixture of water vapour and dry air (molecular weight of air$= 28.84$ and molecular weight of water $=18$). At a location, the total pressure is $100$ kPa, the temperature is $30^{\circ}$ C and the relative humidity is $55\%$. ... the saturation pressure of water at $30^{\circ} C$ is $4246$ Pa, the mass of water vapour per kg of dry air is _________ grams.
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The pressure ratio across a gas turbine (for air, specific heat at constant pressure, $c_{p}=1040 J/kg.K$ and ratio of specific heats, $\gamma=1.4$) is $10$. If the inlet temperature to the turbine is $1200$ K and the isentropic efficiency is $0.9$, the gas temperature at turbine exit is ________ $K$
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One kg of an ideal gas (gas constant, $R= 400 J/kg.K$; specific heat at constant volume, $c_{v}=1000 J/kg.K$) at $1$ bar, and $300$ K is contained in a sealed rigid cylinder. During an adiabatic process, $100$ kJ of work is done on the system by a stirrer. The increase in entropy of the system is _______ $J/K$.
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In the vapour compression cycle shown in the figure, the evaporating and condensing temperatures are $260 \: K$ and $310 \: K$, respectively. The compressor takes in liquid-vapour mixture (state $1$) and isentropically compresses it to a dry saturated vapour condition (state $2$). ... is $1054 \: kJ/kg$. The difference between the enthalpies at state points $1$ and $0$ (in $kJ/kg$) is ____________
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