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engineering
introduction mechanical engineering
Basic Mechanical Engineering 2nd Edition PRAVIN KUMAR - Solutions
\(80 \mathrm{~m}^{3}\) of air per minute at \(32^{\circ} \mathrm{C}\) and \(70 \%\) is cooled to \(24^{\circ} \mathrm{C}\) DBT (sensible cooling). Find the heat removed from the air, relative humidity of cooled air, WBT of the cooled air (Take air pressure \(=1\) bar).
A Carnot engine has an efficiency of \(80 \%\), If the cycle is reversed in direction and made to operate as a refrigerator , its COP will be:(a) 0.25(b) 0.5(c) 0.75(d) 1.25
Write advantages and disadvantages of Vapor Compression Cycle over Air Refrigeration Cycle.
A perfect reversed heat engine is used for making ice at \(-5^{\circ} \mathrm{C}\) from water available at \(25^{\circ} \mathrm{C}\). The temperature of the freezing mixture is \(-10^{\circ} \mathrm{C}\). Calculate the quantity of ice formed per kwh. For ice specific heat \(=2.1 \mathrm{~kJ} /
A condenser of a refrigeration system rejects heat at a rate of \(120 \mathrm{kw}\), while its compressor consumes a power of \(30 \mathrm{kw}\). The coefficient of performance of the system would be:(a) 2(b) 3(c) 4(d) 5
Explain the working of vapor absorption cycle.
The operating temperature of cold storage is \(280^{\circ}\) \(\mathrm{k}\) and the heat leakage from the surroundings is \(35 \mathrm{kw}\) for the ambient temperature of \(310^{\circ} \mathrm{k}\). If the actual COP of the refrigeration plant is onefourth of an ideal plant working between the
What do you mean by sensible heating and sensible cooling?
A Carnot heat pump for domestic heating works between a cold system ( the contents of refrigerator cabinet) at \(0^{\circ} \mathrm{C}\) and the water in the radiator system at \(80^{\circ} \mathrm{C}\). The coefficient of performance of this heat pump would be about:(a) 1.4(b) 3.4(c) 4.4(d) 6.2
What do you mean by latent heating and latent cooling?
A heat pump working on a reversed Carnot cycle has a COP of 5 . If it is made to work as a refrigerator taking \(1 \mathrm{KW}\) of work input, the refrigerating effect will be:(a) \(1 \mathrm{KW}\)(b) \(2 \mathrm{KW}\)(c) \(3 \mathrm{KW}\)(d) \(4 \mathrm{KW}\)
What are the human comfort conditions?
Write notes on bypass factor and sensible heat factor.
The capacity of refrigerating \(\mathrm{m} / \mathrm{c}\) is expressed as:(a) Inside volume of cabinet(b) Lowest temperature attained(c) Gross weight of \(\mathrm{m} / \mathrm{c}\) in tons(d) Rate of abstraction of heat from the space being cooled
One TOR implies that the \(\mathrm{m} / \mathrm{c}\) has a refrigerating effect ( capacity of heat extraction from the system being cooled) equal to:(a) \(50 \mathrm{kCal} / \mathrm{sec}\)(b) \(50 \mathrm{kCal} / \mathrm{min}\)(c) \(50 \mathrm{kCal} / \mathrm{hr}\)(d) \(50 \mathrm{kCal} /\) day
What are the various types of refrigerators have been in the application? Explain them.
One TOR is equivalent to:(a) \(1 \mathrm{KW}\)(b) \(2.5 \mathrm{KW}\)(c) \(3.5 \mathrm{KW}\)(d) \(5 \mathrm{KW}\)
Explain the various refrigerants used in refrigeration and air conditioning.
The domestic refrigerator has a refrigerating load of the order of:(a) Less than 0.25 ton(b) Between 0.5 and 1 ton(c) More than 1 ton(d) More than 5 ton
Write short notes on Window Air Conditioner and Split Air Conditioner.
The refrigerating capacity of 165 domestic refrigerators is approximately equal to:(a) 0.05 ton(b) 0.1 ton(c) 2 ton(d) 5 ton
Differentiate between refrigeration and air conditioning, vapor compression refrigeration and vapor absorption refrigeration. With a neat sketch, explain the working of a room air conditioner.
Round the clock cooling of an apartment having a load of \(300 \mathrm{MJ} /\) day requires an air conditioning plant of capacity about:(a) 1 ton(b) 5 ton(c) 10 tons(d) 25 tons
Define the following: (i) COP, (ii) unit of refrigeration, and (iii) air conditioning.
The refrigerating system of passenger air craft works on reversed:(a) Brayton cycle(b) Atkinson cycle(c) Ericsson cycle(d) Carnot cycle
Explain with neat sketch the principle and construction of vapor absorption refrigeration system.
Explain with a neat sketch the working of a vapor compression refrigerator. Also draw p-h and T-s diagram for the same.
The Bell-Coleman refrigeration cycle uses as working fluid.(a) Hydrogen(b) Carbon dioxide(c) Air(d) Any inert gas
A Bell-Coleman cycle is a reversed:(a) Brayton cycle(b) Atkinson cycle(c) Ericsson cycle(d) Carnot cycle
What is refrigeration? What is refrigeration effect? Explain window air conditioner with neat sketch.
Define air-conditioning. Classify the air conditioning system in detail.
Define:(i) Sensible heat(ii) Latent heat(iii) Dryness Fraction(iv) Enthalpy of evaporation
What should be the properties of common refrigerants?
The dynamic viscosity of lubricating oil used between shaft and sleeve is 12 poise. The diameter of the shaft, which rotates at \(240 \mathrm{rpm}\), is 0.5 \(\mathrm{m}\). The sleeve length is \(120 \mathrm{~mm}\). Calculate the power lost if the thickness of oil film is \(2.5 \mathrm{~mm}\).
Define air conditioning. State the basic component of air conditioning systems.
Name any six properties of refrigerants.
Discuss about psychrometry and their properties?
Sketch and explain split air conditioner?
Explain the working of domestic refrigeration system with a neat sketch?
Distinguish between a heat engine, a heat pump, and a refrigerator.
With a neat sketch of a room air-conditioner, explain its working principle.
Fluid is a substance that:(a) Cannot be subjected to shear force(b) Always expands until it fills any container(c) Has the same shear stress at a point regardless of its motion(d) Cannot remain at rest under action of any shear force
What do you understand by fluid mechanics?How does it differ from mechanics of solid or mechanics of the rigid body?
A fluid is said to be ideal, if it is:(a) Incompressible(b) Inviscous(c) Viscous and incompressible(d) Inviscous and incompressible
Classify the fluids based on their properties.
The surface tension of water in contact with air at ambient temperature is \(0.12 \mathrm{~N} / \mathrm{m}\). The pressure inside the water droplet is \(0.02 \mathrm{~N} / \mathrm{cm}^{2}\) greater than the outside pressure. Calculate the diameter of the water droplet.
The volumetric change of the fluid caused by a resistance is known as:(a) Volumetric strain(b) Compressibility(c) Adhesion(d) Cohesion
Derive the Bernoulli’s equation.
Find the surface tension in a soap bubble of 60 \(\mathrm{mm}\) diameter when the inside pressure is \(5 \mathrm{~N} / \mathrm{m}^{2}\) above atmospheric pressure.
Surface tension:(a) Acts in the plane of the interface normal to any line in the surface(b) Is also known as capillarity(c) Is a function of the curvature of the interface(d) Decrease with fall in temperature
Derive the rise and fall of capillary action in a tube.
Calculate the capillary rise in a glass tube of diameter \(1.8 \mathrm{~mm}\) when immersed vertically in: (i) water and (ii) mercury. Assume surface tension for water as 0.07 and for mercury as 0.5 in contact with air. The specific gravity for mercury is 13.6 and angle of contact is
The stress-strain relation of the Newtonian fluid is:(a) Linear(b) Parabolic(c) Hyperbolic(d) None of these
Derive an equation for pressure on a submerged body in a fluid.
The water is flowing through a pipe having diameters \(32 \mathrm{~cm}\) and \(18 \mathrm{~cm}\) at two sections 1 and 2, respectively. The rate of flow through the pipe is \(100 \mathrm{~L} / \mathrm{sec}\). Section 1 is \(8 \mathrm{~m}\) above the datum and section 2 is \(8 \mathrm{~m}\) above
Unit of surface tension is:(a) Energy per unit area(b) Force per unit length(c) Both(d) None of these
What do you mean by a hydraulic turbine? How do you classify the hydraulic turbines?
A penstock supplies water to Pelton turbine with a head of \(80 \mathrm{~m}\). One-third of head is lost in penstock due to friction. The flow rate of water from the nozzle is \(2.5 \mathrm{~m}^{3} / \mathrm{sec}\). The deflection angle of the jet is \(165^{\circ}\). Speed ratio,
Capillary action is due to the:(a) Surface tension(b) Cohesion of the liquid(c) Adhesion of the liquid molecules and the molecules on the surface of a solid(d) All of the above
Explain the working of Pelton turbine with a neat sketch.
A Pelton wheel is to be designed with following specifications:Shaft power \(=10,000 \mathrm{~kW}\), Head \(=500 \mathrm{~m}\), Speed \(=500 \mathrm{rpm}\), Overall efficiency \(=85 \%\), jet diameter is one-tenth of wheel diameter. Determine: (i) the wheel diameter, (ii) the number of jets
The rise or fall of head ' \(h\) ' in a capillary tube of diameter ' \(\mathrm{d}\) ' and liquid surface tension ' \(\sigma\) ' and specific weight ' \(w\) ' is equal to:(a) \(\frac{4 \sigma}{w d}\)(b) \(\frac{4 d \sigma}{w}\)(c) \(\frac{4 w d}{\sigma}\)(d) None of these
Discuss the governing of Pelton turbine.
A Francis turbine working under a head of 10 \(\mathrm{m}\). The overall efficiency is \(75 \%\) and power required to produce \(180 \mathrm{~kW}\). The peripheral and radial velocities at inlet are \(0.3 \sqrt{2 g H}\) and 0.96 \(\sqrt{2 g H}\), respectively. The wheel runs at \(200 \mathrm{rpm}\)
Cavitation will begin when:(a) The pressure at any location reaches an absolute pressure equal to the saturated vapor pressure of the liquid(b) Pressure becomes more than the critical pressure(c) Flow is increased(d) Pressure is increased
Derive the expression for work done and mechanical efficiency of Pelton turbines.
An inward flow reaction turbine rotates at 420 rpm. The wheel vanes are radial at the inlet and the inner diameter of the wheel is one-third of the outer diameter. The constant velocity of flow in the wheel is \(2.8 \mathrm{~m} / \mathrm{sec}\). Water enters the wheel at an angle of 150 to the
Bernoulli's theorem deals with the conservation of:(a) Mass(b) Force(c) Momentum(d) Energy
How does a hydraulic turbine differ from the hydraulic pump?
A Kaplan turbine is working under a head of \(18 \mathrm{~m}\). The hub diameter is 0.25 times the runner diameter. The rpm of the turbine is 550. Runner angle at the outlet is \(15^{\circ}\) and flow ratio is 0.6 . Calculate: (i) diameter of runner and (ii) discharge rate of water.
Euler's equation in the differential form for motion of liquids is given by:(a) \(\frac{d p}{ho}-g d z+v d v=0\)(b) \(\frac{d p}{ho}+g d z+v d v=0\)(c) \(\frac{d p}{ho}-g d z-v d v=0\)(d) \(\frac{d p}{ho}+g d z-v d v=0\)
What are the different types of the efficiency of a turbine? Define each.
A Kaplan turbine is designed to develop 8,000 \(\mathrm{kW}\) shaft power. The head available is \(12 \mathrm{~m}\). Assuming speed ratio as 2.1, flow ratio as 0.6, overall efficiency as \(80 \%\), and diameter of the boss as one-third of the diameter of runner. Find the diameter of runner and its
A fluid which obeys \(\mu=\frac{\tau}{d u / d y}\) :(a) Real fluid(b) Perfect fluid(c) Newtonian fluid(d) None of these
Draw inlet and outlet velocity triangle for Pelton turbine and find expression for hydraulic efficiency.
A conical draft tube having inlet and outlet diameters \(2.5 \mathrm{~m}\) and \(3.0 \mathrm{~m}\) discharges water at the outlet with a velocity of \(5 \mathrm{~m} / \mathrm{sec}\). The total length of the draft tube is \(10 \mathrm{~m}\) out of which \(3 \mathrm{~m}\) of the length of the draft
The speed of turbine and discharge through turbine are proportional to:(a) Head, \(\mathrm{H}\)(b) \(\sqrt{\mathrm{H}}\)(c) \(\mathrm{H}^{2}\)(d) \(\mathrm{H}^{3 / 2}\)
A centrifugal pump running at \(2,000 \mathrm{rpm}\) has internal and external impeller diameter of 250 \(\mathrm{mm}\) and \(350 \mathrm{~mm}\), respectively. The vane angles of the impeller at inlet and outlet are \(25^{\circ}\) and \(30^{\circ}\), respectively. If water enters the impeller
Establish a relationship between jet velocity and bucket velocity for maximum efficiency of Pelton turbine?
Specific speed of a turbine depends on:(a) Speed, power, and discharge(b) Discharge and power(c) Speed and head(d) Speed, power, and head
An impulse turbine:(a) Operates submerged(b) Requires draft tube(c) Is nor exposed to atmosphere(d) Operates by initial complete conversion to kinetic energy
What is the basis of turbine selection at a particular place?
A centrifugal pump having an internal and external diameter of impeller \(150 \mathrm{~mm}\) and \(450 \mathrm{~mm}\), respectively, is running at \(1,000 \mathrm{rpm}\). It has a constant velocity of flow of \(5 \mathrm{~m} / \mathrm{sec}\) and discharges through the pump is \(0.04 \mathrm{~m}^{3}
Define velocity coefficient, speed ratio, flow ratio, and jet ratio.
Following data of a centrifugal pump are given as: Diameter at inlet \(=0.4 \mathrm{~m}\); Diameter at outlet \(=1.0 \mathrm{~m} ;\) Speed \(=400 \mathrm{rpm}\); Flow rate \(=2000\) liters \(/ \mathrm{sec}\); Vane exit angle \(=30^{\circ}\); Velocity of flow \(=3 \mathrm{~m} / \mathrm{sec} ;\) head
A Pelton wheel is:(a) Tangential flow turbine(b) Axial flow turbine(c) Radial flow turbine(d) Mixed flow turbine
What are the ranges of specific speed and head of Pelton, Francis, and Kaplan turbines?
A double acting reciprocating pump has a piston of \(400 \mathrm{~mm}\) diameter and piston rod of \(40 \mathrm{~mm}\) diameter. Stroke length is \(300 \mathrm{~mm}\) and speed is \(60 \mathrm{rpm}\). The suction and discharge heads are \(8 \mathrm{~m}\) and \(18 \mathrm{~m}\), respectively.
Pelton wheels are used for minimum heads of:(a) \(20 \mathrm{~m}\)(b) \(100 \mathrm{~m}\)(c) \(125 \mathrm{~m}\)(d) \(180 \mathrm{~m}\)
What is a draft tube? Why is it used in a reaction turbine? Describe with a neat sketch.
A single acting reciprocating pump running at 50 rpm delivers \(0.10 \mathrm{~m}^{3} / \mathrm{sec}\) of water. The diameter of the piston is \(600 \mathrm{~mm}\) and the stroke length is \(500 \mathrm{~mm}\). Determine: (i) the theoretical discharge, (ii) percentage slip, and (iii) coefficient of
The ratio of width of bucket for a Pelton wheel to the diameter of jet is of the order of:(a) 15(b) 14(c) 13(d) 12
What is the centrifugal pump? How is it different from Francis turbine?
Impulse turbine is used for:(a) Low head(c) Medium head(b) High head(d) High flow
Explain the working of a centrifugal pump with a neat sketch.
If \(\alpha\) is the angle of blade tip at outlet, then maximum hydraulic efficiency of an impulse turbine is:(a) \(\frac{1+\cos \alpha}{2}\)(b) \(\frac{1-\cos \alpha}{2}\)(c) \(\frac{1+\tan \alpha}{2}\)(d) \(\frac{1-\tan \alpha}{2}\)
Differentiate between the volute and vortex casing of a centrifugal pump.
Francis turbine is best suited for:(a) Medium head application (24 to \(180 \mathrm{~m}\) )(b) Low head installation (less than \(30 \mathrm{~m}\) )(c) High head installation (more than \(180 \mathrm{~m}\) )(d) None of these
Explain different types of the efficiency of the centrifugal pump.
Francis, Kaplan and propeller turbines fall under the category of:(a) Impulse turbine(b) Reaction turbine(c) Axial-flow turbine(d) Mixed flow turbine
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