The condition of stable equilibrium fora floating body is:
ISRO Scientist or Engineer Refrigeration & Air-Conditioning 2014
For the following questions answer them individually
The thickness of turbulent boundary layer at a distance x from the leading edge overa flat plate vvaries as
The diameters of a pipe at the sections 1 and 2 are 10 cm and 15 cm respectively. Velocity of water flowing through the pipe at section 1 is 5 m/s. velocity at section 2 in m/s and discharge in cmm is
The velocity distribution for flow over flat plate is given $$u = \frac{3}{4}y - y^2$$ in which u is the velocity in m/s at a distance y meter above the plate. Shear stress at $$y = 0.15 m$$ is (Take $$\mu$$ for fluid = 8.5 poise)
A gas weighs 16 N/m$$^3$$ at 288 K and at an adiabatic pressure of 25 N/cm$$^2$$. Its gas constant is
A pipe line AB of diameter 30 cm and of length 400 m carries water at the rate of 50 liters/sec. The flow takes place from A to B where point B is 30 meters above A. Pressure
at B is 2 ksc. Pressure at Ais (Take f = 0:008)
A nozzle is fitted at the end of a pipe of length 300m and of diameter 10 cm for transmitting water. What is the diameter of the nozzle considering maximum transmission
of powerthrough the nozzle (f = 0.009)
A turbine develops 500 kW under a head of 100 meters at 200 RPM.Its normal speed and powerunder a head of 81 meters
Number of degrees of freedom in a Ball and socket joint:
Two inelastic spheres of masses 10 kg each move with velocities of 15m/s and 5m/s respectively in the same direction. The loss in kinetic energy when theycollide
In order to have maximum powerfrom a Pelton turbine, the bucket speed must be
The alloying element mainly used to improve the endurancestrength ofsteel materials is
The percentage improvement in powercapacity of a flat belt drive, when the wrap angle at the driving pulley is increased from $$150^\circ$$ to $$210^\circ$$ by an idler arrangement fora friction coefficient of 0.3 is
In an interchangeable assembly, shaft of size $$25.000_{-0.01}^{+0.04}$$ mm. mates with a hole of size $$25.000_{-0.02}^{+0.03}$$ mm. Maximum interference in micronsin the assembly is
A column has a rectangular cross section of 10 $$\times$$ 20 mm and a length of 1m. The slenderness ratio of the columnis close to
A thin cylinder of inner radius 500 mm and thickness 10mm is subjected to an internal pressure of 5 MPa. The average hoop stress in MPa is
A circular disk of uniform thickness 20 mm, radius 200 mm and mass 20 kg is used as flywheel. If it rotates at 600 rpm, kinetic energy of flywheel in Joule is
A vibration system consists of a mass of 175 kg, a spring stiffness 700 N/cm and damper with a damping coefficient of 7 N cm$$^{-1}$$ sec. Damping factor of the system is
Two cutting tools are being compared for a machining operation. The tool life equations are Carbide tool : $$VT^{1.6} = 3000$$; HSS tool : $$VT^{0.6} = 200$$, where V is the cutting speed in m/min and T is tool life in min. The carbide tool will provide higher tool life, if the cutting speed in m/min exceeds
The diameter of suction side of a reciprocating compressor compared to its delivery side is
Two crossed helical gears are used for speed reduction. Gear A haspitch circle diameter in the plane of rotation 80mm and helix angle 30 deg; Gear B . Gear A haspitch circle
diameter in the plane of rotation 120mm andhelix angle 22.5 deg; If the input speed is 1440 RPM, then output speed in RPM is
The moisture in a refrigerant is removedby :
In an arc welding process, the voltage and current are 25 V and 300 A respectively. The are heat transfer efficiency is 0.85 and welding speed is 8mm/sec. the net heat input (in J/mm) is:
Hardness of steel greatly improves with
For a perfect gas
If a mass of moist air in an airtight vessel is heated to a higher temperature, then
Threaded bolts of A and B of same material and length are subjected to identical tensile load. If the elastic strain energy stored in bolt A is 4 times that of bolt B and the mean diameter of bolt A is 12mm, then mean diameterof bolt B is
In a condenser of a power plant, the steam condenses at a temperature of 333 K. The cooling water enters at 303 K and leaves at 318 K. The logarithmic mean temperature
difference (LMTD)of the condenser is
The shear strength of a sheet metal is 300 Mpa. The blanking force required to produce a blank of 100 mm diameter from a 1.5mm thick sheet is
A heat engine is supplied heat at the rate of 1700 kJ/min and gives an output of 9 kW. Thermalefficiency and heat rejection in kW of heat engine is
When we have combinedfree and forced convection, Gr/Re$$^2$$ is
A refrigerator and heat pump operate between the same temperature limits. COP of refrigerator is 4, COP of heat pump would be
A carnot refrigerator requires 1.25 kW perton ofrefrigeration to maintain a temperature of 233 K.Its higher operating temperature of the cycle
The work input to air compressor is minimum if the compression law followed is
Operating pressures of the refrigerants at the evaporator in the ascending order for any application are
For vapour compression system using R717 the material of pipe is
Air at DBT of 308 K and DPTof 293 K passes through a cooling coil which is maintained at 298 K. The process would be
Room sensible heat loss is 30000kJ/min and room latent heat loss is 20000 kJ/min. Sensible heat factor is
Domestic refrigerator working on vapour compression cycle uses the following type of expansion device
An incompressible fluid flows overa flat plate and its boundary layer thickness at certain location is 1mm for Reynolds Numberof 1000. If the velocity is increased by a factorof 4, then the boundarylayer thickness at that location in mm will be
A room contains 35 kg of dry air and 0.5 kg of water vapour. Total pressure and temperature in the room is 100kPa and 298 K.Saturation pressure of water at 298 is 3.17 kPa. Relative humidity of air in that room is
An ideal brayton cycle operating between the pressure limits of 1 bar and 6 bar, has minimum and maximum temperature of 300 and 1500 K. Ratio of specific heat of working
fluid is 1.4. Approximate final temperatures in Kelvin at the end of compression and expansion respectively are
Condition of perfect Vacuumis attained at temperature of
Two identical ball bearings P and Q are operating at loads 15 KN and 45 KN respectively. The ratio of life of bearing P to Q is
If a certain amount of dry ice is mixed with same amount of waterat 80°C, then the final temperature of the mixture is
The leaks in a refrigeration system using Freon is detected using
Presence of moisture in the refrigerant affects the working of
In SI unit, one ton of refrigeration is
On the pressure — enthalpy diagram, condensation and de-superheating is represented by a horizontal line because the process
Generation of heating at one junction and cooling at other by passing direct current through a pair of dissimilar materials is
Power consumption of centrifugal fans varies with speed (N) and diameter (D) as
Sol-air temperature for a wall of absorptivity 0.9, exposed to ambient temperature of $$35^\circ C$$, solar radiation of 260 W/sqm, outside heat transfer coefficient 23 W/sqm K is
The recovery factor in flow of gases is a function of
Adiabatic wall temperature is
A composite slab has two layers of different materials having thermal conductivities k and 2k. If each layer has the same thickness, the equivalent thermal conductivity of the slab is
Whena liquid flows through a tube with subcooled or saturated boiling the processis known as
For filmwise condensation, the heat transfer coefficient will be equal whether the tube is horizontal or vertical, when the ratio of length to diameter is
Insulated tip temperature of a rectangular longitudinalfin will be equal to
The characteristic length computing Grashof number in the case of a horizontal cylinder is
In liquid metal heat transfer for a fluid flowing through a tube, Nusselt number is a function of
Absorptivity of the grey body
Gases have poor
Intensity of solar radiation in KW/sqm is about
Match the following:
In $$MLT \theta$$ system, the dimension of thermal conductivity is
For infinite parallel planes with emissivities 0.4 and 0.2, the interchange view factor for a radiation from surface 1 to surface 2 is about
A chromel — alumel thermocouple of diameter 0.7mm is used to measure the temperature of a gas stream for which h= 600 W/sqm K. Acceptable reading of the temperature can be
taken after (specific heat = 400 J/kg K, Density = 8600 kg/cum)
On a hot summerday, surface of the concrete highway may reach 328 K. Suppose a stream of wateris directed on the highwayso that the surface is suddenly lowered to 308 K. Time
taken in hours to cool the concrete to 318 K to a depth of 5 cm below the surface is:(Thermal diffusivity = 1.77 E-03 m$$^2$$/h)
Hot surface at temperature 400 K having emissivity of 0.5 dissipates heat by radiation into a surrounding of 375 K.Its radiation heat transfer coefficient (W/sqm K) is
Hot steel sphere of diameter 40mm is immersed in oil. If the heat transfer coefficient between the sphereand oil is 300 W/sqm K , then Biot Number is:(Take $$k_{steel}$$ = 50 W/m K and $$k_{oil}$$ = 0.2 W/m K)
A metallic surface is maintained at 1000 K, the wavelength at which maximum spectral intensity occurs
Air at 293 is flowing with velocity of 3m/s over a heated flat square plate. Plate is 0.3 m wide and is maintained at 330 K. Average heat loss from the plate due to convection is (Take $$v = 16.768E-6 m^2/s, Pr = 0.7, k = 0.027 W/m K$$)
Twofluids A and B exchange heatin counterflow heat exchanger. Fluid A enters at 700 K and fluid B enters at 300 K. Mass flow rate of A & B is 1 kg/s. Specific heat of fluid A and B is 1000 J/kg K and 4000 J/kg K. Net Effectiveness of heat exchange is 75 %. Exit temperature of Fluid B is
If the following equations are consistent, then value of k is
4x - 3y + 1 = 0
kx - 8y + 10 = 0
x + y - 5 = 0
If $$\omega$$ and $$\omega^2$$ are cube roots of unity, then $$(2 - \omega + 2 \omega^2)(2 + 2 \omega - \omega^2)$$ is
Area of the ellipse $$\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$$
find $$\lim_{x \rightarrow 0} \frac{1 - \cos x}{x^2}$$
Equation of the plane parallel to the x axis and passes through the point (4,6,2) and (4, -5, 3)
$$\overline{a}$$ and $$\overline{b}$$ are vectors such that $$2 \overline{a} - 4 \overline{b}$$ and $$10 \overline{a} + 8 \overline{b}$$ are perpendicular to each other. Angle between the vectors $$\overline{a}$$ and $$\overline{b}$$ is
