Mechanical Engineering Basic Terms - 2

Stiffness:

Load per unit deflection. The amount of load required to resist the deflection.

Specific Weight:

Weight per unit volume of the fluid.

Specific Volume:

Volume per unit mass of the fluid.

Specific Gravity:

It is the ratio of specific weight of required substance to specific weight of pure water at 4 degree centigrade temperature.

Specific heat:

The amount of heat required to increase 1 unit temperature of 1 unit mass.

Viscosity:

Dynamic Viscosity:

The amount of resistance of one layer of fluid over other layer of fluid.

Kinematic Viscosity:

It is the ratio of dynamic viscosity to density.

Buoyancy:

When a body is immersed in a liquid, it is lifted up by a force equal to weight of liquid displaced by the body. The tendency of liquid to lift up an immersed body is buoyancy. The upward thrust of liquid to lift up the body is called buoyancy force.

Bernoulli's Equation:
P/γ +V²/2g +Z = Constant

Where, P = pressure,V = velocity,Z = Datumn Head

Devices for fluid:

Venturimeter:

It measures discharge of fluid.

Notches :

It measures discharge of fluid.

Orifice meter:

It measures discharge of fluid.

Pitot tube :

It measures velocity of fluid.

Mach Number:

It is the ratio of the velocity of fluid to the velocity of sound.
M=1 ----------------- Sonic flow
M> (1-6) ----------- Super-Sonic flow
M>6 ---------------- Hyper-Sonic flow

Fluid discharge/Fluid flow:

Quantity of fluid flowing per second.

(through a section of pipe/ through a section of channel)

Q=AV

where, V= velocity of fluid,A= cross-sectional area of pipe/channel
Note: 1m³ = 1000 L1 cusec = 1 ft³/sec1 ft = 0.3048 m

Hydraulic Machine:

Turbine,Pump,Compressor etc.

Draft tube:

It attaches with reaction turbine . Its function is to reduce energy loss from reaction turbine & it also reduce pressure at outlet which is must blow the atmospheric pressure.

Themodynamics Law:

Zeroth Law
First Law of Thermodynamic
Second Law of thermodynamic

Zeroth Law:

If two body are in thermal equilibrium with a third body then these two body are also in thermal equilibrium with each other.

First Law of Thermodynamics:

In a closed system, work deliver to the surrounding is directly proportonal to the heat taken from the surrounding.And also, In a closed system, work done on a system is directly proportonal to the heat deliver to the surrounding.

Second Law of Thermodynamics:

It is impossible to make a system or an engine which can change 100 percent input energy to 100 percent output.

Entropy:

It is a thermodynamic property.

ds = dq/T

where, ds = change of entropy, dq = change of heat, T = Temperature.

In adiabatic process, entropy can not change. Actually,lacking or mal-adroitness of tranfering energy of a system is entropy.