Engineer's Zone

Moment of momentum equation is derived from moment of momentum principle, which states that the resulting torque acting on a rotating fluid is equal to the rate of change of moment of momentum.

Moment of momentum per second = rQ x V x r

Where r = density of fluid

Q = rate of flow of fluid

V = velocity of fluid

r = radius of curvature

The equation based on the principle of conservation of mass is called continuity equation.

r₁A₁V₁ = r₂A₂V₂

Where V = Average velocity

r = Density

A = Area of pipe

If the fluid is incompressible, then r₁=r₂ and continuity equation reduces to A₁V₁ = A₂V₂

• When heat transfer takes place through electro magnetic waves between two bodies isolated together in a vacuum, the phenomenon is called radiation
• The rate at which the energy is radiated by a black body at temperature T is given by Stefan-Boltzman law

Q = σ A T⁴

Where

Q = rate of energy radiation, watt

A = surface area radiating heat, m²

σ = Stefan-Boltzmann constant, 5.67x10^-8 W/m²k⁴

Fourier’s law of heat conduction states that the rate of heat flux is linearly proportional to the temperature gradient.

q α dt/dx

q = -k (dt/dx)

k = constant of proportionality which is the property of the material through which heat is being conducted and is known as thermal conductivity.

Water chillers are used in a variety of air conditioning and process cooling applications. They are used to make cold water that can be transported throughout a facility using pumps and pipes. This cold water can be passed through the tubes of coils in order to cool the air in an air conditioning application or it can provide cooling for a manufacturing or industrial process.
Systems that employ water chillers are commonly called chilled water
systems.

There are several types of water chillers that are differentiated by the
refrigeration cycle they use or the type of compressor.

Absorption water chillers make use of the absorption refrigeration cycle and donot have a mechanical compressor involved in the refrigeration cycle. Absorption water chillers are the subject of a separate clinic.

Water chillers using the vapor-compression refrigeration cycle vary by the type of compressor used. Reciprocating and scroll compressors are typically used in smaller chillers. Helical-rotary (or screw) compressors are typically used in medium-sized chillers. Centrifugal compressors are typically used in larger chillers.

Source : Trane Guide