Presentation On

Applied Thermal & Hydraulic Engineering

Submitted by:Gohel Vishal (140123109003) / Electrical Engg. / B-3

Submitted To:Aditya singh

(2140907)

GANDHINAGAR INSTITUTE OF TECHNOLOGY

Basic of conduction

Conduction through a slab

Conduction of heat transfer through Hollow Cylinder

FLOW OF PRESETATION

BASIC OF CONDUCTION

In the simplest of terms, the discipline of heat transfer is concerned with only two things

1. Temperature – Temperature represents the amount of thermal energy

available2. Flow of heat

– whereas heat flow represents the movement of thermal energy from place to place.

On a microscopic scale, thermal energy is related to the kinetic energy of molecules.

The greater a material's temperature, the greater the thermal agitation of its constituent molecules

BASIC OF CONDUCTION

Heat Transfer MechanismsConduction

– Regions with greater molecular kinetic energy will pass their thermal energy to regions with less molecular energy through direct molecular collisions, a process known as conduction

ConvectionConvection is the movement of a physical quantity (for

example heat) because of the movement of the matter.

• Radiation• All materials radiate thermal energy in amounts

determined by their temperature, where the energy is carried by photons of light in the infrared and visible portions of the electromagnetic spectrum.

• When temperatures are uniform, the radioactive flux between objects is in equilibrium and no net thermal energy is exchanged.

• The balance is upset when temperatures are not uniform, and thermal energy is transported from surfaces of higher to surfaces of lower temperature.

• If a slab of material, as shown in Fig. 5.1, has two faces at different temperatures T1 and T2 heat will flow from the face at the higher temperature T1 to the other face at the lower temperature T2.

» Figure 5.1. Heat conduction through a slab

Conduction through a slab

• The rate of heat transfer is given by Fourier's equation:• dQ/dt = kA DT/Dx = kA dT/dx• Under steady temperature conditions dQ/dt = constant,

which may be called q: and so q = kA dT/dx• but dT/dx, the rate of change of temperature per unit

length of path, is given by (T1 - T2)/x where x is the thickness of the slab,

• so q = kA(T1 - T2)/x• or q = kA DT/x = (k/x) A DT

(5.2)• This may be regarded as the basic equation for simple

heat conduction. It can be used to calculate the rate of heat transfer through a uniform wall if the temperature difference across it and the thermal conductivity of the wall material are known.

Conduction of heat transfer through hollow cylinder

• For radial geometry of a hollow cylinder, following equation expresses the heat transfer rate.

• N = length of the hollow cylinder• T1 and T2 are inner and outer wall temperature of the

hollow