REFIGERATION PRINCIPLES

1. UNIT-IV
REFIGERATION PRINCIPLES
Heat emitters – Expansion facilities of heating
system – Energy management – Factors
affecting fuels – Oil sand properties of natural
gas – Air conditioning, principles and
applications – Refrigerant and system
characteristics – Heat recovery devices.

2. HEAT EMITTERS
Heating, process and system of raising the temperature
of an enclosed space for the primary purpose of
ensuring the comfort of the occupants.
 By regulating the ambient temperature, heating also
serves to maintain a building’s structural, mechanical,
and electrical systems.
 A heat emitter is any product that sends out heat.
Heat emitters are used to distribute heat around a
building to maintain required set points within spaces.

3. Types of Heat emitters
1.Radiators
2.Warm Air Heaters
3.Radiant Heaters
4.Underfloor Heaters
5.Electrical Heaters

35. Recuperators

36. Recuperators can be based on the principle of heat transfer by
radiation, convection, or combinations. Recuperators are
constructed out of either metallic or ceramic materials.
(i) ‘in parallel-flow heat exchangers’ where both the gases flow in
the same general direction,
(ii) ‘in counter flow exchangers’ where both the gases flow in
opposite directions, or
(iii) ‘in cross-flow’ where the gases flow at right angles to each
other.Counter flow heat exchangers have the greatest effectiveness
while the parallel flow arrangement has the lowest effectiveness.

38. Regenerators are especially suited for high temperature
applications with dirty
exhaust gases.
 The major disadvantages are its large size and the capital
costs, which are significantly greater than costs of
recuperators.
Other disadvantages of regenerator are the accumulation of
dust and slagging on the surfaces which reduce efficiency of
the heat transfer.
Heat losses from the walls of the regenerator and air in leaks
during the gas period and out-leaks during air period also
reduces the heat transfer efficiency.

40. A regenerative burner is with a heat recovery system
that recovers the waste heat of the furnace exhaust gas
to heat up the combustion air needed for the burning
of the fuel at the burner.
Use of regenerative burners for reheating furnaces can
provide significant energy savings.