Transcript The Efficient Use of Refrigeration in Food Factories

Basic Refrigeration
Star Refrigeration
Wednesday 12 September
2007
Agenda
AM
Refrigeration basics
Simple systems
The refrigerant
The evaporator
The condenser
Agenda - continued
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PM
The compressor
The expansion device
Star designs
- LPR
- RCD
- Indigochiller
- CO2 sytems
Simple Refrigeration System
Heat Out
High Pressure
Liquid
Condenser
Expansion
Device
Work In
Low Pressure
Liquid & Vapour
Evaporator
Heat In
High Pressure
Vapour
Compressor
Low Pressure
Vapour
Basic Physics
WATER (or Refrigerant)
Fundamental “STATES”
Solid
(ICE)
Liquid
(Apply heat)
Solid
(ICE)
(WATER)
Vapour
(Apply heat)
Liquid
(Remove heat)
(WATER)
(STEAM)
Vapour
(Remove heat)
(STEAM)
Basic Refrigeration
Vapour Compression Cycle
In the Evaporator (Evaporation)
Liquid
Vapour
(Apply heat)
In the Condenser (Condensation)
Liquid
Vapour
(Remove heat)
Heat Transfer
Hot
Always Goes To
Cold
Heat from the product will migrate to the
colder refrigerant
THE REFRIGERANT WILL BOIL EVAPORATION
THE REFRIGERANT WILL LIQUEFY CONDENSATION
Heat Transfer :
Examples of Evaporation
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At 100oC Water will boil.
The energy the water uses to boil
in the kettle is heat from the electric
element.
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The energy a refrigerant uses to
boil in the evaporator is heat
from the product.
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Heat Transfer:
Examples of Condensation
Steam will condense on kitchen
tiles – heat transfer from hot steam to
colder tile.
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A refrigerant will condense when it
is exposed to a medium at a lower
temperature, such as water
or air.
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Second Law of
Thermodynamics
•
2nd Law of Thermodynamics States:
“Heat cannot of itself pass from one body to a hotter body”
• Need to do work to compress this refrigerant gas
• RRefrigeration cycle needs
A Compressor
A Condenser
An Expansion Device
An Evaporator
A Refrigerant
A pressure – enthalpy (P-H) diagram is a useful device to understand
what is happening in the cycle
The Refrigerant
In a refrigeration system, the
working fluid is the Refrigerant.
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Different refrigerants have different
boiling temperatures – well below
that of water! For example
Ammonia will boil at –33oC (at
atmospheric pressure).
Saturation Temperature
Saturation Temperature (C)
Pressure
24
19
14
9
4
-1
-40 -30 -20 -10
0
10
20
R717 Ammonia
30
40
50
Examples of Refrigerants
R22:
Ammonia:
CO2:
Currently being phased out because of its
Ozone Depleting Potential (ODP).
Star’s preferred refrigerant. Good
refrigerating properties. Zero ODP
and Zero Global Warming Potential (GWP)
“Back to the Future”. Excellent refrigerating
properties, where appropriate. Zero ODP.
GWP = 1.
Also:
New HFC synthetic Refrigerants – R134a, R404A, R407C
Zero ODP but High GWP
R410A, etc.
Typical Star Refrigeration
System
Evaporator(s)
Expansion Device
Compressor(s)
Condenser
Heat Transfer
The units for heat energy transferred in
the refrigeration system for each kg
of refrigerant flowing in the circuit is
referred to as the refrigerating effect
and has units in kiloJoule/kg (kJ/kg).
One kJ/s is equal to one kiloWatt (kW)
Summary
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Star design and build very efficient
customised refrigeration plant going into
several industrial sectors
Star Refrigeration design systems that
give maximum refrigeration energy for
minimum electrical energy input
required to run the plant.
Star plant is :
ENERGY EFFICIENT