REFRIGERATION & AIR CONDITIONING
POF VISIT REPORT
INTRODUCTION:
The demand for block ice is as great today as it ever has been, despite
advances made in the development of modern refrigeration equipment. The
chemical and construction industries, for example, commonly use block ice in
situations where the use of such equipment may not be practical. The fishing
industry is also another major consumer of block ice, which is used to preserve
the fish from the time they are caught, until they are sold. It is also used to great
extents by the retailers of food and drinks to preserve food and/ or chill drinks.
Block ice is the most popular type of ice sold for a variety of reasons. It
melts more slowly than other types of ice and thus lasts longer. It can be placed
in open truck with only a tarpaulin to protect it from the elements and shipped
to a location of four hours away. Its rectangular shape makes it easy to stack of
up to 15 meters and store large amounts. Block ice has merits of easy to
transport and separate as well. Other types of ice have the tendency to freeze
into a solid mass, making it difficult to work with.
The ice making plant outlined in this proposal is the result of years of
research and development done by FRESER. The plant was designed to operate
efficiently in tropical areas, but should prove to be profitable in any climate.
PARTS OF ICE MAKING PLANT:
The complete ice making plant consists of:
I.
II.
III.
IV.
V.
VI.
Ammonia Compressors
Condensers / Heat Exchangers
Ammonia Receiver
Cooling Coil / Evaporator
Chilling Tank
Paneling (Electrical Equipments)
i.
AMMONIA COMPRESSORS:
 Ammonia compressors designed with state-of-the-art technology for
industrial & commercial refrigeration and low temperature applications.
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 Compressors are V belt driven and are suitable to operate with Ammonia
(NH3) & Freon [12 (CCl2F2), 22 (CHClF2)] as refrigerant.
 Robust construction, excellent performance and power saving features
and hallmarks of the products.
ii.
CONDENSERS/HEAT EXCHANGERS:
Condenser is a heat transfer surface, generally which are divided in to three
types.
 Air Cooled Condenser: Employ air as the condensing medium.
 Water Cooled Condenser: Utilize water to condense the refrigerant.
 Evaporative Condenser: Use both air and water as the condensing
medium. The function of the air is to increase the rate of evaporation by
carrying away the water vapor results from evaporation process.
iii. AMMONIA RECEIVER:
 Ammonia receiver can control the supply and demand relation between
the condensers and the evaporator, prevent excessive liquid ammonia
from staying in the condenser, maintain a certain level in the liquid
receiver to prevent gas from going into the liquid pipe line.
 The ammonia in the system can be stored in the ammonia receiver to
avoid loss of the ammonia before the refrigerating system is repaired.
Therefore, the volume of the ammonia storage should be considered
before buying it.
iv.
COOLING COIL/EVAPORATOR:
 Cooling Coil / Evaporator is used as heat transfer surface in which a
volatile liquid is vaporized for the purpose of removing heat from
refrigerated space.
 V shape cooling coils are available in different sizes, usually custom
made to the individual applications.
v.
CHILLING TANK:
Chilling Tank consists of three parts:
A) Ice Tank
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B) Insulation of Ice Tank
C) Ice Block
A) ICE TANK:
Ice tanks are made of such material as wood, steel or concrete. As wooden tanks
do not last long enough and are liable to leak, they should preferably be made of
steel well coated with waterproof paint. Tanks made of reinforced concrete are
also recommended as superior to those of wood.
The ice tank contains the direct expansion coils, equally distributed throughout
the tank and these coils are submerged in brine. The tank is provided with a
suitable frame of hard wood for support the ice cans and a propeller or agitator
for keeping the brine in motion: the brine in the tank acts as a medium of
contact only, the ammonia evaporating in the ice coils extracts the heat from the
brine, which again absorbs the heat for the water in the cans.
The tank itself should not be much larger than is necessary to hold the cans, the
coils, and the agitator. About two inches should be left between the moulds and
three inches between the pipes and the moulds.
B) INSULATION OF TANK:
Insulation of the ice tank is accomplished by using twelve to eighteen inches of
good insulating material on each of the sides and not less than twelve inches
under the bottom.
C) ICE BLOCK:
Commercial sizes of Ice cans vary with the weight of ice cakes required. The
cans are made to contain about 5% more than their rated capacity to compensate
for thawing.
vi.
Paneling (Electrical Equipments) :
The Neer Ice making plant is furnished with electrical control panel with
compressor starter, all necessary safety switches and press stats, Voltmeter,
Ammeter, Temperature Sensor etc.
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CAPACITY, PROCESS CYCLE AND ITS
LAYOUT:
Ice cans are placed in can grids and moved to beneath the filling
tank which automatically fills each can with proper level of pre-cooled
water and then stop. Potable water must be used to make ice intended for
human consumption.
The cans are then hoisted and carried to the brine tank and
immersed inside. The brine, which is a calcium chloride solution kept at a
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temperature of -10℃, is constantly circulated by agitator in order to keep the
temperature consistent throughout the tank.
Air is blown into the center of the can to induce a swirling motion. This
causes any impurities and air bubbles in the water to be collected in the center
of cans. Prior to finish freezing, this core is removed by a suction pump and
replaced with fresh pre-cooled water.
The time required for the water to be frozen varies according to the size
of cans being used, 150lbs. block requires 24 hours, 300 lbs. Takes 48 hours.
When the ice has completely formed, the grids are lifted up from the brine tank
and moved to place in the thawing tank. Using the warm water heats the can,
until the ice allowed to be slid out. The block ice is then removed from the can
by a can dumper. In POF 150 block per day are going manufactured and mass
of each block is 50KG. The capacity of that plant is 3.5 TONS, installed
on1981.
The empty cans are returned to filling tank for next ice making cycle. The
ice is moved to ice storage and stacked by an ice stacker, or it can be delivered
to customer right away upon requested.
 VAPOUR COMPRESSION REFRIGERATION:
Vapor-compression refrigeration is one of the many refrigeration
cycles available for use. It has been and is the most widely used method for airconditioning of large public buildings, offices, private residences, hotels,
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hospitals, theaters, restaurants and automobiles. It is also used in domestic and
commercial refrigerators, large-scale warehouses for chilled or frozen storage of
foods and meats, refrigerated trucks and railroad cars, and a host of other
commercialandindustrialservices. Oilrefineries, petrochemical and chemical pro
cessing plants, and natural gas processing plants are among the many types of
industrial plants that often utilize large vapor-compression refrigeration
systems. Refrigeration may be defined as lowering the temperature of an
enclosed space by removing heat from that space and transferring it elsewhere.
A device that performs this function may also be called a heat pump.
The vapor-compression uses a circulating liquid refrigerant as the
medium which absorbs and removes heat from the space to be cooled and
subsequently rejects that heat elsewhere. Figure 1 depicts a typical, single-stage
vapor-compression system. All such systems have four components:
a compressor, a condenser, a Thermal expansion valve (also called
a throttle valve or Tx Valve), and an evaporator. Circulating refrigerant enters
the compressor in the thermodynamic state known as a saturated vapor and is
compressed to a higher pressure, resulting in a higher temperature as well. The
hot, compressed vapor is then in the thermodynamic state known as a
superheated vapor and it is at a temperature and pressure at which it can
be condensed with typically available cooling water or cooling air. That hot
vapor is routed through a condenser where it is cooled and condensed into a
liquid by flowing through a coil or tubes with cool water or cool air flowing
across the coil or tubes. This is where the circulating refrigerant rejects heat
from the system and the rejected heat is carried away by either the water or the
air (whichever may be the case).
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The condensed liquid refrigerant, in the thermodynamic state known as
a saturated liquid, is next routed through an expansion valve where it undergoes
an abrupt reduction in pressure. That pressure reduction results in the
adiabatic flash evaporation of a part of the liquid refrigerant. The autorefrigeration effect of the adiabatic flash evaporation lowers the temperature of
the liquid and vapor refrigerant mixture to where it is colder than the
temperature of the enclosed space to be refrigerated.
The cold mixture is then routed through the coil or tubes in the
evaporator. A fan circulates the warm air in the enclosed space across the coil or
tubes carrying the cold refrigerant liquid and vapor mixture. That warm
air evaporates the liquid part of the cold refrigerant mixture. At the same time,
the circulating air is cooled and thus lowers the temperature of the enclosed
space to the desired temperature. The evaporator is where the circulating
refrigerant absorbs and removes heat which is subsequently rejected in the
condenser and transferred elsewhere by the water or air used in the condenser.
To complete the refrigeration cycle, the refrigerant vapor from the
evaporator is again a saturated vapor and is routed back into the compressor.
REFRIGERANTS:
There are three specific types of refrigerants used in refrigeration and airconditioning systems:
1. Chlorofluorocarbons or CFCs, such as R-11, R-12, and R-114
2. Hydrochlorofluorocarbons or HCFCs, such as R-22 or R-123
3. Hydrofluorocarbons or HFCs, such as R-134a. All these refrigerants are
"halogenated," which means they contain chlorine, fluorine, bromine,
astatine, or iodine.
Refrigerants,
such
as
Dichlorodifluoromethane
(R-12),
Monochlorodifluoromethane (R-22), and Refrigerant 502 (R-502), are called
PRIMARY REFRIGERANTS because each one changes its state upon the
application or absorption of heat and, in this act of change, absorbs and extracts
heat from the area or substance.
The primary refrigerant is so termed because it acts directly upon the area or
substance, although it may be enclosed within a system. For a primary
refrigerant to cool, it must be placed in a closed system in which it can be
controlled by the pressure imposed upon it. The refrigerant can then absorb at
the temperature ranges desired. If a primary refrigerant were used without being
controlled, it would absorb heat from most perishables and freeze them solid.
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APPLICATIONS:
Ice Making plants are used in different applications like :





Fisheries
Hospital
Chemical
Pharmaceutical
Commercially used in different industrial applications
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