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International Journal of Engineering and Technology Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1813
Design, Fabrication and Performance Evaluation of a
Micro-Absorption Refrigerator
Hyginus .U. Ugwu
Department of Mechanical Engineering,
Michael Okpara University of Agriculture, Umudike, Umuahia, Abia State, Nigeria
ABSTRACT
Developments in absorption cooling technology present an opportunity to achieve significant improvements on micro-scale
to buildings, cooling, heating and power systems for residential and light commercial buildings. Their resultant effects are
effective, energy efficient and economical. This study therefore contributes an important knowledge and method in the
development, fabrication and application of an absorption refrigerator as a better alternative to the commonly used
compressor refrigerators. In its embodiment, the work focuses on the design and fabrication of the absorption chiller system
with low or no vibration since there are virtually no moving parts. Also, it dovetailed into the selection of a suitable
refrigerant that is economically friendly in order to reduce or eliminate its ozone depleting effect. Consequently, the design
was fabricated using adapted locally sourced materials. This is to encourage local ingenuity and to reduce cost of production
comparable to already made custom-imported ones. It is designed to be simple, handy and readily available to be used by
anyone in case of malfunctioning and for easy relocation. Though, the main limitation of the system fabricated is the long
time it uses to achieve cooling, the performance of the machine generally is very efficient as its calculated coefficient of
performance ( C.O.P) is 1.21, which compared favourably well with the literature value of 1.00-2.00. Also, the total cost
including an over-head of 30% of the machine was estimated at forty-one thousand, two hundred and fifty-nine (N41,259.40)
naira, forty kobo only based on current price structure compared to an equivalent custom-made-imported type estimated at
between sixty to seventy thousand (N60,000.00 to N70,000.00) naira. Hence, the machine is affordable to all, and is highly
recommended for local entrepreneurs for mass production because of its cost effectiveness, simplicity and availability of
spare parts.
Keywords: Micro-absorption chiller, cost-effectiveness, energy efficient and economical, adapted locally sourced materials,
encouragement of local ingenuity, simplicity and availability.
NOMENCLATURE
CFC = Chlorofluorocarbon
HCFC = Hydrochlorofluorocarbon
HFC = Hydrofluorocarbon
LPG = Liquiefied Petroleum Gas
C.O.P. = Coefficient of Performance (TR)
TR = Tonnes of refrigeration
NH3/H2O = Ammonia/water solution (refrigerant)
Pcs = Pieces
h1, h2 = Specific enthalpies (KJ/Kg)
h3, h4 = Superheated enthalpies (KJ/Kg)
T1 = T4 = Initial temperatures (oC or oK)
T2 = T3 = Final temperatures (oC or oK)
K = Thermal conductivity (W/mK)
= Dynamic viscosity (Kg/ms)
(Small kappa) = Kinematic viscosity (Kg/ms)
CV = Vn = Cabinet volume (m3)
It = Insulation thickness (m)
CC = Condenser capacity (TR)
CE = Evaporator capacity (KJ)
V = Volume flow rate (m3/Kg)
(Nu) = Specific volume (m3)
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1814
1. INTRODUCTION
Absorption chillers are thermally driven chillers or
refrigerators using a liquid refrigerant/sorbent solution
and a heat source to provide cooling [1]. They provide
cooling to buildings by using heat. Also, they do not only
use energy than conventional equipment (simple vapour
compression refrigerators), but they also cool buildings
without the use of ozone depleting chlorofluorocarbons
(CFC). Unlike conventional electric chillers which use
mechanical energy in a vapour compression process to
provide refrigeration, absorption chillers primarily use
heat energy with unlimited mechanical energy for
pumping. These, can be powered by natural gas, steam, or
waste heat. They also transfer thermal energy from the
heat source to the heat sink through an absorbent fluid and
a refrigerant [2, 3].
Conversely, an absorption chiller/refrigerator as [4]
stated, is a refrigerator that uses a heat source (such as
solar, kerosene-fueled flame, waste heat from factories or
district heating systems) to provide the energy needed to
drive the cooling system. It is a popular alternative to
regular compressor refrigerators where electricity is
unreliable, costly, or unavailable, where noise from the
compressor is problematic, or where surplus heat is
available (such as from turbine exhausts or industrial
processes or from solar plants, etc). It uses a heat source
to provide the energy needed to drive the cooling process.
An absorption chiller/refrigerator which works on
absorption principle does not have a compressor and any
moving parts. Hence, it is very quiet in operation [5].
Here, instead of having a compressor which compresses
the low liquid refrigerant to a high temperature regime, it
uses heat to propel the refrigeration cycle instead. The
heat is generated by either using a gas (propane, Liquefied
Petroleum Gas (LPG) or natural gas, etc), kerosene
fuelled flame (which provides the energy needed) to drive
the cooling system or by the use of electricity to power
the cooling system for operation.
Two main types of absorption chillers exist. The first is
the gas chiller used in portable applications; e.g. motor
horns, boats and remote locations without electricity; and
the second, the electric absorption chiller. This is
employed where a very quiet refrigerator is desirable,
hotel rooms, and cold rooms [2].
Large industrial chillers and air conditioners are built
using this principle. They are very economical where a
source of waste heat is present and ecologically
favourable since they do not need vast quantities of
electricity like compressor driven refrigerators. The
Absorption refrigerators powered by heat from
combustion of LPG or electricity are often used for food
storage in recreational vehicles. This absorption system
uses a refrigerant with very low boiling point (less than
0˚F/-18˚C) [3]. When this refrigerant evaporates (boils),
it takes some heat away with it, providing the cooling
effect needed.
The major differences between a compression refrigerator
and an absorption refrigerator are that in the former, the
refrigerant is changed from gas back to a liquid after
being compressed mechanically so that the cycle repeats
itself, while in the latter, during absorption, the gas
changes back into liquid using heat energy. Hence, the
vapour compression refrigerator uses heat energy to
change the condition of the refrigerant from the
evaporator as the vapour absorption refrigerator utilizes
only heat energy to change the condition of the refrigerant
from the evaporator. Also, in the vapour absorption type
of refrigerator, the compressor is replaced by an absorber,
a pump, a generator and a pressure reducing valve,
respectively [5]. These components in vapour absorption
system perform the same function as that of a compressor
in vapour compression system. The other difference also
lies in the type of refrigerant used. Compressor
refrigerators typically use an HCFC (Hydro
chlorofluorocarbon) or HFC (hydrofluorocarbon), while
absorption refrigerators use ammonia or water [3].
Absorption chillers come in two commercially available
designs: single-effect and double-effect. The single-effect
machine provides a thermal coefficient of performance
(C.O.P.) of 0.7, while the double-effect machine provides
about 40% more in efficiency, but requires a higher grade
of thermal input [6]. In single-effect absorption machine,
all condensing heat cools and condenses in the condenser,
from where it is released to the cooling water, while a
double effect machine adopts a higher heat temperature
generator.
The performance of an absorption chiller is described in
terms of its C.O.P. given as the ratio of heat extracted in
the refrigerator to the work done on the refrigerant which
invariably could be taken as the theoretical C.O.P. [5].
The schematic of the working principle of an absorption
chiller is as represented in Figure 1.
2. REVIEW OF RELATED
LITERATURES
The use of ice to refrigerate and thus preserve food goes
back to prehistoric times [7, 8]. Through the ages, the
seasonal harvesting of snow and ice was a regular practice
of most of the ancient cultures. Ice and snow were stored
in caves or dugouts lined with straw or other insulating
materials. However, it was not until the middle of the 20th
century after many modifications and consolidated
researches in that respect [9, 10, 11, 12, 13, 14] that
refrigeration units were designed for installation on trucks
or lorries. Refrigerated vehicles hitherto were used to
transport perishable goods, such as frozen foods, fruits
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1815
and vegetables, and temperature-sensitive chemicals.
Most modern refrigerators keep the temperature between -
40 and 20oC, and have a maximum payload of around
24,000Kg gross weight in Europe [15].
With the invention of synthetic refrigerants based mostly
on a CFC chemical, safer refrigerators were possible for
home and consumer use. Freon, a trademark of the
Dupont Corporation refers to these CFCs, which later was
overtaken by the advent of HCFC and HFC refrigerants
developed in the late 1920s. These refrigerants were
considered at the time to be less harmful than the
commonly used refrigerants of the time, including methyl
formate, ammonia, methyl chloride, and SO2. The intent
was to provide refrigeration equipment for home use
without danger. These CFC refrigerants answered that
need. In the 1970s, though the compounds were found to
be reacting with atmospheric ozone, an important
protection against solar ultraviolet radiation, and their use
as a refrigerant worldwide was curtailed in the Montreal
Protocol of 1987 [15].
On application, the most widely used current applications
of refrigeration probably are for air conditioning of
private homes and public buildings, and refrigerating
foodstuffs in homes, restaurants and large storage
warehouses. The use of refrigerators in kitchens for
storing fruits and vegetables has allowed adding fresh
salads to the modern diet year round, and storing fish and
meats safely for long periods. Also, dairy products are
constantly in need of refrigeration, and it was only
discovered in the past few decades that eggs needed to be
refrigerated during shipment rather than waiting to be
refrigerated after arrival at the grocery store. Meats,
poultry and fish must be kept in climate-controlled
environments before being sold. To keep fruits and
vegetables edible longer, refrigerators/chillers are
employed.
In this treatise “Design, fabrication and performance
evaluation of a micro-absorption chiller for efficient
refrigeration”, ammonia/water (NH3/H2O) was utilized as
the refrigerant. The research study was conceived to
overcome, reduce and/or eliminate drastically the
imminent problems associated with the use of CFCs as
refrigerants in the compressor refrigerators since they
possess high rate of ozone depletion factor and affinity
which could be poisonous and dangerous to human health
and consequently pollute the environment and
atmosphere.
The significant advantages derivable in adopting and
commercializing this design are enormous. First, the
refrigerant (NH3/H2O) has high cooling and refrigerating
effect. Second, the entire system is noiseless since it has
no moving part. Also, it has no compressor but an
absorber and hence, its operation is very quiet. Since it
uses heat to propel the refrigeration cycle, its C.O.P. is
very high. Further, as the pumped circulation of the
sorbent solution on the absorption chiller replaces the
compression of the refrigerant, the energy and work
required by the pump are significantly less than required
by the compressor.
However, the limitation of this system is the cost criterion
which is the primary constraint on the widespread
adoption of the unit. Also, the low thermal efficiency of a
single-effect absorption system made the system non-
competitive with readily available free waste heat. The
absorption system only requires greater pump energy than
an electric chiller. Consequently, the chiller requires
larger cooling tower capacity than an electric chiller due
to the large volume of water.
Figure 1: Working principle of an absorption chiller
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1816
3. MATERIALS AND METHODS
3.1 Problems Associated with Other
Conventional Materials
The following are some of the problems being faced with
when using other conventional materials such as copper,
aluminum, HCFC or CFC refrigerants.
i. Reaction of NH3/ H2O refrigerant with copper leads
to leakage of pipe.
ii. There is high production rate of component parts; and
iii. It leads to high cost of production, etc.
3.2 Material Selection
The first step taken in selecting materials from a variety
of materials (aluminum, copper, steel, alloys, etc) was by
carefully defining categorically the requirements of the
desired components. This was followed by checking these
requirements so as to make the selected materials readily
available.
3.3 Materials Used
The major materials used are steel metal pipes (for the
fabrication of some components like condenser, heat sink,
evaporator, etc); wood (used for the construction of the
body frame/casing); and NH3/H2O refrigerant as the
refrigerant for the absorption refrigerator.
3.4 Fabrication Processes of the Absorption
Chiller
The fabrication processes of this absorption chiller
involve three stages only:
i. Sourcing and furnishing of the wood;
ii. Gas welding; and
iii. Electric arc welding processes of the steel materials,
respectively.
The casing for the chiller was done using wood; and has
the dimensions: length 45.5cm, height 50cm and breathe
30cm, respectively. From this dimensions, the wood was
sawed, planned and polished. Afterwards, the various
dimensions were brought together and joined using gum
(top bond) and nails where needed. The backside was
covered with a flat wood throughout for easy passage of
the steel pipes.
Secondly, a flat metal sheet was brought out and cut to a
size of length 8cm and width 4.5cm with a hole bored in
its middle where 0.635cm (¼ inch) pipe with internal
diameter of 0.6cm (6mm) was passed through the sheet
metal to fabricate the heat sink. Consequently, an
electrical welding method was used to tag the flat metal of
about 44pcs to the pipe.
According to [5], the number of turns of the condenser
affects the cooling effects of a refrigeration system. Thus,
the maximum number of turns required for efficient
refrigeration was estimated at 6 turns. Hence, the
condenser was fabricated with a 1.27cm (½ inch) steel
pipe of 1cm (10mm) internal diameter. This was made by
bending the steel pipe with a spring pipe bender to the
required shape and number of turns needed.
Also, the set-up was then welded to the charging
aggregate containing 0.04Kg of NH3 and 1.59cm (5/8
inch) pipe was passed through to the evaporator, while a
1.27cm (½ inch) pipe was welded electrically to the
generator. The pipe carries the anhydrous NH3 to the
generator for heating, while the generator was covered
with a fiber to prevent heat loss by convection. Some of
the components which were not fabricated due to non
feasibility of the fabricating process or non availability of
the technical know-how were: the generator, evaporator,
thermostat, charging aggregate and the heating filament,
respectively which were procured from the market.
Finally, the whole set-up assembly of the micro-
absorption refrigerator fabricated is as presented in Figure
2. Other configurationally views of the system as
designed and fabricated are as depicted in Figures 3 (a-d),
respectively.
Figure 2: The whole set-up assembly of the micro-absorption refrigerator
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1817
Figure 3 (a): Front view of the micro-absorption refrigerator
Figure 3 (b): Side view of the micro-absorption refrigerator
Figure 3 (c): Orthogonal view of the micro-absorption refrigerator (Dimensions in cm)
Figure 3 (d): Back view of the micro-absorption refrigerator
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1818
4. RESULTS AND DISCUSSIONS
4.1 Specifications of Parameters from the
Psychrometric Chart
These involve all values gotten from the psychrometric
chart and tables, respectively for NH3 and specified thus:
Operational temperature range = -15oC to 35oC (258K to
308K); Boiling point = 33.3oC (306.3K); Critical
temperature = 132.4oC (405.4K); Critical pressure =
112.8bar;
h1 = 253.375KJ/Kg;
h2 = 1458.56KJ/Kg;
h3 = 1590.625KJ/Kg;
h4 = 1711.36KJ/Kg;
h1, h2 = Specific enthalpies; h3 and h4 = Super-heated
enthalpies;
T1 = T4 = 27oC (300K); T2 = T3 = 5oC (278K)
[16, 17]; where:
T1 = T4 = Initial temperatures and T2 = T3 = Final
temperatures.
Also, the thermal properties at room temperature and
constant pressure are:
Thermal conductivity, K = 22.19W/mK; Dynamic
viscosity, µ = 1.25Kg/ms;
Kinematic viscosity, =
(1)
Density of NH3 vapour = 0.73Kg/m3; Ammonia
molecular weight = 17.03g/ml; Ammonia melting point =
-78oC (195K); Specific volume of ammonia vapour =
1.411m3/Kg; and Specific heat capacity of NH3 =
0.028KJ/mol, respectively.
4.2 Experimental Tests and Results
In actualizing the aims of this study, performance tests
were carried out after the equipment had been assembled.
The machine was put on and ten different temperature and
pressure readings were taken starting from a standard
room temperature of 27oC (300K) made within an interval
of 30 minutes each. The experimental result is as shown
in Table 1 and represented graphically on a temperature-
pressure diagram in Figure 4, respectively. These were
obtained through interpolation of values as presented
here-under.
Table 1: Experimental results obtained
S/No
t (min)
t (hrs)
Temperature
(oC)
Pressure
(bar)
Specific enthalpy
Super- heated
enthalpy
(hf1)
Properties
(hg1)
hf
(KJ/Kg)
hg
(KJ/Kg)
1
0
0
27
10.670
308.55
1467.15
1606.65
1731.15
2
30
0.5
24
9.722
294.1
1465.2
1602.7
1726.3
3
60
1.0
20
8.570
275.1
1462.6
1597.2
1719.3
4
90
1.5
18
8.035
265.5
1461.1
1594.4
1715.9
5
120
2.0
16
7.529
256.0
1459.5
1591.7
1712.5
6
150
2.5
14
7.045
246.6
1457.8
1588.9
1709.1
7
180
3.0
12
6.585
237.2
1456.1
1586.0
1705.7
8
210
3.5
10
6.149
227.8
1454.3
1583.1
1702.2
9
240
4.0
8
5.736
218.5
1452.5
1580.1
1698.4
10
270
4.5
5
5.161
204.4
1449.55
1575.5
1693.05
Total
2533.75
14585.80
15906.25
17113.60
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1819
Figure 4: Graph of temperature against pressure
It is to be noted that the experiment could have been taken
under different environmental conditions (such as: in a
place under low temperature environment like where an
air conditioner had already cooled the environment; and
in an environment where there is an increased heat source
like in a bakery with an oven in operation) in order to
determine effectively the performance in terms of the
C.O.P. of the machine for variation of experimental test
data. But however, these were limited and hence not
undertaken due to non-availability of regular power
supply in MOUAU and its environ within the periods of
the testing. Thus, these de-limited comparison which
could have been made for the analysis to ascertain its
performance at various environmental conditions.
4.2.1 Parametric Interpolation of Variables
at 27oC
Equation 2 was used for the interpolation to obtain the
values of the parameters at 27oC for a higher temperature
region which were not on the properties tables. Thus:
Interpolation equation =
(2)
Hence:
(a) For the pressure at 27oC:
= 21.98
= 21.98 – 0.65 = 21.33
Pressure, = 10.67bar
(b) For specific enthalpy, :
= 626.8
= 626.8 – 9.7 = 617.1
= 308.55KJ/Kg =
(c) For specific enthalpy,
= 2935.6
= 2935.6 – 1.3 = 2934.3
= 1467.15KJ/Kg =
(d) For superheated enthalpy,
= 3216.0
= 3216.0 – 2.7 = 3213.3
= 1606.65KJ/Kg =
(e) For superheated enthalpy,
= 3465.4
= 3465.4 – 3.1 = 3462.3
= 1731.15KJ/Kg =
4.2.2 Parametric Interpolation of Variables
at 5oC
Similarly, the values of the parameters at 5oC for a lower
temperature region which were not on the properties
tables are obtained thus:
(a) For the pressure at 5oC:
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1820
= 10.692
= 10.692 – 0.371 = 10.321
Pressure, = 5.161bar
(b) For specific enthalpy, :
= 418.2
= 418.2 – 9.4 = 408.8
= 204.4KJ/Kg =
(c) For specific enthalpy,
= 3154.0
= 3154.0 – 3 = 3151.0
= 1575.5KJ/Kg =
(d) For superheated enthalpy,
= 3389.8
= 3389.8 – 3.7 = 3386.1
= 1693.05KJ/Kg =
Further, the values of the specific enthalpies and the
superheated enthalpies, respectively were obtained by
taken the average of each enthalpy; where: = h3 and
= h4. This was done by adding each enthalpy and
dividing them by 10 which is the number of experiments
carried out; hence:
i.
253.375KJ/Kg
ii.
1458.58KJ/Kg
iii.
1590.625KJ/Kg
iv.
1711.36KJ/Kg
4.2.3 Other Parameters Estimated
(a) Cabinet (chiller) casing:
The cabinet areas were calculated by considering both
sides of the six faces of the walls. Hence:
Cabinet areas = (up and down) + (two opposite sides) +
(other two opposite sides) (3a)
Mathematically:
cm2
Or: (3b)
Thus:
= 2(5140)
An = 10280cm2 or 1.028m2
(b) Cabinet volume, :
Based on the inside dimensions of the cabinet, the
insulation thickness on both sides of the six faces
were not included in determining the volume. However,
for this design, an insulation thickness of 2.3cm was
utilized which was the thickness of the wood used for the
chiller casing after sawing and planning. Hence,
according to [18]:
(4)
=
2 2.3
=
=
40.9 25.4
= 47164.244cm3 or 0.047164244m3
0.0472m3 =
(c) Mass Flow Rate:
This is obtained from:
(5a)
(5b)
Mathematically:
(5c)
Thus:
=
=
or 0.000032373
(d) Condenser Capacity:
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1821
It is the heat rejected by the refrigerant in unit time in the
condenser. This is given as:
(6)
Hence:
(132.045)
= 4.2747TR
or 0.0042747TR (Tonnes of refrigeration).
(e) Refrigeration effect is the quantity of heat absorbed
by a unit mass from the refrigerated space. It takes
place at the evaporator. Here:
Thus: (7)
KJ
(f) Evaporator Capacity:
This is the capacity at which heat is removed from the
refrigerated space. It is given as:
(8)
Thus: (1457.985)
KJ
(g) Volume flow rate (V): This is the amount of saturated
vapour (m3) produced when 0.04kg of refrigerant
vapourized; which is dependent on the refrigerant,
NH3. This is determined as:
(9)
Thus: (1.411)
or 0.000045678
where: = Specific volume of ammonia as specified.
(h) Coefficient of performance (C.O.P.): This is used to
measure the performance of the refrigeration system
expressing its output to input ratio and given as:
(10)
Hence:
C.O.P. = 1.2097 1.21
(i) Kinematic viscosity,: This is given as:
=
(11)
= 1.71233
(j) Work done by the generator, W: This is given as:
= W (12)
Thus:
=
= 1.99418 or 0.000019942 = W
4.3 Discussion of Results
The experimental results of the performance of the micro-
absorption chiller test conducted show that the machine
fabricated has a C.O.P. of 1.21. This conforms to the
standard normal performance of a single-effect machine
that produces a C.O.P. of about 1.00 to 2.00 [2, 3, 19].
The results defined the characteristics of the machine and
showed that its performance is in line with the C.O.P. of
all other single-effect refrigerators or chillers.
The machine was powered by a 250volts generator.
These suggest that the produced absorption system has a
good working condition in which temperature, pressure or
any other environmental property cannot reduce its
performance similar to already custom-made imported
ones.
5. COST ANALYSIS AND EVALUATION
OF THE MACHINE
Table 2 shows the cost implications of the materials used
in the fabrication of the machine.
The labour cost is the hour-charge per day for the
completion of the work. This implies the amount paid for
the fabrication. The labour cost for the completion of this
machine as evident in Table 2 was five thousand, five
hundred (N5, 500.00) naira only. Also, the cost of the
machine equals the summation of the cost of the materials
and the labour cost, respectively. Hence, the total cost as
inferred from the Table was estimated at thirty one
thousand, seven hundred and thirty-eight (N31, 738.00)
naira only. This amount represents the total cost for the
production of this micro-absorption chiller. However, the
amount excluded the cost of transportation and other
miscellaneous expenses incurred. Based on these, an
overhead cost of about 30% was estimated which brought
International Journal of Engineering and Technology (IJET) – Volume 2 No. 11, November, 2012
ISSN: 2049-3444 © 2012 – IJET Publications UK. All rights reserved.
1822
the final cost to forty one thousand, two hundred and
fifty-nine (N41, 259.40) naira, forty kobo only.
Table 2: Cost implications and analysis of the machine
S/No
Components
Specifications
Quantity
Cost (N)
1
Materials
Body (wood)
(50 x 40.5 x 30) (H x L x B) cm3
1
3,800.00
2
Condenser (steel metal)
(1.27 x 27 x 10) (D x L x B) cm3
1
2,500.00
3
Evaporator (Aluminium)
(29 x 25) cm2
1
2,238.00
4
Heat sink (steel metal)
0.64 x 35 x 60) (H x L x B) cm3
1
2,700.00
5
Generator
(35 x 7) 250 volts
1
4,500.00
6
Charging aggregate
0.4kg of ammonia gas
1
5,300.00
7
Thermostat
11
1,100.00
8
Paint
Black coloured oil paint
1
500.00
9
Wood sprang
Cream coloured
2
2,200.00
10
Fused plug
13Amp (250 volts)
2
50.00
11
Wire
3yards
300.000
12
Aluminium handle
1
150.00
13
Key lock
1
100.00
14
Connection box
1
100.00
15
Formica
1 yard
700.00
Sub-total (Materials)
26, 238.00
16
Labour
5,500.00
Total
31,738.00
Overhead/Grand total @ 30% factor
41, 259.40
6. CONCLUSION AND
RECOMMENDATIONS
6.1 Conclusion
The design and fabrication of this micro absorption chiller
was partly done using adapted locally sourced materials
since some parts/components were not fabricated but
procured from the market. The machine was designed to
be handy, simple and used by any one, and at any place. It
was designed to be simple in case of malfunctioning and
for easy relocation.
The operation of the machine is electrical by plugging it
to a power source. The main limitation of the system is
the time it uses to cool. But generally, the performance of
the machine is very efficient as its calculated C.O.P. was
1.21 which compared favourably well with the literature
value of 1.00-2.00.
6.2 Recommendations
This machine was designed to reduce the impact of
emission emanating using HCFCs or CFCs as refrigerants
to the atmosphere and to preserve perishable goods.
However, the system is limited to only electrical power
source. Hence, it is recommended that other sources of
powering the machine (solar, waste heat, etc) should be
encouraged for further studies to improve its operation
and performance. It is also proposed that high aluminum
pipe materials should be used as the condenser. This will
increase the capacity of the generator thus speeding up the
heating process of the system.
ACKNOWLEDGEMENTS
Special thanks by the author go to Messrs. Nwazue
Samuel, Odika Collins and Nwakanma Ifeanacho of the
Department of Mechanical Engineering, MOUAU for
their valuable contributions in the analyses and fabrication
of the machine. Also, special gratitude goes to the Staff
and Management of Mandilas Group of Companies for
their advices and endless cooperation in providing
information and relevant materials that led to the
completion of the system and of the study.
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