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CHAPTER II THEORITICAL2.1 The Definition of Air ConditioningAir
conditioner or AC is one of the cooling equipment (refrigeration).
Other tools that work using the cooling system is like a
refrigerator, a freezer and cold dispenser. The basic principle of
the work of the cooling system can be defined as "relocate or move
the heat". So the principle of work of an air conditioner in a cool
room was by way of moving the hot air out of a room (in-door) into
the air outside the room (out door).Figure 2.1 Air-conditioning
(AC) [1] Principle or the workings of AC or refrigeration machine
room ;1. Heat energy is absorbed refrigran in the Evaporator and
where it comes out as the cold air.2. The heat absorbed by the
evaporator is taken out by a steam pipe refrigran.3. Heat is
carried by air to the air being dumped out of the condenser have
circulated.4. Refrigran cool bersikulasi back the liquid pipe.5.
And log back into the EvaporatorBecause indoor air temperature and
the temperature of the outside air is actually no different, then
to move heat in cooling AC needed energy. I.e. energy needed
electricity to pump heat from indoors and throw it out of the
room.Figure 2.2 The Scheme Of Work Of Cooling Machine (AC) [2]
2.1.1 Condenser The condenser is a tool for creating condensation
cooling material gas from the compressor with high temperature and
high pressure. For penempatanya, the condenser placed outside the
room that is being cooled, so that the heat can throw out. The
condenser is pipelines that serve as condensation. The dipompakan
of the Refrigerant compressor will experience the emphasis so that
it flows into the condenser pipe, then subjected to condensation.
From here the refrigerant is condensed and liquid will flow to the
evaporator pipe.
Figure 2.3 Condenser [3] The condenser is a heat exchanger
machine type (heat exchanger), which serves to mengkondensasikan
the working fluid2.1.1.1Types of Condenser In General, there are
two types of the condenser:1. Surface Condenser The working
principle of the surface condenser , as shown in Figure 2.4 sthe
team goes into the condenser shell through the steam inlet
connection on the top of the condenser. The Steam then intersect
the spectral low condenser tube so that the temperature of the
steam down and condensed, producing the condensate accumulated in
the hotwell.
Figure 2.4 Surface Condensor [4] Low temperature on tube is
maintained by means of mensirkulasikan water that absorbs heat from
steam condensation on the process. The heat is here called latent
heat evaporation and condensation heat also sometimes called (heat
of condensation) within the scope of the discussion of the
condenser. Hotwell condensate accumulated in later moved from the
condenser by using the exhaust condensate condensate pump.When
leaving the condenser, almost the entirety of the steam has been
condensed from the saturated portion except the air that is in the
system. There is air in the system generally occurs due to a leak
at shaft seal, piping, valves-valve, and so on.It goes into the
condenser together with steam. Dijenuhkan air by water vapor, and
then water passes cooling section where a mix of steam and air
cooled condenser for further disposed of by using water ejectors
that serves to maintain a vacuum in the condenser. To eliminate the
air dissolved in the air due to the condensate in the condenser,
done de-aeration. De-aeration is done in the condenser with heat
the condensate with steam to the air terlalut on condensate will
evaporate. The air is then drawn into the air cooling section with
a harness of low pressure that occurs in water cooling section. Air
ejector would then move the air from the system.The following are
the types of condenser type surface condenser.a.
Horizontal condenser Cooling water enters through the bottom of
the konddensor, then enter into the cooling pipes and out at the
top while the incoming heat flow through the central part of the
condenser and out as condensate on the bottom of the
condenser.b.
Vertical condenser Cooling water enters through the bottom of
the konddensor, then enter into the cooling pipes and out at the
top while the incoming flow of heat through the top of the
condenser and out as condensate on the bottom of the condenser.2.
Direct-Contact Condenser Direct-contact steam mengkondensasikan
condenser mix it with cooling water. Direct-contact or open a
condenser used in some special cases, such as:a.
Geothermal powerplantb. The powerplant that uses the temperature
difference in sea water (OTEC)
Figure 2.5 Direct Contact Condenser-[5]An example of the
condenser typeDirect-Contact spray condenser Condenser At steam,
mixing with cooling water is carried out by way of spraying water
into steam. So the steam coming out of the exhaust turbine at the
bottom are mixed with water cooling in the Middle, producing
condensate approaching phase saturated.Then dipompakan back into
the cooling Tower. Some of the condensate back to the boiler as the
feedwater. The rest refrigerated, usually in dry-(closed) cooling
tower. The water is cooled in a Cooling tower is sprayed into the
exhaust turbine and the process repeats.2.2 Definition of Heat
Transfer Heat transfer is the transfer of energy due to differences
temperature. There are three forms of heat transfer mechanisms are
known, namely conduction, convection, and radiation.2.2.1Conduction
Conduction is the transfer of heat from a place that has a high to
low temperate in place in the medium that directly intersect. If on
an object there is a gradient of temperature, then heat transfer
may occur as well as energy from the high temperature to low
temperature parts, so that it can be said that the energy will be
moved by conduction, the rate of transfer of kalornya stated the
following :
[7].....................................................
(2.1)Where:
= Heat transfer Rate (W) = Cross-sectional area where heat flows
(m2) = Temperature Gradient in the cross-section, or rate of change
of temperature T against the distance in the direction of heat flow
x
= Thermal conductivity of the material (W/moC)
Figure 2.6 Example of Heat Transfer by Conduction[6]2.2.2
Convection Convection is heat transfer between the solid surface
and adjacent to a moving fluid or flow and it involves the effects
of conduction and fluid flow[1] .
Figure 2.7 Examples of Heat Transfer from the Hot Plate[7]From
the picture above, it can be seen that the speed of the fluid that
flows in surface plate heat affects the temperature around the
surface of the plate. The rate of heat transfer by convection can
be expressed as[7 ]
:.................................................... (2.2)Where:=
Convection heat transfer Rate (W)= Heat transfer Coefficient of
convection (W/m2 0C)= Cross-sectional area (m2)= Temperature
difference or Change (0C; 0F)2.2.3 Radiation Radiation is the
transfer of energy, because the emission of waves electromagnetic
fields (or photons). The rate of heat transfer radiation has can be
formulated with: [7].
.................................. (2.3)Where:
= Stefan-Boltzman Constant = 5,669 x 10-8 (w/m2 k4)
= Cross-sectional area (m2)
= Temperature ( C)
Figure 2.8 The Radiation Heat Transfer [6]2.3Types Of Water Flow
The flow can be classified in various types such as: turbulent,
laminar, real, ideal, and more. Fluid flow through the installation
(pipes) there are two types of flow.2.3.1 Laminar Flow Laminar
Flow, also known as viscous flow. These terms are descriptive of
the laminar flow, because flow, a layer of water flows on top of
each other with different speeds with virtually no mixing between
the layers, the fluid particles move in definite paths and can be
observed, and the flow was characteristic of the viscous fluid or
is where one fluid viscosity plays a crucial part:
.........................(2.4)From the above equation note that
flow is laminar, the magnitude of the friction factor is influenced
by the amount of liquid to Reynolds, and not depending on the
hardness of the pipe
Figure 2.9 Laminar Flow[8 ].2.3.2 Turbulent FlowTurbulent flow
is a flow that is marked with the random movement of the fluid
elements where each element of the fluid velocity has fluctuated.
Happens on "high" the flow rate and is often utilized for better
mixing. In the turbulent flow conditions that occur resulting in
turbulent shear stress evenly throughout the liquid resulted in
losses of flow.
Figure 2.10 Turbulent Flow[8 ].To determine the shape of the
flow of laminar and turbulent flow there is in the image below:
Figure 2.11 Laminar Flow and Shape the Turbulent Flow [8 ].2.3.3
Incompressible FlowIn fluid mechanics or more generally continuum
mechanics, compressible flow (isochoric flow) refers to the density
of the material where the flow is constant in the package-a very
small volume of fluid moving with water (fulid) speed. An example
of a compressed fluid is: water, oil, various types such as
emulsion, etc. Form the Bernoulli Equation for Incompressible flow
is as follows: = constant ....... (2.5)
Information: = Water velocityg = Gravitational forceh = A
relative highp = Pressure of fluid = Density of waterThe above
equation is valid for incompressible flow with the following
assumptions: steady state InviscidIn different forms, can be
written as follows........ (2.6)
2.3.4 Compressible Flow Compressible flow describes the behavior
of fluids that are experiencing significant variations in density.
To flow where the density does not vary significantly, the flow
behavior analysis can be simplified greatly by assuming a constant
density. The Bernoulli equation for the compressed flow is as
follows = constant ...... (2.7)Information: = Gravitational
potential energy of mass unity: if gravity is constant then = gh W
= Enthalpy of the fluid mass unity2.4 Thermoelectric
ConceptThermoelectric technology works by converting heat energy
into electricity directly (Thermoelectric generator), or otherwise,
of electricity produces cold (refrigeration thermoelectric). To
produce electricity, material Thermoelectric simply laid in such a
way in the circuit that connects the hot and cold sources. The
series will be produced from a number of electricity according to
the type of materials used.2.4.1 Thermoelectric Generator (TAG)
Thermoelectric (TAG) plant is a power plant based on the Seebeck
effect, which was first discovered in 1821 by Thomas Johann
Seebeck. He connected the copper and iron in a series. In between
the two metal is then placed needle compass. When the metal is
heated, the compass needle turns moves. This happens due to the
flow of electricity that occurs at the metal gives rise to a
magnetic field. The magnetic field that moves the needle of the
compass. The phenomenon came to be known with Seebeck effect.
Figure 2.12 shows the TAG structure, consisting of an arrangement
of n-type element (a material with an excess of electrons) and
p-type (material with an electron deficient). The heat goes on one
side and the other side disposed of, resulting in a voltage drop
that pass through sambuangan Thermoelectric. The magnitude of the
voltage produced is proportional to the temperature
gradient[3].Voltage (V0) can be expressed by the equation: V0 = X Y
x (Th a T c) .................................. (2.8) Where:V0 =
Output voltage (Volt)XY = Seebeck Coefficient of material between 2
X and Y (Volt/K)Th, Tc = Termokkopel hot and cold Temperature
(K)
Figure 2.12 Structure Thermoelectric Generator (TAG) [9
].Thermoelectric is a integrated circuit module in the form of a
solid using the three principles of thermodynamics which is known
as the Seebeck effect, Peltier and Thompson. Construction consists
of a pair of p-type semiconductor material and n-type forming
thermocouples which has the form of a sandwich between two wafer
thin ceramic. This module can be used to generate heat and cold in
each side if the electricity used is usually applied as a cooling
system for example cooler vaccines or to produce electricity when
used as a hot and cold temperature difference.Heatsink used to help
increase the release of heat on cold side so as to improve the
efficiency of the module. The potential power generation from a
single berbedabeda Thermoelectric modules will depend on the size,
construction and the difference in temperature. The greater the
temperature difference between the hot side and the cold side of
the module will generate a voltage and current. Thermoelectric
modules can also be connected together either in series or in
parallel like a battery to generate voltage or electric current.
Each module is able to produce the average voltage 1-2V DC and even
up to 5V DC depending on the variation, but generally the
temperature delta one Thermoelectric module produces 1.5-2V DC[9
].Currently, the application TAG has been widely applied in various
fields, an American company (Hi-Z Technology, Inc.) has been
successfully developed eight peltier module (model HZ-14) used on
glycol generator and can generate power of 60 Watts with an ambient
temperature of 15-30C and operating temperature range 175-200C.
Large power generated due to the module used is a special
TAGinstead of the TEC and the difference in the temperature reaches
170C. Thermoelectric technology development of Hi-Z experienced a
rapid progress since the current Hi-Z technology is able to reach
the value of ZT (figure of merit), although still produced on a
small scale[9 ].2.4.2 Thermoelectric Cooling (TEC) Thermoelectric
cooling (TEC) is a component of the Peltier Effect applied. Peltier
is a component that includes the Thermoelectric component, which
occurs when the temperature difference disntsrs two sides then
these components transform it into electric voltage magnitudes, and
vice versa, when an electrical voltage is given to this component,
then it can turn it into two different temperatures[10].
Figure 2.13 Peltier Elements[10].In practice, the TEC uses
several thermocouples laid out series that facilitate heat
transfer. Generally the outside of this component is wrapped a thin
ceramic containing stem-batangBismuth Telluride inside. The
Material is a semiconductor which added an additional substance
aims to provide excess free electron (N-type semiconductor) or give
you a free electron deficient (P-type semiconductor) [10].
Figure 2.14 Peltier Element Work Illustrated[10].The electrons
from the electron-deficient material (P-type material) material
moves into excess electron (N-typematerial). In these circumstances
it will absorb the enrgi connector. When the electron moves from
the N-type to P-type, then the connector will release energy. The
energy absorbed or released is given in the form of heat. Peltier
element work illustration shown in Figure 2.14.2.5 Aluminum
Aluminum is often found above the Earth in the form of chemical
compounds, but not found in nature in a State of pure aluminum. The
most important raw material for the manufacture of aluminum is
bauxit, which is a crowd of minerals (land of alum, aluminum oksid)
and affix oksid iron from acid siklat. Bauxit contains 55 65%
ground alum, 2 24% iron, 12 30% water and 1 8% siklat acid. The
color depends on bauxite affix. Figure 2.1 shows an example of
aluminum ingots (ingots)[11].
Figure 2.15 Aluminum Ingots [11] .The main findings in Europe
are France, Italy, the Balkan countries, Russia, and Hungary. But
in Africa, the Americas, Asia, and Australia there are many sources
of bauxit. How to obtain pure aluminum includes four stages:
Preparation of bauxsit (pelumatan, purification, drying,
penggerusan)Rarefaction bauxit become pure alumAbsorption of acidic
substances (the reduction) of land into a raw aluminium alum
through electrolysis melting with a solvent as kryolithSmelting of
pure aluminum in Some properties of pure aluminum is kind of low
weight, colour silver, shiny white, has a conductivity of heat and
electricity well, endurance may be consumed. Aluminium envelop
itself in the air with a layer of oksid (protector) that should not
be tampered with. Aluminum is not sustainable against alkali and
acid salts. Because violence is low, aluminum is less good for the
modified form with appropriate for flakiness and knowest. This is
required for the flakes are big, tall and sayat speed of a suitable
lubricant.
Aluminum is really soft and easily stretched so easily modified
form in a State of cold and heat. Aluminum can be welded and
solder. This is required for pelumer materials and materials
welding. Aluminum is not magnetic, no-toxic and a reflector
(reflectors behind) are good for heat, light and electromagnetic
waves. Through a suitable surface treatment can be diverse
beautiful embodiment.As the power and violence is low, then the
pure aluminum is not suitable for machine parts that are bearing
the brunt. That specifies on its use besides does it weigh a light
is preserved against corrosion. In elektroteknik, aluminum is used
as an ingredient of carriage (special provisions) for capacitors,
cables, cable sheath. Aluminum termurni meet the demands the
highest chemical resistance will be increased in accordance with
the degree of purity. The acid and soda is hard is able to dissolve
membranes oksid and attacking aluminum. The most important
exception: oxidized salpeter acid with strong and not dissolve or
attacking the purest aluminum. Because it's the purest aluminum
used in chemical manufacturing and installation assembly container
for salpeter saturated acids [11].2.5.1 Aluminum Properties
Aluminum is the most used metal after steel. Aluminum is amfoter
and is easily oxidized. As for the basic properties of aluminum so
it can be used in a machine or vehicle's frame: 1. Lightweight,
with a specific weight of 2,7 g/cm3. Therefore, these metals are
widely used in the form of metal as material exchanger with a high
speed connection such as a piston at the bars.2. A good heat
conductor, so used to additional material on the wire. If the thin
steel core is added, then it would have greater power. 3. Aluminum
has a very high thermal conductivity as a component of heat
exchanger on the piston.4. Non-toxic, so it is widely used in
chemical factories and in the food industry, for domestic purposes,
for buildings, and equipment of the vessel, in addition in the form
of aluminium foil used for packing and bottle caps.5. Have a great
attraction to oxygen, which allows the metals used as pengoksidan
in steel, as a mixture of iron oxide and Aluminum powder used to
weld rail.To get a better strength and corrosion resistant
aluminium is usually combined with other types of metal. Because of
the light metal is a good conductor of heat, after copper. Can be
forged, cast, done by machine, soldered, welded, stamped and
hardened, withdrawn, and at ekstruksi. Can be made into a variety
of forms for further processing or manufacturing process that is;
sheets, plates, bars, pipes, and wires.Pure aluminum is soft and
chewy, but when mixed with small amounts of other elements, her
strength and violence will go up, some alloys have a strength equal
to or more than the soft steel. To maintain the stability of
aluminium corrosion does not occur in order for it to be painted or
lacquered aluminium and so are not affected to the acid. Anodizing
that is the formation of oxidation on surface of aluminum
electrolysis, in which time the flow is passed through a metal and
an electrolyte to the cathode, so the normal oxide layer will add a
layer which is almost transparent and its thickness can be
arranged. This layer is harder and less porous, allowing for
permanent staining with basic ingredients in organic paint colors
are very attractive. Surface-surface dianodise usually closed
meetings and can be lacquered [11] .2.5.2 Aluminum Alloy Properties
of aluminum materials will undergo repairs that blatant when he
combined with other metals. Copper exalt violence, power, magnesium
silisium. Other integrators metal is magnesium nickel zinc,
resulting in a desired trait in a small percentage. Possibility of
selection of the many aluminum manifold which opens an opportunity
for area for aluminum spreaders. Mainly to increase the mechanical
solidity of aluminium then try with the road design. In that case
sought wherever possible to maintain or improve nature pure
aluminum is good as a kind of low weight, durability may be
consumed, electric and heat conductivity is good, its convenience
for the trend to form and weld.Depending on the type of alloy, the
weight of its kind located between 2.65 and 2.8 kg/dm3. Aluminum
alloy have in standardization. Categorization is done into two main
groups, namely processed aluminum alloy cast by pouring and alloy
aluminum holding to squeeze on the structure of the cast, had been
wading through a process of squeezing (unfolding, forging,
milling).Based on an increase in power there are two groups of
aluminum alloy that is not able to be hardened or naturally hard
and that can be hardened.Aluminum alloy that can not be gained its
power through the dituakeraskan change the shape at room
temperature, for instance through grinding, forging, perentangan.
But in that stretch is reduced and the material will become more
fragile as the rise in the degree of change form. But reinforcing
the cold can be restored to its original state with the soft
candescance.Aluminum material properties will experience a change
is good when combined with other metals. Copper will increase
violence, magnesium will increase the strength. Selection of
aluminum alloy which is a lot of exciting tours that open up
opportunities to uses of aluminum are more numerous. Mainly to
increase the mechanical robustness of aluminum, then tried with the
road design. But the nature of pure aluminum are retained, such as
the weight of its kind that is low, their rust resistance, heat
conductivity is good, its convenience for modified shape with
good[11] .2.5.3 Heat Treatment Of Aluminum Alloys Aluminum alloy
gained its power through the change form at room temperature, for
instance through grinding, forging, unfolding. However, in that it
spans are reduced and materials will be more fragile in line with
increasing degrees of change form. But reinforcing the cold can be
restored to the original to do a candescance, then it can be done
by warming the aluminum. Figure 2.16 shows the form of aluminum
that has been melting.
Figure 2.16 Molten Aluminium Heated [11] .Through improved
software pemijaran kesudian change the form of aluminum and
aluminum alloys. Granules become more subtle. Thus these materials
become soft and can be stretched Pack. It is only applied when the
material has become too hard and brittle due to the reinforcing
cold. Soft candescance takes place at temperatures between 300oC
and 450oC[5] .2.6 Solidworks Software Solidworks is one type of
software that can be used to create 2-dimensional modeling (2D) and
3-dimensional (3D) quickly and easily. And also to be able to make
a calculation analysis such as stress analysis, flow simulation
fluid, thermal, and other. This Software can create a model unit or
with merangkainya. 2.6.1 Solidworks Simulation SolidWorks
simulation is a special extra for doing simulations such as power,
heat, pressure, and others. To run a simulation, then enter the
required data used umtuk limits of put. SolidWorks flow simulation
is one type of analysis in SolidWorks simulation that aims to
quantify the phenomenon in the flow[12 ].5
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