I - PANEL RADIATOR
Purpose
Investigating the heating power of a panel radiator - used for heating at the buildings- from
room temperature to the steady state on time dependent basis.
Experiment
The experimental set-up is depicted in the figure below.
Experimental set-up includes various type vanes, thermometers, manometer, pump, panel
radiator, flow meter and an electric heater. The heating power of the heater is 2 kW. After
the flow rate of the system reaches a constant value the input and output temperature
values of the water will be recorded periodically.
Question
1) What percentage of electric power of the electric heater transferred to the panel
radiator ?
II- WATER - WATER HEAT PUMP
Purpose
Calculating the COP value of the heat pump by making measurements at the water/water
heat pump and understanding working principle of the heat pumps and the laws of
thermodynamics.
Theoretical Knowledge
Mechanical compressor vapor compression heat pump system works according to the
compression-condensation and expansion-vaporization principles likewise mechanical
compressor vapor compression refrigeration machine. Thus refrigerants are used in the heat
pump applications. The schematic view of a heat pump is shown below.
The refrigerant, whose pressure decreases at the expansion valve, is carried to the
evaporator section by the pipes. The heat load of the environment is removed in the
evaporator section, so the temperature of the refrigerant rises and it vaporizes. When it is
aimed to remove the heat from water, that water is circulated outside of the evaporator or
evaporator is submerged. If more heat transfer rate is desired, the outside water is
circulated in the opposite direction to the refrigerant. Vaporized refrigerant transferred to
the compressor section by the pipes. In the compressor, vaporized refrigerant is compressed
that’s why the temperature and pressure values of the refrigerant increases. The refrigerant
with the high temperature and pressure values carried to the condenser. In the condenser,
the refrigerant gives its heat to the environment which is desired to be heated. When it is
aimed to achieve hot water, water is circulated outside of the condenser or condenser is
submerged. In the condenser section the refrigerant condenses and becomes saturated
liquid. Than refrigerant is sent to expansion valve again and its temperature and pressure
decreases.
Experiment
The main equipments of the water/water heat pump are listed below.
a) Compressor
Brand-Model : Emerson-Copeland- KCE444HAG
Power : 220-230 V,50 Hz
Power Consumption: 252 W
Cooling Capacity: 926 kcal/h
b) Heat Exchanger
Brand-Model: Uğurak 7000
Capacity: 7000 BTU
c) Throttling Valve
Brand-Model: ALCO-TI-MW55
Refrigerant: R134-a
Outlet Diameter: 12 mm
Working Range: -45…+9 oC
d) Filter-Dryer
Brand-Model: ALCO-FDB-052
e) Low and High Pressure Pressurestat
Brand-Model: ALCO-PS2-L7A
f) Manometer
Brand-Model: ALCO MR-206-DS
g) Ampermeter
Brand-Model: SAYPORT DP3-96A
Auxilary Supply: 230-110-415 V
Measurement Range:1-9000/5A
h) Voltmeter
Brand-Model: SAYPORT DP3-96V
Auxilary Supply: 230-110-415 V
Measurement Range:0-600 V
i) Cosψ meter
Brand-Model: SAYPORT DP3-96A
Auxilary Supply: 230-110-415 V
Measurement Range:0.00-1.00 İn/Kap
j) Digital thermometer
12 channel
In this experiment , the water flow rates, which go to the heat exchangers, are
adjusted by the help of vanes and the system is operated. When the system reaches
steady state conditions, the measurement data will be recorded in the tables that are
shown in the following section.
Questions
According to the collected data from the experiment,
a) Compressor power, evaporator and condenser capacities will be calculated
b) COP of the heat pump will be calculated
Table 1 : Temperature Data
No
Definition
T1
Compressor Gas Outlet Temp.
T2
Compressor Gas Inlet Temp.
T3
Condenser Gas Outlet Temp.
T4
Condenser Water Inlet Temp.
T5
Evaporator Water Inlet Temp.
T6
Throttling Valve Outlet Temp.
T7
Condenser Water Outlet Temp.
T8
Evaporator Water Outlet Temp.
Table 2 Compressor Power Data
Definition
Ampermeter
Voltmeter
Cosψ meter
Table 3 Mass flow rates
Definition
Mass flow rate of condenser
Mass flow rate of evaporator
Values
Values
Values
III- AIR CONDITIONING
Humidifying with Water
Fundamentals of Air Conditioning
To choose the right device for air conditioning, it is needed to calculate heating and cooling
loads correctly and certain.
Basic elements for air conditioning are listed below;
1. Temperature ( Heating at winter, cooling at summer
2. Humidity (humidifying at winter, dehumidifying at sumer)
3. Air Movements (circulation)
4. Purification of air (Filtration)
5. Ventilation (Clean air input)
HEAT RECOVERY AIR CONDITIONER EDUCATION SET SCHEME
exhaust
t5
t3
t6
t4
Heat exchanger
t12
Exhaust
damper
Pre heater
humidifier
cooler
t11
t7
t9
t1
t8
t10
t2
inner climate
Final cooler
Fresh air ent.
radiator
fan
TECHNICAL PROPERTIES
1
Fan brand and model
2
Fan motor power and rpm
45 W, 1350 rpm
3
Fan capacity
850 m3/h
4
Preheater power
1055 W
5
Finalheater power
1055 W
6
Humidifier type
Water injection type
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Heatexchanger Type and Material
Aluminum plates
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Heatexchanger Model
BT AL 03 N 021 M T AZ SC
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Dimensions of Heatexchanger
300x300x210
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Heat exchanger series number and width
27 series-7,5 mm
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Damper dimensions
200x230 mm
Experiment
1. Purpose
Observing the changes in the air during the humidifying process.
2. Required Devices and Materials

Air speed meter (anemometer)

Psychrometric chart
3. Question
What is the mass flow rate of the moisture added to the air ?
Measurement Number
Inlet temperature ,
Dry
t1 [0C] , t2 [0C]
Heat exchanger exhaust temp., t3 [0C], t4 [0C]
Cooler hum. ex. Dry temp., t7 [0C], t8 [0C]
Measurement
Velocity of air,
u [m/s]
Specific volume of air,[m3/kg]
Line Voltage, U [V]
Wet
h
ν
ω
THERMAL TREATMENT PROCESSES
Objectives
1) To investigate the conventional heat treatment procedures, such as quenching and tempering,
used to alter the properties of steels.
2) To study the effects of heat treatment on the microstructure and mechanical properties of steels;
microstructure will be investigated and hardness will be measured for heat treated specimens.
Section I: Introduction to Thermal Treatment Processes
Heat treatment is a controlled process used to alter the microstructure of materials such as metals
and alloys to impart properties which benefit the working life of a component, for example increased
surface hardness, temperature resistance, ductility and strength.
1.1. Heat Treatment:
The heat treatment process for steel and steel alloys is composed of three steps:
a) Heating to a temperature at which austenite is formed (austenitizing)
b) Rapid cooling (quenching)
c) Reheating to stabilize structure (tempering)
Austenite is a solid solution of carbon in iron in a face centered cubic (FCC) crystalline structure which
is stable at elevated temperature. The temperature at which austenite formation occurs depends
primarily on carbon content of the steel. This temperature can be determined from the phase
equilibrium diagram for the particular steel composition. The material must be held at the
austenitizing temperature for a period of time to ensure completeness of the phase transformation
and homogeneous structure. The amount of time required is dependent on the size and shape of the
work piece as well as its composition.
After the time required for austenite formation, the material is rapidly cooled by quenching. Most
often, quenching is accomplished by immersing the material in oil or water although air quenching is
also used. Under conditions of rapid cooling, austenite transforms into an unstable (non equilibrium)
phase known as martensite. This phase is a supersaturated solution of carbon in iron in a body
centered tetragonal structure. Martensite is very hard, relatively brittle phase which provides the
ability of strengthening steel to very high levels. Quenching usually results in a structure composed of
martensite plus ferrite (solid solution of carbon in iron in body centered cubic structure) and iron
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carbide (cementite). The proportions present after quenching depend on carbon content and cooling
rate. Higher carbon content and rapid cooling tend to produce larger proportions of martensite.
Martensite is hard and brittle. In order to reduce brittleness, increase ductility, and relieve internal
stresses from rapid cooling step, the material is subjected to a second heating operation known as
tempering. The temperature for the tempering step must be below the austenite transformation
temperature and is usually between 400F and 800F. The resultant properties of the steel after
tempering depend on the time allowed for tempering as well as the temperature.
The microstructure produced by any of the above heat treatments can be deduced using Continuous
Cooling Transformation (CCT) diagrams, which are directly related to the Time Temperature
Transformation (TTT) diagrams for the specific steel being treated. Such a TTT/CCT diagram for
eutectoid steel is shown in Figure 1. Fe-C phase diagram is given at Fig.2.
Fig.1. The dashed lines form TTT diagrams and the solid lines form the CCT diagrams. It can be seen
that CCT diagram can be obtained by moving the TTT curves a little to the downward right.
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Figure 2: Iron-Carbon Phase Equilibrium diagram. (Source: Material Science and Metallurgy, 4 th
edition, Pollack, Prentice-Hall 1988)
1.2. Difference between TTT and CCT diagrams
The essential difference between both the diagrams is the method of cooling. In TTT diagrams, after
cooling to a transformation temperature, you keep the temperature constant until the
transformation of austenite to the required transformation product (usually pearlite or bainite) is
complete and then cool to the room temperature.
In CCT diagrams, there is continuous cooling i.e. there is no holding of temperature. The components
are cooled at a constant or varying rates. The end products are usually martensite or pearlite
depending on the cooling media as well as the material of components.
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Section II: Introduction to Characterization Tests
2.1. Hardness Testing
Hardness tests measure the resistance to penetration of the surface of a material by a hard object.
The depth of penetration is measured by the testing machine and converted to a hardness number.
2.2. Microscopical Examination
The microstructural study of a material can provide information regarding the morphology and
distribution of constituent phases as well as the nature and pattern of certain crystal imperfections.
Optical metallography is a basic tool of material scientists, since the equipment is relatively
inexpensive and the images can be obtained and interpreted easily. Distribution and morphology of
the phases can be studied and, if their properties are known, a quantitative analysis of the
micrographs provides some information about the bulk properties of the specimen. A limited study
of line and surface informations is also possible with the optical microscope. In order to obtain
reproducible results, with good contrast in the image, the specimen surface is polished and
subsequently etched with appropriate reagents before microscopic examination. In a polished
specimen, the etching not only delineates grain boundaries, but also allows the different phases to
be distinguished by differences in brightness, shape, and color of the grain.
Differences in contrast may result from differences in light absorption characteristics of the phases.
Etching results in preferential attack or preferential colouring of the surface. The preferential attack
is electrochemical corrosion; it is well known that different materials corrode at different rates. Grain
boundaries are often anodic to the bulk metal in the interior of the grain and so are etched away
preferentially and delineated. Staining is produced by the deposition of solid etch product on the
specimen surface. This is formed by chemical reaction between the etchant and the specimen. Under
favorable conditions the use of a proper etchant enables the identification of constituents. Failure
analysis depends a great deal on metallographic examination.
Microstructural examination can provide quantitative information about the following parameters:
1) The grain size of specimens
2) The amount of interfacial area per unit volume
3) The dimensions of constituent phases
4) The amount and distribution of phases.
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2.2.1. Specimen preparation for Microscopical Examination
Grinding
A small piece of specimen is cut by a metal-cutting-saw. After cutting operation, burrs on the edges
of the specimen should be carefully removed by a fine file or coarse grinding paper. The silicon
carbide grinding papers are held flat in a unit containing water facility for lubrication purpose. Each
unit contains four grades of papers, starting with grade 400 (coarse) and finishing with grade 1200
(fine). Grinding of the work piece is done by starting with the coarse papers and then continuing with
the fine papers. In each stage, grinding is done by rubbing the specimen backwards and forwards on
the grinding paper in one direction only, until the surface is completely ground, that is, until only
grinding marks due to this particular paper can be seen to cover the whole surface.
The specimen is washed thoroughly to remove coarse silicon carbide particles before proceeding to a
finer paper. The direction of grinding is changed from paper to paper, so that the removalof previous
grinding marks is easily observed. The extra time spent on each paper should be increased as the
finer papers are used. At the end of the grinding sequence, the specimen is washed thoroughly and
dried. Now, the specimen is ready for polishing.
Polishing
The polishing is done on rotating wheels covered by a special cloth. Alumina is employed as polishing
agent. The 1-micron size is commonly used, but the total polishing time shortened by starting on the
7 or 3 micron grade. The pad should be kept well supplied with lubricant. The specimen should be
held firmly in contact with the polishing wheel, but excessive pressure should be avoided. During
polishing the specimen should be rotated or moved around the wheel so as to give an even polish.
The specimen should be thoroughly cleaned and dried between each wheel.
Etching
Before etching, it is essential to ensure that the polished surface is grease and smear free. If the final
polishing has involved the use of magnesia ( in the form of an aqueous paste of fine magnesia) or
alumina (in the form of an aqueous suspension of fine alumina), then thorough washing followed by
drying off with acetone or alcohol will give a suitable surface, although it must not be fingered
afterwards.
Etching is generally done by swabbing. Etching times will vary from specimen to specimen, however,
a good general, procedure is to observe the surface during etching, and to remove the specimen
when evidence of the grains first appears. Microscopical examination will then reveal whether the
degree of etching is sufficient. Further etching can then follow to strengthen up the details as
required. After each etching, the specimen should be thoroughly washed in running water, followed
by drying off with acetone or alcohol.
* As a guide the following etchants are commonly used:
Alcoholic Ferric Chloride -copper alloys
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Mixed Acids -aluminum alloys
Nital (ethyl alcohol+ 2% HN03) -iron and steel
Dilute HCI -zinc alloys
2.3. Roughness Measurements
Roughness is a measure of the texture of a surface. It is quantified by the vertical deviations of a real
surface from its ideal form. If these deviations are large, the surface is rough; if they are small the
surface is smooth. Roughness is typically considered to be the high frequency, short wavelength
component of a measured surface (see surface metrology).Roughness plays an important role in
determining how a real object will interact with its environment. Rough surfaces usually wear more
quickly and have higher friction coefficients than smooth surfaces. Roughness is often a good
predictor of the performance of a mechanical component, since irregularities in the surface may
form nucleation sites for cracks or corrosion. Although roughness is usually undesirable, it is difficult
and expensive to control in manufacturing. Decreasing the roughness of a surface will usually
increase exponentially its manufacturing costs. This often results in a trade-off between the
manufacturing cost of a component and its performance in application.
Measurement. Roughness may be measured using contact or non-contact methods. Contact
methods involve dragging a measurement stylus across the surface; these instruments include
profilometers. Non-contact methods include interferometry, confocal microscopy, electrical
capacitance and electron microscopy.
Principle of a contacting stylus instrument profilometer: A cantilever (1) is holding a small tip (2) that
is sliding along the horizontal direction (3) over the object's surface (5). Following the profile the
cantilever is moving vertically (4). The vertical position is recorded as the measured profile (6) shown
in light green.
6
Sketch depicting how a probe stylus travels over a surface.
For 2D measurements, the probe usually traces along a straight line on a flat surface or in a circular
arc around a cylindrical surface. The length of the path that it traces is called the measurement
length. The wavelength of the lowest frequency filter that will be used to analyze the data is usually
defined as the sampling length. Most standards recommend that the measurement length should be
at least seven times longer than the sampling length. The assessment length or evaluation length is
the length of data that will be used for analysis. Commonly one sampling length is discarded from
each end of the measurement length.
Roughness Parameters. Each of the roughness parameters is calculated using a formula for
describing the surface. There are many different roughness parameters in use, but Ra is by far the
most common. Other common parameters include Rz, Rq, and Rsk. Some parameters are used only in
certain industries or within certain countries. For example, the Rk family of parameters is used mainly
for cylinder bore linings, and the motif parameters are used primarily within France. Since these
parameters reduce all of the information in a profile to a single number, great care must be taken in
applying and interpreting them. Small changes in how the raw profile data is filtered, how the mean
line is calculated, and the physics of the measurement can greatly affect the calculated parameter.
Amplitude Parameters. Amplitude parameters characterize the surface based on the vertical
deviations of the roughness profile from the mean line. Many of them are closely related to the
parameters found in statistics for characterizing population samples. For example, Ra is the
arithmetic average of the absolute values and Rt is the range of the collected roughness data points.
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Section III: Heat Treatment Exercise
1. Supply three SAE 1040 or 1080 or 4140 specimens (and the Jominy Bar). Austenitize these at
proper temperature (look at Fe-C phase diagram) for 1 hour. Allow adequate time for the crucible to
heat to the temperature of the furnace (about 10 minutes). A total of 1 hour heating time should be
adequate allowing roughly 45-50 minutes of soaking.
2. Normalizing - Rapidly remove one specimen and allow it to cool in air on a ceramic base.
3. Quench Hardening – Rapidly remove four specimens and quench them in water at room
temperature.
4. Tempering – Reheat three of the water quenched specimens to 500 0C in another furnace for 30
minutes, then remove it and allow it to cool in air to room temperature.
Section IV: Tests and Results
1. Determine the Rockwell hardness values for each of the heat treated specimens after
cleaning one of the surfaces with sand paper to remove any hard carbon deposits that may
have formed on the surface. Take 5 readings on each sample.
2. Record these readings in Table 1.
Table 1: Hardness Rockwell C for heat treated AISI 1080 Steel
Measurement
Number
1
2
3
4
5
Mean Value
Normalized
Quenched
Tempered at
500 0C
3. Examine each specimen and sketch typical microstructure by means of optical microscopy.
Specimens are going to be polished and etched as explained above.
4. Put microstructure photos with correct magnification bar.
5. Measure the surface roughness after each grinding step.
6. Record these readings in Table 2.
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Table 2. Roughness measurement of normalized steel
Measurement
Number
1
2
3
Mean Value
After 400 grit After 800 grit After
grinding
grinding
polishing
Section V: Discussion
1. Discuss the expected microstructures and properties for each of the specimens based on
the appropriate TTT and/or CCT diagrams for the cooling sequences applied.
2. Discuss the relationship between heat treatment and the resulting hardness and
microstructure obtained in this experiment.
3. Compare and comment on the experimental results obtained with respect to the
expected microstructure and hardness results.
4. When Austempering steel, after the 30 minutes in the 400°C bath the specimen is
removed from the bath and can be either quenched in water or allowed to air cool at
room temperature. Will these two procedures produce different results? Explain.
5. What is decarburization? What causes it and how is it prevented? How does it affect the
properties of heat treated steels?
6. What is purpose the surface roughness measurement?
7. What are the different methods to measure the roughness of a surface?
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