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Performance Analysis of Pedestal and Table fans

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Abstract and Figures

The pedestal and table fans are widely used to provide air mixing and comfort region in enclosed spaces. There are different brand of fans with various blade shapes, sizes and number of blades which lead to different level of performances. Aerodynamic characteristic is one of the important aspect which affects the fan performance. Performance of four different type of fans were analysed through the experimental measurements of velocity distribution, power consumption and angular velocity. A test rig was constructed with suitable instrumentation and integrated using a computerised data acquisition platform to acquire axial flow velocity measurements at each plane. The velocity distribution was measured at sufficient number of planes with different regulator position of the fan. Key parameters such as the flow rate, kinetic energy, linear momentum and the jet diameter were calculated from the experimental data. Different velocity distributions were obtained for different type of fans in the analysis of the data. Iso-velocity lines were obtained to analyse the spread of the velocity. Results show that the velocity profiles of the fans depend on the regulator position and blade parameters such as blade shape and material. It is also found that the overall energy efficiency of the fan depends on the angular velocity for different regulator positions. Further the incremental flow rate was also calculated to analyse the percentile change in flow rate for each regulator position. The impact on the performance when the fan was set to oscillate is also discussed in this paper. The results of the present study indicate the complexity of the influence of various parameters on the performance of the fan such as blade shape, angular velocity and power consumption and the necessity of a detailed experimental analysis of the velocity distribution of the fan for performance analysis.
Content may be subject to copyright.
Annual Sessions of IESL, pp. [1 - 10], 2016
© The Institution of Engineers, Sri Lanka
Performance Analysis of Pedestal and Table fans
A.G.T. Sugathapala, R.A.C.P. Ranasinghe, B. Anthujan, S. Srikandaraj and
V.Vipulan
Abstract: The pedestal and table fans are widely used to provide air mixing and comfort region in
enclosed spaces. There are different brand of fans with various blade shapes, sizes and number of blades
which lead to different level of performances. Aerodynamic characteristic is one of the important aspect
which affects the fan performance. Performance of four different type of fans were analysed through
the experimental measurements of velocity distribution, power consumption and angular velocity. A
test rig was constructed with suitable instrumentation and integrated using a computerised data
acquisition platform to acquire axial flow velocity measurements at each plane. The velocity distribution
was measured at sufficient number of planes with different regulator position of the fan. Key parameters
such as the flow rate, kinetic energy, linear momentum and the jet diameter were calculated from the
experimental data. Different velocity distributions were obtained for different type of fans in the
analysis of the data. Iso-velocity lines were obtained to analyse the spread of the velocity. Results show
that the velocity profiles of the fans depend on the regulator position and blade parameters such as
blade shape and material. It is also found that the overall energy efficiency of the fan depends on the
angular velocity for different regulator positions. Further the incremental flow rate was also calculated
to analyse the percentile change in flow rate for each regulator position. The impact on the performance
when the fan was set to oscillate is also discussed in this paper. The results of the present study indicate
the complexity of the influence of various parameters on the performance of the fan such as blade shape,
angular velocity and power consumption and the necessity of a detailed experimental analysis of the
velocity distribution of the fan for performance analysis.
Keywords: Velocity distribution, Iso-velocity, Energy efficiency, Test rig, Pedestal fan, Table fan
1. Introduction
Pedestal and table fans are widely used to
produce a comfortable environment in enclosed
spaces. There are different brands of fans
available in the market with various blade
shapes, sizes and number of blades as well as
different levels of performances [1]. Globally
there is an increasing effort to improve the
energy efficiency of appliances as an effective
mitigation option in responding to the growing
energy and environment issues [3].Initially a
testing procedure was developed in order to
conduct the performance analysis of pedestal
and table fans. A test rig was created with
appropriate sensors to conduct the experiments.
Then, a testing protocol was developed with
respect to the results gained from the
experiments. Finally a suitable performance
grading scheme was developed from the
experimental analysis considering the different
factors such as service factor, incremental flow
rate, power factor, and oscillation factor.
2. Experimental Investigation
2.1 Test rig setup
Figure 1- Test rig construction
Eng. (Dr.) A.G.T. Sugathapala, B.Sc. Eng. (Moratuwa),
Dr. Eng. (Cambridge,UK), Senior Lecturer of Mechanical
Engineering, Department of Mechanical Engineering,
University of Moratuwa.
Eng. (Dr.) R.A.C.P. Ranasinghe, B.Sc. Eng. (Moratuwa),
Dr. Eng. (Loughborough, UK), Senior Lecturer of
Mechanical Engineering, Department of Mechanical
Engineering, University of Moratuwa.
Mr. B. Anthujan, B.Sc. Eng. (Moratuwa)
Mr. S. Srikandaraj, B.Sc. Eng. (Moratuwa)
Mr. V.Vipulan, B.Sc. Eng. (Moratuwa)
Velocity measurements in each plane should be
obtained at several points in both X and Y
(horizontal and vertical) directions. A test rig as
shown in Figure 1 was created where the
horizontal bar could be moved along the Y axis
direction and the sensors could be moved on the
cross bar along the X axis direction. Similarly a
vertical bar was used to obtain the velocity
measurements along the Y axis. The setup shows
a single sensor mounted on both the vertical and
the horizontal bar but a total of five sensors were
mounted on each and readings were taken
simultaneously.
2.2 Instrumentation
The velocity measurements were obtained in
different planes using hot wire anemometers
which have the resolution of 0.01 m/s and the
range of 0.2 to 20 m/s and they were collected
using a DAQ device. The velocity measurements
were cross-checked using a handheld
anemometer which has the resolution of 0.001
m/s and the range of 0 to 30 m/s. The current,
voltage, power consumption, frequency, and
power factor were measured using a Handheld
Tester. The humidity and temperature of the
testing facility was measured using humidity
and temperature meter. The angular velocity of
each fan was measured using digital tachometer
which has the resolution of 0.1.
As shown in Figure 2 a cross line laser level
which projects horizontal and vertical lines onto
flat surfaces, along with an additional vertical
line, 90 degrees from the cross line and a laser
distance measuring meter were used to align the
fans and sensors to particular position.
The oscillation angle was measured with use of
a laser level. The laser level was mounted on the
front cage hub of the fan and the range swiped
by the laser line was measured by means of
marking starting and ending edge of the sweep.
2.3 Software interface
The sensors were logged in to LabVIEW based
DAQ device to obtain real time data and
simultaneous average values. Continues
sampling was preferred over other sampling
methods in order to obtain reliable continuous
value and consider the whole range of values
obtained at one particular point. All five sensors
were monitored separately and simultaneously
in order to make sure the sensors are acquiring
reliable values.
3. Preliminary experimental
investigation
The placement of the fan and the dimensions of
the test chamber were decided based on a
comprehensive analysis of the entire flow
pattern around several fans. Accordingly,
aiming to decide the minimum required
distances from the fan to the front walls, back
walls and side walls such that their effects on the
fan performances will be negligible.
3.1 Determination of the back wall distance
from the fan blade center
In order to minimise the wall effect at the fan
inlet the fan blade center was kept at a distance
of 2m from the wall. The velocities were
measured at planes situated in 1D (40cm), 2D
(80cm) and 3D (120cm) respectively from blade
center where D represents the diameter of a fan.
The resulting velocity distributions in each plane
were obtained. According to the velocity
analysis the inlet velocity gradually reduces
with distance and at 3D (120cm) away from the
plane the magnitude of the velocity profile
becomes nearly equal to zero. Hence with a 25%
allowance the distance behind the fan was
maintained at 3.75D (150cm) between the wall
and the blade center in order avoid the impact of
the back wall.
Figure 2 - Cross line laser level
3.2 Determination of the fan height
Figure 3 - Jet Radius at each plane
The height of the fan blade center for experiment
was decided based on the largest jet diameter
obtained in the tested planes at different
regulator settings for different fans. From the
analysis of experimental results it could be
observed that the jet diameter increases in each
plane as the distance between the plane and the
blade increases. The velocity measurements
were taken at 13 planes which were 0.2D, 0.25D,
0.5D, D, 2D, 4D, 6D, 8D, 10D, 12D, 14D,16D
and18D this is shown in Figure 3.Measurements
obtained from two fans at the highest regulator
position were used to determine the fan blade
center height.
The maximum jet radius was considered in
order to obtain the blade center height the fan
should be placed for the test. An additional 25%
allowance was given for the jet radius to avoid
the impact of the floor and ceiling. From the
experiment the fan blade center was obtained as
3.75D (150cm). Since the thickness of the shear
layer cannot be measured using the available
instrumentation, a thorough analysis should be
done to analyse the thickness of the shear layer
and its behaviour due to the effects created by
the walls.
3.3 Determination of the dimension of
testing facility
Figure 4 - Maximum velocity obtained at each
plane for fan type A and B
Maximum length of the testing facility should be
determined by the magnitude of the minimum
velocity that should be measured in the
experiment. Velocity measurements were taken
until the minimum velocity is reached as shown
Figure 4. The velocity measurements were taken
up to 18D distance from the blade center and the
velocity reaches the minimum velocity at 20D.
The velocity at 20D was estimated by
interpolating the prevailing data obtained.
Further the rate of kinetic energy reduces
drastically with distance until the plane at 18D
from the fan blade center. Hence for this
experiment the downward length required was
determined as 25D including a 25% allowance.
Hence with the backward wall distance a total
minimum distance of 28.75D should be available
as length of the test facility.
3.4 Determination of the optimum gap
between measurement points
Velocity measurements were analysed at
different gaps between measuring points in
order to determine the optimum distance
between measurement points. The flow rate was
calculated with 11 radial points, 6 radial points,
and 3 radial points. When the point gap is
increased, some velocity fluctuations will be
missed, so that the flow rate values will be
changed. The probability of large velocity
fluctuations being omitted is high when
considering 3 radial points comparing with 6
and 11 radial points. Increasing the point gap
between measuring points will reduce the
resolution of the data obtained but having a
higher resolution will result in high time
consumption for measurements. Hence for the
experiment, 6 measurements per radius was
considered as reliable.
3.5 Determination of time duration for
velocity measurement
Figure 5 - Velocity measurement with time
An optimum time duration has to be determined
for the measurement velocity in order to capture
the complete pattern of the velocity change. For
this, velocity measurements were obtained for
10 minutes for a particular setting of a fan and
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Distance (y/D)
Distance (x/D)
0
1
2
3
4
5
6
7
8
0246810 12 14 16 18 20 22 24
Velocity (m/s)
Distance (x/D)
1.24
1.26
1.28
1.30
1.32
1.34
1.36
1.38
1.40
1.42
1.44
1.46
0 2 4 6 8
Time averaged velocity
(m/s)
Time interval (minutes)
the time averaged velocity magnitudes were
calculated for different time interval. The rate of
increase of the velocity decrease to
0.02(m/s)/minute after the three minute time
interval and the rate continues to decrease as
shown in Figure 5. Hence for this experiment the
minimum time of 3 minutes was taken as time
interval to measure the velocity at each point.
More accurate readings could be obtained if
measurements are taken for more than 3 minutes
but the time duration for the whole experiment
would increase hence the minimum best time
span was selected for this experiment.
3.6 Determination of number of
measuring radii on each plane
Air velocity readings were taken along four
symmetrically located radii. This is in order to
obtain better accurate values at each radial point.
Even though the fan shaft is set parallel to the
plane of the sensor head there will be minor
alignment problem which will result in non-
symmetric velocity distribution. Non symmetric
values will also result due to the fan cage design
and the cage hub.
3.7 Obtaining steady state of fans
The fan should achieve a steady state before any
experimental measurements being taken.
Existing standards for fans such as the IEC 60879
defines the steady based on the temperature of
the motor where steady state is achieved when
the temperature change with time is 1/hour.
The experiment was performed to analyse the
temperature change over time from 0th regulator
position to each of the other regulator positions
and to analyse the temperature change over time
when switching between each regulator
position. The time required to become steady
from 0th regulator position to 1st, 2nd, and 3rd
regulator position were obtained as 50 minutes
and the time required to become steady from 1st
regulator position to 2nd regulator position and
2nd regulator position to 3rd regulator position
were obtained as 30 minutes.
3.8 Proposed test rig setup
Figure 6 shows the test rig setup obtained
through the preliminary analysis of the flow
around the fan. This defined setup is used to
conduct the experiment for the performance
analysis. All the dimensions are defined in terms
of the diameter (D) of the fan blade.
Figure 6 - Defined test rig setup
4. Measurements
4.1 Power consumption details and
angular velocity
Table 1 - Power and angular velocity
measurements
Each fan was differentiated through the power
output measurements and the angular velocity
obtained for each regulator settings as shown in
Table 1.
4.2 Velocity Distribution
The velocity distributions given are
axisymmetric since the velocity of each points
are average velocity values calculated from the
readings taken at all four perpendicular radii.
This is shown in Figure 7 for Fan A however a
non-symmetric behaviour is observed in each
plane of measurement. The non-symmetric
patterns are smoothed out in averagevelocity
distribution. Nevertheless the velocity
distribution shown in Figure illustrate some
important characteristics of flow such as the jet
diameter, peak velocity and increments between
each regulator position of fan A. All velocity
measurements were taken with the fan cage to
represent the domestic usage.
Fan
Type
Curren
t (A)
Volta
ge(V)
Frequenc
y(Hz)
Power
consu
mptio
n(W)
Powe
r
factor
Rotati
onal
speed
(RPM)
Annual
Power
consum
ption
(kWh)
1 196.1 242.4 50.1 47.86 1 1231 138.87
2 211.6 243.5 50.1 52.1 1 1310 153.17
3 249.1 240.7 50.12 56.54 0.946 1370 165.23
1 173.2 221.6 50.2 35.44 0.945 970 103.6
2 185.1 219.8 50.15 40.14 0.968 1100 116.7
3 210.2 224.6 50.15 47.57 1 1230 139.5
1 150.5 218.8 50.25 32.45 0.97 940 94.57
2162 226.4 50.15 36.26 0.988 1080 106
3 174.5 225.8 50.1 38.84 1 1240 114.2
1 149 .9 210 50.1 30.67 0.968 1235 90.18
2 160.2 215.2 50.05 34.09 0.991 1310 97.71
3 184.7 215.1 50.2 38.88 0.992 1375 114
A
B
C
D
Figure 7 - Velocity distribution of Fan A
4.2 Velocity measurements for oscillating
configuration of fans
Table 2 - Measurement for oscillation
configuration
The average velocity values obtained from the
time average of velocity magnitudes obtained
from the data as shown in Table 2. The sensor
was set to capture data for 5 minutes.
5. Results
The flow rate, rate of momentum, rate of kinetic
energy, and velocity head were calculated for
each fan in different planes and were compared
each other.
Figure 8 - Variable dimensions for calculation
Fan Type Regulator
Oscillations
Per minute
Average
velocity
Oscillation
Angle
1 4.14 0.54
2 4.73 0.55
3 5.21 0.66
1 3.02 0.47
2 3.52 0.52
3 4.28 0.6
1 3.41 0.36
2 4.09 0.38
3 4.8 0.45
1 5.54 0.54
2 5.9 0.55
3 6.13 0.66
90
95
90
75
A
B
C
D
5.1 Volume flow rate
Figure 9 - Volume flow rate of Fan A
The volume flow rate can be expressed as
 
   
 , where the r0
represents the radius of the jet in the particular
distance from the fan blade,  represents the
radial increment, ri represents the radial position
in ith number of velocity measurement, ui
represents the velocity at position ri. This is
shown in Figure 8.
Figure 9 shows flow rate of fan A. The flow rate
was calculated in different planes, and while
comparing the flow rate of the tested fans, for
fans A, C, D the maximum flow rate is obtained
at the distance of 10D, and for fan B the
maximum flow rate is obtained at the distance of
8D. The maximum average flow rate is obtained
around 4 (3.57 to 4.41) times greater than the
flow rate near the rotor. Most of the cases the
flow rate increases with the regulator position.
For fan-A in some particular planes the flow rate
reduces from one plane to another. For other
three fans the flow rate increases with increment
of regulator position. For each cases the velocity
in center of the blade is being increased from one
regulator position to another position though for
Fan-A in particular planes the air jet is being
narrowed because of high rate of momentum.
As mentioned above, the flow rate of fan-B
reduces after the distance of 8D, but at the
distance of 14D there is an increment in flow rate
and after that the flow rate decreases. As the
experiment was performed until 18D for fan-A
and fan-B, at the regulator position 2 there is an
increment in flow rate from 16D to 18D for both
fans. In regulator position 1 and 3 there is no
increment in flow rate after 14D for both fans A
and B. In order to analyse the whole pattern, the
experiment should be performed until the flow
rate becomes zero.
5.2 Rate of momentum
Figure 10 - Rate of momentum of Fan A
The rate of momentum can be expressed as
    

 , where the
r0 represents the radius of the jet in the particular
distance from the fan blade,  represents the
radial increment, ri represents the radial position
in ith number of velocity measurement, ui
represents the velocity at position ri, and
represents the density of the air.
While comparing the rate of momentum of each
fan, fan-A and fan-B have the higher rate of
momentum than the fan-C and fan-D. For each
fan the rate of momentum is almost constant
near the fan rotor and reduces after a certain
distance. Though, in some points the rate of
momentum have some peak values after
continuous decrement.
The Figure 10 shows the rate of momentum of
fan A in different planes and in each fan there is
an initial increment in rate of momentum near
the rotor because of converging jet. The
maximum rate of momentum is obtained at 0.2D
for fan-A and fan-C, at 0.25D for fan-B, at 1D for
fan-D. For fan-B and fan-D the rate of
momentum was not calculated before 0.25D
because of the fan safety cage. If the rate of
momentum was obtained before 0.25D the
maximum rate of momentum may be obtained
before 0.25D for fan-B and before 1D for fan-D.
5.3 Rate of kinetic energy
Figure 11 - Rate of Kinetic Energy of Fan A
The rate of kinetic energy can be expressed as
    
 , where
the r0 represents the radius of the jet in the
particular distance from the fan blade, 
represents the radial increment, ri represents the
radial position in ith number of velocity
measurement, ui represents the velocity at
position ri, and represents the density of the
air.
The Figure 11 shows the rate of kinetic energy of
fan A and the rate of kinetic energy continuously
decreases for each fan. The kinetic energy should
be increased until the je diameter reaches its
minimum value. As the minimum jet diameter
for fan-A, fan-B, fan-C becomes at the minimum
plane accounted for the measurements. For fan-
D the minimum air jet diameter becomes at 1D,
though the rate of kinetic energy at 1D is less
than rate of kinetic energy at 0.25D and 0.5D. So,
the minimum jet diameter of fan-D should come
before 0.25D. While comparing the rate of kinetic
energy of each fan, fan-A and fan-B have the
higher rate of kinetic energy than fan-C and fan-
D.
5.4 Velocity head
Figure 12 - Velocity head of Fan A
The Figure 12 shows the velocity head of fan A
and while considering the velocity head, for each
fan the velocity head decreases continuously.
The velocity head near the rotor of the fan-A and
fan-B is much higher than the velocity head of
fan-C and fan-D.
5.5 Service factor
Figure 13 - Variation of service factor along
downstream of Fan-A
The service factor is defined as the flow rate per
unit power consumption [2]. As the flow rate has
been calculated in different planes for each
regulator positions, the service factor also can be
calculated in different planes for each regulator
positions. While consider the service factor plot,
it can be seen that the pattern of the service factor
varies like the pattern of flow rate varies for each
fan, because there is no variation in power
consumption for different planes. Figure 13
shows the variation of service factor for Fan A.
5.6 Overall efficiency
Overall Efficiency = 

The overall efficiency can be defined as fluid
power output by electric power input. Overall
efficiency of each fans are shown in Table 3. The
overall efficiency of fan-A is much higher than
other fans at regulator position 3. For fan-A the
overall efficiency is above 20 percentage at each
regulator positions and for fan-B the overall
efficiency is above 20 percentage at regulator
position 3. In other cases the overall efficiency is
less than 20 percentage. For ceiling fans mostly
the overall efficiency is less than 20 percentage.
Table 3 - Overall efficiency of tested fans
Fan type
Regulator
position
Overall
efficiency
Fan-A
1
21.54
2
24.71
3
25.27
Fan-B
1
13.21
2
18.59
3
24.83
Fan-C
1
5.94
2
9.58
3
14.08
Fan-D
1
6.75
2
7.44
3
8.64
5.7 Iso-velocity lines
Figure 14 - Iso-velocity lines of Fan A
The velocity distributions of the four fans were
measured in different planes, and according to
the velocity profile, different iso-velocity lines
were obtained as shown in the Figure 14 which
was obtained for fan A. Further considering the
0.5 m/s iso-velocity line, for fan A and B the jet
is developed beyond 1.8 D in radial distance of
the fan, but in fans C and D the jet is developed
within 1.8 D. Hence, for fans A and B the area
covered by 0.5 m/s will be higher than the fans
C and D. The maximum velocity of each fan is
obtained near the rotor plane, and it varies from
fan to fan. Further the jet diameter in each
planes, downstream distance, and the area
where the velocity is greater than a particular
value can be obtained from the above iso
velocity lines.
5.8 Velocity distribution and its impact on
comfort while oscillation
While considering the oscillation of the fan, the
velocity in a particular position varies with time
according to the oscillation speed and oscillation
angle. As a person is seated in a particular
position, the comfort level of the person is being
decided by the air temperature, humidity, air
speed, metabolic rate and clothing insulation. As
the air temperature, humidity, metabolic rate,
and clothing insulation does not vary a lot in a
particular time, according to the air speed the
comfort region can be changed. The minimum
velocity required for the thermal comfort
depends on other factors.
In Sri Lankan context, as the experiments were
performed in the average temperature of 30 °C
and the average humidity of 70 percentage, the
minimum air speed required for a person who is
involved in sedentary work is 0.6 m/s as
discussed in the research “Orientation of roof
and openings: Their influences on indoor
thermal comfort of single storey houses” [5].
The percentage of time where the person is in the
comfort zone can be defined by the percentage
of time where the air speed is greater than 0.6
m/s. The area covered by the fan will depend on
the oscillation angle of the fan where the area
will be proportional to the oscillation angle. In
order to analyse the variation of air velocity and
the percentage of time where the air speed is
greater than 0.6 m/s, the sensor was mounted in
the centre of the fan and in 4D from the rotor
plane.
5.9 Influencing factors and Performance
grading
The Performance grading of a fan shall be
determined by four main factors such as service
value, incremental flow rate, power factor and
oscillation factor.
5.9.1 Service value
The service value is defined as the air flow rate
per unit electric power consumption [2]. The
flow rate and the power consumption varies
with the different regulator positions. In order to
incorporate the service value in performance
grading, simple average of each service value
relevant to the regulator position was obtained.
5.9.2 Incremental flow rate
The incremental flow rate is defined as the flow
rate change from one regulator position to the
next regulator position. If there is N regulator
settings for a particular fan, there will be N-1
incremental flow rate. In order to incorporate the
incremental flow rate in performance grading,
simple average of all incremental flow rate can
be used. If the flow rate in ith regulator position
is higher than the flow rate in (i+1)th position, the
flow rate change will be decrementing flow rate.
Though, when the average incremental flow rate
is calculated the decrementing flow rate will
give a penalty, though there will be an
incremental flow rate as overall.
5.9.3 Average power factor
Power factor, which is the ratio between real
power and apparent power, measured for each
regulator setting is used to estimate the average
power factor of the fan as

= 


Where N = number of regulator setting
 = power factor at  regulator setting
5.9.4 Oscillation factor
Oscillation factor was determined by
considering two different factors such as the
comfort factor which indicates the percentile of
time where the velocity is greater than minimum
required velocity for thermal comfort and the
angle factor which indicates the area covered by
the fan. As the velocity distribution for
oscillation was analysed in 4D from the rotor
plane of fan, according to the air temperature
and humidity the minimum required velocity
was decided as 0.6 m/s. As the area covered by
the fan is proportional to the oscillation angle,
the oscillation angle was considered for the
oscillation factor.
5.9.5 Performance grading
In order to propose a performance grading, for
the average service value in a particular plane,
the maximum service value of the four fans was
identified and a predetermined value was given
with a 25 percentage allowance of the maximum
value. Marks allocated for the service value is
defined through a linear scale from zero to the
predetermined value. If the average service
value is zero the marks for the average service
value will be zero and if the average service
value is equal or greater than the predetermined
value the marks for the average service value
will be 100.
In order to get the marks of incremental flow
rate, the maximum incremental flow rate of four
fans was identified and a predetermined value
was given with a 25 percentage allowance of the
maximum value. Marks allocated for the
incremental flow rate is defined through a linear
scale from zero to the predetermined value. If
the average incremental flow rate is zero the
Marks for the average incremental flow will be
zero and if the average incremental flow is equal
or greater than the predetermined value the
Marks for the average incremental flow will be
100.
Marks allocated for the power factor was
defined through a linear scale from a
predetermined value. If the average power
factor is equal or less than the predetermined
value, the Marks for the average power factor
will be zero and if the average power factor is
equal to one the Marks for the average power
factor will be 100.
In order to give marks for oscillation factor, the
comfort factor and angle factor were considered.
While giving marks for the comfort factor, if the
percentile is zero the marks will be zero and if
the percentile is equal or greater than 0.75 the
marks will be 100. In between 0 to 0.75 the marks
will be allocated linearly from zero to 100. The
value 0.75 is a predetermined value with
maximum expectation. While giving marks for
the angle factor, if the angle is equal or less than
60 degree the marks will be zero and if the angle
is equal or greater than 100 degree the marks will
be 100. In between 60 degree to 100 degree the
marks will be allocated linearly from 0 to 100.
The value 60 degree and 100 degree are
predetermined values. Finally the oscillation
factor was calculated by combining both the
comfort factor and angle factor by giving a
contribution of 0.75 and 0.25 respectively.
The performance grading shall be estimated by
taking the contribution from each factor which
indicates the performance of fan. As the flow
rate and the power consumption is the most
important factor 70 percent marks was allocated
for the average service value, 10 percent marks
for average incremental flow rate, 10 percent
marks for the average power factor, and 10
percent marks for the average oscillation factor.
So the total performance grading can be given by
the expression:
Performance grading = 0.7 × + 0.1 × Δ +
0.1×  + 0.1× .
Figure 15 - Performance grading at each plan of
measurement
The performance grading of each in different
planes is shown Figure 15. The performance
grading varies from plane to plane for each fan,
though it doesn’t show a big variation until the
distance of 6D. After that as the flow rate of Fan-
B reaches its maximum flow rate at the distance
8D, and other three fans reached their maximum
flow rate at the distance of 10D, the performance
grading varies significantly. In order to analyse
the performance of different fans, it would be
better to analyse the variable factors within the
distance of 6D.
6. Conclusions
The main objective of this research work is to
identify parameters which affects the
performance of the pedestal and table fans and
determine an effective method to incorporate the
critical performance factor in to an equation in
order formulate a suitable performance rating
method. Another important objective is to
develop a testing protocol which was developed
through experimental analysis. During the first
phase of the study a suitable testing protocol
was developed and validated through
experimental analysis. Through the analysis the
following has been identified as important
aspects of this research in the development of
the testing protocol developed.
The minimum dimensions of the testing
facility and the guidelines for the alignment
and placement of the blade center were
determined through experimental methods.
Suitable methods to measure the required
parameters were developed through
experimental analysis.
Oscillation function of the fan proves to be
an important function in the usage of
pedestal and table fan in providing comfort
level, and hence suitable testing methods
were developed to analyse the functionality.
Using the testing protocol that has been
developed, the experiment was conducted by
considering four different brands of fans and
quantitative and qualitative conclusions were
drawn from the data analysis for the
performance rating. The service factor
incorporates both the flow rate and the power
consumption of the fans and hence gives a better
picture of the output achieved by the fan. It does
not incorporate other factors such as comfort
level achieved by the fan. The incremental flow
rate provides a way to incorporate the different
comfort level achieved by the fan. The increment
between each regulator settings should be
included and hence simple averaging of the
incremental flow rate was considered for the
performance rating.
The power factor of all four fans tested were
more than 0.95 and hence the impact of it on the
performance rating is negligible. As the sample
size of the experiment is only limited to four
fans, the factor for power factor was considered
and a thorough analysis has to be done with a
bigger sample size. The oscillation factor
incorporates two important factors, the time in
which the minimum velocity for thermal
comfort is sensed and the oscillation angle. A
factor of 0.75 was given for the aspect of thermal
comfort and a factor of 0.25 was given for the
oscillation angle. The star ratings were
calculated for each plane for all four fans to
determine an optimum plane distance to
incorporate in the testing protocol.
According to the analysis variation in star
ratings for all fans are less in planes measured
up to 4D (D fan rotor diameter).
References
1. Wallis, R. A., Axial Flow Fans And Ducts,
New York: John Wiley & Sons, 1983.
2. Srilanka Standard 1600, Srilanka Stadard Institution,
2011.
3. Mahlia, T. M. I., Masjuki, H., Taha, F. M., Rahim,
N. A., and Saidur, R., “Energy labeling for electric
fans in Malaysia,” Energy Policy, vol. 33, no. 1, pp.
63-68, 2005.
4. Sugathapala, A. G. T., and Somarathne, P. B. I.,
“Performance Analysis of Pedestal Fans an
Experimental Investigation,” in ERU Symposium,
University of Moratuwa, Sri Lanka, 2000.
5. Jayasinghe, M.T.R, Priyanvada, A.K.M, and
Jayawardena, A. I,(2002),“Orientation of
Roof and Openings: Their Influences on
Indoor Thermal Comfort of Single Storey
Houses”.
... Trong nghiên cứu [4], D. Dwivedi và cộng sự đã tiến hành khảo sát mô hình quạt hướng trục với cánh quạt xiên về phía trước và phía sau, nhằm so sánh các thông số khí động như áp tĩnh, lưu lượng, hệ số dòng chuyển động giữa 2 mô hình để tìm ra được mô hình hoạt động hiệu quả nhất, đồng thời tiến hành so sánh với mô hình thực nghiệm để kiểm tra các sai số thực tế. Về mặt thực nghiệm, trong nghiên cứu [5] A. G. T. Sugathapala và các đồng sự đã sử dụng phương pháp khảo sát phổ vận tốc quạt tương tự với phương pháp sẽ được trình bày trong bài báo này. Các mẫu quạt được phân tích trong [5] có kích thước hình học và các thông số hoạt động tương tự với hai mẫu quạt mục tiêu của nhóm tác giả. ...
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At present, the selection of the roof type and roof orientation for houses is primarily based on cost and aesthetic considerations, without much regard to the thermal performance of the roof. However, since Sri Lanka is a tropical country, the roof causes significant adverse effects on the thermal comfort indoors and therefore. its thermal performance should be carefully considered on selection of the roof type and orientation. Otherwise, the resulting warm indoors will cause the occupants to use fans. This is not a healthy development due to the energy crisis the country is now facing. Another aspect that deserves attention is the orientation of openings. This paper investigates the effect of the orientation of the roof and the openings on the indoor thermal comfort of single storey houses. Two roof types commonly adopted in Sri Lanka are considered. namely cement fibre roof with cement fibre flat ceiling and cement fibre roof with sloping cement fibre ceiling. Using DEROB-LTH computer program. a four-room model house was simulated. For two roof orientations, i.e. the ridge along east-west and the ridge along north-south, the simulations were carried out for March, June and December, when different. extremes of sun path occur. The results indicate that the roof orientation is not so significant as the orientation of openings on the indoor thermal comfort in single storey houses.
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To reduce energy consumption in the residential sector, Malaysia Energy Commission is considering implementing energy labels for household electrical appliances including electric fans in 2005. The purpose of the energy labels is to provide the consumers a guideline to compare the size, features, price and efficiency of the appliance. This paper discusses the energy label for electric fans in this country based on Malaysian Standards developed by a technical committee that reviewed the performance of household electrical appliances. This study includes methodology for the calculation of the energy efficiency star rating and projected energy usage, performance requirements, details of the energy label and the requirements for the valid application in Malaysia. The label also can be adopted for other household electrical appliances with only slight modifications.
Performance Analysis of Pedestal Fans an Experimental Investigation
  • A G T Sugathapala
  • P B I Somarathne
Sugathapala, A. G. T., and Somarathne, P. B. I., "Performance Analysis of Pedestal Fans an Experimental Investigation," in ERU Symposium, University of Moratuwa, Sri Lanka, 2000.