In the present work two parabolic trough concentrator system of different rim angle and different reflector aperture area is designed, fabricated, and evaluated, and operated for generate hot water .There one system is 45° rim angle and next is of 90° rim angles, here reflector aperture area of 45° rim angle has operatically 20% more than 90° rim angle system, but remaining all other features are same for both the 90° and 45° system. On operation of the system we gets nearly same efficiency for both the system thus we observe that for all same equal features except of reflector aperture area, the efficiency got 20+% more for 90° rim angle compare to 45° rim angle.

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
65
COMPARATIVE STUDY OF PARABOLIC
TROUGH CONCENTRATORS
Santosh Chandra Anand, Dr. Ajeet Kumar Rai, Vivek Sachan
MED, SSET, Sam Higginbottom Institute of Agriculture Technology and Sciences,
Allahabad (U.P.), India
ABSTRACT
In the present work two parabolic trough concentrator system of different rim angle and
different reflector aperture area is designed, fabricated, and evaluated, and operated for generate hot
water .There one system is 45° rim angle and next is of 90° rim angles, here reflector aperture area of
45° rim angle has operatically 20% more than 90° rim angle system, but remaining all other features
are same for both the 90° and 45° system. On operation of the system we gets nearly same efficiency
for both the system thus we observe that for all same equal features except of reflector aperture area,
the efficiency got 20+% more for 90° rim angle compare to 45° rim angle. The Supporting stand of
concentrator is made of mild steel & reflector is made of acrylic sheet with a rim angle of 45 and 90
degree and aperture area of 2.20 m square and 1.84 m square with a concentration ratio of 10.00 and
08.30. Both the receiver tube has made of aluminum metal material. The thermal performance of the
PTC was determined based on ASHRAE 93-1986 (RA 91) .The maximum instantaneous thermal
efficiency separately both system is obtained closely to 58.32% – 59.24 % range. The total cost for
each separate system is calculated Rs 4500 Indian.
Keywords: Reflector Aperture Area, Rim Angle, Concentration Ratio.
INTRODUCTION
The Improper use of fossil fuels has led to negative imbalance in the natural environment so
need of using both non-renewable and renewable energy resources were taken to be the main aim
and the utilization objective outlined the need to use energy efficiently. Power plants and
domestically uses parabolic trough collectors to concentrate the direct solar radiation onto a tubular
receiver to generate hot water and water steam for Boiler and turbines for Industrial and domestic
and Buildings uses also. Parabolic trough power plants are participates in the biggest part of the total
installed concentrating solar power technology. Hence other technologies systems like Fresnel power
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2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
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plants, solar tower power plants and dish/ Sterling systems are also using but parabolic trough power
plants provide over 90% of the capacity of concentrating solar power plant technology that is in
operation or under construction up to September 2010. In the projected additional capacity more than
70% are constituted by parabolic trough power plants. PTC mainly consists of a cylindrical parabolic
reflector and a metal tube receiver at its focal plane. The receiver is black coated for heat loss
resistant and much absorb heat radiation purpose black paint coated at the outside surface covered by
concentrator and rotated about one axis to track the sun`s directional motion. The sun tracking
system has two types, one is single tracking and another is double tracking system. In PTC
concentrated heat is transferred through the absorber tube to working fluid for required purpose.
The aperture diameter, rim angle, reflector property and absorber size and shape is defines the PTC.
The absorber tube is made of aluminum for quick heat, low cost; reduce weight and protection from
salt decomposition and corrosion on outer surface of tube. Hence it is difficult to curve a very large,
mirror strips so used in the shape of parabolic cylinder. Reflectors are made of anodized, aluminum
Mylar or curved silvered glass. The concentration ratio for a cylindrical.
Absorber tube varies from 5 to 30+. The Concentration ratios for composite system can be
theoretically very high with the imaging concentrators of precise optical elements and continuous
automatic tracking system is in the range of 10 to 40 000. The reflector and absorber with collector
are fixed on the frame structure. The major energy losses from a concentrator-receiver assembly for
normal incidence rays deflected away from concentrating plane, losses during reflection from
reflecting surface and convection loss from the receiver to surrounding.
PTC can be oriented in these three directions, East-west, north-south or polar directions. The
East-west, north-south is simple to assemble and have higher incidence angle cosine losses. The
polar configuration intercepts more solar radiation per unit area as compared to other modes.
DESIGN CONSIDERATIONS
In the present PTC has following innovative characteristics; easy constructible, strong and
stable in structure, light in weight and low in cost. There we have used for reflecting mirror two
Acrylic Mirror Sheets of the size 0.92 meter wide, 1.22 meter long and 4 mm thick has placed
longitudinally in each system. The parabolic profile is determined by the shape of the ribs and the
width of the sheets. The weight of sheets is rest on said ribs. The total aperture area is for 45° is
2.208m² and for 90° included collectors shadow is 1.840 m², but the reflector’
s total area is equal for
both the systems.
PTC DESIGN PARAMETERS
The PTC dimensions and designing parameters has determined by these considerations.
For these two separate systems of 90° and 45° rim angle of parabola these two
considerations has determined. The first is aperture of the parabola of 1.22m wide acrylic sheet is
determined by ‘Wa’ and second is focal length ‘݂’ of parabola. And D₀ is the outer diameter of the
receiver tube.
Aperture of parabola ‘Wa’
Wa ൌ
ଶୗ ୲ୟ୬ቀ
കೝ
మ
ቁ
ሺୱୣୡቀ
കమ
మ
ቁା୲ୟ୬ቀ
കೝ
మ
ቁା୪୬ሺୱୣୡቀ
കమ
మ
ቁା୲ୟ୬ቀ
കೝ
మ
ቁሻሻ

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
67
Focal length of parabola ‘݂’
݂ ൌ
୛౗
ସ௧௔௡ቀ
കೝ
మ
ቁ
Geometrical concentration ratio ‘C’ for tubular receive
‫ܥ‬ ൌ
ௐೌ
గ ஽బ
We have taken D₀= 0.03 m
The three parameters rim angle, aperture width and focal length are determine the cross-
section of PTC. ψ is expressed as a function of the ratio of the aperture width to the focal length.
tan ψ=
ሺୟ/୤ሻ
ଶି
భ
ఴ
ሺቀ
ೌ
೑
ቁ‫כ‬ቀ
ೌ
೑
ቁሻ
The function of the rim angle is expressed as the ratio of the aperture width to the focal length
that is = a/fҮ
Here ݂ is the focal length, i.e. the distance between the vertex of the parabola and the focal
point. Equation of parabola on x axis:
ܻ ൌ
ଵ ௫మ
ସ௙
Table 1: Specifications of PTC
FABRICATION OF PTC
The PTC parts has constructed according to given below process and descriptions.
1-Frame structure for PTC system holding and support
For holding and support the receiver and reflector a frame structure of made by mild steel
Iron has assembled with use of arc welding, drilling and nut-bolt joint. The reflector support frame
portion was adjustable to horizontal axis for automatic or manual sun tracking. The single Sun
tracking and double Sun tracking structure is designs according structure frame manner.
1 Rim angle( φr ) 45° 90°
2 Focal length ( ݂) 0.51m 0.25m
3 Aperture width ( Wa) 1.20m 1.04m
4 Diameter of receiver tube (D₀) 0.0384m 0.0384m
5 Length of Parabola (L) 1.84m 1.84m
6 Effective Aperture Area (Aa) 1.56m 1.30m
7 Concentration Ratio (C) 9.952 8.625
8 Reflectivity of collector (ρ) 0.7 0.7
9 Absorptivity of receiver tube (α) 0.6 0.6
10 Transitivity of receiver tube (τ) 0.6 0.6
11 Intercept Factor (γ) 0.72 0.72

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
68
2- Parabolic Trough or Receiver-Absorber assembly
Commonly parabolic trough has four parameters are used to determine, in this system, trough
length (1.84m), focal length (25cm, 51cm), aperture width (104cm, 120cm) and rim angle
ψ (90°, 45°).
Rim angle is angle between optical axis and line between focal point and rim angle. Focal
length is distance between focal point and vertex. Aperture width is distance between one rim to
other rim in one parabola.
Rim angle has an effect on the concentration ratio and on the total irradiance per meter
absorber tube in W/m. If the rim angle is very big then the way of reflected radiation from outer part
of mirror is very long and the beam spread is very big, reducing, hence, the concentration ratio.
Hence a mirror with a smaller rim angle and the same aperture width would permit a higher
concentration ratio.
At 45° rim angle the highest concentration ratio is reaches and on increasing rim angle the
Sun image is widening and then concentration ratio is decreasing capture to 45° rim angle, and when
below the 45° rim angle now Sun image is more widening compare to first condition and then C.R. is
much more decreases.
In higher rim angle the absorber tube is nearer allocated the mirror then radiation beam is
spread and reduces C.R. The shadow of tubular also reduces mirror receiver area, aperture and C.R.
also. The absorber distance is larger in very large rim angle as well as very small rim angle.
The more weight carries the radiation aberration due to mirror slope error. Mirror is determined as at
a Sun position it captures the radiation beams.
EXPERIMENTAL SETUP
In this experimental setup of parabolic trough concentrator we have used a 30 liter storage
source tank for supply the working fluid to receiver tube. The storage source tank level is 0.25m
higher than the receiver tube’s maximum height and the connecting tube is flexible and 0.75m long
to rotate the receiver movement and direction for Sun tracking. Our system was oriented in north-
south to capture maximum isolation. The system was able for manual tracking.
Figure 1: Experimental Setup
In the system collector performance over the day is quit uneven and is reduces in the hours
after sunrise and before sunset. So to reduce this problem we have enlarged 0.50m length of receiver
tube at inlet and outlet side in the focal plane.

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
69
We have applied adjustable flow control valve arrangement at collector end to variance the
different, constant mass-flow rate with drop-wise flow. Our flow rate was 2 liter/3 liter/4 liter per
hour droplet-wise constant mass-flow rate condition 8 hours day observations.
We have fitted the thermocouple sensors to observe the temperature at point of receiver’s
in/mid/out points, source storage tank, collector storage, reflector sheet’s front/back sides and
ambient temperature pick out.
We have used solarimeter to measure the solar radiation intensity on mirror sheet and
receiver tube. For measuring wind velocity we used anemometer.
PERFORMANCE OF PARABOLIC TROUGH COLLECTOR
In this system estimated performance are the solar field efficiency and useful heat output
from solar effected area under different operating conditions for characterizing the performance.
Thermal Efficiency
In thermal efficiency, it is affected by thermal losses. Thermal losses depend on the
temperature difference between the heat transfer medium and the surrounding air. Heat loss from a
warmer surface to ambient air is because of convection and thermal radiations.
Qconv = h.A.∆T
Qrad = Ԑ.ρ.A.(T4
amb-T4
abs)
Qcond = (ߣߣߣߣ/b).A. ∆T
Here b is insulation thickness.
Collector overall efficiency ߟc is defined as the ratio between the useful output Qu by collector to
global irradiance I on Aa
ߟc=
ொೠ
஺ೌ
*Ib
For collector useful output Qu
Qu=mCp(T0-Tc)=AaIb ߟ₀-Aabs*Ul(Tabs-Ta)
Optical efficiency
Optical efficiency ߟ₀ is defined as total amount of radiation absorbed on absorber tube outer
surface to the amount of direct normal radiation incident on aperture area. If incident radiation is
normal to the aperture is (ߐ=0°) then the optical efficiency ߟ₀=ρ.(τ.α).γ
RESULT AND DISCUSSION
Number of observations has taken on both the system in the month of May 2014, in solar lab
ground of SHIATS Allahabad, Uttar Pradesh, India.
The observation data of both 90° rim angle and 45° rim angle PTC has taken and calculated
the thermal efficiency at separately particular day. The maximum thermal efficiency has got 58% for
45° rim angle and 59% for 90° rim angle systems.

6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
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Fig 2: Variation of solar intensity with respect to time of a day on a particular day in the month of
may (23/05/2014)
Figure 3: Variation of wind velocity with respect to time of a day in the month of May
at a particular day (23/05/2014)
Figure 4: Variation of temperature with respect to time of a day of receiver tube at in/mid/end point
at a particular day (23/05/2014)

7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
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Figure 5: Variation of temperature rise (inlet-outlet) difference with respect to time of a day of on a
particular day 23/05/2014
Figure 6: Variation of thermal efficiency with respect to time of a day, at mass flow rate of 2
liter/hour on a particular day in the month of May (21/05/2014)
Figure 7: Variation of thermal efficiency with respect to time of a day, at mass flow rate of 3
liter/hour on a particular day in the month of May (22/05/2014)

8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 65-73 © IAEME
72
Figure 8: Variation of thermal efficiency with respect to time of a day, at mass flow rate of 4
liter/hour on a particular day in the month of May (23/05/2014)
The result shows that the thermal efficiency of both PTC at different mass flow rate of drop
wise constant continue flow of working fluid (Water).
The result has shows that for same size mirror sheet at rim angle 45° and 90°, the thermal
efficiency has closely equals. Hence in 90° rim angle PTC has active Sun radiation receiving active
aperture area of reflector sheet receiver is 20% less due to aperture width and absorber tube is closely
to reflector sheet appears the shadow on mirror sheet. Thus 90° rim angle PTC system is 20% more
efficient than 45° rim angle PTC system for same equal area of receiver mirror sheet and absorber
tube system.
CONCLUSION
From the observations, calculated data and calculations in relation with analysis and
discussion, this research investigation can be calculated that fabricated PTC has maximum thermal
efficiency has got 58% for 45° rim angle system and 59% for 90° rim angle system. The result
concludes that 90° rim angle PTC has 20% more efficient compare to 45° rim angle PTC system.
And 90° degree rim angle system is permits easy protection with flat glass mirror reflector sheet.
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