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International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 11
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
Experimental and Theoretical Investigation to
Generate Steam by Parabolic Trough Solar
Collector with Using Different Heat Transfer Fluids Mohammed Hasan Abbood
1 and Mohammed Mohsen Mohammed
2
1 PhD, Assistant professor, Mechanical Engineering Dep., College of Engineering, University of Kerbala.
2 M.Sc. student, Mechanical Engineering Dep., College of Engineering, University of Kerbala.
Abstract-- This paper describes the mathematical model and
experimental tests for parabolic trough solar collector (PTSC).
The model is based on detailed energy balances, and it has been
applied to evaluate collector thermal performances with
different heat transfer fluids. The influence of fluids
temperature has been studied from the point of view of heat
gain and thermal efficiency. The working fluids which have
been selected for this study are hydraulic oil, ethylene glycol
based water, and water. An experimental investigation for
testing the performance of parabolic trough solar collector
(PTSC) is carried out to generate steam at moderate
temperature. The tests have been carried out in KERBALA
climatic conditions (32.34º N, 44.03º E) during selective days.
The results show that the best performance was in case of using
hydraulic oil as heat transfer fluid. The maximum
enhancement in thermal efficiency was 31.7% between
hydraulic oil and water. While the enhancement in the thermal
efficiency reaches about 20.4% between ethylene glycol and
water.
Index Term-- Solar collector, Concentrated solar collector,
Parabolic trough collector, Receiver tube, Thermal efficiency.
NOMENCLATURE
Aa Collector Aperture area K(Ɵ) Incident Angle Modifier
Ag Area of Glass Cover L Collector length
Ar Area of Receiver Nu Nusselt Number
Cp Specific Heat Pr Prandtl Number
Dgc Glass Cover Diameter Qu Useful Heat Gain by the collector
Dr Receiver Diameter Re Reynolds Number
FR Heat Removal Factor S Absorbed Solar Radiation Per Unit Area
hrad,gc-a Radiation Heat Transfer Coefficient between
Glass and Ambient Air Ta Ambient Temperature
hrad,rec-gc Radiation Heat Transfer Coefficient between
Receiver and Glass Cover Tg Temperature of the Glass Cover
hconv,rec-gc Convection Heat Transfer Coefficient between
Receiver and Glass Cover Tf,i Inlet Fluid Temperature to the Collector
hw Wind Heat Transfer Coefficient Tf,o Outlet Fluid Temperature from the
Collector
Ib Beam Radiation Tw Water temperature inside the heat
exchanger
K Thermal Conductivity UL Heat Loss Coefficient
1. INTRODUCTION
In recent years, competition and development among
countries to produce energy cleanly away from traditional
ways of producing energy with very large residues on the
environment. Many countries now rely more on renewable
energy and are working to transform them from one form to
another and develop them. One of the most important
renewable energy sources that can be depended on the solar
energy. Most the application of steam generation for
industrial use or electricity production by solar energy, used
the method of concentrator solar radiation. Nowadays,
parabolic trough solar technology is the most used solar
application. The following researches will show the
summary for previous theoretical and practical work
regarding parabolic trough system.
The first practical experience with Parabolic trough
solar collectors (PTSC) goes back to 1870, when a
successful engineer, Ericsson, a Swedish immigrant to the
United States, designed and built a 3.5m2 aperture collector
which drove a small 373 W engine. Steam was produced
directly inside the solar collector (today called Direct Steam
Generation or DSG) [1]. Following this more researches are
try to enhancement the efficiency of PTSC. A publication
then by Lüpfert et al. [2] studied experimentally thermal
properties of receivers of a parabolic trough. In this study
different methods to calculate the thermal loss from a
receiver tube was presented based on their operating
temperature. It was observed that the solar parabolic trough
plants which are having a temperature range of about 390°C
were having an energy loss of about 300 W/m of receiver
length. Qu et al. [3] developed a mathematical model of
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 12
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
parabolic trough collector used for solar cooling and heating
by using energy balance correlations between the absorber
tube, glass tube, and surroundings. The results of the
comparison between the mathematical model and the
experimental data indicate some differences, including high
measured glass temperature and low measured efficiencies.
These differences are attributed to heat loss at the supports
and the connectors and the low assumption of the
absorptivity. Ouagued et al. [4] built a numerical model of a
parabolic trough collector under Algerian climate. In this
model, the receiver is divided into several segments, and
heat transfer balance equations which rely on the collector
type, optical properties, heat transfer fluid (HTF), and
ambient conditions are applied for each segment. This work
led to the prediction of temperatures, heat loss, and heat gain
of the parabolic trough. Raj et al. [5] performed numerical
and experimental analysis on the performance of the
absorber tube of a parabolic trough collector system with
and without insertion. Water was used as the heat transfer
fluid and three different mass flow rates had been used
which were 33Kg/hr, 63 Kg/hr and 85 Kg/hr. It was seen
that presence of inserts gave a higher rise in the outlet
temperature when compared with the one without insertion
which was due to the fact the area of heat transfer was
increased with the insertion. It was also observed that the
thermal stresses on the tube with insertion were less than
that without insertion. A study then done at 2014 by Filho et
al. [6] to describes the methodology and the results of an
experimental and numerical investigation of the thermal
losses of a small scale parabolic trough collector, The
numerical simulation when compared to the experimental
results for the losses shows the degradation of the vacuum in
the annular region of the absorber tube also the collector
was tested with solar radiation and the efficiency obtained
varied from 0.3 to 0.55.
The present work aims to develop a mathematical
model and experimental tests for parabolic trough solar
collector to generate steam by using different types of heat
transfer fluid (HTF) and with flow rate of 3 liters per minute
(LPM).
2. PARABOLIC THROUGH SOLAR COLLECTOR
Parabolic trough solar collectors (PTSC) are
considered as one of the most mature, successful, and
proven solar technologies for electricity generation and
steam requirements. The PTSC are typically operated at
temperatures range 50-400 ºC. The PTSC system consists of
support structure, parabolic trough, and receiver tube. The
parabolic trough shaped mirror concentrate sun rays onto
receiver tube which is placed in the focal line of the
parabola trough as shown in figure (1). The solar parabolic
trough is made up of several reflectors. The receiver tube is
typically composed of glass cover and an absorber tube with
a vacuum between these two elements, to reduce heat losses
by convection. The receiver of PTSC usually paint with
selective coating in order to maximize solar radiation
absorption. The absorbed solar radiation is conveyed to the
heat transfer fluid (HTF) that flows inside the absorber tube.
The HTF is provided heat to the thermal system directly by
using the fluid or indirectly by transferring heat using a heat
exchanger.
3. Heat transfer fluid (HTF)
Parabolic trough solar collectors PTSC used heat
transfer fluid HTF that flows through the receiver tube,
which is collecting and transporting solar thermal energy to
storage tanks or heat exchanger. The HTF leaves the
parabolic solar collector is utilized to produce steam that
used either in industrial processes or to generate electricity.
Some criteria must be taken in considered when choosing a
HTF such as thermal capacity, the coefficient of expansion,
viscosity, boiling point and freezing point. The most
commonly HTFs used in the applications of PTSC are air,
water, glycol and hydrocarbons oil.
Fig.1. The PTSC system
4. MODEL ANALYSIS
A theoretical model of PTSC has been presented in
detail. The model is mainly consisting of three parts. The
first part is estimating the solar radiation that reaches the
collector. The second part is optical analysis. The purpose of
this section is to determine the optical efficiency of the
PTSC which is the ratio of the amount of energy arriving to
the absorber tube to that hits the reflector. The last part is
thermal analysis, and the aim of this part is to predict the
thermal efficiency of PTSC. The proposed model is
implemented is MATLAB software, and it is validated with
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 13
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
experimental data. So the equations of this model can be
describe here as:
Optical efficiency
The optical efficiency is defined as the ratio of energy
reaching the absorber tube to that received by the reflector
aperture [7] :
(1)
The actual amount of absorbed radiation on the receiver is
calculated by [8]:
( ) ( ) (2)
Thermal model of PTSC
The thermal model was based on a one-dimensional steady-
state thermal-resistance heat transfer model. This model can
predict the behavior of any parabolic collector design under
any ambient condition and with a variety of work
parameters [9]. The heat transfer model considers radiation
and convection heat transfer modes from the solar radiation
to heat transfer fluid (HTF) as shown in figure (2).
Fig. 2. Thermal resistance model
Heat loss coefficient (UL) can be estimate based on receiver area:
[
( )
]
(3)
For the space between the glass cover and receiver is evacuated, and convection losses are negligible, UL is calculating from the
following equation:
[
( )
]
(4)
The convection heat transfer coefficient between the glass cover and ambient due to wind (hw) [7]:
(5)
For the convection loss coefficient, the Nusselt number (Nu) and the Reynold’s Number (Re) can be used as follow [7]:
( ) (6)
( ) (7)
(8)
The radiation heat transfer coefficient between glass cover and sky temperature is:
( ) (
) (9)
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 14
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
Where sky temperature is calculating from the following equation [10]
(10)
The radiation heat transfer coefficient between glass cover and receiver is:
( ) (
)
(
)
(11)
Heat Transfer to Working Fluid
The heat transfer from the receiver tube to the fluid (HTF) must be characterized by turbulent or laminar flow conditions
accordingly, the evaluates the Reynolds number of the fluid [11].
(12)
Nusselt number of the fluid :
(13)
( ) ( ) (14)
The heat transfer coefficient to the fluid, is evaluated:
(15)
Overall Heat Transfer Coefficient and heat removal Factor
The overall heat transfer coefficient, Uo, needs to be estimated, this should include the tube walls because the heat flux in a
concentrating collector is high. Based on the outside tube diameter, this is given by [11]
[
(
)
]
(16)
The collector efficiency factor, F', is given as:
(
)
(17)
The collector heat-removal factor FR, it is one of important design parameter where it is a measure of the thermal
resistance encountered by the absorbed solar radiation that reaching the collector. Its value depends on flow rate of working
fluid inside the receiver, FR is found by this equation [12]:
[ (
)] (18)
Thermal Efficiency of parabolic trough collector
The thermal efficiency of a PTSC can be defined as the ratio of heat gained by the collector, Qu, to the total incident
radiation that is incident on the aperture of the collector
(19)
Where the useful heat gained, Qu, is a function of the outlet and inlet temperature of the heat transfer fluid in the receiver tube as
shown below:
( ) (20)
The useful heat collected by the receiver can also be expressed in terms of optical efficiency, heat loss coefficient, heat removal
factor, and inlet receiver fluid temperature:
[
( )] (21)
Thermal efficiency can be found using the following equation [11]:
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 15
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
( )
(22)
5. Numerical solution for a mathematical model
The mathematical model is applied to study the
performance of a parabolic trough solar collector (PTSC).
This model consists of three parts. The first one is a solar
radiation model, the amount of beam radiation incident upon
collector is calculating using relationships and equations
between the Earth and the sun. The second one is the optical
model. In this part, has the ability to estimate the optical
efficiency. The last one, is the thermal model, which
estimate the amount of energy collected by the working
fluid, heat loss and thermal efficiency. This model is
implemented by MATLAB software. There are two types of
inputs: input variables and input parameters. The input
variables are changeable through the daytime such as date,
time, ambient temperature and wind speed. These input
variables must be entered into the code in order to run the
simulation. The input parameters have fixed values and do
not change through day time such as geometrical properties,
latitude and longitude of the PTSC location, outer and inner
diameter of the glass envelope and the receiver, aperture
area of the trough, and optical properties.
Fig. 3. Flow chart of MATLAB
For the solar model, inputs are time, and day date. All
the equation and relationship of sun-earth are considered to
produce angle of incidence and beam radiation. For optical
model, which the inputs are emissivity, absorptivity,
transmisivity, and reflectivity of the tube and parabolic
trough. Also, Incident angle modifier and End loss factor are
solved, which used to estimate the optical efficiency of
PTSC. For thermal model in which consist of heat transfer
equations by convection and radiation.
To find all temperatures and solve these equations, an
iterative process was suggested by Duffie [13]. Procedure
that used to solve this equation is by initially guessing a
value (closer to ambient temperature) for the outer glass
temperature, then solve the heat transfer equation through
heat collection element and evaluate the inner glass
temperature. The outer glass temperature (initial guess)
needs to be checked by performing an energy balance on the
glass cover to evaluated new value of outer glass
temperature. By comparing the two values of outer glass
temperature. If the comparison is not equal, a new guessing
value will apply as shown in flow chat, figure (3). after all
temperatures required are evaluated, heat losses, heat gain
and thermal efficiency are calculated.
6. Experimental rig and test procedure
A PTSC is a concentrating collector, which the
reflector surface has a parabolic form as shown in figure (4).
Solar radiation falling on trough then concentrated on the
focal line, where a receiver tube was placed. The parabolic
collector consists of three troughs, which are arranged in
series so that the heat transfer fluid (HTF) will gain heat
gradually as it flows through the tubes one by one. By
circulating the HTF, thermal energy in the HTF will transfer
to water by using a coil tank heat exchanger.
The experimental rig is designed, constructed and
tested to investigate its ability for steam generation at
moderate temperature. The PTSC system consist of a
mechanical structure (support frame), absorber, reflecting
parts, evacuated glass tube, heat exchanger, centrifugal
pump, auto tracking system and some other accessories. The
PTSC specifications are given in table 1. The glass receiver
tube composed of two coaxial borosilicate glass tubes with
one open end and another sealed.
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 16
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
Fig. 4. The PTSC system
Table I
Specifications of the PTSC
ITEM Value/Type
Rim angle (θr) 77.72
Focal distance (f) 233.1 mm
Glass cover external diameter (Dg) 58 mm
Receiver external diameter (Dr) 47 mm
Collector aperture width (W) 1040 mm
Concentration ratio (C) 46.8
The effective aperture width (W) 750 mm
Collector length (L) 1800 mm
Parabolic curvature 1220 mm
Total Collector aperture area 3.73 m2
Reflective material Aluminum composite panels
Tracking system One axis auto tracking system
Electrical motor Electrical motor with moving arm
The experimental setup used for testing the PTSC
system shown schematically in Fig. 5. It consists of the
following (1) support structure, (2) three parabolic troughs
(3) evacuated glass tube (4) coil-tank heat exchanger, and
(5) auto tracking system.
First, it is very important to clean the reflector from
any dirt or dust. Then, pump and tracking motor wires are
connected to electricity to running the test. Heat exchanger
tank is filled with 30 liters of water (half volume is filled
with water only). In the current experiment work, the
working fluid is circulated in a closed cycle. The collecting
tank is filled with working fluid from the main supply. After
this tank had been filled, the outlet from the tank connecting
to the pump, then the working fluid is pumped to the inlet of
troughs and the trough outlet to the coil inlet then exit from
the coil is connecting again to collecting tank. After that, the
tracking system of the troughs is turned on and moves the
troughs until the sun is directly over the troughs. The flow
meter keeps the flow rate of working fluid at 3 LPM, which
is placed before the troughs inlet and after the pump. The
fluid temperatures in their locations (as mentioned in
schematic diagram), ambient temperature, wind speed, the
pressure of steam and solar radiation are continuously
recorded during the test. After starting the test, working
fluid collects heat and its temperature rises, it goes to heat
exchanger coil to transferring heat energy to water. This
cycle repeats continuously throughout the test period until
steam production is achieved. In the current work, three type
of working fluid hydraulic oil and ethylene glycol based
water and water have been used.
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 17
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
Fig. 5. Schematic Diagram of Experimental Setup.
7. Results and discussion
This study presents the experimental and theoretical
investigation to generate steam by using a parabolic trough
solar collector PTSC system. Thermal performance for
PTSC is determined theoretically in MATLAB (R2014a)
software by evaluating the parameters that effected on the
system such as solar radiation, wind speed, day number, and
temperatures of HTF. Also, the thermal performance of
PTSC was calculated from measured data experimentally.
The measured data was recorded with different heat transfer
fluid hydraulic oil, ethylene glycol, and water. The tests
were conducted at the college of engineering/ University of
Kerbala (44.03° Longitude and 32.34° Latitude), through the
clear sky days for the months of July and August from 9:00
A.M until 2:30 P.M,
8. Outlet temperature
In this cases, the data measured experimentally are
recorded for three days under clear sky similar weather
(25th of July, 5th
and 9th
of August, 2018). all the necessary
data have been measured to study the performance of the
PTSC with hydraulic oil, ethylene glycol, and water as HTF.
Figure (7) shows the outlet temperature of working fluid
from the collector for different HTFs, which is increase
through the test day with time passing for all type of the
HTF until it reaches to the end of the experiments. This can
be referring to the actuality that the incident solar radiation
which falls on the collector directly due to auto tracking
system of the collector continuously and directly toward the
solar radiation. The maximum difference between hydraulic
oil and water was 21%, while the difference between
ethylene glycol and water was 7%. Figure (8) shows the
temperature difference between the outlet temperature and
inlet temperature through the solar collector for each
working fluid. This is referring to hydraulic oil is better than
ethylene glycol and water, which is heated up faster and its
temperature rises more. this is due to the low heat capacity
of hydraulic oil as compared with the two other fluids.
8.1 Heat gain through the collector
The useful heat gained was calculated from the inlet
and outlet temperatures through the collector, specific heat,
and flow rate of HTF. Figures (9) and (10) show the
experimental and theoretical heat gained from the collector
with time at 3 LPM flow rate respectively. It was noticed
from experimental results at figure (9), the maximum heat
gained enhancement between the hydraulic oil and water
was 29%, while the maximum enhancement between the
ethylene glycol and water was 16.5%. The useful heat gain
for the hydraulic oil is better than the other two HTF, and
the heat gain for ethylene glycol is better than the water and
lower than the hydraulic oil. This is because of the
difference in the thermal properties of each type of fluid
used and their ability to raise its temperature. The
comparison between the experimental and theoretical results
show that the maximum difference is 10.4%, 16%, and
14.9% for hydraulic oil, ethylene glycol based water, and
water respectively. This is due to several factors such as the
assumptions that assumed during the implementing of the
model, applying different equations, correlations, and Earth-
sun relationship in the model, the effect of dust and clouds
on the solar radiation that measured experimentally is
significant when compared with theoretical solar radiation,
and also thermal and optical losses that calculated in this
model can be lower than that the actual losses that have been
significantly influenced by the results of experimental heat
gain.
8.2 Heat gained by the heat exchanger tank
The heat gained by the water in the heat exchanger
tank is computed every 15 minutes through the tests with
different HTF (hydraulic oil, ethylene glycol, and water).
Figures (11), (12), and (13) show the comparison between
the three types of HTF. It is found that the temperature of
water in the tank of heat exchanger increase with time
passes. As a result of the solar radiation increase with time
passes. It is increased from 48.2oC to 95.4
oC, 47.9
oC to
92.1oC, and 47.8
oC to 90.6
oC for hydraulic oil, ethylene
glycol, and water, respectively.
On the other hand, the heat gained by the water starts
to increase until reach the maximum value 0.797 KW, 0.711
KW, and 0.58 KW, for hydraulic oil, ethylene glycol, and
water around noontime, respectively. Then, start to decrease
slowly due to decreasing in the solar radiation. This is due to
the proportional relation between the heat gain through the
collector and the heat gained by the water in the tank of the
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 18
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
heat exchanger, and their relation with a variation of solar
radiation during the test period.
8.3 Thermal efficiency
The collector thermal instantaneous efficiency is
determined from useful heat gain, solar radiation, and
aperture area, to analyze the performance of the PTSC
system. Figure (14) shows the comparison between the
experimental thermal efficiency for different HTF hydraulic
oil, ethylene glycol based water, and water. The maximum
difference in thermal efficiency was 31.7% between
hydraulic oil and water. While the difference between
thermal efficiency reaches about 20.4% between ethylene
glycol and water. It is clear that hydraulic oil gives better
thermal efficiency than other HTF, and thermal efficiency of
ethylene glycol is higher than water but lower than hydraulic
oil with the same flow rate. This is due to the different heat
capacity of HTF. Figure (14) and (15) show the
experimental and theoretical thermal efficiency. The
comparison between the experimental and theoretical results
show that the maximum difference is 9.7%, 15.1%, and
21.1% for hydraulic oil, ethylene glycol based water, and
water respectively. This is due to several factors such as
dust, clouds, wind speed, the transmissivity of the glass
cover, and absorptivity.
Fig. 7. outlet temperatures for different HTF with time at 3 LPM flow rate
Fig. 8. temperatures difference between inlet and outlet for different HTF
with time at 3 LPM flow rate
45
55
65
75
85
95
105
115
125
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM
Tem
per
ature
(oC
)
Time (hr.)
Hydraulic Oil Ethylene Glycol Water
0
2
4
6
8
10
12
14
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM
Tem
per
ature
dif
fere
nce
(oC
)
Time (hr.)
Hydraulic Oil Ethylene Glycol Water
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 19
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
Fig. 9. experimental heat gain for different HTF with time at flow rate 3 LPM
Fig. 10. theoretical heat gain for different HTF with time at flow rate 3 LPM
0
0.2
0.4
0.6
0.8
1
1.2
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM
Usf
ul
hea
t gai
n (
Kw
)
Time (hr.)
water
ethylene glycol
hydraulic oil
0
0.2
0.4
0.6
0.8
1
1.2
1.4
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM
Usf
ul
hea
t gai
n (
Kw
)
Time (hr.)
water
ethylene glycol
hydraulic oil
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 20
I J E N S IJENS © December 2018 IJENS -IJMME-4747-061821
Fig. 11. experimental heat gained by water and steam temperature with
time for hydraulic oil as working fluid
Fig. 12. experimental heat gained by water and steam temperature with
time for ethylene glycol as working fluid
40
50
60
70
80
90
100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM
Ste
am t
emper
ature
(oC
)
Usf
ul
hea
t gai
n (
Kw
)
Time (hr.)
Useful Heat Gained by
water
40
50
60
70
80
90
100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
9:00 AM 10:00
AM
11:00
AM
12:00 PM 1:00 PM 2:00 PM
Ste
am t
emper
ature
(oC
)
Usf
ul
hea
t gai
n (
Kw
)
Time (hr.)
Useful Heat Gain by
water
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 21
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Fig. 13. experimental heat gained by water and steam temperature with
time for water as working fluid
Fig. 14. experimental thermal efficiency at different HTF with time
40
50
60
70
80
90
100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
9:00 AM 10:00
AM
11:00
AM
12:00 PM 1:00 PM 2:00 PM
Ste
am t
emper
ature
(oC
)
Usf
ul
hea
t gai
n (
Kw
)
Time (hr.)
Useful Heat Gain by water
Steam Temperature
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM
Eff
icie
ncy
Time (hr.)
water
ethylene glycol
hydraulic oil
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:06 22
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Fig. 15. theoretical thermal efficiency at different HTF with time
9. Conclusions
A mathematical model has been implemented for
studied the thermal performance of the PTSC so as to
generate steam. This model takes into consideration the heat
transfer equations and correlations and heat transfer
mechanism that including radiation and convection. An
experimental investigation has been carried out for
analyzing the thermal performance of PTSC experimentally
so as to generate steam at medium temperature. In this
study, the experimental tests carried out with different heat
transfer fluids HTFs. The performance of the PTSC system
depends on the measured parameters such as ambient
temperature, inlet temperature, outlet temperature, and solar
intensity. A peak experimental efficiencies close to (33.2%,
28.5%, and 22.7%) were obtained for parabolic trough
collectors with hydraulic oil, ethylene glycol based water,
and water respectively.
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T., “Experimental analysis of overall thermal properties of parabolic trough receivers”, Journal of solar energy engineering,
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in a high temperature solar cooling and heating system”, Journal
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