Vol.:(0123456789) 1 3
Journal of Thermal Analysis and Calorimetry
https://doi.org/10.1007/s10973-020-09590-2
Comparative performance assessment of diferent absorber tube
geometries for parabolic trough solar collector using nanofuid
Muhammad Sajid Khan
1,2
· Mi Yan
1
· Hafz Muhammad Ali
3
· Khuram Pervez Amber
2
· Muhammad Anser Bashir
2
·
Bilal Akbar
2
· Samina Javed
4
Received: 8 October 2019 / Accepted: 17 March 2020
© Akadémiai Kiadó, Budapest, Hungary 2020
Abstract
Parabolic trough collector is the most mature and widely deployed concentrated solar power technology with temperature
ranging from 325 to 700 K. In this study, three diferent absorber tube geometries (smooth absorber tube, absorber tube with
twisted tape insert and tube with longitudinal fns) of commercially available LS-2 collector are modeled and investigated
using engineering equation solver. The objective of this study is to present a numerical comparative analysis of the available
thermal enhancement techniques. Comprehensive energetic and exergetic performance of diferent tube geometry confgura-
tions using Al
2
O
3
/water as a heat transfer fuid has been compared to assess the nature of exergy destruction due to the fuid’s
pressure, due to the heat transfer between sun and the receiver wall and due to the temperature diference between receiver
wall and heat transfer fuid temperature. Furthermore, pure base fuid (water) along with the nanofuid is used to evaluate
the system’s performance (thermal efciency, exergetic efciency, heat transfer coefcient, receiver temperature, pressure
drop, pumping work demand and friction factor). Smooth absorber tube with pure base fuid is the reference case, while fve
cases (smooth tube with nanofuid, tube with pure water and fns inserted, tube with nanofuid and fns inserted, tube with
pure water and twisted tape inserted, tube with nanofuid and twisted tape inserted) are investigated. Thermal efciency of
absorber tube with twisted tape insert and nanofuid is almost 72.26%, followed by tube with internal fns (72.10%), while
smooth absorber tube has nearly 71.09%. Heat transfer coefcient of twisted tape inserted tube with nanofuid and longitudinal
fns tube with nanofuid is greater than smooth absorber tube to almost 118.23% and 103.26%, respectively. The emphasis is
also given to the pressure drop of the examined cases as it depends up on the friction factor of the absorber tubes. The use of
nanofuid and twisted tape inserts leads to higher thermal enhancement, followed by the nanofuid and internal fns inserted
tube. The nanoparticle concentration is also varied to investigate its efect on diferent performance parameters of the system.
Keywords Parabolic trough · Absorber · Twisted tape · Longitudinal fns · Nanofuid · Base fuid · Thermal enhancement
techniques · Turbulators
List of symbols
A
ap
Aperture area (m
2
)
A
r
Receiver area (m
2
)
C
p
Specifc heat capacity (J kg
−1
K
−1
)
D
c,o
Outer cover diameter (m)
D
r,o
Outer receiver diameter (m)
E
X,Col
Collector exergy rate (W)
G
b
Solar radiation (W m
−2
)
f Friction factor
h Heat transfer coefcient (W m
−2
K
−1
)
k
nf
Thermal conductivity of nanofuid (W m
−2
K
−1
)
T
c
Cover temperature (K)
T
a
Ambient temperature (K)
U
L
Coefcient of heat loss (W m
−2
K
−1
)
U
0
Overall heat transfer coefcient
Q
loss
Heat loss (W)
* Hafz Muhammad Ali
hafz.ali@kfupm.edu.sa
1
Institute of Energy and Power Engineering, Zhejiang
University of Technology, Hangzhou 310014, Zhejiang,
China
2
Department of Mechanical Engineering, Mirpur University
of Science and Technology (MUST), Mirpur, AJK 10250,
Pakistan
3
Mechanical Engineering Department, King Fahd University
of Petroleum & Minerals (KFUPM), Dhahran 31261,
Saudi Arabia
4
Department of Mechanical Engineering, Air University,
Islamabad, Pakistan