Advances in Environmental Biology Collector Efficiency of the Polymer Solar Collector

Advances in Environmental Biology, 8(8) 2014, Pages: 2583-2588
AENSI Journals
Advances in Environmental Biology
Journal home page: http://www.aensiweb.com/AEB/
Collector Efficiency of the Polymer Solar Collector
1,2Mohd
1Mohd
1
2
Afzanizam Mohd Rosli, 1Sohif Mat, 1Mohd Khairul Anuar Sharif, 1Kamaruzzaman Sopian,
Yusof Sulaiman, 1E. Salleh
Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor. Malaysia.
Faculty of Mechanical Engineering, Universiti Teknikal Malaysia Melaka, 76100 Durian Tunggal, Melaka. Malaysia.
ARTICLE INFO
Article history:
Received 28 February 2014
Received in revised form 25 May 2014
Accepted 6 June 2014
Available online 20 June 2014
Keywords:
Collector efficiency
Polymer Solar collector
Heat energy balance
Low thermal conductivity
ABSTRACT
This paper examines the collector efficiency (F’) of the polymer collector in variation
of plate thickness, top heat loss coefficient and ratio of the thermal conductivity to plate
thickness (H). The collector efficiency reduced with the increase of the thickness for all
cases of top heat loss coefficient (Ut) as expected. Furthermore, the higher H value
increased the F’ for all conditions of Ut. The suitable thickness of the collector has been
determined in the range of 1.5 to 2.5 mm base on the F’. The top losses heat transfer
coefficient should be minimize to obtain higher performance. The polymer collector
needs to be optimum design to compensate the low thermal conductivity of the
material.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: M.A.M. Rosli, S. Mat, M.K.A. Sharif, K. Sopian, M.Y. Sulaiman, E. Salleh, Collector Efficiency of Polymer Solar
Collector. Adv. Environ. Biol., 8(8), 2583-2588, 2014
INTRODUCTION
The solar collector is the device harvesting solar energy into useful energy. Using the working fluid such as
water or air as heat exchanger, the useful heat can be used as space heating or water heating base on the required
applications. One of the important of the solar collector device is the absorber plate. As a major component of
the solar collector, it absorbs the heat from the surrounding to convert and transfer to the working fluid. The
conventional solar collector consists of glazing surface, absorber, insulator and mounting frame. Typically, the
absorber made from steel, aluminum and copper made the device is very costly [7]. In additional, it has other
problems such as handling issue, weight, resistant of chemical.
The polymer collector is the one option to solve the problems [1]. Made from low cost material and lighter
than steel material, it offers a huge potential of application as solar collector for water heating. Even the thermal
conductivity of the material relatively low compare to the copper, aluminum or steel, the optimization of the
polymer collector design able to compensate the major issue [1,2]. It depends on the several parameter design
of the polymer collector.
There are few type of the polymer collector design. Working as a same principle, the shape of the tube can
increase the surface area thus enhance the heat transfer. Figure xx show the design of polymer collector. In this
paper, the given polymer collector has been study in term of the collector efficiency. It refer to the variation of
the thickness, heat loss coefficient and the ratio of the thermal conductivity to thickness of the plate.
Fig. 1: (a) Cross section of polymer collector, (1) Glazing, (2) absorber, (3) frame (Tsilingiris 1999).
Corresponding Author: Mohd Afzanizam Mohd Rosli, Solar Energy Research Institute, Universiti Kebangsaan Malaysia,
43600 Bangi, Selangor. Malaysia.
E-mail: [email protected]
2584
Mohd Afzanizam Mohd Rosli et al, 2014
Advances in Environmental Biology, 8(8) 2014, Pages: 2583-2588
Fig. 2: (b) parallel polymer plate, (c) rib connected parallel plate, (d) seamed plastic soil absorber, (e) butyl
rubber absorber, (f) polymer tube absorber [6].
One of the criteria to evaluate the solar collector is the collector efficiency. In general, collector efficiency
is the ratio of the of the actual useful energy gain to the useful energy gain that would results if the collector
absorbing surface at the local fluid temperature. Denoted as F’, it is strong function of design parameter but not
for of temperature [8].
Methodology:
The available polymer collector has been study to predict the collector efficiency (F’). The heat energy
balance for the collector has been refer to available technical paper [6] which considered the thickness, solar
fraction and heat loss coefficient. Table 1 showed the parameter of given polymer collector by manufacturer.
Fig. 3 and Fig.4 show the polymer collector and heat loss coefficient of the collector.
Table 1: Parameter of the polymer collector.
Parameter
Length, L
Width, W
Thickness, b
Thermal conductivity, kp
Design – tube absorber
Fig. 3: Sample of the polymer solar collector.
Dimension
1.22 m
4.22 m
2 mm
0.2 W/m.K
5 mm diameter
2585
Mohd Afzanizam Mohd Rosli et al, 2014
Advances in Environmental Biology, 8(8) 2014, Pages: 2583-2588
Fig. 4: Heat loss coefficient on the collector.
In this study, several assumptions have been made to simplify the analysis [4].
Steady state conditions
No losses at the edge of collector.
Thermo physical of water are constant.
All convection heat transfer coefficient are constant.
Referring the diagram from Fig.4, the equation of heat energy balance can be written as follow (Tsilingiris
2002).
At the top surface of polymer absorber.
a)
b)
c)
d)
S  U t T p  Ta  
kp
b
T
p
 Tf   0
(1)
For water flow channel
kp
b
T
f
 Tb   qu 
kp
b
T
f
 Tb   0
(2)
which,
kp is the thermal conductivity of the polymer plate, b is the thickness of the polymer plate and qu is the
useful heat gain per unit area.
kp
b
T
f
 Tb   ub Tb  Ta   0
(3)
The Ut and Ub are the loss coefficient for top and bottom respectively. Eliminating Tb in Eqs. (2) and (3), it
derives as,
Tp  2T f 
k p bU b
1  k p bU b
Tf 
1
1  k p bU b
 Ta
(4)
Substitute Eq. (4) in Eq. (1), the equation can be written as follows,


qu  F ' S  U L T f  Ta 
(5)
the collector efficiency (F’) can be written as,
F'
H Ub
 1 1  U t H 
H Ub  Ut Ub
(6)
2586
Mohd Afzanizam Mohd Rosli et al, 2014
Advances in Environmental Biology, 8(8) 2014, Pages: 2583-2588
and overall loss coefficient can be derives as,




1
1
  U b 1 

U L  U t 1 


1

H
/
U
1

H
U
b 
b 


(7)
where,
H
kp
(8)
b
Results:
Based on the Eq (6), the variation of the top heat loss coefficient (Ut) and plate thickness (b) have been
study. For Ut conditions, it has been set in the range of 5, 10, 15 and 20 W/m2.K.
Collector efficiency for various thickness of polymer solar collector
1
Collector efficiency
0.95
0.9
0.85
0.8
Ut =5 W/m2.K
Ut =10 W/m2.K
0.75
Ut =15 W/m2.K
0.7
Ut =20 W/m2.K
1
1.5
2
2.5
thickness (m)
3
3.5
4
-3
x 10
Fig. 3: Collector efficiency (F’) for various plate thickness.
The collector efficiency (F’) in term of ratio of the thermal conductivity to plate thickness has been
investigated. The ranges of H in between 0 to 1000 W/m2.K. The equation of H has been addressed in Eq (8).
Collector efficiency of polymer solar collector for variation H value
1
0.9
0.8
Collector efficiency
0.7
0.6
0.5
0.4
0.3
Ut =5 W/m2.K
0.2
Ut =10 W/m2.K
Ut =15 W/m2.K
0.1
0
Ut =20 W/m2.K
0
100
200
300
400
500
600
H = kp/b
700
Fig. 4: Collector efficiency of polymer solar collector base on H value.
800
900
1000
2587
Mohd Afzanizam Mohd Rosli et al, 2014
Advances in Environmental Biology, 8(8) 2014, Pages: 2583-2588
Discussion:
Fig. 3 show the higher thickness reduced the collector efficiency of the collector as expected. When the
thickness of the plate increased, higher resistance has been built to allow the heat to penetrate the collector.
Therefore, it is not favor for the working fluid to produce the high useful heat. Taking a nominal thickness of
polymer collector in between 1.0 mm to 2.5 mm, the range of the collector efficiency is up to 0.8 to 0.9 for all
cases. One important criteria of designing the polymer collector is to withstand with load. Some numbers of the
top loss coefficient conditions have been study to investigate the effect of the collector efficiency (F’). It show
the F’ is linearly decrease with the increased of top loss coefficient conditions. The factor contributions of
higher top loss coefficient are losses by radiation, convection of wind and glazing. Knowing the thermal
conductivity of the polymer material relatively low, determination the optimum plate thickness is crucial to
obtain a good performance of the collector. Fig. 4, clearly showed the higher ratio thermal conductivity to
thickness, enhanced the F’ value. Consider the thermal conductivity of polymer collector is 0.2 W/m.K and the
thickness of polymer collector is 2 mm, the value of H is 100 W/m2.K which obtained collector efficiency
approximately 0.9 for all cases.
Conclusion:
The optimum design of the collector is important to obtain the good collector efficiency. It can be conclude
the suitable thickness of polymer collector in the range 1.5 to 2.5 mm after consider the load of the water along
the collector. Even the thermal conductivity of the polymer material is relatively low compared to the steel, the
proper design and consideration able to compensate some factors such handling issue, cost of product, resistance
of chemical and wear for a long period of operation. The higher thickness of plate will decrease the collector
efficiency for all cases of heat loss coefficient. Also, reduce of H value decrease the collector efficiency of the
collector. The environment factor is the one of the crucial factor determining the performance of the collector
such as convection due to air and radiation from polymer plate to sky. Optimizing those criteria made the
polymer collector able to replace the conventional solar collector to produce domestic hot water for residential.
ACKNOWLEDGMENTS
Authors like to thank Universiti Teknikal Malaysia Melaka, Universiti Kebangsaan Malaysia, Ministry of
Education, Malaysia for financial support. Also for Greentech Sdn Bhd for the donation of polymer collector.
Nomenclature
Ac
collector area (m2)
b
plate thickness (m)
Cp
specific heat (J/kg.°C)
F
collector efficiency factor
FR
heat removal efficiency factor
H
defines as kp/b (W/m2.°C)
k
thermal conductivity (J/m.°C)
L
Length (m)
ṁ
mass flow rate (kg/s)
q
heat rate (W/m2)
S
energy absorb (W/m2)
T
temperature (°C)
U
heat loss coefficient (W/m2.°C)
Subscript
a
ambient
b
base
f
fluid
i
inlet
L
overall loss
p
plate
u
useful
REFERENCES
[1] Cristofari, C, J.L. Canaletti, G. Notton and C. Darras. 2012. Energy Procedia Innovative patented PV / TH
Solar Collector : optimization and performance evaluation. Energy Procedia, 14: 235-240.
[2] Cristofari, C., G. Notton, P. Poggi and A. Louche, 2002. MODELLING AND PERFORMANCE OF A
COPOLYMER SOLAR WATER HEATING COLLECTOR, 72(2): 99-112.
[3] Cristofari, Christian, Gilles Notton and Jean Louis Canaletti, 2009. Thermal behavior of a copolymer
PV/Th solar system in low flow rate conditions. Solar Energy, 83(8): 1123-1138.
[4] Dubey, Swapnil, and G.N. Tiwari, 2008. Thermal modeling of a combined system of photovoltaic thermal
(PV/T) solar water heater. Solar Energy, 82(7): 602-612.
[5] Tsilingiris, P.T., 1999. Towards making solar water heating technology feasible the polymer solar collector
approach. Energy Conversion and Management, 40: 1237-1250.
[6] Tsilingiris, P.T., 2002. Back absorbing parallel plate polymer absorbers in solar collector design. Energy
Conversion and Management, 43(1): 135-150.
[7] Tyagi, V.V., S.C. Kaushik, and S.K. Tyagi. 2012. Advancement in solar photovoltaic/thermal (PV/T)
hybrid collector technology. Renewable and Sustainable Energy Reviews, 16(3): 1383-1398.
2588
Mohd Afzanizam Mohd Rosli et al, 2014
Advances in Environmental Biology, 8(8) 2014, Pages: 2583-2588
[8]
William, A. Beckman, John A. Duffie, 1980. Solar Engineering of Thermal Processes. In Solar Engineering
of Thermal Processes, New York: John Wiley & Sons, Inc, pp: 197.