The poster presentation is a part of my academic thesis. It is the pre-defense of my group about our thesis topic, "Performance Enhancement of Phase-Changing Material by Embedding Lower Fin".

1. Department of Mechanical Engineering
Shahjalal University of Science and Technology
ABSTRACT
Thermal Performance Enhancement of Phase-Changing Material by Embedding Lower Fin
INTRODUCTION
LITERATURE REVIEW
PHYSICAL MODELING
MATHEMATICAL MODELING
NUMERICAL METHOD AND VALIDATION
RESULT
CONCLUSION
FUTURE SCOPE
REFERENCES
A large amount of heat energy is rejected by ICE without being used. Now it is the new requirement to
utilize the waste heat in a useful work. The recovery and utilization of the waste heat not only reduces the
demand for fossil fuels but also will be helpful in reducing greenhouse gas emissions to the environment.
One of the most promising WHR (Waste Heat Recovery) systems is using thermal energy storage (TES)
by integrating into the ICEs. The TES uses PCM that has thermal storage capability which plays a key
role in improving energy efficiency by limiting the incongruity between the energy supply and the energy
demand. PCM contributes more to storing the energy in the thermal energy storage. PCMs provide
different properties that meet the suitable TES mediums. Pure paraffin wax is selected as a phase-
changing material as it has a high specific heat capacity and is one of the excellent materials for heat
storage. So, improving the thermal performance of the PCM will help to effectively use the waste heat
emitted by ICEs.
As a great amount of energy consumed by an internal combustion engine (ICE) is wasted through the
exhaust gas, heat recovery from the exhaust is a promising technology to improve the efficiency of an
engine. Different technologies have been introduced to recover the waste heat. Due to the low thermal
controllability, low thermal storability, and difficulties in implementation, these technologies are not
considered as efficient. By overcoming those drawbacks thermal energy storage (TES) system captures
the researcher's interest. The TES with phase change materials (PCMs) is the most utilized in ICEs
because of its good controllability and high storage capacity. The PCMs are a class of materials that
exhibit good phase transformations by undergoing cyclic freezing and melting processes through the
influence of heat transfer. So, its performance greatly depends on the heat transfer process. Inserted fin in
PCMs is one of the most efficient methods to boost the heat transfer between the PCM and heat transfer
fluid (HTF). A two-dimensional computational fluid dynamic simulation is carried out with a fin
embedded in a double tube shell-and-tube latent heat thermal energy storage (LHTES) system. In that
model, the HTF flows through the inner tube, and the PCM is placed at the region between the inner tube
and the outer tube. The PCM is pure paraffin wax, and the fins material is aluminum which is installed at
the lower half of the inner tube. The number of fins is 7. A combined quantitative and qualitative analysis
is done in the present work.
Pandiyarajan et al. [1] developed a combined energy storage system for sensible heat and for latent heat.
To extract heat from the diesel engine exhaust system, a finned shell and tube heat exchanger and a
thermal energy storage (TES) tank filled with paraffin wax as a phase-changing material are designed.
Saleel [2] studied and analyzed the melting time, temperature distribution, and heat transfer
characteristics of two PCMs one was pure paraffin wax and another one was paraffin with 1 mass %
fraction of SiC nanoparticles. From the comparative analysis, it was found that the addition of SiC
nanoparticles in base paraffin develops the latent heat energy-storing capacity of the PCM by 50% and
reduces the melting time. Park et al. [3] numerically studied the effect of the number and arrangement of
tubes on the melting performance of PCM in a multi-tube shell-and-tube latent heat thermal energy
storage system. From their numerical analysis, the arrangement of tubes installed downward in the
vertical direction has the best melting performance. Deng et al. [4] tried to find out the most effective
fins arrangement to boost the charging rate of Phase Changing Material (PCM). From the proposed
arrangement of fins, the arrangement of lower fins increases the heat transfer in the lower part, resulting
in uniform melting. Tao and He [5] investigated the effects of liquid PCM natural convection on Latent
Heat Storage (LHS) performance. Salts were chosen as a PCM. They investigated the solid-liquid
interface and PCM temperature distribution. Based on their investigation a local finned tube was designed
to enhance the uniformity of the LHS process and further enhance the LHS performance. From their
analysis, they recommended the number of fins was 7 for better thermal performance.
[1] V. Pandiyarajan, M. Chinna Pandian, E. Malan, R. Velraj, R. V. Seeniraj, Experimental investigation on heat
recovery from diesel engine exhaust using finned shell and tube heat exchanger and thermal storage system, Appl
Energy. 88 (2011) 77–87. https://doi.org/10.1016/j.apenergy.2010.07.023.
[2] C.A. Saleel, Numerical study on melting and heat transfer characteristics of paraffin wax/ SiC paraffin using
enthalpy-porosity model, J Therm Anal Calorim. 147 (2022) 10497–10508. https://doi.org/10.1007/s10973-022-11265-
z.
[3] S.H. Park, Y.G. Park, M.Y. Ha, A numerical study on the effect of the number and arrangement of tubes on the
melting performance of phase change material in a multi-tube latent thermal energy storage system, J Energy Storage.
32 (2020). https://doi.org/10.1016/j.est.2020.101780.
[4] S. Deng, C. Nie, H. Jiang, W.B. Ye, Evaluation and optimization of thermal performance for a finned double tube
latent heat thermal energy storage, Int J Heat Mass Transf. 130 (2019) 532–544.
https://doi.org/10.1016/j.ijheatmasstransfer.2018.10.126.
[5] Y.B. Tao, Y.L. He, Effects of natural convection on latent heat storage performance of salt in a horizontal concentric
tube, Appl Energy. 143 (2015) 38–46. https://doi.org/10.1016/j.apenergy.2015.01.008.
( )
( ) ( ) ( )
( ) ( ) ( )
2
Continuity Equation: 0
Momentum Equation:
Energy Equation:
ref
d
v
dt
d
v v v P v g T T S
dt
H vH k T
t


   
 
+  =
+  = − +  + − +

+  =  

The two-dimensional simulation is done by using Finite Volume Method (FVM). The validation is done on
the 30 mm by 30 mm square enclosure. The bottom wall of the enclosure made up of aluminum material is
hot with a uniform temperature while the top cold wall is also made up of aluminum material and is
maintained at a constant. The left and right-side walls of the square enclosure are adiabatic for which a low
thermal conductive Plexiglas material is chosen. Pure paraffin wax is selected as PCM.
T
Fig.2. Validation with Saleel [3] and present work
Fig.4. Contours of Mass Fraction, Temperature Distribution, and Velocity Magnitude for the case of without fin for 200 seconds
Fig.5. Contours of Mass Fraction, Temperature Distribution, and Velocity Magnitude for the case of with fin 200 seconds
Fig.6. Comparison of (a) liquid fraction versus time, (b) temperature profile versus time between the cases for with fin and without fin
The heat transfer method is changing with the gradual progression of melting. Initially, the heat is
transferred mainly by means of conduction. As solid PCM continues to melt and because of the density
difference hot fluid moves in the upward direction and hence, natural convection initiates The melting rate
slows down in the bottom position. The addition of fins can significantly improve the melting fraction and
consequently the overall heat transfer with a reduced quantity of PCM.
Improvement can be done to increase the heat transfer between the heat transfer fluid (HTF) and phase-
changing material (PCM) by finding the optimum numbers of fin and optimizing the use of phase-
changing material.
Fig.1. (a) Three-dimensional model, and (b) cross-section of the proposed model with dimension
(a) (b)
SUPERVISOR: HM Toufik Ahmed Zisan | Lecturer, Dept. of Mechanical Engineering
Joy Raj Bhowmik (2018339064) | Md Sojib Mia (2018339006)
(a) (b)
Outer Shell
Inner Tube
Fin
where, ρ is the density of the PCM, ѵ is the velocity vector, Р is the pressure, μ is the viscosity, β is
the thermal expansion coefficient, Т is the temperature of the cell, Тref is the reference temperature, Ѕ is
the source term, Н is the enthalpy of the cell, and к is the thermal conductivity of the PCM. An
enthalpy-porosity model is used to describe the unsteady flow and heat transfer characteristics during
the melting process.
Fig.3. Contours of Mass Fraction for 12 seconds, 45 seconds, and 110 seconds