Parametric study of portable solar-powered heat exchanger using computational fluid dynamics
Water is important for human. Its importance is highlighted by the United Nation as decade for clean water in the world populations suffer lack of portable water in stressed area such as Africa and South East Asia. Therefore, solar powered water distillation system is important, especially for po...
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/67075/1/FK%202016%20177%20IR.pdf |
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| Summary: | Water is important for human. Its importance is highlighted by the United Nation as
decade for clean water in the world populations suffer lack of portable water in
stressed area such as Africa and South East Asia. Therefore, solar powered water
distillation system is important, especially for portable devices seems necessary. This
study is concerned with parametric of heat exchanger for a portable telescopic solar
powered water distiller. The water supply for the distiller is untreated water from rain
water, tube well or flood water. The solar powered water distiller was a Master thesis
project completed in 2014 but the heat exchanger requires further improvement on
design and fabrication. Presently, the water distiller can produce 10L per day in good
sunny weather. The shell and tube heat exchanger with parabolic trough collector
(PTC) have potential to increase performance using computational fluid dynamics to
produce clean water. Design geometry of heat exchanger was based on the conditions
of high-pressure difference between the fluids. The setting of cooling temperature of
water inlet is 31°C and water outlet is 29.8°C. However, the tube for fluid inlet is water
vapour at 82°C and the temperature outlet is at 38°C. Water vapour comes into tube
heat exchanger from the parabolic thermal collector (PTC). The methodology involves
using computational fluid dynamics RNG k-epsilon turbulence flow model. The
model was applied using CFD (computational fluid dynamics) package conjunction
with conjugated heat transfer to predict the flow behavior inside the heat exchanger
for both vapour and liquid water flow. Both heat conduction and heat convection are
taken into account for this 3D computational method to determine fluid flow and
temperature distribution. Parameters considered for design (shell diameter, number of
tubes, baffles, temperature difference, velocity of fluid and heat transfer coefficient
involved) can be used to develop optimum design of heat exchanger and also through
selection of suitable materials. The material construction is a very important aspect in
the design for heat exchanger to ensure operating conditions fabrication technique and
safe drinking water is produced at a minimum cost and low maintenance. Selected
materials have to view the shape design are able to withstand high temperatures and
pressures for heat exchanger to perform efficiently. The analysis compares actual experimental result and defines the suitable material and the best thermal efficiency
on the shell in tube heat exchanger. A multiple baffled shell-and-tube heat exchanger
design performance is evaluated numerically using CFD (computational fluid
dynamics) modeling approach. The field heat exchanger consists of two tubes inside
a 0.535 m long and 0.140 m diameter shell. The simulated results are found to be in
good agreement with the experiment data. Different materials for the heat exchanger
used are stainless steel, copper and aluminum and their performances for a heat
exchanger are compared. From the results, it is found that the temperature difference
between the vapour outlet and water outlet is least in the case of copper and aluminum
as a solid material. Thus, it can be concluded that the copper and aluminum material
is giving highest heat transfer to the water. Using copper for heat exchanger can be
very expensive and the produced water is not safe to be used for drinking compared
to water produced with stainless steel. High heat transferred to the water will help in
the sanitising process of the water. Sanitising is a process in which water is cleaned
by the use of heat, to turn the water into a usable form. |
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