الخلاصة:
ABSTRACT
The solar water heater system (SWHS) is a well-known renewable energy technology
that has gained a lot of global attention. The main drawback of such a system that it
This work introduces an approach to the
integration of Phase Change Materials (PCMs) within Evacuated Tube Solar Collectors
(ETSC) for SWHS for domestic applications. The benefit of this technique is to enhance
the thermal performance by delaying heat release, thus providing hot water when the
intensity of the solar radiation is insufficient or during high-demand hours. Two models
of ETSC namely: a heat pipe (HP) and a U-shaped tube were experimentally tested with
and without PCM. The SWHS was tested experimentally during normal operation and at
mass flow rate of 0.5,1and1.5 l/min.The simulation model was developed using CFD
ANSYS Fluent R21 to analyze the melting and solidification process of PCM inside Utube
ETSC. The experimental and numerical results showed that the time of the PCM
melting process is directly proportional to the flow rate. The time of the solidification
process is inversely proportional to the flow rate. The time delay for heat stored inside
PCM integrated with HP -ETSC to HTF was approximately 2.16, 1.36 and 1.16 hours,
for HTF flow rate of 0.5, 1and1.5 L/min respectively. The experimental abservations
show that the enhancement efficiency of HP ETSC with integrating of PCM reach up to
28%, 22% and 16% as compared with simple HP-ETSC corresponds to flow rates of 0.5,
1 and 1.5 l/min respectively. The maximum increase in useful energy of HP ETSC was
up to13%, 10% and 2% compared to simple configuration at flow rate of 0.5, 1 and 1.5
l/min respectively. Further the time period for heat release to HTF when using PCM
with U-ETSC was approximately 77 ,60 and 31 min for HTF flow rate of 0.5,1,and 1.5
L/min respectively. However, enhancement in efficiency of U ETSC with integrating of
PCM up to 26%, 20% and 12% at flow rates of 0.5, 1 and 1.5 l/min respectively. as
compared to simple configuration of U-ETSC. The maximum rise in useful energy of U
-ETSC with PCM can be reached up to 15%, 14% 10% at flow rate of 0.5, 1 and 1.5
l/min respectively. compared with simple U-ETSC system. As can be seen that HPETSC
thermal performance is better than U-ETSC by providing a higher difference in
HTF temperature between entry and exit and extended working time of SWHS during
the night or cloudy days when integrated with PCM.
