Experimental and Numerical Analysis of a PCM-Supported ...
Experimental and Numerical Analysis of a PCM-Supported ...
Experimental and Numerical Analysis of a PCM-Supported ...
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Introduction <strong>of</strong> the indirect type<br />
solar desalination process based<br />
on the (HDH) principle led to a<br />
major improvement in the<br />
efficiency <strong>and</strong> reduction in the<br />
specific collector area. This is<br />
due to energy recovery<br />
mechanisms, extended<br />
evaporation surfaces, <strong>and</strong><br />
enhanced heat <strong>and</strong> mass<br />
transfer coefficients due to the<br />
turbulent flow between air <strong>and</strong><br />
water. Therefore, combining the<br />
principle <strong>of</strong> humidificationdehumidification<br />
with solar<br />
desalination appears to be an<br />
attractive method <strong>of</strong> water<br />
desalination with solar energy.<br />
The HDH technique is especially<br />
Figure 1.6: Schematic diagram <strong>of</strong> a HDH<br />
desalination cycle<br />
suited for seawater desalination when the dem<strong>and</strong> for water is decentralized.<br />
Advantages <strong>of</strong> this technique include flexibility in capacity, moderate installation <strong>and</strong><br />
operating costs, simplicity, <strong>and</strong> possibility <strong>of</strong> using low temperature energy (solar,<br />
geothermal, recovered energy or cogeneration) [2].<br />
1.5 Aim <strong>of</strong> the work<br />
The major aim <strong>of</strong> this study is to examine, characterize, <strong>and</strong> optimize the<br />
performance <strong>of</strong> an innovative “<strong>PCM</strong>-supported HDH system” utilizing spherical<br />
capsules <strong>of</strong> Phase Change Materials (<strong>PCM</strong>) as a packing media in the evaporator,<br />
<strong>and</strong> condenser. The system configuration comprises a closed air loop between the<br />
evaporator <strong>and</strong> condenser. The condenser is <strong>of</strong> direct contact type in a concurrent<br />
flow regime between cooling fresh water <strong>and</strong> humid air. Moreover, a solar thermal<br />
power supply, which consists <strong>of</strong> a solar collector <strong>and</strong> an external thermal storage is<br />
used to drive the HDH plant. The thermal storage is accomplished by storing to <strong>PCM</strong><br />
with melting point around the required output temperature to guarantee 24 hours <strong>of</strong><br />
operation. The <strong>PCM</strong> elements will be integrated in the hot water storage tank in<br />
order to reduce its volume, cost, <strong>and</strong> heat losses.<br />
The objective <strong>of</strong> integration <strong>of</strong> <strong>PCM</strong> packing in the HDH process is for improving the<br />
thermal performance <strong>of</strong> the evaporator <strong>and</strong> condenser <strong>and</strong> not for thermal energy<br />
storage. Under steady state conditions, the main difference between <strong>PCM</strong> packing<br />
<strong>and</strong> other commercially available bed filling materials such as Raschig Rings, Pall<br />
Rings, Berl Saddles or Intalox Saddles, is the thermal conductivity <strong>of</strong> <strong>PCM</strong>, but not<br />
its thermal storage capacity or solid-liquid phase change. Thus this study focuses on<br />
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