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Research Papers

Air-Heating Solar Collectors for Humidification-Dehumidification Desalination Systems

[+] Author and Article Information
Edward K. Summers

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02319-4307 USAesummers@mit.edu

John H. Lienhard1

Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02319-4307 USAesummers@mit.edu

Syed M. Zubair

Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabiasmzubair@kfupm.edu.sa

1

Corresponding author.

J. Sol. Energy Eng 133(1), 011016 (Feb 14, 2011) (6 pages) doi:10.1115/1.4003295 History: Received May 16, 2010; Revised October 27, 2010; Published February 14, 2011; Online February 14, 2011

Relative to solar water heaters, solar air heaters have received relatively little investigation and have resulted in few commercial products. However, in the context of a humidification-dehumidification (HDH) desalination cycle, air heating accounts for advantages in cycle performance. Solar collectors can be over 40% of an air-heated HDH system’s cost; thus, design optimization is crucial. Best design practices and sensitivity to material properties for solar air heaters are investigated, and absorber solar absorptivity and glazing transmissivity are found to have the strongest effect on performance. Wind speed is also found to have an impact on performance. Additionally a well designed, and likely low cost, collector includes a double glazing and roughened absorber plates for superior heat transfer to the airstream. A collector in this configuration performs better than current collectors with an efficiency of 58% at a normalized gain of 0.06Km2/W.

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Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A typical air-heated HDH cycle

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Figure 2

A closed air HDH cycle as developed by Narayan (5)

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Figure 3

Normalized comparison of solar air heaters in literature. “E” denotes an experimental study and “T” denotes a theoretical study (6).

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Figure 4

Diagram of heater cross-section

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Figure 5

Heat transfer resistances with lumped parameters

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Figure 6

Effect of emissivity, absorber absorptivity, and glazing transmissivity on collector efficiency

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Figure 7

Effect of design enhancements on collector performance

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Figure 8

Comparison of baseline design (double glazed, rough, nonselective absorber) with existing air heaters

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Figure 9

Collector efficiency vs normalized gain for different wind speeds

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Figure 10

Effect of wind speed on collector performance at different absorber IR emissivity

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Figure 11

Effect of wind speed on collector performance at different glazing IR emissivity

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