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ABSTRACT
Tubular solar still (TSS) is drawing more attention from researchers due to its compact design with many advantages. This study developed a 3-dimensional, 2-phase numerical model tubular for solar still with a parabolic concentrator solar tracking system (PCST-TSS) to study its performance with a negative static pressure caused by a static water column. The developed model can calculate the amount of freshwater production and the gas mixture phase’s temperature. The model was validated by comparing the simulation results, e.g. for water temperature, vapor temperature, and distillate output, with real-field experimental results. Results showed a significant enhancement of the PCST-TSS performance under negative static pressures. Reducing the operating pressure from 100 to 40 kPa enhanced the productivity and thermal efficiency of the PCST-TSS by 53.2% and 57.4%, respectively. Moreover, the CPL was decreased to a very competitive cost of $0.00557 at 40 kPa. The device productivity reached 7.2 L/m2day, which is suitable for the essential water needs of one person in small communities and remote areas without infrastructure.
Highlights
3-D and 2-phase theoretical model has been developed for tubular solar still
The recommended range of the operating pressure is estimated from 40 to 50 kPa
Using 40 kPa reduced the water production cost by 34.7% reaching $0.00557/L
Reducing the operating pressure to 40 kPa enhanced the device efficiency by 57.4%
Nomenclature
| A | = | area (m2) |
| = | temperature difference fraction (-) | |
| = | specific heat (J/kg.K) | |
| = | molecular diffusion coefficient (m2/s) | |
| h | = | convective heat transfer coefficient (W/m2K) |
| hfg | = | latent heat (J/kg) |
| = | thermal conductivity (W/m.k) | |
| = | molecular weight (kg/kmol) | |
| m | = | Mass (kg) |
| PAA | = | Principle accrued amount ($) |
| Q | = | heat (J) |
| r | = | interest rate (%) |
| = | Rayleigh number (-) | |
| = | universal gas constant (8315 J/kmol/K) | |
| = | gas constant of water vapor (461.5 J/kg K) | |
| s | = | solar intensity (W/m2) |
| T | = | temperature (oC or K) |
| TAA | = | total accrued amount ($) |
| t | = | Time (s) |
| w | = | width (m) |
| Subscripts | = | |
| a | = | air |
| amb | = | ambient |
| b | = | basin |
| c | = | condensation |
| cond | = | conduction |
| conv | = | convective |
| d | = | distillate |
| e | = | envelope |
| ev | = | evaporation |
| g | = | gas |
| l | = | liquid |
| rad | = | radiation |
| v | = | vapor |
| va | = | vapor at humid air |
| w | = | water |
| Greek symbols | = | |
| = | thermal diffusivity (m2/s) | |
| = | volumetric thermal expansion coefficient (1/K) | |
| = | characteristic length (m) | |
| ε | = | emissivity (-) |
| = | temperature difference (K) | |
| = | efficiency (%) | |
| = | coefficient (-) | |
| = | dynamic viscosity (Pa.s) | |
| = | density (kg/m3) | |
| ϕ | = | reflectivity (-) |
| Abbreviations | = | |
| AWH | = | atmospheric water harvesting |
| BSS | = | basin solar still |
| CSHSTs | = | composite sensible heat storage tubes |
| CPL | = | cost per liter |
| IEA | = | international energy agency |
| ISS | = | inclined solar still |
| LDRs | = | light-dependent resistors |
| LNG | = | liquefied natural gas |
| MSF | = | multi-stage flash |
| OTSS | = | oval tubular solar still |
| PCM | = | phase change material |
| PCST | = | parabolic concentrator solar tracking |
| PMMA | = | polymethylmethacrylate |
| PV | = | photovoltage |
| PVT | = | photovoltage thermal |
| RH | = | relative humidity |
| TSS | = | tubular solar still |
Acknowledgements
This research has been funded by Scientific Research Deanship at University of Ha’il - Saudi Arabia through project number RG-21 020.
Disclosure statement
No potential conflict of interest was reported by the author(s).