Nanofluid-based wick-type integrated solar still for improved diurnal and nocturnal distillate production

ABSTRACT

In the present work, a novel “nanofluid-based wick-type integrated solar still” has been designed, fabricated, and tested under on-sun conditions to assess its diurnal and nocturnal performance characteristics. Herein, floating wicks were placed inside the basin of single slope-single basin solar still. Furthermore, the basin water was supplied with external thermal energy collected by a nanofluid-based volumetrically absorbing solar collector (NBVASC) during the sunshine hours (9 am to 6 pm) and from the solar pond during the non-sunshine hours. In essence, the benefits of volumetric as well as surface heating have been synergized to significantly enhance the distillate production rate. Volumetric or bulk heating allows for enhanced sensible heat storage in the NBVASC, and the presence of wicks in the still’s basin lends localized surface heating of basin water – thus considerably improving the evaporation rates. Rigorous on-sun testing of “nanofluid-based wick-type integrated solar still” showed significant improvements relative to the conventional solar still; distillate productivity and efficiency enhancements on the order of 111.1% and 89.9%, respectively, were recorded (with exergy efficiency of 3.40%).

KEYWORDS:

• Nanofluid
• solar distillation
• solar collector
• solar pond
• floating wick

Nomenclature

Ab	=	basin surface area, m2
C	=	specific heat of heat transfer fluid, kJ/kg/K
GT	=	overall solar radiation impinging on the still, kJ/m2/day
hfg	=	latent heat of water, kJ/kg
$\text{dotm}$	=	heat transfer fluid flow rate in the heat exchanger, kg/sec
md	=	mass of distillate, kg
mi	=	yield produced by integrated still, l/m2
mc	=	yield produced by conventional still, l/m2
Pp	=	pump rating, W
Qsc	=	heat energy provided to integrated still from the solar collector, kJ
Qsp	=	heat energy provided to integrated still from the solar pond, kJ
$\mathrm{\Delta }t$	=	average temperature difference of HTF at inlet & outlet of basin still HE, oC
Wp	=	pump work, kJ

Greek letters

$\eta$	=	efficiency, %
$\tau$	=	overall running time of the pump, sec

Abbreviations

CPVC	=	CS:chlorinated polyvinyl chlorideconventional Still
HE	=	heat exchanger
HTF	=	heat transfer fluid
NBVASC	=	nanofluid based volumetric absorption solar collector
PBSASC	=	paraffin-oil based surface absorption solar collector
SSSB	=	single slope single basin

Acknowledgement

It is a pleasure to acknowledge the Department of Mechanical Engineering, Thapar Institute of Engineering and Technology, Patiala, Punjab, India for providing facilities and continuous support to carry out research work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Jagteshwar Singh

Jagteshwar Singh is a research scholar in the Mechanical Engineering Department at Thapar Institute of Engineering and Technology, Patiala, Punjab, India. His research interests include solar distillation, solar collectors and nanofluids application in desalination.

Madhup Kumar Mittal

Dr Madhup Kumar Mittal is an Associate professor in the Mechanical Engineering Department at Thapar Institute of Engineering and Technology, Patiala, Punjab, India. His research area is solar energy and its application in solar desalination, solar pond, solar air heating and solar water heating. Heat transfer and refrigeration & air-conditioning. He has numerous international and national publications and completed research projects under DST.

Vikrant Khullar

Dr Vikrant Khullar is working as an associate professor in the Mechanical Engineering Department at Thapar Institute of Engineering and Technology, Patiala, Punjab, India. His research interests include heat transfer, solar thermal and nanofluids. He has undertaken various research projects and published a number of research papers in journals of International repute.