Energy and exergy study of a novel multi-mode solar dryer without and with sensible heat storage for Garcinia pedunculata

ABSTRACT

In the present analysis, a novel four-mode solar dryer was developed and tested for the drying of Garcinia pedunculata. The four combinations considered were indirect-mode solar dryer without storage (ID-WOS), mixed-mode solar dryer without storage (MX-WOS), indirect-mode solar dryer with storage (ID-WS), and mixed-mode solar dryer with storage (MX-WS). The feature of this dryer that sets it apart is its capability to convert the drying cabinet into various modes simply by sliding the walls of the four sides of the cabinet. The storage system is made space efficient, by filling the gravel up to the surface of the absorber plate inside the solar air collector. For ID-WOS, MX-WOS, ID-WS, and MX-WS, respectively, the drying durations were 30 h, 25 h, 28 h, and 8 h, and the drying efficiencies were 18.55%, 24.03%, 20.32%, and 29.94%. In ID-WOS, MX-WOS, ID-WS, and MX-WS, the average exergy efficiency was determined as 47.08%, 65.10%, 52.46%, and 68.07%, respectively. Environmental impact was studied for all four cases. The energy payback periods for ID-WOS, MX-WOS, ID-WS, and MX-WS were 1.47, 1.61, 1.48, and 1.62 years, respectively. The study indicated that MX-WS outperformed the other three configurations in all aspects.

KEYWORDS:

• Solar dryer
• energy study
• exergy study
• energy payback period
• sensible heat storage

Nomenclature

$\dot{E}$	=	$Energy\left(W\right)$
$\dot{H}$	=	$Netheattransfertosystem\left(W\right)$
$\dot{W}$	=	$Networkdonebysystem\left(W\right)$
$T$	=	$Temperature\left({ }^{\circ }C\right)$
$h$	=	$Enthalpy\left(J/kg\right)$
$V$	=	$Velocity\left(m/s\right)$
$Z$	=	$Heightfromthedatum\left(m\right)$
$C_{pa}$	=	$Specificheatofair\left(J/kgK\right)$
$Exp.$	=	$Experiment$
$A$	=	$Area\left(m2\right)$
$z$	=	$Numberofconstants$
$EPPD$	=	$Energypaybackperiod\left(year\right)$
$Q_L$	=	$Latentheatofvaporizationofwater\left(J/kg\right)$
$m_w$	=	$Amountofmoistureevaporated\left(kg\right)$
$m_i$	=	$InitialmassoftheGP\left(kg\right)$
$m_j$	=	$FinalmassoftheGP\left(kg\right)$
$M{C}_{GP}$	=	$Moisturecontentattime{t}^{\prime }\left(\mathrm{\%}\right)$
$M_{GP,e}$	=	$Moisturecontentatequilibrium\left(\mathrm{\%}\right)$
$M_{GP,i}$	=	$Moisturecontentattimet=0^{\prime }\left(\mathrm{\%}\right)$
$MR$	=	$Moistureratio$
$\dot{E}x$	=	$Exergy\left(W\right)$
$n$	=	$Numberofobservations$
$I$	=	$SolarRadiation\left(W{m}^{-2}\right)$
Greek symbols	=
$\alpha$	=	$Absorptivity$
$\tau$	=	$Transmissivity$
${\eta }_{e,SAC}$	=	$ThermalefficiencyoftheSAC\left(\mathrm{\%}\right)$
${\eta }_{e,dry}$	=	$Overalldryerefficiency\left(\mathrm{\%}\right)$
${\eta }_{Ex,SAC}$	=	$ExergyefficiencyoftheSAC\left(\mathrm{\%}\right)$
${\eta }_{Ex,dc}$	=	$Exergyefficiencyofthedryer\left(\mathrm{\%}\right)$
Subscripts	=
$i$	=	inlet
$o$	=	Outlet
$m$	=	mass
$u$	=	useful
$c$	=	collector
$l$	=	loss
$ex$	=	experimental
$pr$	=	predicted
$a$	=	air
$in$	=	input
$out$	=	output
$md$	=	Mixed-mode dryer
$sys$	=	system
$SAC$	=	Solar air collector
$avp$	=	average predicted
$dry$	=	dryer
$dc$	=	Drying chamber
$\mathrm{\infty }$	=	atmosphere

Disclosure statement

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

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Notes on contributors

Pooja Dutta

Pooja Dutta is a PhD scholar and Teaching Assistant in the Mechanical Engineering Department, Tezpur (Central) University, Assam, India.

Partha Pratim Dutta

Partha Pratim Dutta is working as a Professor in the Mechanical Engineering Department, Tezpur (Central) University, Assam, India, since 2007. He is actively working in Renewable Energy, Solar Thermal Energy, Drying Technology, and so on.

Paragmoni Kalita

Paragmoni Kalita is working as an Associate Professor in the Mechanical Engineering Department, Tezpur (Central) University, India, since 2008. He is actively working in Renewable Energy, Computational Fluid Dynamics, Gas Dynamics, etc