Vol.:(0123456789) 1 3
International Journal of Environmental Science and Technology
https://doi.org/10.1007/s13762-019-02554-6
ORIGINAL PAPER
Experimental investigation of a heat pump‑assisted solar
humidifcation–dehumidifcation desalination system with a free‑fow
solar humidifer
M. Shojaei
1
· H. Mortezapour
1
· K. Jafarinaeimi
1
Received: 10 April 2019 / Revised: 4 August 2019 / Accepted: 25 September 2019
© Islamic Azad University (IAU) 2019
Abstract
Global water scarcity is one of the biggest human concerns in recent decades. Seawater desalination becomes the dominant
way to access the new drinkable waters. The present study developed a heat pump-assisted humidifcation–dehumidifcation
water desalination system. The designed system is equipped with a novel solar humidifer that works based on the free-fow
solar water collectors. The efect of air fow rate and mode of the air circulation system on the performance of the designed
system was experimentally investigated. The results reveal that raising the air fow rate improved water evaporation rate
and the solar humidifer efciency, while closing the air circuit led to a reduction in the evaporation rate. The maximum
evaporation amount and water productivity were around 1.38 and 1 kg/h/m
2
in the average solar irradiance of 877 W/m
2
. The
closed-loop air circulation system resulted in a signifcantly higher efectiveness of dehumidifcation and produced higher
desalinated water compared with the open-circuit mode. The lowest specifc electrical energy consumption and the highest
gained output ratio values of, respectively, 0.15 kWh/kg and 2.36 were observed at the air fow rate of 0.019 m
3
/s/m
2
of solar
humidifer when closing the air circulation system.
Keywords Evaporation rate · Productivity · Air circulation · Specifc energy consumption · Gained output ratio
List of symbols
A Surface area (m
2
)
a Accuracy
E Electrical energy (kWh)
G Solar irradiance (W/m
2
)
GOR Gained output ratio (decimal)
H Specifc enthalpy (J/kg)
L Latent heat (J/kg)
M Mass of desalinated water (kg)
m Mass fow rate (kg/s)
PCF Pre-condenser fraction (decimal)
Q Rate of useful energy gain (W)
SEEC Specifc electrical energy consumption (kWh/kg)
T Temperature (°C)
U Overall heat loss coefcient of solar collector (W/
m
2
/°C)
u Uncertainty
x Measured parameter
y Calculated parameter
Greek letters
Absorption coefcient of absorber plate (decimal)
Thermal efciency (%)
Efectiveness (decimal)
Transmission coefcient of glass cover (decimal)
ω Absolute humidity (kg moisture/kg air)
Subscripts
a Air
amb Ambient
b Brine
c Condensation
DH Dehumidifcation
EC_o Outlet of evaporative condenser
EC_i Inlet of evaporative condenser
el Electrical
HE_i Inlet of heat pump evaporator
HE_o Outlet of heat pump evaporator
Editorial responsibility: M. Abbaspour.
* H. Mortezapour
h.mortezapour@uk.ac.ir
1
Department of Biosystems Engineering, Faculty
of Agriculture, Shahid Bahonar University of Kerman,
Kerman, Iran