ABSTRACT
Impact of using V-cuts twisted tape insert and phase change material (PCM) dispersed mono or hybrid nanofluid on the hydrothermal characteristics of the double tube heat exchanger is experimentally investigated. Water-based Al2O3 and PCM nanofluids and Al2O3+ PCM hybrid nanofluid with different concentrations are used in inner tube. Influences of various geometric parameters of V-cuts twisted tape insert on heat transfer, pressure drop and entropy generation are investigated. Results reveal that heat transfer and pressure drop increase with the increase in particle concentration and decrease in twisting ratio. A higher V-cut depth ratio or lower width ratio yields more heat transfer and pressure drop.
Nomenclature
: Specific heat capacity (J.kg−1.K−1)
d: Tube diameter (m)
D: Width of the twisted tape (m)
f: Friction factor
h: Heat transfer coefficient (W.K−1.m−2)
H: Pitch of the twisted tape (m)
k: Thermal conductivity (W.K−1.m−1)
Nu: Nusselt number
L: Effective tube length (m)
m: Mass flow rate (kg.s−1)
Pr: Prandtl number
Q: Heat transfer rate (W)
Re: Reynolds number
Sgen: Entropy generation (W.K−1)
T: Temperature (K)
: Volume flow rate (lpm)
v: Fluid velocity (m.s−1)
Greek Symbols
: Particle volume concentration
µ: Dynamic viscosity (Pa.s)
: Density (kg.m−3)
∆p: Pressure drop (Pa)
Subscripts
avg: average
c: cold fluid
h: hot fluid
hnf: mono/hybrid nanofluid
i, o: inner, outer
in, out: inlet, outlet
it, ot: inner tube, outer tube
w: tube wall
Abbreviations
DR: Depth ratio
LMTD: Log mean temperature difference
TR: Twist ratio
WR: Width ratio