Experimental hydrothermal characteristics of concentric tube heat exchanger with V-cut twisted tape turbulator using PCM dispersed mono/hybrid nanofluids

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.

KEYWORDS:

• hybrid nanofluid
• phase change material
• V-cuts twisted tape
• heat transfer coefficient
• pressure drop
• entropy generation

Nomenclature

$c_p$:  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

S_gen:  Entropy generation (W.K⁻¹)

T:  Temperature (K)

$\dot{V}$:  Volume flow rate (lpm)

v:   Fluid velocity (m.s⁻¹)

Greek Symbols

$\mathrm{\varnothing }$:  Particle volume concentration

µ:  Dynamic viscosity (Pa.s)

$\rho$:  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