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Micro (Mini)-Channels and Their Applications in Solar Systems

  • Thierno DialloEmail author
  • Min Yu
  • Jinzhi Zhou
  • Yi Fan
  • Xudong Zhao
Chapter
  • 577 Downloads
Part of the Green Energy and Technology book series (GREEN)

Abstract

This chapter presented micro (mini)-channels and their applications in solar systems. Two types of channels, micro (mini)-tubes and micro (mini)-heat pipes, have been presented, and the performance of their use in solar systems has been illustrated by studies in the literature. For solar thermal systems, the integration of micro (mini)-channels can increase significantly the thermal performance that achieves an increase of 28% compared to conventional channels. For PVT systems, the use of micro (mini)-channels enhances also the electrical output by decreasing the temperature of PV panels. Consequently, the use of these channels increases the overall efficiency of PVT systems that can achieve the overall efficiency of around 70%. Furthermore, in this paper, the use of micro-channel has been illustrated by the investigation of a novel solar PVT loop heat pipe employing a micro-channel heat pipe evaporator and a PCM triple heat exchanger. This illustration showed environmental parameters (i.e. solar radiation, air temperature, wind velocity), structural parameters (i.e. glazing covers, number of the absorbing heat pipes, PC cell packing factor) and the variable inputs (i.e. water inlet temperature, mass flow rate) that can influence the overall efficiency of the novel PVT system. This chapter showed that application of micro (mini)-channels in solar systems is promising, and their integration in solar technologies can enhance significantly their performance and their market share.

Keywords

Micro-channel Mini-channel Heat pipe Solar application Efficiency PVT systems 

Nomenclature

A

Area (m2)

a

Mini-channel width (m)

b

Mini-channel height (m)

Bo

Bond number (m)

C

Heat capacity (W/K)

C, d

Discharge coefficient (−)

D, d

Diameter (m)

e

Thickness (m)

f

Liquid fraction, friction factor (−)

g

Gravitational acceleration 9.81 (m/s2)

G

Mass velocity (kg/m2/s)

H

Height (m)

h

Heat transfer coefficient (W/m2/K)

hfg

Latent heat of vaporization (J/kg/K)

k

Thermal conductivity (W/m/K)

L

Length (m)

m

Variable (m−1)

N

Number (−)

Nch

Number channel ports (−)

Nu

Nusselt number (−)

P

Pressure (Pa)

ΔP

Pressure drop (Pa)

q

Heat density (W/m2)

Q

Heat transfer rate (W)

Ro

Specific gas constant (J/(kg K))

R

Radius (m)

R

Thermal resistance (W/K)

Re

Reynolds number (−)

t/T

Temperature (°C/°K)

U

Heat loss (W/K)

u

Velocity (m/s)

W

Collector width (m)

x

Vapour quality (−)

Subscripts

an

Annular

av

Average

c

Cold, charge, cover

ch

Channel

cond

Condensation

d

Discharge

f

Fin

F

Efficiency factor

e

Evaporator, electrical

eq

Equivalent

ei

Electrical insulation

EVA

Ethylene-vinyl acetate

fg

Fluid gas

g

Gravity

i

Inlet

min

Minimum

mt

Middle tube

h

Hole, header

he

Heat exchanger

hp

Heat pipe

hp-he

Heat pipe to heat exchanger

lf

The liquid film

lh

Liquid header

LO

Liquid only

ltl

Liquid transportation line

vtl

Vapour transportation line

l

Liquid

L

Loss

lf

Liquid film

o

Overall

out

Outlet

p

PV cell

PCM

Phase change material

Pr

Prandtl

p-fin

PV-fin

th

Thermal

tp

Two phase

u

Utile

v

Vapour

vtl

Vapour transportation line

w

Water

Greek Symbols

β

Packing factor

ε

Efficiency

Δ

Difference

λ

Thermal conductivity (W/(m K))

μ

Dynamic viscosity (Pa s)

ρ

Density (kg/m3)

δ

Thickness (m)

η

Efficiency (m)

σ

Surface tension (N/m)

ν

Specific volume (m3/kg)

Supplementary material

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Thierno Diallo
    • 1
    Email author
  • Min Yu
    • 1
  • Jinzhi Zhou
    • 1
  • Yi Fan
    • 1
  • Xudong Zhao
    • 1
  1. 1.School of Engineering and Computer ScienceUniversity of HullHullUK

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