Heat and Mass Transfer

, Volume 48, Issue 3, pp 439–449 | Cite as

Effects of the heat transfer fluid velocity on the storage characteristics of a cylindrical latent heat energy storage system: a numerical study

Original

Abstract

A numerical study of the effects of the thermal fluid velocity on the storage characteristics of a cylindrical latent heat energy storage system (LHESS) was conducted. Due to the low thermal conductivity of phase change materials (PCMs) used in LHESS, fins were added to the system to increase the rate of heat transfer and charging. Finite elements were used to implement the developed numerical method needed to study and solve for the phase change heat transfer (melting of PCM) encountered in a LHESS during charging. The effective heat capacity method was applied in order to account for the large amount of latent energy stored during melting of the PCM and the moving interface between the solid and liquid phases. The effects of the heat transfer fluid (HTF) velocity on the melting rate of the PCM were studied for configurations having between 0 and 18 fins. Results show that the overall heat transfer rate to the PCM increases with an increase in the HTF velocity. However, the effect of the HTF velocity was observed to be small in configurations having very few fins, owing to the large residual thermal resistance offered by the PCM. However, the effect of the HTF velocity becomes more pronounced with addition of fins; since the thermal resistance on the PCM side of the LHESS is significantly reduce by the large number of fins in the system.

List of symbols

Dimensional variables

Cp

Heat capacity (J kg−1 K−1)

E

Energy (J)

k

Thermal conductivity (W m−1 K−1)

L

Latent heat of fusion (J kg−1)

m

Mass (kg)

P

Pressure (Pa)

r

Radius (m)

r

Cylindrical coordinate (m)

T

Temperature (K)

t

Time (s)

u

Thermal fluid velocity (m s−1)

v

Velocity (m s−1)

X

Solid–liquid interface position (m)

z

Cylindrical coordinate (m)

Greek symbols

Φ

Viscous dissipation (W m−3)

μ

Dynamic viscosity (N s m−2)

ρ

Density (kg m−3)

Non-dimensional variable

n

Normal direction

Subscripts

0

Initial

1

Onset of melting

2

End of melting

eff

Effective

in

Inlet

l

Latent

l

Liquid

p

Pipe

pcm

Phase change material

r

In the r direction

s

Sensible

s

Solid

T

Total

z

In the z direction

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringDalhousie UniversityHalifaxCanada

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