Indicators evaluating thermal inertia performance of envelops with phase change material

Published Date
Energy and Buildings
15 June 2016, Vol.122:175–184, doi:10.1016/j.enbuild.2016.04.009

• Author 

• Haoshu Ling ^a
• Chao Chen ^a,,
• Hong Qin ^b
• Shen Wei ^c
• Jie Lin ^a
• Na Li ^a
• Mingxing Zhang ^a
• Nan Yu ^a
• Yin Li ^a

• aCollege of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100124, PR China
• bDepartment of Construction Engineering, Guangzhou Vocational College of Science and Technology, Guangzhou 510450, PR China
• cFaculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne, NE1 8ST, United Kingdom

Received 19 July 2015. Revised 2 April 2016. Accepted 4 April 2016. Available online 6 April 2016. 

Highlights

• •
  A simplified method calculating the thermal storage coefficient of PCM is proposed.
• •
  The Rayleigh's method in dimensional analysis is introduced and applied.
• •
  Simulation results from EnergyPlus are calibrated against real measured data.
• •
  The thermal inertia performance of building envelops with PCM is evaluated.

Abstract

Phase change material (PCM) has been widely integrated in building envelops to increase their thermal inertia performance. To evaluate the thermal inertia performance of materials and envelops, Chinese Thermal Design Code has provided three indicators, namely, thermal storage coefficient, thermal resistance and thermal inertia index. The existing simplified method calculating the thermal storage coefficient is only applicable for materials with constant thermal properties. For those with varying thermal properties, such as PCM, however, further developments are still required. To solve this issue, both dimensional analysis and numerical simulation were carried out to develop relationships between the thermal storage coefficient of PCM and its other thermal properties (e.g. thermal conductivity, density and the effective equivalent specific heat). Based on the developed relationships, a simplified method calculating the thermal storage coefficient of PCM was proposed in this study. This simplified method was then combined into the thermal inertia index for evaluating the thermal inertia performance of building envelops with PCM.

Abbreviations

PCM, phase change material

EVAC, ethylene vinyl-acetate copolymer

Keywords

Phase change material

Thermal inertia performance

Thermal storage coefficient

Dimensional analysis

Building simulation

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Nomenclature

C

Constant

c

Specific heat capacity (J/kg °C)

D

Thermal inertia index

k

Thermal conductivity (W/m °C)

kg

Dimension of mass

m

Dimension of length

q

Heat flux (W/m²)

R

Thermal resistance (m² °C/W)

s

Dimension of time

t

Temperature (°C)

TSC

Thermal storage coefficient (W/m² °C)

x

Independent variable

y

Variable

Z

Periodic time of the heating effect (s)

ρ

Density (kg/m³)

δ

Thickness (m)

τ

Time (s)

°C

Dimension of temperature

Δh

Enthalpy difference (kJ/kg)

Δ t

Temperature difference (°C)

Subscripts

Br

Brick

i

Node position or serial number

In

Polystyrene board

max

Maximum

min

Minimum

n

Serial number

PCM

phase change material

sum

Sum

wall

Wall

wall, in

Inner surface of wall

wall, out

Outer surface of wall

Superscript

j

Time coordinate

Fig. 1.

Fig. 2.

 Table 1

Table 1.

Fig. 3.

 Table 2

Table 2.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

 Table 3

Table 3.

 Table 4

Table 4.

• ⁎ 
  Corresponding author.

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