PCM-Based Building Envelope Systems pp 147-181 | Cite as

# Heat Transfer Mechanisms in PCM-Based Building Envelope Systems

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## Abstract

To describe physical processes and predict performances of passive buildings, various mathematical models have been developed based on numerical and experimental studies. This chapter is a useful reference for researches, academicians, professionals, and students regarding the passive building design in terms of energy storage within PCM, heat transfer through building envelope as well as airflow rate through a solar chimney.

## Nomenclature

## .

*C*Coefficient

*g*Gravity acceleration, m/s

^{2}*U*Overall heat transfer coefficient/

*U*-factor, W/m^{2}K*H*Height, m

*A*Area, m

^{2}*c*_{p}Specific heat, J/kg °C

*T*Temperature, °C

*h*Convective heat transfer coefficient, W/m

^{2}K*β*Fraction of melted PCM

*m*Mass, kg

- \(\dot{q}\)
Heat flux in positive direction, W/m

^{2}- \(\dot{Q}\)
Heat flow, W

- \(\dot{q}\)
Heat flux, W/m

^{2}*I*Solar irradiance, W/m

^{2}*E*Energy, J

*σ*Stefan–Boltzmann constant (

*σ*= 5.67 × 10^{−8}W/m^{2}K^{4})*ε*Surface emissivity

*λ*Thermal conductivity of material, W/m K

- \(\dot{E}\)
Rate of heat, W

- \(\dot{e}\)
Rate of heat, W/m

^{3}*α*Thermal diffusivity, m

^{2}/s*ρ*Density, kg/m

^{3}*L*Thickness/length, m

*u*Velocity in

*x*-direction, m/s*v*Velocity in

*y*-direction, m/s*w*Velocity in

*z-*direction, m/s*F*Force

*τ*Shear stress tensor, Pa

- \(\hat{\tau }\)
Transmissivity of the surface

*t*Time, s

*μ*Dynamic viscosity of the liquid phase, Pa s

*ψ*_{j}Linear heat transfer coefficient, W/m K

*χ*_{k}Dotted heat transfer coefficient, W/m K

*p*Number of dotted connections.

## Abbreviations

- PCM
Phase change material

- LHES
Latent heat energy storage

- SHES
Sensible heat energy storage.

## Subscripts

- i
Interior

- e
Exterior

- s
Surface

- surr
Surrounding

- in
Inlet

- out
Outlet

- is
Interior side

- d
Discharge

- sc
Solar chimney

- pc
Phase change

- cond
Conduction

- conv
Convection

- R
Radiation

- c
Convection

- T
Total

- cv
Control volume

- gen
Generated

- stored
Stored

- tot
Total.

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