2. How to design building envelope with phase change materials

In this part, a kind of PCM-based lightweight wallboards which integrates PCMs with insulation materials is put forward. In application, the different PCM layer arrangements and the different PCM layout areas are significant to thermal performance of the wallboards. Current thermal design calculation of PCM-based envelope is mainly based on numerical methods. Although the numerical methods could obtain the wall temperature accurately, it is difficult to provide amounts of parameters and build models for architects. Therefore, in order to provide reference for the estimation of PCM-based envelope application effects, a thermal design calculation method is proposed, which is based on harmonic response method and equivalent specific heat capacity principle and is verified with experimental results. The present part mainly contains two points as follows: (1) a comparative experimental investigation with reduce-scale in the controlled condition, and (2) a simple thermal design method is developed based on harmonic response method and equivalent specific heat capacity principle.

## 2.1 Reduce-scale experiments

The experiments are conducted in the Thermal Storage and Ventilation Laboratory (TSVL) in Xi'an University of Architecture and Technology, Shaanxi, China. The lab consists of artificial climate chamber and control system, which can simulate the outdoor thermal environment including temperature and humidity. The temperature can be controlled by setting curves. Two test cells are adopted in the comparative experiments. The length, width, and height in each test cell are 1200mm, 660mm, and 800 mm, respectively. To exclude the uncontrollable factor Building Envelope with Phase Change Materials DOI: http://dx.doi.org/10.5772/intechopen.85012

influence, the wallboards of test cell are made by 100 mm expandable polystyrene (EPS) panels which can be considered as adiabatic. In the experiments, PCM-based lightweight wallboard is adopted to replace one of EPS panel (see Figure 2). The macro-encapsulated PCM panels are employed in the experiments. The encapsulated PCMs are CaCl2�6H2O, whose phase change temperature is 25–27°C. In melting process, the latent heat is 122.3 kJ�kg�<sup>1</sup> , and in solidification process the latent heat is 116.9 kJ�kg�<sup>1</sup> .

The experimental wallboard named PCM-based lightweight wallboard is put forward. The wallboard is made by 20 mm PCM layer and 30 mm insulation material layer. The wallboard improves its thermal storage capacity obviously by utilizing PCMs while sacrificing a fraction of insulation performance. The PCMbased lightweight wallboard is divided into PCM part and insulation part to distinguish whether there are PCMs in the horizontal direction.

r<sup>A</sup> is defined as the ratio of PCM part area to wallboard area:

$$r\_{\rm A} = \frac{A\_{\rm PCM}}{A\_{\rm ALL}} \tag{1}$$

where APCM is the area of PCM and AALL is the area of the wallboard. The wallboards with four r<sup>A</sup> are compared in experiments: 0, 21.6, 43.3, and 65%.

The reference group (r<sup>A</sup> = 0%) is performed firstly to benchmark the PCMbased lightweight wallboard experiments. Figure 3 shows the temperature curves of reference group during harmonic temperature changing process. Comparing the

Figure 2. PCM-based lightweight wallboard.

Figure 3. Temperature under harmonic temperature fluctuation.

thermal storage performance in lightweight structures widely developing in recent years. Due to large thermal capacity, phase change materials (PCMs) are ideal thermal storage materials to be integrated with building envelope [9]. As shown in Figure 1, building envelope integrated with PCMs can improve thermal inertia of lightweight structures and further stabilize indoor thermal environment [10]. Therefore, the thermal performance of PCM-based envelope has attracted more

2. How to design building envelope with phase change materials

In this part, a kind of PCM-based lightweight wallboards which integrates PCMs with insulation materials is put forward. In application, the different PCM layer arrangements and the different PCM layout areas are significant to thermal performance of the wallboards. Current thermal design calculation of PCM-based envelope is mainly based on numerical methods. Although the numerical methods could obtain the wall temperature accurately, it is difficult to provide amounts of parameters and build models for architects. Therefore, in order to provide reference for the estimation of PCM-based envelope application effects, a thermal design calculation method is proposed, which is based on harmonic response method and equivalent specific heat capacity principle and is verified with experimental results. The present part mainly contains two points as follows: (1) a comparative experimental investigation with reduce-scale in the controlled condition, and (2) a simple thermal design method is developed based on harmonic response method and

The experiments are conducted in the Thermal Storage and Ventilation Laboratory (TSVL) in Xi'an University of Architecture and Technology, Shaanxi, China. The lab consists of artificial climate chamber and control system, which can simulate the outdoor thermal environment including temperature and humidity. The temperature can be controlled by setting curves. Two test cells are adopted in the comparative experiments. The length, width, and height in each test cell are 1200mm, 660mm, and 800 mm, respectively. To exclude the uncontrollable factor

attention in recent years.

Principle of PCM-based envelope.

Zero and Net Zero Energy

Figure 1.

equivalent specific heat capacity principle.

2.1 Reduce-scale experiments

12

exterior and interior air temperature, the maximum temperature difference is 2.8° C, and the lag time is 2.5 h. The results prove that the insulation wallboard with poor thermal storage capacity is insufficient for the stability of indoor thermal environment.

Figure 4 shows the temperature and feat flux curves of the PCM-based lightweight wallboard (r<sup>A</sup> = 65%) under harmonic temperature changing process. Due to the weak thermal inertia of insulation materials, the temperature changing of interior air is faster than the interior surface temperature changing of the PCM-based lightweight wallboard. It can be seen from the heat flux curves that the heat flux is delayed as much as 14.4 h. It is corresponding accurately between the largest temperature difference and the heat flux peak.

The temperature of the exterior/interior surfaces under the harmonic mode is shown in Figure 5. The temperature of interior surface and air is more stable in cell 1 (interior surface arrangement of PCM layer) than in cell 2 (exterior surface arrangement of PCM layer). The results show that the interior surface arrangement of PCM layer can reduce temperature amplitude in interior air to 32.1%. It proves that the PCM layer should be arranged on interior surface to improve thermal performance of PCM-based envelope.

Figure 6 illustrates the heat flux curves in PCM-based lightweight wallboards surfaces during the harmonic process. Because the PCMs are exposed to exterior air in cell 2, the heat flux amplitude of exterior surface is larger than in cell 1. Meanwhile, because most of the incoming heat is absorbed by the PCM directly,

Heat flux curves in PCM-based lightweight wallboards surfaces during the harmonic process.

It can be proved by the experimental results that PCM layer with interior surface arrangement could achieve excellent performance to adjust indoor thermal environment. Although the PCM layer with exterior surface arrangement could absorb more heat from ambient environment, the PCMs cannot directly regulate the indoor thermal environment. By absorbing indoor excess heat, the PCM layer on interior surface can stabilize the indoor thermal environment. Therefore, it is a suitable approach to arrange the PCM layer on the interior surface of building

As a traditional thermal design method of building envelope, harmonic response method can obtain the temperature fluctuation attenuation and delay time of normal envelope such as concrete and brick structures [11]. The method is widely accepted by engineers [12]. A simple thermal design method named HR-EC (harmonic response method and equivalent specific heat capacity principle) is proposed based on harmonic response method and equivalent specific heat capacity principle. The PCM-based envelope is different from normal envelope. During the phase change process, the latent heat will cause changing apparent specific heat. Therefore, to conveniently calculate the impact of latent heat, the calculation method adopts the equivalent specific heat capacity principle to simplify latent heat [13]. The temperature amplitude and delay time of interior surface of PCM-based lightweight wallboard are calculated and verified by comparing with the experimental

The HR-EC thermal design method is based on the harmonic response method, which is developed based on heat transfer analysis through building walls using Fourier transforms. Harmonic response method is a simple calculation method to obtain temperature damping and time delay of the walls without the analysis of heat transfer process. Therefore, it is a useful approach in the PCMs envelope thermal

Damping factor (v0) of outdoor air temperature to wall interior surface temper-

the heat flux fluctuation on interior surface of cell 2 is less.

Building Envelope with Phase Change Materials DOI: http://dx.doi.org/10.5772/intechopen.85012

envelope in the thermal design.

2.2 Thermal design method

results.

Figure 6.

design.

15

ature can be calculated as [12]

#### Figure 4.

Temperature and heat flux distribution of PCM-based lightweight wallboard during harmonic temperature process (rA = 65%).

Figure 5. Surface temperature curves during the harmonic process.

Building Envelope with Phase Change Materials DOI: http://dx.doi.org/10.5772/intechopen.85012

exterior and interior air temperature, the maximum temperature difference is 2.8° C, and the lag time is 2.5 h. The results prove that the insulation wallboard with poor thermal storage capacity is insufficient for the stability of indoor thermal

Figure 4 shows the temperature and feat flux curves of the PCM-based lightweight wallboard (r<sup>A</sup> = 65%) under harmonic temperature changing process. Due to the weak thermal inertia of insulation materials, the temperature changing of interior air is faster than the interior surface temperature changing of the PCM-based lightweight wallboard. It can be seen from the heat flux curves that the heat flux is delayed as much as 14.4 h. It is corresponding accurately between the largest

The temperature of the exterior/interior surfaces under the harmonic mode is shown in Figure 5. The temperature of interior surface and air is more stable in cell 1 (interior surface arrangement of PCM layer) than in cell 2 (exterior surface arrangement of PCM layer). The results show that the interior surface arrangement of PCM layer can reduce temperature amplitude in interior air to 32.1%. It proves that the PCM layer should be arranged on interior surface to improve thermal

Figure 6 illustrates the heat flux curves in PCM-based lightweight wallboards surfaces during the harmonic process. Because the PCMs are exposed to exterior air

Temperature and heat flux distribution of PCM-based lightweight wallboard during harmonic temperature

environment.

Zero and Net Zero Energy

Figure 4.

Figure 5.

14

Surface temperature curves during the harmonic process.

process (rA = 65%).

temperature difference and the heat flux peak.

performance of PCM-based envelope.

Figure 6. Heat flux curves in PCM-based lightweight wallboards surfaces during the harmonic process.

in cell 2, the heat flux amplitude of exterior surface is larger than in cell 1. Meanwhile, because most of the incoming heat is absorbed by the PCM directly, the heat flux fluctuation on interior surface of cell 2 is less.

It can be proved by the experimental results that PCM layer with interior surface arrangement could achieve excellent performance to adjust indoor thermal environment. Although the PCM layer with exterior surface arrangement could absorb more heat from ambient environment, the PCMs cannot directly regulate the indoor thermal environment. By absorbing indoor excess heat, the PCM layer on interior surface can stabilize the indoor thermal environment. Therefore, it is a suitable approach to arrange the PCM layer on the interior surface of building envelope in the thermal design.

#### 2.2 Thermal design method

As a traditional thermal design method of building envelope, harmonic response method can obtain the temperature fluctuation attenuation and delay time of normal envelope such as concrete and brick structures [11]. The method is widely accepted by engineers [12]. A simple thermal design method named HR-EC (harmonic response method and equivalent specific heat capacity principle) is proposed based on harmonic response method and equivalent specific heat capacity principle. The PCM-based envelope is different from normal envelope. During the phase change process, the latent heat will cause changing apparent specific heat. Therefore, to conveniently calculate the impact of latent heat, the calculation method adopts the equivalent specific heat capacity principle to simplify latent heat [13]. The temperature amplitude and delay time of interior surface of PCM-based lightweight wallboard are calculated and verified by comparing with the experimental results.

The HR-EC thermal design method is based on the harmonic response method, which is developed based on heat transfer analysis through building walls using Fourier transforms. Harmonic response method is a simple calculation method to obtain temperature damping and time delay of the walls without the analysis of heat transfer process. Therefore, it is a useful approach in the PCMs envelope thermal design.

Damping factor (v0) of outdoor air temperature to wall interior surface temperature can be calculated as [12]

$$w\_0 = 0.9e^{\frac{\Sigma^0}{\sqrt{2}}} \cdot \frac{\mathcal{S}\_1 + a\_\text{i}}{\mathcal{S}\_1 + Y\_{\text{1,e}}} \cdot \frac{\mathcal{S}\_2 + Y\_{\text{1,e}}}{\mathcal{S}\_2 + Y\_{\text{2,e}}} \cdot \dots \frac{\mathcal{S}\_\text{n} + Y\_{\text{n-1,e}}}{\mathcal{S}\_\text{n} + Y\_{\text{n,e}}} \cdot \frac{a\_\text{e} + Y\_{\text{n,e}}}{a\_\text{e}} \tag{2}$$

where ΣD is thermal inertia of building wall, S<sup>n</sup> is coefficient of heat accumulation of wall materials, Yn,e is coefficient of heat accumulation of the outer surface of material layer, α<sup>i</sup> is interior surface coefficient of heat transfer, and α<sup>e</sup> is exterior surface coefficient of heat transfer.

D is thermal inertia of wall material layer. It can be defined as

$$D = R \cdot \mathbb{S} \tag{3}$$

<sup>ξ</sup>if <sup>¼</sup> <sup>Z</sup>

cL p cM <sup>p</sup> <sup>þ</sup> <sup>c</sup> <sup>∗</sup> p cS p

> c ∗ <sup>p</sup> <sup>¼</sup> <sup>Δ</sup><sup>h</sup> ΔT<sup>R</sup>

λL p

<sup>p</sup> is the thermal conductivity in solid phase and λ<sup>L</sup>

λS <sup>p</sup> þ λL <sup>p</sup> � <sup>λ</sup><sup>S</sup> p ΔT<sup>R</sup> λS p

8 >>>><

>>>>:

equivalent specific heat capacity (cp) is defined as [13].

Building Envelope with Phase Change Materials DOI: http://dx.doi.org/10.5772/intechopen.85012

cp ¼

where c<sup>L</sup>

where λ<sup>S</sup>

ductivity in liquid phase.

tude and delay time.

Table 1.

17

as [13]

capacity in solid phase, and c<sup>M</sup>

8 >><

>>:

<sup>p</sup> is the specific heat capacity in liquid phase, c<sup>S</sup>

and Δh is the latent heat of phase change process. Δh is obtained as

λ<sup>p</sup> ¼

<sup>360</sup> <sup>Φ</sup>if <sup>¼</sup> <sup>1</sup>

It is necessary to determine the calculation parameters. The equivalent specific heat capacity principle is adopted to convert the latent heat to a constant value. The

<sup>p</sup> is the average value of c<sup>L</sup>

where ΔT<sup>R</sup> is the temperature range during the complete phase change process

where ΔH is the latent heat of the PCM and ratio is the phase change ratio of PCMs during phase change process. In the phase change process, the thermal conductivity of the PCM is also replaced as equivalent thermal conductivity [13]:

The results are listed in Table 1. The calculated results are close to the experimental results with 7.7% relative error. The results of interior surface temperature delay time have larger relative error with 33.2%. As an estimated method used in early design, the method is an easy way to predict the trend of temperature ampli-

For the calculation of temperature damping factor and delay time by HR-EC method, the input parameters of wall materials are necessary to be determined, including thermal conductivity (λ), density (ρ), specific heat capacity (c), and material layer thickness (d). In addition, the equivalent specific heat capacity (cp) is also a significant parameter for the calculation of PCM-based envelope thermal

Temperature amplitude 4.06°C 4.40°C 7.7 Temperature delay time 3.38 h 5.06 h 33.2

Calculated and experimental results of PCM-based lightweight wallboard.

ð Þ T . TL

ð Þ TS . T

ð Þ TL ≥ T ≥TS

Calculated results Experimental results Relative error (%)

15

ð Þ T . TL

ð Þ TS . T

ð Þ TL ≥T ≥ TS

Φif (11)

<sup>p</sup> is the specific heat

<sup>p</sup> can be calculated

p; c <sup>∗</sup>

<sup>p</sup> and c<sup>S</sup>

Δh ¼ ΔH � ratio (14)

(12)

(13)

(15)

<sup>p</sup> is the thermal con-

where R is thermal resistance of wall material layer and S is coefficient of heat accumulation of wall material. Thermal inertia represents the performance of material layers to resist the effects of fluctuating temperature, which is reflected by the temperature fluctuations of back of the material layer. ΣD can be obtained as

$$
\Sigma D = D\_1 + D\_2 + \dots + D\_n \tag{4}
$$

where D<sup>1</sup> , D2…D<sup>n</sup> are the thermal inertia of each material layer of the wall. S<sup>n</sup> and Y<sup>n</sup> are expressed as follows [12]:

$$\mathbf{S\_n} = \sqrt{\frac{2\pi\lambda c\rho}{Z}}\tag{5}$$

$$Y\_{\mathbf{n}} = \frac{R\_{\mathbf{n}} S\_{\mathbf{n}^2} + Y\_{\mathbf{n-1}}}{1 + R\_{\mathbf{n}} Y\_{\mathbf{n-1}}} \tag{6}$$

where λ is thermal conductivity, c is specific heat capacity, ρ is wall materials density, and Z is period of temperature fluctuation.

Phase delay (Φ0) between the maximum temperature of outdoor air and the maximum temperature of wall interior surface is calculated by [12]

$$\Phi\_0 = 40.5 \sum D + \arctan \frac{Y\_{\text{ef}}}{Y\_{\text{ef}} + a\_{\text{e}} \sqrt{2}} - \arctan \frac{a\_{\text{i}}}{a\_{\text{i}} + Y\_{\text{if}} \sqrt{2}} \tag{7}$$

where Yef is coefficient of heat accumulation of wall outer surface and Yif is coefficient of heat accumulation of wall inner surface. Because the temperature period is 24 h in building thermal design, the delay time (ξ0) can be obtained as [12]

$$
\xi\_0 = \frac{Z}{360} \Phi\_0 = \frac{1}{15} \Phi\_0 \tag{8}
$$

Building envelope is always affected by double-side thermal effects including indoor and outdoor temperature changes. Therefore, the damping factor (vif) and time delay (Φif) between indoor air and interior surface temperature of building envelope should also be obtained by the following Equations [12]:

$$v\_{\rm if} = 0.95 \frac{a\_{\rm i} + Y\_{\rm if}}{a\_{\rm i}} \tag{9}$$

$$\Phi\_{\text{if}} = \arctan \frac{Y\_{\text{if}}}{Y\_{\text{if}} + a\_{\text{i}}\sqrt{2}} \tag{10}$$

Building Envelope with Phase Change Materials DOI: http://dx.doi.org/10.5772/intechopen.85012

v<sup>0</sup> ¼ 0:9e

Zero and Net Zero Energy

surface coefficient of heat transfer.

∑Dffi 2 p

S<sup>n</sup> and Y<sup>n</sup> are expressed as follows [12]:

density, and Z is period of temperature fluctuation.

Φ<sup>0</sup> ¼ 40:5∑D þ arctan

� <sup>S</sup><sup>1</sup> <sup>þ</sup> <sup>α</sup><sup>i</sup> S<sup>1</sup> þ Y1, <sup>e</sup>

�

D is thermal inertia of wall material layer. It can be defined as

S<sup>2</sup> þ Y1, <sup>e</sup> S<sup>2</sup> þ Y2, <sup>e</sup>

where ΣD is thermal inertia of building wall, S<sup>n</sup> is coefficient of heat accumulation of wall materials, Yn,e is coefficient of heat accumulation of the outer surface of material layer, α<sup>i</sup> is interior surface coefficient of heat transfer, and α<sup>e</sup> is exterior

where R is thermal resistance of wall material layer and S is coefficient of heat accumulation of wall material. Thermal inertia represents the performance of material layers to resist the effects of fluctuating temperature, which is reflected by the temperature fluctuations of back of the material layer. ΣD can be obtained as

where D<sup>1</sup> , D2…D<sup>n</sup> are the thermal inertia of each material layer of the wall.

r

<sup>Y</sup><sup>n</sup> <sup>¼</sup> <sup>R</sup>nSn2 <sup>þ</sup> <sup>Y</sup><sup>n</sup>‐<sup>1</sup> <sup>1</sup> <sup>þ</sup> <sup>R</sup>nY<sup>n</sup>‐<sup>1</sup>

where λ is thermal conductivity, c is specific heat capacity, ρ is wall materials

Phase delay (Φ0) between the maximum temperature of outdoor air and the

where Yef is coefficient of heat accumulation of wall outer surface and Yif is coefficient of heat accumulation of wall inner surface. Because the temperature period is 24 h in building thermal design, the delay time (ξ0) can be obtained as [12]

<sup>360</sup> <sup>Φ</sup><sup>0</sup> <sup>¼</sup> <sup>1</sup>

Building envelope is always affected by double-side thermal effects including indoor and outdoor temperature changes. Therefore, the damping factor (vif) and time delay (Φif) between indoor air and interior surface temperature of building

<sup>v</sup>if <sup>¼</sup> <sup>0</sup>:<sup>95</sup> <sup>α</sup><sup>i</sup> <sup>þ</sup> <sup>Y</sup>if

Yef Yef þ α<sup>e</sup>

ffiffi 2

15

αi

Yif Yif þ α<sup>i</sup>

ffiffi 2

<sup>p</sup> � arctan <sup>α</sup><sup>i</sup>

α<sup>i</sup> þ Yif

Φ<sup>0</sup> (8)

p (10)

ffiffi 2

p (7)

maximum temperature of wall interior surface is calculated by [12]

<sup>ξ</sup><sup>0</sup> <sup>¼</sup> <sup>Z</sup>

envelope should also be obtained by the following Equations [12]:

Φif ¼ arctan

16

ffiffiffiffiffiffiffiffiffiffiffi 2πλcρ Z

S<sup>n</sup> ¼

� <sup>⋯</sup> <sup>S</sup><sup>n</sup> <sup>þ</sup> <sup>Y</sup>n‐1, <sup>e</sup> S<sup>n</sup> þ Yn, <sup>e</sup>

�

D ¼ R � S (3)

ΣD ¼ D<sup>1</sup> þ D<sup>2</sup> þ ⋯ þ D<sup>n</sup> (4)

α<sup>e</sup> þ Yn, <sup>e</sup> αe

(2)

(5)

(6)

(9)

$$
\xi\_{\text{if}} = \frac{Z}{\mathfrak{Z}\mathfrak{G}\mathfrak{O}} \Phi\_{\text{if}} = \frac{1}{\mathfrak{1}\mathfrak{F}} \Phi\_{\text{if}} \tag{11}
$$

It is necessary to determine the calculation parameters. The equivalent specific heat capacity principle is adopted to convert the latent heat to a constant value. The equivalent specific heat capacity (cp) is defined as [13].

$$\mathcal{cp} = \begin{cases} \mathcal{c}\_{\mathsf{p}}^{\mathsf{L}} & (T > \mathsf{TL}) \\ \mathcal{c}\_{\mathsf{p}}^{\mathsf{M}} + \mathcal{c}\_{\mathsf{p}}^{\*} & (\mathsf{TL} \geq T \geq \mathsf{TS}) \\ \mathcal{c}\_{\mathsf{p}}^{\mathsf{S}} & (T\mathsf{S} > T) \end{cases} \tag{12}$$

where c<sup>L</sup> <sup>p</sup> is the specific heat capacity in liquid phase, c<sup>S</sup> <sup>p</sup> is the specific heat capacity in solid phase, and c<sup>M</sup> <sup>p</sup> is the average value of c<sup>L</sup> <sup>p</sup> and c<sup>S</sup> p; c <sup>∗</sup> <sup>p</sup> can be calculated as [13]

$$c\_{\mathbf{p}}^{\*} = \frac{\Delta h}{\Delta T\_{\mathbf{R}}} \tag{13}$$

where ΔT<sup>R</sup> is the temperature range during the complete phase change process and Δh is the latent heat of phase change process. Δh is obtained as

$$
\Delta h = \Delta H \cdot ratio \tag{14}
$$

where ΔH is the latent heat of the PCM and ratio is the phase change ratio of PCMs during phase change process. In the phase change process, the thermal conductivity of the PCM is also replaced as equivalent thermal conductivity [13]:

$$\lambda\_{\rm P} = \begin{cases} \lambda\_{\rm p}^{\rm L} & (T > T\text{L}) \\ \lambda\_{\rm p}^{\rm S} + \frac{\lambda\_{\rm p}^{\rm S} - \lambda\_{\rm p}^{\rm S}}{\Delta T\_{\rm R}} \left( T\text{L} \ge T \ge T\text{S} \right) \\ \lambda\_{\rm p}^{\rm S} & (T\text{S} > T) \end{cases} \tag{15}$$

where λ<sup>S</sup> <sup>p</sup> is the thermal conductivity in solid phase and λ<sup>L</sup> <sup>p</sup> is the thermal conductivity in liquid phase.

The results are listed in Table 1. The calculated results are close to the experimental results with 7.7% relative error. The results of interior surface temperature delay time have larger relative error with 33.2%. As an estimated method used in early design, the method is an easy way to predict the trend of temperature amplitude and delay time.

For the calculation of temperature damping factor and delay time by HR-EC method, the input parameters of wall materials are necessary to be determined, including thermal conductivity (λ), density (ρ), specific heat capacity (c), and material layer thickness (d). In addition, the equivalent specific heat capacity (cp) is also a significant parameter for the calculation of PCM-based envelope thermal


Table 1.

Calculated and experimental results of PCM-based lightweight wallboard.

performance. It is critical to determine the phase change ratio in phase change process. In this part, it is determined based on experimental results. To provide references for PCM-based envelope thermal design in buildings, the phase change ratio of PCM-based envelope in different climate conditions could be obtained by series of further experiments.
