Temperature reduction due to the application of phase change materials

TLDR: In this article, a modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction, where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding.

About: This article is published in Energy and Buildings.The article was published on 2008-01-01 and is currently open access. It has received 184 citations till now. The article focuses on the topics: Thermal mass & Thermal energy storage.

Figures

Table 7: Used PCM in the experimental object

Table 6: Composition of the experimental objects envelopes

Fig. 8. Indoor temperature (grey without PCM, black with PCM), ambient temperature (dotted).

Fig. 7. Limits of the functional capability during a heat wave in summer 2005: air temperature (grey without PCM, black with PCM), ambient temperature (dotted).

Fig. 9. Comparison of the paek temperatures.

Table 1: Thermophysical properties of paraffin

Frequently asked questions

Q1. What have the authors contributed in "Temperature reduction due to the application of phase change materials" ?

A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. 

Q2. What was the first research conducted in the 1980s?

During the 1980s, the first research was conducted where phase change materials, especially paraffin, were integrated into building materials to solve the problems of thermal protection insummer [3]. 

Q3. What is the heat capacity of the PCM modified gypsum plaster?

Beyond the phase change the heat capacity of the PCM‐ modified gypsum plaster reaches an amount of csensible = 1.15 kJ/kgK, which is equal to the heat capacity of pure gypsum plaster. 

Q4. What is the effect of phase change materials in buildings?

The utilization of phase change materials (PCM) in buildings increases the thermal mass and contributes consequently to an improvement of the thermal protection in summer. 

Q5. What is the effect of the PCM on the temperature of the room?

In the following night the PCM‐conditioned room merely cools down until the solidification temperature of the phase change materials (28 °C), which therefore can be discharged only insufficiently. 

Q6. What is the melting point of the modified CaCl26H2O?

The melting point of the modified CaCl2∙6H2O lies between 25.5 and 27.0 °C, which means it is suitable for the practical use in buildings. 

Q7. How does the temperature curve of the PCM stay convergent?

Until the room temperature attains 25 °C, the beginning of the melting process of the PCM, the temperature curves of both rooms stay convergent. 

Q8. What is the effect of the PCM layer on the temperature curves of the room?

In case of insufficient nocturnal solidification of the PCM as a result of high indoor temperatures, e.g. due to high solar radiation during the day, the functionality of the PCM can be limited. 

Q9. Why is there no supercooling effect in the phase change process?

There is no significant supercooling effect because the solidification process starts nearly at the same temperature as melting process stops [14]. 

Q10. What was the temperature of the salt?

8. Using thermocouples (NiCr–Ni) that were placed on different locations, readings were made in order to get interior and ambient temperatures, the surface temperature and finally the temperature of the salt. 

Q11. What is the effect of the nocturnal ventilation on the temperature of the PCM?

in case of expected high solar radiation resulting in high indoor temperatures it is necessary to adjust the melting point of the PCM to the estimated daily/ nocturnal indoor temperatures [14]. 

Q12. What are the main factors that determine the room temperature?

It is worth mentioning that the room temperature is mainly determined by the impact of the ambient temperature, the solar radiation , internal heat gains and the air change rate n . 

Q13. What is the effect of the PCM on the thermal protection of buildings?

Furthermore,it could be proven that the PCM forfeit their characteristic heat storage capacity after a few consecutive hot days, if they cannot be discharged over night. 

Q14. How can the heat conductivity of phase change materials be determined?

ΔThe heat conductivity of the phase change materialscan only be measured indirectly through the experimental determination of the thermal diffusivity. 

Q15. How can the authors fit the series of measurements with polynomials?

With the help of the least squares method it is consequently possible to fit the series of measurements piecewise with polynomials. 

Q16. What is the idea of improving the thermal buffer?

The idea of improving the thermal buffer through theapplication of phase change materials has been common knowledge for many years.