Sodium acetate–urea composite phase change material used in building envelopes for thermal insulation

Abstract

Integrating phase change material with building envelopes is an effective way to reduce cooling or heating loads, improve indoor thermal comfort and save building energy consumption. In this paper, the composite phase change material of sodium acetate and urea is prepared and its thermal-physical properties with different mixing mass ratios are investigated through experiment and T-history method. Moreover, the heat transfer model of building envelopes with phase change material is established and different phase change material locations in external walls for thermal insulation are compared based on integrated uncomfortable degree. The results show that (1) with rising urea mass fraction, both phase change temperature and latent fusion heat (enthalpy) decline; (2) strontium sulfate is an effective nucleating additive to decrease super-cooling degree for such phase change material solidification and (3) to improve indoor thermal comfort, it is preferable to put phase change material in the middle of external walls. Furthermore, the illustrative example of an office building in Chengdu indicates that phase change material insulation can lead to time lag and decrement for indoor air temperature variations. It also indicates that after inserting such phase change material into building external wall, the highest indoor temperature can be decreased by 7 C, leading to 60% cooling energy saving in one typical summer day. This work can provide guidance for building thermal design with phase change materials. Practical application: The studied sodium acetate-urea composite phase change material has been used as energy storage and thermal insulation materials inserted in envelopes for the demonstration project of low/zero energy consumption passive buildings in China.

A Novel Molecular PCM Wall with Inorganic Composite: Dynamic Thermal Analysis and Optimization in Charge–Discharge Cycles

“…Kitagawa et al [15] pointed out that among the available phase transition materials or composites, solid-liquid PCMs, such as paraffin, salt hydrates, fatty acids, and ester,s are applicable in building applications due to their relatively minimal volume variation during the phase change process, along with their desirable melting and freezing features. Gonzalez et al [16] and Zhang et al [17] further stated that With rapid industrialization and technological development, the applications of various PCMs have drawn increasing attention in recent years, especially in the architecture and construction sectors [14]. Kitagawa et al [15] pointed out that among the available phase transition materials or composites, solid-liquid PCMs, such as paraffin, salt hydrates, fatty acids, and ester's are applicable in building applications due to their relatively minimal volume variation during the phase change process, along with their desirable melting and freezing features.…”

“…Kitagawa et al [15] pointed out that among the available phase transition materials or composites, solid-liquid PCMs, such as paraffin, salt hydrates, fatty acids, and ester's are applicable in building applications due to their relatively minimal volume variation during the phase change process, along with their desirable melting and freezing features. Gonzalez et al [16] and Zhang et al [17] further stated that phase change temperature and latent transition heat are the two main considerations in engineering fields, considerably impacting the energy storage capacity and thermal application performance during charge and discharge processes. Some organic and inorganic PCMs considered in the existing literature are listed in Table 1 [13,14,17].…”

“…Gonzalez et al [16] and Zhang et al [17] further stated that phase change temperature and latent transition heat are the two main considerations in engineering fields, considerably impacting the energy storage capacity and thermal application performance during charge and discharge processes. Some organic and inorganic PCMs considered in the existing literature are listed in Table 1 [13,14,17]. [13,14,17].…”

Review on phase change materials and application in building energy saving

“…Such PCMs must be well integrated with the building materials, and the PCMs applicable to the building envelope are shown in New organic composites in building PCMs draw attention currently. Zhang [9] prepared a composite PCM of sodium acetate and area and compared the positions of different PCMs in the external wall insulation based on the integrated discomfort level. The results show that to improve the thermal comfort of the interior, the PCM is preferably placed in the middle of the outer wall.…”

Heat transfer investigation on the thermal energy storage using phase change material in low-carbon building

“…3 It is an effective and energy-saving method to integrate phase change material (PCM) with building envelopes to improve the energy consumption situation. 4…”