Determining the Heat of Fusion and Specific Heat of Microencapsulated Phase Change Material Slurry by Thermal Delay Method

This paper details an experimental study that was performed to investigate the specific heat of microencapsulated phase change material (mPCM) slurry and its heat of fusion at the PCM phase change transition temperature. Six samples (mPCM slurry concentrate with the water solution of propylene glycol used as a main base liquid) were prepared. As the concentrate contains 43.0% mPCM, the actual mass fraction amounts to 8.6, 12.9, 17.2, 21.5, 25.8, and 30.1 wt%, respectively. The thermal delay method was used. Samples were cooled from 50 °C to 10 °C. A higher concentration of microcapsules caused a proportional increase in the specific heat of slurry at the main peak melting temperature. The maximum value of the specific heat changed from 9.2 to 33.7 kJ/kg for 8.6 wt%, and 30.1 wt%, respectively. The specific heat of the mPCM slurry is a constant quantity and depends on the concentration of the microcapsules. The specific heat of the slurry (PCM inside microcapsules in a liquid form) decreased from 4.0 to 3.8 kJ/(kgK) for 8.6 wt%, and 30.1 wt% of mPCM, respectively. The specific heat of the slurry (PCM inside microcapsules in a liquid form) was higher than when the PCM in the microcapsules is in the form of a solid and increased from 4.5 to 5.2 kJ/(kgK) for 8.6 wt% and 30.1 wt% of mPCM, respectively.

Study of Huichol Vernacular Housing through Thermal Analysis of the Construction Elements Characteristic of the Pre-hispanic Era

Aims: Analyze the thermal quality provided by the building elements of Huichol vernacular housing concerning the climatic conditions of San Andrés Cohamiata, Jalisco. Study Design: The analysis was performed through a simulation of computer housing, for which the characteristics of the materials and EPW (Energy Plus Weather) data of 2018 from the study area were applied to the model, analyzed in programs such as 2D Sun-Path, 3D Sun-Path and Opaque. Place and Duration of Study: Universidad Autónoma de Querétaro, Graduate of Architecture, Faculty of Engineering, between January and March 2019. Methodology: First, a bibliographic and field study was carried out to verify the materials and construction processes of Huichol housing. The computer housing model was designed to apply the characteristics of the materials, as well as the location and orientation handled by the Huichol ethnic group. Subsequently, EPW (Energy Plus Weather) data from the study area were introduced to opaque software to perform thermal analysis of the house and various factors are studied such as thermal mass and insulation, heat gain/loss, direct radiation, diffuse, dry bulb temperature, among others. Also, in software such as 2D Sun-Path and 3D Sun-Path, the study of sunbathing and shadows of the house was carried out. Results: The orientation of the house allows them to make better use of solar radiation at different times of the year. Its construction elements (wall thickness, material, and ceiling structure) decrease the overheating of the space in summer. Adobe walls have a thermal delay of 4 hours, and internal conditions are optimal to maintain thermal comfort in summer and winter. Internal temperatures during the year range from 20 to 25°C. Conclusions: Huichol culture has important knowledge in the construction with natural materials, as these allow positive thermal behaviour in the face of the climatic conditions of the area throughout the year. These housing characteristics may apply to other ethnic groups in the region with limited economic resources, to improve their living conditions.

Analysis of Ablation Volume Produced During Microwave Ablation of Breast Cancerous Lesion Using Fourier and Non-Fourier Models

The present article aims to compare the change in the temperature and ablation volume during Microwave ablation procedure. The microwave ablation process is carried out using Fourier and non-Fourier bioheat transfer models in the computational domain of breast tumor. The above models have been considered with the relaxation time known as thermal delay during ablation procedure at constant power and frequency. The above objective has been carried out on a heterogeneous three compartment Breast model using COMSOL-Multiphysics software, with inbuilt bioheat transfer and electromagnetic waves Physics interfaces. The simulation results show that the ablation volume is slightly greater while using Fourier bioheat transfer model as compared to the non-Fourier bioheat transfer model. Further, the temperature distribution also shows that there is a slight variation initially at the start of the ablation, i.e., Fourier heat transfer model shows nearly 2°C more temperature as compared to the non Fourier model and becomes equal as the time increases. The present study helps in establishing the better clinical procedure of Microwave Ablation technique.

Thermal delay of drop coalescence

We present the results of a combined experimental and theoretical study of drop coalescence in the presence of an initial temperature difference $\unicode[STIX]{x0394}T_{0}$ between a drop and a bath of the same liquid. We characterize experimentally the dependence of the residence time before coalescence on $\unicode[STIX]{x0394}T_{0}$ for silicone oils with different viscosities. Delayed coalescence arises above a critical temperature difference $\unicode[STIX]{x0394}T_{c}$ that depends on the fluid viscosity: for $\unicode[STIX]{x0394}T_{0}>\unicode[STIX]{x0394}T_{c}$, the delay time increases as $\unicode[STIX]{x0394}T_{0}^{2/3}$ for all liquids examined. This observed dependence is rationalized theoretically through consideration of the thermocapillary flows generated within the drop, the bath and the intervening air layer.

Reducing Heat Conduction of Autoclaved Aerated Concrete Wall Using Phase Change Material

In this work, the effect of the salt hydrated phase change material (PCM) on microstructure and heat conduction of the autoclaved aerated concrete (AAC) was studied. The microstructure in the AAC and AAC with composed phase change material was imaged by scanning electron microscopy (SEM). The ability in heat conduction was compared among AAC (AAC1), AAC with composed phase change material (0.417 (AAC2) and 0.833 (AAC3) kg/m2 in contents), and AAC which was composed by PCM (0.417 (AAC4) and 0.833 (AAC5) kg/m2 in contents) and was coated by the cement in 2 sides. These ones were tested the thermal delay at 40, 50 and 60 °C using the heater that was the thermal source. It was found that the optimum content of PCM on top surface was found at 0.417 kg/m2 because the minimum heat conduction and the lowest average temperatures of inside wall and inside room were shown in this sample at 40, 50 and 60 °C.

Enhanced Heat Conduction in Cellulose Nanocrystals Grafting Polyethylene Glycol as Solid-Solid Phase Change Materials

Green copolymers as phase change material were prepared by grafting polyethylene glycol(PEG) onto a rigid molecular skeleton of cellulose nanocrystals (CNs), and their thermal properties were studied by thermal delay method and differential scanning calorimetry. The influences of the CNs on the thermal conductivity behavior and thermal energy storage capacity of the copolymers were evaluated. As expected, a great enhancement on thermal conduction can be achieved by introducing CNs.