Phase Change Material Location Research Articles

Experimental study on the thermal protection enhancement of novel phase change material integrated structural firefighting gloves under high-heat exposures

Phase change material (PCM) has been widely studied for efficient thermal management. This work is the first holistic experimental research on the temperature control performance of PCM-integrated firefighters' gloves. The results showed that the thermal protection time could be extended by 2-5 times in the direct contact to hot object tests and around 1.5 times under the radiant/convective heat source tests when embedding a 1-mm-thick PCM layer in gloves. The PCM of melting point 68 °C showed the best thermal protection performance in all test conditions since it had the most efficient phase change function during the heating process. Considering the PCM location effect, the PCM with lower melting point (68 °C) showed better performance when located close to external environment (heat source) and the PCM with higher melting point (108 °C and 151 °C) showed better performance when located close to hand. The optimum PCM thickness would be in the range of 0.5-1.0 mm for both thermal protection improvement and hand dexterity purposes. In addition, the time for continuous temperature rises on the hand surface at post-heat exposure was longer when embedding PCM in firefighters’ gloves due to the stored latent heat in PCM.

How to choose a model to address practical issues encountered during food transport in an insulated box equipped with phase change material

This article discusses the capabilities and the limitations of three validated models: lumped, zonal and Computational Fluid Dynamics (CFD), to solve several technical issues related to food transport in an insulated box with a Phase Change Material (PCM). The lumped model predicts the average temperature evolution and is suitable for investigating the effect of box design and operating conditions where the temperature heterogeneity is not the main concern. The zonal model depicts spatial temperature variations but requires some assumptions regarding airflow and heat transfer which are specific for a given product arrangement and PCM location. The CFD model gives the most extensive information on physical phenomena and temperature variations but involves a high computational cost that is inevitable. This study shows the possibility of combining these models with a quality model. Finally, the abilities/limitations of each model to solve certain practical issues are discussed.

Effect of phase change material (PCM) on thermal inertia of walls in lightweight buildings

The effect of a layer of phase change material on an increase in the thermal inertia properties of the outer wall in lightweight building has been numerically studied. Changes in thermal characteristics of the wall in the summer period at various locations of the PCM were analyzed. The regime of indoor air conditioning and the regime of daily in-phase change in the indoor and outdoor air temperatures are considered. It is shown that in the regime of indoor air conditioning, the use of a layer of 4-vol.% paraffin in a wall made of foamed polyurethane allowed reduction in the amplitude of heat flux fluctuations on the inner wall surface from 2 to 13 times, depending on PCM location. The greatest heat flux reduction was obtained when a PCM was mounted in the central area of the wall. It was calculated that the greatest effect of increasing the thermal inertia of the wall made of a light heat-insulating material in the regime of daily in-phase fluctuations in the indoor and outdoor air temperatures was observed when a PCM was located on the inner surface of the wall.

Hygrothermal and energy performance assessment of a passive building wall integrating PCM and bio-based hygroscopic material

Phase change material (PCM) and hygroscopic material (HM) in building walls are promising passive technologies for temperature and humidity regulation, respectively. Integrating the two materials allows for hygrothermal environment regulation and energy savings. However, the joint effect of the temperature dependence of the HM's hygroscopic properties and the location dependence of the PCM's thermal properties has not been mentioned or demonstrated. This study experimentally assessed the hygrothermal and energy performance of a shell enclosed by a PCM-HM wall. Different wall scenarios were proposed to study the effect of the HM, PCM, and PCM's location. The results highlighted the dominance of temperature and the significance of the PCM on performance. For PCM walls, the thermal and hygric inertia were enhanced, the characteristic times of temperature/relative humidity were increased, and the variation was dampened. Under a sinusoidally varying climate, the peak temperature, thermal load, and fluctuations in temperature, relative humidity, and vapor pressure were reduced, and the peak temperature was delayed. Additionally, the repositioning of the PCM further improved the performance. When the PCM was repositioned from the outside to the middle, the temperature, relative humidity, vapor pressure fluctuations, and thermal load were reduced by 25.0 %, 45.8 %, 54.6 %, and 33.1 %, respectively, in warm to hot climates, and by 12.5 %, 63.6 %, 41.9 %, and 66.0 %, respectively, in cold to temperate climates. The PCM properties are important as the PCM in the PCM-middle wall has a higher melt fraction in the solid–liquid state, which utilizes more PCM latent heat energy and improves wall performance.

Study on the heat transfer of a concrete wall outfitted with phase change materials

This paper tested and simulated the thermal performance of a concrete wall outfitted with Phase change materials (PCMs) under 5 climate conditions in China. The PCMs were encapsulated in high-density polyethylene spherical shells in the concrete to form a PCMs-concrete layer. The daily thermal load change rate through the wall when the PCMs-concrete layer was placed in different positions in five typical climate regions in China were studied. The results show that to make the best use of the PCMs in summer, the phase transition temperature is suggested to be between the outer and inner surface temperatures. For the cases when the outer and inner surface temperatures are higher than the phase transition temperature, the PCMs should be installed in the middle of the wall; To make the best use of the PCMs in winter, the location of PCM should be adjusted according to the range of ambient temperature, when the ambient air is warm enough, the PCMs layer should be installed near to the inner surface, when the ambient air is tepid, the PCMs layer should be installed near to the outer surface, when the ambient air is cold, results do not suggest using PCMs.

Potential evaluation of energy flexibility and energy-saving of PCM-integrated office building walls

Building energy flexibility is important for reducing peak-to-valley differences in air-conditioner loads. Integrating phase change material into office building envelopes and precooling can effectively reduce peak load, but precooling may increase total energy consumption. Therefore, it is imperative to investigate its energy flexibility and energy consumption features. In present work, a heat transfer model of phase change material (PCM)-integrated office building walls was established firstly and verified by experiments. Then, the energy flexibility and energy-saving potential of the PCM-integrated wall under different precooling strategies were studied, and the effects of various PCM parameters on energy flexibility and energy-saving potential were evaluated. Finally, the influence of different peak-to-valley electricity tariff differences on electricity costs was analyzed. The results show that the optimized precooling strategy and peak-to-valley electricity tariff difference make the energy flexibility index of the PCM-integrated wall up to 69.7% at a total load reduction of 1.3% and save the electricity cost by 51%. The PCM location and melting point have the most significant effect on the energy flexibility and energy-saving potential of the PCM-integrated wall under precooling operating conditions. This study guides the selection of energy flexibility and energy-saving precooling strategy and PCM parameters for PCM-integrated office building walls and the formulation of time-of-use tariff policies.

Numerical analysis for thermal management of data center with phase change material

PurposeThe purpose of this paper is to analyze the performance of a data center and thermal management by using phase change material (PCM). Numerical studies were conducted for two dimensional model of data center and installation of PCM at different locations.Design/methodology/approachFinite volume method was used for the unsteady problem, while impacts of air velocity and PCM location on the flow field, thermal pattern variations and phase change dynamics were evaluated. Three different locations of the PCM were considered while air velocity was also varied during the simulation. Thermal field variations and cooling performance of the system for different PCM location scenarios were compared.FindingsIt was observed that the installation of the PCM has significant impacts on the vortex formation, thermal field variation within the system and its performance. The left, right and top wall installation of the PCM changed the thermal patterns near the heat cell of the data centre. The phase change process is fast for the upper wall installation of the PCM, while the discrepancy of the melt fraction dynamics between different air flow at this position is minimum. The case where PCM placed in the upper wall at the highest air velocity is the best configuration in terms of heat storage. The utilization of PCM and changing its locations provide an excellent tool for thermal management and cooling performance of data centre.Originality/valueResults of this study can be used for initial design and optimization of cooling systems for thermal management of data centers while the importance of the high-performance computing becomes very crucial for the advanced simulations in different technological applications.

A review of novel methods and current developments of phase change materials in the building walls for cooling applications

The prime concern of the scientific community nowadays is high energy consumption and related greenhouse gas (GHG) emission. One of the major energy consumers is building sector, where nearly 30% of total energy is disbursed, with high priority to space cooling and ventilation. In addition, the contribution of buildings for GHG emission is also high. Various researchers in the recent past have suggested and successfully implemented different cooling methods to address this crisis. This paper evaluates various models suggested by researchers for building cooling with phase change materials (PCMs). Since the exposed area of high-rise buildings is more, there is a great chance for energy savings. The PCM impregnated building wall and building brick models have the promising potential for energy saving, by providing thermal comfort and conceding the peak temperature. This article emphasises the wall and building brick applications of PCM for building cooling, that illuminate the associated difficulties and possible alternatives. From the study, it was found that the PCM walls can be constructed with different techniques like adding PCM as a separate layer or inserting PCM in brick holes. In some cases, the PCM is added as a constituent in the cement mortar for plastering or for making concrete. These techniques will help to reduce the building cooling load, peak heat flux, and shift the peak temperature to off working hours. In cooling applications, it is preferred to keep the PCM layer near the heat source for better performance. The performance of a PCM wall highly depends upon the type of PCM used, location of PCM in the wall, type of application, and on the phase transition temperature of PCM.

Numerical study of phase change material microencapsulated in a typical multilayer wall for a hot climatic zone

AbstractA phase change material (PCM) allows releasing and absorbing energy at the phase change transition. They are employed in building walls to maintain internal thermal comfort and optimize thermal energy storage. However, the hottest cities in Morocco suffer from overheating during peak days. Consequently in this article, the purpose is to evaluate the thermal performance of incorporation of the PCM n‐octadecane paraffin in a typical multilayer wall at three different locations for a Moroccan hot climate zone. Numerical simulation is developed in a two‐dimensional transient in addition to mathematical modeling using the enthalpy‐porosity approach for three wall types. An implicit finite volume method is used for the numerical solution. The effects of PCM location, PCM type, and mass fraction (varying between 15% and 35%) are studied and compared with the reference case (without PCM). The evaluation of mass fraction variation is based on two determining factors of the wall panel's thermal inertia: the time delay and amplitude attenuation. The surface heat fluxes will then be used to quantify the capacity of the multilayer wall to store and release energy. The results showed that to ensure the thermal performance of the wall, it is useless to exceed 20% of mass fraction for all types of multilayer walls. It is shown that the incorporation in a solid matrix of hollow brick is the most optimal scenario, and it makes it possible to have a reduction in the internal surface flux of 32% with a temporal phase shift of 3 h.

Parametric and sensitivity analysis of a PCM-integrated wall for optimal thermal load modulation in lightweight buildings

Load modulation in buildings is becoming increasingly important due to growing disparity in energy demand during peak and off-peak hours. Integrating phase change material (PCM) in building envelopes and using a controlled precooling strategy can provide substantial thermal load modulation; however, it may greatly increase the total energy use. Previous studies have employed PCM in building envelopes primarily for energy savings and, to some extent, peak load shedding and shifting. However, the load modulation capacity of a PCM-integrated envelope has not been well explored in the literature. In this study, we perform an extensive parametric and sensitivity analysis on PCM-integrated lightweight building walls and examine the combinatory effects of various PCM parameters on thermal load modulation and wall-related heat gains in buildings. Using numerical simulations, we investigate eight PCM parameters: PCM location in the wall, transition temperature, thickness, latent heat, transition range, density, specific heat, and thermal conductivity. We evaluate their impact and relative importance to achieve maximum load modulation in buildings without compromising occupants’ thermal comfort or total energy use. The results show that the optimized PCM proposed in this study can completely invert the transient heat gain profile of the wall, providing up to 70% reduction of wall-related heat gain during peak hours without a major increase in the cumulative heat gain.

Dynamic performance of a novel air-soil heat exchanger coupling with diversified energy storage components—modelling development, experimental verification, parametrical design and robust operation

A novel vertical air-soil heat exchanger (VASHE) is proposed, coupling with diversified energy storage components, i.e., both annular and tubular phase change material (PCM) components. Compared to traditional air-soil heat exchanger systems, advantages of the new VASHE include the space-saving, higher energy efficiency, centralized discharge of condensate water and smaller fluctuation of outlet air temperature. An enthalpy-based model is developed to characterise the underlying heat transfer mechanism of the sophisticated sensible and latent heat transfer in PCMs. An experimental platform is thereafter constructed for the calibration of the developed enthalpy-based numerical model. Systematic parametrical analysis has been conducted on PCM types, PCM structure and PCM locations. Research results indicated that, the developed enthalpy-based model was accurate to predict the system performance with the maximum relative error at 1.98%. Systematic parametric analysis indicates that, within various PCM types, the RT 20 in the tubular PCM is the most promising with the smallest outlet temperature amplitude. Furthermore, accurate PCM location is an effective solution to the contradiction between daily cooling storage capacity and outlet temperature amplitude. This study demonstrates a novel air-soil heat exchanger with diversified energy storage components, which can provide concrete guidance and pave path for the geothermal energy utilisation.

Numerical simulation of building wall incorporating phase change material for cooling load reduction

Phase change material (PCM) placed in the building wall changes the temperature profile within the wall and thus influences the heat transport to indoor environment. The effectiveness of these building walls depends on PCM location within the wall, PCM melting temperature, and PCM layer thickness. Considering these parameters, the numerical simulation has been conducted for a typical building wall and the obtained results are reported in terms of melt fraction of PCM and heat flux at the inner surface of the wall. From these results it is found that for the minimum heat transport to the indoor environment, the PCM layer should be embedded in between the fiberglass insulation layers, melting temperature of PCM should be in the range of indoor air temperature and PCM thickness should be higher. The numerical simulation has also been conducted considering actual weather conditions into account for three consecutive days with four different PCM (RT-26, RT-25, n-octadecane and RT-28). For three consecutive days, the percentage reduction of heat transport to the indoor environment is obtained 33.18%, 33.94%, 34.40% and 37.13% by using RT-26, RT-25, n-octadecane and RT-28 PCM, respectively.

Computer Simulation of Passive Cooling of Wooden House Covered by Phase Change Material

The paper is devoted to computer simulations of the distribution and time evolution of the temperature in a wooden house in summer. The goal of simulations was to assess the effect of covering walls inside the house with a PCM (phase change material) on its passive cooling, which prevents the undesired overheating of the house and provides the required thermal comfort for the occupants under warm summer days. Computer simulations were performed by the COMSOL Multiphysics software (COMSOL Inc., Stockholm, Sweden). A model of a house without the PCM coverage was compared with models of houses in which the PCM was located on all walls, except a floor, and on a wall opposite the window. Results of simulations proved that the wood wall thickness and PCMs location influence overheating the wooden house. Under studied conditions, the coverage of a wall opposite the window best eliminated extremes of the air temperature inside the house. The maximum temperature decrease was 3.9 °C (i.e., drop of 31.1%) comparing the house which wall opposite the window was covered by the PCM and the house without the PCM coverage.

Experimental investigation of PCM location in a commercial display cabinet cooled by a transcritical CO2 system

Abstract In this study, the influence of phase change material (PCM) location in a closed display cabinet cooled by a transcritical CO2 refrigeration system was examined experimentally. Two configurations have been investigated where PCM panels are placed on the backside and the shelves of the cabinet. The effect of PCM locations on the cabinet air temperature and compressor power consumption is evaluated and compared during periods of 24 and 8 h of operation. The variation of in the cabinet air temperatures and power consumption with time is measured during charging, running, and power failure periods. It is found that installing PCMs on the shelves of the cabinet is more advantageous and promising in terms of both maintaining cabinet air temperature homogeneous and keeping it at certain average temperature levels. For PCM on the shelves case, energy saving is found 4.4% less than without PCM case. On the other hand, PCM on the backside case results in 8% more energy consumption. Moreover, the running time is found 15.8 less for PCM on the shelves case. Therefore, PCM on shelves case is concluded to be the best option for PCM utilization in the present study.

An experimental study of the efficacy of integrating a phase change material into a clay-straw wall in the Drâa-Tafilalet Region (Errachidia Province), Morocco

The objective of this new study is to integrate a Phase Change Material (PCM) into a clay-straw wall in order to reduce the energy consumption of buildings in Morocco's Drâa-Tafilalet Region. The underlying notion is to fully utilize the storage capacity in the walls built with clay and straw. Furthermore, to raise the thermal energy stored in the building envelope, a PCM was integrated into the walls. In this experiment, a reduced-scale cavity with replaceable sidewalls was used to study the thermal transfer taking place in walls. The effect of PCM location was also investigated by considering the reduction in both wall surface temperature and surface heat flux. Both the inner and outer wall layer temperatures were measured, while the heat flux through the walls and the heat stored in the walls were estimated. Results show that by integrating PCM into the clay-straw wall, the surface temperature can be reduced by up to 3 °C. In addition, the location of the PCM adjacent to the heat source considerably lowers the surface temperature, by a value of 1 °C compared to when PCM is placed on the outer wall layer. The peak heat flux of the PCM-integrated wall drops by 31.95% compared to the clay-straw wall without PCM. However, for the clay-straw wall with PCM on the outer layer, the peak heat flux is reduced by 26.5%. Moreover, the PCM-integrated wall stores 14.17 W/m2 on average of the inlet heat flux. On the other hand, the clay-straw wall with PCM on the outer layer and the wall with PCM embedded in the middle are both able to reduce the peak heat flux by 30.41%.

PCM integrated to external building walls: An optimization study on maximum activation of latent heat

Integration of the phase change materials (PCM) into the external building walls is an efficient method for reduction of energy consumption and regulation of energy demands due to increasing thermal inertia of the walls. This study aims to reveal the contribution of latent heat to the thermal performance of the wall and to determine the location, thickness and melting temperature of PCM for the maximum exploitation of latent heat for different climatic conditions. A comparative study is carried out for the wall coupled with PCM and the wall with Phase Stabilized PCM (PSM) to reveal the improvement provided by the latent heat. The influence of location, fusion temperature and layer thickness of PCM on energy saving, decrement factor and time lag was examined. The annually optimized PCM fusion temperature and layer thickness which utilizes the latent heat at maximum level considering both heating and cooling loads are determined for three cities of Turkey. The computed results show that the monthly optimized PCM melting temperature and PCM layer thickness vary from 6 to 34 °C, from 1 to 20 mm depending on climatic conditions. It was concluded that an optimization study should be conducted in order to prevent PCM behaves like PSM.

Multi-objective optimization of energy performance of a building considering different configurations and types of PCM

Phase change materials (PCM) can be outfitted in building envelopes to not only provide thermal comfort for occupants but also trim heating, ventilation and air conditioning (HVAC) loads. However, the efficacy of PCMs depends highly on its thermo-physical properties and climatic condition. In this regard, a multi-objective optimization technique is adopted to unearth the optimal type and location of PCM that can minimize heating and cooling loads considering five cities of Iran namely Tehran, Tabriz, Bandar Abas, Shiraz and Yazd with distinctive climates. Then, the optimal PCMs are environmentally and economically assessed. The study showed that the PCM with a melting temperature of 25 °C outperforms in terms of cooling load while the PCM with a melting temperature of 21 °C favors the heating performance. Moreover, the utilization of PCM results in electricity saving of 4.5–5.5% for all the climates. On average, the annual carbon footprint is reduced by 1297 kg, 1420 kg, 2040 kg, 1027 kg, and 1248 kg for Tehran, Tabriz, Bandar Abas, Shiraz, and Yazd, respectively. The payback period was found to be more than 70 years for all the cities considering current economic conditions. However, the energy subsidies are projected to fall in the near future that may make PCM integration economically feasible.

Thermal performance evaluation of a new structure hot water tank integrated with phase change materials

The energy consumption of domestic hot water accounts for 10-20% of building energy consumption. Such high energy consumption heightened the need for utilizing energy-efficient technologies in domestic hot water systems. Among existing technology, integrating phase change materials (PCM) into domestic hot water tanks is very attractive due to the fact that adding PCM in tanks would enhance the storage density of the system. Most of these studies encapsulated PCM and then put it on the top of the tank. These studies highlighted the positive aspects of the integration of PCM. However, they suffer from the fact that the capacity of hot water in tanks will be reduced. To address this issue, in this study a new structure hot water tank was proposed with PCM placed on the side of the tank. In order to evaluate the thermal performance of this new tank, experiments were performed based on a cylindrical hot water tank of 150 L capacity. Results show that the integration of PCM can significantly improve the thermal performance of the hot water tank. Compared to a tank without PCM, the time length for water temperature drop from 65 to 40 ºC at the top of the tank with PCM is over 8.5% longer. Moreover, the change of the amount and the location of PCM results in different water stratification in the tank.

The effect of phase change material incorporated building wall on the CO<SUB align="right">2 mitigation: a case study of Izmir, Turkey

Buildings are considered to be one of the considerable energy consuming systems and greenhouse gas emissions sources, and 14% of this energy is used for cooling. This paper evaluates the energetic benefits and CO2 emissions of incorporating phase change materials (PCMs) on the facade of an office building under real weather data conditions for Izmir, Turkey for cooling. For this purpose, two situations, specifically the effect of the melting temperature (27°C, 32°C and 37°C) and the location of PCM (interior, middle and exterior of the wall) have been investigated for five months, from May to September. The results indicate that integration of PCM with a melting temperature of 32°C at the interior section of the wall in the hottest months of the year, namely June, July, and August reduce the related CO2 emissions by 50.15, 122.339 and 121.727 kg CO2 respectively, compared to the baseline configuration without PCM.

The effect of phase change material incorporated building wall on the CO<SUB align="right">2 mitigation: a case study of Izmir, Turkey

Buildings are considered to be one of the considerable energy consuming systems and greenhouse gas emissions sources, and 14% of this energy is used for cooling. This paper evaluates the energetic benefits and CO2 emissions of incorporating phase change materials (PCMs) on the facade of an office building under real weather data conditions for Izmir, Turkey for cooling. For this purpose, two situations, specifically the effect of the melting temperature (27°C, 32°C and 37°C) and the location of PCM (interior, middle and exterior of the wall) have been investigated for five months, from May to September. The results indicate that integration of PCM with a melting temperature of 32°C at the interior section of the wall in the hottest months of the year, namely June, July, and August reduce the related CO2 emissions by 50.15, 122.339 and 121.727 kg CO2 respectively, compared to the baseline configuration without PCM.