PCM Layer Thickness Research Articles

Performance augmentation and machine learning-based modeling of wavy corrugated solar air collector embedded with thermal energy storage: Support vector machine combined with Monte Carlo simulation

At present, artificial intelligence methods have been effectively utilized for predicting the complex performance of storage-based solar thermal technologies for cooling/heating applications. It is crucial to have accurate energy storage-based sustainable system estimation, which would contribute to increased operational time, thus maximizing the overall efficiency of solar energy-based storage systems. Hence, this work introduces a comparative experimental investigation and support vector machine (SVM) modeling on a wavy corrugated solar air collector (WCSAC) with and without using a paraffin wax storage container. Experiments on the WCSAC were performed under three air flow rates of 0.540, 1.68, and 3.72 kg/min and two paraffin layer thicknesses of 2 cm and 4 cm, respectively. Moreover, improved SVM models implemented in MATLAB software are developed for predicting the thermal performance parameters; including air temperature ratio, average air temperature, convective heat transfer coefficient, and energy efficiency for the WCSAC. The optimal solution of the SVM modeling is developed by incorporating the Karush-Kuhn-Tucker conditions and several kernel functions. In addition, a sensitivity analysis is also conducted to explore the significance of model input parameters (air inlet temperature, time, solar irradiance, air flowrate, PCM layer thickness) on the output parameters prediction using the Monte Carlo simulation technique. The experimental results presented that the daily energy efficiencies of the WCSAC equipped with 4 cm paraffin layer thickness are 24.0 %, 20.39 %, and 16.37 % higher than that of the WCSAC without PCM at airflow rates of 3.72, 1.68, and 0.54 kg/min, respectively. Moreover, the connective heat transfer coefficient of the WCSAC with PCM is more than 1.20 times that yielded with the WCSAC without PCM. Additionally, the SVM simulations showed that the optimal solution of the SVM model is developed by incorporating the Karush-Kuhn-Tucker conditions and Lagrangian function kernel function, which revealed a superior accuracy with the highest coefficient of determination of 0.990 and 0.950 for training and test processes, respectively.

Modelling analysis and performance evaluation of a novel hybrid CdTe-PCM PV glass module for building envelope application

In this work, a novel hybrid CdTe-PCM PV glass module (CdTe-PCMG) was proposed, fabricated and tested. A mathematical optical-electrical-thermal coupled model was established and validated against the experiment data under different ambient conditions. Based on the validated model, a building energy simulation (BES) model integrated with the novel modules as building windows was established. Comparison case study was respectively conducted between the building model with single PV glass module under a continuous hot/cool week. Impacts of several parameters including the PV coverage, ambient conditions, PCM thickness and phase change range on the comprehensive electrical and thermal performance was analyzed. Annual performance in five different climatic cities was predicted to discuss the PCMG's regional application potential. Main conclusions are: (1) The utilization of PCM has improved the electrical output of the PV glass and enhanced the indoor thermal comfort when applied on the building envelope; (2) According to the parameter analysis under the cool week, the optimal PCM layer thickness and phase change range were 3.5 cm and 22 °C ∼ 24 °C; (3) Based on the annual performance predictions, the PCMG was more suitable to be applied in the regions with abundant solar radiation resource or mild climate condition.

Developing a TRNSYS model for radiant cooling floor with a pipe-embedded PCM layer and parametric study on system thermal performance

The design of the radiant cooling floor with a pipe-embedded PCM layer (RCF-PEPCML) lacks a relevant reference basis. Simulation is the best way to determine the optimal design of the system. The simulation research of PCM radiant terminals has been developed, but there is still a need to establish a convenient transient simulation method for RCF-PEPCML, in order to conduct various optimization studies on system design. In order to meet this simulation requirement, a two-dimensional heat transfer model for a pipe-embedded PCM layer (PEPCML) was established. The numerical model was written in FORTRAN language and integrated into TRNSYS to create a new module (TYPE207) for simulating a PEPCML. The accuracy of the new module was verified by experiments conducted in a scaled experiment room with radiant floor cooling. Then, using the newly-built module and TRNSYS, a case study was conducted to explore the effect of several key parameters on the thermal performance of the RCF-PEPCML. The influencing parameters considered include the PCM's phase change temperature, phase change latent heat, and the PCM layer thickness. The results of univariate sensitivity analysis show that these three parameters all greatly affect the thermal performance of RCF-PEPCML. The recommended optimal phase change temperature should meet this condition where the lower limit of the phase change temperature interval is higher than the water supply temperature by 0–1 °C. The optimal phase change latent heat and optimal PCM layer thickness depend on the specific design conditions of the cooling terminal. It is suggested to perform optimization design analysis for specific cases through simulation. The orthogonal test analysis of multiple parameters shows that the optimal design parameters combination for the case study is the combination of a phase change temperature of 20 °C, a phase change latent heat of 160 kJ/kg, and a PCM layer thickness of 15 mm. Among the three influencing factors, the phase change temperature should be given priority.

Computational Investigation on Phase Change Material based Hybrid Battery Thermal Management System for Electric Vehicle

The future of the automobile industry is moving towards the electrification of vehicles due to the increase in pollution and global warming. The thermal management of the battery is necessary to enhance the performance of the battery module at extreme operating conditions. Battery thermal management systems using phase change material can be used to control the temperature extremity and to achieve uniformity in temperature inside battery module. In this work, the conventional battery layout system is modified to induce the passive cooling with the use of PCM (paraffin wax) which has been placed around the periphery of each cell in the battery pack. Different thickness of PCM layer 2mm, 3mm and 4mm have been taken. This reduces the weight and cost compared to the existing PCM based BTMS. This also ensures improvise in the efficiency of the battery. The battery thermal behaviour is studied using ANSYS for various discharge rate condition (4C, 3C, 2C and 1C) with air assisted cooling system having an air flow rate of 4m/s. From the analysis, it is found that maximum temperature of a battery pack at 4C discharge rate without any BTMS is, about 60C. Elevated temperature of the battery pack covered with a PCM, for same discharge rate with same air flow rate for 2mm is 33.5C and for 3mm it is 34.4C and for 4mm it is 34.07C which falls under the optimal temperature. While adding expanded graphite to the PCM it is found that the temperature reduces to 30C for 2mm thickness PCM.

Sensitivity of energy performance to the selection of PCM melting temperature for the building located in Cfb climate zone

In the present study, optimization of PCM layer thickness and melting temperature to increase the energy-saving potential of the office building located in eight cities in the Cfb climate zone was conducted using the Fanger model. The sensitivity of the energy savings to the selection of PCM melting temperature was quantitatively analyzed using a novel indicator of average savings drop. Additionally, the investigation of the effect of real PCMs on the energy performance of the building located in Cfb climate as well as the economic and environmental analyses were accomplished. The results showed that the PCM layer with a thickness of 2 cm reached the highest values of energy savings per unit thickness. The optimization of the PCM melting temperature revealed that PCM 22–25 were optimum for the whole Cfb climate zone and resulted in energy consumption reduction values of up to 37.6%. The sensitivity analysis showed that the steadiness of the outdoor climate conditions affects the sensitivity of the energy savings to the selection of PCM melting temperature. The analysis of real PCMs revealed that PCM 25-r demonstrated more efficient performance in all cities. Overall, it was concluded that the integration of PCM can be considered an economically and environmentally feasible solution.

Investigating the performance of the PCM-integrated building envelope on a seasonal basis

BackgroundThe PCM-integrated building envelope has shown significant potential in energy management and heating/cooling loads reduction. However, PCM layer performance highly depends on environmental conditions, configuration and its thermo-physical properties. The right choice of these characteristic features is great of importance since it may cause inverse effects. MethodsSo, in this comprehensive study, the performance of PCM wallboard under realistic sessional weather and solar radiation by considering different values of melting points (22, 24 and 26 °C) is investigated. To capture the solid/liquid interface and liquid fraction, the precise enthalpy-porous model, as well as the actual heat transfer chain consisting of radiation, convection and conduction from the environment to the room ambient, are implemented. Significant findingsThe results showed that the PCM layer is not always advantageous and more than 5% negative impact on energy loss is observed. So, the performance is highly dependent on other key factors including the environmental conditions and its volumetric amount. Also, the existence of optimum values for PCM layer thickness regarding the costs and wall density is observed for different types of PCM. The effect of the melting point on energy-saving is another significant parameter that has shown a considerable impact on appropriate PCM selection for specific regional conditions.

Phase-change material-integrated thermoelectric radiant panel: Experimental performance analysis and system design

The objective of this research was to experimentally analyze the cooling performance of a phase-change material-integrated thermoelectric radiant cooling panel (PCM–TERCP) under active and passive cooling operation modes. Empirical models were derived for the PCM–TERCP to provide the available cooling capacity, duration time, and electric power consumption of the panel for the melting period (passive cooling mode) and solidifying period (active cooling mode) under a given operating condition. In the experiments, the durations of both the active and passive cooling were extended by up to 4 h when the thickness of the PCM layer increased from 5 mm to 15 mm. The mean cooling capacities of the proposed panel under the active cooling and passive cooling modes were approximately 58 W/m2 and 54 W/m2, respectively, when the mean radiant temperature (MRT) was 26 °C. Both cooling capacities decreased under lower MRT conditions. Empirical correlations for the cooling duration, cooling capacity, and electric power consumption of the proposed panel were used as objective functions to determine the optimum PCM layer thickness. The optimum PCM thickness of the proposed panel was determined to be 6–8 mm when providing a higher weight to minimizing the electric power consumption than to maximizing the cooling capacity.

Thermal stress performance of glazed units contained phase change material

The low heat transfer and high energy storage performance of phase change material (PCM) will improve the thermal performance of the PCM-glazed units. However, decreasing the heat transfer results in uneven thermal load on the surface of the PCM-glazed units, which is an important cause of thermal stress in such units, because the glass in glazed units is a fragile material, and then large thermal stress can result in cracks and possible fallout of the glazed units. To study the thermal stress distribution of PCM-glazed units, a method combined numerical simulation and experimental analysis was conducted. First, the heat transfer performance and thermal stress distribution of PCM-glazed units with PCM thicknesses between 3 and 11 mm were experimentally investigated. Results showed that the thermal performance of a glazed unit was improved by adding PCM, and the variation of thermal strain on its surface with a PCM-layer thickness of 7 mm was the smallest in five test facilities. Then, the thermal stress was numerically investigated regarding the PCM height and the aspect ratio of the PCM-glazed unit. The higher the PCM height, the greater the maximum strain. An aspect ratio of PCM-glazed units of 1.5 was recommended.

Multi-factor analysis on thermal comfort and energy saving potential for PCM-integrated buildings in summer

The multi-factor orthogonal simulation analysis was initiated to investigate the influence degree of four key parameters of PCM-integrated building envelopes on energy consumption and indoor thermal comfort under Chinese climate. The sensitivity and the interaction between four key parameters on energy saving and indoor temperature were discussed. The results showed that: 1) According to the influence degree on energy consumption and indoor thermal comfort time, the four key parameters of PCM envelope can be ranked in descending order as follows: envelope type > PCM layer layout > PCM type > PCM layer thickness. 2) The optimal level of all the cases studied is using BioPCMTM23 (PCM2) with a thickness of 7 cm on the inner side of both wall and roof. 3) Integrating the PCM to the envelope can effectively reduce the indoor temperature fluctuation. Considerable energy saving effects (the energy saving rate is 4.8% – 34.8%) can be achieved by properly selecting the PCMs according to local climatic conditions. The PCMs with high latent heat should be selected and placed in an envelope structure that receives longtime solar radiation and has a large surface area, which can maximize the effect of energy saving and temperature control.

Performance prediction and optimization of a photovoltaic thermal system integrated with phase change material using response surface method

Abstract In this study, a predictive model is developed based on the response surface method (RSM), to show the relationship between the operating factors (independent parameters) and some important response factors (dependent parameters) of a photovoltaic thermal system integrated with phase change material (PVT/PCM). The considered phase change material is the Rubitherm (RT) series of organic phase change materials. Moreover, both single and multi-objective optimization are conducted using RSM for different optimization objectives to recommend the optimal values of control factors for different operating conditions. The selected operating factors include PCM layer thickness, solar radiation, melting temperature of PCM and ambient temperature. Five response factors, including electrical power, thermal power, electrical exergy, thermal exergy and entropy generation are considered. To evaluate the model statistical adequacy, diagnostic analysis is performed for each response to indicate that the predictive model has a reasonable accuracy. The analysis of variance (ANOVA) test and perturbation analysis are also applied to evaluate the suitability and statistical importance of the recommended model and they show that the sensitivity of solar radiation on energy and exergy outputs is higher than that of other operating factors. According to the results, to maximize the electrical power, thermal power, electrical exergy, thermal exergy, and to minimize the entropy generation, simultaneously, it is recommended to select the PCM layer thickness of 1.5 cm, solar radiation of 901 W/m2, melting temperature of 25 °C, and the ambient temperature of 40 °C, based on the proposed method in this study.

Effect of variation in thickness of phase change material on temperature across the composite building wall

In this paper, the impact of thickness of a bio-phase change material (b-PCM) and its effectiveness towards thermal execution and comfort of a building wall is studied using ANSYS. Two models have been simulated among which the primary model is a reference room which do not contains b-PCM and the secondary model is one including b-PCM with varying thickness. A b-PCM can more constructively decrease the heat transfer to the inner side room due to lower thermal conductivity and higher latent heat of phase change. In addition, the thermal conductivity has need over other PCM thermo physical properties. The lower thermal conductivity of PCM allows lower amount of heat to the inside room space. The observations of present work reveal the information that the expansion of PCM layer thickness has significant impact for delivering a higher temperature contrast, past specific timings of the peak surrounding temperature. Likewise, the utilization of PCM empowers better ability to hold starting temperature for longer timeframe.

Parametric analysis and design optimisation of PCM thermal energy storage system for space cooling of buildings

The paper presents a parametric analysis and design optimisation of an active PCM thermal energy storage system for space cooling of nearly zero-energy buildings. The design for a new space cooling system proposes a TES system composed of stand-alone PCM storage units incorporated into the building interior under the ceiling slab. Active control of the thermal energy storage is realized by night cooling of a phase change material by means of cold water flowing within a capillary pipe system. The objective of the study is to examine the effect of the system’s main parameters such as PCM layer thickness, number of parallel pipes, diameter of pipes, night cooling duration, cooling water inlet temperature and velocity under Baltic summer weather conditions. Parametric analysis is performed by using computational fluid dynamics software Ansys Fluent. Optimisation of the main parameters is carried out to determine the best combination of their values ensuring the system is able to absorb the daily thermal loads within the room and operates with minimum energy consumption for the night cooling of PCM.

Model establishment and operation optimization of the casing PCM radiant floor heating system

In this study, a new two-dimensional model of CPRF was developed in TRNSYS. Its accuracy was validated by a full-scale experiment. The effects of key parameters of CPRF coupled with solar water heating system on indoor temperature was analyzed. The single factor analysis revealed that reducing tube pitch and solidification temperature, increasing PCM layer thickness and solar collector area could increase indoor temperature. The orthogonal test analysis indicated that tube pitch has the greatest impact on the average indoor temperature. The CPRF heating system coupled to solar energy and an electric boiler operating on valley electricity (CSSEBV) was proposed to ensure stable heating. It was optimized by GENOPT. The optimal parameters are that the tube pitch is 0.28 m, the PCM layer thickness is 0.02 m, the solar collector area is 12.5 m2 and the operating time of the electric boiler is 2h. The economy, energy saving property and environmental benefits of four systems were also compared and analyzed.

Study on thermal insulation characteristics and optimized design of pipe-embedded ventilation roof with outer-layer shape-stabilized PCM in different climate zones

Roof receives heat directly from the solar radiation and outdoor air, and the heat transfer of the roof is often greater than that of any external wall. The building roof is usually overheated in summer, causing a great increase in the air conditioning load and negative effects on indoor thermal comfort. Thus improving the thermal insulation performance of the roof is essential for reducing air conditioning energy consumption and improving indoor thermal comfort. In this paper, an innovative pipe-embedded ventilation roof with outer-layer shape-stabilized PCM (named VRSP for short) was proposed. The heat gain is stored in the PCM to migrate excessive heat during the day and released through air ventilation at night. A three-dimensional transient-state heat transfer model of the VRSP system was built by CFD. The effects of phase transition temperature range of PCM, thickness of PCM layer and airflow rate in the ventilation duct on the thermal performance of the structure in five representative climate regions of China were evaluated. Results show that the optimum phase transition temperature ranges of PCM in severe cold region, cold region, hot summer and cold winter region, hot summer and warm winter region and mild region are 31–33 °C, 34–36 °C, 36–38 °C, 34–36 °C and 29–31 °C, respectively. The optimum thicknesses of the PCM layer are 25–30 mm, 25–30 mm, 30–35 mm, 25–30 mm and 20–25 mm, respectively. The suitable airflow rates are 1.5–1.9 m/s, 1.6–2.0 m/s, 2.1–2.5 m/s, 1.9–2.3 m/s and 1.4–1.8 m/s, respectively. The conclusion provides valuable guides for the application of VRSP under various climate conditions.

Energy Savings of PCM-Incorporated Building in Hot Dry Climate

Phase change materials is one of the innovative technologies to reduce the heating and cooling demand of buildings. In this research, the thermal performance and energy efficiency of PCM-incorporated residential house located in Sharjah and Al-Ain cities using DesignBuilder software have been evaluated. According to the simulation results, for both cities PCM 32 was found to be the most effective with energy consumption reduction around 19%. The optimum PCM decreased the maximum temperature by up to 1.09°C and was able to reduce temperature fluctuations. For constant volume, the influence of different thicknesses and surface area on energy savings was evaluated and it was found that energy savings increased with the increase in surface area and decrease in thickness of PCM layer. Finally, from correlation analysis, it was found that relationship between energy savings and meteorological factors like wind speed, temperature, relative humidity and solar radiation exist.

Thermal performance and energy efficiency of building integrated with PCMs in hot desert climate region

Researchers have used phase change materials to reduce energy cost, dependency on fossil fuels and make the buildings energy efficient. However, the following issues have not been addressed yet. (a) How PCM influence the thermal performance and energy efficiency of PCM integrated buildings with local construction details in hot desert climate? (b) How energy savings in PCM integrated buildings are related to meteorological factors such as wind speed, temperature and relative humidity? (c) What is the economic and environmental impact of PCM integrated buildings located in BWh climate? Hence, the thermal performance and energy efficiency performance of PCM integrated residential building located in eight different cities (Abu-Dhabi, Dubai, Faisalabad, Mecca, Jodhpur, Nouakchott, Cairo and Biskra) from hot desert climate zone was evaluated with thirteen different PCMs in EnergyPlus. Test results showed that the optimum PCMs were able to reduce the temperature fluctuations and the maximum temperature reduced by up to 2.04 °C. Except for Cairo and Biskra, the best PCM were close to the cooling set point suggesting that in hot desert climate, PCM with higher melting points perform better. For selected cities, the energy consumption reduction varied from 17.97 to 34.26% while for a given volume of PCM, energy efficiency increased with the increase in the surface area and decrease in the thickness of PCM layer. From multiple regression analysis, the equation describing the dependency of energy saving on meteorological parameters was obtained. Conclusively, economical and environmental aspects of the incorporation of PCM in a residential building located in a hot desert climate were discussed.

A comparative study on battery thermal management using phase change material (PCM)

The present study aims at battery thermal management of Electric Vehicles (EV). Li-ion battery used in EVs has an optimum operating range of 25 °C to 60 °C beyond which battery doesn’t perform efficiently. Thus thermal management of EV is catching importance in the industry. There are two ways in which Thermal management of EV’s can be done. First is from inside by controlling the dimensions of Electrode and reducing the resistance. This helps in reducing the Power dissipation and hence preventing the Electrolyte explosion which can result in overall battery damage. Second is from outside by employing various methods (i) by Air (ii) by liquid (iii) by PCM which is called the battery thermal management of the vehicle System. The first two methods of cooling are active cooling methods and involve lot of auxiliary parts which calls for balancing of the system. Moreover, active cooling method also lowers the vehicle’s efficiency. The heat generation is closely dependent upon the discharge rates and the ambient condition. Therefore, current study is focussed on passive methods of cooling through the use of PCM (Capric acid) which has been placed around the periphery in the battery pack. Different thickness of PCM layer 3 mm, 7 mm, 9 mm and 12 mm have been taken. Two ambient conditions of 294 K and desert condition (323 K) has been explored in this study and the effect of Capric acid as a PCM has been tested and compared with the traditionally used paraffins. PCM layer of 3 mm thickness proves to be optimum and lowered the maximum temperature in the battery to 305 K.

Numerical study on the thermal performance of pipe-embedded PCM building envelope in the heating season

In this paper, a comprehensive numerical model is presented and validated to simulate the dynamic heat transfer behavior of pipe-embedded PCM building envelope in a typical day of heating season. The performance of the pipe-embedded PCM envelope are investigated and compared with traditional envelope as well as the envelope integrated only with a PCM interlayer. Further, the influence of two design parameter including pipe spacing and thickness of PCM layer are studied and analyzed simultaneously. Finally, the influence of building orientation on the thermal behavior of pipe-embedded PCM envelope was evaluated. The simulation results proved the effectiveness of the numerical results in this paper support and highlight the potential of pipe-embedded PCM envelope for energy saving and indoor comfort lifting. This study will help develop a comprehensive understanding of dynamic thermal behavior of pipe-embedded PCM envelope utilizing low-grade energy source.

Influence of glazed roof containing phase change material on indoor thermal environment and energy consumption

Glazed roof has a convenient place to receive solar radiation, however its bad thermal mass affects the indoor thermal environment and energy consumption. In the present work, the effect of glazed roof filled with phase change material on its thermal mass was experimentally investigated and compared with conventional glazed roof. Experiments with different PCM melting temperatures, PCM layer thicknesses and glazed roof slopes were performed to analyze their effect on the energy consumption and dissatisfaction rate of indoor thermal environment. Also, a general economic analysis was performed to assess the viability of glazing units containing PCM. The results show that the energy consumption of glazed roof filled with PCM is significantly less than that of air, and up to 47.5% of energy saving can be achieved. Payback period can be reduced to 3.3 years by proper selection of PCM melting temperature. Increasing the melting temperature of PCM can effectively decrease the temperature of internal surface of glazed roof, but has a slight influence on the dissatisfaction rate of indoor thermal environment. Increasing the thickness of PCM layer decreases the peak temperature of internal surface of glazed roof and indoor chamber, the energy consumption and the dissatisfaction rate. The highest energy consumption and dissatisfaction rate are obtained at 20° of the inclination angle.

Experimental investigation of optical and thermal performance of a PCM-glazed unit for building applications

In present work, optical and thermal performances of a PCM-glazed unit were experimentally investigated compared with that filled with air, and the influences of solar irradiance, melting temperature and PCM layer thickness on three parameters were analyzed including the transmittance, the temperature difference between upper and bottom surfaces, and the interior surface temperature of the glazed unit. The results show that the thermal performance of glazed unit filled with PCM is improved compared with that of air, and transmittance of glazed unit is 50% when the PCM is liquid. Solar irradiance and PCM layer thickness both have effects on the optical and thermal performance of glazed unit, but the effect of melting temperature on thermal performance can be neglected. Increasing the PCM thickness can effectively decrease the heat loss of glazed unit filled with PCM, but the PCM thickness in the glazed unit is not beyond 16mm considering the optical performance of glazed unit.