Catalyst Modeling Challenges for Electrified Powertrains

The use of organic phase change materials (PCM – O) for thermal conditioning of agricultural products is proposed here. In particular, the capacity of PCM – O for controlling temperature is studied for sudden variation of external temperature conditions. Two different situations (a thermal jump and a periodic oscillation) using a simple and appropriate simulation model are presented. This model allows the evaluation of the temperature distribution and the interface position as a time function in the PCM. The obtained results show that the use of these substances is appropriate to control the required temperature of the agricultural products. Besides, these substances can reduce the cost during the transport of these products. PRACTICAL APPLICATIONS Several agricultural products, such as fruits and vegetables, need adequate conditions of storage and transport. It is necessary to maintain certain conditions of temperature and controlled atmosphere. Each product needs different temperature conditions. Temperatures must be maintained within a range that would guarantee the preservation of a product's organoleptic characteristics during a certain period. Thus, the use of phase change materials (PCM) for these purposes has been proposed, to reduce the energy consumption and, accordingly, the cost of transportation. Agricultural products can suffer thermal stress when they are exposed to extreme conditions, such as a sudden change or an oscillation in the external temperature. PCM can control and attenuate the influence of the external temperature on the agricultural product.

Heat storage process analysis in a heat exchanger containing phase change materials

Improving the energy efficiency of passive PCM system using controlled natural ventilation

Solar energy is one of the renewable energy sources and widely used to obtain thermal energy. The heat obtained from solar energy can be stored by using different systems. One of these systems is solar ponds. Solar ponds consist of layers whose salt density increases towards the bottom. In this study, the use of phase change materials to increase the heat storage performance of a model solar pond was investigated. The phase change material, Cetyl-palmitic acid eutectic mixture was prepared and its chemical properties were obtained by FT-IR spectroscopy. The thermophysical properties and surface morphologies were determined by using Differential Scanning Calorimetry and SEM. The obtained phase change material was applied to the inner surface of the heat storage zone. The temperature distribution of the solar pond was calculated numerically for with and without phase change material. As a result, it has been seen that the use of phase change materials with suitable thermophysical properties in solar ponds will contribute to long-term heat storage performance.

For the design of sustainable buildings, it is crucial with accurate methods to evaluate how alternative constructions will influence thermal comfort, as well as energy efficiency. This study introduces a model to investigate how the use of phase change materials (PCM)in building envelopes can influence the temperature stratification, which also influences the indoor thermal comfort. PCM is characterized by large latent heat in the melting/solidifying process during phase transition. Applications with PCM have been recognized as possible alternatives in building envelopes to improve thermal comfort as well as energy efficiency. The selection of the properties of the PCM, as well as how and where the PCM was installed in the building envelope, are crucial factors to be considered before application in practice. In this study, a simplified experimental set-up including a hot-box was used. The PCM material Climsel28 with different layers thicknesses was installed in the sidewall of a hot-box. Extruded polystyrene (XPS) foam boards were used as wall insulation material in the study. XPS was installed as a reference case and in different layer combinations with the PCM. The sequence of the XPS and PCM was varied. Temperature and heat flux were measured in different positions of the hot-box and on the tested walls. A 3D COMSOL model was developed to study the thermal performance of the system. The model was validated in the study using the collected experimental data. The results indicated that the developed COMSOL model can reasonably predict the performance of the system, both with and without the incorporation of PCM. Additionally, the measured temperature stratification were theoretically validated by the COMSOL model. The study gives indicative guidance of how PCMs can be installed in building constructions elements to reduce temperature peak loads and thus also contributing to an improvement of the indoor thermal comfort.

What about greener phase change materials? A review on biobased phase change materials for thermal energy storage applications

The investigation of relation between radiative and convective heat transfer coefficients at the ceiling in a cooled ceiling room

The efficient utilization of solar energy technology is significantly enhanced by the application of energy storage, which plays an essential role. Nowadays, a wide variety of applications deal with energy storage. Due to the intermittent nature of solar radiation, phase change materials are excellent options for use in several types of solar energy systems. This overview of the relevant literature thoroughly discusses the applications of phase change materials, including solar collectors, solar stills, solar ponds, solar air heaters, and solar chimneys. Despite the complexity of their availability and high costs, phase change materials are utilized in the majority of solar energy techniques because of the considerable technical improvements they provide. While numerous studies have investigated the progress of phase change materials used in solar energy applications such as photovoltaic systems, it is vital to understand the conceptual knowledge of employing phase change materials in various types of solar thermal energy systems. Investigations into the use of phase change materials in solar applications for the purpose of storing thermal energy are still being carried out to upgrade the overall performance. This paper briefly reviews recently published studies between 2016 and 2023 that utilized phase change materials as thermal energy storage in different solar energy systems by collecting more than 74 examples from the open literature. This study focuses on demonstrating the maturity of phase change materials and their integration into solar energy applications. Based on the findings, proposals for new research projects are made.

Thermo-energy performance of a phase change material integrated into lightweight hollow concrete roofs in warm–subhumid climate

This research investigates the use of phase change materials (PCMs) in thermal energy storage (TES) unit-based cooling systems to increase the efficiency of air conditioners (ACs) by reducing the air inlet temperature. This study aims to evaluate different configurations of PCM enclosures, and different PCMs (paraffin and salt hydrate), by changing the speed of inlet air to achieve heat reduction of inlet air. The study includes experimental and simulation investigations. Every configuration simulates the hot-season atmospheric conditions of the UAE. A duct containing enclosures of paraffin RT-31 and salt hydrate (calcium chloride hexahydrate) was used for the simulation study using ANSYS/Fluent. A conjugate heat transfer model employing an enthalpy-based formulation is developed to predict the optimized PCM number of series and optimum airflow rate. Four designs of the AC duct were modelled and evaluated that contained one to four series of PCM containers subjected to different levels of supplied air velocities ranging from 1 m/s–4 m/s. The simulation study revealed that employing four series (Design 4) of PCM enclosures at a low air velocity of 1 m/s enhanced the pre-cooling performance and reduced the outlet air temperature to 33 °C, yielding a temperature drop up to 13 °C. The performance of salt hydrate (calcium chloride hexahydrate) was observed to be better than paraffin (RT-31) in terms of the cooling effect. Characterization of paraffin wax (RT-31) and salt hydrate was performed to establish the thermophysical properties. The experimental setup based on a duct with integrated PCM enclosures was studied. The experiment was repeated for three days as the repeatability test incorporating RT-31 as the PCM and a 3 °C maximum temperature drop was observed. The drop in the outlet air temperature of the duct system quantifies the cooling effect. Net heat reduction was around 16%.

The use of phase change materials (PCMs) in thermal storage is not a new concept, but engineers are continually finding new ways to utilize them in a wide range of applications. A PCM takes advantage of high latent heat in the phase change process to store large amounts of heat while undergoing only a small change in temperature. This property makes PCMs suitable for thermal storage purposes in a wide range of engineering applications. Due to the nature of these applications, it is vital to have a precise knowledge of the thermal characteristics of any PCM. Unfortunately, due to the low thermal conductivities and high latent heats found in PCMs, current measuring tools such as differential scanning calorimetry, provide inconsistent results. This paper conjectures that these errors come from the effects of low thermal diffusivity samples as well as improper data analysis methods.

A phase change material (PCM) is a substance capable of storing or releasing large amounts of energy typically when melting or solidifying. The use of PCM is promising for the cooling of electric machines with high-load short transient duty, such as aircraft stator generators (S/G). During the starting phase, which lasts a couple of seconds, a substantial amount of heat has to be extracted from the machine windings, while the steady-state operation is less thermally constraining. In order to ensure sufficient cooling capabilities, PCMs should be placed as close as possible to the winding conductors due to their low thermal conductivity. This paper investigates a novel integration approach, where PCMs are placed inside hollow conductors (HCs). Numerical and experimental analyses have been completed on a range of hollow conductors filled with PCMs to gain a first insight into the benefits of this cooling method. Detailed descriptions of the proposed cooling technique have been supplemented with measured data from tests on a hollow conductor exemplar filled with PCM. An illustration of a practical use of the developed method on a helicopter turbine S/G is also presented.

A two-dimensional numerical solution has been obtained of the effect of a venetian blind on the conjugate heat transfer at an indoor window glazing. A solution has been obtained to the coupled laminar free convection and radiation heat transfer problem, including conduction along the blind slats. The local convective Nusselt number distributions were found to compare well with published experimental data for an aluminum blind. Also, there was good qualitative agreement with temperature and flow field visualization photographs. The results show that, over a wide range of Rayleigh numbers, an aluminum venetian blind can have a strong effect on the heat transfer rate from the indoor window glazing. Depending upon the specific conditions, the average convective heat transfer rate can either increase or decrease. However, for all cases studied, the blind was found to substantially reduce the radiative heat transfer rate from the window, even when the slats were fully open.

Investigating the performance improvement of lithium-ion battery cooling process using copper fins and phase change materials (PCMs)

Thermal management of Li-ion battery with phase change material for electric scooters: experimental validation