Frank Bruno

A Study on EGR Utilization in Natural Gas SI Engines Using a Two-Zone Combustion Model

In this study, a computer model of the four-stroke, spark-ignition natural gas engine thermodynamic cycle was developed. This model was constructed based on the mass and energy conservation principles and the combustion process was analyzed using a two-zone combustion model. The combustion angle was calculated by using relationships derived from a turbulent model. In addition, a kinetic model based on the extended Zeldovich mechanism was developed in order to show the ability of Exhaust Gas Recirculation (EGR) on reducing NO emissions. Furthermore, a knocking model was incorporated with the two-zone combustion model in order to predict any autoignition that might occur. The aim of this study is to investigate the effect of adding EGR to a stoichiometric mixture on engine performance and NO emissions under several inlet conditions. It was found that using EGR in cooled supercharged inlet conditions (333 K and 250 kPa) can reduce both NO emission and fuel consumption by about 80%, and 19 to 27% (depending on engine speed) respectively compared to a stoichiometric non EGR mixture condition.

9 – Using solid-liquid phase change materials (PCMs) in thermal energy storage systems

This chapter presents the principles of solid-liquid phase change materials (PCMs). The classifications of PCMs are discussed along with their advantages and disadvantages. PCMs can have problems in regards to incongruent melting, phase separation, subcooling and low thermal conductivity. Literature in relation to overcoming these issues has been reviewed and is summarised. Methods to measure the thermophysical properties of PCMs are presented. A list of key PCMs is given along with a comparison of their physical and technical properties. The future trend of PCM development is being conducted in conjunction with the application.

Geopolymer encapsulation of a chloride salt phase change material for high temperature thermal energy storage

In an effort to reduce the cost and increase the material compatibility of encapsulated phase change materials (EPCMs) a new encapsulated system has been proposed. In the current study a molten salt eutectic of barium chloride (53% wt.), potassium chloride (28% wt.) and sodium chloride (19% wt.) has been identified as a promising candidate for low cost EPCM storage systems. The latent heat, melting point and thermal stability of the phase change material (PCM) was determined by DSC and was found to be in good agreement with results published in the literature. To cope with the corrosive nature of the PCM, it was decided that a fly-ash based geopolymer met the thermal and economic constraints for encapsulation. The thermal stability of the geopolymer shell was also tested with several formulations proving to form a stable shell for the chosen PCM at 200°C and/or 600°C. Lastly several capsules of the geopolymer shell with a chloride PCM were fabricated using a variety of methods with several samples remaining stable after exposure to 600°C testing.

Investigation of Conducting Pins in Sphere Filled with Phase Change Material for Enhancing Heat Transfer in Thermal Energy Storage

The utilisation of phase change material (PCM) for thermal energy storage (TES) can significantly enhance the energy savings achievable with renewable thermal systems. Sphere based packed bed systems have been used as TES for many years. However, due to the thermal resistance within these systems, the heat transfer is limited and not all the PCM can be used effectively. This study focuses on heat transfer enhancement options for single PCM sphere in a TES system. An experimental investigation has been conducted using water as the PCM. The thermal performance of plain plastic sphere containing PCM has been compared to plastic sphere encapsulated with conducting pins. The heat transfer rate of the sphere with conducting pins was more than 34% that of the sphere without pins.

Numerical modeling of inward and outward melting of high temperature PCM in a vertical cylinder

Numerical study of inward and outward melting of a high temperature PCM in cylindrical enclosures were performed, using FLUENT 15. For validation purposes, numerical modeling of inward melting of a low temperature PCM was initially conducted and the predicted results were compared with the experimental data from the literature. The validated model for the low temperature PCM was used for two high temperature cases; inward melting of a high temperature PCM in a cylindrical enclosure and outward melting in a cylindrical case with higher aspect ratio. The results of this study show that the numerical model developed is capable of capturing the details of melting process with buoyancy driven convection for Ra<108, i.e. laminar flow, for a high temperature PCM and can be used for the design and optimization of a latent heat thermal storage unit.

Thermal Performance Of A Pcm Thermal Storage Unit

The thermal performance of a PCM thermal storage unit (TSU) is studied numerically and experimentally. The TSU under analysis consists of several flat slabs of phase change material (PCM) with melting temperature of-26.7 °C. Liquid heat transfer fluid (HTF) passes between the slabs to charge and discharge the storage unit. A one dimensional mathematical model was employed to analyze the transient thermal behavior of the storage unit during the melting and freezing processes. The model takes into consideration the temperature variations in the wall along the flow direction of the HTF. The paper compares the experimental and numerical simulation results in terms of HTF outlet temperatures during the melting period.

Analysis of the operation of a high-pressure micro-compressor

A high pressure micro-compressor is described which is driven by a cyclic pressure source. A theoretical analysis is presented for the case where the compressor is powered by the gases within the combustion chamber of an internal combustion engine. Results from this analysis are compared to those obtained from experiment. Operating characteristics of the compressor are described.

Experimental Investigation of PCM Spheres in Thermal Energy Storage System

This paper presents the experimental result of a small scale packed bed of random spheres with encapsulated PCM being charged and discharged. A vapor compression refrigerator and heated room with fan heater were used to supply constant heat transfer fluid at a minimum temperature of -28°C for charging and 16°C for discharging. Even though the temperature differences were not fixed in the experiments, the performance of the thermal energy storage is depicted in the form of effectiveness values. Different results were obtained for charging and discharging the thermal storage unit. The differences are expected to come from natural convection and super cooling. The super cooling during the charging process was as high as 6°C.

Numerical investigation of PCM in vertical triplex tube thermal energy storage system for CSP applications

Numerical study for phase change material (PCM) in high temperature vertical triplex tube thermal energy storage system (TTTESS) were performed, using ANSYS FLUENT 15. For validation purposes, numerical modelling of a low temperature PCM was initially conducted and the predicted results were compared with the numerical and experimental data from the literature. The average temperature for freezing and melting agree well with the results from the literature. The validated model for the low temperature PCM was extended to high temperature TTTESS; the supercritical CO2 as the heat transfer fluid (HTF) flows in the inside and outside tubes during the charging and discharging processes, whereas the Lithium and Potassium carbonate (Li2CO3-K2CO3) (35%-65%) as the PCM is enclosed between them. To enhance the heat transfer inside the PCM, eight fins have been incorporated between the internal and external tubes. This study also provides results demonstrating the effect of adding more fins relative to the case of n...

Modified T-history method for measuring thermophysical properties of phase change materials at high temperature

Latent heat storage using phase change materials (PCMs) can be used to store large amounts of energy in a narrow temperature difference during phase transition. The thermophysical properties of PCMs such as latent heat, specific heat and melting and solidification temperature need to be defined at high precision for the design and estimating the cost of latent heat storage systems. The existing laboratory standard methods, such as differential thermal analysis (DTA) and differential scanning calorimetry (DSC), use a small sample size (1-10 mg) to measure thermophysical properties, which makes these methods suitable for homogeneous elements. In addition, this small amount of sample has different thermophysical properties when compared with the bulk sample and may have limitations for evaluating the properties of mixtures. To avoid the drawbacks in existing methods, the temperature – history (T-history) method can be used with bulk quantities of PCM salt mixtures to characterize PCMs. This paper presents a modified T-history setup, which was designed and built at the University of South Australia to measure the melting point, heat of fusion, specific heat, degree of supercooling and phase separation of salt mixtures for a temperature range between 200 °C and 400 °C. Sodium Nitrate (NaNO3) was used to verify the accuracy of the new setup.Latent heat storage using phase change materials (PCMs) can be used to store large amounts of energy in a narrow temperature difference during phase transition. The thermophysical properties of PCMs such as latent heat, specific heat and melting and solidification temperature need to be defined at high precision for the design and estimating the cost of latent heat storage systems. The existing laboratory standard methods, such as differential thermal analysis (DTA) and differential scanning calorimetry (DSC), use a small sample size (1-10 mg) to measure thermophysical properties, which makes these methods suitable for homogeneous elements. In addition, this small amount of sample has different thermophysical properties when compared with the bulk sample and may have limitations for evaluating the properties of mixtures. To avoid the drawbacks in existing methods, the temperature – history (T-history) method can be used with bulk quantities of PCM salt mixtures to characterize PCMs. This paper presents a ...