Enhancement of the Thermal Energy Storage Using Heat-Pipe-Assisted Phase Change Material

Usage of phase change materials' (PCMs) latent heat has been investigated as a promising method for thermal energy storage applications. However, one of the most common disadvantages of using latent heat thermal energy storage (LHTES) is the low thermal conductivity of PCMs. This issue affects the rate of energy storage (charging/discharging) in PCMs. Many researchers have proposed different methods to cope with this problem in thermal energy storage. In this paper, a tubular heat pipe as a super heat conductor to increase the charging/discharging rate was investigated. The temperature of PCM, liquid fraction observations, and charging and discharging rates are reported. Heat pipe effectiveness was defined and used to quantify the relative performance of heat pipe-assisted PCM storage systems. Both experimental and numerical investigations were performed to determine the efficiency of the system in thermal storage enhancement. The proposed system in the charging/discharging process significantly improved the energy transfer between a water bath and the PCM in the working temperature range of 50 & DEG;C to 70 & DEG;C

Fabrication of Nanobiosensor for Early Detection of Cancer Biomarker

The common problem with all different forms of cancer is that many people experience the symptoms, and have it diagnosed when it is too late. Nanobiosensors have become essential tools in early cancer biomarker detection and quantification, in which nanoprobe materials and composition play crucial roles in achieving sensitive and stable detection. Although nanobiosensing techniques are proved to be robust and efficient, most of them are time-consuming and still suffer from the lack of accuracy and sensitivity for clinical diagnostics. This thesis aimed to address these shortcomings by developing a new class of hybrid nanobiosensing platform based on low dimensional materials with niche electro-optical properties and favorable surface chemistry. The multifunctional carbon nanomaterials (core optical element), named as Carbon Dots (CDs), were engineered through a systematic hydrothermal reaction to achieve the right affinity features for conjugation to a wide range of macromolecules (e.g., peptides and proteins) and polymers (e.g., hydrogels). The hybrid nanobiosensor arrays (named as PACD) employing a family of helix-loop-helix polypeptides de novo, carbon, and gold nanomaterials were fabricated through a step-wise covalent self-nanoassembly. This method is based on matrilysin-digestible peptides (i.e. JR2EC) that are anchored between gold nanoparticle (AuNPs) cores (~30-50 nm) and carbon quantum dot (CDs) satellites (~2-7 nm). The AuNP–CDs produce ideal optical signals, with noticeable fluorescence quenching effects. Upon peptide cleavage by matrilysin, CDs leave the surface of gold nanoparticles, resulting in ultra-fast (nearly 30 seconds) detectable violet and visible fluorescent signals at the limit of detection of 30 nM. The overall knowledge of the underpinnings of synthesizing low-dimensional materials, synthetic bioreceptors and the modular self-assembled nanoarchitectures will make it possible to aim for a universal-multifunctional platform for multiplex detection of several diseases, targeted drug delivery, and drug discovery

Investigation on Thermal Conductivity, Viscosity and Stability of Nanofluids

In this thesis, two important thermo-physical properties of nanofluids: thermal conductivity and viscosity together with shelf stability of them are investigated. Nanofluids are defined as colloidal suspension of solid particles with the size of lower than 100 nanometer. Thermal conductivity, viscosity and stability of nanofluids were measured by means of TPS method, rotational method and sedimentation balance method, respectively. TPS analyzer and viscometer were calibrated in the early stage and all measured data were in the reasonable range. Effect of some parameters including temperature, concentration, size, shape, alcohol addition and sonication time has been studied on thermal conductivity and viscosity of nanofluids. It has been concluded that increasing temperature, concentration and sonication time can lead to thermal conductivity enhancement while increasing amount of alcohol can decrease thermal conductivity of nanofluids. Generally, tests relating viscosity of nanofluids revealed that increasing concentration increases viscosity; however, increasing other investigated parameters such as temperature, sonication time and amount of alcohol decrease viscosity. In both cases, increasing size of nanofluid results in thermal conductivity and viscosity reduction up to specific size (250 nm) while big particle size (800 nm) increases thermal conductivity and viscosity, drastically. In addition, silver nanofluid with fiber shaped nanoparticles showed higher thermal conductivity and viscosity compared to one with spherical shape nanoparticles. Furthermore, effect of concentration and sonication time have been inspected on stability of nanofluids. Test results indicated that increasing concentration speeds up sedimentation of nanoparticles while bath sonication of nanofluid brings about lower weight for settled particles. Considering relative thermal conductivity to relative viscosity of some nanofluids exposes that ascending or descending behavior of graph can result in some preliminary evaluation regarding applicability of nanofluids as coolant. It can be stated that ascending trend shows better applicability of the sample in higher temperatures while it is opposite for descending trend. Meanwhile, it can be declared that higher value for this factor shows more applicable nanofluid with higher thermal conductivity and less viscosity. Finally, it has been shown that sedimentation causes reduction of thermal conductivity as well as viscosity. For further research activities, it would be suggested to focus more on microscopic investigation regarding behavior of nanofluids besides macroscopic study

HEAT RECOVERY FROM A NATURAL GAS POWERED INTERNAL COMBUSTION ENGINE BY CO2 TRANSCRITICAL POWER CYCLE

The present work provides details of energy accounting of a natural gas powered internal combustion engine and achievable work of a utilized CO2 power cycle. Based on experimental performance analysis of a new designed IKCO (Iran Khodro Company) 1.7 litre natural gas powered engine, full energy accounting of the engine were carried out on various engine speeds and loads. Further, various CO2 transcritical power cycle configurations have been appointed to take advantages of exhaust and coolant water heat lost. Based on thermodynamic analysis, the amount of recoverable work obtainable by CO2 transcritical power cycles have been calculated on various engine conditions. The results show that as much as 18 kW power could be generated by the power cycle. This would be considerable amount of power especially if compared with the engine brake power

Optimized energy recovery in line with balancing of an ATES

The present study explores the potential imbalance problem of the Aquifer Thermal Energy Storage (ATES) system at the Eindhoven University of Technology (TU/e) campus, Eindhoven. This ATES is one of the largest European aquifer thermal energy storage systems, and has a seasonal imbalance problem. Reasons for this issue may be the high cooling demand from laboratories, office buildings and the direct ATES cooling system. Annually, cooling towers use on average 250 MWh electricity for the removal of about 5 GWh of excess heat from the ATES to the surroundings. In addition, the TU/e uses a large amount of natural gas for heating purposes and especially for peak supplies. Recovering the surplus heat of the ATES, a CO2 Trans-critical Heat Pump (HP) system to cover particularly peak demands and total heating demand is proposed, modeled and optimized. The model is validated using data from International Energy Agency. Based on simulation results, 708294 nm3 of natural gas are saved where two different scenarios were considered for the ATES efficiency, cost saving and green house gas reduction. In scenario I, the COP of the ATES increased up to 50% by which K€ 303.3 energy cost and 1288.5 ton CO2 are saved annually. On the other hand, it will be shown that the ATES COP in Scenario II will improve up to 20%. In addition, the proposed energy recovery system results in a 606 ton CO2 -reduction and K€152.7 energy cost saving for the university each year

An Enhanced Phase Change Material Composite for Electrical Vehicle Thermal Management

Lithium-ion (Li-ion) battery cells are influenced by high energy, reliability, and robustness. However, they produce a noticeable amount of heat during the charging and discharging process. This paper presents an optimal thermal management system (TMS) using a phase change material (PCM) and PCM-graphite for a cylindrical Li-ion battery module. The experimental results show that the maximum temperature of the module under natural convection, PCM, and PCM-graphite cooling methods reached 64.38, 40.4, and 39 °C, respectively. It was found that the temperature of the module using PCM and PCM-graphite reduced by 38% and 40%, respectively. The temperature uniformity increased by 60% and 96% using the PCM and PCM-graphite. Moreover, some numerical simulations were solved using COMSOL Multiphysics® for the battery module

On design for additive manufacturing (DAM) parameter and its effects on biomechanical properties of 3D printed ceramic scaffolds

Biological and mechanical functions are sometimes two conflicting characteristics in bone tissue scaffolds, whichnecessitates a trade-offbetween these two properties in load-bearing applications. In this article, a systematiccomputational analysis was performed to investigate the effects of controllable fabrication factors (e.g. Designfor Additive Manufacturing (DAM) Parameter) on compressive strength and permeability of ceramic scaffoldsfabricated by robocasting technique, followed by a study on multiobjective optimization to determine the op-timal structural parameters. To evaluate the compressive strength of scaffolds, the eXtended Finite ElementMethod (XFEM) was adopted to model fracture behavior in the scaffolds. Computational Fluid Dynamics (CFD)simulations were also conducted to analyze the permeability of the scaffold structures to quantify their bio-transport capacity. Furthermore, experimental compression tests andfluidflow tests were conducted for somerepresentative scaffolds to demonstrate the effectiveness of both XFEM and CFD simulations. The computationalresults indicated that the anisotropic degree of permeability could be controlled by adjusting particular geo-metric parameters during design and fabrication process, thereby enabling desirable directional permeability ineach of longitudinal and transverse directions. Moreover, the XFEM results demonstrated that compressivestrength of the scaffolds can be improved by at least 70 % while the porosity is kept unchanged, which is ofconsiderable implication to design of robocast ceramic scaffolds for weight-bearing tissue engineering