Showing papers in "Thermal science and engineering in 2018"

Waste Heat Recovery Technologies and Applications

Abstract: Horizon 2020 Project “Design for Resource and Energy efficiency in CerAMic Kilns- DREAM Project (Grant No: 723641), Horizon 2020 Industrial THERMal energy recovery conversion and management (Grant No:680599) and ESPRC (Grant No: EP/P004636/1)

Pumped Thermal Electricity Storage: A technology overview

Abstract: A large penetration of variable intermittent renewable energy sources into the electric grid is stressing the need of installing large-scale Energy Storage units. Pumped Hydro Storage, Compressed Air Energy Storage and Flow Batteries are the commercially available large-scale energy storage technologies. However, these technologies suffer of geographical constrains (such as Pumped Hydro Storage and Compressed Air Energy Storage), require fossil fuel streams (like Compressed Air Energy Storage) or are characterised by low cycle life (Flow Batteries). For this reason, there is the need of developing new large-scale Energy Storage Technologies which do not suffer of the above-mentioned drawbacks. Among the in-developing large-scale Energy Storage Technologies, Pumped Thermal Electricity Storage or Pumped Heat Energy Storage is the most promising one due to its long cycle life, no geographical limitations, no need of fossil fuel streams and capability of being integrated into conventional fossil-fuelled power plants. Based on these evidences, in the present work, a literature survey on the Pumped Thermal Electricity Storage technology is presented with the aim of analysing its actual configurations and state of development.

A review of Backward-Facing Step (BFS) flow mechanisms, heat transfer and control

Abstract: Backward-Facing Step (BFS) flow is one representative model for separation flows, which can be widely seen in aerodynamic flows (airfoil, spoiler, high attack angle process), engine flows, condensers, vehicles (cars, boat), heat transfer systems, and even the flow around buildings, etc. The flow separation after a simple stage will introduce separation bubble formation, evolution and re-attachment process, which is dependent on the BFS geometric design, the inlet and outlet conditions, turbulent intensity, as well as heat transfer conditions. In the past decades, it has been widely studied by various theoretical, experimental and numerical methods. Considering the importance of BFS flow in both theoretical and engineering aspects, this paper is focused on a review study of BFS flows from fundamental understandings to various experimental and numerical developments in a historical viewpoint. Basic models and the parameter-based after-step flow laws are summarized and categorized in this study. It is shown that the step size (duct expansion ratio) will define the basic re-circulation and re-attachment process, while the coupled effects of inflow parameters and the perturbation designs also help shape the flow behaviors after BFS. The review is also extended with model generalizations and the implications on system design, especially the heat transfer effects and the representative control designs are discussed in detail. Future trends and prospects in BFS studies are also included in this study.

Simultaneous investigations the effects of non-Newtonian nanofluid flow in different volume fractions of solid nanoparticles with slip and no-slip boundary conditions

Abstract: In this study, the laminar and forced flow of non-Newtonian nanofluid in a two-dimensional microtube has been numerically simulated. The non-Newtonian, pseudo-plastic fluid is included of a solution with 0.5% wt fraction of CMC in Water as the base fluid. In this research, in order to increase the heat transfer rate, the mentioned non-Newtonian fluid has been combined with volume fractions of 1 and 1.5% of CuO nanoparticle and has been created the non-Newtonian cooling nanofluid. In this investigation, the effect of slip velocity boundary condition on the wall of microtube has been considered. In order to have an accurate estimation of dynamic viscosity of non-Newtonian nanofluid, the power-law model, for numerical simulation has been used. This research has been investigated in Reynolds numbers of 100, 500, 1500 and 2000. The results indicate that, the increase of volume fraction of solid nanoparticles and slip velocity coefficient, cause the increase of heat transfer. By enhancing the slip velocity coefficient, better mixing accomplishes which causes the reduction of temperature gradients among the fluid layers close to the surface. In Reynolds numbers of 1500 and 2000, comparing to Reynolds numbers of 100 and 500, Nusselt number, on the microtube wall increases significantly.

Optimization of tensile strength in TIG welding using the Taguchi method and analysis of variance (ANOVA)

Abstract: The main criteria discussed in this paper concern the welding optimization parameters and tensile strength of duplex stainless steel 2205 by tungsten inert gas welding based on Taguchi method and analysis of variance Taguchi method of orthogonal L9 design experiment is carried out using orthogonal array for defining the problem occur on welding process and to reduce the error occurred in the neural network for the prediction of output The neural network is a mathematical prediction model for the optimization process using back propagation algorithm Analysis of variance (ANOVA) is a decision tool for detecting the variation of process parameters, it is a statistical technique for find out the optimal level of factors for the verification of the optimal design parameters through confirmation experiments The purpose of this paper to increase the tensile strength, hardness and depth of weld by varying the parameters such as current, time, speed, variation of oxide fluxes, electrode diameter and gas flow rate The Mat lab software is used for analyzing results and it shows that neural network coupled with Taguchi method and Anova is an effective method for optimizing the weld quality of material

Heat transfer enhancement using different types of vortex generators (VGs): A review on experimental and numerical activities

Abstract: This paper presents a comprehensive review on heat transfer augmentation and pressure loss reduction of compact heat exchanger (CHXs) by using interrupted surfaces in the form of vortex generators (VGs). The influence of type, shape, and design and attack angle of VGs on enhancement of heat transfer rate and pressure loss are widely discussed. The sole objective of this review is to gather major thermodynamic features of CHXs presented by researchers through both experimental and numerical investigation for innovative designing purpose of heat exchangers. We have evaluated the effects of different types of vortex generators, their arrangement, location, attack angles and height on heat transfer and friction characteristics of heat exchangers. It was noticed that longitudinal vortices induced by vortex generators leads to the reduction of wake region behind tubes, augmentation of turbulence intensity and higher flow mixing. However, the intensity and strength of these vortices is strictly dependent on Reynold number. Delta winglet type vortex generators provide better heat transfer performance than rectangular winglet type vortex generators. Location of these winglets is quite suitable in downstream region than upstream region. Moreover, flow visualization techniques are discussed to analyze the vortex formation due to VGs at microscopic level.

Analytical and numerical solution of non-Newtonian second-grade fluid flow on a stretching sheet

Abstract: This paper analyzes flow and heat transfer of an incompressible homogeneous second-grade fluid over a stretching sheet channel. Further, nonlinear differential equations solving this problem are presented which are solved by the hemotopy perturbation method (HPM). The main goal of this paper is to compare the results of solving the velocity and temperature equations in the presence of k changes through HPM and Nam for introducing HPM as a precise and appropriate method for solving nonlinear differential equations. In the following, the effects of changes in the viscoelastic parameter (k) values on velocity profile and Prandtl number ( σ ) on temperature profile are studied. The most important results of these comparisons and studies are the high precision of the hemotopy perturbation method in solving nonlinear differential equations and also the dual behavior of k in velocity and temperature profiles, the direct relation of σ and with temperature distribution can also be mentioned.

A review and comparative assessment of direct ammonia fuel cells

Abstract: In this study, we present a comparative assessment of direct ammonia fuel cells and a discussion of these from various perspectives by considering the effective criteria. The effect of electrolyte and electrode materials, electrolyte thicknesses and operating temperatures on the performance of direct ammonia fuel cells are studied and discussed comparatively for evaluation purposes. A comparison of which cell types and configurations provide the optimum performance is conducted by utilizing the experimental results reported in the literature. The results of this study are expedient to provide important inferences about the performances of direct ammonia fuel cells. Ammonia fed oxygen ion conducting Samarium doped ceria electrolyte based solid oxide fuel cells have comparatively the highest peak power density of 1190 mW/cm2 when operated at 650 °C with a 10 µm thick electrolyte. Direct ammonia proton conducting electrolyte based solid oxide fuel cells have lower cell performance than oxygen ion conducting fuel cells due to the dilution of hydrogen at the anode by undecomposed ammonia as well as formed nitrogen gas. The operating temperature of the fuel cell and electrolyte thickness affect the cell performance considerably. A 200 °C increase in operating temperature increases the peak power density by nearly three to four times for ammonia fed solid oxide fuel cells. The molten alkaline electrolyte based fuel cells can be a promising technology. Further research is required for these type of fuel cells to investigate their performance with low electrode separation distance and more conductive alkaline electrolytes.

Pyrolysis of domestic based feedstock at temperatures up to 300 °C

Abstract: This article reports the state of the art of the characteristics of products derived from the pyrolysis of municipal solid waste. The by-products which arise at more elevated temperatures are discussed so that the outcomes of low temperature pyrolysis may be put into context. Our throwaway society is a globally growing issue, the continued discarding of valuable resources into landfill sites is highly undesirable due to many of these materials being non-biodegradable and some may produce toxic gases which are harmful to the environment if discarded in an uncontrolled way. Domestic and industrial sorting and transport of discarded resources result in an increase in carbon footprint as well as a high cost. Therefore, an alternative resource management method is required in order to achieve a more sustainable and less harmful method of managing these valuable resources in the future. Below 300 °C, the products of pyrolysis are generally expected largely to contain biochar, bio-oil and syngas. However, the phase distribution and chemical composition of the products is highly dependent on the feedstock used as well as the operating parameters of the process. Plant based feedstock produces more biochar while plastic based feedstock produces more bio-oil. The composition of products can be analysed using gas chromatography/mass spectrometry. Current applications of pyrolysis are focused on high temperatures due to the increased yields of gases and bio-oils, which are more valuable. Biochar, however, is becoming increasingly popular due to its various applications such as a filter material for water purification. Low temperature pyrolysis is an area where further research is required in order to produce economically viable processes.

Investigation of finned heat sink performance with nano enhanced phase change material (NePCM)

Abstract: In this research, the performance of a finned heat sink with phase change material (PCM) is numerically simulated for two cases: with and without PCM. The results showed an improvement in heat sink performance when using PCM. One of the defects of PCMs is their low thermal conductivity. One solution to deal with this problem is the addition of high thermal conductivity nanoparticles to PCMs. For this purpose, the effects of adding copper oxide and aluminum oxide nanoparticles to paraffin PCMs were investigated. The results show that the performance of heat sink is improved by adding a low percentage of nanoparticles (2%). However, by increasing volume fraction of nanoparticles to 6%, not only the heatsink performance does not improve, but also decreases.

Review on solar Stirling engine: Development and performance

Abstract: Solar dish-Stirling system has proved to be the most efficient way to generate electricity using solar energy. Due to the increasing commercialization of this technology, the need for maximizing overall efficiency, and minimizing losses and cost has become an important area of interest for researchers. In the past few years, the research on modeling, thermodynamic performance analysis, simulation studies and techno-economic analysis of solar dish-Stirling engines have gained pace. Many parameters like concentration ratio, absorber temperature, hot side temperature, cold side temperature, regenerator effectiveness, working fluid, dead volume and average working pressure values are generally considered for the performance analysis of dish-Stirling systems. Researchers have observed that by increasing the concentrating ratio, the absorber temperature and thermal efficiency increaseses. The maximum thermal efficiency reported for the dish-Stirling system is 32% at an absorber temperature of 850 K for the concentration ratio of 1300. Although regenerator losses tend to reduce the overall efficiency. Energy and Exergy efficiency for the dish-Stirling system were reported to be 17% and 19% respectively wherein major losses occurred at the receiver. However, thermal efficiency as high as 84% can be obtained for the receiver system. A synthesis of results indicates that dish-Stirling technology can produce power cost-effectively with comparatively better performance than other renewable systems. Moreover, incorporation of hybridization and thermal storage have emerged as a particularly favourable option for more continuous operation of the system.

Development and analysis of a technique to improve air-cooling and temperature uniformity in a battery pack for cylindrical batteries

Abstract: In this paper, a passive approach to improve temperature uniformity in a simple battery pack, in which an inlet plenum is added as a secondary inlet to a battery pack with an axial air flow, is examined. This inlet plenum changes the direction of the flow and eliminates the problem of recirculation and non-availability of air between the adjacent cells. Three different configurations are considered to examine the effects of the orientation of inlet plenum and the cells. CFD (computational fluid dynamics) is used to perform detailed simulations of the battery packs and the results are validated with data obtained experimentally from one of the battery pack configuration. The thermal performance of the battery packs is compared to the baseline case, and the results indicate an average maximum temperature reduction of the cells by ∼4% and an improvement in temperature uniformity of the cells by ∼39%. This is a simple battery pack that uses forced air passive cooling (no moving parts required in the battery pack) and introduces mixing and turbulence in the air flow to increase the temperature uniformity in the battery pack.

Investigation of thermal performance of unidirectional flow porous bed solar air heater using MLP, GRNN, and RBF models of ANN technique

Abstract: In the present work, Multi-layer perceptron (MLP), Generalized regression neural network (GRNN), Radial basis function (RBF) and Multiple linear regression (MLR) models has been used to predict the thermal performance of unidirectional flow porous bed solar air heater. These four models have been constructed on the basis of actual experimental data and calculated values. Total 96 experimental data sets have been used in the present work. In GRNN, RBF and MLP models, six input parameters such as mass flow rate, wind speed, atmospheric temperature, inlet fluid temperature, fluid mean temperature and solar intensity were used in input layer, and one variable, the thermal efficiency was used in output layer. Same parameters were used in MLR model. It is observed that GRNN model is the best model due to lowest error and highest value of R2 as compared to MLP, RBF and MLR model performances. It is found that the value of MAE, RMSE and R2 for GRNN model are 1.1128E−03, 5.9284E−06 and 0.99758 respectively, and the model efficiency is 0.99760, which is the highest value as compared to other model. These results confirmed that the GRNN model is appropriate model to predict the thermal performance of solar air heater.

China’s R&D of advanced ultra-supercritical coal-fired power generation for addressing climate change

Abstract: Climate change is today’s common challenge faced by all humanity. The accumulated carbon dioxide emissions from the fossil fuels consumption have resulted in significant global warming. Among the commercial-ready technologies, the advanced ultra-supercritical (USC) technology is the most convenient solution for coal-fired power generation to address CO2 mitigation, especially in countries where electricity generation is primarily dependent upon coal. This paper reported the research and development of advanced ultra-supercritical technology in China in the past ten years and its technology roadmap. The USC R&D has suffered three stages: technology introduction, absorption, and innovation. Its characteristic is the transition to higher live steam parameters, larger capacity, and steam double–reheat. Except for the introduction of several milestones in China’s USC development, emphasis was placed on the first 1000 MW double-reheat USC unit in the Taizhou Power Plant and ongoing research for a future 700 °C USC program. This paper provided a status report on the progress achieved to date in China.

Experimental and computational investigation of a latent heat energy storage system with a staggered heat exchanger for various phase change materials

Abstract: This work reports the operation of a Latent Heat Thermal Energy Storage system (LHTES) utilizing a staggered heat exchanger (HE) and using various organic Phase Change Materials (PCMs). In a LHTES test rig set measurements regarding energy storage and release were performed in the working temperature range of each Phase Change Material. Nominal melting temperatures of the PCMs used were 40–53 °C. Computational Fluid Dynamics (CFD) simulation was applied to follow the operation of the test rig. The test rig consisted of a compact insulated tank, filled with PCM, a staggered heat exchanger to supply or extract thermal energy by the PCM and a water pump to circulate water as a Heat Transfer Fluid (HTF). Different HTF flow rates affect charging (melting) and discharging (solidification) processes but more significant was the effect of heat transfer mechanisms occurring. The latter was confirmed by inserting buoyancy currents created due to convection in a CFD simulation program where melting time was reduced compared to the same conditions with only conduction occurring. The suggested LHTES configuration is a promising compact unit despite the PCMs thermal resistance and solidification hysteresis phenomena, as well as the heat transfer mechanism strongly affecting the energy storage process.

Thermal performance enhancement of flat-plate solar collectors by means of three different nanofluids

Abstract: Solar energy, which comes first among renewable energy sources, enables efficient use of energy with many applications due to its low operating cost and environmental friendliness. In this study, we experimentally investigated the effects on thermal efficiency of nanofluid and water as working fluids in flat-plate solar collector hot water solar energy systems. Nanofluids were prepared by adding Al2O3, CuO, and TiO2 nanoparticles at 0.2, 0.4, and 0.8 vol% into distilled water, and then the thermophysical properties (thermal conductivity, viscosity) of the prepared nanofluids were determined. Flow rate was adjusted to 250 l/h at given concentrations for each nanofluid in the experimental setups and data such as collector inlet and outlet temperatures, ambient and tap water temperatures; radiation, humidity, and wind speed were measured and recorded. The obtained data were used to calculate efficiencies according to ASHRAE 93-2003 standards. When compared with water, the results indicated that the use of nanofluid increased collector efficiency.

Effect of fly ash particle size on thermal and mechanical properties of fly ash-cement composites

Abstract: In this study, fly ash was used in concrete and plaster in place of sand and the impact of fly ash grain size on thermal and mechanical performance of composite material was examined. Fly ash used in the experiments was received from Soma Thermal Power Station and separated into the various grain size groups namely unsieved, >75 × 10-6 m, (45–75) × 10-6 m and Some tests were performed using the new products to find out their detailed properties including density, thermal conductivity, compressive tensile strength, and elasticity module and water absorption. It was found in the experiments that (i) as the grain size diameter decreased, ash density increased 16.12%, and porous structure was replaced by full-grain ash and its color turned to light brown; (ii) as the ash addition ratio increased 10–90% in fly ash cement mixtures, thermal conductivity coefficient and compressive strength values decreased in the rates of 14.47–24.52% and 1.25–9.4% respectively; (iii) concrete or plaster turned into an insulator due to fly ash.

Energy, exergy and economics analysis of an ORC working with several fluids and utilizes smelting furnace gases as heat source

Abstract: It is necessary to improve efficiency of energy systems due to lack of fossil fuels in near future and their environmental issues. Waste heat of industrial activities can be recovered in order to enhance the efficiency of the energy systems. Organic Rankine cycles (ORCs) are an appropriate option to recover heat from metal smelting furnaces. In this study, thermodynamic and economic analyses are conducted on an ORC working with the gases existing a metal smelting furnace by applying different working fluids. Effects of various parameters on the performance are investigated and the results are compared. Obtained results show that m-xylene, P-xylene and Ethylbenzene have higher net power output, higher efficiency and lower total cost compared with other investigated working fluids.

Energy and emission management of CCHPs with electric and thermal energy storage and electric vehicle

Abstract: The shortage of energy along with environmental issues call for Distributed Energy Resources (DERs) to be employed in recent distribution systems. In Microgrids (MGs), Combined Cooling, Heating and Power (CCHP) units, Electrical Energy Storages (EESs) that are Battery Energy Storage Systems (BESSs) and Plug-in Hybrid Electric Vehicles (PHEVs), and Thermal Energy Storages (TESs) as new technologies can enhance system efficiency, in addition to reducing energy cost and emissions if they are properly managed. In this paper, a multi-objective optimization algorithm is proposed to minimize energy cost and emissions in residential MGs with considering BESS and TES. In order to preserve system reliability during on-peak periods, the Demand Response (DR) program is also implemented using Time of Use (TOU) energy tariffs and reducible loads to change energy consumption patterns of consumers. As well, PHEVs as active electrical energy storages are considered as an alternative for EES in optimal energy and emissions management. To solve the proposed multi-objective method, the augmented ɛ-constraint, as one of powerful solution algorithms, is used to efficiently obtain the Pareto front solutions. Then, a fuzzy decision maker is used to pick up the best compromising solution. The proposed strategy is evaluated in several scenarios including with/without considering ESSs and TESs in cases of following thermal, electric, and hybrid loads. Results from case study confirms the effectiveness of the proposed method.

Numerical investigation of heat transfer enhancement using various nanofluids in hexagonal microchannel heat sink

Abstract: This paper describes the numerical modelling of heat transfer and fluid flow characteristics for various types of nanofluids and water passing through a microchannel heat sink (MCHS). The microchannel heat sink is of hexagonal shape, with a hydraulic diameter, Dh, of 170 µm. In consideration of cases under cooling and heating, the heat flux is fixed to qw = 500 kW/m2. Water was used as the base fluid for various nanoparticles—i.e., Al2O3, CuO, SiO2 and ZnO- with different volume fractions and nanoparticle diameters. The results implied that nanofluids enhance the thermal performance of the microchannel heat sink by increasing the pumping power. It was also discovered that Al2O3-water shows the lowest readings in dimensionless temperature and thermal resistance, while displaying the highest in heat transfer coefficient. Thermal performances of the MCHS can be increased with an increase in volume fraction and by applying smaller particular diameter but at the cost of pumping power and pressure, which would then diminish the overall favourable effects. Ultimately, Al2O3-water with 4% volume fraction and 25 nm nanoparticles diameter is the favoured nanofluid through microchannel heat sinks and can be adopted in next generation cooling devices.

Summer thermal performances of PCM-integrated insulation layers for light-weight building walls: Effect of orientation and melting point temperature

Abstract: Phase change materials (PCMs) as insulation layers constitute a novel application of this kind of heat storage materials, which could be profitably used in buildings for energy saving because they can shave the peak heating load during the day. PCMs exploit the capability of storing and releasing the latent heat of phase change with minor or even no variation of temperature. In this condition, they show an apparent increase of their thermal capacity, per unit of mass or volume, which can be particularly useful in lightweight walls. This paper deals with the effect of solar radiation on a light-wall with PCM-integrated. In addition, a dynamic model of a wall is developed considering the different conditions such as position of PCM and different orientation of the wall. The results show that utilizing PCMs integrated insulation layers could provide major reductions of heat loads when their intensity is fluctuating and variable, and that this solution is more effective when the temperature variations are close to the phase change temperature, leading to energy savings up to 75% of the heat load through opaque walls.

A review of flow and heat transfer behaviour of nanofluids in micro channel heat sinks

Abstract: The nanofluids have increased interest in many engineering fields due to its excellent thermophysical properties, which can be easily used in microchannel heat sinks by many roles for performance improvement. The purpose of this review summarizes the important published articles on the enhancement of the convective heat transfer in microchannel heat sinks using nanofluids. Numerous studies have been done to find the effect of different nanofluids flow through micro channel heat sinks on thermal performance. In this work a comparative study is also carried out to select be micro channel heat sink shapes for maximum heat transfer and minimum friction losses.

A review on the current research and application of wastewater source heat pumps in China

Abstract: Wastewater source heat pumps (WWSHPs) have become increasingly popular in many countries due to their advantages of relatively higher energy utilization efficiency and environmental protection. As concluded in literature (Hepbasli et al., 2014) that “the location where the majority of the studies are conducted is China”, but many research results were published in Chinese only. Therefore, the current research and application of WWSHP systems in China or published in Chinese are reviewed in this paper in terms of current projects, challenges, and opportunities of WWSHPs to the best of our knowledge. The WWSHP projects are reviewed first. Next, challenges in the applications of WWSHPs and related studies are presented, including foulant contained in wastewater, fouling deposited on the heat transfer surface, flow and heat transfer characteristics of wastewater, and its temperature and amount. Afterward, the opportunity of WWSHPs is discussed through reviewing the development of special devices and heat exchangers of WWSHPs and the economic benefits. Finally, some concluding remarks are drawn from the review. It is expected that the study in this paper will supplement the knowledge of WWSHPs and provide reference data to the WWSHP researchers all over the world.

A comprehensive study of an atmospheric water generator using Peltier effect

Abstract: A prototype of a small-scale atmospheric water generator (AWG) that employs the Peltier effect for cooling was designed and constructed. In this study, a systematic design approach was employed, and the AWG system was sized using the cooling capacity and coefficient of performance (COP) behaviors of the thermoelectric cooler (TEC) with respect to the current. Likewise, a mathematical model that uses the surrounding fluid temperature and relative humidity ratio as the driving force for heat and mass transfer was used to optimize and design the rectangular extended surfaces and estimate the water generation rates. The completed AWG system, housed in a 3D printed casing, was used to experimentally investigate the impact of the variation of the airflow velocity, humidity, and TEC current on the water generation rates. The experiments confirm that the inclusion of an intake fan reduces water generation in some cases. The water yield is observed to increase with relative humidity. The tests also suggest that increasing the current of the individual TECs results in an increased water generation rate; however, this increase is coupled with a higher specific energy consumption as a result of the decreased COP. Finally, a comparison between the prototype and several AWGs in literature was carried out.

Investigation of the effect on the efficiency of phase change material placed in solar collector tank

Abstract: In parallel with the increase in population, natural energy resources on earth started to run out. And this brought along tendency to new energy resources. Therefore, studies on new and renewable energy resources became intensified and especially researches about solar power as the most important renewable energy resource gained intensity. In this study, tank with latent heat storage in combination with hot water collector was designed and tests were held under Elazig climatic conditions. Thermal efficiencies obtained from collector system were compared to the efficiencies of a standard insulated tank. In accordance with this purpose the results of the tests, held on certain days in July-November, were commented. The highest thermal efficiency value in the study was obtained as 58% in July around hour 13:30 from the tank in which phase change material (PCM) was used.

Experimental investigation on the Effect of Using Nano fluid (Al 2 O 3 - Water) on the Performance of PV/T System

Abstract: In the following, a work was conducted to evaluate the performance of PV/T system when using Nano fluid as working fluid. The used Nano fluid consists of Al2O3 50 nm suspended in water as base fluid. Firstly, Tests were performed with different flow rates of water as a cooling agent, and then volume concentrations ratios (0.05, 0.075, 0.1, 0.2, .03) were used as a working fluid at the highest flow rate. The results showed that using Nano fluid increases the combined performance of PV/T by 74 and 56% at volume concentration 0.1% V Concentration. The optimum flow rates achieved in the experiment was 1.2 l/mini. Finally using Nano fluid increases the efficiency of PV/T system significantly.

Numerical and experimental investigation of heat transfer in liquid cooling serpentine mini-channel heat sink with different new configuration models

Abstract: Cooling of electronic chips has become a basic viewpoint in the advancement of electronic devices. Overheating may cause glitch or harm to hardware. A water-cooled mini-channel is a successful cooling innovation for cooling of heat sinks. In this work, geometric optimisation of a 3D serpentine mini-channel heat sink (SMCHS) was investigated. Four configurations of SMCHS were proposed. These configurations were then simulated numerically and tested experimentally. Finite volume method computational fluid dynamics technique is used to model single-phase forced convection for water-cooling laminar flow in a 3D mini-channel heat sink with various channel configurations. Experiments were conducted to analyse the effect of water mass flow rate and heat load on thermal and hydraulic performances of the SMCHS. Experimental results agree well with numerical results. Results indicate that the performance of the proposed device effectively improves when serpentines with two inlets and two outlets are used compared with conventional serpentine with one inlet and one outlet.

Energy performances and numerical investigation of solid-state magnetocaloric materials used as refrigerant in an active magnetic regenerator

Abstract: Magnetic is the most diffused, developed and evolved technique among solid-state cooling, a class of ecofriendly refrigeration systems employing solid-state caloric materials. Active Magnetic Regenerative refrigeration cycle (AMR), a Brayton based thermodynamical cycle, is the benchmark cycle for magnetic refrigeration. This paper aims to provide a map of energetic performances of an Active Magnetic Refrigerator by the development of a two-dimensional numerical model, whom replies the behaviour of one of the regenerators mounted in 8Mag, the experimental prototype of the first Italian Rotary Permanent Magnet Magnetic Refrigerator (RPMMR), mounting gadolinium. To this hope, through the model a performance map has been delineated and it has been investigated the behaviour of the AMR regenerator, mounting gadolinium, in order to explore the limit conditions of prototype working, in terms of cold-hot heat exchanger range, fluid flow rate and frequency. In a second step, the performance map has been extended to other MCE materials, possible candidates for magnetic refrigeration at room temperature.

Energetic, exergetic and financial evaluation of a solar driven trigeneration system

Abstract: The objective of this work is to investigate a solar driven trigeneration system by the energetic, exergetic and financial point of view. Parabolic trough collectors coupled to a storage tank are used in order to feed an Organic Rankine Cycle which rejects heat to an absorption heat pump. The system is optimized using both exergy and energy criteria. The optimization parameters are the heat source temperature in the inlet of the heat recovery system, the pressure in the turbine inlet and the heat rejection temperature of the organic Rankine cycle to the absorption chiller. Toluene, n-octane, MDM and cyclohexane are the examined organic working fluids with toluene to be the most suitable choice according to the conducted multi-objective optimization procedure. The next step is the dynamic simulation of the optimum system design for all the year period. This optimum system is also evaluated financially. According to the final results, the yearly operation of the optimum system leads to heating, cooling and electricity production equal to 995 kWh, 232 kWh and 154 kWh respectively. The payback period was found 5.33 years and the internal rate of return 20.02%, values which indicate a viable system. The analysis is performed with a developed thermodynamic model in Engineering Equation Solver.

Flexibility assessment of a combined heat-power system (CHP) with energy storage under real-time energy price market framework

Abstract: The use of on-site generation can significantly enhance the primary energy savings of a building while acting as a hedge against rising electricity prices. Among other techniques, combined heat and power systems have proved to be reliable and economically suitable technologies in building applications and provision for their promotion has been set out by the European Union over the last few years. Moreover, demand side management programs can provide additional revenue streams which can further benefit the feasibility of combined heat and power technology in a commercial building while providing services to the grid network. In this context, the aim of the present paper is to investigate the techno-economic performance and energy flexibility potential for demand response programs of a gas turbine combined heat and power unit with thermal and electrical storage in commercial buildings. A short assessment overview on demand side management and demand response programs, with a special focus on combined heat and power systems, is provided to introduce the main aspects of these initiatives. Combined heat and power system, technical parameters and operating control strategies are investigated to determine their effects on system efficiencies and economics. Finally, real time pricing and energy storage are examined to establish the implications on a combined heat and power system in a demand-side management framework. Results show that savings of 7% can be obtained by the introduction of thermal energy storage systems, making them suitable for combined heat and power systems in building applications. Operating in a real-time market, the year-on-year savings associated with the combined heat and power are greater than when fixed rate tariffs are considered, especially with the electric energy storage system installed, since it allows the exploitation of price fluctuations. However, the current high investment cost of electric storage makes this solution economically unsuitable, leading to poorer combined heat and power economic performance.