Energy Equipment and Systems
Volume:10 Issue: 3, Summer 2022

Drop motion on a solid surface has many applications in science and engineering, such as in architecture, offshore structures, and electronics. The present paper aims to simulate the motion of a water droplet located on a hydrophobic inclined surface and investigate its deformation rate using ANSYS FLUENT software. The sessile droplet subjected to uniform airflow can be shed depending on the value of drag and drop’s adhesion forces. In the present work, coupled level set and volume of fluid method are employed to estimate the motion of the interface. The effect of drop size, wind velocity, drop contact angle, and drop size on the location, velocity, and drop deformation is investigated. The results demonstrate that the drop is splashed as the contact angle decreases. The drop acceleration has an approximately constant trend at Reynolds numbers ranging from 8000 to 80,000. The maximum acceleration corresponds to the hydrophilic surface and is equal to 0.9 m/s2. As the contact angle increases, the acceleration becomes constant. For instance, the drop acceleration is about -0.3 for a contact angle of 135°. The results reveal that the drop requires a longer time to reach the lowest point of the inclined surface by decreasing its diameter and increasing surface hydrophobicity and wind velocity. It is found that as surface hydrophobicity increases, the drop reaches the bottom of the surface in a long time in comparison with the deformed drop.

Integrating MED-TVC unit with gas turbine cycle (GTC) and organic Rankine cycle (ORC) can be an effective way to take advantage of the hot exhaust gas of gas turbines. In this study, a multi-product system consisting of GTC, MED-TVC, and ORC is investigated. The energy and exergy analysis is carried out and influences some design variables such as inlet air temperature of air compressor, air compressor pressure ratio, high pressure in ORC, pinch point temperature difference, the pressure of motive steam, and TVC compression ratio on the developed system are examined. Calculation shows that the developed unit can produce 39.6 MW of power and 137.3 kg/s of fresh water with a gain output ratio of 4.41 and energy efficiency of 21.5%. According to the result, precooling the air at the entrance of the air compressor and decreasing the pinch point temperature can lead to enhancement exergy and energy efficiency of GTC and the gain output ratio of MED unit, respectively. In addition, the highest exergy destruction takes place in the combustion chamber and desalination unit.

The production of nanostructure materials or ultrafine grain (UFG) has been noticed by most of research society due to high strength, wear resistance, formability and high plastic strain rate. These features result from microstructure materials (100-300 nm) and unique defect (grain boundary-dislocation) make these material ideal for medical implant and structured components of aerospace and energy systems. The ways of producing UFG for these advanced engineering projects have not been considered yet. Due to the fact that nanostructured materials can show a good mechanical strength, researchers are using different ways to change pure copper into nanostructure one. One of these methods is applying process in equal channel angular pressing (ECAP), which coarse grain copper changed to nanostructure one. In this study, machinability of UFG as well as coarse grain (CG) copper is really considered in turning. To evaluate the machinability, cutting force, tool wear, chip morphology and surface roughness have been studied. Experimental results confirmed that UFG copper can be machined more efficiently than CG copper. In other words, the amount of BUE is reduced during turning ECAP copper due to the hardening of the pure sample. In comparison to CG copper, cutting force and surface roughness for UFG copper were less. As a result, machining performance can be improved partly by cold-work applying ECAP process.

In this study, a computational method for determining the contribution of each module in the output power of a photovoltaic power plant is presented and the results of that are compared with actual values. This method is based on infrared thermography. In other words, in this study, we are trying to develop a new model for analyzing the photovoltaic module thermography images through field measurements on several photovoltaic systems in Isfahan region. Since it is very important to precisely calculate the module surface temperature in this method, practical methods are presented to calculate the temperature accurately. Validation of these methods have been done by performing specific experiments. The results of this study show that for modules in which difference between maximum and minimum temperature in STC conditions is less than 10 °C and therefore classified in terms of temperature pattern in the healthy group, the calculation of power contribution of each module through this method is very close to the actual value ​​and have an error below 2.8%.

The wind turbine power transmission system exploits a planetary gearbox due to its large power transmission. In comparison with the common rotating systems, the wind turbine (WT) gearbox is assumed a complex system. Therefore, condition monitoring and fault detection isolation (FDI) of such systems are not straightforward and conventional signal processing methods (e.g. Fast Fourier transform) are not applicable or do not have an acceptable output accuracy. This paper proposes a new FDI approach for wind turbines based on vibration signals’ signatures derived from the multivariate empirical mode decomposition (MEMD) algorithm. Vibration signals are measured from a 750 kW planetary wind turbine gearbox on a dynamometer test rig provided by National Renewable Energy Laboratory (NREL).  In WT applications, to gather enough data with high accuracy and to avoid losing local information, multiple sensors must be utilized to collect data from different locations of the gearbox yielding a multi-sensory dataset. In standard EMD, joint information of multi-sensory data will be lost. Additionally, the intrinsic mode function (IMF) groups may not have the same characteristic features. To capture cross information of the dataset and to remove the effect of noise on the output results, a noise-assisted MEMD (NA-MEMD) algorithm is employed. Vibration signal features are also extracted by using discrete wavelet transform (DWT). Three major faults of the WT gearbox are detected using NA-MEMD and a comparison between NA-MEMD and DWT methods confirms the capability of the NA-MEMD method.

A comprehensive study was conducted on how different nano-fluids affect the heat transfer characteristics of a conical spiral duct with a square section. Metallic, non-metallic and Carbon nanotube (CNT) nanoparticles were assumed to be added to water as coolant in the spiral side of heat exchangers. The combined effects of nanoparticle dispersion and path curvature on heat transfer enhancement under two different thermal boundary conditions were investigated. The effects of the flow regime on heat transfer in such a configuration were tested. The flow and energy equations were solved numerically using available commercial software ANSYS FLUENT® Academic Research, Release 16.2. The numerical procedures were verified with available data, and correlation and maximum error were determined to be less than 13%. It was found that compared to the non- curved duct with the same length; heat transfer would increase by about 15%. The addition of metallic nanoparticles also enhanced the heat transfer by 5%. In low Reynolds numbers, crossflow affects temperature distribution and thermal characteristics but in the turbulent regime, the temperature distribution is less sensitive to generated crossflow.

In this study, the year-round thermal performance of a qanat source heat pump in supplying the required cooling and heating loads of a case study building is investigated. Using TRNSYS software, dynamic simulation of the proposed system is performed in three climate zones including Hot/Dry, Cold/Dry, and Hot/Humid. The heat pump and helical coil heat exchanger inside the qanat water are mathematically modeled in MATLAB, and then, coupled to TRNSYS model to evaluate the system transient performance. It is found that the free energy ratio of the qanat source heat pump Hot/Dry climate zone is on average 21.6% higher than compared to that of the air source heat pump. In cold months, by increasing the temperature of the inlet fluid to the helical coil heat exchanger inside the qanat, the system coefficient of performance increases 15%. The increase of the energy efficiency ratio of the system in the warm months is 7.7%. It is also found the highest coefficient of performance and the lower energy efficiency ratio of the system is obtained in the Hot/Humid climate zone in comparison with the other zones; so that, the energy efficiency ratio of the system in the Cold/Dry and Hot/Dry zones is 48% and 58% higher than that in the Hot/Humid zone, respectively. The annual FER of 63.4%, 63.1%, 56.8%, and 53.3% are obtained in Hot/Dry (Kerman), Cold/Dry (Mashhad), Hot/Dry (Tehran), and Hot/Humid (Bandar Abbas), respectively. These findings suggest that the building energy consumption significantly reduces using the QSHP in all climatic conditions.