Thermal performance enhancement of evacuated tube solar collector using MWCNT, Al2O3, and hybrid MWCNT/ Al2O3nanofluids

Nanofluids have numerous applications in heat transference procedures due to their exceptional thermal characteristics. The most desirable parameter to enhance the solar collector's performance is the enhancement of the convective heat transfer coefficient between the working fluid tubes and the absorber. As a result, nanofluids have gained prominence as working fluids in solar thermal systems. The trendsetting review reveals that mostly the nanofluids in solar collectors are based on water employing nanoparticles of Al2O3, TiO2, SiO2, and CuO. Besides, nanoparticle concentration is a challenging factor in using nanofluids. In this research, under controlled conditions, the working fluids multi-wall carbon nanotube, Aluminum Oxide, and hybrid MWCNT/Al2O3 50:50% were experimentally examined for the thermal efficiency enhancement of the evacuated tube solar collector. For each type of nanofluid, four volume concentration percentages (0.5%, 0.025%, 0.01%, and 0.005%) were examined along with three distinct mass flow rates. According to the findings, using hybrid MWCNT/Al2O3 50:50% delivers an efficiency boost of about 20% overusing Al2O3, as was previously reported. Finally, it was found that the utilization of 0.5% MWCNT/water nanofluid at 3.5 L/m can enhance the ETSC's energy and exergy efficiency to reach 73.5% and 51% respectively while reaching approximately 60% and 44% for AL2O3, and 69% and 38% for hybrid MWCNT/Al2O3 (50:50%) under the same test conditions

Accelerated cooling of steel rebars establishment of technological and design parameters of the cooling unit by modelling and experimentation

The aim of this work is to develop a computer mathematical model that could be used to predict the design parameters of an accelerated cooling unit. These parameters include length and diameter of cooling tube, size, number and type of nozzles and amount of water needed. Such units are encorporated at the end of or before the last rolling mill of re-inforcing bars for the production of high strength steel re-bars. The production of high strength steel rebars from ordinary 0.2% C - 0.8% Mn by thermo-mechanical treating has been widely employed recently. The control of the cooling rates through the water flow (cross sectional area of tube and amount of water) and cooling time (length of unit which varies according to the rolling speed) affects the process greatly. The bars that leave the stand at about1000°C, are cooled in a long tube with high pressure water. The outer surface cools to about 200-400°Cforming a martensftic layer, while the inner areas remain hot (1000°C). Then both surface and core temperatures equalise at a certain temperature which greatly affects the strength of the cooled rebars. It is of great importance to be able to predict this temperature and previously mentioned design parameters to be able to build the cooling unit required to achieve certain strength levels. The results of the model have been used to develop a cooling unit at El-Ahlya National Company. The performance of the unit was verified experimentally, where several experiments were carried out for different bar diameters, in the range 12-16 mm, and various cooling conditions leading to different bar equalising temperatures.Strength values in the range from 430 to 1500 MPa were obtained by changing cooling conditions. The obtained mechanical properties after cooling were compared with the predicted equalising temperatures. Also, the microstructures of the cooled bars were compared with those predicted by the cooling curves obtained from the mathematical model results. The results obtained from the model predicted to great proximfty the experimentally obtained results

Guidelines for data collection on energy performance of higher-education buildings in Egypt: a case study

Reliable energy analysis of buildings relies heavily on high-quality data leading to proper indicators. Previous studies have highlighted the importance of data quality in analyzing energy usage in residential and non-residential buildings in order to transform declarations to actions, optimise energy efficiency policies and monitor progress and failures in countries. Collected data must adhere to national and international standards for energy performance in buildings. This study aims to provide practical guidelines for effectively collecting and preparing data suitable for evaluating energy performance in Egyptian higher-education (HE) buildings. The guidelines are developed based on a comprehensive case study, considering data availability in typical educational facilities. Architectural and civil engineering drawings, construction specifications, and occupancy details are accessible. However, actual monthly electrical and natural gas consumption data for individual buildings are lacking. To address this, the study proposes the creation of detailed datasheets for each building, encompassing all energy sources and their electrical and power specifications, such as equipment, machinery, and HVAC systems. These datasheets were utilized to calculate energy consumption and energy usage indicators (EUI). The findings demonstrate that the datasheets enable adequate assessment of energy usage in various spaces within educational buildings, including staff rooms, lecture halls, and laboratories. This facilitates the identification of areas in need of targeted energy efficiency improvements. Notably, the study reveals that electricity consumption in the Faculty of Engineering building is significantly influenced by PCs, laboratories, lighting, and air conditioning

Maraging steels for cast tooling

SIGLEAvailable from British Library Document Supply Centre- DSC:D73634/87 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Optimization of plastic waste integration in cement bricks

Abstract Implementing plastic waste in construction materials is a sustainable disposal method to overcome plastic pollution. The current study aims to optimize the integration of plastic waste in cement bricks regarding their thermomechanical properties in order to develop an eco-friendly building material. Polyethylene terephthalate (PET) and high-density polyethylene (HDPE) partially substituted cement with different ratios (0, 2.5, 5, 7.5, 10, 20%). The type that achieved better thermomechanical performance further replaced the other brick components; sand and coarse aggregates to determine the optimum replacement scenario and best design mix. Laboratory experiments have been carried out to measure the compressive strength, indirect tensile strength, bulk density, and thermal conductivity of the new composites. The measured results revealed better performance for the samples with HDPE than PET. A boost in the compressive strength and indirect tensile strength was noticed for the samples obtaining a limited amount (up to 7.5%) of HDPE. However, a reduction in the tested mechanical properties occurs with higher substitution levels. With respect to thermal conductivity and bulk density, they decreased with the increase of plastic waste. The best mechanical behavior and the highest thermal resistance were obtained by partial replacement of coarse aggregates with 7.5% and 20% HDPE respectively. The results represent a good contribution to energy conservation, waste management and sustainability

Assessment of lateral and vertical tissue displacement obtained by the retraction cord and diode laser: A randomized controlled clinical trial

This study was carried out to compare between two techniques of gingival retraction (retraction cord and diode laser) regarding the amount of tissue displacement both laterally and vertically. Also, Patient satisfaction during their application. Methodology: twenty two cases requiring full coverage porcelain fused to metal fixed prosthesis in the anterior esthetic zone were taken from the outpatient clinic of the fixed prosthodontics department – Cairo University. The teeth were prepared with subgingival deep chamfer finish line and were distributed according to the technique of gingival retraction. Group I: Patients receiving retraction with the retraction cord. Group II: Patients receiving retraction with diode laser. In both groups measurement of lateral and vertical displacement done by using the stereomicroscope. also, patient satisfaction was measured by Comley and Demeyer numeric pain scale. There was significant difference between the two groups regarding lateral and vertical displacement. Laser troughing give not only more amount of vertical but also more lateral retraction whereas, P<0.05. For the patient satisfaction there was a significant difference between both groups, with laser troughing give better results.&nbsp