Analysis of the microstructure and microhardness of rotary friction welded titanium (Ti‐6AL‐V4) rods

Abstract: This paper presents the evolution of mechanical properties in Ti6Al4V rods welded by rotary friction welding. This is evaluated by monitoring the microstructure and micro hardness changes resulting from the welding. 16 mm diameter Ti6Al4V rods were joined by rotary friction welding utilizing different process parameter settings, namely; axial force, rotational speed and upset distance. The microstructure and micro hardness analysis were observed on each of the weld zones/regions. The micro hardness results revealed higher hardness on the weld zone and low hardness on the heat‐affected zone when compared to the parent material. The higher axial force resulted in higher hardness in the weld zone because of more friction and hence higher heat input which led to refined microstructure. Microstructure characterization for the different weld zones due to varying process parameters is also discussed

Experimental investigation of water leakages through a longitudinal crack due to expansion of the pipe material under pressure

Abstract: The effect of the pipe material plays a preeminent role in the overall water leakage behaviour of cracks, and specifically of longitudinal cracks for pipes composing Water Distribution Systems. Due to pipe material properties, a longitudinal crack on a pipe exhibits expansion behaviour under internal pressure increases, taken up by hoop stresses, which cause high stress concentration around the crack, provoking the expansion of cracked areas. With the aim of assessing the increment of water leakages through longitudinal cracks, caused by pressure increase, in this paper results from experimental tests of a longitudinal crack on a pipe wall were analysed and discussed. This is achieved by subjecting several plates with different length of cracks to tension and monitoring the opening of the cracks. A mathematical model for longitudinal crack opening is derived using the orifice equation, as a function of pressure, pipe material properties, pipe geometry and fluid properties for uni-axial stress state. Subsequently, an equation describing the increase of the leakage flow rate as function of the increase of the crack area in uni-axial stress state is determined. The derived model (Ilunga’s Equation) contradicts the Torricelli’s orifice equation which assumed that the orifice area is fixed, but variable with the change in pressure due to pipe material properties

Coal combustion models: a review

Abstract : Computational Fluid Dynamics has been used for optimisation of industrial applications with some level of success. The modest accuracy provided by some of the combustion models in use has left some room for research and improvement. Coal is presented as a fuel with complex chemical properties due to its fossil fuel nature. The devolatilization process of coal is investigated with special attention to the best models that can handle heavy and light volatiles found in coal. The heterogenous char combustion is also presented paying attention to the nature of the char particle during the combustion process. The other processes such as drying, homogenous volatile combustion, radiation models, particle tracking models and turbulent models are investigated in a general manner as they rarely vary with the type of fuel being investigated. A summary of the industrial applications that have successfully utilised the CFD models for optimisation of coal combustion are presented thus helping in drawing the final conclusion

Comparative characterization of P91 and 10CrMo9-10 creep resistant steel welds

Abstract:Abstract: P91 and 10CrMo9-10 creep resistant steels are critical to the performance of boiler tubes and power generating plants in general. Components made from these materials are mainly joined by welding. This paper reports on the comparative study of the effect of TIG and SMAW welding on the mechanical performance of P91 and 10CrMo9-10. TIG was used for root welding while SMAW was used for weld filling of V-butt joints. Specimens of the two alloys prepared using recommended welding procedures are evaluated using optical microscopy and Vickers micro hardness assessment. Some specimens were post weld heat treated while others were not. Post weld heat treated (PWHT) specimens exhibited similar properties as the corresponding base materials for both steels. TIG welding resulted in significant grain size reduction in both steels. PWHT produced more consistent grain structure, which is favorable

Microstructural characterization of friction stir lap welds of aluminium incorporated with titanium carbide

In this research study, the characterization of the microstructure evolution of friction stir lap welds (FSLW) of Aluminium incorporated with Titanium Carbide powder to form Aluminium based composites is presented. The Titanium Carbide powder was infused at the weld interface to produce a composite. The FSLW were conducted on an Intelligent Stir Welding for Industry and Research (I-STIR) Process Development System (PDS). Different welding parameters were used for the welding process. Rotational speeds of 1600 rpm and 2000 rpm and transverse speeds of 100 mm/min, 200 mm/min and 300 mm/min were employed. The process parameters were carefully selected to represent a low, medium and high setting for the feed rates. The microstructural evolution of the samples were studied. Optical microscope and scanning electron microscopy (SEM) techniques were used to investigate the particle distribution of the welded samples. The results obtained revealed the influence of the welding parameters on the particle distribution of the welded samples. A homogenous mixture of the materials was observed at higher rotational speed of 2000 rpm

Comparison of experimental data and two clear sky models

Abstract: Solar energy is becoming a key player in manufacturing especially for off-grid applications such as community factories. Between the radiation emitted by the Sun and that absorbed on Earth, different phenomena take place. Many models were developed to tackle and explain these phenomena with varying levels of accuracy and complexity. Two commonly used models in most commercial simulation software such as ANSYS® Fluent® are the Fair Weather Condition and Theoretical Maximum Method. The aim of this paper is to investigate the accuracy of these models based on experimentally measured data. While these models assume a completely clear sky, the study is based on wet season. Global irradiance data acquired for different hours (9 o'clock, 12 o'clock and 15 o'clock) of the day was used. Results show good correlation between the average global irradiance for the Fair Weather Condition and the experimental values. The accuracy is more important for high solar elevation around 12 o’clock

Performance evaluation of a plate encapsulated salt hydrate PCM mixed with a gel

Abstract : An alternative method of cooling is required to meet cooling demands and simultaneously decrease conventional energy consumption. The current research aimed to investigate the feasibility of using a phase change material (PCM) in the form of a salt hydrate mixed with a CSIR-developed gel for PCM based cold storage that used nighttime cold to cool ambient air during the day. The experiments were conducted over a time period of three hours between 12:00 pm and 15:00 pm in the afternoon. The total temperature drops were found to be 3.8, 2.9 and 2.6 degrees for air flow rates of 0.03, 0.05 and 0.06kg/s respectively. The total energy transferred for each of the mass flow rates averaged 140.9, 144.4 and 158.9J for air flow rates of 0.03, 0.05 and 0.06kg/s respectively

Investigation of household refrigerator system with varied capillary tube length

Abstract : In this paper, the performance of R600a was investigated in a household refrigerator originally designed to work with R134a using varied capillary tube length (1.0, 1.15, 1.30 and 1.45 m). The refrigerator was instrumented with four thermocouples at the inlet and outlet of the major components. Also, two pressure gauges were connected to the compressor to measure the suction and discharge of the compressor. The experimental results were used to evaluate the performance of the system. The results showed that at optimal capillary tube length the COP and cooling capacity of R600a in the system increased with 45% and 4.2% respectively and the power consumption reduced with 25% using 1.30 m varied capillary tube length compared to R134a. Conclusively, R600a can serve as a retrofit in the household refrigerator systems originally designed to work with R134a refrigerant

COMPARATIVE ANALYSIS OF THE EXERGETIC PERFORMANCE OF A HOUSEHOLD REFRIGERATOR USING R134a AND R600a

The coefficient of performance (COP) and exergetic performance of a household refrigerator was investigated using R134a in comparison with the performance of R600a. The coefficient of performance, exergy efficiency, and the efficiency defect in the four major components were investigated. The results showed that the COP of R600a was 10.3% higher than that of R134a, a higher exergy efficiency of 42.8% was obtained using R600a at evaporator temperature of–10 C. Generally, R600a performed better than R134a in terms of COP, exergy efficiency, and the efficiency defect in a household refrigeration system

Dataset and ANN model prediction of performance of graphene nanolubricant with R600a in domestic refrigerator system

Abstract: This work evaluated the steady state performance of R600a in the base lubricant and graphene nanolubricant. The mea- suring instruments required and their uncertainties were provided, step by step method and procedures for prepara- tion of graphene nanolubricant concentration and substitut- ing it with the base lubricant in domestic refrigerator system are described. The system temperatures data was captured at the inlet and outlet of the system components. Also, the pressures data was recorded at the compressor inlet and out- let. The data was recorded for 3 h at 30 min interval at an ambient temperature of 27 °C. The experimental dataset, Ar- tificial Neural Network (ANN) training and testing dataset are provided. The artificial intelligence approach of ANN model to predict the performance of graphene nanolubricant in do- mestic refrigerator is explained. Also, the ANN model pre- diction statistical performance metrics such as Root Mean Square Error (RMSE) and Mean Absolute Deviation (MAD), Mean Absolute Percentage Error (MAPE) and coefficient of determination (R 2 ) are also provided. The data is useful to researchers in the field of refrigeration and energy efficiency materials, for replacing nanolubricant with the base lubricant