Modeling and Analysis of Fouling Behaviour in Plate and Frame Heat Exchanger

The fouling of heat exchangers in the oil and gas industry is not only a recurring challenge in refineries but it is also becoming a challenge in crude oil production and treatment facilities where heat exchangers are deployed to cool the crude oil temperature downstream of stabilization system prior to storage. A predictive mitigation approach to addressing fouling in heat exchangers remains the most viable option to avoid production train capacity limitations, unplanned shutdown and attendant loss of revenue. Considerable researches have been carried out which lead to the development of models used for predicting fouling resistances in shell and tube heat exchangers. However, this study focused on evaluation of the performance of a plate and frame heat exchanger utilized in cooling of crude oil prior to storage in a cargo tank for export. It also developed a fouling resistance suitable for forecasting the exchanger performance and predicting the maintenance management scheme. The data employed were continuously measured for three years and employed for the analysis.  It found that the lower the hot stream approach temperature, the more the fouling resistance. In addition, the work validates that as the fouling resistance increases with time, the efficiency of the plate and frame heat exchanger diminishes

Development of a Multi Agricultural Products Dryer using Biomass

Natural method of sun drying is weather dependent and time consuming which leads to spoilage and contamination of food crops. This research designed and experimentally tested a multi agricultural dryer using solar energy and biomass, capable of drying agricultural produce anytime of the day in a hygiene environment. The experimental setup consists of the biomass combustion chamber with inbuilt heat exchanger, the dryer and data collection instruments. Tomatoes, Okra and bitter leaf were dried, their relative humidity, moisture content, weight loss and temperature variation in the drying chamber were monitored. The maximum temperature reached in the drying chamber when drying tomato, okra and bitter leaf were 95.7oC, 87.1oC 73.4oC respectively, with a drying rate of 0.1248 kg/h, 0.1876 kg/h, 0.0780 kg/h, respectively at a steady air flow rate of 1.3 m/s. The dryer had an efficiency of 45% and effectiveness of the heat exchanger is 0.077 at an average combustion temperature of 1300oC. The uniqueness of the machine is that it reduces the drying time and products are free from environment contaminations and rodents’ invasion. Thus agricultural crop samples can be preserved year-round irrespective of weather conditions and at a faster rate with the developed machine

Potential of mucilage-based hydrogel for passive cooling technology: Mucilage extraction techniques and elucidation of thermal, mechanical and physiochemical properties of mucilage-based hydrogel

Current air-conditioning and refrigeration systems utilize active cooling technology, which consumes a lot of energy from fossil fuels, thereby increasing global warming and depletion of the ozone layer. Passive cooling is considered an alternative to active cooling because it is effective and less expensive and does not require the use of electricity, so cooling can be achieved in locations where there is no electricity. Hydrogels are flexible and soft 3-dimensional networks with high water content and evaporative and radiative cooling properties that make them suitable for use in passive cooling technology. Natural hydrogels are considered alternatives to synthetic hydrogels because they are biodegradable, biocompatible, sensitive to external environments and mostly sourced from plant-based sources. There are limited studies on the application of mucilage-based hydrogel for passive cooling, despite its excellent thermal, mechanical and physiochemical properties. Therefore, this study evaluates the properties of mucilage-based hydrogel as a plausible alternative to synthetic hydrogel for passive cooling. The possibility of using mucilage-based hydrogel in passive cooling technology depends on the mucilage biomass feedstock, mucilage extraction techniques, polymerization techniques and additives introduced into the hydrogel matrix. Different mucilage extraction techniques; mucilage percentage yield; the effects of crosslinkers, polymers and nanoparticle additives on the properties of mucilage-based hydrogel; and the potential of using mucilage-based hydrogel for passive cooling technology are examined in this review

Experimental Investigation and FE Simulation of the Effect of Variable Control on Temperature Distribution in Orthogonal Metal Cutting Process

The study aimed at building a 3-Dimensional finite element simulation to monitor orthogonal machining process under a dry machining environment. The study was conducted in two stages of experimentation and finite element modelling and simulation (FEMS). The purpose of the experimentation was to obtain data which will be used to validate the FEMS result. The FEMS was carried out with a commercially available solver. The workpiece material employed for the study was mild steel in the form of round bar of solid shaft having 45 mm diameter and length of 500 mm. Mild steel was selected due to its wide range of applications in the fields of manufacturing tools and mould industry. The tool material used was tungsten carbide of DIN4980R 20 mm x 20 mm, with cutting angle of 80-degree tool steel, which was modelled in the FEMS as a rigid body. Various cutting conditions such as speed, feed rate and depth of cut were considered to obtain the tool chip temperature. Different values of temperature were recorded at interval of 10 seconds and ranged from 10 to 100 seconds. The FEMS was carried out by making one of the conditions vary while the others were constant. The temperature values measured with a digital thermocouple were used to validate the FEMS data obtained. The result show that the cutting temperature predicted by the FEMS is within 20% of the real experimental value and followed the same trend. It was discovered that the values of temperature obtained from simulation were also much higher than that of experimentation. Therefore, the experimental value might not be accurate, due to some experimental errors and environmental effects like partial contact between the measuring device and the cutting tools, fluctuation in the magnitude of air flow around the surrounding which may affect the cutting temperature, room temperature and pressure effect. Generally, with an increase in the cutting speed, feed rate and depth of cut, the tool temperature also increased and the cutting speed was found to be the most effective parameter when consideration is given to temperature effects, especially in high range of cutting conditions

Development of Thermomechanical Model for the Analysis of Effects of Friction and Cutting Speed on Temperature Distribution around AISI 316L During Orthogonal Machining

In metal cutting,severe deformation takes place in the vicinity of the cutting edge of the high strain-rate and an increase in temperature is observed. Deformation behaviour of the work material in the primary and secondary zones is highly sensitive to the cutting conditions. Also, the frictional conditions between the tool and the chip and tool and the workpiece are highly complex and sensitive to the cutting conditions. As a result, the stresses and temperatures at tool-chip interface and around the cutting edge can be critically high in some cutting conditions and can cause excessive tool wear or premature tool failure. This research work focuses on the accurate prediction of the distribution of the process variables such as stresses and temperatures with the Finite Element (FE) Analysis to identify optimum cutting conditions, tool material, edge geometry and coating in order to help improve productivity and quality of machining operations. Effects of work material flow stress and interfacial friction at chip-tool interface on the accuracy of the predicated process variables in FE simulations are also analyzed. Specifically, friction models and cutting speed are varied to predict the effect on the temperature distribution, stresses and strain on the workpiece and tool chip during orthogonal cutting process. The result showed that an increase in coefficient of friction will cause an increase in thermal, force and mechanical variables during machining. Thus, the higher the coefficient of friction, the higher, the cutting forces, temperature, stress, and strain

Modelling and Control of Flow Induced Vibration of Top–Tensioned Marine Risers Using Analytical Methods

For a riser array in deep waters, interference between individual risers in strong ocean current is of operational concern and thereby a key design issue. The lateral deflection is likely to be large, and the risers may experience collision with fatigue or coating damage as a consequence. In this paper, active control of flexible marine riser angle and the reduction of flow induced (forced) vibration under a time varying distributed load were considered using boundary control approach. A torque actuator was introduced in the upper riser package and a boundary control was designed to generate the required signal for riser angle control and vibration reduction with guaranteed closed-loop stability. The design is based on the partial differential equations of the system, which are developed using energy principle. Analytical method of solution was deployed with the aid of a program, developed within the framework of MATLAB, to predict the riser's behaviour by top tensioning. A sensitivity analysis for different values of the control variables was carried out. The results of this work showed that active control of flexible marine riser by top-tensioning reduced flow induced vibration

Thermophysical Properties of Gmelina Arborea Biodiesel

The depletion of petroleum reserves, rising cost of conventional fuels and the ill effect of emission from the use of fossil fuel on human health and environment have driven scientific research towards the development of alternative source of fuels such as biofuel and biodiesel. Biodiesel is a fuel from a renewable sources and it has the potential of being used as an alternative to fossil diesel in compression ignition engine. Some of the challenges encountered in the use of biodiesel in compression ignition engine are its availability, use of edible oil for its production, cost of biodiesel feedstock and unfavorable properties of biodiesel such as its high viscosity. Presently, there is a search for more inedible oil seeds since the available inedible feedstock are still not enough to replace more than 20 - 25% of the total transportation fuels. The thermophysical properties of the biodiesel which vary from feedstock have a significant impact on the combustion process thereby affecting the overall engine performance and emissions. The aim of this study is to test the compatibility of biodiesel from Gmelina arborea seed oil in the compression ignition engine through its thermophysical properties. The biodiesel was produced using transesterification method and the thermophysical properties tests were carried out. The results showed that the density and viscosity of Gmelina arborea seed oil was 868.8 kg/m2 (at 27.5°C) and 1.882(mm)2/s (at 40.0°C) respectively. It also showed that the biodiesel obtained had a density and viscosity value of 821.2 kg/m3 (at 27.5°C) and 0.794 9 (mm)2/s (at 40.0°C) respectively. Comparing these results with other biodiesel, it was observed that Gmelina arborea oil has a lower viscosity and density than other biodiesel from different feedstocks; therefore it has potential to perform better in the diesel engine in comparison to other biodiesel

PERFORMANCE EVALUATION OF HOT AIR THERMOELECTRIC GENERATOR USING BIOMASS ENERGY SOURCE

Thermoelectric generators are solid-state devices that convert heat into electricity using the Seebeck effect, when there is a temperature difference across a thermoelectric material. This research designed an experimentally tested a thermoelectric hot air generator using sixteen SP1848-27145 modules in two parallel strings. The system consists of a biomass combustion chamber, hot air exhauster, hot and cold side heat exchangers. Voltage, current and temperatures in the combustion chamber, hot air heat exhauster, hot side heat exchanger and cold side heat sink were measured. The hot air exhauster, hot side heat sink and cold side maximum temperatures are 178.3°C, 69.2°C and 44.5°C respectively yielding an open circuit voltage of 64 V and current of 1.99 A in the course of the experiment. The thermal performance of the designed hot air exhauster, hot side heat exchanger and cold side heat were simulated using ANSYS Fluent, for pictorial representation of their temperature contours

CFD Analysis of Nanorefrigerant through Adiabatic Capillary Tube of Vapour Compression Refrigeration System

Over time attempts have been made to understand the flow characteristics of refrigerants through capillary tubes as well as to seek more thermally efficient working fluids for refrigeration systems. This study investigated the flow of nanorefrigerants through adiabatic capillary tubes of vapour compression refrigeration systems; and afterwards creates numerical models that will account for solution of refrigerant side pressure drop and mass flow rate. Also in this study, a CFD flow analysis was carried out using a CFD simulation/solver such that the results of the simulations obtained were discussed so as to establish a distinction between the conventional and nano-refrigerants. Upon comparison of the CFD results of nanorefrigerants (CuR134a, CuR600a) and the conventional refrigerants (R134a, R600a), the conventional refrigerants were noticed to have more isothermal regions implying that heat was not being transferred quickly enough to raise the temperature of the adjoining region thus proving that the addition of nanoparticles improves the thermophysical properties of the base fluid. Also, based on the results of the study of the flow patterns of both working fluids, the density of pressure contours in the conventional refrigerants was far larger than that of the nanorefrigerant implying that more compressor work and ultimately greater power will be required. The findings from this study were validated with experimental results showing that a CFD analysis tool/method can be employed to understudy the phenomenal changes that take place in nano-refrigerant movement through capillary tubes without recourse to experimentation