Rheology Characteristics and Critical Velocity of Particle-laden Flow Affected by Three-lobed Spiral Pipe

The use of piping systems for fluid transportation is increasing because it is considered the most effective method. Newtonian and non-Newtonian fluid flows are suitable for piping systems, and non-Newtonian, particle-laden fluids are more complex due to various factors. Deposition is one of the problems that must continue to be investigated because of the effects of flow efficiency. The purpose of this study was to investigate the performance of the three-lobe spiral pipe effect. Working fluids in several variations of concentration weight (Cw 20%, 30%, and 40%) were used. Test pipe with a length of 1550 mm and consisting of spiral pipe P/Di = 7 and a circular pipe with an inner diameter of 25.4 mm were used. The circular pipe was used to investigate the rheological workings of fluid. Both pipes were used to investigate the particle effects. Using scanning electron microscopy, 1-?m to 5-?m slurry particles were obtained from the mud eruption source at Semau Island, Kupang, Indonesia. The critical velocity value of the spiral pipe was lower than the circular pipe, so the spiral pipe is highly effective for slurry transportation

Effects of two-phase flow friction factor correlations on the optimal pressure drop-martinelli parameter pair in a mini-channel

Substantial research has been completed with more on-going on the flow pattern and heat transfer associated with two-phase flows. Discrepancies reported may have been as much as agreements, due to the different models, approaches, flow regimes, correlations, and new working fluids being utilized. This paper reports the outcome of a study to look at the effects of applying two different friction factor correlations on the simultaneous minimization of the pressure drop and Martinelli parameter under optimized flow rate and vapor quality, using genetic algorithm. The homogeneous model is assumed with ammonia as the working fluid, the coolant being environmentally friendly and having recently discovered as a potential replacement for the current refrigerants in micro and mini-channels. Results show that significant differences in the frictional pressure drop and Martinelli parameter arise due to the different correlations used, and this is only the outcome from two different correlations currently being considered by researchers in pressure drop analysis for two-phase flows in mini-channels. Thus, absolute agreement is indeed not possible between theoretical, experimental, and numerical work in view of the many different available correlations being utilized today with differences between 10 to 100 percent that has already been established

Heat Transfer Coefficient Characteristic Study of Natural Refrigerant with Substitute for R-134a

The wide-spread use of halocarbon refrigerants are making negative impact on Earth. Natural Refrigerant, such as hydrocarbon, is one alternative of several option to use. Mixing hydrocarbon are develop to improve the heat transfer characteristic. For example is, Musicool-134 (MC-134) is a mixture with two major substance of propane and iso-butane. The experimental apparatus is using a microchannel with a diameter of 0.5 mm and length of 0.5 m. The evaporative process was conducted in the experiment. The result of the experiment is that if the high coefficient value then the heat flux value is also high

Characteristics of two-phase flow heat transfer of R-22 and R-290 in horizontal circular small tube

Hydrocarbon refrigerants have been widely used to replace HFCs. As hydrocarbon, R- 290 has no ODP (Ozone Depletion Potential) and negligible GWP (Global Warming Potential). This paper presents flow boiling heat transfer in small tube with R-290 and R-22. The test tube has inner diameter of 7.6 mm and length of 1.07 m. In order to determine the heat transfer coefficient, experiments were carried out for heat fluxes ranging from 10 to 25 kW/m2K, mass fluxes ranging from 204 to 628 kg/m2s, and saturation temperatures ranging from 1.87 to 11.9o C. The study analyzed the heat transfer through the local heat transfer coefficient along the flow under the variation of these different parameters. In comparison with R-22, R-290 provides higher heat transfer coefficients. In the prediction of the heat transfer coefficients of R-22 and R-290, the correlation of Shah (1982) and Choi et.al. (2009) best fitted the present experimental result, respectively

Thermofluids on Renewable Energy, Refrigeration and Air Conditioning, and Flame and Combustion

Increasingly limited sources of fossil energy are driving people to seek alternative energy resources. The use of photovoltaic (PV) and biogas for electric power generation continues to be accompanied by efforts to improve their system performance. Electrical ratings on PV systems, and the design of the digester in the biogas combustion process, are two of the relevant issues presented in this edition. Absorption cooling systems for buildings with solar power is one type of environmentally friendly system. In addition, the use of the natural refrigerant propane and a small channel can provide a higher heat transfer coefficient. In the heating and cooling process, the heat transfer characteristics are changed due to the phase change of the working fluids or material. Therefore, research on phase change material or working fluids has become an important way to support energy savings. Adsorption cooling systems that work with certain materials have shown better system performance, are environmentally friendly, and are energy-saving. System performance is determined by the properties of the material or the working fluid; it can be improved by modifying the serial or parallel stages of the process, which can be implemented in the dehumidification process. The pyrolysis process is another example of an application of thermofluids that uses flame and combustion; here, a carbonaceous solid is thermally degraded via heat in the absence of oxygen. For safety in flame and combustion, controlling the oxygen concentration can reduce the propensity for ignition and lower the fire propagation rate. Related applications on the engine and controlling the conditions of combustion in the engine room can improve engine performance

The influences of diversity hull shapes and outriggers arrangement in pentamaran systems

The wave flow pattern builds up along the hull and expansion flow behind the hull is absorbing the energy from the ship as a resistance. The ship's resistance and the behaviour of its components are significant in estimating the propulsion of the ship, which positively influences fuel consumption. The aimed of this work was investigating the influence of two hull forms and its outriggers arrangement in pentamaran systems. The investigating was in wave resistance, interference, and far-field wave spectrum. This study focused on warp-chine and Wigley hull shapes by comparing a computation which was based on Michell's thin ship theory and various tests in clearance and stagger of side hulls. The results of this study founded the resistance coefficients based on Michell's approach agreed with towing test results at Fn > 0.5. Besides, wave resistance for warp-chine configurations was established to be much better than Wigley except at Fn < 0.5. High coefficient reduction for warp-chine hulls was generated with a setting where the main hull to side hull on a formation as an arrow trimaran near to Kelvin angle. As for Wigley, the high reduction was produced by a configuration where the front-side hull and the stern-side hull were in line. Then, captured wave patterns of the towing test exhibited a fit visual with the computation, in which Wigley hulls produced a more significant wave than warp-chine hulls

Improvement of two-phase heat transfer correlation superposition type for propane by genetic algorithm

The prediction accuracies of the two-phase heat transfer coefficient for the flow in a small channel, which are usually based on the mean absolute error (MAE) between the correlation and experimental data, have remained unsatisfactory. Conventionally, the regression method has been used to determine the correlation that best represents the experimental data. In this paper, an improved heat transfer correlation for the evaporation of propane is developed by applying the genetic algorithm method. A total of 789 data points from 4 sources with circular diameters ranging from 1.0 to 6.0 mm are used to minimise the MAE while searching for the optimum conditions for the suppression factor, S, and convective factor, F, in a selected superposition correlation for two different vapour quality ranges. The optimisation can minimise the MAE at 33% and 25% for Case I and Case II, respectively. The proposed method assists in attaining a precise empirical prediction that fits well with the experimental data

Prediction of the heat transfer coefficient in a small channel with the superposition and asymptotic correlations

Heat transfer coefficient as an important characteristic in heat exchanger design is determined by the correlation developed from previous experimental work or accumulation of published data. Although discrepancies still exist between the existing correlations and practical data, several researchers claimed theirs as a generalized heat transfer correlation. Through optimization method, this study predicts the heat transfer coefficient of two-phase flow of propane in a small channel at the saturation temperature of 10°C using two categories of correlation - superposition and asymptotic. Both methods consist of the contribution of nucleate boiling and forced convective heat transfer, the mechanisms that contribute to the total two-phase heat transfer coefficient, which become as two objective functions to be maximized. The optimization of experimental parameters of heat flux, mass flux, channel diameter and vapor quality is done by using genetic algorithm within a range of 5-20kW/m2, 100-250kg/m2s, 1.5-3mm and 0.009-0.99, respectively. In the result, the selected correlations under optimized condition agreed on the dominant mechanism at low and high vapor qualities are caused by the nucleate boiling and forced convective heat transfer, respectively. The optimization work served as an alternative approach in identifying optimized parameters from different correlations to achieve high heat transfer coefficient by giving a fast prediction of parameter range, particularly for the investigation of any new refrigerant. In parallel with some experimental works, a quick prediction is possible to reduce time and cost. From the four selected generalized correlations, Bertsch et al. show the closer trend with the reference experimental work until vapor quality of 0.6

Drying kinetics of Indonesian peat

Indonesia has the largest peatland area in the tropical region, situated mainly in Sumatra, Kalimantan and Papua. Peat is an organic substance which is highly combustible in dry conditions; dried peat can burn easily and spread vertically and laterally along peat layers. In Indonesia, peat fires have often occurred in recent decades. Besides being influenced by the amount of organic content, smoldering peat fires are also effected by the drying rate, pyrolysis, and heterogeneous oxidation on the peat surfaces. In contrast to flaming combustion, which have been widely studied, smoldering peat fires remain little understood. To date, the major peat fire-related publications concern the pyrolysis and combustion stages. The contribution of the drying kinetics of peat in the peat fire phenomenon is important, as this could provide complete understanding of the peat fire process. The objective of this paper is to make an isothermal drying kinetics analysis of peat. Peat samples were taken from various locations in Indonesia with the largest peat distribution, namely South Sumatra, Central Kalimantan and Papua. An isothermal test was conducted using a Shimadzu MOC63u Moisture Balance. At certain interval times, the weight of the specimen was measured, until it reached a constant weight of less than a 0.05% change in moisture content. Isothermal analysis was conducted for each peat sample at temperatures of 60, 70, 80, 90, 100, and 110oC. The results show that the activation energies from the isothermal measurement test were 24.97, 25.08, and 30.11 kJ/mole for Papuan, South Sumatran and Central Kalimantan peat, respectively