Transport Phenomena,
Volume 11, Issue 1 , January 2014, , Pages 63-68
Transport Phenomena,
Volume 10, Issue 1 , January 2013, , Pages 3-16
Transport Phenomena,
Volume 10, Issue 1 , January 2013, , Pages 55-66
Transport Phenomena,
Volume 10, Issue 1 , January 2013, , Pages 79-91
Process Control and Engineering, Process Safety, HSE
Volume 9, Issue 3 , July 2012, , Pages 55-62
Transport Phenomena,
Volume 9, Issue 2 , April 2012, , Pages 3-12
Transport Phenomena,
Volume 9, Issue 1 , January 2012, , Pages 23-32
Transport Phenomena,
Volume 9, Issue 1 , January 2012, , Pages 33-39
Transport Phenomena,
Volume 8, Issue 4 , October 2011, , Pages 43-49
Transport Phenomena,
Volume 8, Issue 3 , July 2011, , Pages 55-63
Transport Phenomena,
Volume 8, Issue 3 , July 2011, , Pages 64-77
Transport Phenomena,
Volume 8, Issue 2 , April 2011, , Pages 81-97
Transport Phenomena,
Volume 8, Issue 1 , January 2011, , Pages 38-45
Transport Phenomena,
Volume 7, Issue 4 , October 2010, , Pages 3-11
Transport Phenomena,
Volume 7, Issue 3 , July 2010, , Pages 61-73
Transport Phenomena,
Volume 7, Issue 3 , July 2010, , Pages 81-87
Transport Phenomena,
Volume 7, Issue 2 , April 2010, , Pages 17-27
Transport Phenomena,
Volume 7, Issue 1 , January 2010, , Pages 76-86
Transport Phenomena,
Volume 6, Issue 4 , October 2009, , Pages 3-14
Abstract
In the present study a mathematical model is developed in order to examine the effects of heat and mass transfers on removal efficiency of particulate matters in venturi type scrubbers. The governing equations including the variations of the particulate concentration, gas temperature, droplet temperature, ...
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In the present study a mathematical model is developed in order to examine the effects of heat and mass transfers on removal efficiency of particulate matters in venturi type scrubbers. The governing equations including the variations of the particulate concentration, gas temperature, droplet temperature, diameter, and velocity are obtained based on the conservation laws and are solved numerically. In order to validate the model, necessary data was measured and collected in a commercial cement plant that uses these types of scrubbers in air pollution control applications. A good agreement between plant data and the model predictions is noticed in general. The results obtained from the model reveal that the existance of temperature difference between the gas and the liquid droplets decreases the overall removal efficiency of particulate matters. This is due to sudden reduction ofrelative velocity between the gas and droplets which is resulted from the existence ofheat and mass transfers between the two fluids, especially in the throat section. In addition, the effects ofvarious operating parameters on the extent ofreduction in the removal efficiency are examined. This study confirms that in most industrial applications ofventuri scrubbers it is necessary to use a direct or an indirect cooling tower in order to decrease the gas temperature before entering the venturi.
Transport Phenomena,
Volume 6, Issue 4 , October 2009, , Pages 15-26
Abstract
This paper reports a study on the effect of the heat flux, cooling water flow rate, fill ratio and extra volume on the overall performance of a partially vacuumed thermosyphon. A rig was made from a 1 m copper tube with an inner and outer diameter of 17.5 and 19 mm. The heights of the evaporator, the ...
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This paper reports a study on the effect of the heat flux, cooling water flow rate, fill ratio and extra volume on the overall performance of a partially vacuumed thermosyphon. A rig was made from a 1 m copper tube with an inner and outer diameter of 17.5 and 19 mm. The heights of the evaporator, the adiabatic section and the condenser are 40, 20 and 40 cm, respectively. The temperatures at different places on the thermosyphon and on the inlet/outlet ofthe cooling water were measured. It was observed that change in heat flux, fill ratio and employing different extra volumes, has a significant effect on its performance. On the other hand, with changes in the cooling water flow rate the performance ofthe thermosyphon was altered regarding the trapped air movement. In order to illustrate the effect ofthe existence ofair in deactivating the thermosyphon, the pipe was cooled down by disconnecting the evaporator power input. It was seen that the thermosyphon loses its performance as the trapped gas occupies the whole condenser. The whole study shows that due to the existence ofthe trapped air, the heat loads can have significant effects on the thermosyphon performance.
Transport Phenomena,
Volume 6, Issue 4 , October 2009, , Pages 44-61
Abstract
A numerical investigation was carried out to solve the flow dimensionless partial differential equations through rectangular microchannels. A purely viscous power law model was used to characterize the flow behavior of non-Newtonian fluids. The flow was assumed to be steady and laminar, and slip conditions ...
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A numerical investigation was carried out to solve the flow dimensionless partial differential equations through rectangular microchannels. A purely viscous power law model was used to characterize the flow behavior of non-Newtonian fluids. The flow was assumed to be steady and laminar, and slip conditions were used as boundary conditions at the walls. The problem was solved for different power law indices as well as for various rectangular aspect ratios. Results showed that the effects ofslip velocity on dilatant fluids are more pronounced than that for pseudoplastic fluids. An increase in the power law index enhances the product of the friction factor and the Reynolds number, as well as the dimensionless incremental pressure drop and the dimensionless maximum velocity, while the hydrodynamic entrance length decreases. Results emphasize the significant effects of channel aspect ratio on the hydrodynamic flow behavior through microchannels.
Transport Phenomena,
Volume 6, Issue 3 , July 2009, , Pages 3-12
Transport Phenomena,
Volume 6, Issue 3 , July 2009, , Pages 13-25
Abstract
"> Waste heat recovery is very important, because it not only reduces the expenditure of heat generation, but also it is of high priority in environmental consideration, such as reduction in greenhouse gases. One of the devices used in waste heat recovery is heat pipe heat exchanger. An experimental ...
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"> Waste heat recovery is very important, because it not only reduces the expenditure of heat generation, but also it is of high priority in environmental consideration, such as reduction in greenhouse gases. One of the devices used in waste heat recovery is heat pipe heat exchanger. An experimental and theoretical research is carried out to investigate heat performance of an air to water thermosyphon heat pipe heat exchanger according to ε-NTU method. The experiments were done according to the following procedure: cold water with 0.1kg/s flows through the condensation section and hot air in a closed cycle is blown into the evaporation section. A blower with varying frequency of current turns in the mass flow rate between 0.14-0.6 kg/s and a temperature range of 125-225°C. The results of the experiments show that as the ratio of C Ch c rises, the rate of heat transfer goes up. The efficiency of the heat pipe heat exchanger remains constant as the temperature of the hot stream goes up, but the amount of heat transferred increases.
Transport Phenomena,
Volume 6, Issue 3 , July 2009, , Pages 26-45
Abstract
ewline"> Dispersion of heavy gases is considered to be more hazardous than the passive ones because it takes place more slowly. When the gas is accidentally released at ground level or where there are many obstacles in the area it is considered to be a heavy gas. In this paper, based on the extensive ...
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ewline"> Dispersion of heavy gases is considered to be more hazardous than the passive ones because it takes place more slowly. When the gas is accidentally released at ground level or where there are many obstacles in the area it is considered to be a heavy gas. In this paper, based on the extensive experimental work of McQuid and Hanna, the model was tested against two types of experiments: A simple experiment “Thorney Island” and a complex experiment “Kit Fox” in order to validate CFD code. In order to accomplish this validation the multiphase approach was employed. Also, the vertical temperature gradient in the atmosphere was investigated. The investigation of wind speed was done taking factors such as time, height and direction into consideration. In order to reduce the number of elements in the computational domain, a combination of 2D and 3D geometry was utilized. The results showed that the wind inlet correction, as well as the temperature gradient, had a significant influence on gas concentration records.
Transport Phenomena,
Volume 6, Issue 3 , July 2009, , Pages 46-56
Abstract
"> Experimental measurements of overall gas holdup (εg), residence time distribution (RTD) and liquid mixing time (tm) have been carried out in an air-water system in a 17 lit bubble column with an 11 cm diameter, over a wide range of superficial gas velocity (0.14-1.46 ms-1) and height to ...
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"> Experimental measurements of overall gas holdup (εg), residence time distribution (RTD) and liquid mixing time (tm) have been carried out in an air-water system in a 17 lit bubble column with an 11 cm diameter, over a wide range of superficial gas velocity (0.14-1.46 ms-1) and height to diameter ratio (1.36-8.84). The bed expansion method was used to obtain holdup values and the change of slope related to εg versus superficial gas velocity (Usg) indicated the transition point from homogeneous to heterogeneous regime at Usg= 0.7-0.9 ms-1. Besides, the experiments illustrated that H/D ratio had no effect on holdup values. The axial dispersion model was used with semi-closed boundary conditions for prediction of RTD, and hence, the axial dispersion coefficients (Dax). Moreover, fitting results of the model and experimental RTD curves achieved from tracer injection method attained the model parameter, Dax , in three H/D ratios of 4.73, 6.36 and 8.84. Results showed that an elevation in H/D ratio, caused a rise in D ax. On the other hand, the mixing time data declined with an increase in Usg; however enhancement of H/D ratio caused an increase in tm.