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Aims and Scope
Editorial Board

1. Flow behavior in an agglomerated fluidized bed gasifier

Nora C I S Furuvik, Rajan Jaiswal, Britt M E Moldestad

Department of Process, Energy and Environmental Technology, Faculty of Technology, Natural Sciences and Maritime Sciences, University of South-Eastern Norway, Kjølnes Ring 56, 3901 Porsgrunn, Norway.

Abstract: The global energy demand has increased over the last decades and the need for utilization of energy produced from sustainable sources is stressed. Fluidized bed gasification of biomass is a thermochemical conversion process that involves heating and converting of biomass into a gaseous mixture of syngas. The syngas can be used for sustainable production of heat, power and biofuels for useful applications. Agglomeration of bed material due to ash melting is one of the biggest challenges associated with fluidized bed gasification of biomass. Inorganic alkali components from the biomass cause problems as they can form a sticky layer on the surface of the bed particles and make them grow towards larger agglomerates that will interfere with the fluidization process. The aim of this work was to study the effect of agglomerates on the flow behavior in a fluidized bed gasifier. The experiments were performed in a cold-flow model of a bubbling fluidized bed at ambient temperature. Three different experiments were carried out: (I) with sand particles as bed material, (II) with agglomerates located at the bottom of the bed and (III) with agglomerates located at the top of the bed. The results show that agglomerates lead to decreased pressure drop and increased minimum fluidization velocity. The minimum fluidization velocity increased from 0.035 m/s in the normal fluidized bed to 0.041 m/s in the agglomerated fluidized bed where the agglomerates were placed at the bottom of the bed. The minimum fluidization velocity increased further to 0.057 m/s in the agglomerated fluidized bed where the agglomerates where added from the top of the bed. This study also found that bed agglomeration causes channeling and poor fluidization conditions.

2. Experimental investigations on heat transfer enhancement for a high aspect ratio rectangular duct roughened by intersecting ribs with inclined ribs

Ali Hussein F. Theeb, Munther Abdullah

Mechanical Engineering Department, University of Baghdad, Iraq.

Abstract: In this work, the effect of the intersecting ribs with inclined ribs on the heat transfer performance and friction factor through a rectangular roughened duct have been experimentally investigated. The chosen aspect ratio of the duct (W/H) was 10 and Reynolds number was in the range between 35,700 up to 72,800. The rib-pitch-to-height-ratio (P/e) and Relative roughness height (e/Dh) were 10 and 0.068 respectively. The inclination of the rib with respect to the flow, generates counter-rotating secondary flow along the span that causes span wise variation of heat transfer coefficient. The fluid enters at the leading zone of the rib and travel to the trailing zone, thus raising heat transfer rate at the leading zone while the trailing zone heat transfer is relatively low. To minimize this effect, longitudinal ribs were suggested to use with the inclined ribs in intersection form. A single longitudinal rib was installed at the center of the plate with parallel to flow, this for Model 2, and two longitudinal ribs were used for Model 3. Using the intersecting ribs lead to induced new vortices at every intersection point in addition to the primary vorticities at the leading corner of the inclined rib. So, the heat transfer at the trailing zone will enhance. Therefore, the model 3 provide highest Nusselt number ratio than model 2 are about 13.19 % and 7.03%, respectively, with respect to that of the model 1 (without intersecting ribs), Also, it can be observed that the model 3 with two Intersecting ribs mostly provides higher overall efficiency indices rather than those of the model 2 and 1.

3. Uncertainty comparison of viscosity measurements of CO₂ loaded MEA and water mixtures in a coaxial rheometer using Monte Carlo simulation and GUM method

Sumudu S. Karunarathne, Dag A. Eimer, Lars E. Øi

University of South-Eastern Norway, Kjølnes ring 56, Porsgrunn 3901, Norway.

Abstract: Evaluation of measurement uncertainty is vital in the measurement of physicochemical properties. The uncertainty of viscosity measurement of a mixture of monoethanol amine (MEA), water and CO2 is evaluated according to the Guide to the expression of Uncertainty in Measurement (GUM) and validated using Monte Carlo Simulation (MCS) method. This helps to estimate the truncation error due to the first order approximation of Taylor series on nonlinear models in GUM. In literature, only one method is normally used. Calculated uncertainty according to GUM for CO2 loaded aqueous MEA is 0.035 mPa·s. For the uncertainty of viscosity in unloaded aqueous MEA solutions, the confidence interval calculated by GUM deviates from calculated confidence interval according to MCS. This deviation is beyond the numerical tolerance defined for the comparison. The probability distributions of the uncertainty sources influence the distribution of the model output in the MCS method. For the uncertainty of viscosity in CO2 loaded aqueous MEA solutions, the confidence interval calculated by GUM is within the defined numerical tolerance and closer to the calculated confidence interval according to MCS. Combining GUM and MCS will improve confidence in the uncertainty evaluation.

4. Experimental characteristic of a solar parabolic trough collector with indirect steam generation system

Mohammed Hasan Abbood, Mohammed Mohsen Mohammed

Mechanical Engineering Dep., College of Engineering, University of Kerbala, Iraq.

Abstract: The experimental testing shows the construction and testing of three parabolic trough solar collectors (PTSC) experimentally in order to produce moderate-temperature steam. The experimental investigation was carried out on PTSC to testing the thermal performance of the system. The tests were carried out at University of Kerbala / college of engineering with climatic conditions (32.34o N, 44.03o E) for nine days during the month of July and August of 2018. Different parameters of the PTSC system are selected for testing this study such as heat transfer fluid (HTF) type (hydraulic oil, ethylene glycol, and water) and three flow rates of working fluid (1 LPM, 2 LPM, and 3 LPM). A process of steam generation was occurring with a steam temperature of 95.4oC and steam pressure of 2.1 bar. The experiments show that the maximum heat gain and high efficiency can be occurring with using hydraulic oil and the highest value of fluid flow rate. The results show that the maximum useful heat gain is 1.035 kW, 0.879 kW, and 0.734 kW for the case of using hydraulic oil, ethylene glycol based water, and water respectively, with 3 LPM flow rate. The peak experimental efficiencies close to 33.2%, 28.5%, and 22.7% were obtained for PTSC with hydraulic oil, ethylene glycol based water, and water respectively at the highest value of fluid flow rate.