38 research outputs found
การเพิ่มความสามารถถ่ายเทความร้อนบนพื้นผิวที่เจ็ทพุ่งชนโดยลดผลกระทบจากกระแสไหลตัด
No full textThesis (Ph.D. (Mechanical Engineering))--Prince of Songkla University, 201
ICOPE-15-1138 Effect of Orifice Geometry on Heat Transfer Characteristics of Array of Impinging Jets in Confined Channel
No full text1073 FLOW AND HEAT TRANSFER CHARACTERISTICS OF ROW OF JET IMPINGEMENTS FROM ELONGATED ORIFICES UNDER CROSS-FLOW
No full textThe effect of single and double air inlets on swirling flow in a reactor of a fluidized bed gasifier
No full textIn this work, the effect of single and double air inlets on swirling flow in a reactor of
fluidized bed gasifier was studied numerically. The reactor diameter (D) was 20 cm,
and the reactor length was 7.5D. The geometry of the reactor bottom was conical. In
order to generate swirling flow in the reactor, the air inlet pipe with inner diameter of
46.8 mm was assembled tangentially to the bottom of the reactor. The comparison of
the effect of single and double air inlets were studied based on the same mass flow
rate. A 3-D numerical model of the reactor was created using a commercial software
of ANSYS Ver.15.0 (Fluent). The results showed that swirling flow at the bottom of
the reactor for the case of double inlets was more uniform than that of single inlets.
Therefore, double air inlets were applied to design and fabricate a swirling fluidized
bed gasifier
Influence of nozzle arrangement on flow and heat transfer characteristics of arrays of circular impinging jets
No full textThe effect of jet arrangements on flow and heat transfer characteristics was experimentally and numerically investigatedfor arrays of impinging jets. The air jets discharge from round orifices and perpendicularly impinge on a surface within arectangular duct. Both the in-line and staggered arrangements, which have an array of 6×4 nozzles, were examined. A jet-toplate distance (H) and jet-to-jet distance (S) were fixed at H=2D and S=3D, respectively (where D is the round orificediameter). The experiments were carried out at jet Reynolds number Re=5,000, 7,500 and 13,400. Temperature distributions onthe impingement surface were measured using a Thermochromic Liquid Crystal sheet, and Nusselt number distributions wereevaluated using an image processing method. The flow characteristics on the impingement surface were visualized using theoil film technique. The numerical simulation employed to gain insight into the fluid flow of jets between the orifice plate andthe impingement wall was via computational fluid dynamics. The results reveal that the effect of crossflow on the impingingjets for the staggered arrangement is stronger than that in the case of in-line arrangement. In the latter case of in-line arrangement, the crossflow could pass throughout the passage between the rows of jets, whereas in the former case the crossflowwas hampered by the downstream jets. The average Nusselt number of the in-line arrangement is higher than that of thestaggered arrangement by approx. 13-20% in this study
Development of mini pilot fluidized bed gasifier for industrial approach: Preliminary study based on continuous operation
No full textA small pilot scale of bubbling fluidized bed gasifier was designed and fabricated. The
diameter of reactor (D) is 20 cm and the total height of the reactor from the bottom
end of the cone to the top is 160 cm. The feedstock used was palm kernel cake which
the size range of 1-10 mm. The mass feeding rate of feedstock was fixed at 0.05 kg/min,
and flow rate of air was varied according to Equivalent Ratio (ER) at 0.03, 0.06, 0.19,
0.31, 0.49, 1.17, 1.43 and 2.64, respectively. In the first phase of this work is to focus
on continuous gasification operation that expected approximately for 8 hours without
shut down or malfunction. Based on the result obtained in this study, it was found that
the ER which can be provided for continuous operation was 0.19≥ER≥1.17. For the
syngas production study at the ER of 0.06 and 1.43 could not run continuously.
Moreover, the gasification run at ER=0.03 and 2.64 was found that the syngas
production was incombustible
Heat Transfer Enhancement for Row of Impinging Jets in Cross-Flow with Some Baffle Attachments
No full text
The effect of Biomass Shapes on combustion characteristic in updraft chamber
No full textThe objective of this work was to study the effect of biomass shapes on combustion characteristic in an updraft chamber. 6 types of biomasses: rubber wood chips, coconut shell, oil palm empty fruit bunch, corn straw, rubber wood sawdust, and mixed palm cake that are agricultural wastes in Thailand were categorized by 3 shapes namely: chip shape, fiber shape, and powder shape. They were burnt using a combustion chamber, which was a simple type of direct combustion. The diameter of combustion chamber was 20 cm and the total height of the combustion chamber was 160 cm. Biomass sample, which moisture content was lower than 20%, was fixed at 1 kg per experiment for burning. The air velocity was varied at 0.50, 0.75 and 1.00 m/s which corresponds to an equivalence ratio between 1 up to 3.5. The temperature at different positions along combustion chamber height and the properties of product gas (carbon monoxide) were measured. The experimental results show that the biomass shape influences the combustion process. The fiber shape has low combustion temperature and higher carbon monoxide, which is indicated improper combustion. The chip shape was well burnt with higher air velocity and the product gas has the lowest amount of carbon monoxide. In addition, it had lower temperature than powder shapes. As for the powder shapes, it shows suitability for combustion with an updraft combustion chamber because it has the highest temperature compared with other types of biomass. However, it has some limitation for some powder biomass types as sawdust. When the air velocity was high, there was carryover of biomass particles without burning
Entropic analysis of a double helical tube heat exchanger including circular depressions on both inner and outer tube
No full textIn this research, entropic analysis of a double helical tube heat exchanger including circular depressions on both inner tube and outer tube is provided. Experimentally validated 3D numerical simulation is employed to reach the aim of this study. Entropic characteristics of four cases are investigated and reported. In case “a” both inner tube and outer tube are smooth. In case “b”, circular depressions are created on only inner tube while in case “c” both tubes contain circular depression. Case “d” is the same as case “c” while the depression arrangement is different from case “c”. Dimensionless entropy generation and dimensionless Nu number are used to evaluate the proposed designs based on the first and second laws of thermodynamics. Moreover, heat transfer improvement (HTI) factor is adopted to consider the impacts of said two parameters simultaneously. Results demonstrate that, although creating circular depressions on both tubes significantly improves the heat transfer characteristics of the heat exchanger, it increases the entropy generation level of heat exchanger as well. Case “d” in which the location of any circular depression of the outer tube is placed between any two continuous depressions of the inner tube, gives the highest thermal performance and also entropy generation
