scholarly journals Biogas Production and Heat Transfer Performance of a Multiphase Flow Digester

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1960 ◽  
Author(s):  
Pei Guo ◽  
Jiri Zhou ◽  
Rongjiang Ma ◽  
Nanyang Yu ◽  
Yanping Yuan
Keyword(s):  
Heat Transfer ◽  
Anaerobic Digestion ◽  
Multiphase Flow ◽  
Production Rate ◽  
Transfer Rate ◽  
Field Experiments ◽  
Heat Transfer Performance ◽  
Biogas Production ◽  
Transfer Performance ◽  
Biogas Production Rate

Traditional static anaerobic digestion technology presents the disadvantages of a low gas production rate and long digestion cycle, which is not conducive to the treatment of livestock manure. A 12 m3 multiphase flow anaerobic digester (MFD) was developed in this study to improve the biogas production rate and maintain constant temperature digestion during winters. Full-scale field experiments were conducted on the biogas production rate at different temperatures, the dynamic digestion effects, and the dynamic heating digestion effects of the system at Sichuan, China. A comparison of the dynamic and static digestion results of 50 days indicated that the biogas production for the dynamic digestion (DD) group was 115.22 m3 or 127.1% higher than that of the static digestion (SD) group with the same digestion temperature. The results of the heat transfer performance experiment revealed that the heat transfer rate of the system increased significantly, and the temperature of the biogas slurry increased rapidly. The optimization analysis of the system was based on the experimental results of the relationship between the slurry temperature and biogas production rate, and the economical digestion temperature of the system was proposed and calculated. Different insulation materials or insulation thicknesses have an influence on the economical digestion temperature. Additionally, the economical digestion temperature of the system in which the polystyrene insulation layer with a thickness of 90 mm was used, was found to be 27.2 °C. When digestion temperature was 22.3 °C, the energy efficiency ratio (EER) of dynamic anaerobic digestion system is 1. The advantages of MFD are low biogas production unit cost and high heat and mass transfer rate. However, the disadvantage of high operation energy consumption needs further improvement. And additional energy was required when system digestion temperature below 22.3 °C. The proposed MFD and dynamic anaerobic digestion system can play a significant role in using biomass resources and promoting the development of biogas projects.

Heat Transfer in Serpentine Flow Passages With Rotation

1994 ◽  
Vol 116 (1) ◽  
pp. 133-140 ◽  
Author(s):  
S. Mochizuki ◽  
J. Takamura ◽  
S. Yamawaki ◽  
Wen-Jei Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Performance ◽  
Flow Passage ◽  
Rotation Numbers ◽  
Straight Flow

Heat transfer characteristics of a three-pass serpentine flow passage with rotation are experimentally studied. The walls of the square flow passage are plated with thin stainless-steel foils through which electrical current is applied to generate heat. The local heat transfer performance on the four side walls of the three straight flow passages and two turning elbows are determined for both stationary and rotating cases. The throughflow Reynolds, Rayleigh (centrifugal type), and rotation numbers are varied. It is revealed that three-dimensional flow structures cause the heat transfer rate at the bends to be substantially higher than at the straight flow passages. This mechanism is revealed by means of a flow visualization experiment for a nonrotating case. Along the first straight flow passage, the heat transfer rate is increased on the trailing surface but is reduced on the leading surface, due to the action of secondary streams induced by the Coriolis force. At low Reynolds numbers, the local heat transfer performance is primarily a function of buoyancy force. In the higher Reynolds number range, however, the circumferentially averaged Nusselt number is only a weak function of the Rayleigh and rotation numbers.

Influence of Pattern Geometry of Hybrid Surfaces on Dropwise Condensation Heat Transfer and Droplet Dynamics

2018 ◽  
Author(s):  
Karim Egab ◽  
Saad K. Oudah ◽  
M. Alwazzan ◽  
Jamil Khan ◽  
Chen Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Significant Influence ◽  
Atmospheric Pressure ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Condensation Heat Transfer ◽  
Transfer Performance ◽  
Droplet Dynamics ◽  
Lower Performance

The scope of combining two wettability regions is to impact the droplet dynamic behaviors, manipulate the droplets’ mobility and enhance condensation heat transfer. Hydrophobic-hydrophilic hybrid patterns can promote the heat transfer, droplet-renewal frequency and enhance the droplets’ removal during condensation. With regard of condensation on hybrid surfaces, the geometry of the patterns has a significant influence on droplets departure frequency and heat transfer performance. Therefore, different patterns geometries (circle, ellipse, and diamond) have been developed on horizontal copper tubes at atmospheric pressure. All the patterns have the same size, and the same identical gap as well between the adjacent patterns. Results show that the diamond hybrid surface has the best performance compared with ellipse, circles hybrid surfaces at the same pattern area with same neighbor gap between two patterns and complete dropwise However, the circle and ellipse hybrid surfaces outperform lower performance compared to complete dropwise surface. The heat transfer rate for the diamond hybrid surface is 15% higher than complete dropwise surface when the gap is 0.5mm. This study clearly demonstrated the effect of pattern’s geometry regarding maximum condensation heat transfer rate and droplet departure frequency.

scholarly journals Analytical solution and process analysis of energy pile’s heat transfer rate

2020 ◽  
Vol 205 ◽  
pp. 05026
Author(s):  
Jun Yang ◽  
Zhenguo Yan ◽  
Zhengwei Zhang ◽  
Shu Zeng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Heat Transfer Process ◽  
Transfer Performance ◽  
Energy Pile ◽  
Energy Piles ◽  
The Difference ◽  
Surrounding Soil

With the ever-increasing energy demand and implications of climate change, the use of energy piles to absorb shallow geothermal energy to regulate room temperature of buildings is considered the best sustainable energy technology, especially in China, and the use of this technology is becoming increasingly popular. At present, studies generally uses the temperature field to analyze the heat transfer performance of the energy pile, which cannot represent the heat transfer rate distribution intuitively. In this study, we used mathematical models to provide an analytical solution to determine the heat transfer rate distribution between the energy pile and surrounding soil. Analysis of the heat transfer process of concrete piles in clay showed that the difference in thermal properties between the energy pile and the surrounding soil affected the whole heat transfer process, especially in the initial stage. The time required to reach the quasi-steady state mainly depended on the pile’s volume heat capacity, the thermal diffusivity of the pile and the surrounding soil. In engineering practice, to enhance the heat transfer performance of energy piles, the following measures can be taken: reduce the difference in thermal properties between the energy pile and surrounding soil and increase the distance between energy piles to improve the heat transfer conditions.

scholarly journals Field Study on the Air-Side Heat Transfer Performance of Copper Finned-Flat Tubes for Heavy-Duty Truck Radiators

2021 ◽  
Vol 39 (5) ◽  
pp. 1451-1459
Author(s):  
Jose Canazas
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heavy Duty ◽  
Cooling Systems ◽  
Heavy Duty Truck ◽  
Flat Tubes

Heavy-duty truck cooling systems have been given low importance in the enhancement and research of heat transfer performance since off-highway conditions are hard to evaluate in laboratory essays or CFD studies. The present work is performed to evaluate the heat transfer performance of copper finned-flat tubes used in heavy-duty truck radiators. Parameters were measured in the field of two heavy-duty truck engines cooling systems. In both vehicles water is used as the cooling fluid. The results showed that the Air convective heat transfer coefficient and Overall heat transfer coefficient on the air side decreases as the Reynolds Number decreases and increases as passing through the first row to the fourth row. Additionally, the mass air flow and heat transfer rate have very high values in comparison from normal automotive radiators' operative conditions, since heavy-duty truck radiators require a large heat transfer rate. The analysis presented in this paper was used for a heavy-duty truck radiator but can be extended to any equipment with finned flat tubes. A more accurate study should be done considering vibrations and different environmental conditions.

scholarly journals Anaerobic Digestion of Cassava (Manihot Esculenta) Waste: Effects of Inoculum on Biogas Production Rate

2020 ◽  
Vol 4 (2) ◽  
pp. 411-420
Author(s):  
B.E. Eboibi ◽  
K.O. Adiotomre ◽  
F. Onobrudu ◽  
E. Osioh
Keyword(s):  
Anaerobic Digestion ◽  
Production Rate ◽  
Manihot Esculenta ◽  
Decay Constant ◽  
Biogas Production ◽  
Cow Manure ◽  
Anaerobic Digesters ◽  
First Order ◽  
Cassava Peel ◽  
Biogas Production Rate

In this paper, cow manure fluid was used as inoculums to investigate biogas production rate from anaerobic digestion of cassava peel at mesophilic temperature (280C). The anaerobic experiment was conducted using six batch digesters (D1, D2, D3, D4, D5 and D6) each of 20L capacity for 40-day hydraulic retention. Each digester, was loaded with 5kg of cassava peel (CP) and 0%, 10%, 20%, 30%, 40% and 50% of inoculum to CP. Hashimoto model was used to obtain the digestion kinetic parameters. The results of the study showed that inoculums influenced the rate of biogas production, showing variations in biogas production, correlation coefficient (R2) and in first-order decay constant (k). The average cumulative biogas production was in the range of ~2358 to 4010ml/kgVS for 10% to 50% inoculum. The R2 and k for D1 was 0.959 and 0.359 D1 (without inoculum), 0.990 and 0.371 for D2 (10% inoculum) and 0.991 and 0.371 for D3 (20% inoculum), 0.951 and 0.356 for D4 (30% inoculum), 0.992 and 0.372 for D5 (40% inoculum), and 0.990 and 0.371 was obtained for D6 loaded with 50% inoculum. Despite variation in biogas yields from different inoculums, biogas production obtained from anaerobic digesters loaded with inoculums were still lower compared with that without inoculum.

Reducing Crossflow Effects in Arrays of Impinging Jets

2017 ◽  
Author(s):  
Nicholas R. Arens ◽  
Mitchell P. Morem ◽  
Jeffrey Doom ◽  
Gregory J. Michna
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Cfd Modeling ◽  
Working Fluid ◽  
Transfer Performance ◽  
Simulation Data ◽  
Jet Array

With increasing heat fluxes in microelectronics, thermal management of these devices will soon no longer be attainable through current methods. One thermal management technology that could be integrated into the design of microelectronics is jet impingement cooling. Past research has primarily focused on evenly spaced, equal-sized, circular or slot jets perpendicular to the surface. A significant problem associated with this technology, especially as the surface to be cooled increases in size, is crossflow. This is the interaction of the transverse flow from the spent inner jet fluid with the jets closer to the outer edge of the surface. In an attempt to attenuate the crossflow effects, the heat transfer performance of jet arrays with non-uniform jet diameter and jet spacing were investigated. The testing apparatus housed a 3D-printed jet array nozzle that could be easily exchanged to accommodate many tests. The use of advanced manufacturing techniques allows for array geometries that may have previously been difficult to create. The impingement surface was a circular, polished, oxygen-free copper surface with a diameter of 25.4 mm. Heat transfer rates nearing 400 W could be delivered to the surface, for a heat flux of more than 75 W/cm2. The working fluid was single phase water, and the heat transfer rate was measured for each jet array over a range of flow rates. Experimental data was compared to simulation data obtained through CFD analysis. CFD modeling was used to predict the most promising geometries, which were then validated through experiment. Out of the nozzles tested, it was determined that the nozzle with larger diameters toward the edge of the surface attained the highest heat transfer rate of h = 38,822 W/m2-K. The nozzle with closer jet spacing at the outside of the array was found to have the highest experimental Nusselt number with NuD = 88.8. It was determined that angled confining walls do not have a definitive association with improved heat transfer. The simulation data was found to predict the heat transfer performance of the various geometries with an average percent difference in heat transfer coefficient of 11%.

scholarly journals Numerical Calculations on Flow and Heat Transfer in Smooth and Ribbed Two-Pass Square Channels under Rotational Effects

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Zhongyang Shen ◽  
Yonghui Xie ◽  
Di Zhang ◽  
Gongnan Xie
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Thermal Characteristics ◽  
Transfer Performance ◽  
Operation Condition ◽  
Flow And Heat Transfer ◽  
Rotation Numbers ◽  
First Pass

U-shaped channel, which is also called two-pass channel, commonly exists in gas turbine internal coolant passages. Ribbed walls are frequently adopted in internal passage to enhance the heat transfer. Considering the rotational condition of gas turbine blade on operation, the effect of rotation is also investigated for the coolant channel which is close to real operation condition. Thus, the objective of this study is to discuss the effect of rotation on fluid flow and heat transfer performance of U-shaped channel with ribbed walls under high rotational numbers. Investigated Reynolds number is Re=12500and the rotation numbers areRob=0.4and 0.6. In the results, the spatially heat transfer coefficient distributions are exhibited to discuss the effect of rotation and roughened walls. It is found that ribbed walls enhance the heat transfer rate significantly. Under the rotational condition, theNuin the first pass with outward flow is increased while that in the second pass is decreased. Finally, averageNuratio, friction ratio, and thermal performance are all presented to discuss the thermal characteristics.

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