Numerical Simulation of Flow and Thermal Behavior of Radiating Gas Flow in Plane Solar Heaters

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Mohammad Foruzan Nia ◽  
Seyyed Abdolreza Gandjalikhan Nassab ◽  
Amir Babak Ansari
Keyword(s):  
Numerical Simulation ◽  
Temperature Distribution ◽  
Thermal Efficiency ◽  
Gas Flow ◽  
Simple Algorithm ◽  
Outlet Section ◽  
Gas Temperature ◽  
Conservation Of Energy ◽  
Solid Media ◽  
Solar Heater

Abstract In this paper, the radiating effect of working gas on thermal performance of plane solar heaters is investigated. In the numerical simulation of gas flow, the continuity and momentum equations are solved using the finite volume method (FVM) in which the pressure–velocity coupling is handled by the SIMPLE algorithm. To obtain the temperature distribution, the conservation of energy in the fluid and solid media is solved by the finite difference technique. The distribution of radiating intensity which is needed to calculate the radiative term in the gas energy equation is computed by numerical solution of the radiative transfer equation (RTE) using the discrete ordinate method (DOM). The effect of the variation of different parameters on the predicted thermal efficiency of plane solar heater is investigated by presenting the performance plot. The obtained results show that when the gas medium participates in radiation, the gas temperature at the outlet section increases considerably, especially at high optical thicknesses. Also, the temperature difference between the absorber plate and flowing gas decreases, and more uniform temperature distribution takes place inside the solar heater, which leads to a considerable increase in thermal efficiency. Comparison between the present numerical results and the experimental data published in literature shows good agreement.

Assessment of a Syngas-Diesel Dual Fuelled Compression Ignition Engine

2010 ◽  
Author(s):  
Bibhuti B. Sahoo ◽  
Niranjan Sahoo ◽  
Ujjwal K. Saha
Keyword(s):  
Diesel Engine ◽  
Thermal Efficiency ◽  
Gas Flow ◽  
Direct Injection ◽  
Dual Fuel ◽  
Exhaust Gas ◽  
Compression Ignition ◽  
Gas Temperature ◽  
Compression Ignition Engine ◽  
Exhaust Gas Temperature

Synthesis gas (Syngas), a mixture of hydrogen and carbon monoxide, can be manufactured from natural gas, coal, petroleum, biomass, and even from organic wastes. It can substitute fossil diesel as an alternative gaseous fuel in compression ignition engines under dual fuel operation route. Experiments were conducted in a single cylinder, constant speed and direct injection diesel engine fuelled with syngas-diesel in dual fuel mode. The engine is designed to develop a power output of 5.2 kW at its rated speed of 1500 rpm under variable loads with inducted syngas fuel having H2 to CO ratio of 1:1 by volume. Diesel fuel as a pilot was injected into the engine in the conventional manner. The diesel engine was run at varying loads of 20, 40, 60, 80 and 100%. The performance of dual fuel engine is assessed by parameters such as thermal efficiency, exhaust gas temperature, diesel replacement rate, gas flow rate, peak cylinder pressure, exhaust O2 and emissions like NOx, CO and HC. Dual fuel operation showed a decrease in brake thermal efficiency from 16.1% to a maximum of 20.92% at 80% load. The maximum diesel substitution by syngas was found 58.77% at minimum exhaust O2 availability condition of 80% engine load. The NOx level was reduced from 144 ppm to 103 ppm for syngas-diesel mode at the best efficiency point. Due to poor combustion efficiency of dual fuel operation, there were increases in CO and HC emissions throughout the range of engine test loads. The decrease in peak pressure causes the exhaust gas temperature to rise at all loads of dual fuel operation. The present investigation provides some useful indications of using syngas fuel in a diesel engine under dual fuel operation.

Effect of Water Injection in Acetylene-Diesel Dual Fuel DI Diesel Engine

2012 ◽  
Author(s):  
T. Lakshmanan ◽  
A. Khadeer Ahmed ◽  
G. Nagarajan
Keyword(s):  
Diesel Engine ◽  
Thermal Efficiency ◽  
Alternative Fuels ◽  
Gas Flow ◽  
Water Injection ◽  
Intake Manifold ◽  
Dual Fuel ◽  
Intake Port ◽  
Gas Temperature ◽  
Brake Thermal Efficiency

Gaseous fuels are good alternative fuels to improve the energy crisis of today’s situation due to its clean burning characteristics. However, the incidence of backfire and knock remains a significant barrier in commercialization. With the invention of latest technology, the above barriers are eliminated. One such technique is timed injection of water into the intake port. In the present investigation, acetylene was aspirated in the intake manifold of a single cylinder diesel engine, with a gas flow rate of 390 g/h, along with water injected in the intake port, to overcome the backfire and knock problems in gaseous dual fuel engine. The brake thermal efficiency and emissions such as NOx, smoke, CO, HC, CO2 and exhaust gas temperature were studied. Dual fuel operation of acetylene induction with injection of water results in lowered NOx emissions with complete elimination of backfire and knock at the expense of brake thermal efficiency.

Simulation Research of Interior Ballistics Performance for a New-Type Light Caliber Cannon

2013 ◽  
Vol 446-447 ◽  
pp. 458-462
Author(s):  
Jia Ning Li ◽  
Xin Liao ◽  
Feng Qiang Nan
Keyword(s):  
Numerical Simulation ◽  
Temperature Distribution ◽  
Phase Flow ◽  
Gas Temperature ◽  
Projectile Velocity ◽  
Two Phase ◽  
Simulation Research ◽  
Interior Ballistics ◽  
New Type ◽  
Simulation Results

In order to make a precise interpret and research of interior ballistics performance for a new-type light caliber cannon, an interior ballistics mathematical and physical model was established, on the basis of two-phase flow interior ballistics theory and description of interior ballistic cycle. MATLAB software was used to conduct numerical simulation. Conclusion indicates that the simulation results manifest favorable consistency with the experiment results. Simulation results can comprehensively interpret the physical process in guns by pressure distribution, projectile velocity and gas temperature distribution.

scholarly journals Research on the experimental performance of gas-fired boiler based on the total heat recovery technology of absorption heat pump

2021 ◽  
Vol 261 ◽  
pp. 01059
Author(s):  
Xujing Zhai ◽  
Shoutao Tian ◽  
Kelin Zhu ◽  
Pan Huang ◽  
Jin Yu ◽  
...  
Keyword(s):  
Energy Saving ◽  
Heat Pump ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Gas Flow ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Absorption Heat Pump ◽  
Reconstruction Project ◽  
Exhaust Gas Temperature

Based on an example of a gas-fired boiler for an industrial user in Tianjin, the absorption heat pump technology was used to carry out energy-saving transformation of the above boiler. The actual test was carried out on the gas flow, exhaust gas temperature and other parameters from January 2, 2018 to February 26, 2018. And then, the thermal efficiency of the boiler was analysed. The results show that after the energy-saving transformation, the exhaust gas temperature of the gas-fired boiler can be reduced from 140 °C to about 40 °C, and the overall thermal efficiency of the boiler also rises from 89.5% to 101.3%, which is 13.2% higher than that before optimization. According to the economic analysis, the energy-saving reconstruction project can achieve an energy-saving economic benefit of 1.598 million yuan throughout the year, with obvious energy-saving and emission reduction benefits.

scholarly journals Study on Distribution of Wellbore Temperature in Gas Drilling with Gradient Equations

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhongxi Zhu ◽  
Chaofei Wang ◽  
Zhigang Guan ◽  
Wanneng Lei
Keyword(s):  
Temperature Distribution ◽  
Gradient Method ◽  
Gas Flow ◽  
Temperature Drop ◽  
Geothermal Gradient ◽  
Cooling Effect ◽  
Formation Temperature ◽  
Gas Temperature ◽  
Local Cooling ◽  
Gas Drilling

Precise calculation of gas temperature profile is the key to gas drilling design. It is traditionally assumed that the gas temperature distribution in the wellbore is equal to the formation temperature, without considering the influence of fluid flow and Joule-Thomson cooling effect. This paper puts forward a gradient equation method for gas temperature distribution in wellbore considering gas flow and Joule-Thomson local cooling of the bit. The method applies pressure, temperature, density, and velocity equations to gas flow in drillstrings and annulus. The solution of the gradient equation is in the form of the fourth-order Runge-Kutta equation. Bottom wellbore temperatures measured at depths of 700 to 2000 m in an actual well are consistent with those predicted by the gradient method. Due to the Joule-Thomson cooling effect at the bit nozzle, the temperature drops by about 30°C. The sensitivity analysis is carried out by gradient method, and the results show that the temperature drop range of different nozzle sizes can reach 60°C due to the Joule-Thomson cooling effect. Stable temperature curves can be established within a few minutes of the gas cycle. Due to the influence of gas flow and Joule-Thomson cooling, the gas temperature in the wellbore deviates significantly from the geothermal temperature in the formation under the flow condition. The temperature of the gas in drillstrings increases as the drill depth increases and then decreases rapidly near the bottom of the hole. As the gas flows upward along the annulus, the gas temperature rises first, surpasses the formation temperature, and then decreases gradually along the geothermal gradient trend.

scholarly journals Investigation on influences of loose gas on gas-solid flows in a circulating fluidized bed (CFB) reactor using full-loop numerical simulation

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Pengju Huo ◽  
Xiaohong Li ◽  
Yang Liu ◽  
Haiying Qi
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Gas Flow ◽  
Circulating Fluidized Bed ◽  
Separation Efficiency ◽  
Circulation Rate ◽  
Solid Mass ◽  
Gas Flow Rate ◽  
Gas Leakage ◽  
Mass Circulation

AbstractThe influences of loose gas on gas-solid flows in a large-scale circulating fluidized bed (CFB) gasification reactor were investigated using full-loop numerical simulation. The two-fluid model was coupled with the QC-energy minimization in multi-scale theory (EMMS) gas-solid drag model to simulate the fluidization in the CFB reactor. Effects of the loose gas flow rate, Q, on the solid mass circulation rate and the cyclone separation efficiency were analyzed. The study found different effects depending on Q: First, the particles in the loop seal and the standpipe tended to become more densely packed with decreasing loose gas flow rate, leading to the reduction in the overall circulation rate. The minimum Q that can affect the solid mass circulation rate is about 2.5% of the fluidized gas flow rate. Second, the sealing gas capability of the particles is enhanced as the loose gas flow rate decreases, which reduces the gas leakage into the cyclones and improves their separation efficiency. The best loose gas flow rates are equal to 2.5% of the fluidized gas flow rate at the various supply positions. In addition, the cyclone separation efficiency is correlated with the gas leakage to predict the separation efficiency during industrial operation.

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