Phase transition and flow-rate behavior of merging granular flows

2015 ◽  
Vol 91 (2) ◽  
Author(s):  
Mao-Bin Hu ◽  
Qi-Yi Liu ◽  
Rui Jiang ◽  
Meiying Hou ◽  
Qing-Song Wu
2021 ◽  
Vol 383 ◽  
pp. 536-541
Author(s):  
Xiaoyan Zhou ◽  
Shikun Liu ◽  
Zihan Zhao ◽  
Xin Li ◽  
Changhao Li ◽  
...  

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Megan F. Watkins ◽  
Richard D. Gould

Particle-based heat transfer fluids for concentrated solar power (CSP) tower applications offer a unique advantage over traditional fluids, as they have the potential to reach very high operating temperatures. Gravity-driven dense granular flows through cylindrical tubes demonstrate potential for CSP applications and are the focus of the present study. The heat transfer capabilities of such a flow system were experimentally studied using a bench-scale apparatus. The effect of the flow rate and other system parameters on the heat transfer to the flow was studied at low operating temperatures (<200 °C), using the convective heat transfer coefficient and Nusselt number to quantify the behavior. For flows ranging from 0.015 to 0.09 m/s, the flow rate appeared to have negligible effect on the heat transfer. The effect of temperature on the flow's heat transfer capabilities was also studied, examining the flows at temperatures up to 1000 °C. As expected, the heat transfer coefficient increased with the increasing temperature due to enhanced thermal properties. Radiation did not appear to be a key contributor for the small particle diameters tested (approximately 300 μm in diameter) but may play a bigger role for larger particle diameters. The experimental results from all trials corroborate the observations of other researchers; namely, that particulate flows demonstrate inferior heat transfer as compared with a continuum flow due to an increased thermal resistance adjacent to the tube wall resulting from the discrete nature of the flow.


Author(s):  
Dongmei Wang ◽  
Jin Zhang ◽  
Raymond Butler ◽  
Adam Clark ◽  
Rachel Rabun ◽  
...  
Keyword(s):  

2014 ◽  
Vol 378 (18-19) ◽  
pp. 1281-1285 ◽  
Author(s):  
Guo-Cheng Yang ◽  
Qi-Yi Liu ◽  
Mao-Bin Hu ◽  
Rui Jiang ◽  
Qing-Song Wu

2021 ◽  
Vol 6 (3) ◽  
pp. 33-40
Author(s):  
V. A. Shishkov

increasing the efficiency of the power plant. A method of controlling the supply of cryogenic fuel to a gas turbine engine is to pump its liquid phase, followed by its separation into two parts and controlling the flow rate of each part. Heated the first part of the cryogenic fuel to a gaseous state in the heat exchanger, mixing it with the second part and feeding the resulting mixture of cryogenic fuel into the combustion chamber. The first part of the cryogenic fuel flow rate is passed through the heat exchanger Gta = Gsm [Ср_sm (Тfp + T) il] / [ig il], where Gsm is the consumption of cryogenic fuel at the outlet of the mixer, Ср_sm is the isobaric heat capacity of cryogenic fuel at the outlet from the mixer, Тfp is the temperature of the phase transition of cryogenic fuel from liquid to gas at a pressure in the mixer, T is the temperature of the gas mixture of cryogenic fuel at the outlet of the mixer above the temperature of the phase transition, il is the enthalpy of the first part of the liquid phase of cryogenic fuel at the input ode to the heat exchanger and the second part of the liquid phase of the cryogenic fuel, which is fed to the second entrance to the mixer, ig is the enthalpy of the gaseous phase of the cryogenic fuel at the outlet of the heat exchanger, at which it is fed to the first entrance to the mixer. Moreover, ig Ср_sm (Тfp + T) il and Gsm = Gta + Gl, where Gl is the flow rate of the second part of the liquid phase of the cryogenic fuel, which is fed to the second input to the mixer. When the pressure of the cryogenic fuel in the mixer is below the critical value Pkr, the temperature Тfp of the phase transition from liquid to gas of the cryogenic fuel is taken equal to the temperature Тnas on the saturation line of the cryogenic fuel at the corresponding pressure in the mixer. The excess of the temperature of the cryogenic fuel mixture over the phase transition temperature after mixing the gas and liquid phases at the mixer outlet sets T = 60 ... 170 for cryogenic methane and T = 150 ... 260 for cryogenic hydrogen. Due to the gasification of a part of the cryogenic fuel consumption in the heat exchanger and subsequent mixing of this part with the second liquid part of the cryogenic fuel in the mixer, the freezing of the outer surface of the heat exchanger in all operating modes of the power plant is reduced. Due to the reduction of external freezing of the channels of the heat exchanger, the heat transfer efficiency is increased in it. By reducing the dimensions of the heat exchanger, the hydraulic losses in the gas-dynamic path of the power plant are reduced, which, in turn, increases its efficiency. By lowering the temperature of the gas phase of the cryogenic fuel at the inlet to the combustion chamber, the temperature of the exhaust gases at its outlet is reduced, which, in turn, increased the reliability of the gas turbine of the power plant. The method of operation of the cryogenic fuel supply system is intended for ground-based power plants and vehicles. The work is intended for scientists and designers in the field of cryogenic fuels for internal combustion engines.


2018 ◽  
Vol 335 ◽  
pp. 147-155 ◽  
Author(s):  
Jiangfeng Wan ◽  
Fugang Wang ◽  
Guanghui Yang ◽  
Sheng Zhang ◽  
Mengke Wang ◽  
...  

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 756 ◽  
Author(s):  
Lu ◽  
Hu ◽  
Qi

Fire prevention and extinguishing and CO2 sequestration in coal mine gob require continuous transportation of liquid CO2 in pipelines with large height difference (from ground to underground). However, the temperature and pressure variation of liquid CO2 in pipelines with large height difference is still unclear, which hinders the design of a liquid CO2 pipeline transportation system. The influence of pipe diameter and inlet parameters (temperature and pressure) on the variation of temperature and pressure of liquid CO2 along the 1000 m vertical pipeline was studied in this paper. The study found that for each pipeline diameter considered there existed a range of flowrates where safe flow conditions could be ensured, at which no phase transition occurs throughout the length of the pipeline. When the transporting flow is larger than the maximum limit flow, phase transition occurs dramatically, which will lead to a sudden drop in temperature and pressure. When the transporting flow rate is lower than the minimum limit flow rate, phase transition of CO2 occurs slowly along the pipeline. According to the requirement of underground fire prevention and extinguishing for transporting flow rate and the economic cost of the pipeline system, the optimum diameter is 32 mm, and the corresponding safe transporting flow range is 507–13,826 kg/h. In addition, when the inlet pressure is constant, if the inlet temperature is too high, phase transition of CO2 occurs dramatically at the entrance. For a 1000 m vertical pipe with diameter of 32 mm, when the inlet pressure is 14 bar, 16 bar, 18 bar, 20 bar, 22 bar, 24 bar, the corresponding maximum allowable inlet temperatures are −30 °C, −26 °C, −23 °C, −19 °C, −16 °C and −13 °C, respectively. This research has significant guidance for safety transportation scheme of liquid CO2 from coal mine surface to underground.


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