scholarly journals Crystallization Behavior of Ammonium Chloride in High-Pressure Heat Exchanger of Hydrotreating Unit

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Jianwen Zhang ◽  
Fan Zhang ◽  
Yan Li ◽  
Yahui Zhao ◽  
Gang Sheng
Keyword(s):  
Mass Transfer ◽  
High Pressure ◽  
Heat Exchanger ◽  
Ammonium Chloride ◽  
Volume Fraction ◽  
Flow Direction ◽  
Corrosion Cracking ◽  
Inlet Temperature ◽  
Corrosion Failure ◽  
Chloride Deposition

In view of the corrosion failure of a high-pressure heat exchanger in a diesel hydrogenation unit, the formation mechanism of ammonium chloride in a multiphase flow system is investigated in this article. Numerical simulation is carried out by user defined function (UDF) on the process of adding source of mass transfer in computational fluid dynamics (CFD) solvers. The distribution characteristics of ammonium chloride are illustrated by the parameters including crystallization temperature of ammonium chloride, volume fraction of ammonium chloride, and mass transfer rates of NH3 and HCl, and the causes of corrosion cracking in the U-shaped bend of the heat exchanger are discussed. The results show that there is a great risk of ammonium chloride deposition in the heat exchanger from 4.5 m away from the outlet of the second pass. The crystallization area in the tube gradually expands from the wall to the center along the flow direction, and the crystallization rate is higher near the tube wall. The field sampling test results show that the corrosion cracking is hydrogen-induced cracking, which is due to the existence of large amount of hydrogen, high impacting force, excessive flow rate, and the risk of ammonium chloride particle erosion at the U-bend. In order to alleviate the corrosion of ammonium chloride deposition, some improvement measures are put forward, such as raising the inlet temperature of the tube side to 215 °C and increasing the water injection by 30%, which play an important role in decreasing the formation of ammonium chloride in the heat exchange system.

scholarly journals Analysis of Multiphase Flow and Heat and Mass Transfer for Ammonium Chloride Crystallization of the High-Pressure Heat Exchanger in Hydrogenation Unit

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7754
Author(s):  
Jianwen Zhang ◽  
Yahui Zhao ◽  
Yan Li ◽  
Fan Zhang
Keyword(s):  
Mass Transfer ◽  
High Pressure ◽  
Heat Exchanger ◽  
Multiphase Flow ◽  
Gas Phase ◽  
Heat And Mass Transfer ◽  
Ammonium Chloride ◽  
Tube Bundle ◽  
Corrosion Failure ◽  
Petrochemical Enterprise

The corrosion failure of the high-pressure heat exchanger in a petrochemical enterprise was simulated. A multiphase flow and heat and mass transfer simulation shows that the vortex core with a higher gas phase content and lower temperature is the region of easy crystallization, located on both sides of the center of the tube. The crystallization process occurs in the gas phase. As the reaction progresses, the crystallization range spreads from the tube wall to the center of the tube bundle, and the inner diameter of the tube bundle decreases continuously. In Fluent, a user-defined function, based on the ammonium chloride crystallization reaction, is loaded. The results show that crystallization first occurs in the tube bundles on both sides of the center of the tube and that the corrosion is aggravated by the erosion wall surface of crystal particles at the elbow, which is consistent with the actual corrosion failure location.

A study on the corrosion failure induced by the ammonium chloride deposition in a high-pressure air cooler system

2020 ◽  
Vol 112 ◽  
pp. 104529
Author(s):  
Xiaofei Liu ◽  
Aoqiang Duan ◽  
Jianxun Quan ◽  
Haozhe Jin ◽  
Chao Wang
Keyword(s):  
High Pressure ◽  
Ammonium Chloride ◽  
Corrosion Failure ◽  
Air Cooler ◽  
Chloride Deposition

Turbulent flows in a spiral double-pipe heat exchanger

2019 ◽  
Vol 30 (1) ◽  
pp. 39-53 ◽  
Author(s):  
Zhe Tian ◽  
Ali Abdollahi ◽  
Mahmoud Shariati ◽  
Atefeh Amindoust ◽  
Hossein Arasteh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulent Flows ◽  
Heat Exchangers ◽  
Volume Fraction ◽  
Inlet Temperature ◽  
Content Type ◽  
Tube Heat Exchanger ◽  
Double Pipe ◽  
Pipe Heat

Purpose This paper aims to study the fluid flow and heat transfer through a spiral double-pipe heat exchanger. Nowadays using spiral double-pipe heat exchangers has become popular in different industrial segments due to its complex and spiral structure, which causes an enhancement in heat transfer. Design/methodology/approach In these heat exchangers, by converting the fluid motion to the secondary motion, the heat transfer coefficient is greater than that of the straight double-pipe heat exchangers and cause increased heat transfer between fluids. Findings The present study, by using the Fluent software and nanofluid heat transfer simulation in a spiral double-tube heat exchanger, investigates the effects of operating parameters including fluid inlet velocity, volume fraction of nanoparticles, type of nanoparticles and fluid inlet temperature on heat transfer efficiency. Originality/value After presenting the results derived from the fluid numerical simulation and finding the optimal performance conditions using a genetic algorithm, it was found that water–Al2O3 and water–SiO2 nanofluids are the best choices for the Reynolds numbers ranging from 10,551 to 17,220 and 17,220 to 31,910, respectively.

scholarly journals Research on High-Pressure Hydrogen Pre-Cooling Based on CFD Technology in Fast Filling Process

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2208
Author(s):  
Sen Li ◽  
Jinxing Guo ◽  
Xin Lv ◽  
Teng Deng ◽  
Bo Cao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Transfer Process ◽  
Volume Fraction ◽  
Cooling System ◽  
Operating Cost ◽  
Heat Transfer Process ◽  
Inlet Temperature ◽  
Filling Process ◽  
Pressure Hydrogen

In the fast filling process, in order to control the temperature of the vehicle-mounted storage tank not to exceed the upper limit of 85 °C, it is an effective method to add a hydrogen pre-cooling system upstream of the hydrogenation machine. In this paper, Fluent is used to simulate the heat transfer process of high-pressure hydrogen in a shell-and-tube heat exchanger and the phase change process of refrigerant R23. The accuracy of the model is proven by a comparison with the data in the references. Using this model, the temperature field and gas volume fraction in the heat transfer process are obtained, which is helpful to analyze the heat transfer mechanism. At the same time, the influence of hydrogen inlet temperature, hydrogen inlet pressure, and refrigerant flow rate on the refrigeration performance was studied. The current work shows that the model can be used to determine the best working parameters in the pre-cooling process and reduce the operating cost of the hydrogen refueling station.

scholarly journals Numerical Exploration of Influence of Phase Changing Material in Heat Transfer Augmentation in the Double Tube Heat Exchanger

2018 ◽  
Vol 7 (3.27) ◽  
pp. 162
Author(s):  
C Gnanavel ◽  
R Saravanan ◽  
M Chandrasekaran
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Volume Fraction ◽  
Heat Transfer Fluid ◽  
Storage Device ◽  
Liquid Volume ◽  
Inlet Temperature ◽  
Transition Flow ◽  
Liquid Volume Fraction ◽  
Tube Heat Exchanger

The double tube heat exchanger is a device in which the inner tube carries the hot fluid.  Phase Changing Material is the energy storage device is used for Solar heater applications to maintain the constant temperature, in the present study of this work is CFD Analysis of plain tube heat exchanger with Phase Changing Material (PCM) and without Phase Changing Material (PCM), Charging time, liquid volume fraction with the various Heat Transfer Fluid (HTF) inlet temperature 70, 75, 80 deg Celsius and various flow conditions of laminar flow of 2000 Re, Transition flow of 4000 Re and Turbulent flow of 10,000 Re  

Analysis on the corrosion failure of U-tube heat exchanger in hydrogenation unit

2021 ◽  
pp. 105448
Author(s):  
Xiaofei Liu ◽  
Haiyan Zhu ◽  
Chenyang Yu ◽  
Haozhe Jin ◽  
Chao Wang ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Corrosion Failure ◽  
Tube Heat Exchanger

scholarly journals Numerical and experimental investigation of alumina-based nanofluid effects on double-pipe heat exchanger thermal performances

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
A. Bendaraa ◽  
My. M. Charafi ◽  
A. Hasnaoui
Keyword(s):  
Heat Exchanger ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Deionized Water ◽  
Comsol Multiphysics ◽  
Exchange Coefficient ◽  
The Subject ◽  
Double Pipe ◽  
Pipe Heat ◽  
Thermoelectric Power Plant

AbstractIn this study, we investigate the thermal behaviour of nanofluids in a double-pipe heat exchanger. It is about a counterflow configuration, designed to cool a lubrication unit of a thermoelectric power plant. The subject of this work is to evaluate the thermal performances of the exchanger by using a nanofluid based on alumina suspension comparing with deionized water. In order to evaluate the thermal performance of the studied configuration, we carried out numerical experiments in an application developed on COMSOL Multiphysics environment, these experiments are utilized to show the feasibility of this application. As result, we found that the nanofluid with an increase in its volume fraction leads to an increase in the overall exchange coefficient, the convective heat transfer coefficient, as well as the efficiency and the power of the exchanger. It is noted that an increase of 1% in volume fraction, can enhance the overall exchange coefficient, the power and the effectiveness of the exchanger by 17.62%, 1.473% and 10.80% respectively. Besides, it is noted that the increase in the concentration of nanofluids leads to a narrowing of the pinch points of the inlet and outlet temperatures, which means that nanofluids are more efficient in cooling temperatures than conventional fluids.

CFD-based structure optimization of plate bundle in plate-fin heat exchanger considering flow and heat transfer performance

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yao Li ◽  
Haiqing Si ◽  
Jingxuan Qiu ◽  
Yingying Shen ◽  
Peihong Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Field Performance ◽  
High Specific Surface Area ◽  
Calculation Model ◽  
Air Separation ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency

Abstract The plate-fin heat exchanger has been widely applied in the field of air separation and aerospace due to its high specific surface area of heat transfer. However, the low heat transfer efficiency of its plate bundles has also attracted more attention. It is of great significance to optimize the structure of plate-fin heat exchanger to improve its heat transfer efficiency. The plate bundle was studied by combining numerical simulation with experiment. Firstly, according to the heat and mass transfer theory, the plate bundle calculation model of plate-fin heat exchanger was established, and the accuracy of the UDF (User-Defined Functions) for describing the mass and heat transfer was verified. Then, the influences of fin structure parameters on the heat and mass transfer characteristics of channel were discussed, including the height, spacing, thickness and length of fins. Finally the influence of various factors on the flow field performance under different flow states was integrated to complete the optimal design of the plate bundle.

Temperature Transients in a Triple Heat Exchanger

1984 ◽  
Vol 198 (3) ◽  
pp. 145-154
Author(s):  
P C Chiu ◽  
E H K Fung
Keyword(s):  
Heat Exchanger ◽  
Nuclear Reactor ◽  
Reactor Power ◽  
Solar Heating ◽  
Inlet Temperature ◽  
Exchange Processes ◽  
Flow Experiments ◽  
Heating Plant ◽  
Reactor Power Plant ◽  
Secondary Fluid

A triple heat exchanger, so called because there are three heat exchange processes taking place in it, was built to simulate the system behaviour of a nuclear reactor power plant or a solar heating plant which is characterized by the two circulating loops of the fluid flow. Experiments were carried out to study the temperature transients under disturbances in secondary fluid inlet temperature and power output from immersion heaters. Numerical results were obtained from the weighted residual formulation of the proposed dynamic model and they were shown to be in general agreement with the two sets of experimental responses.

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