Advanced Materials Research Vols. 1008-1009

Abstract: The effect of the volumetric flow rate on the heat transfer of shell and tube heat exchangers was investigated. Furthermore, a comparison of four flow models using for numerical simulation was discussed to provide improved predictions of turbulent flow in the shell and tube heat exchangers. Four flow models tested were Reynolds stress model, k-ε Standard model, k-ε RNG model and k-ε Realizable model, respectively. Multi reference frame technique was used with Fluent software package. During the numerical simulation, the heat dissipation was shown to be strongly dependent on the choice of turbulence model. Compared with the cold model experimental result, k-ε RNG model was a better turbulence model for the prediction of the heat dissipation in the shell and tube heat exchangers among the four models. Furthermore, the good agreement between the numerical results and the experimental result confirmed the validity of the numerical method.

Abstract: In pipeline transportation, hydraulic resonance is a particular fluid transient phenomenon, which maybe produces high surge pressure. Especially with air cavity being trapped in liquid pipeline, so must be avoided. However, this behavior may be used to prompt flow vibration to enhance the surge pressure for some special purposes, for example, pulsed water jet, water cannon, and so on. Based on this viewpoint, an approach of making use of the air-liquid hydraulic resonance in a pipe connected with an air-chamber to generate high pressure is put forward. The mathematic model of the system is established and numerically simulated. It is shown that, under some certain conditions, hydrodynamic resonance can take place because of the air-liquid transient, so the pipe outlet jet pressure can be enhanced remarkably.

Abstract: Three liquid-gas separator units were designed and manufactured from transparent acrylic resin based on the concept of a new kind of validated high performance condenser. The separator units had different spaces between baffle and outlet arm or different header diameters. A visualization cold state test system was set up to explore the basic principle of liquid-gas separation and liquid discharge process, using air and water as the working fluids. Four kinds of liquid flow patterns were observed by the liquid staining and high-speed photography at inlet air superficial velocities from 1m/s to 15m/s and water superficial velocities from 0.0015m/s to 0.06m/s. The effects of operation conditions and structure parameters on the separation efficiency of the liquid-gas separator units were investigated. The results showed that under the experimental conditions, the separation efficiency was more than 70%, the separation efficiency could be improved by increasing the space between baffle and outlet arm as well as the header diameter.

Abstract: In this paper, the heat transfer rate of parallel flow heat exchanger was obtained in the condition of non-uniform flow distribution by 3D numerical simulation. The maximum theoretical heat transfer rate of parallel flow heat exchanger was obtained through 1D calculation. Ultimately, the correlation of the influence of non-uniform flow distribution on heat transfer efficiency was obtained by the comparative analysis of non-uniform flow distribution and heat transfer efficiency and regression calculation. It was found that the forecasted heat transfer efficiency error of correlation was within 2%.

Abstract: The application of soot-blower is the primary means for solving the fouling and slagging of coal-fired boilers. And appropriate soot-blowing will greatly improve the efficiency of boilers. Therefore, selecting the appropriate type of soot-blower is surely important. This paper analyzes the working principle, technical characteristics, and application scope of steam soot-blowers, gas pulse shock soot-blowers, acoustic soot-blowers and air shock soot-blowers which are common in boilers. It raises a proposal that different types of soot-blowers should be used in different positions of boilers.

Abstract: The heat transfer device with lead and bismuth is one of the most important equipment to ensure the safe operation of the loop. Though the analysis of sleeve type heat exchange’s flow heat transfer situation, we will get when the lead and bismuth working in the certain circumstance, different thickness of pipe wall, different cooling conditions, have different influence on the heat transfer and thermal stress. When the water side condition is in certain circumstance, as the thickening of the tube wall and the increasing of wall thermal stress,, thin wall can reduce thermal resistance and thermal stress, but faced the corrosion of lead and bismuth at the same time,. Under the condition of the same thickness of the wall, water with higher pressure and temperature can reduce thermal stress, but because of low temperature difference, the economy of heat transfer device is not good. So, in the design of lead bismuth-heat transfer device, we should fully take into account the influence of water side parameters.

Abstract: The flow regime and water evaporation outside horizontal tube are the important factors reflecting the heat transfer. In this paper, under different wind speed, the water film flowing and air moisture are studied for some spray density and different diameter. The results shows that there is a wind threshold with air velocity increased, the water film thickness decrease along the annular angles and then increase, and reaches the minimum at about 120 °, air moisture content decreases first and remains unchanged after a certain distance from the tube wall, the greater the wind speed , the thicker the water film, the faster water evaporation, the more the amount of water vapour taken away by air velocity increased, air moisture content decreases on the same position.

Abstract: A multi-point low-pressure methanol injection system was installed on manifold of a four cylinder turbocharged diesel engine, and the experiments on the engine operated with intake premixed methanol were conducted under wide operating conditions. The influence of the engine operating conditions on premixed methanol quantity was analyzed. The results show that, compared with straight diesel model, premixed methanol prolongs the ignition delay time of pilot diesel at the engine high load with low speed, and more methanol quantity can be premixed. At more than medium load with high speed, diesel ignition delay time with premixed methanol is shorter than with straight diesel model, and substitution ratio of methanol for diesel is significantly lower than that of low speed. Compared with the straight diesel mode at high speed, the fuel economy of the dual fueling mode is better, and NOx and soot emissions also are decreased, but CO and HC emissions are increased.

Abstract: It takes the C26:33L6 engine as an example to simulate the LNG vaporization system on LNG powered ships. It establishes the dynamic mathematical model of the three-way valve, the vaporizer, the heater and the heat exchanger in LNG vaporization system. Then, the simulation model was established based on MATLAB. At last, it analyzes the LNG temperature at the heater outlet under different loads using the PID control in order to make LNG temperature stable to the engine.

Abstract: It presents the compressor gas-cooler of a 300 MW Oxy-fuel pulverized coal fired boiler and established the simulation model of the cooler by the mechanism analysis method. On the simulation platform, the heat transfer performance and dehydration properties of cooler are studied on different pressure conditions. The simulated experiments show that when the flue gas inlet pressure is greater than the design pressure, with the increase of pressure, heat exchange performance of gas-cooler will declines; the water separation amount increases initially and then decreases subsequently.