Advanced Materials Research Vols. 732-733

Abstract: Enhanced Geothermal Systems represent a series of technology, which use engineering methods to improve the performance of geothermal power plant. In some geothermal fields, the rocks are in high temperature but a low permeability, or the subsurface water is scarce. In these geological conditions, cool water was injected into the geothermal wells to fracture the tight rock and create man-made reservoir for thermal exploitation. Furthermore, these engineering methods can be utilized to improve the productivity of pre-existing hydrothermal power plants. To save water and treat the global warming, using carbon dioxide instead of water as working fluid was proposed. Numerical simulation reveals that the carbon dioxide has numerous advantages over water as working fluid in the heat mining process. The precipitation caused by carbon dioxide will restore part of carbon dioxide in the rock and reduce the micro-seismicity risk.

Abstract: High temperature corrosion of metal material was found on the side water-walls of a swirl-opposed firing supercritical boiler. The gas atmosphere near the side wall has great relationship with the high temperature corrosion. Test holes were installed on the side walls to form an experimental system. The gas compositions near the side walls were analyzed under different combustion conditions. High CO concentration is detected near the side walls. The effects of the operation states of burners on the CO concentration near side walls were tested. High over-fire air quantity results in strong reducing atmosphere of the test area. The adjusting method to control the atmosphere is suggested.

Abstract: In this paper, effects of the vortex tube hot end lengths on the performance are studied, using a three-dimensional numerical fluid dynamic model. The hot end and cold end structure of vortex tube adapts the conical tube with the dilated side connecting a straight pipe. Structural mesh is employed. Different turbulence models are used, compared with experiment, considered of convergence and computing time, eventually, SST model is applied. In contrast to experimental data, numerical results are acceptable. By numerical analysis, it is observed that as the length of hot ends increases, the performance of energy separation increases significantly. However, while the length diameter ratio is more than 20, the performance does not increase any more. Even, it begins to decrease. Meanwhile, different hot end lengths flow is compared, and attemptable analysis is conducted to the flow phenomenon.

Abstract: A microscale ceramic tube was used as a burner jet, and a coaxial jet flame was established in the confined space between the ceramic tube and the outer quartz glass tube. The effects of gravity on the small jet flame characteristics in the confined space were investigated numerically. Comparisons between the experimental data and the numerical data showed that characteristics of the small jet flame structure and temperature field were in good agreement. It verified the accuracy of the numerical simulation. Numerical simulations of flame characteristics at zero gravity level were performed. The results show that the gravity level has a greater influence on the flame width than that on the flame length. The chemical reaction rate is larger under the condition of normal gravity than that of zero gravity.

Abstract: O₂/CO₂ combustion technology is an effective method to capture and store coal-fired boiler flue gas CO₂. With a 300MW subcritical pulverized coal boiler as the research subject investigated, Fluent numerical simulation software is used to simulate the process of pulverized coal combustion both in air and O₂/CO₂ conditions. The comparative analyses are made both in the former conditions, such as the combustion characteristics of pulverized coal, the influence of oxygen volume fraction, the effect of the secondary air temperature on the temperature field in the furnace of pulverized coal boiler. As for the following results of the pulverized coal combusted in the O₂/CO₂ condition, compared with the results in the air condition, its time of ignition is delayed, and the combustion temperature is low and the central position of flame rises. With the increasing percentage of the oxygen volume and the rising temperature of secondary air, the time of ignition speeds up, which improves the overall furnace temperature level and transferring capability of the radiation heat.

Abstract: Based on test principle of ground penetrating radar (GPR), the application feasibility for detecting the heating pipelines on complex highway is verified. In accordance with the complex highway in Wangjing region of Beijing city in China, by using ground penetrating radar of SIR-20 to monitor the geological situation of construction surface, the plain position of pipeline and the buried depth, the detection shows that: the objects of bigger relative dielectric constant absorbs the electromagnetic wave signal from periphery; the maximum intensity of reflection radar wave appears at the top of pipeline; the arc width in radar wave image produced by the bottom of pipeline is bigger than the top. Based on these studies, the design program and accident removal countermeasures for the detection of complex highway pipeline are proposed. Meanwhile, combining with actual measurement in field, contrives scheme utilizing ground penetrating radar to detect heating pipelines. It could be verified the feasibility of testing heating pipelines with ground penetrating radar, provides a basis for the subsequent security dynamic construction design, and accumulates some experience for ground penetrating radar detecting pipeline on complex highway.

Abstract: Wind speed was an important impact factor when simulating the cooling tower plume dispersion. The SACTI model was selected in this paper and this model was used to predict the plume dispersion character discharging from cooling tower under normal operation and three different kinds of wind speeds. The three kinds of wind speeds were 2 m/s, 4 m/s and 6 m/s and it was analyzed that the plume character under these three wind speeds. Results showed that the plume length, plume height and plume radius will present different change trend when wind speed changed.

Abstract: for hot pipeline, on the base of taking the influence from the constant temperature of the earths layer and air cyclic variation in year into account, the thermal calculation mathematics models of steady operation in different laying way were established and the test method was introduced, which were verified to be right by the temperature at inlet and outlet of heating stations. Bing compared experiment data with test data, all the errors were less than 3%, which can meet the demand of project and it verified the models to be right.

Abstract: A grey box model of screw ground source heat pump unit has been established and operating characteristics of the unit using R22 refrigerants were simulated. The effects on refrigerating capacity, heating capacity, power consumption of the compressor and COP on conditions of cooling and heating have been analyzed with different inlet water temperature of evaporator and inlet water temperature of condenser. Results show that main factor which affecting COP of heat pump unit is inlet water temperature of condenser. The change of refrigerating capacity and heating capacity are mainly caused by inlet water temperature of evaporator. Measures can be done to decrease the inlet water temperature of condenser when the unit operates for a long time and to increase inlet water temperature of evaporator on very hot or very cold conditions.

Abstract: This paper presents a new scheme of distributed pump-system for district heating network. As no circulating pumps for the heat sources and no throttle valves for the users, much energy is saved. And the control of hydraulic parameters can be adjusted without interfering with that of the thermodynamic parameters. The novel scheme is available for both looped pipeline networks (LPNs) with multiple heat sources and dendritic pipeline networks (DPNs) with single heat source. Moreover, for users located at the hydraulic intersection points of the looped pipe network with multi-heat sources, their water temperature can be less affected by their own water consumption. A case study was presented and about 22% power saved when the new scheme was employed.