Advanced Materials Research Vols. 250-253

Abstract: The layout of district cooling pipeline network is a typical combinational optimization problem. Taking the minimum annual total cost of pipeline network as the optimization target, this article applied the single parent genetic algorithm in optimum arrangement of aqueous cooling system pipe network of the First Energy Station in Shanghai Expo Park, which has given a scheme of arrangement with minimum tentative investment and operation cost to provide basis for scheme assessment and decision-making. The study shows that the application can provide not only many optimal arrangements for pipe network which has the same refrigeration station to make basis for scheme assessment and decision-making, but also the basis for choosing the best position of refrigeration station.

Abstract: The relationship between surface crack tip stress intensity factor and calculated parameters of pavement structure is discussed and finite element models based on the fracture mechanics theory is created. From the study in this paper, the following conclusions can be drawn: As the load increases, stress intensity factor will decrease, and it may promote spread of the crack. Surface layer modulus has a great influence on stress intensity factor. In the condition of the same crack depth, stress intensity factor increases while surface layer modulus increases, stress intensity factor decreases gradually while the thickness of the surface layer increases. As base layer modulus increasing, stress intensity factor of surface layer decreases. With the increase of the modulus of subbase layer, stress intensity factor of surface layer decreases gradually. The earthen foundation module has a little big influence. With the increase of the earthen foundation module, stress intensity factor will decrease, so it can delay the appearance of the crack.

Abstract: Numerical simulation is an essential tool for investigation of seawater intrusion in coastal aquifer. For most groundwater modeling software, boundary condition along the beach is required. But it was normally assumed due to the uncertainty in the seawater – freshwater interface. Using FEFLOW, a groundwater simulation software based on finite element method, we investigated the intrusion scope and the exiting point of groundwater outflow under various boundary conditions. Seven cases were designed, among which three cases with boundary conditions of a freshwater layer over seawater, three cases with a triangle freshwater zone between seawater and the beach, and the last one without freshwater at the seawater boundary. Results showed that the last case has the longest intrusion scope. The scope of seawater intrusion is determined by both the horizontal water head gradient along the bottom of the aquifer and the vertical water head gradient along the beach. Both higher horizontal gradient and lower vertical gradient result in larger intrusion scope. In some circumstances, the vertical gradient has greater impact on seawater intrusion than the horizontal gradient, and act as the main power inhibiting seawater intrusion.

Abstract: Indoor air quality has an important impact on human health.In order to find out indoor air quality (IAQ) condition at the waiting room in Guilin Lingui bus station, in the survey, the waiting room IAQ had been investigated with the carry-home fast inspect instrument from Dec 20^th to Dec 30^th in Lingui Bus Station. The levels of CO₂, formaldehyde(HCHO), particles with diameters of 10 um or less(PM₁₀) and total volatile organic compound(TVOC) had been inspected mostly. Data were analyzed by the SPSS 11.0 and evaluated with synthetic index method of air quality. Results showed that CO₂ concentration was biggest to 878 ppm(standard limit of 1000ppm), PM₁₀ concentration was biggest to 0.14mg/m³(standard value of 0.15 mg/m³), HCHO concentration was biggest to 0.08 mg/m³(standard value of 0.10 mg/m³). The concentration of other pollutants were lower comparatively. The winter air quality of the waiting room in Lingui bus station belongs to the no pollution. It showed that the levels of indoor pollutant were higher than outdoors', too.

Abstract: A method for simulating heat recovery systems using AirModel in implementations of the ASHRAE simplified energy analysis procedure was developed in this paper. AirModel, a simulation tool used to simulate the energy consumption of building heating, ventilating, and air-conditioning (HVAC) systems, was developed by the Energy Systems Laboratory (ESL) at Texas A&M University (TAMU) in the 1990’s. This program is capable of simulating single duct reheat systems and dual duct systems with economizer cycles. However, in certain buildings, energy savings techniques such as heat recovery systems are implemented but AirModel does not have a specific input to simulate this system. Presented in this paper is a method to simulate a heat recovery system using AirModel. An example of this methodology was used to simulate the HVAC system with a heat recovery system for the Biophysics and Biochemistry building on the TAMU campus.

Abstract: The energy efficiency reformation of existing buildings is a very complicated system which is controlled by lots of factors. It is very important content of the energy efficiency reformation work. The evaluation system for energy efficiency reformation of existing buildings is established. The value assignment method is proposed and the rating standard is established. Based on matter-element theory and dependent function, the extension theory is applied to evaluate the effect of energy efficiency reformation of existing buildings, and the extension method for the effect evaluation is proposed. Taking a real project of energy efficiency reformation for example, based on the reasonable selection of evaluation factor, an extension model for evaluation is built. As a result, it is practical and feasible to apply the extension method to solve this kind of problems.

Abstract: Rail transit hub is key node in urban transportation system. The study on properties of ventilation and smoke control system can improve response ability in case of fire and give ventilation and smoke control design guidance for underground rail transit hub. Take Beijing DongZhimen underground rail transit hub as research object, according to its air turbulent flow characteristics, introducing standard turbulence model based on the N-S equation. Build the computational fluid dynamics model for solving the flow field within underground rail transit hub. Through theoretical analysis and numerical simulation, take "Siamese model” results as the boundary condition and establish a mathematical model of rail transit hub with CFX. Then research fire smoke development and spread laws when the exhaust fan within underground rail transit hub delayed open.

Abstract: This paper presents researches on the technique for testing water content and moisture field in concrete by GPR. Through the experiments, a discussion has been carried out on the variation of velocity of radar waves and the relative dielectric constants in the concrete with different water content. Comparing the results of air drying and drying experiment, an equation is given to reflect the relation between the water content in the concrete and the radar speed of radar waves in the concrete, also the relative dielectric constants of concrete. Some suggestions are proposed for the actual concrete water content test by using Ground Penetrating Radar (GPR).

Abstract: The typical subway island-platform of Beijing as research object was present in the article. Taking two-equation turbulence model and giving boundary conditions of piston wind and train heat load change with the time, adopting numerical method simulates air distribution of air-conditioning and ventilation system in subway. The results indicate that piston wind effect has significant impact on the area of platform entrance and staircase entrance while station with safety doors can obstruct piston effect at a certain degree. Simultaneity, the supply- exhaust air system offers relatively uniform temperature and velocity field, which meets requirements of transitory comfort for passengers. It is found that numerical simulation method can simulate and forecast air distribution of air conditioning and ventilating system in subway station. In conclusion, it can provide the reference for optimizing air-conditioning and ventilation system, improving thermal environment designing of subway station.

Abstract: A numerical analysis for the progressive collapse of a reinforced concrete frame caused by an explosion in this structure’s basement is presented in this paper. The whole process from the detonation of the explosive charge to the complete demolition is reproduced. The main work is focused on the role of soil in structural collapse and failure mode of structural members. The analysis is simulated using ANSYS/LS-DYNA and proposes a new simulation method which is comparatively accurate and economic.