Applied Mechanics and Materials Vols. 90-93

Abstract: Based on the risk type classification of model development project, the paper used the analytic hierarchy process (AHP) method, established a AHP risk assessment model of development project, and described the risk assessment idea.

Abstract: This study reviews some published literatures to survey the recent research on indoor environment quality and building energy consumption. The indoor environment quality is categorized and defined as different indices and variables. The building energy consumption can be determined by ventilation rates, thermal comfort, adaptive thermal comfort, neutral temperature, set-point temperature, indoor air quality, air velocity, and non-occupied hours. Various climates or regions such as subtropical climates in Hong Kong, Italy, three climatic zones in Greece, hot and dry climates in Africa, hot and humid climate in Thailand, are contained. The building types include office buildings, commercial buildings and school buildings, and the data can be obtained from a simulation model or the field database. It can be concluded that the indoor environment quality has a significant influence on the building energy consumption, and a validated thermal model is be a practical tool to investigate the effect of the indoor environmental parameters.

Abstract: Indoor environment quality can be used to rank the building performance. Environmental parameters involve operative or room temperature, predicted mean vote, predicted percentage of thermally satisfied, predicted percentage dissatisfied, air velocity, relative humidity, indoor air quality and so on. One or more parameters can be possible to establish a corresponding range for building classes. Average CO₂ concentration level can be used as the index of indoor air quality to measure the office buildings or public places. Various authors in different climates or zones proposed different baseline for building grades. It should be develop a scientific methodology or evaluation system to give the convincing classification and explanation.

Abstract: The optimal performance of an absorption refrigerator operating between four temperature levels with the losses of heat resistance and internal irreversibility is analyzed first by taking the total heat transfer area of heat exchangers as an objective function. The minimum total heat transfer area is described in terms of the rate of the entropy changes of four heat reservoirs, and the generally optimal relation among the cooling load, the coefficient of performance and total heat transfer area is achieved. Then, an ecological optimization criterion is proposed for the best mode of operation of the absorption refrigerator. We investigate the ecological optimization performance and derive the corresponding cooling load, coefficient of performance and entropy production rate at the maximum ecological criterion for the absorption refrigerator. A comparison of an absorption refrigerator performance under maximum ecological function and maximum cooling load conditions is presented. Effects of the cycle parameters on the ecological performance have been discussed.

Abstract: Steam stimulation is one of the main methods used in heavy oil reservoir development. How to inject high temperature and high dryness steam is a key factor to enhance heavy oil recovery. It is significant to evaluate heat transfer of steam pipeline and optimize thermal insulation layer for heavy oil exploitation. Based on fluid mechanics, heat transfer theory, considered phase change, mathematical model to calculate heat transfer and heat loss of steam pipeline was derived. Using COMSOL Multiphysics, a finite element based program for simulating unlimited multiphysics and single physics applications, the author simulated heat transferring in ground steam pipeline and analyzed the effect of thermal insulation layer. From the simulation results, it was known that, (1) Along with the pipeline distance increases, the steam dryness decreases, the decrease rate decreases with the distance increases. (2) At the same transmission distance, the bigger the thermal insulation layer thickness is, the smaller the heat loss of the steam is. The heat loss of steam transmission mainly center on the first half pipeline. (3) With the thickness of thermal insulation layer increases, the heatloss declines. After the thickness of thermal insulation layer increases 90 mm, increasing the thickness has no obvious effect on reducing the heat loss. So, it is suggested that the thermal insulation layer thickness should be 75-80mm.

Abstract: The increasing performance demands and the growing complexity of heating, ventilation and air conditioning (HVAC) systems have created a need for automated fault detection and diagnosis (FDD) tools. Cost-effective fault detection and diagnosis method is critical to develop FDD tools. To this end, this paper presents a model-based online fault detection method for air handling units (AHU) of real office buildings. The model parameters are periodically adjusted by a genetic algorithm-based optimization method to reduce the residual between measured and predicted data, so high modeling accuracy is assured. If the residual between measured and estimated performance data exceeds preset thresholds, it means the occurrence of faults or abnormalities in the air handling unit system. In addition, an online adaptive scheme is developed to estimate and update the thresholds, which vary with system operating conditions. The model-based fault detection method needs no additional instrumentation in implementation and can be easily integrated with existing energy management and control systems (EMCS). The fault detection method was tested and validated using in real time data collected from a real office building.

Abstract: This paper presents a method which uses LonWorks control system and frequency converter in Central Air-Condition chilled water variable flow system. In this system, the output of frequency converter can be altered by augmenter PID control rule which is used in control of invariable difference in temperature between water supply and backwater, and the rotating speed of water pump can be changed correspondingly, so when the user load is small ,the electric energy consume can be reduced. The effect of energy-saving was visible comparing with the conventional Air-Condition chilled water constant flow system.

Abstract: Calculation of refrigerant quantities in the heat-exchangers of an air-conditioner on refrigeration and heating operating conditions shows that refrigerant charge quantity in heating operating condition is less than that in refrigeration operating condition. The refrigerant control strategies are most important for refrigeration and heat-pump system. Based on the difference of charged refrigerant quantities of the air-conditioning system between refrigeration and heating operating conditions, the exhaust bypass method was presented in order to improve its operation efficiency. This heat-pump system for controlling refrigerant mass flux was analyzed in detail. The results show that the exhaust bypass method has its advantages in controlling refrigerant mass flux for heat-pump system.

Abstract: We can calculate various pump lifts utilizing the method of solving the pressure balance loop equations in the distributed power system. For the system pumps are set at heat (cold) source and on each branch, if the number of independent loops is less than the pumps, the equations of the pump lift have multiple solutions. When considering the constraint conditions, if we determine the pump lift of the first branch, others can be determined. For the system pumps are set on the main pipes, if we install pumps at heat (cold) source and on each main water supply and backwater pipes, and the pumps of a corresponding pair of main water supply and backwater pipes are the same, when the number of independent loops is equal to the pump lifts, the equations can have solutions. Furthermore, the method can also be applied for other systems where pumps are set on the main pipes, and the equations of the pump lift have a unique solution.

Abstract: This paper has studied the reinforced concrete eccentrically compressed members through the laboratory accelerated corrosion method, which has been also combined with the continuous damage theory to give a preliminary definition of the damage degree of concrete uniform corrosion. The study has shown that with the increase of concrete corrosion layers, the bonding properties of steel and concrete keeps falling. With the increase of damage degree, the concrete will be advanced into the compression and the steel can’t fully exert its tensile properties. The bearing capacity of large and small eccentric hydraulic components will be decreased with the increase of damage degree. With the increase of damage degree, the neutral axis of concrete compressed column will shift to the eccentric point, which can make the eccentricity become small. No matter the unilateral corrosion or the peripheral corrosion, the column deflection is proportional to the damage degree and the column stiffness will be decreased with the increase of corrosion layers.