EFFECT OF SYSTEM LAYOUT ON SUBSURFACE DRAINAGE COST IN FLAT IRRIGATED LAND1

ABSTRACT: The economic feasibility of large-scale subsurface drainage projects in irrigated land is affected by construction costs. This study was conducted to evaluate the effect of two different types of subsurface drainage system layout on construction costs for a 1000 ha pilot area located in the Nile Delta of Egypt. The two types of layout studied were the conventional layout currently used in Egypt and the modified layout that was developed for reducing water losses from rice fields. When compared to the conventional layout, the modified layout resulted in a reduction of 6.74 percent in construction costs (714,464 US$ versus 766,142 US$). This cost reduction is explained by the need for lesser lengths of large diameter collector pipes with the modified layout, which results from the smaller drainage area of subsurface drainage systems (average 23.7 versus 30.8 ha). We have found that the cost of subsurface drainage can be minimized by reducing the area drained by each subsurface drainage system.     

Effect of pipes in heat pump system on electric vehicle energy saving

ABSTRACT

Refrigerant pressure drop and temperature change in pipes are normally ignored in the thermodynamic analysis of traditional vehicle air conditioning system, this will result in serious errors. In this Paper, pressure drop and temperature difference are simulated in different pipes of electric vehicle (EV) heat pump system to analysis the effects of pipes in the actual EV heat pump system. The results indicate that the greater the mass flow, the faster pressure drop increases, the temperature difference decreases. Pressure drop of saturated liquid refrigerant is smaller than that of saturated gas refrigerant at the same saturation pressure and mass flow rate. The higher the refrigerant pressure (no phase change), the slower pressure drop decreases, the faster the temperature difference decreases. Pressure drop decreases with the increment of bending angle of the pipe. For EV heat pump system, suitable valves and less branches are helpful for energy saving of the system. Shortening the pipe between compressor and condenser can reduce temperature change obviously. Pressure drop per unit length in the pipe between evaporator and compressor is large especially in heating mode because of lower refrigerant density. It even reaches to over 100 times of that in the pipe between condenser and throttle valve in heating mode and has negative effects on the performance of the system. If the evaporator is closer to the compressor and the number of branches is less, then pressure drop will decrease a lot, which will be advantageous for energy saving of the heat pump system.     

Numerical parametric study of a new earth-air heat exchanger configuration designed for hot and arid climates

ABSTRACT

Thermal potential for cooling and heating can be achieved by new configuration of earth–air heat exchanger (EAHE). This paper presents a numerical investigation of thermal performance of a spiral-shaped configuration of EAHE intended for the summer cooling in hot and arid regions of Algeria. A commercial finite volume software (ANSYS FLUENT) has been used to carry out the transient three-dimensional simulations and the obtained results have been validated using the experimental and numerical data obtained from the literature. The agreement between our simulation results and those from literature is very satisfactory. A parametric analysis of the new geometry of (EAHE) has been performed to investigate the effect of pitch, depth, pipe length and of the flow velocity on the outlet air temperature and the EAHE’s mean efficiency as well as its coefficient of performance (COP). It has been shown that when the pitch space varies between 0.2 and 2 m the difference of outlet air temperature increases by 6 ^°C. When the air velocity increases from 2 to 5 m/s the mean efficiency decreases from 60 % to 33 % and the COP of the EAHE decreases from 2.84 to 0.46.     

DISCHARGE CHARACTERISTICS OF PERFORATED PIPE FOR USE IN INFILTRATION TRENCHES1

ABSTRACT: Infiltration trenches are an effective stormwater management alternative for the control of urban runoff from small areas. Perforated pipes buried within the gravel of an infiltration trench are used to distribute the inflowing runoff along the length of the trench. Laboratory tests are described that characterize the hydraulics of the orifices in perforated pipes. The results show that the steady-state exfiltration of water from the pipe into a surrounding gravel trench can be described by the orifice equation.     

COST EFFECTIVE OPERATION OF URBAN WATER SUPPLY SYSTEM USING DYNAMIC PROGRAMMING1

ABSTRACT: Efficient operation of a city water supply system is an important goal of all municipalities. Efficient operation should result in minimum operation cost through reduction in total energy use and/ or reduction in on-peak energy consumption. An optimization model was designed for operating the water supply systems of cities using groundwater. The Newton-Raphson pipe network was used for network analysis and a dynamic programming optimization algorithm was used for determining a schedule for pump operation in the pipe network system. The model is most suitable for use in small cities with up to 45,000 in population, but with large-scale disintegration techniques may also be used for larger cities. The savings in operation costs are a function of energy cost and energy use pattern and water use pattern in the area.     

Oxygen supply for oxyfuel CO2 capture

This paper presents the results of a study to develop Air Products’ air separation unit (ASU) offerings for oxyfuel coal CO₂ capture projects. A scalable “reference plant” concept is described to match particular sizes of power generation equipment, taking into account factors such as safety, reliability, operating flexibility, efficiency, and low capital cost. We describe the selection of a process cycle to exploit the low purity requirements, as well as the options for compression machinery and drivers as the scale of the plant increases and the sizes of referenced equipment limit the possibilities. We also explore integration with other elements of the system, such as preheating condensate or heating and expanding pressurised nitrogen. In addition, we consider how the ASU affects the flexibility of the oxyfuel system and discuss how its power consumption can be reduced during periods of high power demand. Finally, the advantages and disadvantages of different execution strategies for air separation unit projects are discussed, as well as alternative commercial models for the supply of oxygen.     

新疆地区地温采暖技术的应用探讨

针对寒冷地区建筑物的采暖方式，介绍一种新型的区域供暖方式－－地温水源热泵（地温中央空调）供暖系统，为寻找新型供暖方式提出了环保安全、绿色节参采暖制冷新理念。     

An Experimental Study of Heat Pipe Performance Using Nanofluids

Heat pipe cooling is widely used in computer processors. Advances in microprocessor technology have resulted in reduced heat transfer surface area. Maintaining an efficient cooling process is therefore challenging. The main goal of this experimental study is to perform a parametric study on heat pipe performance using nanofluids. Nanofluids of 1 and 3 vol% of alumina nanoparticles of 20–50 nm diameters in deionized water versus deionized water as a base fluid were considered in the present study. The nanofluids are prepared in our laboratory using two-step method. The nanofluids thermal properties are measured to confirm the properties enhancement that could indicate a corresponding performance enhancement of the heat pipe. A 10 mm inner diameter, 200 mm long brass tube with 50 mm long evaporator, and 50 mm long water cooled condenser were used. Heat pipe wall temperature is reduced with nanofluids as is the temperature difference between the evaporator and condenser. The thermal diffusivity of the nanofluids is increased by 10%. The pipe pressure in case of deionized water was higher than the corresponding one for the nanofluids by 20–32%.     

交通方式对城市空间形态的影响——以芜湖市为例

城市交通方式和道路系统的布局对城市的规模和空间结构具有重大影响。以芜湖市为例，通过对不同历史时期的比较，提出了城市在水运时期的单侧带状布局、陆路时期的放射布局和综合高速交通时期的都市区三种空间布局形式。此外，借用长度-半径维数模型与关联维数模型对交通方式与城市空间形态之间的关系进行了论证和探讨。     

Dynamic characteristics of cool thermal energy storage systems—a review

Cool thermal energy storage (CTES) plays a significant role in conserving available energy, improving its utilization, and correcting the mismatch that occurs between the supply and demand of energy. It has been employed in many applications, for example, cool storage systems for air-conditioning and natural cooling of energy-efficient building. CTES is widely used in various industrial applications such as food and pharmacy processing, where large short duration loads are often required. This paper presents a review on CTES systems and characteristics. The dynamic characteristics of chilled water storage system, coil pipe cool storage system, packed bed cool storage system, gas hydrate cool storage system, and ice slurry cool storage system are analyzed and discussed. The applications of CTES system are summarized.     

Natural gas engine driven heat pump system – a case study of an office building

ABSTRACT

An eQUEST model was developed to conduct a simulation study of a natural gas engine-driven heat pump (GEHP) for an office building in Woodstock, Ontario, Canada. Prior to the installation of the GEHP, the heating and cooling demands of the office building were provided by rooftop units (RTUs), comprising of natural gas heater and electric air conditioner. Energy consumption for both GEHP and RTUs were monitored for operation in alternating months. These recorded energy consumptions along with weather data were used in the regression analysis. The developed eQUEST models were validated and calibrated with the regression analysis results with respect to the ASHRAE Guideline 14–2014. The eventual models were then applied to investigate the potential annual energy consumption, greenhouse gas (GHG) emission and energy cost savings achieved by using the GEHP in Woodstock, and other cities in Canada, particularly in Ontario.     

Energy-efficient HVAC system through chillers’ capacity sizing for a library building

Heating, ventilating, and air-conditioning (HVAC) systems in commercial buildings consume the largest amount of energy. Recent surge in energy cost necessitates constant re-evaluation of HVAC system for most of the buildings. The objective of this study is to present the strategic approach on energy saving analysis of the HVAC system and chiller sizing optimization for a library building. Energy modeling code (eQUEST) for buildings simulation has been applied to verify and predict the long-term energy consumption of HVAC systems. To improve the accuracy of simulation results, the actual performance curves of the chillers and pumps were the inputs of curve fitting data from on-site field measurements data. Energy consumption data acquisition from the building energy management system (BEMS) for one year has been conducted comprehensively to calibrate energy modeling and to quantify energy saving results. The results revealed good agreement between energy modeling and BEMS data with the error of less than 10%. Besides, energy savings through the chillers’ sizing based on cooling load profile could be achieved satisfactorily by utilizing energy modeling by using the actual chiller performance curve. The energy saving for HVAC system can be obtained satisfactorily at the saving of 110,362 kWh per year. It is expected that the study will stimulate a more robust investigation of energy-efficient and cost-effective HVAC system specific for library buildings.     

Economic evaluation of sewage treatment processes in India

This paper evaluates the total annual cost including capital and operation and maintenance (O&M) costs for the up-flow anaerobic sludge blanket (UASB) and waste stabilization pond (WSP) systems operated in India. It also compares UASB and WSP systems with the activated sludge process (ASP) and biological aerated filter (BAF) systems in terms of total annual cost and chemical oxygen demand (COD) removal cost by assuming various annual interest rates and land prices. It was found that the relationship between capital and O&M costs per unit size of a UASB or WSP system and its treatment capacity can be established by a first-order equation. The relation between the cost of organic removal and capital or O&M cost for various sewage treatment systems at various annual interest rates revealed that, for the Indian context, UASB could be the most suitable option in terms of expenses and treatment efficiency.     

高校人工湿地系统的规划设计——以福建工程学院新校区为例

人工湿地处理技术具有投资低、出水水质好、耗能低、抗冲击力强、操作简单和运行费用低等优点。本文阐述了人工湿地系统应用于高校生活污水回收利用的意义,以福建工程学院新校区的北校区为例,利用前期在福州大学模拟人工湿地系统处理生活污水的实验数据,规划设计人工湿地系统,计算确定相关设施的面积和尺寸,并对人工湿地系统进行平面布置,绘制出系统流程的剖面图。     

Changes in electrical generator cooling systems: Are they cost-effective sources of water now and under climate change?

In the United States, thermal power plant electrical generators (EGs) are large water diverters and consumptive users who need water for cooling. Retrofitting existing cooling systems to dry cooling and building new facilities with dry cooling can save water and reduce EG's vulnerability to drought. However, this can be an expensive source of water. We estimate that the cost of water saved by retrofitting cooling in existing EGs ranges from $0.04/m³ to $18/m³ depending on facility characteristics. Also water savings from building new EGs with dry cooling ranges in cost per unit water from $1.29/m³ to $2.24/m³. We compare costs with that for water development projects identified in the Texas State Water Plan. We find the water cost from converting to dry cooling is lower than many of the water development possibilities. We then estimate the impact of climate change on the cost of water saved, finding climate change can increase EG water use by up to 9.3% and lower the costs of water saved. Generally, it appears that water planners might consider cooling alterations as a cost competitive water development alternative whose cost would be further decreased by climate change.     

HYDROLOGIC IMPACTS OF ALTERNATIVE APPROACHES TO STORM WATER MANAGEMENT AND LAND DEVELOPMENT1

Low impact development (LID) and other land development methods have been presented as alternatives to conventional storm water management and site design. Low impact development encourages land preservation and use of distributed, infiltration‐based storm water management systems to minimize impacts on hydrology. Such systems can include shallow retention areas, akin to natural depression storage. Other approaches to land development may emphasize land preservation only. Herein, an analysis of four development alternatives is presented. The first was Traditional development with conventional pipe/pond storm water management and half‐acre lots. The second alternative was Cluster development, in which implementation of the local cluster development ordnance was assumed, resulting in quarter‐acre lots with a pipe/pond storm water management system and open space preservation. The “Partial” LID option used the same lot layout as the Traditional option, with a storm water management system emphasizing shallow depression storage. The “Full” LID used the Cluster site plan and the depression storage‐based storm water management system. The alternatives were compared to the hydrologic response of existing site conditions. The analysis used two design storms and a continuous rainfall record. The combination of land preservation and infiltration‐based storm water management yielded the hydrologic response closest to existing conditions, although ponds were required to control peak flows for the design storms.     

城乡用地结构与布局优化研究——以黄山市为例

优化城乡用地结构与布局是实施统筹城乡发展、建立和谐社会的重要内容。选取黄山市城乡用地为研究对象,从数量、布局等方面分析了城乡建设用地现状及存在的问题,提出相应的优化城乡建议和对策,为新农村建设和土地利用总体规划的修编提供参考。     

新疆土地资源的开发利用及对环境的影响

新疆土地面积占国土面积1/6，幅员辽阔的地域决定了土地资源自然类型和可利用类型的多样性，近几十年来，新疆土地的开发仍是以农业土地开发为主，其包括开荒扩大耕地面积和广度开发和集约化生产提高单位产量的深度开发，随着西部大开发战略逐渐实施，新疆城市规模不断扩大，工业加速发展，用地需求与日俱增，本文在总结以往的土地开发利用对环境产生的利与弊基础上，为未来土地利用提出了一些趋利避害的建议。     

芜湖市近30年耕地数量变化特征分析

利用1971～2002年的统计资料,通过计算递减率的方法分析了芜湖市近30年来耕地数量变化的时间过程及空间差异.根据1990～2001年的详细统计资料,从国家建设用地、乡村集体建设用地、农民个人建房三个方面阐述了耕地流失的方向,得出耕地流失的主要流向是建设用地占用,揭示了耕地流失的特征,并在此基础上提出了4点对策,从而为研究耕地数量变化的驱动因子,为芜湖市制定科学的耕地资源可持续发展计划提供依据.