Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Feasibility Analysis of Back-Pressure Steam Feeding Water Pump for Direct Air-Cooled Unit

As the performance of an air-cooled condenser is apt to be affected by the fluctuating ambient condition, some difficulties are brought to the use of a steam feeding water pump in an air-cooled unit. This paper introduces a new design of for steam feeding the water pump of an air-cooled unit using the back-pressure steam turbine as the prime motor. Using variable condition analysis on a 600 MW direct air-cooled unit, and with consideration of the effect on the ambient conditions, the feasibility, economy, and adaptability of the design are verified.

Water, Air Emissions, and Cost Impacts of Air-Cooled Microturbines for Combined Cooling, Heating, and Power Systems： A Case Study in the Atlanta Region

The increasing pace of urbanization means that cities and global organizations are looking for ways to increase energy efficiency and reduce emissions. Combined cooling, heating, and power （CCHP） systems have the potential to improve the energy generation efficiency of a city or urban region by providing energy for heating, cooling, and electricity simultaneously. The purpose of this study is to estimate the water consumption for energy generation use, carbon dioxide （CO2） and NOx emissions, and economic impact of implementing CCHP systems for five generic building types within the Atlanta metropolitan region, under various operational scenarios following the building thermal （heating and cooling） demands. Operating the CCHP system to follow the hourly thermal demand reduces CO2 emissions for most building types both with and without net metering. The system can be economically beneficial for all building types depending on the price of natural gas, the implementation of net metering, and the cost structure assumed for the CCHP system. The greatest reduction in water consumption for energy production and NOx emissions occurs when there is net metering and when the system is operated to meet the maximum yearly thermal demand, although this scenario also results in an increase in greenhouse gas emissions and, in some cases, cost. CCHP systems are more economical for medium office, large office, and multifamilv residential buildings.

Performance analysis on a novel water chiller using liquid desiccant

A new type of liquid desiccant water chiller for applications on air-conditioning and refrigeration is introduced.The system can be driven by low-grade heat sources with temperatures of 60 to 80 ℃,which can be easily obtained by a flat plat solar collector,waste heat,etc.A numerical model is developed to study the system performance.The effects of different parameters on performance are discussed,including evaporating temperature,regenerating temperature,ambient condition,and mass flow rates of closed moist air and regenerating air.The results show that an acceptable performance of a cooling capacity of 2.5 kW and a coefficient of performance of 0.37 can be achieved in a reference case.The regenerating temperature and the humidity ratios of ambient air are two main factors affecting system performance,while the temperature of ambient air functions less.In addition,the mass flow rate of regenerating air and closed moist air should be carefully determined for economical operation.

Energy, Exergy and Thermoeconomics Analysis of Water Chiller Cooler for Gas Turbines Intake Air Cooling

Gas turbine (GT) power plants operating in arid climates suffer a decrease in output power during the hot summer months because of the high specific volume of air drawn by the compressor. Cooling the air intake to the compressor has been widely used to mitigate this shortcoming. Energy and exergy analysis of a GT Brayton cycle coupled to a refrigeration air cooling unit shows a promise for increasing the output power with a little decrease in thermal efficiency. A thermo-economics algorithm is developed to estimate the economic feasibility of the cooling system. The analysis is applied to an open cycle, HITACHI-FS7001B GT plant at the industrial city of Yanbu (Latitude 24o 05” N and longitude 38o E) by the Red Sea in the Kingdom of Saudi Arabia. Result show that the enhancement in output power depends on the degree of chilling the air intake to the compressor (a 12 - 22 K decrease is achieved). For this case study, maximum power gain ratio (PGR) is 15.46% (average of 12.25%), at an insignificant decrease in thermal efficiency. The second law analysis show that the exergetic power gain ratio drops to an average 8.5%. The cost of adding the air cooling system is also investigated and a cost function is derived that incorporates time-dependent meteorological data, operation characteristics of the GT and the air intake cooling system and other relevant parameters such as interest rate, lifetime, and operation and maintenance costs. The profit of adding the air cooling system is calculated for different electricity tariff.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

Thermodynamic and Experimental Analysis of an Ammonia-Water Absorption Chiller

A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested. The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heating source. The thermodynamic models have been derived using the First and Second Laws. Calculated results are compared with experimental data. The results show that the cooling capacity of experimental apparatus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and 0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.

Optimum control strategy for all-variable speed chiller plant

The optimum control strategy and the saving potential of all variable chiller plant under the conditions of changing building cooling load and cooling water supply temperature were investigated. Based on a simulation model of water source chiller plant established in dynamic transient simulation program (TRNSYS),the four-variable quadratic orthogonal regression experiments were carried out by taking cooling load,cooling water supply temperature,cooling water flow rate and chilled water flow rate as variables,and the fitting formulas expressing the relationships between the total energy consumption of chiller plant with the four selected parameters was obtained. With the SAS statistical software and MATHEMATICA mathematical software,the optimal chilled water flow rate and cooling water flow rate which result in the minimum total energy consumption were determined under continuously varying cooling load and cooling water supply temperature. With regard to a chiller plant serving an office building in Shanghai,the total energy consumptions under different control strategies were computed in terms of the forecasting function of cooling load and water source temperature. The results show that applying the optimal control strategy to the chiller plant can bring a saving of 23.27% in power compared with the corresponding conventional variable speed plant,indicating that the optimal control strategy can improve the energy efficiency of chiller plant.

Evaluation of Performance of Thermal and Electrical Hybrid Adsorption Chiller Cycles with Mechanical Booster Pumps

Large amounts of waste heat below 100oC from the industrial sector are re-leased into the atmosphere. It has been suggested that energy system efficiency can be increased with adsorption chillers. However, the cooling power and coefficient of performance (COP) of conventional adsorption chillers significantly decrease with the desorption temperature. In this paper, we proposed a mechanical booster pump (MBP)-assisted adsorption chiller cycle, and evaluated its performances. In the cycle, a MBP was incorporated into a zeolite-water-type adsorption chiller for facilitating water vapor transportation between an adsorber and an evaporator/condenser. We have experimentally studied the effect of the input electrical power of MBP on the performances of adsorption chiller cycle. It has been demonstrated that the heat input achieved by using MBP at the desorption temperature of 50oC was 1.6 times higher than that of without MBP at the desorption temperature of 60oC. And the increase of pump power was found to be effective in increasing the heat input. Therefore, it was confirmed that the operation range of desorption temperature, which can be generated by using the waste heat, was extended and the cooling power was increased directly by using MBP.

Analysis of Nuclear Power Development in Henan Province Based on Carrying Capacity of Water Resources

Firstly, current situation of water resources in Henan Province was analyzed, and then carrying capacity of water resources in Henan Province was assessed based on ＂degree of water stress＂ and ＂balance index of carrying capacity of regional water resources＂, finally the thinking on adopting air-cooling technology to develop nuclear power in Henan Province was expounded.

Measurement of thickness and heat transfer coefficient of water film out of tube in an evaporative air cooler

Thickness of falling water film out of tubes is one of critical factors of heat transfer of evaporative air cooler. A new method of resistance measurement was developed to measure thickness of the film. When the resistance probe on the tip of micrometer touches the surface and bottom of the film, two corresponding sudden reductions of resistance occurs, and the difference of two graduations on the micrometer displays the thickness of the film. The film thickness of eleven angles was measured in five kinds of water flows and results varies from 0.8933mm to 1.7233 mm. Mean thickness and mean heat transfer coefficient of the film out of the tube was calculated.

太阳能吸收式制冷系统及其蓄能技术研究

在分析国内外现有太阳能吸收式制冷系统的基础上,从太阳能集热器、蓄能形式、辅助热源、吸收式冷水机组以及太阳能集热器与吸收式冷水机组的匹配等方面详细阐述太阳能吸收式制冷系统及其蓄能技术的发展现状,并对太阳能制冷空调系统的控制策略、优化分析及理论研究进行总结,最后指出太阳能吸收式制冷系统及其蓄能技术的发展方向。

夏热冬冷地区空调冷热源配置的多目标优化

为实现“双碳”背景下清零建筑直接碳排放的目标,夏热冬冷地区建筑空调冷热源越来越多地采用空气源热泵加水冷式冷水机组的复合架构。其中,空气源热泵冬季供热,夏季与水冷式机组共同供冷。由于空气源热泵供冷能效较低,提高水冷式机组容量配置,尽可能使之分担更多的冷负荷,有利于降低系统供冷能耗,但系统投资也将随之上升。因此,有必要研究复合架构下空调冷热源配置的综合优化方法。利用层次分析法,计算空调冷热源系统的节能性、环保性、经济性、节材性等不同目标维度的权重,建立空调冷热源的综合优化目标函数。设计空调冷热源配置的优化流程,并以上海某办公建筑为例进行分析。结果表明,随着水冷机组容量的增加,空调冷热源系统的全年能耗降低,耗材生产能耗、折算年费上升,而碳排放呈先降后升的规律。多目标优化方法可以更好地实现各项指标之间的平衡,为相关研究及实际项目决策提供参考。

GB 19577—2024《热泵和冷水机组能效限定值及能效等级》解析

热泵和冷水机组作为获取冷、热水的装置,节能环保,得到了广泛的普及和应用。GB 19577—2015《冷水机组能效限定值及能效等级》已经执行了9年时间,随着制造工艺、新材料、新科技的应用,整体的能效水平得到了提高,为此国家市场监督管理总局、国家标准化管理委员会于2024年4月29日发布了标准GB 19577—2024《热泵和冷水机组能效限定值及能效等级》,并将于2025年2月1日正式实施,该标准代替了GB 19577—2015、GB 29540—2013、GB 30721—2014、GB 37480—2019。本文通过分析GB 19577—2024与GB 19577—2015等标准的差异,为从事热泵和冷水机组生产制造企业及检测机构和市场监管部门理解并执行标准提供了基础。

磁悬浮冷水机组冷冻出水温度DMC控制仿真研究

针对磁悬浮冷水机组冷冻水出水温度控制存在时滞、外界干扰而传统PID控制效果不佳的问题,基于动态矩阵控制算法建立控制与仿真模型,通过预测冷水机组出水温度并加以校正,局部动态优化得到控制器最优控制量。仿真结果表明,动态矩阵控制算法能够实现平稳、无超调的控制,出水温度调整速度相比传统PID控制提升3倍以上,抗干扰能力也优于传统PID算法。

SPC and Kalman filter-based fault detection and diagnosis for an air-cooled chiller

Buildings worldwide account for nearly 40%of global energy consumption.The biggest energy consumer in buildings is the heating,ventilation and air conditioning(HVAC)systems.In HVAC systems,chillers account for a major portion of the energy consumption.Maintaining chillers in good conditions through early fault detection and diagnosis is thus a critical issue.In this paper,the fault detection and diagnosis for an air-cooled chiller with air coming from outside in variable flow rates is studied.The problem is difficult since the air-cooled chiller is operating under major uncertainties including the cooling load,and the air temperature and flow rate.A potential method to overcome the difficulty caused by the uncertainties is to perform fault detection and diagnosis based on a gray-box model with parameters regarded as constants.The method is developed and verified by us in another paper for a water-cooled chiller with the uncertainty of cooling load.The verification used a Kalman filter to predict parameters of a gray-box model and statistical process control(SPC)for measuring and analyzing their variations for fault detection and diagnosis.The gray-box model in the method,however,requires that the air temperature and flow rate be nearly constant.By introducing two new parameters and deleting data points with low air flow rate,the requirement can be satisfied and the method can then be applicable for an air-cooled chiller.The simulation results show that the method with the revised model and some data points dropped improved the fault detection and diagnosis(FDD)performance greatly.It can detect both sudden and gradual air-cooled chiller capacity degradation and sensor faults as well as their recoveries.

蒸发冷却式冷水机组热岛效应研究

蒸发冷却式冷水机组应用于实际工程时,排风气流易倒流至进风口,从而产生热岛效应,影响机组性能。在相同进风风量、进风入口温湿度的条件下,数值模拟研究蒸发冷却式冷水机组在不同排风百叶角度下的压力分布、温度分布和速度分布等流动特性,得到排风气流组织和空间流场分布较佳状态下的排风百叶角度,并进行工程现场测试验证。结果表明:排风百叶角度不低于30°时,理论上可避免热岛效应发生;工程应用推荐排风百叶角度为45°,应对突发状况时冗余系数更高。

大型商业建筑冷水机组运行调研及装机容量分析

通过对南北方不同区域的7个建筑案例中,冷水机组的装机容量和使用数据进行调研分析可知:北京地区,商业建筑实际运行的冷负荷指标约为90~130W/m^(2),对于南方的夏热冬暖地区,商业建筑实际运行的冷负荷指标为130~170W/m^(2)。究其原因,除室外干球温度南方稍高于北京外,湿球温度较高,室外空气焓值较高,潜热负荷大,因此,总负荷较大。

基于仿真对比的某办公建筑空调系统改造分析

对某办公建筑的老旧空调系统进行改造,比较了冷水机组与多联机2种改造方案,探讨了人员加班情况对系统选择的影响。首先,对建筑改造区域进行了负荷模拟,针对每种方案进行设备选型。然后,对2种方案供冷、供暖季的空调系统能耗进行了仿真和比对,多联机系统能耗更低,投资回收期仅4.6 a。最后,针对不同的加班模式和加班率进行了仿真分析,绘制了能耗-加班率曲线,发现多联机系统更适用于有人员加班情况出现的建筑。当独立办公室加班率为10%时,改造区域多联机系统的供冷季能耗比冷水机组系统低41.7%。