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 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.

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。

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%。

常用冷水机组的性能特征和选型案例分析

根据厂家提供的变频螺杆式、定频离心式、变频离心式和磁悬浮离心式冷水机组的全负荷、变冷凝器进水温度性能系数曲线,分析各类冷水机组的节能特性,并提出其适用场所。以长沙市某综合商业体项目为例,设计3种常用的冷源配置方案,分别以变频螺杆式冷水机组和磁悬浮离心式冷水机组调节部分负荷,根据初投资、运行费用、投资回收期、全寿命周期运行成本和碳减排量等对比方案,提出优化建议。

旋风式油分离器仿真优化及试验验证

采用流体仿真技术研究旋风式油分离器内部结构对其压降和油循环率OCR的影响,通过增大排气管管径、增加挡油环和导油管,设计一款新型油分离器,并进行试验验证。结果表明,与现有油分离器相比,在同一状态下,新型油分离器压力损失下降28%,OCR降低24%,该结构有利于改善其应用系统的能效。

离心冷水机组动态仿真与控制开发研究

冷水机组控制系统影响机组的运行性能,利用仿真的方法对其进行设计可以加快设计效率、降低开发周期及成本。文章介绍了基于冷水机组动态仿真的智能控制器设计与仿真测试。首先在Modelica环境下基于热力学定律建立了冷水机组物理模型并进行了模型验证和测试,再将冷水机组仿真模型与控制器模型结合形成动态-控制仿真平台,在此平台上开发并测试了智能加载PID(Proportion、Integral、Differential,结合比例、积分和微分三种环节于一体)、智能整定PID等算法,结果表明,基于仿真平台的控制设计可行,智能PID控制器能很好地降低系统超调量、消除系统震荡,使机组稳定可靠运行。

水冷式冷水机组性能试验装置中变频器常见故障分析

本文介绍了水冷式冷水机组性能试验装置运行原理,阐述了试验装置中变频器的主要应用情形和常见故障形式,从产品选型、安装及维护、参数设定及定期检查等方面提出了降低水冷式冷水机组性能试验装置变频器故障率的具体措施。

换流站阀厅空调冷水机组蒸发器泄漏原因分析与优化改进措施的研究

换流站阀厅的稳定性关系到电网的正常运行,然而,阀厅空调冷水机组的蒸发器经常出现泄漏现象,对阀厅的运行稳定性构成威胁。文章对换流站阀厅空调冷水机组蒸发器泄漏原因进行了分析,发现蒸发器泄漏的主要原因在于制冷系统管道设计不合理及维护保养不到位。针对这些问题,提出了相应的优化改进措施,如优化管道设计,减少机械应力及强化设备维护保养,及时更换或修复磨损部件。实施优化改进措施后,冷水机组的稳定性明显提高,阀厅运行效率也得到了提升。

制冷与热泵产品的能效标准研究和循环热力学完善度的分析

为了建立评价冷水机组和水源热泵的EER或COP等能效指标的公共平台,提出了热力学完善度的分析方法,并计算了我国的房间空调器、冷水机组和水源热泵等制冷装置的热力学完善度的数据范围。大多水冷产品的热力学完善度在0.3至0.5之间,高效产品可以达到0.6,但风冷产品热力学完善度在0.2左右,空气源热泵热水机等介于两者之间。热力学完善度可用于同类产品或相似产品在不同工况下的性能比较。分析可见热力学完善度表征着当前产品设计制造的综合水平,是制定相关产品能效标准的限定值、节能值及能效等级的依据。

间接蒸发冷水机组设计开发及性能分析

基于间接蒸发冷却技术设计了高温冷水机组,其驱动源为室外干空气而非电能,冷水机组的理论出水温度可无限接近进口空气的露点温度。建立了数学模型,并提出了系统的串联冷水流程,以更充分地利用室外干空气的能量。合作开发了第一台间接蒸发冷水机组,通过测试得到了实际机组的性能。最后分析了冷水机组作为湿度独立控制空调系统的高温冷源在中国西部及其他地区的应用。