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.

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。

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。

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。

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。

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.

地下车站冷水机组部分负荷性能系数研究

部分负荷性能系数的概念综合考虑了气象因素、实际负荷及运行条件,便于在更贴近实际使用条件下对机组进行比较、评价,有助于促进机组实际运行性能水平的提高,目前已被空调行业广泛采用。国标定义的部分负荷性能系数具有广谱性,力求覆盖全国各气候区及各种建筑类型。地铁车站应用场景下,空调负荷有其固有的特点,不宜直接采用国标定义的部分负荷性能系数定义工况点及计算方法。本文选取我国不同气候区域的代表城市,在深入研究地下车站空调负荷特点的基础上,提出适应于地下车站应用场景的部分负荷性能系数定义工况点及相应的计算方法。

疫苗生产厂房冷水机组可移动式胶球清洗装置的应用

随着生物医药及大健康产业项目的飞速发展,生物厂房的建设和使用需求不断增加,冷水机组作为最基础的保障设施,使用数量和技术也随之提高,在冷水机组冷凝器胶球清洗的实践过程中,不仅需要解决设备成本、混合布管、胶球使用寿命等技术问题,也要根据实际情况选择高效运行装置的方法。通过剖析各类胶球清洗装置效果,以提升冷凝器清洗效率为目标,重点研究胶球清洗装置与疫苗生产厂房冷水机组的适配性,提出以移动式胶球清洗冷水机组冷凝器的解决方案。基于此,对移动式胶球清洗装置在冷水机组中的具体应用进论述和分析,为冷水机组冷凝器清洗提供新的技术和方法。

超高效两级压缩水冷螺杆式冷水机组开发

针对两级压缩技术在中小容量冷水机组中鲜少应用的现状,本文设计了一种名义制冷量为615.48 kW的两级压缩水冷螺杆式冷水机组,采用新型转子型线和结构设计研制了两级变频螺杆制冷压缩机,并依据国家标准对开发的压缩机和冷水机组进行实验测试。结果表明:本文研发的两级变频螺杆制冷压缩机容积效率普遍高于96%,等熵效率最高达84.4%;冷水机组在出水温度为7℃的名义工况下COP达7.01,相比标准GB 19577—2015规定的一级能效水平高16.83%,部分负荷综合性能系数IPLV达到10.45,相比标准GB 19577—2015规定的一级能效水平高39.33%。两级压缩技术能够有效提升水冷螺杆式冷水机组的性能,与无中间冷却相比,中间冷却后冷水机组制冷量和COP分别提升11%和8%以上。

间接蒸发冷却冷水机组在我国数据中心的应用分析

以既有数据中心为模型,选取20个位于不同地区的典型城市作为样本,比较了不同地区应用间接蒸发冷却冷水系统和水冷冷水机组空调系统的运行状况。通过计算2种冷源系统的PUE及空调系统全年耗电量,分析了间接蒸发冷却冷水系统在不同地区的节能规律及其相较于传统水冷冷水机组空调系统的节能潜力和经济优势,给出了间接蒸发冷却冷水机组适合在我国推广的地区,为不同地区数据中心冷源系统的选择提供参考。

蒸发冷凝式冷水机组在华南医院的应用及管理

蒸发冷凝式冷水机组在华南地区医院建筑应用经验较少,在冷源系统设计、运行维护、水质管理、能耗水平等方面缺少研究和分析。以广州市某医院为例,蒸发冷凝式冷水机组在医院的应用一般采用模块化布置,利于节能和备用。在运维方面,需要人员24 h值班,重点开展蒸发冷凝器清洗除垢保养工作,并通过共同使用系统控制法、化学法和软化法来减缓结垢速度。夏天工况下,蒸发冷凝式冷水机组的能效比(COP)一般介于3.58~4.34之间,能效水平低于水冷式冷水机组。

基于最佳负荷率的冷水机组序列控制优化

提出了基于最佳负荷率的冷水机组序列控制优化策略,可以优化冷水机组的运行组合和启停序列,在满足建筑冷量需求的前提下,使冷水机组的运行效率最高,降低冷水机组能耗。根据该优化策略开发了冷水机组序列控制优化软件,并将其运用到中国香港某建筑群的建筑管理系统(BMS)中,采用实时数据分析方式对比实行优化策略前后冷水机组的组合方案、平均负荷率与平均COP,采用历史数据分析方式计算冷水机组的年节能率,验证冷水机组序列控制优化策略的应用效果与节能潜力。结果表明:在满足建筑冷量需求的前提下,优化组合中冷水机组的开启台数更少或型号更小,且平均负荷率和平均COP都明显高于未优化组合;2009年和2010年的年节能率分别为9.15%和11.82%,节能效果明显。

气悬浮冷水机组热力循环特性研究

冷水机组广泛应用于大型建筑、工业制冷等领域,采用气体轴承的离心冷水机组因其高效、可靠、紧凑等优势,成为重要研究方向。系统中的轴承供气、高速电机冷却过程使系统循环更为复杂,分析系统热力循环及变工况运行特性是系统设计及优化的前提。考虑了轴承供气及电机冷却过程,建立了带经济器的气悬浮冷水机组的数学模型,分析了系统热力学参数变化规律,结果表明:蒸发温度升高时,系统COP增大而[火用]效率减小,系统COP和[火用]效率随着冷凝温度的升高而降低。随着冷却电机负荷的增大,系统COP和[火用]效率均减小。系统的总[火用]损主要来源为冷凝器和蒸发器,两者占为61.9%。