多台不同冷量冷水机组并联节能运行及控制

针对多台不同制冷量冷水机组并联运行的情况,分析了影响系统能耗的各因素,结合实例对比了不同运行方案的能耗,提出了制定节能运行方案的方法。对冷水机组群控的逻辑判据进行分析,从兼顾节能效果和设备使用寿命的角度,提出了将节能运行方案与负荷变化趋势预测相结合的群控策略。     

冷水机组联合运行策略仿真与分析

在空调系统的能耗中,冷水机组运行产生的能耗占很大的比例。多台冷水机组联合运行时,存在多种运行策略。当根据负荷控制冷水机组的运行时,负荷控制点大小的确定及不同的运行策略会对总能耗造成影响。探讨了冷水机组性能系数和综合部分负荷性能系数分析在冷水机组联合运行策略中的不足,对某建筑空调冷冻水系统冷水机组提出不同运行策略,并采用TRNSYS仿真软件进行仿真,对仿真结果进行了对比分析,得出冷水机组全年优化运行策略,以降低运行能耗。     

多台冷水机组负荷分配优化策略仿真研究

以广州某商场冷水机组系统为研究对象,根据机组全年运行数据,采用最小二乘法对机组能效模型的参数进行辨识,建立了各台冷水机组运行能效模型,并根据空调系统全年冷负荷分布特性,以冷水机组总能耗最小为目标,探讨了基于遗传算法的多台冷水机组负荷优化分配策略。对该商场夏季和过渡季节多台冷水机组优化运行策略进行了仿真实验,结果表明:与原有运行方式相比,夏季负荷率为50%~75%时,冷水机组优化运行后的能耗比原运行方式降低25.75%;过渡季节负荷率为25%~50%时,冷水机组优化运行后的能耗比原运行方式降低5.35%。     

基于全局能耗的空调水系统运行策略的优化分析

针对多台冷水机组联合运行的一次泵定流量系统,建立其主要设备的能耗模型,以及全局能耗最优化目标函数,运用Matlab软件进行"动态规划"求解,从而实现空调水系统运行策略的优化。最后,结合某实际工程,与仅考虑冷水机组能耗的运行策略优化进行比较,验证了基于全局能耗的运行策略优化节能性更好。     

冷水机组配置及运行策略探讨

以某品牌某系列离心式冷水机组的运行测试数据为基础,从配置台数、配置方式及运行策略三方面,分析了影响冷水机组运行能耗的主要因素,对实际工程中冷水机组的运行调节有一定的参考价值。     

基于关联规则算法的冷水机组运行性能优化

提出了一种优化冷水机组运行性能的关联规则数据挖掘方法。以广州某商场不同额定功率的冷水机组为研究对象,利用冷水机组历史运行数据,通过Apriori频繁项集算法分析了各种运行工况下的单台冷水机组最佳运行能效与各运行参数之间的关联规则,以指导冷水机组的节能优化运行。仿真结果表明:利用该运行参数优化方法,2台不同额定功率的冷水机组能耗与原运行方式相比,分别在夏季和冬季降低了5.53%和11.80%,节能效果显著,验证了算法的有效性。其关联规则具有代表性和实用性,能够挖掘冷水机组的节能潜力。该方法适用于已积累大量运行数据的冷水机组,为冷水机组的节能优化运行提供参考。     

多台冷水机组空调系统的优化控制

以两台容量相同并联运行的冷水机组空调系统为例,通过绘制负荷比与比功率关系曲线,确定了最优负荷分配策略。分析结果表明,应用该方法确定多台冷水机组空调系统负荷分配策略可以减少系统能耗。     

基于现场调研和分项计量数据的冷水机组序列控制策略分析

冷水机组的运行能耗约占整个空调系统能耗的30%～40%,冷水机组运行控制策略的优劣对建筑节能管理有很重要的作用。然而实际管理方对机组的运行管理不够重视,操作人员的专业知识不够,并且存在粗放操作的行为,因此冷水机组运行策略优化控制具有很大的节能潜力。为了更好地了解目前冷水机组的运行现状并指导冷水机组的运行,对上海市建筑进行实地调研,并结合分项计量数据,分析目前冷水机组的运行策略,总结出运行人员的运行策略。得到的结论显示目前采用的冷水机组控制策略过于简单,不注重冷水机组的优化控制,实施优化控制策略具有很大的节能潜力。     

磁悬浮变频冷水机组在中央空调系统中的节能分析

简要介绍了磁悬浮冷水机组的工作原理;分析了在不同工况下,不同形式冷水机组的节能效果。通过分析比较,磁悬浮离心式冷水机组具有无油路系统、噪声低、启动电流低、部分负荷时有着较高的综合部分负荷性能系数(IPLV)以及节能环保等特点。通过工程实例对其进行了经济性分析,计算结果表明,磁悬浮变频离心式冷水机组与定频离心式冷水机组相比,全年可降低能耗32%左右,大大降低了中央空调系统的全年运行费用,在建筑节能减排方面有着显著的效果。     

对变频离心式冷水机组全年节电的探讨

介绍了变频离心式冷水机组节能的原理及适用条件。基于冷水机组的全年耗电量是冷水机组在不同运行时段内的机组能效、机组负荷与运行时间乘积之和,分析了1台变频离心式冷水机组在单台和多台机组中应用的节电效果。     

Energy signatures for assessing the energy performance of chillers

This paper investigates how energy signatures can be used as an alternative to an energy use intensity (describing the annual electricity consumption of chillers in kWh per unit floor area of a building in m²) to assess the energy performance of chillers with various design options and operating strategies. An energy signature is a best-fit straight line relating chiller power to a climatic index when chillers operate for a building cooling load profile. Sixteen combinations of four design options and four operating strategies for chillers serving a hypothetical hotel are studied by simulation. For each combination, an energy signature for the chillers is determined. The slope and intercept of the energy signature can be used to accurately predict the annual electricity consumption of the chillers and to evaluate the extent to which this consumption can drop when chiller efficiency is improved. It is desirable to develop reference energy signatures in relation to different characteristics of building cooling load as a yardstick for the minimum requirement of chiller performance. With this yardstick, the effectiveness of energy efficient measures in the operation of chillers could be identified.     

Optimum load sharing strategy for multiple-chiller systems serving air-conditioned buildings

Many central cooling systems in air-conditioned buildings have multiple chillers to meet various cooling load requirements. This paper further develops optimum load sharing strategies for the chillers in order to maximize their aggregate coefficient of performance (COP). Based on the part load performance curves of air-cooled screw chillers, it is ascertained that for two equally sized chillers operating, one should carry a full load and the other should be partially loaded to meet the system load. When two chillers of different sizes are running, the larger chiller should be fully loaded and the smaller chiller should operate at part load in order that their combined capacity satisfies the system load. Such an uneven load sharing strategy for achieving maximum COP is independent of ambient conditions and the control of condensing temperature. The variable primary flow of chilled water should be applied to chillers in order to implement the strategy. The results of this paper are useful in developing low-energy chiller plants.     

基于模型的离心式制冷机组系统优化控制策略研究

本文提出了基于模型的离心式制冷机组系统台数优化控制策略。该优化控制策略充分利用系统日常调试与机组自身提供的可靠数据,采用简化模型来评估单台机的最大制冷量、计算单台机的瞬时制冷量,并预测一定负荷下不同台数机组运行时的系统总电功率,寻求制冷机台数的优化组合,以使得制冷机组系统的性能系数最大化。     

Part load performance of air-cooled centrifugal chillers with variable speed condenser fan control

Air-cooled centrifugal chillers are commonly used in commercial buildings but their performance analysis is lacking. This paper investigates the part load performance of the chillers via a thermodynamic model. The model was validated using a wide range of operating data from an existing chiller with specific settings of outdoor temperature and condensing pressure in controlling the condensing temperature. The validated model was developed specifically to ascertain the maximum coefficient of performance of chiller (COP) together with the strategy for optimizing the condensing temperature under various operating conditions. It is found that the highest COP occurs at a part load ratio (PLR) of 0.71–0.84, depending on the outdoor temperature and the control of condensing temperature, rather than at full load. Yet the chillers operating at such part load conditions will cause extra energy used for the early staging of chilled water pumps. To minimize the overall chiller plant energy consumption, it is still preferable to implement chiller sequencing based on the full load condition than on the aforementioned PLRs. The results of this paper present criteria for implementing low-energy strategies for operating air-cooled chillers satisfying a given building cooling load profile.     

An alternative approach for the performance rating of air-cooled chillers used in air-conditioned buildings

Air-cooled chillers are widely used to provide cooling energy for air-conditioned buildings at the expense of considerable electricity. The (Air-Conditioning & Refrigeration Institute) ARI standard 550/590 sets out a rating condition to specify the coefficient of performance (COP) of the chillers under part-load conditions. This condition was found to be insufficient to deal with diverse operating conditions under the multiple chiller arrangement. This paper proposes an alternative approach to specifying more precisely the chiller COP under part-load conditions. It is desirable to establish a set of part-load performance curves showing how the chiller COP varies with the condensing temperature at various combinations of chiller loads and outdoor temperatures. The results of this paper will give engineers and researchers a better idea about how to specify the upper limit of condensing temperature for more energy efficient chillers and how chiller COP curves help compare air-cooled chillers for buildings in any climate zone and to estimate the annual electricity consumption of chillers satisfying any given building cooling load profile.     

Low-energy design for air-cooled chiller plants in air-conditioned buildings

Chillers are widely used for cooling buildings in the subtropical regions at the expense of considerable energy. This paper discusses how the number and size of air-cooled chillers in a chiller plant should be designed to improve their energy performance. Using an experimentally verified chiller model, four design options were studied for a chiller plant handling the cooling load profile of an office building. Using chillers of different sizes is desirable to increase the number of steps of total cooling capacity. This enables the chillers to operate frequently at or near full load to save chiller power. Pumping energy can also be saved because of the improved control of chilled water flow whereby the chilled water supplied by the staged chillers can match with that required by air side equipment for most of the operating time. It is estimated that the annual electricity consumption of chiller plants could drop by 9.4% with the use of unequally sized chillers. The findings of this research will offer guidance on how to select chillers of different sizes for a low-energy chiller plant.     

Strategy for designing more energy efficient chiller plants serving air-conditioned buildings

In cities located in the subtropical regions, air-cooled chillers are commonly used to cool commercial buildings almost year-round, which accounts for considerable electricity consumption in the long term. This paper explains how a chiller plant should be designed to enable the chillers to operate frequently with maximum performance. Four design options with respect to the number and size of chillers were studied for a chiller plant satisfying the year-round cooling demand of a hotel. For each design option, the annual electricity consumption of chillers and pumps was assessed using a sophisticated chiller model. The assessment showed that an electricity saving of 10.1% can be achieved by installing a chiller plant with six chillers of three different sizes instead of four equally sized chillers. The results of this paper will give engineers and researchers a better idea about how to select chillers of different sizes and how chiller part load performance curves can be used to evaluate improvements in the energy performance of a chiller plant with alternative designs.     

离心式制冷机系统优化控制策略研究

提出了基于模型的离心式制冷机系统台数优化控制策略。该优化控制策略充分利用机组系统的日常调试与制冷机组自身提供的可靠数据,采用简化模型来评估单台机的最大制冷量、计算单台机的瞬时制冷量、并且预测在一定负荷下不同台数机组运行时系统的总电功率,从而寻求制冷机台数的优化组合使得制冷机组系统性能系数最大化。