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.     

风冷冷水机组在工程中的应用及应注意的问题

简要介绍了风冷冷水机组在某工程中的应用，结合设计经验分析了风冷冷水机组噪声，等。     

高温冷水机组能效特性研究的误区剖析

针对相关文献关于常规冷水机组、高温冷水机组在高出水温度工况下的能效特性评价及对比研究方面的认识误区进行了分析.建议采用热力完善度来比较以上两种机组在同一出水温度工况下的能效特性,认为相关文献所研发的高温离心冷水机组能效特性并不优于现有的常规离心冷水机组.     

风冷冷水机组部分负荷时的节能优化运行策略与性能分析

对部分负荷时冷水机组的节能优化运行和能量连续调节方法进行了研究，提出了一种节能优化运行方案，并对机组冷凝器的传热过程进行了模拟计算分析，结果表明机组COP最大可提高35％。     

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.     

Life cycle analysis of enhanced condenser features for air-cooled chillers serving air-conditioned buildings

Air-cooled chillers are commonly used to provide cooling energy for air-conditioned buildings at the expense of considerable electricity. This paper examines the life cycle electricity cost of these chillers with the improved condenser features of condensing temperature control (CTC), evaporative pre-coolers (EC) and variable speed condenser fans (VSF). A validated model for an air-cooled screw chiller was used to ascertain how the individual and mixed features influence the annual electricity consumption of chillers in various operating conditions. It is estimated that the life cycle electricity cost savings range from HK$ 2,099,742 with EC to HK$ 6,399,564 with all the three features, with regard to a chiller plant serving an office building for 15 yr. The life cycle analysis reported here provides important insights into how to reap the benefits of energy efficient technologies for air-cooled chillers.     

Electricity end-use characteristics of air-cooled chillers in hotels in Hong Kong

This paper presents the operating efficiency of air-cooled chillers in three existing hotels and investigates the extent to which the annual electricity consumption can decrease by improving their efficiency. Chillers in these hotels tend to be improperly staged, causing their seasonal efficiency to rise by 0.05–0.12 kW/kW from a full load efficiency of 0.32 kW/kW. When chiller sequencing is restored, their seasonal efficiency could be enhanced to 0.34 kW/kW, which corresponds to an 8.8–22.7% drop in their annual electricity consumption. It is possible to further decrease the annual electricity consumption by 27.0–38.6% when the chillers operate under floating condensing temperature control instead of head pressure control. The implications of improved chiller efficiency for reducing the electricity demand of hotels are discussed.     

冷水机组的优化运行

针对冷水温度、冷却水温度及机组启停控制等影响冷水机组运行的主要因素进行了分析，指出适当提高冷水出口温度和(或)降低冷却水出口温度，采用智能调节策略对多台制冷机和水泵的启动顺序进行合理调配，采用BP网络预测最小预热(冷)期和最长提前停机时间对压缩机进行最优启停控制等，都可以降低系统能耗。     

也谈溴化锂吸收式制冷机的节能问题

由于电与低位热能品位不同，不能不加分析地说溴冷机“节电不节能”；如采用与电联产方式，溴冷机肯定是节能的。     

冷凝式供热锅炉最大热效率

依据热平衡原理，分析了冷凝式供热锅炉的最大热效率，给出冷凝式供热锅炉燃用各种代表性燃料时的最大热效率值。     

水冷式冷水机组能效标准的合理化研究

分析了水冷式冷水机组的能效现状,认为现行能效标准有不合理之处。研究了能效比与制冷量的关系,指出能效标准中两者应为线性函数关系。     

Impact of shading air-cooled condensers on the efficiency of air-conditioning systems

Shading is a technique used to reduce the cooling demand in buildings and save energy. This paper investigates the possibility of reducing the electrical demand and saving energy by shading the condensers of air-conditioning (A/C) equipment. A limiting analysis compares the performance of several A/C systems with ideal shade to those with ideal solar heat gain. The comparison is based on a theoretical model and data from equipment catalogs. The results show that the theoretical increase in the coefficient of performance (COP) due to shading is within 2.5%. Furthermore, this small improvement in ideal efficiency decreases at higher ambient temperatures, when enhancements to efficiency are more needed. A sensitivity analysis shows that the small COP enhancement is not significantly affected by assumed variables. The actual efficiency improvement due to shading is not expected to exceed 1%, and the daily energy savings will be lower. The findings indicate that condenser shading alone, without evapo-transpiration, is not an effective measure to improve efficiency or save energy.     

对并联螺杆式冷凝机组油温过高故障的处理

在对济南某食品公司进行制冷工安全培训时,笔者参与分析解决了一例螺杆机组油温过高的故障。由于此故障比较隐蔽,而且主要涉及安装施工的问题,因此特地把对此故障的分析解决过程介绍如下,供大家参考借鉴。     

建筑供暖的室温调节与节能

认为应根据建筑的使用情况进行室温调节,既可以减少能耗,又利于节能,提出了室温调节的方法和措施。     

一次泵系统冷水机组变流量控制方案

介绍了一次泵空调水系统在冷水机组采用变水量运行过程中可能出现的问题。根据对负荷侧(表冷器)冷量和流量特性的分析，给出不同冷水机组台数组合时的控制方案和其他环节的控制策略。     

风冷热泵机组环境温度使用范围及除霜技术

本文讨论了风冷热泵机组在规定环境温度下以及更低环境温度条件下制热能力的相对变化和膨胀阀的对应变化，提出在低温环境下风冷热泵机组系统设计方案，并结合际详细介绍了风冷热泵机组除霜技术与经验数据。     

蒸发式冷凝空调系统运行中能效的实验研究

将蒸发式冷凝器应用于建筑制冷空调系统作为新型的冷却散热设备,建立实验平台对运行参数进行优化和对系统能效进行实验研究。实验结果表明:该系统最佳的运行参数组合是风速3.1m·s-1和水喷淋密度0.052kg·m-1·s-1;随着负荷率的逐渐降低,冷凝温度在38.9～34.9℃之间,制冷机COP在5.02～2.54之间,冷凝侧EER在4.48～2.23之间。蒸发式冷凝空调系统运行稳定、高效节能,适用于建筑制冷空调。     

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.     

Advanced dehumidifiers for moisture control

As thermal insulation improves so ventilation losses assume crucial importance for energy economy. In temperate climates this factor is closely related to moisture and temperatures in the home. Since ventilation control is never easy, moisture generation can be controlled by heat pumps, which are already used for this purpose in Italy, Japan and the USA. But their potential could be greatly increased if they incorporate counterflow air/air heat exchangers, as described here.     

利用蒸发冷却技术制取高温冷水设备的应用气候分区

推导了蒸发冷却式冷水机组出水温度的计算式,提出了蒸发冷却式冷水机组和蒸发冷却与机械制冷复合高温冷水机组综合部分负荷性能系数的计算方法,对这两种机组的应用进行了气候分区.