武汉嘉叶宾馆空调冷热源的选择

针对武汉嘉叶宾馆空调扩建工程，文章对螺杆式冷水机组加燃油锅炉，螺杆式冷水机组加蓄热式电热锅炉，直燃型溴化锂吸收式冷温水机组3种类型的冷热源方案进行了技术、经济性分析，作者认为，螺杆式冷水机组加燃油锅炉方案最合适。     

武汉市某酒店节能型空调冷热源方案的选择

根据现有能源结构,结合武汉某宾馆空调冷热源方案的选择,对螺杆式冷水机组加燃气锅炉、螺杆式冷水机组加蓄热式电热锅炉、水源热泵机组3种类型的冷热源方案进行了技术、经济性比较和分析。结果显示:螺杆式冷水机组加燃气锅炉方案初投资最低、运行费用较少,是该酒店最合适的节能型冷热源。     

螺杆式冷水机组群控策略

叙述了螺杆式冷水机组在冷冻/冷却水系统定流量情况下,低负荷或高负荷时,能效比均较低的特点,提出了一种在保证机组稳定、可靠运行的基础上,以系统总能效比为目标的螺杆式冷水机组群优化控制策略。     

水冷式制冷机组的性能比较及选型

分析了水冷活塞式、螺杆式和离心式冷水机组的特点，介绍了不同厂家制造的一些代表性的水冷活塞式、螺杆式和离心式冷水机组在名义工况下的性能，总结了他们各自的适用范围和COP值大小，可供实际使用和选型参考。     

某宾馆空调冷源方案的比较

介绍了浙江省绍兴市某宾馆改造过程中,对三种空调冷源方案从初始投资和运行费用两方面进行了比较：一是风冷热泵冷水机组（单冷）;二是螺杆式冷水机组;三是溴化锂冷水机组。结果第一种方案最符合要求。     

半封闭活塞式和螺杆式冷水机组性能比较

半封闭活塞式和螺杆式冷机组以其各自鲜明的特点得到了广泛的应用。文章分析了开利半封闭活塞式和螺杆式冷水机组的特点,对比在不同温度和不同冷量下的性能,为实际使用打下基础。     

冷水机组运行特性建模与优化控制研究

为实现中央空调冷水机组运行优化,提出了基于支持向量回归机(SVR)建模的冷水机组优化控制方案。利用SVR建模思想,在冷水机组运行特性分析基础上,采用基于遗传算法的SVR参数优化算法,对冷水机组运行特性进行建模,并以此模型为基础提出了冷水机组运行参数寻优算法,通过动态调整机组运行参数实现节能。利用Matlab的Libsvm软件包对某螺杆式冷水机组运行特性进行建模,并在典型工况下,对优化控制方法和常规运行方法的能耗做了仿真对比。结果表明,采用基于SVR建模的冷水机组优化控制方法能显著提高冷水机组运行效率,具有很好的工程适应性和应用前景。     

雄安某社区中心空调冷源方案比选

结合项目当地能源价格,从投资费用、运行费用、维护费用等方面对雄安地区某社区中心的蓄冷空调、水冷螺杆式冷水机组、螺杆式风冷热泵、模块式风冷热泵、双热源多联机的空调冷源方案进行了对比,并结合项目用能特点,选择了双热源多联机冷源方案。     

某住宅区冷热源型式的分析与比较

本文针对某住宅区设置集中式空调系统的要求,对风冷热泵冷热水机组、水冷螺杆式冷水机组＋燃油锅炉、由热电厂余热蒸汽驱动的蒸汽双效溴化锂吸收式冷水机组＋热交换器和燃气直燃型溴化锂吸收式冷温水机组等四种冷热源方案作了能耗和经济性比较,认为利用热电厂余热蒸汽为能耗的方案是最适合该住宅楼的空调方案。     

电动螺杆式与溴化锂吸收式中央空调经济性实例比较

通过某侯机楼改造工程中央空调的选型（设计制冷量２９００ＫＷ），分析了比较了两种机型选择方案，即电动螺杆式冷水机组和溴化锂吸收式蒸汽机组。并得出结论：后者比前者经济。     

Steady-state simulation of screw liquid chillers

In order to predict the performance of screw liquid chillers in a wide range of configuration parameters and operating conditions, a steady-state simulation model is presented, which is suitable for non-economized and economized chillers. The model includes sub-models for key components, such as non-economized compressor, economized compressor, shell-and-tube condenser, expansion valve, and flooded evaporator. Sequential modular method and successive substitution methods are combined together to carry out the simulation of the chillers. The convergence properties of this simulation technique are also analyzed. The present model can predict the performance within ±10% for large scale of cooling capacity including four specifications of non-economized chillers and three specifications of economized chillers. With the validated model, a sensitivity analysis on the economizer system is made. It is found that the cooling capacity of screw liquid chiller can be increased apparently by adding the economizer, but only when the volumetric ratio of the first stage internal compression is greater than a certain value, the economized screw liquid chiller can gain a higher COP than that of the non-economized one at the same time.     

Improved energy performance of air cooled centrifugal chillers with variable chilled water flow

This paper considers how to apply optimum condensing temperature control and variable chilled water flow to increase the coefficient of performance (COP) of air cooled centrifugal chillers. A thermodynamic model for the chillers was developed and validated using a wide range of operating data and specifications. The model considers real process phenomena, including capacity control by the inlet guide vanes of the compressor and an algorithm to determine the number and speed of condenser fans staged based on a set point of condensing temperature. Based on the validated model, it was found that optimizing the control of condensing temperature and varying the evaporator’s chilled water flow rate enable the COP to increase by 0.8–191.7%, depending on the load and ambient conditions. A cooling load profile of an office building in a subtropical climate was considered to assess the potential electricity savings resulting from the increased chiller COP and optimum staging of chillers and pumps. There is 16.3–21.0% reduction in the annual electricity consumption of the building’s chiller plant. The results of this paper provide useful information on how to implement a low energy chiller plant.     

Optimum hot water temperature for absorption solar cooling

The hot water temperature that maximizes the overall instantaneous efficiency of a solar cooling facility is determined. A modified characteristic equation model is used and applied to single-effect lithium bromide-water absorption chillers. This model is based on the characteristic temperature difference and serves to empirically calculate the performance of real chillers. This paper provides an explicit equation for the optimum temperature of vapor generation, in terms of only the external temperatures of the chiller. The additional data required are the four performance parameters of the chiller and essentially a modified stagnation temperature from the detailed model of the thermal collector operation. This paper presents and discusses the results for small capacity machines for air conditioning of homes and small buildings. The discussion highlights the influence of the relevant parameters.     

Modelling of improved energy performance of air-cooled chillers with mist pre-cooling

Air-cooled chillers are widely used to provide cooling energy and yet pragmatic and simple energy efficient measures for them are still lacking. This paper considers how their coefficient of performance (COP) can be improved by using mist to pre-cool ambient air entering the condensers. The benefit of this application rests on the decrease of compressor power resulting from the reduced condenser air temperature with insignificant consumption of water and pump power associated with the mist generation. Based on a simulation analysis of an air-cooled screw chiller operating under head pressure control, applying such mist pre-cooling enables the COP to increase by up to 7.7%. Precise control of mist generation rate and integration with floating condensing temperature control are the major challenges of using a mist system to maximize electricity savings. The results of this study will prompt low-energy operation of existing air-cooled chillers working for various climatic conditions.     

Performance analysis of combined microgas turbines and gas fired water/LiBr absorption chillers with post-combustion

The integration of microgas turbines (MGT) and absorption chillers is an emerging technology that uses a wide range of fuels to produce electricity, cooling and heating simultaneously for small scale distributed generation in grid connected or isolated locations.This paper studies the performance of MGTs of different power capacities directly coupled to double-effect water–LiBr absorption chillers. In these systems the MGT exhaust gas is the heating medium to drive the chiller. Also post-combustion natural gas is used to increase the cooling capacity of the system. The paper analyses the effect of the post-combustion degree on the integrated system performance of four MGT power sizes. Two cases are considered. In the first, fresh air is added together with the post-combustion natural gas and in the second it is not added. In the latter case the oxygen necessary for the combustion reaction is extracted from the MGT exhaust gas stream. For the sake of comparison a study is also made of the performance of a more conventional system consisting of an MGT and a hot water heat exchanger to drive an absorption chiller. The main advantages of the new technology over this conventional system are that the COP of the chillers is higher because they are driven by higher temperatures, the production of electricity and chilled water is decoupled and there is a wider range of chilled water production capacity.     

Thermodynamic-behaviour model for air-cooled screw chillers with a variable set-point condensing temperature

This paper presents a thermodynamic model to evaluate the coefficient of performance (COP) of an air-cooled screw chiller under various operating conditions. The model accounts for the real process phenomena, including the capacity control of screw compressors and variations in the heat-transfer coefficients of an evaporator and a condenser at part load. It also contains an algorithm to determine how the condenser fans are staged in response to a set-point condensing temperature. The model parameters are identified, based on the performance data of chiller specifications. The chiller model is validated using a wide range of operating data of an air-cooled screw chiller. The difference between the measured and modelled COPs is within ±10% for 86% of the data points. The chiller’s COP can increase by up to 115% when the set-point condensing temperature is adjusted, based on any given outdoor temperature. Having identified the variation in the chiller’s COP, a suitable strategy is proposed for air-cooled screw chillers to operate at maximum efficiency as much as possible when they have to satisfy a building’s cooling-load.     

Modelling of vapour-compression liquid chillers with neural networks

A new approach to steady state modelling of vapour-compression liquid chillers is presented in this paper. The model uses a generalised radial basis function (GRBF) neural network to predict chiller performance. The GRBF chiller model is developed with the objective of requiring only those input parameters that are readily known to the operating engineer, i.e. the chilled water outlet temperature from the evaporator, the cooling water inlet temperature to the condenser, and the evaporator capacity. The GRBF chiller model predicts relevant performance parameters of a chiller, especially the coefficient of performance. The neural network is applied to two different chillers operating at the University of Auckland, New Zealand and the agreement is found to be within ±5%. It is inferred that neural networks, in particular the generalised radial basis function, can be a promising tool for predicting the chiller’s performance for fault detection and other diagnosis purposes.     

Performance modelling of air-cooled twin-circuit screw chiller

A large variety of chiller models are available in the public domain but none can model chillers that comprise multiple and separate refrigerant circuits, despite that chillers of this type are already widely used for their good part-load performance. Presented in the paper is a mathematical model for an air-cooled twin-circuit chiller, with two screw compressors per circuit. The chiller model comprises a series of linked mathematical modules, each made up of a set of thermodynamic and empirical equations for modelling the major chiller components. The coefficients in the component models were evaluated using rated operating conditions obtained from the manufacturer and measured performance data of an existing chiller. The chiller model had been applied to simulate the performance of another set of chiller of the same make and model. Comparison of the predicted and measured performance of the chiller showed that the model could yield accurate energy use predictions over a wide range of operating conditions. The model could also provide good predictions of the variation in chiller performance due to staged operation of the separate refrigerant circuits in the chiller and of compressors in each circuit, which matched with observations made with measured chiller operation data.     

Integration of absorption cooling systems into micro gas turbine trigeneration systems using biogas: Case study of a sewage treatment plant

Absorption chillers can help to increase the performance of biogas-driven micro gas turbine (MGT) cogeneration plants. In this paper we analyse various integrated configurations of several types of commercially available absorption cooling chillers and MGT cogeneration systems driven by biogas. MGTs are fuelled with biogas and their waste heat is used to drive absorption chillers and other thermal energy users. The chillers considered in this study include single- and double-effect water/LiBr and ammonia/water chillers. The exhaust gas from the MGT can be used directly to drive the chiller or indirectly to produce hot water to drive the chiller. In this paper we conduct a case study for an existing sewage treatment plant. Chilled water is used to reduce humidity in the biogas pre-treatment process and cool the combustion air of the MGT. We identify the most interesting integrated configurations for trigeneration systems that use biogas and micro gas turbines. We analyse these configurations and compare them with conventional configurations using operational data from an existing sewage treatment plant. The best configurations are those that completely replace the existing system with a trigeneration plant that uses all the available biogas and additional natural gas to completely meet the heating demands of the sewage treatment plant.     

Study of a two-bed silica gel–water adsorption chiller: performance analysis

In this study, a lumped parameter simulation model has been developed for analysis of the thermal performance of a single-stage two-bed adsorption chiller. Since silica gel has low regeneration temperature and water has high latent heat of vaporisation, silica gel–water pair has been chosen as the working pair of the adsorption chiller. Low-grade waste heat or solar heat at around 70–80°C can be used to run this adsorption chiller. In this model, the effects of operating parameters on the performance of the chiller have been studied. The simulated results show that the cooling capacity of the chiller has an optimum value of 5.95?kW for a cycle time of 1600?s with the hot, cooling, and chilled water inlet temperatures at 85°C, 25°C, and 14°C, respectively. The present model can be utilised to investigate and optimise adsorption chillers.