Modeling water/lithium bromide absorption chillers in ASPEN Plus

Absorption chillers are a viable option for providing waste heat-powered cooling or refrigeration in oil and gas processing plants, thereby improving energy efficiency. In this paper, single- and double-effect water/lithium bromide absorption chiller designs are numerically modeled using ASPEN. The modeling procedure is described and the results are compared to published modeling data to access prediction accuracy. Predictions for the single- and double-effect designs are within 3% and 5%, respectively of published data for all cycle parameters of interest. The absorption cycle models presented not only allow investigation into the benefits of using absorption chillers for waste heat utilization in the oil and gas industry, but are also generically applicable to a wide range of other applications.     

Heat transfer coefficients in two phase flow for the water/lithium bromide mixture used in solar absorption refrigeration systems

This paper describes the experimental results obtained from the heat transfer in saturated nucleate boiling for the water/lithium bromide mixture flowing upward in a uniformly heated vertical tube, which is the generator of a solar absorption refrigeration system. The concentration range for the mixture was from 48 to 56 wt.% Plots of local and average heat transfer coefficients are shown against solution concentration, heat flux and the temperature difference between the wall tube and the fluid. It was observed that the average heat transfer coefficients increased for the mixture with an increase of the heat flux and with the decrease of the solution concentration and the temperature difference. The average heat transfer coefficients varied from 1.0 to 4.0 kW/m² °C.     

塑料管单效溴化锂吸收式制冷机理论研究

分析了塑料管单效溴化锂吸收式制冷机的理论循环,对塑料管单效溴化锂吸收式制冷机进行了热力计算和传热计算,为塑料管单效溴化锂吸收式制冷机的结构设计及实验研究提供理论依据。     

浅谈溴化锂吸收式制冷机的运转性能

本文详尽介绍了外界因素对溴化锂制冷机性能的影响状况 ,以精确的性能曲线图向读者展示了其运转性能特性     

溴化锂吸收式制冷机采用塑料传热管的研究

提出了在溴化锂吸收式制冷机中采用塑料传热管代替铜传热管,以解决传热管腐蚀及其引起的冷量衰减问题。以1台制冷量为35kW的溴冷机为例,对采用塑料传热管的溴冷机与传统铜管溴冷机相关部件的参数进行比较。通过对溴冷机的传热面积、管道阻力的计算和安全强度的校核,发现采用塑料传热管的溴冷机在技术上是可行的。     

温度参数对升温型溴化锂吸收式热泵性能系数影响程度分析

通过对升温型溴化锂吸收式热泵进行理论分析,得到在相同工况条件下,发生温度变化对系统性能系数的影响程度最大,但小于吸收温度和冷凝温度影响程度之和.并利用焓浓度图,结合前人数据对理论分析进行了验证.     

Ionic liquid based absorption chillers for usage of low grade waste heat in industry

The standard working pairs for absorption chillers, ammonia/water and water/lithium bromide show problematic behaviours like crystallisation and corrosiveness. Because of their convenient solving properties and their low vapour pressure, ionic liquids are a new promising class of sorbents for absorption cooling purposes. In this study, the working pairs water/1,3‐dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and water/1‐ethyl‐3‐methylimidazolium dimethylphosphate ([EMIM][DMP]) are implemented in AspenPlus. The performance of a single effect cycle with these pairs is simulated and compared to results of a cycle with water/LiBr. For [EMIM][DMP] a coefficient of performance (COP) comparable to that of LiBr or even higher (up to 0.85) is found. [MMIM][DMP] shows a smaller maximum COP but a largely wider operating temperature range than LiBr. Results are compared with those of other groups, discrepancies discussed and improvements suggested. Copyright © 2013 John Wiley & Sons, Ltd.     

Comparison of the theoretical performance of a solar air conditioning system operating with water/lithium bromide and an aqueous ternary hydroxide

This paper compares the theoretical performance of the modelling of a solar absorption air conditioning system operating with water/lithium bromide and an aqueous ternary hydroxide mixture consisting of sodium, potassium and cesium hydroxides in the proportions 40 : 36 : 24 (NaOH : KOH : CsOH). In this paper, plots of the coefficients of performance of a solar air conditioning system operating with these two mixtures are presented. The results showed that similar coefficients of performance are obtained for both mixtures, however, it was found that the system operating with the hydroxides may operate with a higher range of condenser and absorber temperatures and the heat delivered by these components can be removed by air.     

Single-stage and advanced absorption heat transformers operating with lithium bromide mixtures used to increase solar pond's temperature

Mathematical models of single-stage and advanced absorption heat transformers operating with the water/lithium bromide and water/Carrol™ mixtures were developed to simulate the performance of these systems coupled to a solar pond in order to increase the temperature of the useful heat produced by solar ponds. Plots of coefficients of performance and gross temperature lifts are shown against the temperatures of the heat supplied by the solar pond. The results showed that the single-stage and the double absorption heat transformer are the most promising configuration to be coupled to solar ponds. With single-stage heat transformers it is possible to increase solar pond's temperature until 50°C with coefficients of performance of about 0.48 and with double absorption heat transformers until 100°C with coefficients of performance of 0.33.     

量子力学方法计算溴化锂水溶液的活度系数及其热力参数

文章基于量子力学理论和超额吉布斯能量方程建立了溴化锂水溶液的活度系数及其热力参数的计算公式,此计算公式形式简单,适用范围广,对于设计溴化锂制冷机十分有用.     

参数变化对LiBr吸收式热泵性能的影响

针对溴化锂吸收式热泵的特点,在一定参数变化范围内研究驱动热源、冷媒水以及冷却水进出口变化对其性能的影响。结果表明,不同参数对COP及具体设备的热负荷、传热温差造成不同程度的影响,在热泵的设计过程中应综合考虑各参数的取值以获得最佳的效果。研究结果为热泵系统的优化设计提供理论支持和参考。     

Exergy analysis of lithium bromide/water absorption systems

Exergy analysis of a single-effect lithium bromide/water absorption system for cooling and heating applications is presented in this paper. Exergy loss, enthalpy, entropy, temperature, mass flow rate and heat rate in each component of the system are evaluated. From the results obtained it can be concluded that the condenser and evaporator heat loads and exergy losses are less than those of the generator and absorber. This is due to the heat of mixing in the solution, which is not present in pure fluids. Furthermore, a simulation program is written and used for the determination of the coefficient of performance (COP) and exergetic efficiency of the absorption system under different operating conditions. The results show that the cooling and heating COP of the system increase slightly when increasing the heat source temperature. However, the exergetic efficiency of the system decreases when increasing the heat source temperature for both cooling and heating applications.     

冷水机组的优化配置

本文利用先进的暖通空调专业软件－ＨＶＡＣＳＩＭ＋,用仿真实验比较了具有不同台数和容量的冷水机组在相同的负荷需求条件下的季节能效比（ＳＥＥＲ）。证明了较好的配置具有明显的节能效果。     

小型太阳能溴化锂吸收式制冷系统的优化设计

小型太阳能溴化锂吸收式制冷机是当今制冷空调业中的研究重点,其中需要解决的关键问题是换热器的合理选择和优化设计,最终达到提高效率、减小体积和节约成本的多重目的。实验室设计的5 kW吸收式制冷机组为板式换热器和管壳式换热器的结合体,经过数值计算模拟,可达到理想效果。     

An evaluation of empirically-based models for predicting energy performance of vapor-compression water chillers

This paper presents an evaluation of six empirically-based models for predicting water chiller energy performance using over 1000 chiller data sets from chiller manufacturers and field measurements. The data sets comprise three broad classifications, including (1) constant condenser and constant chilled water flow, (2) constant condenser and variable chilled water flow, and (3) variable condenser and variable chilled water flow. The regression parameters for each performance model are obtained using least squares method. The criteria for evaluating the predictive ability of models are based on the coefficient of variation of root-mean-square error (CV). Results show that among the six empirically-based performance models for water chillers in this study, the bi-quadratic regression model (CV = 2.2%) and the multivariate polynomial regression model (CV = 2.25%) have the best prediction accuracy for all kinds of data sets. The results of this study can be used as a reference for selecting empirically-based models for the purposes of energy analysis, performance prediction, evaluation of energy-efficiency improvements, and fault detection and diagnosis of water chillers.     

新型太阳能吸收式制冷循环的性能分析

在两级溴化锂吸收式制冷循环的基础上,提出了一种由太阳能驱动的新型吸收式制冷循环,并对其进行性能分析。通过大量计算,分析结果表明,在现有太阳能集热器所能提供的热水温度范围内,新型太阳能吸收式制冷循环有较高的热力系数。该循环系统的中间压力、中间浓度对系统的热力系数和热源可利用温差有较大影响。     

余热回收吸收式制冷集中空调方案研究

为回收大型炼油装置丰富的低温余热用于生活区的夏季集中空调,本文对余热资源状况和生活区集中空调建筑物供冷负荷分别进行了综合标定和统计计算,在分析比较的基础上确定采用余热热水型溴化锂吸收式制冷冷水机组和半集中式风机盘管全水型空调系统,并利用现有双管制热水集中供暖管网和泵站输送空调冷水,可以显著地节约投资。技术经济分析表明,该方案在技术上可行,节能效果和经济效益十分显著,而且可以大大改善厂区的热污染和居民的生活条件。     

Modeling of ammonia absorption chillers integration in energy systems of process plants

A mathematical programming approach is proposed to study the integration of absorption chillers in combined heat and power plants. The aim of this work is to determine the economic viability of the introduction of ammonia absorption chillers in energy systems instead of using the more conventional compression cycles. This procedure selects the best refrigeration alternative taking into account both absorption and compression cycles. To select the most suitable refrigeration cycle for a given refrigeration load, it is not only necessary to model the performance of each cycle, but also to take into account the interactions between the energy system and the considered cycles, optimizing the performance of the global plant. This approach has been implemented in the computer program XV, and tested in an energy plant in the petrochemical complex of Tarragona (Catalunya, Spain). The refrigeration demands to be met are at 0 and −20°C. The results highlighted the benefit obtained with the simultaneous presence of ammonia absorption cycles and a cogeneration based energy plant.     

标准型直燃机在严寒地区应用探讨

介绍了标准型直燃机的分类、原理及长庆至呼和浩特输气管道工程冷冻供热站的设计实例 ,重点论述了标准型直燃机在严寒地区使用的利弊     

冷水机组低温冷却水系统解决方案分析

通过理论分析与实验方法研究了冷水机组冷却水温度和流量调节的方法。结果表明:采用旁通阀调节冷却水温度,不仅能够保证冷水机组安全、高效稳定运行,且能够有效节约能源;采用冷却水变频方式,可以大量减少能耗,但当环境温度低于10℃时,基本不可用。