Simulation of industrial refrigeration plants under variable load conditionsSimulation d'installations frigorifiques industrielles à des charges variables

A method to simulate industrial refrigeration systems with several independent, time-variable heat loads is described. The method uses a combination of ordinary differential and algebraic equations to describe both the refrigeration plant, and its interaction with the product in each application. Numerical integration of the differential equations with respect to time allows the various processes to be simulated. Models for freezers, chillers, cold stores and controlled atmosphere work areas are discussed. Assumptions made in these models are realistic from a practical viewpoint, so provided accurate data are available close correlation between predictions and measurements would be expected. The simulation could have applications in both refrigeration system and control system design as it will predict the interactions between different parts of a plant when operating under time-variable conditions. When considering system changes or changes to product specifications the suitability of particular alternatives can be assessed by simulating each in turn.     

Simple mathematical model for predicting the transient behaviour of an ice-bank system

The time-variable performance of a Refrigerant 22 ice-bank system was simulated by a dynamic model which was derived by assuming that heat transfer was always the limiting process, and which thus ignored hydrodynamic processes. The model comprised four ordinary differential equations describing the position of the ice front, the water temperature, and the refrigerant evaporation and condensation temperatures, each of which was derived by energy balance, plus a number of algebraic equations. Measured plant performance was accurately predicted except immediately after start-up, and in circumstances in which the assumption that the dynamics of refrigerant flow did not exert any controlling influence on the overall process dynamics was inadequate (for example, when the thermostatic expansion valve operation becomes unstable). The model requires only data that should be readily available or can be easily estimated, and thus it is suitable for analyses in the design of ice bank systems to handle time-varying conditions. Simple dynamic models ignoring hydrodynamics can be adequate in circumstances where the main source of variation arises beyond the refrigeration circuit itself.     

制冷循环稳态仿真的联立模块法

为了克服顺序模块法和联立方程组法的各自缺点,融合各自优点,在制冷循环稳态仿真中引入联立模块法。首先按照功能独立原则对制冷循环进行模块化分解,制冷循环的结构模型由部件模块之间的连接关系表示,其中每个连接对应一组连接方程组;然后联立部件模块方程组、连接方程组和制冷剂总质量守恒方程组成制冷循环模型的模块方程组;最后采用离散数值差商计算Jacobi矩阵,用带松弛因子ω的New-ton法求解,另外采用数值延拓法拓展收敛域。联立模块法通用性和实用性好,可以解决模块共享与知识产权保护之间的矛盾,有利于制冷循环仿真开发的专业化分工和社会化协作,提高开发质量和效率。     

CO_2载冷剂氨双级压缩制冷系统及其性能分析

针对氨制冷系统在实际应用中存在安全隐患的问题,总结提高系统安全性的方法和途径,介绍以CO2为载冷剂的半封闭式氨制冷系统的组成及其应用。对以CO2为载冷剂的氨双级压缩制冷系统性能进行理论计算与对比分析,结果表明：在蒸发温度为-50~-30℃范围内,与NH3/CO2复叠式制冷系统相比,CO2载冷剂氨双级压缩制冷系统的EER约高5.7%~10.8%。     

船用跨临界循环二氧化碳制冷系统性能仿真

本文建立了船用二氧化碳跨临界循环制冷系统的稳态仿真数学模型,用此模型计算和分析了内部和外部参数分别变化时跨临界二氧化碳制冷系统的工况特性.本文的研究结果可为跨临界二氧化碳制冷系统的产品开发和系统控制提供依据.     

冷热互联系统研究及其能效计算准则讨论

随着节能减排的不断深入和能源效率的逐步提高,同时利用冷量和热量的冷热互联系统将得到进一步的推广应用。与传统的制冷系统和制热系统的能效计算相比,冷热互联系统能综合利用冷热两部分的能量,原来单独冷、热量的能效计算法则是否适用于新的系统需要重新考虑。本文构建了复叠机组和热泵机组互联(A系统)、以及常规制冷机组和热泵互联(B系统)两种冷热互联系统,提出了3种能效计算方式,通过具体实验操作和分析给出了3种系统的COP计算方式和结果,其中第3种计算方法综合考虑了制冷系统制冷量和热泵系统制热量作为收益,将整个系统的轴功率看作补偿能量,最为合理。     

渔船动力余热制冷技术

渔船通常需要带冰或使用压缩式制冷来满足渔获冷藏保鲜的需要,而渔船发动机尾气中有大量的热能被排放到环境中去,利用渔船发动机尾气余热制冷是一种既经济又节能的好方法。本文介绍了吸附式、吸收式和喷射式三种热能驱动的制冷循环,并针对渔船制冰工况对这三种循环在渔船中应用的优缺点进行了分析;重点讨论了使用喷射式制冷技术对渔船现有压缩式制冷系统进行改造的可行性。研究结果表明,将喷射制冷与压缩制冷结合,可减少渔船制冷系统燃料消耗54.5%,在1年内即可收回改造成本。     

多回路制冷空调综合型实验系统的研制

制冷系统是多输入、多输出的系统,而且各操作参数相互关联.随着环境和室内热负荷的变化,制冷空调系统通常是在变工况条件下运行.为全面研究制冷系统的实际工作特性,研制开发了变频蒸气压缩式多回路制冷空调综合性实验系统,通过调节连接蒸发器和冷凝器的空气回路可以在任何时间模拟实现全年的运行工况,而不受季节的影响.详细介绍了实验系统的设计原理、调节方法、技术参数和数据采集系统.利用该实验系统既可获得参数间的动态关联特性,还可进行单体设备的性能测试以及不同控制策略的比较实验,为制冷系统动态仿真研究、各部件的合理匹配和优化运行控制策略提供实验基础.     

Numerical simulation of a variable speed refrigeration system

This work presents two numerical models to simulate the transient and steady state behavior of a vapor compression refrigeration system. The condenser and the evaporator were divided into a number of control volumes. Time dependent partial differential equations system was obtained from the mass, energy and momentum balances for each control volume. As the expansion valve and the compressor both have very small thermal inertia, the steady state models were applied for these components. Transient and steady state models numerical predictions were compared and good agreement was found. Further simulations were performed with the objective of verifying the possibility of controlling the refrigeration system and the superheating of the refrigerant in the evaporator outlet by varying the compressor speed and the throttling valve sectional area. The results indicate that the proposed models can be used to formulate an algorithm for controlling a refrigeration system.     

以[mmim]DMP-甲醇为工质对的吸收式制冷循环研究

采用离子液体[mmim]DMP-甲醇作为吸收式制冷系统工质对,运用文献提出的[mmim]DMP-甲醇二元溶液经验方程进行制冷循环计算研究,并将此系统的工作压力、COP等与相同工况下的溴化锂-水、氨-水制冷循环进行比较。研究结果表明：[mmim]DMP-甲醇工质对制冷系统工作压力要求适中,COP稍高于NH3／H2O系统,低于H2O／LiBr系统;[mmim]DMP-甲醇溶液对金属无腐蚀,其适用范围要大于H2O／LiBr系统,具有一定的应用价值。     

Optimum staging of multistage exo-reversible refrigeration systems

A general staging model is developed to optimize multistage exo-reversible refrigeration systems affected solely by internal irreversibilities. Under some reasonable assumption, the same high to low temperature ratio is found at each stage so as to maximize the coefficient of performance of a multistage combined refrigeration system, where each stage is subjected to an independent refrigeration subcycle. This model is then applied to the optimum staging of two configurations of multistage thermoelectric coolers, which are the ones with different and identical electrical current flowing through each stage, respectively. For both the two cases, the optimum stage temperatures are numerically proved to follow from the ideal staging well. Detailed optimum staging parameters of both types of thermoelectric coolers are calculated with commercially available thermoelectric (TE) materials. The temperature dependence of TE properties has been taken into account.     

微型制冷系统研究进展

得益于制造技术的进步和传热传质理论的发展完善,制冷系统不断向小型化、便携化发展,近年来出现了不少形式的微型制冷系统。本文介绍了3种主要的微型制冷系统:蒸气压缩制冷、吸收式制冷和半导体制冷系统。结合近年来国内外文献,介绍了制冷系统微型化的最新发展状况,并对各种系统的优缺点进行对比,重点介绍了微型蒸气压缩制冷系统及其核心部件—微型压缩机的发展现状。最后论述了制约制冷系统微型化的瓶颈问题,提出了微型制冷系统的发展方向。     

自然复叠制冷系统初探

自然复叠制冷系统是一种采用多元混合工质的制冷系统，它使用单台压缩机，通过自然分离、多级复叠的方法，在高沸点组分和低沸点组分之间实现了复叠，在到了制取低温的目的。详细介绍了自然复叠制冷系统的原理，将自然复叠循环与单级压缩、双级压缩、复叠式进行了分析比较，指出自然复叠循环的优势。文中给出了自然复叠制冷系统的优化原则，并将用CFC作制冷剂的自然复叠循环的计算结果和两级压缩循环、复叠循环的计算结果进行了比较，对用非CFC物质作制冷剂的自然复叠制冷系统进行了分析，说明自然复叠制冷系统具有较大的实用价值。     

船舶制冷装置高压继电器动作的思考

运用故障树定性分析方法，分析船舶制冷装置中高压继电器动作的故障树模型，探讨了船舶制冷装置高压继电器动作的预防途径，为制冷装置的安全管理提供参考。     

Application of micro-electronics to refrigeration and heat pump technology

Micro-electronics will have large effects on both the design and operation of refrigeration and heat pump installations. Developments of artificial intelligence will enable designers to draw on far more extensive data banks and to work interactively at each stage of the design using graphic displays and spoken instructions. In addition, computers will be used not only to achieve better control of plant but for diagnosis of faults and the scheduling of maintenance.     

Economic optimization of refrigeration plants

The economic optimization of refrigeration plants is discussed. In the optimization procedure it is often necessary to compare several different optimized concepts of the refrigeration system, eg screw compressors versus reciprocating compressors. Optimization procedures are discussed and the optimum values found by the computer program are compared with results calculated with Bäckström equations. Estimation of future changes in the cost of electricity and water, and rates of interest and inflation have to be included in the optimization procedure. Even so, it may be difficult to persuade the purchaser to afford the optimum plant.     

Economic optimization of refrigeration plantsOptimisation économique des installations frigorifiques

The economic optimization of refrigeration plants is discussed. In the optimization procedure it is often necessary to compare several different optimized concepts of the refrigeration system, eg screw compressors versus reciprocating compressors. Optimization procedures are discussed and the optimum values found by the computer program are compared with results calculated with Bäckström equations. Estimation of future changes in the cost of electricity and water, and rates of interest and inflation have to be included in the optimization procedure. Even so, it may be difficult to persuade the purchaser to afford the optimum plant.     

一种新型便携式制冷保温容器的试验研究

研制一种新型便携式制冷保温容器制冷系统，主要用于保存血液。确定半导体制冷核心部件的参数，如半导体制冷片的选择、容器内部结构及系统的匹配。通过性能试验进行优化，对影响半导体制冷的因素进行讨论。实验结果表明，将半导体制冷应用于保温容器是可行的，而且是有利的。该研究结果对半导体制冷技术在小型制冷保温容器中的进一步研究和应用具有一定的指导意义。     

低温液体冷却循环器的研究与开发

根据低温生物、生化实验研究和产品小试时应用低温条件的特点，提出机械制冷的冷却循环器，讨论了工作原理和制冷量计算，对其制冷系统和温度控制进行介绍。     

Experimental verification of a mathematical model for simulation of industrial refrigeration plantsVérification expérimentale d'un modèle mathématique de simulation des installations frigorifiques industrialles

A mathematical model, proposed for simulation of food refrigeration processes, was tested against experimental data collected in a New Zealand meat processing plant which had a total refrigeration capacity of 2.5 MW. Predicted air temperatures in freezing and chilling operations followed the same trends as measured data. Differences were shown to be more attributable to uncertainties in data than to deficiencies in the formulation of the mathematical model. The model is considered suitable for use in simulation of a wide range of food refrigeration processes. Such simulations provide useful information about plant performance that cannot be obtained by steady state analysis. Predictions were worst for short times immediately following step changes in plant operation; should more accurate simulation of these periods be required a different form of mathematical model is needed.