Comportement dynamique de détendeurs thermostatiques de machines frigorifiques

A good adaptation of refrigerating machine components operating with a variable-speed compressor requires knowledge of the dynamic behaviour of each component, more particularly of the expansion valve. The behaviour of various thermostatic expansion valves (ballast charge, adsorbent charge and maximum operating pressure or MOP charge) has been studied for compressor speed variations (between 20% and 200%) of a refrigerating machine, with R22 as refrigerant, and a cooling capacity of 6kW. This study has shown the disadvantages of these expansion valves, during dynamic operation, without modification of the static superheat. The decrease of the evaporating pressure, consecutive to a step or a ramp of the compressor speed, can lead to the suction of a two-phase fluid in the compressor. This phenomenon takes place particularly either for the low evaporating temperatures or for great variations of the compressor speed, more than 50%. The stable operating limits of different thermostatic expansion valves have been determined as a function of the evaporation temperature and the rotational speed of the compressor during the non-steady state.     

Non-linear predictive control of a vapour compression cycle

A potential energy saving can be obtained by a global optimal setting of each actuator in a vapour compression cycle. This paper describes a predictive optimal control algorithm applying this strategy. At each step, an optimal command profile is computed, upon predictions of variables system evolution, using a simple non-linear model of a vapour compression cycle. Choice of this profile is based on a multiple criterion including cycle efficiency and technological constraints. The approach is experimentally validated on a pilot scale refrigeration plant with variable speed compressor. Trials have been performed and showed a meaningful energy saving.     

基于PLC的模糊参数自整定冷库控制系统研究

针对冷库制冷系统大滞后、大惯性、时变性的特点，提出基于PLC的模糊PID参数自整定控制算法。该技术既充分利用了PLC的软硬件资源，又提高了控制的智能化程度。模糊PID技术与变频技术相结合应用于冷库制冷系统，实现了压缩机的变频调速，有效地节约了能源，提高了经济效益。     

制冷系统变容量智能控制的理论及实验研究

为了提高变容量调节制冷系统过热度的控制精度,建立简单易行的过热度控制方法,在考虑各种影响因素的前提下,提出了基于传统PID控制策略的过热度智能控制策略。并以某恒温恒湿冷库为研究对象,验证了所提过热度控制策略的实际控制效果,并与热力膨胀阀的控制效果进行对比分析。实验结果表明:智能控制策略较传统PID控制策略动态响应快,超调量小,振荡时间短;压缩机频率变化作为干扰量提前输入,有利于过热度的稳定;采用智能控制策略对过热度的控制效果明显优于热力膨胀阀,冷库降温时间缩短37.14%。     

一种高效节能的近共沸制冷剂KLB—1制冷剂替代R22在小型冷库中的应用

用节能型ＫＬＢ－ １ 制冷剂替代Ｒ２２, 作为小型冷库的制冷工质, 并与Ｒ２２ 为工质的相似冷库作比较,在设备未更动和未调换润滑油的情况下,测定了吸排气压力,吸排气温度和能耗情况。结果表明：ＫＬＢ－ １ 具有节省能耗的效果,可以代替Ｒ２２ 直接使用。     

Behaviour and performances of R502 alternative working fluids in refrigerating plants

This is an experimental study that aims to evaluate both general characteristics and system performances of the most credited fluids that are likely to substitute for R502 in a refrigeration plant. R402A, R402B, R403B and R408A (still containing HCFC) and R404A, R407A and FX40 (chlorine free) have been tested. Generally, both of them have showed performances very close to those of R502 except R403B, whose COP has been found to be about 8% lower than that of R502.     

冷藏库的节能技术

分析了影响冷藏库负荷的主要因素;从冷藏库的设计、施工和制冷装置的操作运行等环节,提出了冷藏库的节能措施。     

Formation Conditions of Clathrates Between HFC Alternative Refrigerants and Water

There are two promising candidates as alternative refrigerants for air-conditioners and heat pumps. The first is R407C, which is composed of HFC-32 (23 mass%), HFC-125 (25 mass%), and HFC-134a (52 mass%). The second is R410A, which is composed of HFC-32 (50 mass%) and HFC-125 (50 mass%). In this study, formation conditions of clathrate compounds between water and HFC alternative refrigerants such as HFC-32, HFC-125, HFC-134a, and their mixtures, R407C and R410A, were investigated. Phase diagrams of clathrates of these HFC alternative refrigerants and their mixtures were determined. From the phase diagrams, the critical decomposition temperature and the critical decomposition pressure were determined. The relationship between the critical decomposition points for the clathrates of HFC-32, HFC-125, HFC-134a, R410A, and R407C were studied. It is found that R407C and R410A form clathrate compounds with water under the evaporating temperature condition in the refrigeration cycle of air-conditioners and heat pumps.     

Performance representation of variable-speed compressor for inverter air conditioners based on experimental data

Variable speed control of compressors is one of the best methods to regulate the capacity of heat pumps and air conditioners. An analysis is conducted for modeling the variable speed compressor for simulation of inverter air conditioner and heat pump. Having scattered the real operation performance of inverter compressor into infinite operation performance of constant speed compressor, the map-based method is utilized to fit the performance curves of inverter compressor. The model is built at the basic frequency and the map condition as the second-order function of condensation temperature and evaporation temperature. Then it is corrected by the compressor frequency as the second-order function of frequency and by the actual operating condition as the actual specific volume of the suction gas. This method is used to set up simulation models of three different compressors. Compared with the data provided by the compressor manufacturers, the average relative errors are less than 2, 3 and 4% for refrigerant mass flow rate, compressor power input and coefficient of performance (COP), respectively. This model of variable speed compressor is suitable for the simulation of inverter air conditioner and heat pump systems. Based on the experimental data and simulation model, the frequency at zero mass flow rate and power input at zero frequency are discussed and the relation between COP and compressor frequency is analyzed.     

Experimental investigation of the performance of R22, R407C and R410A in several capillary tubes for air-conditioners

The objective of this study is to present test results and to develop a dimensionless correlation on the basis of the experimental data of adiabatic capillary tubes for R22 and its alternatives, R407C (R32/125/134a, 23/25/52 wt.%) and R410A (R32/125, 50/50 wt.%). Several capillary tubes with different length and inner diameter were selected as test sections. Mass flow rate through the capillary tube was measured for several condensing temperatures and various degrees of subcooling at the inlet of each capillary tube. Experimental conditions for the condensing temperatures were selected as 40, 45 and 50°C, and the degrees of subcooling were adjusted to 1.5, 5 and 10°C. Mass flow rates of R407C and R410A were compared with those of R22 for the same test conditions. The results for straight capillary tubes were also compared with those of coiled capillary tubes. A new correlation based on Buckingham π theorem to predict the mass flow rate through the capillary tubes was presented based on extensive experimental data for R22, R407C and R410A. Dimensionless parameters were chosen considering the effects of tube geometry, capillary tube inlet conditions, and refrigerant properties. Dimensionless correlation predicted experimental data within relative deviations ranging from −12% to +12% for every test condition for R22, R407C and R410A. The predictions by the developed correlation were in good agreement with the results in the open literature.     

基于R600/R290混合制冷剂的立式冷冻箱的降温能力试验研究

为优化以混合制冷剂为工质的立式冷冻箱制冷系统降温能力,对使用R600/R290混合制冷剂的立式冷冻箱在32℃环境温度下进行降温能力试验,研究混合制冷剂充注量、制冷剂各组分配比、毛细管流量及风机转速对其性能的影响.结果 表明:混合制冷剂充注量过大会削弱制冷系统降温能力,并使压缩机功率增加;增大毛细管流量、风机转速及混合制...     

冷冻冷藏用制冷剂R404A的替代品对比分析

基于现有的R404A涡旋式压缩机,模拟分别采用R404A,R407A,R407F,R134a和R1234ze制冷剂时的压缩机性能,计算5种制冷剂系统的理论循环COP,并对各典型工况进行对比分析。计算结果表明,R407A和R407F可直接应用于R404A压缩机,而R134a和R1234ze替代R404A时压缩机设计变更较大,4种制冷剂系统能效均较R404A系统有较大提高。     

The surface tension of HFC refrigerants and mixtures

The surface tension of the refrigerants R32, R125, R134a, R143a and R152a, as well as the binary refrigerant mixtures R32-R125, R32-R134a, R125-R134a, R125-R143a, R125- R152a, R143a-R134a and R134a-R152a, and the commercially available ternary mixtures R404A and R407C was measured across the temperature range from −50 to 60°C using a measuring unit based on the capillary rise method. Different formulations for calculation of the surface tension of the binary and ternary mixtures on the basis of the surface tension of the pure refrigerants were tested. With an approach based on mass proportions in the mixture, a good correspondence between the measured and calculated values was achieved.     

多制冷剂、宽电压范围工业空调用转子式压缩机设计

针对客户希望同一款工业空调能够实现不同制冷量的要求,提出一种多制冷剂、宽电压范围转子式压缩机,并通过理论分析和试验研究多制冷剂、宽电压范围定速压缩机的设计要点,开发一款电源为三相380~415 V 50 Hz/380~460 V 60 Hz,制冷量在3.9~9.5 kW范围内可兼容R410A/R407C/R134a这3种制冷剂的转子式压缩机,并已实现批量生产。     

变频压缩机在冰箱中的节能技术分析

本文通过对变频压缩机的研究,以及变频压缩机节能分析,了解变频压缩机及变频板产生的功耗对节能的影响。通过采用仿真软件对变频压缩机在冰箱各种环境温度下的节能效果进行分析,研究如何提高变频压缩机的节能效果。     

Calculation of thermodynamic properties of R407C and R410A by the Martin–Hou equation of state — part I: theoretical development

A theoretical development of the thermodynamic properties of two mixtures of hydrofluorocarbon (HFC) refrigerants, i.e. R407C and R410A (in the superheated vapour state), is carried out. The modelling is based on the Martin-Hou equation of state, which has long been used for pure hydrofluorocarbons (e.g. R134a) with good results. Since R407C and R410A are very well investigated refrigerants, the analytical procedure here derived concerns with those thermodynamic properties of R407C and R410A (in the superheated state) that are not published in the current specialised literature. They are: compressibility factor, isentropic and isothermal compressibility, volume expansivity, isentropic and isothermal exponent, speed of sound and Joule–Thomson coefficient. These properties may be used as a theoretical basis for research into the optimal HFC-mixture for compressor efficiency and for performing cycle calculations in the vapour-phase region for systems working with R407C and R410A.     

涡旋变频压缩机

本文介绍了涡旋变频压缩机的主要特点 ,及其在工程实践中的应用实例 ,包括多联机组和低温热泵等 ,分析了涡旋变频压缩机在节能和舒适性等方面的突出优势 ,并指出了影响其使用的关键问题 ,为合理、可靠、高效地使用涡旋变频压缩机提供了切合实际的指导     

R290/CO2复叠式制冷系统的性能实验

通过对R290／C02复叠式制冷系统的性能实验,对低温循环用CO2作为制冷工质,高温循环分别用R22和R290为制冷工质的性能进行比较,结果表明,随着蒸发温度的升高,冷凝温度的降低,R290／CO2复叠式制冷系统的最佳质量流量比增大,COP增加。随着高温循环压缩机入口温度的升高,R290压缩机的功耗略高于R22压缩机的功耗,R290循环的COPh要高于R22循环的COPh。结果表明自然工质R290／CO2复叠式制冷系统具有很好的发展前景。     

Mechanical refrigeration using an ejector-injector to transfer the working fluid from the evaporator to the condenser

The refrigeration plant described in this paper uses an ejector-injector instead of a compressor to pump the freezing mixture from the evaporator to the condenser. A pump draws the liquid from the condenser and pumps it to another vessel. Before the ejector-injector, a heat exchanger preheats the refrigerating fluid to speed up the mixing with steam ejected from the evaporator. The steam is compressed using kinetic energy in the ejector-injector and the pump supplies a discharge pressure to operate the plant. The heat transfer fluid, the condensing and evaporating pressures and the energy losses determine the operating features of the plant. Energy saving is obtained using such an ejector-injector and it provides a simple method of refrigeration. The operating conditions were optimized in this study and the feasibility of the plant was confirmed.     

Simulation and measurement on the full-load performance of a refrigeration system in a shipping containerSimulation et mesures de la performance d'un système frigorifique d'un conteneur maritime entièrement chargé

A mathematical model of a refrigeration system in a shipping container has been developed to allow for full-load simulation of its thermal performance. Sub-models are created on the key components: compressor, evaporator, condenser, and thermostatic expansion valve. The sub-models are then coupled by appropriate mass and energy transfer relations to form the full model. Comparison with a series of cooling capacity tests conducted on a 2.2 m (40 ft) fullscale container housed in a temperature-controlled environmental test chamber indicates good agreement, with simulation results being within ±10% uncertainty of measurements.