改进风冷热泵冷热水机组除霜性能的实验研究

通过对一台风冷热泵冷热水机组除霜时使用热力膨胀阀和使用短管直接连通机组高低压侧的对比实验, 研究了不同节流装置对机组除霜性能的影响, 提出了改进风冷热泵冷热水机组除霜性能的一种方法。     

热力膨胀阀与电子膨胀阀对分液性能影响的比较

本文通过比较蒸发器各回路之间的温差，对分液器在热力膨胀阀和电子膨胀阀控制下的分液性能做了实验研究。结果表明在电子膨胀阀控制下分液器的工作性能更好，而且还可以保持较小的蒸发器传热温差。     

Transient and steady-state experimental investigation of flash tank vapor injection heat pump cycle control strategy

Recent research on vapor injection technique has been mostly focused on performance improvement using different system configurations. The flash tank cycle typically shows better performance than the internal heat exchanger cycle. However, the flash tank cycle control strategy is not yet clearly defined. In this study, a novel cycle control strategy is proposed for an R-410A vapor injection flash tank heat pump system and its feasibility was experimentally investigated. The proposed novel cycle control strategy utilized an electronic expansion valve (EEV) for the upper-stage expansion and a thermostatic expansion valve for the lower-stage expansion, and applied an electric heater in the vapor injection line to introduce superheat to the injected vapor by providing a control signal to the upper-stage EEV. Both transient and steady-state system behaviors were studied. The proposed cycle control strategy was found to be able to provide reliable control to the system.     

膨胀阀对陈列柜内温度分布影响的对比实验研究

对热力膨胀阀和电子膨胀阀控制下陈列柜内的温度分布做了实验研究。结果表明，在热力膨胀阀控制下，陈列柜内的温度分布情况与电子膨胀阀相差不大。在目前的实际应用中，热力膨胀阀基本能满足一般客户对陈列柜的使用要求，没有必要大规模进行电子膨胀阀的替代。     

离心式冷水机组变工况运行性能分析研究

以单级离心式制冷压缩机的性能曲线为基础,分析了单级离心式冷水机组的变工况运行性能,在给定的非标准工况下,综合比较了压缩机-换热器-膨胀节流装置在各种配置下的运行性能.从数据对比,说明电子膨胀阀对于离心式冷水机组的变工况运行适应性最好,手动/半自动可调膨胀节流孔板可兼顾变工况性能与制造成本,而固定式膨胀节流装置从综合能效比来讲运行经济性较差.     

制冷装置中膨胀阀的对比研究

为验证自行开发的电子膨胀阀和采用单片机开发的实时控制器的控制效果，针对热力膨胀阀、步进电机型膨胀阀、电磁阀型膨胀阀，进行了多个制冷系统冷启动和稳定工况下变负荷控制的实验研究。结果表明相对于传统的热力膨胀阀，电子膨胀阀更适用于系统综合控制器；连续调节型的执行机构比离散调节型的执行机构更容易使过热度稳定；积分环节大大改善了过热度的控制品质。自行开发的电子膨胀阀和控制器，性能价格比高，与国外同类产品相比，实际的控制效果也有较明显的提高。     

Experimental comparison of electronic and thermostatic expansion valves performances in an air conditioning plant

Adopting electronic expansion valves in air conditioners enables an appreciable energy saving with respect to the same installations equipped with traditional thermostatic expansion valves. This is due to the fact that electronic valves allow a lower condensation pressure in systems equipped with air cooled condensers, which is adjusted to variations in outside air temperature. Furthermore, PID (Proportional–Integral–Derivative) control over the superheating leads to the best use of evaporator under every condition (lower superheating level of the vapour refrigerant), thus increasing the refrigerating capacity.This paper reports on the results of a set of measurements that were carried out from March to November 2006 on the operation of eight direct expansion air conditioners having a total cooling capacity of 120 kW installed at a telephone control room near Bologna (North Italy). Air conditioners are equipped with both thermostatic and electronic expansion valves, alternatively activated by solenoid valves on a daily basis, in order to compare the two systems in the same environment and at similar load conditions. The annual analysis is supplemented by a transient simulation program to simulate the behaviour of the system in the two different operating modes in different European climates, in order to evaluate the energetic and economic advantages of electronic valve.     

Cycling losses in refrigeration equipment: An experimental evaluation

Cycling losses may be defined as those inefficiencies that reduce the performances of units during the transient period. They may be quantified by comparing the Energy Efficiency Ratio (EER) of a cycling unit and the EER of the same unit working continuously.The on-off control is the most widespread strategy for modulating; therefore, a reliable evaluation of cycling losses is fundamental to assess the EER of the system. The mentioned losses have been experimentally evaluated on a test rig, and logged data demonstrate a loss up to 13% with respect to steady operations when the load factor is lower than 10% and a Thermostatic Expansion Valve (TEV) is used. The insertion of a solenoid valve in series with the TEV can reduce the losses but the best results are obtained by using the Electronic Expansion Valve (EEV) instead of the TEV.     

电子膨胀阀在低温装置上降温特性的试验研究

为了研究电子膨胀阀在低温条件下的应用特性，研制了低温试验台，并在试验台上并联安装了电子膨胀阀和热力膨胀阀，对两种膨胀阀在相近工况下进行降温特性的对比性试验。根据实验结果进行分析研究，可以看出电子膨胀阀在低温条件下的控温曲线是非常平稳的，并可调节电子膨胀阀的不同开度，达到不同的降温速率及终温。另外通过改变电子膨胀阀开度，研究了在变开度情况下，对制冷系统循环参数的影响。     

Numerical study on the steady state and transient performance of a multi-type heat pump system

Numerical methods are provided to analyze dynamic characteristics as well as steady-state performance of a multi-type heat pump system. Lumped parameter method was applied to simulate the compressor and expansion device. Additionally, fully distributed method was used for analyzing the condenser and evaporators. The transient terms in the governing equations for heat exchangers were solved adopting the wave equation solutions. The simulation results predict the steady-state performance of a heat pump system with the deviation of ±10%. The transient simulation showed satisfactory responses of temperatures and pressures for various compressor speeds or expansion valve openings. From the results, it was shown that the operating conditions of secondary fluid of one indoor unit had minor influence on the performance of the other unit, while opening of expansion valve affected the transient responses of both evaporators significantly.     

大型风冷冷水机组性能评价系统节能性研究

针对大型风冷冷水机组性能评价系统能耗高的现状,分析评价系统的主要能耗构成,指出传统大型风冷冷水机组性能评价系统的高能耗成因,提出一种新型变容量全回收风冷冷水机组性能评价系统。新型评价系统省去样机恒温水箱、冷冻水箱和换热水泵,将变容量水冷乙二醇冷冻机组与经济器(冷却塔协同功能板换)串入闭式回路实现一级温控,结合变频泵与调节阀实现二级温控。实证表明:相比传统评价系统,应用双级温控的新型评价系统相近工况过渡耗时减少为前者的70%,综合能耗降为传统的75%,运行稳定性良好,节能效果显著。     

离心式冷水机组油温智能控制系统的设计研究

介绍一种离心式冷水机组油温智能控制系统,以西门子S7-200系列PLC和ProFace文本显示器组成控制系统的核心,以电子膨胀阀代替传统意义的孔板控制冷却油温的制冷剂流量,达到精确控制油温的目的。与传统油温控制系统相比,该系统对离心式冷水机组运行过程中精确控制油温、降低压缩机壳体表面温升、减小机组振动幅度有显著作用。     

节流短管在大容量空调机组中的应用

对在大容量空调机组中应用节流短管作为制冷系统节流机构的可行性进行分析,并通过试验方法对在同一款空调机组上分别采用节流短管组件、毛细管和热力膨胀阀作为节流机构时的整机性能进行测试和对比。试验结果表明,空调机组采用多分路节流短管组件作为节流和分液机构时,各回气支路温度的标准偏差仅为1.39℃,其分液均匀性明显优于采用热力膨胀阀或毛细管节流;此外,制冷量比采用毛细管和热力膨胀阀分别提高5.7%和4.2%,能效比也比采用毛细管和热力膨胀阀分别提高5.5%和6.2%,可有效地提高蒸发器的换热能力和整机能效比。     

电子膨胀阀在冷藏库制冷系统中应用的展望

本文通过阐述电子膨胀阀与冷藏库的传统节流装置——热力膨胀阀之间的差别，并从节能和机电一体化的角度出发，分析了电子膨胀阀在冷藏库制冷系统中应用的可行性。     

多联式空调制冷系统动态仿真研究

为了研究多联机制冷系统的动态性能,建立了基于简化气液两相流体网络的多联式空调制冷系统动态仿真模型.其中,压缩机和电子膨胀阀采用稳态模型,蒸发器和冷凝器采用移动边界动态仿真模型,气液分离器采用动态模型.采用Matlab和Simulink为仿真工具,对多联机动态仿真模型进行求解,并通过一套具有四台室内蒸发器的多联机系统的实验结果进行验证和改进.结果表明,该动态仿真模型能够准确预测多联机动态过程的变化趋势,并保持很高的计算精度,蒸发温度、冷凝温度和过热度的误差都在1.0℃左右,排气温度误差小于3.0℃,可以用于多联机动态性能分析,并可作为开发和优化多联机控制策略和控制算法的有效工具.     

Thermostatic valve control using a non-azeotropic refrigerant, isobutane/propane mixtureRégulation d'un détendeur thermostatique utilisant un mélange d'isobutane et de propane comme frigorigène non azéotropique

This article describes the evaluation and comparison of a conventional R12 cross-charged thermostatic valve and an electronic expansion valve using a non-azeotropic refrigerant mixture (NARM); isobutane/propane mixture (CARE30). The superheat temperature setting on an expansion valve needs to compensate for the temperature glide associated with a non-azeotropic refrigerant as these can be of similar magnitude. It is also advisable to increase the superheat setting to make allowance for change in refrigerant composition as a result of preferential refrigerant/oil solubility. The majority of refrigeration systems operate at fixed evaporating temperatures, hence, once superheat setting is trimmed during commissioning, then there should be no further problems associated with evaporation of a non-azeotropic refrigerant provided the system is leak-tight. An R12 expansion valve with a factory superheat setting of 5°C tested over a wide range of evaporating temperatures proved satisfactory in operation with CARE30 after increasing the superheat temperature screw setting equivalent to 5°C.     

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%。     

Control of flash gas bypass MAC system with emphasis on start-ups and transients

Most of the previous research on flash gas bypass (FGB) focused on performance improvement in steady state and demonstrated that compared to direct expansion mode (DX), FGB mode have better performance. However, the control strategy of flash gas bypass system and dynamic behavior during start-ups and transients were not yet clearly defined and investigated. In this paper, a novel control strategy has been proposed for an automobile air conditioning system operating in flash gas bypass mode with R134a as the refrigerant. The proposed control strategy utilized an electronic expansion valve (EV) for the control of subcooling from condenser outlet and a bypass valve (BV) for superheat from compressor inlet. Both start-up and transient system behaviors were studied. The experimental results showed that the proposed cycle control strategy was found to be able to provide reliable control to the system. In addition, proper sizing of bypass valve and flash gas bypass tank have also been studied.     

电子膨胀阀流量特性试验台的研制

为方便对电子膨胀阀进行性能测试及试验研究,需研制调试方便、易于操作的电子膨胀阀流量特性试验台。通过参考国内机械行业标准中有关膨胀阀的测量标准,基于其中的方法设计了适合于测试电子膨胀阀流量特性的试验装置,实现了电子膨胀阀与变频制冷系统的合理匹配与节能控制。     

Comportement dynamique de détendeurs thermostatiques de machines frigorifiquesBehaviour of a thermostatic expansion valve in non-steady state for a refrigerating machine

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.