螺杆式冷水机组性能分析

为预测螺杆冷水机组在不同结构参数下的变工况特性，提出了基本螺杆冷水机组(I型)、带经济器一级节流螺杆冷水机组(Ⅱ型)和带经济器二级节流螺杆冷水机组(Ⅲ型)变工况稳态仿真模型，其主要部件模型包括不带经济器运行的压缩机、带经济器运行的压缩机、冷凝器、电子膨胀阀、以及蒸发器。仿真结果表明：I型冷水机组的性能可以通过调节膨胀阀开度得到明显的改善；Ⅱ型和Ⅲ型的COP比I型都有明显提高；而Ⅲ型的性能最优，名义工况下的COP约高出Ⅰ型约8％．变工况下性能更为稳定。     

螺杆冷水机组动态仿真

给出了螺杆冷水机组动态过程模型，其中，壳管式冷凝器和满液式蒸发器被分成制冷剂侧、管壁、壳体以及水侧等四个控制容积，针对每个控制容积建立了质量或能量平衡的微分方程，由于螺杆压缩机和电子膨胀阀具有较小的热惯性，因而采用稳态模型描述压缩过程和膨胀过程，通过“自适应步长”方法实现了系统仿真，仿真结果与测试数据吻合良好。     

谈谈带经济器螺杆制冷压缩机耗功的计算——读“带经济器螺杆制冷压缩机的过程分析及系统设计计算”一文的体会

“带经济器螺杆制冷压缩机的过程分析及系统设计计算”(下简称为“设计计算”)一文(见制冷学报1985年第3期),首次考虑了中间补气过程始末螺杆压缩机容积的变化,从而提出了整个压缩过程可分成一级压缩、等容绝热充气、等压放气和二级压缩四个阶段的假说,见图1。这在带经济器制冷循环节能本质的定量分析方面,应该说是更进了一步。然而,文中关于压缩机耗功的求法,值得商讨。“设计计算”一文认为,压缩气体消耗的机械功包括三部分,即一级压缩过程、二级压缩过程的技术功和     

带闪蒸型经济器的风冷螺杆热泵机组性能的实验研究

研究了带闪蒸型经济器风冷螺杆热泵机组对制热性能的影响,理论分析了补气压力的变化对机组制热性能的影响。研究表明,带闪蒸型经济器热泵螺杆机组制热量随经济器的补气压力的减小而增大,压缩机功率也随经济器的补气压力的减小而增大,压缩机的COP随着经济器的补气压力的升高先升高再降低,存在最佳效率的补气压力点。实验测试了比最佳补气压力点偏高的经济器补气压力对机组性能的影响,理论计算结果和实测数据吻合良好。     

中间充气涡旋制冷压缩机

美国谷轮压缩机公司Warren L，Beeton和Hung M．Pham在美国供暖制冷空调工程学会杂志上发表文章，介绍一种新型制冷节能技术——带经济器的中间充气涡旋压缩机。文章指出，目前大型制冷用螺杆压缩机和多级离心压缩机都采用中间充气来实现经济器循环，而小型全封闭压缩机则尚无此种技术。最     

经济器对压缩制冷循环影响分析

通过对空调工况下R134a和R22常用制冷工质的螺杆制冷压缩机带经济器后的机组性能提高情况进行了数值模拟计算。分析了压缩机补气口位置、经济器传热温差、冷凝器出口过冷度和工质类型对机组性能的影响。另外,对带经济器螺杆制冷循环系统进行试验测试,得到了普通单级螺杆循环与带经济器螺杆循环在空调工况下的制冷量、耗功、性能系数的数据,并与模拟计算的结果进行比较分析。结果表明:螺杆制冷循环系统增设经济器以后,系统性能在某补气位置存在最佳值;经济器的换热性能越高、冷凝器出口过冷度越小、蒸发温度越低,系统性能提高的程度就越好;以R134a为制冷工质的系统的性能系数增长率高于以R22为工质的情况。     

带经济器螺杆制冷压缩机的过程分析及系统设计计算

本文在论述带经济器螺杆制冷机制冷系统工作过程的基础上,着重分析压缩机的压缩过程,得到整个压缩过程包括四个阶段;分析并给出求取最大制冷系数下补气压力、补气孔口位置的一般方法。实例计算表明该计算方法可供设计时使用。     

螺杆制冷压缩机热力完善度的指数律

以螺杆制冷压缩机在国际标准试验台上的试验数据为基础；对螺杆压缩机热力完善度－绝热效率ηｓ运用统计方法建立数据模型，得到了较为理想的指数规律。经检验，该模型可用于工程设计计算。     

带经济器螺杆制冷循环系统的研究

从带经济器螺杆制冷循环系统的工作机理山发,本文分析了现有理沦模型的缺陷,导出了新的数学模型。并具体分析、求解了R717、R22、R12、R502等四种常用工质、经济器传热温差、螺杆压缩机泄漏和喷油等实际因素对带经济器制冷机性能的影响。实验验证了该模型的正确性,同时肯定:制冷系统增设经济器以后,在所测试的工况范围内,其性能明显提高。例如,当t_o=-35℃,t_k=40℃,工质为R717时,制冷量增加24.1％,制冷系数提高19.5％。     

离心式冷水压缩机组成部件的结构分析和技术特性比较

本文介绍了离心式冷水机组的主要组成部件，包括压缩机和电机，蒸发器和冷凝器，节流装置和抽气装置等，比较了不同机型技术特性的优缺点，为选择适合的离心式冷水机组提供了选型依据。     

Performance simulations of twin-screw compressors with economizer

In a compressor refrigeration plant with an economizer system, the regular expansion valve is replaced by two valves and an intermediate pressure vessel. The refrigerant which is vaporized after the first valve is injected via the compressor economizer inlet to a thread under compression. The economizer arrangement increases the refrigeration capacity and improves the coefficient of performance (COP). In this paper a performance simulation computer program for twin-screw compressors with an economizer arrangement is presented. Comparisons of economizer performance for different arrangements are often difficult to carry out if real tests have not been run, as the performance is dependent on the intermediate pressure and this pressure is not the same for different arrangements. Such comparisons can be made with the simulation program. Examples are presented for an economizer arrangement combined with external liquid subcooling and for a two-stage economizer arrangement.     

The energy efficiency of chillers in a trigeneration plant

The cooling requirements of buildings can be met using a variety of cooling systems. Electrically driven compressor chillers are the most popular, however, the last decade has seen a rapid increase in the number of absorption chillers, which can use many different energy sources including exergy-poor sources. As an alternative solution for satisfying the cooling demands of buildings and improving the cogeneration efficiency, steam and hot-water driven absorption chillers can be included in trigeneration plant. In this paper we look at the efficiency of a number of different chillers. A method for the exergetic efficiency determination of different kinds of chillers is described and a comparison of the chillers' exergetic efficiency in a trigeneration system including the whole cooling loop is shown.     

Theoretical and experimental research on the working process of screw refrigeration compressor under superfeed condition

In order to increase the refrigeration capacity and improve the coefficient of performance (COP), an economizer arrangement is used in the refrigeration system with screw refrigeration compressor. In this system, the mid-pressure refrigerant gas from the economizer is injected in the screw refrigeration compressor. So it affects the performance of the compressor. In this paper, the working process of a twin screw refrigeration compressor with economizer under different superfeed pressures is studied. A mathematical model for simulating the working process of screw refrigeration compressor under superfeed condition with the economizer is presented; especially the flow coefficient of superfeed is obtained by the experimental research. To verify the model, the p–V diagrams (pressure–volume diagrams) of screw refrigeration compressor under different superfeed pressures with the economizer are recorded successfully by making use of a micro-type pressure sensor that embedded into the groove at the root of the female rotor on the discharge side. The p–V diagrams of theoretical calculation are in good agreement with the results of experimental recorded, which lead to conclusion that the model can be used as a powerful tool for performance prediction of screw refrigeration compressor, also, it is very helpful for refrigeration system design.     

经济器补气压力对双螺杆制冷压缩机性能影响的试验研究

在制冷系统中使用经济器提高了系统制冷量,但由于中间补气使压缩机耗功增加,制冷系统的COP并不会随制冷量成正比增长,其增长幅度依赖于补气压力、补气孔口位置等参数。通过实测补气工况下双螺杆制冷压缩机的P—V图,分析了不同补气压力下压缩机的热力过程特征,研究了补气压力对双螺杆制冷压缩机性能及COP的影响。研究结果表明：压缩机工作腔内气体压力在开始补气时会大幅上升,随后上升幅度逐渐变缓甚至略有下降,压缩机效率和系统COP随补气压力的上升出现先升后降的趋势,结果,存在一个最佳补气压力使制冷系统的COP增加幅度最大。     

Transient simulation of vapour-compression packaged liquid chillers

This paper presents a transient simulation model that is useful for predicting the dynamic performance of vapour-compression liquid chillers over a wide range of operating conditions. The model employs a thermal capacitance approach for specific state variables to account for the dynamics of the chiller and ancillaries. The model accounts for the change in heat transfer coefficients throughout the heat exchangers thereby improving both physical realism and the accuracy of the simulation model. The model requires only a select few initial conditions (eg. the chilled water and condenser water temperatures). A simple compressor model based on empirical regression has been employed in the simulation. The outputs of the model include system performance variables such as the compressor electrical work input and the coefficient of performance (COP) as well as states of the refrigerant throughout the refrigeration cycle with respect to time. The model is validated with data from two in -situ screw chillers. Predictions are found to be within ±10%, although for one of the chillers a degree of empiricism was employed for the evaporator tube wall mass in order to give satisfactory results for the start-up process.     

变频离心式压缩机冷水机组

高效和节能技术是空调用冷水机组的主要发展方向。本文论述了近年来变频技术在离心式压缩机冷水机组中的应用,包括大型变频离心式压缩机冷水机组和磁悬浮变频离心式压缩机冷水机组。这两种技术是当今世界上离心式压缩机冷水机组领域里最先进的技术。     

Investigation of R-744 Voorhees transcritical heat pump system

Using economizer in R-744 heat pump cycle is an effective way to improve the heating capacity in cold climates. In this paper, a modification construction of reciprocating compressor with economizer port, a Voorhees compressor was introduced and the heat pump cycle with Voorhees economizer was compared with the traditional screw or scroll economizer cycles. Both the R-744 transcritical heat pumps with and without Voorhees economizer were tested at the same conditions with different air mass flow rates and different evaporating temperatures. The results show that the heating capacity of the heat pump with Voorhees economizer can be two times higher than the transcritical heat pump without economizer at low evaporating temperature conditions. At the same capacity operation conditions, the efficiency of the heat pump with Voorhees economizer is higher at high refrigerant mass flow rate conditions. The optimum discharge pressure of the heat pump with Voorhees economizer is found to be higher than the heat pump without economizer at the same ambient conditions. For mobile heat pump application, CO₂ transcritical heat pump with Voorhees economizer demonstrates better performance comparing to the conventional transcritical CO₂ heat pump without economizer when the evaporating temperature is lower than −20 °C, or when the mobile is idling with low compressor RPM.     

水作为制冷剂的透平冷水机组研究现状(二)

水是一种古老的制冷剂,至今仍使用在溴化锂吸收式制冷机中和蒸气喷射式制冷机中,但被认为不适合在蒸气压缩式制冷机中使用。自从科学家们发现CFCs和HCFCs制冷剂对大气臭氧层的破坏作用和产生全球气候变暖效应以后,这些CFCs和HCFCs制冷剂在大型透平冷水机组中将被淘汰使用。在寻求新的替代制冷剂时,水重新引起了人们的关注。本文综述使用水作为制冷剂在大型透平冷水机组中应用的研究和开发现状,包括制冷循环的COP分析,透平压缩机的结构和设计,以及三孔口冷凝波转子系统。