脉管制冷机回热器填加紫铜丝网的影响

在回热器中加入紫铜丝网增加径向导热有利于抑制大功率脉冲管制冷机回热器中的温度不均现象,但紫铜丝网也可能对制冷机性能产生其它的影响。通过数值模拟考察了在没有温度分布不均时,不同的紫铜丝网目数、分布方式、丝网厚度等对制冷机性能的影响。结果表明,在假设回热器温度均匀的情况下,不论如何填充定量的紫铜丝网,总会引起制冷机的效率降低;如果总的紫铜丝网数量一定并且均匀地分布在回热器中,整机制冷性能不会因填充层数的不同而有明显变化;采用与回热器不锈钢丝网目数接近的紫铜丝网要比目数相差较大的丝网可以获得更好的效果。     

板叠式回热器的特征频率

提出回热器特征频率的概念,以热声器件的热动力学理论为基础,建立起热声回热器的分布参数网络模型,以实例分析并用Matlab编程计算回热器不同工质下的特征频率,得出了单一He气和He、Ar混合气体下回热器的特征频率分别为565 rad/s和1 300 rad/s以及回热器的阻抗特性和不同工作压力对回热器阻抗影响的关系图.通过计算分析以便为回热器与系统更好地匹配,以及为回热器热声转换效率的提高提供依据.     

热声热机核心部件——回热器

回热器是热声热机热声转换的核心部件。介绍了目前常用回热器种类,回顾了国内外对回热器的研究进展,重点介绍了回热器内部的能量流动情况,并对回热器研究今后的发展趋势进行了展望。     

大功率脉管制冷机回热器填料优化研究北大核心CSCD

对一台液氮温区百瓦级制冷量的大功率斯特林型脉管制冷机的回热器填料进行了理论优化和实验研究。实验结果发现,在回热器冷端适当组合不同目数的丝网后,会把回热器分成两个部分,这在一定程度上能抑制大功率脉管制冷机回热器中的二次流动,降低回热器中部的温度非均匀性。通过实验得出该脉管制冷机中回热器填料的最优组合为300目不锈钢丝网搭配250目不锈钢丝网,组合比例为10∶1,最终在80 K获得了381.3 W的制冷量。回热器中部最大温差为30.3 K,相较于在回热器中填充单一300目不锈钢丝网的情况,降低了25.6 K。     

斯特林制冷机回热器热损研究

讨论了回热器的各种损失对斯特林制冷机的影响,对斯特林制冷机回热器的结构和丝网填料进行了分析,并模拟分析各种损失的影响.研究表明,回热器的结构、丝网填料对制冷机的性能有重大影响.     

小型制冷系统中吸气管-毛细管回热器特性实验研究

由吸气管与毛细管热交换形成的回热器对小型制冷装置的制冷性能有着重要影响。目前,回热器主要有以下四种类型:毛细管外穿式、铝箔覆盖式、铜锡焊式、毛细管内穿式。结合理论分析,实验研究了制冷装置采用不同类型回热器时毛细管进出口温度、吸气管进出口温度、蒸发器温度以及压缩机吸排气温度对其工作性能的影响。结果表明,从换热性能上看,毛细管内穿式回热器与铜锡焊式回热器的性能基本相同,从制冷装置总体制冷性能上看,毛细管内穿式回热器优于铜锡焊式,且比毛细管外穿式及铝箔覆盖式回热器同等条件下单位容积制冷量提高17.4%,采用毛细管内穿式回热器有利于提高系统的制冷性能。     

交变流动热机的介观热力循环理论--第一部分 制冷机回热器的介观热力循环模型及分析

提出了交变流动热机的介观热力循环理论,系统地分析交变流动热机中关键部件的热力过程.本部分将基于物理上直观的拉格朗日法,首先分析回热器内具有代表性微团的热力过程,进而阐述回热器整体在整机中的热力工作过程和功能.分析表明,回热器中的不同气体微团及相应的固体工作介质更像一个个配合精巧、工作在不同温度水平、功能完整的微型热机.对于制冷机来说,回热器内的微团通过接力作用,一步步将低温热源的热量向高温泵送,并最终排向环境温度热源.     

热声回热器自激振荡特性的研究

从热动力学理论出发,定量地证明回热器的自激振荡特性为负阻尼振荡。回热器是热机系统的热声源,从外热源吸收热能补偿热机系统的能量耗散,维持系统的热声振荡。对不同的回热器填料进行比较,为回热器的填料选择提供了理论依据。     

吸附剂型回热器热声热机

介绍了回热器热声制冷机理及发展简况,并对回热器填料为金属网格和吸附剂两种材料的热声特性作了对比,给出强化吸附剂型回热器热声特性的方法,并提出吸附剂型回热器热声制冷机更应能广泛适用于低温热源,无运动部件,清洁制冷的建议。     

双声源法调制回热器边界声场的理论分析

为了方便获得热声系统较佳的回热器边界条件,提出了双声源法调制回热器边界声场的方案.基于Rott方程,推导出回热器以及有阻尼谐振管中的声场表达式,建立了回热器边界声场调制的理论模型,得到了回热器边界声场和双声源的声压之间的关系.理论分析表明双声源法可以实现回热器边界声场的任意调节,并实际讨论了各种回热器声场边界条件的调制方法.     

The effect of tapering on a magnetocaloric regenerator bed

To design a high efficiency magnetocaloric heat pump for the residential sector, we focused on the improvement of the performance of the regenerator bed. In particular, placing the regenerators circumferentially on a plane, we decided to use tapered regenerators instead of the straight channel ones. Therefore, this paper investigates the effect of the tapering of the regenerators, which exhibit better air-gap utilization. Several simulations using a 1D AMR model were run to study the performance of the tapered regenerator, and the results were compared to the case of the straight regenerator bed. Moreover, the temperature span was held fixed at 25 K, and the working temperature of the regenerator was shifted to study the sensitivity to the variation of the working conditions. This paper considers a 10-layer regenerator, with Curie temperature (T_C) spacing of 2.5 K.     

新型径轴向混合填充式回热器的流动阻力实验

对新型径轴向混合填充式回热器的流动特性进行了实验研究.实验结果表明:在工质体积流量相同的条件下,新型径轴向混合填充式回热器的稳态流动阻力系数f小于层叠丝网型回热器,而大于丝网卷裹型回热器和平行丝型回热器;在相同体积流量下,以He为工质的稳态流动阻力系数f是以N2为工质时的3.4-3.6倍;回热器稳态流动阻力系数f主要与...     

Flow characteristics of a cyclic flow regenerator

The results of experimental investigations on the cyclic flow characteristic of the regenerator of a split cycle Stirling cryocooler is presented. A mathematical model has been proposed to describe the action of regenerator and other main components of the cryocooler system on its dynamic response.     

Development of parallel wire regenerator for cryocoolers

This paper describes development of a novel regenerator geometry for cryocoolers. Parallel wire type is a wire bundle stacked in parallel with the flow in the housing, which is similar to a conventional parallel plate or tube. Simple and unique fabrication procedure is developed and fully depicted in this paper. Hydrodynamic and thermal experiments are performed to demonstrate the feasibility of the parallel wire regenerator. First, pressure drop characteristic of the parallel wire regenerator is compared to that of the screen mesh regenerator. Experimental result shows that the steady flow friction factor of the parallel wire type is three to five times smaller than that of the screen mesh type. Second, thermal ineffectiveness is determined by measuring the instantaneous pressure, the flow rate and the gas temperature at the warm and cold ends of the regenerator. The measured ineffectiveness of the parallel wire regenerator is larger than that of the screen regenerator due to the excessive axial conduction loss. To alleviate the intrinsic axial conduction loss of the parallel wire regenerator, segmentation is introduced and the experimental results reveal the favorable effect of the segmentation. Entropy generation calculation is adopted to compare the total losses between the screen regenerator and the parallel wire regenerator for various operating ranges. Simulation results show that the parallel wire regenerator can be an attractive candidate to improve cryocooler performance especially for the case of smaller NTU and lower cold-end temperature.     

A new method to calculate the pressure drop loss of the regenerator in VM refrigerator

The VM refrigerator, known as heat driven refrigerator, is one kind of closed-cycle regenerative refrigerator. There are some losses in VM refrigerator, but the losses in regenerator are the main loss when the refrigeration temperature is below 100 K. This paper present one method to calculate the pressure drop loss in the regenerator, which is one main part loss in the regenerator. The pressure drop loss in the regenerator will decrease the refrigeration capacity in two aspects. On the one hand, due to the friction pressure drop in the regenerator will be converted into heat that causes reduced the refrigeration capacity. On the other hand, the pressure drop in the regenerator will decrease the pressure ratio in cold end. From a practical standpoint, this calculation method was used for analysis one VM refrigerator proposed by Zhou in 1984. The results showed that the results by using this method are very close to the experimental results in three temperature points.     

小型斯特林制冷机回热器理论模型与分析

对小型斯特林制冷机回热器建立理论模型,通过对控制方程进行无量纲化处理及合理简化,推导出表征小型斯特林制冷机回热器不可逆性的熵流方程。     

Experimental study on the low temperature regenerator packed with rectification meshes

The low temperature regenerator with rectification meshes was designed to improve the cooling performance of a 10 K G-M refrigerator. The rectification meshes were packed not only at the two ends, but also in two additional positions inside the regenerator. By improving the helium gas distribution inside the regenerator at low temperatures, the cooling performance of the G-M refrigerator was obviously improved. The improvement was influenced by the positions and quantity of the rectification meshes inside the regenerator. The other factors influencing the performance of G-M refrigerator, including the charge pressure and input power, were also tested and their optimum values are given in this paper.     

行波热声发动机中平板与丝网回热器的对比实验研究

制作出了一个平板回热器,将其置入行波热声发动机中与丝网回热器进行对比实验研究.实验结果表明,平板回热器能够有效提高行波热声发动机的输出声功,但是其热效率有所降低.     

Numerical modeling on a reciprocating active magnetic regenerator refrigeration in room temperature

Considering the unignorable factors in practice, a new time independent, 2-dimensional porous media model of room-temperature Active Magnetic Regenerative Refrigeration (AMRR) has been proposed. The 2-D model improved the existing 1-dimensional model by introducing the influence of heat transfer effect though the regenerator wall and conduction for y-axis inside the regenerator. This study compared the previous 1-D model with the 2-D model and concluded that the system can lose 22% of cooling capacity caused by air convection and the conduction loss in y can reach to 10% of cooling capacity. It is concluded that the new model will be useful to predict the performance of room AMRR for more practical conditions.