Characteristics of a gravity-assisted heat pipe-based heat exchanger

An experimental study of the performance of an air-to-air thermosyphon-based heat exchanger utilizing R-22 as the working fluid has been carried out to investigate its behavior under different operating conditions. A test installation has been developed to model a variety of HVAC real life applications. The results reported in this article describe the influence of various parameters such as: supply and exhaust air stream mass flow rates, stream temperatures and exhaust stream moisture content on the effectiveness of the heat exchangers. Heat exchanger heat flow hysteresis has been recognized. Some optimization criteria are presented.     

Thermodynamic design data for absorption heat transformers—part III. Operating on water-lithium iodide

Derived thermodynamic design data, including Carnot coefficients of performance, enthalpy-based coefficients of performance with and without an economizer heat exchanger and flow ratios for possible combinations of operating temperatures, are calculated for absorption heat transformers operating on a system in which water is used as the working fluid and aqueous lithium iodide solution as absorbent. The effects of operating temperatures as well as economizer heat exchanger on the performance of the absorption heat transformer are illustrated graphically.     

Thermodynamic design data for absorption heat pump systems operating on water-lithium iodide—part I. Cooling

The operating temperatures in the absorption heat pump system fix the absorber and the generator concentration for a given working pair. Derived thermodynamic design data, including Carnot coefficients of performance and enthalpy-based coefficients of performance, with and without an economizer heat exchanger for possible combinations of operating temperatures, are presented for water-lithium iodide absorption systems for cooling. The effects of operating temperatures as well as economizer heat exchanger on the performance of an absorption cooler are illustrated graphically.     

Thermodynamic design data for absorption heat pump systems operating on water-lithium iodide—part II. Heating

Derived thermodynamic design data, including Carnot coefficients of performance and enthalpy-based coefficients of performance (for heating) with and without an economizer heat exchanger for possible combinations of operating temperatures are calculated for a system in which water is used as a working fluid and aqueous lithium iodide solution as absorbent. The effects of operating temperatures as well as economizer heat exchanger on the performance of an absorption heat pump are illustrated graphically.     

基于热量流法的超临界CO2换热器性能分析

本文基于热量流法,应用进口温差定义的换热器通用热阻,采用分段法考虑超临界CO₂的物性变化,结合能量守恒方程,构建了超临界CO₂-冷却水换热过程的整体热量流拓扑模型,结合超临界CO₂物性库和经验关联式提出了换热器性能分析的流程图,实现了综合考虑物性-结构-运行参数的超临界CO₂-冷却水换热器的性能分析,进一步结合[火积]耗散热阻的概念提出了评价物性变化时换热器换热性能的等效热阻。通过分析获得了换热量的沿程分布规律,发现当进口压力为11 MPa时,总的换热量最大,此时等效热阻最小。总之,热量流法对超临界CO₂为工质的换热器设计和系统分析是可行和有效的。     

Performance of a compact,spiral coil heat exchanger

A spiral coil heat exchanger consists of a number of horizontal layers of spirally wound, finned tubes connected to vertical manifolds at the inner and outermost turns of each coil. This design has advantages in heat recovery and air-conditioning applications. Two theoretical models to predict the performance of this compact heat exchanger are presented based upon unmixed and mixed air-flow considerations. Results of experimental studies on a laboratory model of the spiral coil heat exchanger agree well with the predicted performance of the theoretical models. Charts of effectiveness vs NTU suitable for design are presented.     

地源热泵的运行特性模拟研究

依据圆柱源理论,建立起了耦合地面热泵机组和地下埋管换热器特性的模拟模型,该模型可用于长期运行的地源热泵系统的短时间步长运行特性模拟。探讨了模拟过程中有关参数的确定方法,并运用所建模型对地源热泵的冬季和夏季运行特性进行了模拟。运行特性模拟与实验数据的验证结果表明,所建模型可以对地源热泵的运行特性做出符合实际的预测。     

Feasibility and design studies for heat recovery from a refrigeration system with a canopus heat exchanger

This paper presents an investigation of the feasibility of heat recovery from the condenser of a vapour compression refrigeration (VCR) system through a Canopus heat exchanger (CHE) between the compressor and condenser components. The presence of the CHE makes it possible to recover the superheat of the discharged vapour and utilize it for increasing the temperature of the external fluid (water) removing heat from the condenser. The effects of the operating temperatures in the condenser and evaporator for different inlet water temperatures and mass flow rates on the heat recovery output and its distribution over the condenser and CHE (the fraction of the condenser heat available through the CHE), available outlet water temperature and heat recovery factor have all been studied and optimum operating parameters for feasible heat recovery have been ascertained. The parametric results obtained for different working fluids, such as R-22, R-12, R-717 and R-500, have been presented. It is found that, in general, a heat recovery factor of the order of 2.0 and 40% of condenser heat can be recovered through the Canopus heat exchanger for a typical set of operating conditions.     

U型管地下换热系统非稳态传热数值模拟

地下换热器是地源热泵系统重要的组成部分,单U型管是当前广泛使用的地下换热器形式。本文建立了单U型管地下换热器的真实尺寸三维数值模型,通过模拟结果同试验实测数据的对比,验证了模型的正确性。本文随后对单U型管地下换热器在冬季工况下连续运行和间歇运行的换热率进行了数值计算,得出了换热率随时间变化的规律。本文还对连续运行工况下U型管作用半径随时间变化的规律进行了研究。本文得出的结果可以用来指导地源热泵工程的设计。     

格芯夹层结构散热性能的数值计算评估

为评估格芯夹层结构的传热性能以及代替传统的板式肋片结构应用于汽车散热系统中的可能性,文章对几种典型的格芯夹层结构（如kagome lattice,tetrahedral lattice和pyramidal lattice）和板式肋片（corrugated plate）结构实施了一系列的三维数值计算评估.通过对比相同Reynolds数下的传热系数和相同泵功率下的局部Nusselt数来评估各组结构的传热性能.结果显示,相同Reynolds数条件下,各组格芯夹层结构的传热系数较板式肋片结构均有提高,同时摩擦阻力也大幅度增大.在相同泵功率条件下,由于板式肋片结构所受形阻基本可以忽略,因此在较低泵功率范围内（< 1 500 W）,板式肋片的局部Nusselt数最大.随着泵功率的增长,当泵功率提高到3 000 W,tetrahedral的Nusselt数与板式肋片持平并进一步增大,显示出了格芯夹层结构的应用潜力.高传热性能而低摩擦阻力的格芯夹层结构完全有潜力代替传统的板式肋片结构应用于新型高效紧凑的散热系统中.      

气液双热源耦合换热器性能研究

设计了一种由管翅式换热器和套管式换热器耦合而成的气液双源耦合式换热器,该换热器可以实现一种介质同时与气态热源和液态热源进行同步耦合换热.对该换热器进行了详细的介绍,并对其耦合换热特性及该换热器在耦合热源热泵空调中应用时的制热工况进行了的性能测试.研究结果证明,使用该气液双热源耦合式换热器的耦合热源热泵空调系统,气液双热...     

盘状螺旋管换热器的实验研究

介绍了一种适用于小流量大温升的新型盘状螺旋管换热器,具有结构简单、质轻,体积小的特点;利用相关的实验研究,获得其换热性能和流动阻力特性。实验结果表明,其在小流量下仍具有较高的传热系数,适合于做热泵热水器的水冷换热器。     

翅片管蒸发器换热表面的结霜特性与对其结构设计的影响

通过论述翅片管蒸发器换热表面的结霜特性以及结霜对换热器性能的影响 ,提出了改进结霜工况下翅片管蒸发器结构的一些措施 ,以减小结霜对其换热性能的不利影响 ,延长除霜周期 ,节约能源和原材料。特别是针对蒸发器除霜装置的改进以及不同工作温度范围内翅片管组结构的变化进行了阐述     

Timing compensation for an excimer laser solid-state pulsed powermodule (SSPPM)

For certain applications, it is critical to minimize variations in the (throughput) timing between trigger and the output pulse of a magnetic modulator. A circuit is described that maintains a relatively constant delay over a large operating voltage range (600-1150 V) and temperature range (25 °C-65 °C) range, The circuit operates by sampling the charging voltage and magnetic switch temperature just prior to the start switch trigger. Those parameters are then used to calculate the appropriate amount of delay to add into the low-level trigger chain to ensure that the delay stays constant over the voltage and temperature operating range. Although other approaches can be conceived and implemented, this particular design is relatively simple and inexpensive and meets the desired performance goals. Data presented show that the ideal correction function is nonlinear in nature and, as a result, simple linear approximations are limited in their ability to minimize the timing variations. Improvements to the original circuit use a multiple, piece-wise, linear approach in order to obtain better performance. The results are that an initial timing variation of almost 3 μs has been reduced to a total variation of less than 100 ns     

环路热管技术的研究热点和发展趋势

综述了环路热管技术近20年的主要理论和实验研究内容,分析了当前的研究热点,包括环路热管启动特性研究,以温度滞后和温度波动现象为代表的暂态特性研究,新型毛细芯的研制和毛细结构的优化,蒸发器内的强化传热和可视化研究,以及高级环路热管、混合冷却环路、多蒸发器混合环路热管、低温环路热管等新型环路热管技术。     

换热器动态设计方法研究

本文在分析了换热器动态特性对其运行和性能影响的基础上,提出了换热器的动态设计方法.该方法结合换热器动态特性中大惯性的特点,将设计和运行以及目标参数的控制结合起来,同时引入换热器柔性的特点,使得所涉及的换热器具有最佳的动态运行性能.     

Winter performance of residential heat pump

This paper deals with the effect of a snowcover on the coefficient of performance (COP) of a residential heat pump with a single layer ground heat exchanger for maritime climatic conditions (Fredericton, NB, Canada). A computer program was used to simulate a snowcover and heat and moisture transfer in the ground. Results obtained show that an increased thickness of a snowcover may evoke an increase of the COP of the ground heat pump system. Noticeable changes of the COP are observed within a snow-depth range from 0 to 10 cm. A further increase in snow depth does not significantly improve the COP which hereafter appears to be independent on a depth of a horizontal ground heat exchanger.     

Experimental study on the heat transfer characteristics of a new type flat micro heat pipe heat exchanger with latent heat thermal energy storage

An experimental energy storage system has been designed using a new type flat micro heat pipe heat exchanger that incorporates a moderate-temperature phase change material paraffin with a melting point of 58°C. The basic structure, working principles, and design concept are discussed. The heat transfer process during the charging and discharging of the heat exchanger under various operating conditions has been experimentally investigated. Results show that the performance of the new type flat micro heat pipe was steady and efficient during charging and discharging. The average thermal storage power and absorption efficiency have been determined to be approximately 537 W and 92.5%, respectively.     

Experimental and numerical investigation on the exergy and entransy performance of a novel plate heat exchanger

There has been increased attention on various types of plate heat exchangers because of their high efficiency and compactness. This article presents an investigation of heat transfer and fluid flow performance of a novel plate heat exchanger based on numeric studies and experimental tests. Parameters of the novel plate heat exchanger are analyzed and discussed. The thermo-hydraulic transfer performance of different plate heat exchangers is comprehensively analyzed using the exergy and entransy principle. The results indicate that the novel plate heat exchanger has better thermo-hydraulic transfer performance than the smooth plate heat exchanger. The result of this study provides a paradigm for the optimal design of plate heat exchangers.     

高温相变储能换热器中传热模型的研究

1前言利用相变材料在发生相变时有很高的潜热释放或吸收的特点，将相变材料作为储热介质用于相变储能换热器中，可以大大地提高热储存的容量。本文研究的这种壳管式相变储能换热器壳内布置换热管，管壳之间填充高温储热材料，管内通以空气作为热交换流体提取储存在相变材料中的热量。定义输出功率为单位时间内热交换流体所提取到的热量，那么输出功率就成为评价这类换热器换热性能的指标。2理论模型的建立下面几点，概括了求解本文相变储能装置中传热问题的特点：a．相变储能换热器的壳侧填充的AI-Si合金属高温相变储能材料，实验始末其温…