太阳能跨季节储热供热系统试验分析

介绍了一种太阳能-土壤源热泵联合供热系统,对其运行试验数据进行了分析,并对其运行能效比与两种单独由土壤源热泵供热的模式进行了比较。土壤温度的变化不仅与取热速率有关,还与地温的自动恢复能力相关。该试验建筑所在的土壤条件下地温的恢复能力为30～40MJ/d。采用太阳能-土壤源热泵联合系统能效比最高,土壤源热泵单机组双供系统次之,而土壤源热泵单机组单供系统能效比最低。太阳能跨季节储热及土壤源热泵联合供热系统适用于热负荷远大于冷负荷的建筑。     

基于圆柱源理论模型的U型埋管换热器的模拟研究

分析了圆柱热源(热汇)理论模型,运用圆柱源理论对太阳能-土壤源联合运行热泵系统进行连续20d运行的状况进行模拟,得出联合运行模式较单独土壤源运行模式节能8%~10%,可为圆柱源理论模型应用和太阳能-土壤源热泵运行模式的选择提供参考。引入“负荷集合”思想对圆柱热源(热汇)理论模型进行改进,使其适合于对土壤源热泵的全年运行进行模拟,模拟过程更为快捷。     

地源热泵系统非平衡冷热负荷运行特性研究

建立地埋管传热模型和系统能耗模型,对非平衡冷热负荷条件下地源热泵系统运行特性进行模拟计算。当建筑空调冷负荷大于热负荷,且供冷时间较长时,地源热泵系统从冬季初始运行,到达夏季时段,地温比夏季初始运行低,更加有利于夏季地源热泵系统节能。地源热泵系统运行7a后,采取夏季和冬季初始运行两种方案的地埋管钻孔壁年平均温度与土壤初始温度相比,分别上升3.10和5.12℃,导致机组耗功率逐年增加,应考虑采用复合式地源热泵系统间歇运行或增设地埋管设置分区运行策略,平衡土壤传热量。     

圆柱源理论用于地下U型盘管换热器的模拟研究

分析介绍了引入“负荷聚合”方法的改进型圆柱热源(热汇)理论模型，并运用圆柱源理论对太阳能一土壤源联合运行热泵系统全天运行模拟，指出联合运行模式较单独土壤源运行模式节能10％～12％，为圆柱源理论模型应用和太阳能-土壤源热泵运行模式的选择提供参考。     

地源热泵与主动式冷梁高效复合系统在学校建筑中的应用与设计

本文中的工程采用可再生能源--土壤源地源热泵作为空调冷热源。根据岩土热响应报告、全年能耗分析及地源热泵方案经济性分析,确定了地源热泵配置方案及室外的埋管形式及数量,并配置冷却塔辅助散热以维持土壤热平衡。空调末端(教室及办公房)采用主动式冷梁+新风系统。地源热泵系统分设高温和低温供水系统。18/21℃高温冷冻水供给主动式冷梁承担室内显热冷负荷,有效提高了地源热泵机组的能效比;(新风)空调机组利用低温供水(7/14℃)有效进行冷冻除湿,实现了室内温湿度独立控制。主动式冷梁和地源热泵系统复合系统在舒适度、节能和环保等多方面展现出了优势。     

别墅型建筑地源热泵空调系统设计

地源热泵是一种利用土壤所储藏的太阳能资源作为冷热源进行能量转换的供暖制冷空调系统,通过输入少量的高品位能源(如电力、机械功、燃气和液体燃料),实现热量从低温热源向高温热源的转移.以上海某小型别墅为对象,设计了一套家用地源热泵空调系统.首先计算了夏季冷负荷和冬季热负荷,然后根据冷、热负荷选择一套水源热泵机组(MWH080CR型机组)和相应的风机盘管,进行了室内水管环路系统、土壤热交换器和地板采暖的设计选型,最后对系统的能效比进行了计算.结果表明,该空调系统具有节能环保、稳定可靠、舒适耐用等优点.     

地源热泵-太阳能复合系统与冰蓄冷空调技术联合运行的可行性研究

沈阳某实际工程夏季为冰蓄冷空调技术与传统空调的联合,冬季由城市热网进行供暖。通过De ST-c软件对之进行全年逐时冷热负荷模拟,针对负荷的特性,分析使用地源热泵-太阳能复合系统与冰蓄冷技术联合运行的可行性,并从运行策略和经济性分别进行比较,认为地源热泵-太阳能复合系统与冰蓄冷技术联合运行系统在可行性和经济性方面都具有显著的优势,是一种很好联合运行的模式。     

太阳能、蓄热与地源热泵组合系统能量分析与实验

在天津地区设计建成太阳能、蓄热与地源热泵组合系统(SGCHPSS),实现建筑物供暖、空调、供热水三联供。对组合系统运行模式进行研究,在TRNSYS平台上模拟得到太阳能、地表能的组合、匹配利用关系,及两种热源对整个系统的能量贡献;模拟得到4～7月份太阳能向地下土壤的跨季节蓄热量。进行示范工程实验,得到土壤跨季节蓄热与地源热泵系统全年运行情况,并进行全年土壤热平衡与系统能耗分析。     

复合地源热泵系统冬季供暖运行实验研究

介绍了地源热泵在冬季运行供暖的实验研究,具体分析了长期连续运行时土壤温度的变化规律,热泵机组系统的COP变化情况,以及太阳能辅助系统与地源热泵系统联合运行时土壤温度的变化规律,热泵机组系统的COP变化情况.试验数据表明了增加太阳能辅助地源热泵系统后,显著地提高了冷凝器出口温度和室内温度,有效地提高了热负荷,增加了供热面积.总结出了本地区地源热泵系统的一般运行规律.     

太阳能应用于土壤源热泵低温热源侧的实验研究

为了提升热泵机组的性能系数COP,合理利用不同温度层次的太阳能集热量,文章基于太阳能—土壤源复合热泵系统的大量实验结果,分析了蒸发器进口温度对热泵系统各项性能的影响,并在此基础上,分析了复合源热泵工况和太阳能热泵工况的运行特点。分析结果表明:随着蒸发器进口温度的升高,热泵机组吸热量逐渐增大,热泵机组输入功率略有增加,导致热泵机组的供热量和COP均逐渐增大;复合源热泵工况下,存在土壤源和太阳能共同供热,以及土壤短期储热与太阳能单独供热同时进行的两种运行情况;为了提升热泵机组的工作性能,在太阳能集热量较低时,优先运行复合源热泵工况;土壤源温度的自然恢复能力较差,需要利用太阳能集热系统对土壤源进行跨季强制蓄热,以提高土壤源温度,缓解土壤源冷堆积现象。     

A review of the applications of heat pipe heat exchangers for heat recovery

The waste heat recovery by heat pipes is accepted as an excellent way of saving energy and preventing global warming. This paper is a literature review of the application of heat pipes heat exchangers for the heat recovery that is focused on the energy saving and the enhanced effectiveness of the conventional heat pipe (CHP), two-phase closed thermosyphon (TPCT) and oscillating heat pipe (OHP) heat exchangers. The relevant papers were allocated into three main categories, and the experimental studies were summarized. These research papers were analyzed to support future works. Finally, the parameters of effectiveness of the CHP, TPCT and OHP heat exchangers were described. This review article provides additional information for the design of heat pipe heat exchangers with optimum conditions in the heat recovery system.     

Internal heat generation in a discrete heat source: Conjugate heat transfer analysis

In the present work, we conduct an asymptotic and numerical analysis for the cooling process of a discrete heat source, which is placed in a rectangular-channel laminar cooling flow. In our physical model, the heated strip is embedded in a substrate, generating continuously a uniform volumetric heat rate. We assume that this heat-generation mechanism is due to an electrical current in the heat source. Hence, heat losses to the cooling fluid and to the substrate material during this process are presented. The governing equations of the cooling flow and the participating solid are reduced to an integro-differential equation that predicts the temperature variations of the heat source. We show that the conjugate heat transfer process is controlled by a conjugate nondimensional parameter, here denoted by α, which determines the basic heat transfer regimes between the cooling flow and the discrete heat source.     

Waste heat recovery using heat pipe heat exchanger for heating automobile using exhaust gas

The feasibility of using heat pipe heat exchangers for heating applying automotive exhaust gas is studied and the calculation method is developed. Practical heat pipe heat exchanger is set up for heating HS663, a large bus. Simple experiments are carried out to examine the performance of the heat exchanger. It is shown that the experimental results, which indicate the benefit of exhaust gas heating, are in good agreement with numerical results.     

地源热泵的套管式地下换热器传热研究

地源热泵是一种节能、对环境无害的绿色空调设备,可成为下个世纪冷暖技术的核心,采用能量平衡,建立了地下浅埋套管式换热器传热平衡式,进行求解,并分析了影响传热的各关联因子,提出了需研究的强化地下换热的措施,根据求解结果,给出了相应的函数关系图。对实验设计和工程实践有一定的指导作用。     

一种新颖简易的太阳能热动力转换装置--明托热机

明托热机(Minto Engine),俗称明托转轮,它 是通过液体活塞在转轮中不停地变换位置,产生不 同的动力矩,从而驱动转轮旋转的机器。明托热机 最早于1975年被维利·明托(Wally Minto)发明。 早期的明托热机结构十分简单,效率也很低,但由 于它能将低品位热能转变成高品位的动力。因而一 下子吸引了许多科学家的注意。之后,许多学者对 明托热机进行了研究,提出了许多改进的方向和应 用领域,推动了明托热机的发展。     

Forced convection heat transfer in microchannel heat sinks

This paper presents an analysis of forced convection heat transfer in microchannel heat sinks for electronic system cooling. In view of the small dimensions of the microstructures, the microchannel is modeled as a fluid-saturated porous medium. Numerical solutions are obtained based on the Forchheimer–Brinkman-extended Darcy equation for the fluid flow and the two-equation model for heat transfer between the solid and fluid phases. The velocity field in the microchannel is first solved by a finite-difference scheme, and then the energy equations governing the solid and fluid phases are solved simultaneously for the temperature distributions. Also, analytical expressions for the velocity and temperature profiles are presented for a simpler flow model, i.e., the Brinkman-extended Darcy model. This work attempts to perform a systematic study on the effects of major parameters on the flow and heat transfer characteristics of forced convection in the microchannel heat sink. The governing parameters of engineering importance include the channel aspect ratio (α_s), inertial force parameter (Γ), porosity (ε), and the effective thermal conductivity ratio (k_r). The velocity profiles of the fluid in the microchannel, the temperature distributions of the solid and fluid phases, and the overall Nusselt number are illustrated for various values of the problem parameters. It is found that the fluid inertia force alters noticeably the dimensionless velocity distribution and the fluid temperature distribution, while the solid temperature distribution is almost insensitive to the fluid inertia. Moreover, the overall Nusselt number increases with increasing the values of α_s and ε, while it decreases with increasing k_r.     

Frosting of heat pump with heat recovery facility

This paper aims to prolong the heat pump frost time and reduce its growth with heat recovery facility, which should mix the exhausted indoor and outdoor air before entering the evaporator. An ideal mathematic model is developed for heat transfer, frost generation and airside pressure drop. The properties of the mixture would be obtained by solving the mass and energy conservation equations. A parametric analysis is performed to investigate the effects of air inlet temperature, relative humidity and air mass flow rate on total heat transfer coefficient, frost thickness and airside pressure drop, respectively. The results show that rationalizing the ratio of indoor and outdoor air could prolong frosting time and reduce the frost thickness greatly. The total heat transfer coefficient, frost thickness and airside pressure drop increase monotonically with time going, but are not proportional. Decreasing the mixture inlet air temperature and relative humidity could essentially reduce frost growth on the tube surfaces. This can also be observed when increasing the air mass flow rate.     

石墨烯-PFA复合材料换热器与金属换热器的传热性能对比

氟塑料换热器以其耐腐蚀、耐磨损等优点而备受关注,但氟塑料热导率较低,换热能力差,限制了其广泛应用。石墨烯-PFA复合材料兼具石墨烯优异的导热性和可熔性聚四氟乙烯(PFA)良好的耐酸碱腐蚀性,是新一代的换热器材料。搭建了余热回收测试实验台,对石墨烯-PFA复合材料换热器和金属换热器的传热性能进行对比。研究了不同烟气流速、不同进口烟气温度以及不同石墨烯配比对复合材料传热性能的影响。结果表明:对于金属换热器和复合材料换热器,当烟气流速从2.0增加到4.0 m/s时,传热系数分别增加到原来的1.19和1.34倍;随着进口烟温的升高,两种材质的传热系数分别降低了15.6%和14.7%;随着石墨烯含量增加,复合材料的导热系数以及传热系数均增加。