Influence of Condensing Temperature on Heat Pump Efficiency

The thermodynamic aspect of a compression type heat pump （HP） is briefly described and special attention is given to investigation of condensing temperature influence on heat pump efficiency in heating mode, expressed by its coefficient of performance （COP）. Heat pumps are usually applied for the purposes of heating and cooling of energy efficient buildings where they have advantages in low-temperature systems, as it is well documented in the paper. The comparison of real thermodynamic processes with thermodynamically most favorable Camot＇s process is made. The results in the paper show that COP is diminishing with increasing of condensing temperature and also depends on real properties of working fluids. The impact of compressor efficiency for two real working media is also analyzed in the paper. There is significant diminishing of COP with diminishing of compressor efficiency. The intension of the paper is to help better understanding of this very effective and prosperous technology, and to encourage its development, production, and efficient application.

Developing Operational Model for Heat Pumps as Space Heating and Domestic Hot Water Provider

In the United Kingdom, means of meeting domestic heating is being electrified to decarbonise in effort to reduce the greenhouse gases emissions from the burning of natural gas. Therefore, the uptake of heat pumps is on the increase. The operation and working principle of heat pumps must be well understood in the investigations of their impacts on the grid and the grid assets, especially distribution transformers which could be overloaded due to higher peak load demand. This work develops an operational model of heat pumps as combined space heating and domestic hot water provider implemented in MATLAB. The developed operational model of heat pumps is adaptable and repeatable for different input parameters. The developed model is used to generate daily average demand profiles of heat pumps for a typical winter weekday and a typical summer weekday. The generated demand profiles of heat pumps by the developed model compared well with the demand profiles of heat pumps generated from actual field projects which are usually expensive and time-tasking.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

Design and performance test of miniature capillary pumped loop for electronics cooling

Considering two characteristics of compact heat dissipation room and high heat flux, a novel miniature capillary pumped loop (MCPL) for electronics cooling was proposed. MCPL consists of evaporator, condenser, vapor and liquid line dissipates heat by boiling and condensation of working fluids with no extra power consumption. Working fluid circulation is ensured by vapor pressure and capillary head. Saturated wick screens vapor and liquid, and ensures one-way flow of working fluid with no extra valve. In order to promote heat dissipation capacity of MCPL, the intensified boiling and condensation structures are embedded into evaporator and condenser respectively, which are useful to increasing boiling and condensation efficiency. Startup and run characteristics are tested by experiments in the condition of different power inputs and working fluids. MCPL is capable of dissipating 80 W of thermal energy and keeping the bottom substrate temperature of evaporator at 80 ℃.

Transient Exergy Analysis of the Condenser and Evaporator of an Air Source Heat Pump Water Heater

In this study the performance of an ASHPWH （air source heat pump water heater） is assessed from exergy point of view in component wise. In order to investigate the work potential of energy, the destruction on the exergy is analyzed and results are summarized for the components individually. The exergy destruction of the system is studied by considering real paths of the pressure and temperature data which are collected during the experiments of the ASHPWH under varying environmental conditions. In the following step, the evolution of the exergy destruction of the system is calculated by a code which is compiled on MATLAB along these temperature and pressure paths. The obtained results reveal the importance of the transient exergy analysis by providing detailed information about exergy destruction of the system such as where it drives up and reaches up to its max and where it drops down and evolves on a smooth path.

家用空气源热泵热水器微通道冷凝器仿真研究

为提升家用空气源热泵热水器水箱外微通道冷凝器的性能,建立了家用空气源热泵热水器水箱外微通道冷凝器的准稳态模型,实验验证结果显示模型误差能控制在±9%以内。依据模型对微通道冷凝器的换热量、换热系数、压降等性能进行仿真研究。结果发现,微通道冷凝器为四流程时能够减小压降并保证换热量满足需要;关键参数微通道截面的最佳尺寸在1.6~2.6 mm^(2)系统性能最优,同时扁管内微通道数应控制在16~24根。研究结果为家用空气源热泵热水器微通道冷凝器的设计提供借鉴。

采用非共沸制冷剂的双喷气增焓两级压缩热泵循环研究

提出一种采用非共沸制冷剂的双喷气增焓两级压缩热泵循环(DVIC),该循环在普通喷气增焓循环(VIC)的基础上采用分液冷凝技术,并增加一组闪蒸器,减少系统不可逆损失,改善热力性能。采用R290/R1336mzz(Z)非共沸制冷剂,对DVIC进行研究,并与VIC进行比较。结果表明:在设定工况下,DVIC比VIC拥有更优的循环性能,系统COP和(火用)效率分别提高5.82%和8.41%,压缩机功耗降低6.39%;在较低蒸发温度或较高冷凝温度的运行工况下,DVIC性能的改善效果更加明显。

闭式循环热泵烤房的设计及其在安康烟区的烘烤效能研究

针对密集烘烤烤后烟叶欠柔软、香气损失等问题,对闭式循环热泵烤房进行了优化设计。以常规开式循环热泵烤房为对照,研究了其除湿速率、能耗水平及其对烤后烟叶柔软度、常规化学成分和感官质量的影响。结果表明:不同烘烤阶段冷凝水流出速率有较大差异,变黄末期冷凝水流出速率最高,此后逐渐下降。闭式循环热泵烤房干烟烘烤能耗成本较开式循环热泵烤房下降0.51元/kg,烤后烟叶宽度收缩率和柔软度显著优于开式循环热泵烤房。闭式循环热泵烤房烤后烟叶感官质量综合得分高于开式循环热泵烤房,主要体现在改善了烤后烟叶的香气量和余味。

Performance and Optimization of Air Source Heat Pump Water Heater with Cyclic Heating

A new type of microchannel condenser applied in the air source heat pump water heater(ASHPWH)with cyclic heating was proposed in this study.The operating performance of the ASHPWH was frst tested.Then,the structure of the microchannel condenser was optimized with the implement of vortex generators.Finally,a numerical model of the ASHPWH was established and the optimized microchannel condenser was studied.The experimental results showed that the average coefficient of performance(COP)of the 1HP(735 W)ASHPWH reached 3.48.In addition,the optimized microchannel condenser could be matched with a 3 HP(2430W)ASHPWH with an average heating capacity of 10.30 kW,and achieving an average COP of 4.24,14.6%higher than the limit value in the national standard.

建筑负荷率及回水温度对地源热泵效率的影响研究

地源热泵是地热能利用的有效工具,在可持续发展领域作用显著。依托长春市某高校近零能耗建筑中的地源热泵供暖系统,对不同建筑负荷率及在不同的冷凝器(负荷侧)回水温度工况下热泵机组制热效率的变化规律进行研究,旨在优化地源热泵系统在近零能耗建筑中的应用,并使其高效运行。研究表明:随着机组负荷侧设定回水温度的不断升高,机组制热效率不断下降;建筑负荷率在75%时,机组制热效率达到最高;建筑负荷率低于55%时,机组制热效率下降明显。这为严寒地区近零能耗建筑中地源热泵系统的优化运行提供了数据支撑。

“双碳”目标下河北省农村取暖的低碳转型实施路径研究

在“双碳”目标下,农村取暖面临低碳转型。在对河北省农村取暖现状分析的基础上,对“双碳”目标下农村低碳取暖的需求进行了总结。以河北省张家口地区、唐山地区、石家庄地区的农村住宅为例,对在取暖季分别采用传统散煤取暖、天然气取暖、生物质成型燃料取暖、电直热取暖、空气源热泵取暖、“光伏+空气源热泵”取暖6种取暖方式时的需热量、用能量、污染物排放量、取暖费用、初始投资进行了对比分析,并探究了适合河北省农村取暖的低碳转型实施路径。研究结果表明:1)不同取暖方式中,“光伏+空气源热泵”取暖在清洁、低碳、可持续方面的综合表现最优,但其初始投资较高,可采用“政府补贴+银行贷款”的形式进行推广。2)在目前河北省农村地区清洁取暖改造已基本完成的情况下,其取暖的低碳转型实施路径具体为:在气代煤、电代煤未覆盖区域,对剩余使用寿命大于等于20年的房屋建筑,优先推广采用“光伏+空气源热泵”取暖;对老旧房屋建筑,推广采用空气源热泵取暖或生物质成型燃料取暖。在电代煤区域,可发展屋顶分布式光伏发电,以解决电代煤取暖方式取暖费用高、碳排放量高等问题。在气代煤区域,仍保留原燃气输配管道向用户输送燃气用于做饭,然后结合当地经济和社会特征、资源禀赋,推广应用绿色低碳技术和节能设备。在目前现状下,可先推广屋顶分布式光伏发电的应用,再逐步推广采用空气源热泵取暖;然后由天然气取暖和“光伏+空气源热泵”取暖协同应用逐步向单一采用“光伏+空气源热泵”取暖方式发展。

基于制冷剂泄出的双温热泵特性研究

为满足生产生活中双温供暖供热的需求,提出了一种基于制冷剂泄出的双温热泵系统。建立基于制冷剂泄出的涡旋压缩机数理模型和系统模型并进行数值模拟验证,计算分析系统在不同泄出口位置、泄出口大小、蒸发温度、高温冷凝温度、中温冷凝温度下系统各项性能参数的变化趋势,并与传统双温热泵系统进行对比分析。结果表明,压缩机中间泄出口打开越早压缩机耗功越少、泄出口越大系统节能效果越明显,较传统双温热泵系统制热性能系数在不同工况下都有显著提高,最高可提升16%。所提模型为制冷剂泄出式双温热泵、补气增焓热泵系统的理论分析提供了更有效方法,为涡旋压缩机性能优化和双温热泵系统的研究、设计及系统性能的提升提供了理论参考。

一款改进的家用热回收空调热力性能实验研究

为提高家用空调器利用率并节能减排,通过改进得到一款具有制冷、供暖、全天候供热水和冷凝热回收制取热水四种功能的热回收空调器。热力性能实验结果表明,改进后的热回收空调器各模式运行可靠,节能效果显著。

某住宅小区温湿度独立控制空调系统设计

以南京某住宅项目为例,介绍了该项目复合式地源热泵系统、空调水系统、新风系统、空调末端、温湿度及防结露控制。该空调系统采用集中冷热源、分户换热系统,节省了管网投资,降低了输送能耗。用户侧定压补水采用竖向分区减压补水,控制用户侧毛细管系统工作压力,提高了毛细管辐射末端可靠性及使用寿命。置换新风系统采用局部微降板埋地处理,以节省户内空间。其竖向分区的新风系统减小了户内风井面积,增加了使用面积,由双冷源深度热回收新风机组集中回收排风能量,优化了冷凝器配置,热泵回收低温排风能量,提高了内置热泵效率。该项目系统设计对住宅毛细管辐射系统设计具有一定的参考价值。

冷凝热回收技术在区域能源站中的应用研究

本文针对广东某区域能源站需要长期进行供冷和供应生活热水的需求,设计了一种基于冷凝热回收技术的离心式水源热泵蓄热供热系统,该系统通过回收区域能源站夜间进行蓄冰的冰蓄冷双工况主机冷却侧散热量作为水源热泵的热源,制取高温热水进行蓄热供热,实现低品位冷凝热向可再生能源的转化,结合峰谷电价有效降低系统运行费用,并通过全年逐时能耗仿真计算,对比分析了采用空气源热泵供热系统和电热锅炉供热系统的经济性及节能水平。结果表明,冷凝热回收的系统全年能效可达3.75,相对于空气源热泵系统实现节能50.9%,节费72.4%,相对于电热锅炉系统节能77.9%,节费87.6%;冷凝热回收系统的能源成本降低至0.11元/kWh,相对于空气源热泵系统降低72.3%,相对于电热锅炉系统降低87.5%。

采用水冷冷凝器的电动汽车热泵系统制热和抗结霜性能试验研究

热泵技术由于具有比电加热显著提升的制热效率,近年来逐渐应用于电动汽车以期提高冬季续航里程。文章设计了一套电动汽车热泵系统,该系统取消了传统热泵的车外冷凝器,而以低温散热器作为主要的散热和吸热部件。根据实车的零部件部件要求搭建了该热泵系统的测试台架,台架试验结果表明该热泵系统在-7℃环境下,纯热泵工况下的制热能力可以达到5.4kW,COP可以达到2.4。通过模拟电机电控的余热回收效果,试验发现低于30%的余热可以被该系统吸收用于制热。试验也表明这种类型的热泵系统在湿度较高的情况下同样存在结霜的问题,且结霜开始的时间与环境湿度和压缩机转速关系紧密。

火电厂供热技改项目新增用电负荷分析研究

为满足城市供热和响应电网调度需求,各热电联产机组都在加快实施相应的供热技改项目。改造过程中,由于新增工艺设备用电负荷较大,经常遇到厂用电裕量不足的问题。本文通过实际案例,依据厂用电设计规程对设计负荷进行校核,同时对工艺设备实际运行工况进行分析,采用负荷率法重新校核。理论分析和实际运行数据均表明供热技改项目对厂用电负荷的影响较小,多数技改项目无需实施高厂变增容或增设高厂变。

小型燃气吸收式热泵机组研究

随着能源紧缺和环境污染问题的日益突出,寻找高效、环保的能源利用方式成为各行各业共同关注的焦点。热泵技术作为一种能够利用低品位热能实现高品位热能供应的技术,其应用前景备受关注。小型燃气吸收式热泵机组作为一种新型的热泵系统,具有独特的结构和优势,引起了人们广泛的研究兴趣。基于此,本文从机组结构、应用优势、应用场景等角度出发,对小型燃气吸收式热泵机组进行研究,以供参考。

冷凝热回收地源热泵系统运行仿真研究

根据经验模型与样本数据在TRNSYS平台上建立开发了冷凝热回收地源热泵系统仿真模型,以夏热冬冷地区的上海市宾馆建筑为例,利用开发模型研究了冷凝热回收地源热泵系统长期运行的效益。仿真计算结果表明,与传统地源热泵+燃气锅炉系统相比,冷凝热回收地源热泵系统中长期运行能保持土壤温度稳定,土壤温升减少了76%,运行20年一次能源标准煤消耗量减少10%,冷凝热回收改造动态投资回收期为4年,具有更好的稳定运行与环保节能效益。

空气源热泵空调除霜模式瞬态冲击与减振方法研究

某特定型号空气源热泵空调在北方0℃至-20℃低环境温度下运行2至5个制热季后,会出现冷凝器支管泄漏的不良问题,经排查发现冷凝器支管与冷凝器管板接触的位置发生磨损,导致制冷剂泄漏。采用西门子振动测试设备对发生制冷剂泄漏的热泵空调进行振动数据采集,结合有限元分析,发现导致冷凝器支管磨漏的原因是热泵空调除霜工况下四通阀切换时产生的振动冲击,经铜管传递至冷凝器支管,冷凝器支管与冷凝器管板翻遍孔过盈配合处产生相对振动。寒冷冬季情况下,冷凝器结霜速率快,热泵空调频繁进入除霜工况,四通阀频繁切换加速了冷凝器支管的磨损,最终发生泄漏。针对该问题,设计了新的减振胶块,将胶块安装在集气管和冷凝器支管振幅最大的位置,减轻四通阀冲击引起的支管振动,经试验测试,振幅降低50%以上,整改前,一个制热季冷凝器支管泄漏引起的售后为767起,直接损失金额为900500元;次年整改后,一个制热季冷凝器支管泄漏引起的售后为58起,直接损失金额66400元,整改后的售后件数降幅约为92%。