Performance analysis of heat pump based on a new solar air-source heat pump heating system

To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and performance of the heat pump part of this new heating system are studied.Based on a SASHP with 10 kW,the mathematical model of this system is built,and the characteristics and performance are concluded from the simulation analysis at different environmental temperatures and output water temperatures.The results show that the performance of heat pumps can be greatly improved based on the new SASHP.When the environmental temperature is 7 ℃,the coefficient of performance（COP）of the air-source heat pump（ASHP）can be increased by 26% at most.This paper sets up a base for further study on the heating system with this new SASHP in the heating season.

Research on Performance of Ground-Source Heat Pump Double U Underground Pipe Heat Exchange

This paper uses FLUENT software building the three-dimensional unsteady state model of ground source heat pump single U and double U underground pipe to study on heat exchange of underground pipe system in the condition of unsteady state long-term continuous running, analyzes the change of soil temperature filed around underground pipe and performance of underground pipe heat exchange between single U and double U pipe system. The results show that double U pipe system is better than single U system, which can improve unit depth heat exchange efficiency, reduce the number of wells and reduce the initial investment.

Novel Radiation-Adjustable Heating Terminal Based on Flat Heat Pipe Combined with Air Source Heat Pump

The electrification of building heating is an effective way to meet the global carbon target. As a clean and sustainable electrified heating technology, air-source heat pumps (ASHPs) are widely used in areas lacking central heating. However, as a major component of space heating, heating terminals might not fit well with ASHP in order to achieve both intermittency and comfort. Therefore, this study proposes a novel radiation-adjustable heating terminal combined with an ASHP to achieve electrification, intermittency, and better thermal comfort. Radiant terminals currently suffer from three major problems: limited maximum heating capacity, inability to freely adapt, and difficulty with combining them with ASHPs. These problems were solved by improving the structural design of the novel terminal (Improvement A–E). Results showed that the maximum heating capacity increased by 23.6% and radiation heat transfer ratio from 10.1% to 30.9% was provided for users with the novel terminal. Further, new flat heat pipe (FHP) design improved stability (compressor oil return), intermittency (refrigerant thermal inertia), and safety (refrigerant leakage risk) by reducing the length of exposed refrigerant pipes. Furthermore, a new phased operation strategy was proposed for the novel terminal, and the adjustability of the terminal was improved. The results can be used as reference information for decarbonizing buildings by electrifying heating terminals.

Analysis of Power Quality Problems in Large-Scale Application of Air-Source Heat Pump

With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial for the environment and alleviates air pollution.However,the large-scale application of airsource heat pumps has brought power quality problems such as voltage sags,harmonic pollution,and three-phase imbalance to the distribution network.This paper studies the fixed-frequency and variablefrequency air-source heat pump,introduces its working principle,analyzes the mechanism of its power quality problem.Moreover,the paper establishes a simulation model for the fixed-frequency heat pump and variable-frequency heat pump to connect to the distribution network.This research mainly studies the impact of large-scale fixed-frequency heat pumps on the depth of voltage sags in the distribution network and the impact of large-scale variable-frequency heat pumps on the harmonic content of the distribution network under different penetration rates and uses measured data to verify the reliability of the simulation results.This paper uses experimental data for the first time to verify the real power quality problems of large-scale heat pumps,which can provide a reference for determining the power quality standards for heat pumps connected to the power grid.At the same time,it can also provide a reference for the power quality management of the distribution network that is actually connected to electric heating.

Refrigerant Control Strategies for Residential Air-Conditioning and Heat-Pump System

This paper simulated the optimal refrigerant charge inventory of a refrigeration system in air-conditioning operation and heat-pump operation respectively,and studied the refrigerant control strategies in this system.The void fraction in two-phase fluid region was calculated by Harms model.And based on distributed parameter model and Harms model,the refrigerant charge inventory in condenser and evaporator were calculated and analyzed in air-conditioning conditions and heat-pump conditions,respectively.The calculating results of different refrigerant mass between refrigeration and heating conditions indicate that the optimal refrigerant charge inventory in heat-pump conditions is lower than that in air-conditioning conditions.To avoid the decrease of COP due to the surplus refrigerant in heating conditions,we introduced the liquid reservoir control method and associate capillary control method.Both of them could increase the heating capacity of the air-source heat pump.The difference of optimal refrigerant charge inventory in air-conditioning and heat-pump system can be controlled by the liquid reservoir or the associate capillary.

The noise spectral characteristics and noise reduction schemes of screw air-source heat pump:A case study

The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in this research.The measurements revealed that the compressor is the main noise source of the heat pump,and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions,with multiple peaks at 63,250,and 1000 Hz.Then,a compressor sound insulation cover with broadband absorption was proposed,and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA.Third,we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation.The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump.The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ALa exhibit a U-shaped relation.For buildings of different heights,the optimal heights of noise barrier are proposed.The 5.5-meter is the optimal height of the sound barrier for single-story buildings.The conclusions can be applied to other building projects for heat pump noise reduction.

地铁车站围护结构耦合埋管换热系统运行策略研究

以某地铁车站为研究对象,模拟了其全年动态负荷,确定了地源热泵参数,建立了估算热泵出力及耗电量的参数模型,结合建立的动态换热模型得到了地源热泵系统-埋管阻容耦合仿真模型。以10年为运行周期,计算了埋管出水温度和换热量,分析了不同工况下的换热性能,提出了热泵机组联合冷却塔辅助换热的运行策略。结果显示:围护结构耦合埋管换热系统在长期运行工况下存在机组停机或机组出力不足的情况,当负荷为计算负荷的80%时,可以保证热泵机组出力满足需求;冷却塔联合运行策略在制冷季可以有效降低埋管出水温度,在过渡季冷却塔的免费冷量可以降低埋管出水温度1~2℃,在长期运行工况下具有较好的地温恢复效果。

磁场作用下功能性导热流体在地源热泵中的应用研究

本文主要通过对功能性导热流体的研究,找到适合于地源热泵中使用的功能性导热流体,优化携热、阻垢、腐蚀问题,强化传热工质导热能力,进一步找到该功能性导热流体在地源热泵中应用的优选方案。主导产品为功能性供暖导热流体与新型优化地埋管。与其他功能性流体相比,实验项目所采用的功能性流体具有制作简单的特点,并且极为环保,更适合大面积的应用。综合比较下Fe3O4-H2O纳米流体为地埋管循环流体最佳选择。

某产业园混合式装配能源站的应用

以某产业园混合式装配能源站为例,介绍地埋管换热器设计、能源站配置、BIM模型建立、现场装配、系统调适及运行测试,分析系统设计、运行中的实际问题,总结地埋管地源热泵系统设计、装配、调适和运行中的一些经验方法,为混合式装配能源站的应用提供参考。

Experimental study on heat exchange of several types of exchangers

Aiming at the ground-coupled source heat pump that possesses the shortcomings of occupying larger land,this article studies the heat exchanged of heat exchanger in piling,and compares it with common heat exchangers buried directly. The result indicates that the heat exchanger makes the best use of structure of building,saves land,reduces the construction cost,and the heat exchanged is obviously more than exchangers buried directly. In winter condition,when W-shape pipe heat exchanger in pile foundation is 50 m deep and diameter is 800 mm,it transfers 1.2-1.3 times as large as the one of single U-shape buried directly at the flow rate of 0.6 m/s,whose borehole diameter is 300 mm. And in summer condition it does about 2.0-2.3 times as that of U-shape one.

基于PIPENET对集中供热管网能耗的研究

建筑能耗节能的重点是供热能耗,传统集中供热管网采用阀门节流,虽然消除了冷热不均现象,但这是以能源浪费为代价的,可见集中供热管网的节能措施显得尤为迫切。通过建立动力分布式定速加压泵供热管网的计算模型,对以不同环路选取主循环泵的供热管网进行了能耗模拟计算,计算结果表明:在动力分布式定速加压泵供热管网中,选择主循环泵的环路逐渐靠近热源,供热管网的能耗逐渐降低;选择主循环泵的环路逐渐靠近热源,供热管网的节能率开始保持稳定增长,当选择主循环泵所在的环路离热源足够近时,供热管网的节能率开始趋于稳定。

中深层地埋管热泵供热系统运行特性实测研究

通过大量工程实测研究,总结了中深层地埋管热泵供热技术的运行特性。中深层地埋管具有出水温度高、取热功率大、长期运行稳定的特点,为热泵系统提供了高品位的低温热源,以提升其运行性能;同时中深层地埋管自身存在间歇蓄热特性,能很好地满足建筑供热需求变化与柔性用能;无级变频热泵机组更适合与中深层地埋管匹配运行,节能减排效果显著;热源侧水系统具有小流量、大扬程,且阻力随着流量变化而大幅度变化的特性。研究结果可为提升该技术的供热性能提供关键指导。

基于改进粒子群算法的中深层地源热泵供暖系统运行优化

构建变工况运行且包含蓄热装置的中深层地源热泵供暖系统,基于改进粒子群算法,分别以运行费用、系统COP和地热能利用系数为目标函数对系统运行进行优化,并对优化结果进行比较和分析。结果表明:对应目标函数优化后的运行费用、系统COP和地热能利用系数分别为279.27元、6.4420和0.8527。以系统COP为目标函数的优化效果与运行费用相反,而与地热能利用系数相近。

大型地埋管群地源热泵三维传热-渗流耦合模拟

为确定地下水渗流对大尺度、多分支埋管集群地源热泵系统换热区温度场和换热特性的影响,基于上海天文馆880个地埋管地源热泵场地,建立考虑地下水渗流和地质分层的三维传热-渗流耦合模型,并利用现场热响应试验对模型进行验证。结果表明:渗流作用引起管群内和支管群之间沿地下水流动方向发生温度干扰,89.5~120.3 m埋深范围内的温度干扰现象相对明显;地下水渗流有利于提高管群的换热总量,缩小夏季和冬季工况的换热量差距;换热量增加百分比随水力梯度的增加而增大,两者呈对数函数关系,当水力梯度大于0.005时,换热量增加百分比趋于平稳。

地埋管换热系统改造项目关键技术节点施工工艺研究

天津某管业公司建筑原采用常压燃气热水锅炉供热和分体式空调供冷,现拟以浅层地热能为基础能源对原供热制冷系统进行改造,施工前首先通过现场岩土热响应试验、地下管线探测等查明施工场地岩土体结构和换热能力,掌握地下综合管线的分布,并对建筑单位冷热负荷指标校正。重点阐述地埋管换热系统施工过程的关键技术节点,即竖直换热孔钻进、下管、回填及水平管线连接等,为类似改造项目提供参考。

竖进平出型地埋管群换热器结构与控制优化

【目的】为提高浅层地热能利用效率,亟须对影响地源热泵系统性能的地埋管换热器结构和控制开展优化设计。【方法】建立了一种竖进平出型地埋管群换热器模型,研究其换热系统性能,探究其最佳结构及运行方式。【结果】管群布置横纵比越低,单位面积换热量越大,横纵比超过0.15后对系统影响较小;换热器间距越小,土壤利用率越高,但热短路损失越大;双列双出型埋管每延米换热量相较于双列单出型结构提升7%以上;负荷较大工况下叉排布置结构的换热效果更好;整个夏季优化结构的平均出口温度下降2.28℃,换热器周围土壤温度下降1℃以上;实际运行过程中应优先考虑采用流速随负荷变化控制模式。【结论】研究结果可为地源热泵换热器的设计、制造提供理论依据。

电磁-机电暂态混合仿真在多能源系统动态建模中的应用研究

热力网络是多能源系统的重要组成部分。电网和热网建模机理和时间尺度存在较大差异,传统电力系统暂态仿真程序难以直接应用于电-热多能源系统动态仿真。根据电-热类比方法,采用基本电气元件构建了热力管道热路和水路等效电路模型。同时,基于查表法构建了计及设备运行特性的空气源热泵等效电路模型。为提高仿真效率,进一步提出了基于电磁-机电暂态建模框架的电-热多能源系统动态仿真方法。电网采用机电暂态建模,热网采用电磁暂态建模,空气源热泵模型作为接口模型,完成电网模型和热网模型之间的数据交互。电网模型与热网模型均采用毫秒级及以上仿真步长,实现了高效的多能源系统动态仿真。最后通过算例分析验证了所提模型和仿真方法的有效性。

超长重力热管联合热泵的地热利用系统热力经济性分析

深层地热资源储量巨大,采用超长重力热管取热技术对深层地热资源进行开采,将其与热泵系统联合为用户供热是一种高效利用深层地热资源的方法。针对如何调节不同参数下超长重力热管与热泵联合运行以期获得最佳热力经济性的问题,建立了系统热力经济性模型,研究了热泵系统蒸发温度、超长重力热管热阻、井深、地温梯度以及蒸发器面积不同的情况下系统热力经济性变化规律。结果表明存在一个最佳蒸发温度使供热成本最低,如在地温梯度30℃/km、井深3 000 m的条件下,最佳蒸发温度为-2℃;超长重力热管热阻越小或地温梯度越大时可实现供热成本越低且最佳蒸发温度越高;存在最佳的井深和蒸发器面积使得供热成本最低。研究结果可为优化超长重力热管在开采深层地热联合热泵系统性能方面提供理论指导。

土壤源热泵地埋管侧水系统优化运行研究

本文基于江苏无锡某典型厂房土壤源热泵空调项目的实测数据,以地源侧系统总能耗最低为目标,构建设备模型对地源水泵运行工况进行优化,并与两种传统控制策略的运行效果进行对比,据此提出进一步的优化建议。结果表明:基于负荷的优化控制策略,其节能效果要明显优于定频控制策略,冬夏季典型测试日平均节能率分别为28.33%和13.27%,相比于5℃温差变频策略节能了3.61%和2.21%。适当增大地埋管的埋管深度或管径,可以进一步提升该优化控制策略的节能效果。传统的定温差控制策略在负荷率大于60%时,可在5℃基础上将温差增加1~5℃以提升节能效果。

中小型数据中心冷却系统优化案例研究进展

针对数据中心行业节能环保的要求,通过对业界主流节能空调技术在数据中心改造方面的应用探究,提出了现有中小型数据中心冷却系统节能改造的路径。研究表明:氟泵热管蒸发冷凝技术、蒸发冷却技术、液冷技术、泵驱动两相机柜背板、数据中心升温节能技术、风冷冷却系统改为水冷冷却系统等技术方案在中小型数据中心节能改造方面具有良好的应用,针对不同情况选用不同技术措施可以有效降低数据中心能源使用效率。