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.

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.

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.

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.

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.

基于梯级利用的工业园区综合能源系统双层优化

目前中国仍有部分工业园区采用供电、供热、供气等各种能源供应系统单独规划和运行的方式,导致大量工业余热被浪费,系统能效低、碳排放高。为了充分利用工业余热并提高系统运行能效,提出一种含高温蒸汽热泵(high temperature heat pump,HTHP)的工业园区综合能源系统(integrated energy system,IES)双层优化模型。首先,构建含HTHP的工业园区综合能源系统架构。其次,针对IES能效较低的问题,利用余热的梯级利用原则与多能协同原则,建立含HTHP的综合能源系统调度策略。再次,建立包含设备容量规划优化与运行优化的双层优化模型,并提出优化模型的求解方法。最后,通过西北地区一个化工园区的实例分析,验证了所提方法的有效性。

R32/R134a自复叠热泵变组分浓度实验分析

为缓解热泵大温度跨度运行时容积制热量衰减严重的问题,提出一种新型变组分浓度调控自复叠热泵实验装置,采用非共沸混合制冷剂R32/R134a为工作介质,通过动态监测系统组分浓度分布、制热量、性能系数(COP)等关键性能参数,探究混合工质浓度变化对自复叠热泵循环性能的影响规律。结果表明:冷凝器出水温度或第一级节流阀开度增加,主路低沸点组分质量分数降低2.5%~8.1%。而随着充注量增加,主路低沸点组分质量分数逐渐增加,排气温度逐渐降低;当充注量增至2.8 kg,出水温度为65℃时,COP达2.22,压缩机排气温度仅为80℃。当低沸点组分质量分数从0.3增加至0.5,排气温度最高可降低25.4%。与单级蒸气压缩系统(SVC)相比,自复叠热泵系统排气温度降低31.2%,以上自复叠热泵组分浓度分布及性能变化规律表明该热泵系统在大温度跨度时具有较明显的性能优势,对于系统长期稳定运行以及节能效应具有显著作用。

炼化企业能量利用优化案例分析

基于炼化企业生产用能规律及特点,借助流程模拟、对标、大数据分析等方法,中海石油宁波大榭石化有限公司开展了全厂能量利用优化研究,在装置工艺过程、换热网络、低温热合理利用、蒸汽梯级能量利用等方面提出了改进措施和优化方案,并实施了提高DCC装置原料直供比及分馏塔塔顶循环换热流程优化、乙苯装置低温余热回收利用、甲苯塔进料换热网络设计优化、抽提蒸馏装置蒸汽喷射泵技术应用等节能优化改造,每年产生经济效益约5727万元,实现节能36 ktCE(1 tCE=29.3 GJ),减少CO_(2)排放103 kt,全厂低温热利用率提高了16.3%。

地热供暖梯级利用优化研究

提高地热能利用率是地热供暖节能增效的有效途径,尾水回灌是热储可持续开发利用的根本保障。不同的地热能供暖运行策略致使系统地热能利用率与系统总能效不同。不同的热储层具有不同的物化特征,为利于回灌、节能及安全,宜据其特性优化利用模式。基于砂岩热储供暖在不同运行模式下案例,定量分析不同侧重点之优缺,提供更合理的梯级利用策略参考模型。

Thermodynamics of Cascaded Waste Heat Utilization from Flue Gas and Circulating Cooling Water

A detailed thermal power plant model was developed to evaluate power plant waste heat usage in terms of the operating parameters,energy consumption,water consumption,and pollutant emissions.This model was used to analyze the bypass flue gas energy cascade utilization design which provides excellent energy savings and emission reductions.This paper then presents a design to use the low-temperature waste heat and to extract water from the flue gas.The low-grade heat can be recovered from a coal-fired unit using absorption heat pumps to increase the air preheating.This method significantly reduces the turbine steam extraction in the low pressure stages which increases the turbine power and reduces the coal consumption.This design has a small heat transfer temperature difference between the air preheater and the air warmer,resulting in a smaller exergy loss.The power output of the present design was 1024.28 MW with a coal consumption savings of 3.69 g·(kWh)^(−1).In addition,the present design extracts moisture out of the flue gas to produce 46.48 t·h^(−1)of water.The main goal of this work is to provide a theoretical analysis for studying complex thermal power plant systems and various energy conservation and CO_(2)reduction options for conventional power plants.

空气源热泵系统在寒冷地区供暖的应用

寒冷地区某自来水厂项目,供暖分为4个区域,每个区域独立供暖。1~3区供暖设备采用CO_(2)复叠空气源热泵,4区采用传统空气源热泵。文章从方案选择、运行数据的分析得出结论:经过2个供暖期的实际运行表明,CO_(2)复叠空气源热泵供暖系统,供水温度65℃,适合在寒冷地区,末端采用散热器的供暖系统;传统空气源热泵供暖系统,供水温度45℃,适合在寒冷地区,末端采用地板辐射的供暖系统。以上两种空气源热泵供暖系统,运行效果可靠稳定,既减少了冬季供暖的运行费用,又能够减少碳排放。

Research trend of cascade heat pumps

Most commercial and industrial facilities require very low temperatures for refrigeration and high temperatures for space heating and hot water purposes. Single stage heat pumps have not been able to meet these temperature demands and have been characterized by low capacities and coefficient of performance(COP). Cascade heat pump has been developed to overcome the weaknesses of single stage heat pumps. This study reviews recent works done by researchers on cascade heat pumps for refrigeration, heating and hot water generation. Selection of suitable refrigerants to meet the pressure and temperature demands of each stage of the cascade heat pump has been discussed. Optimization of design parameters such as intermediate temperature(low stage condensing and high stage evaporating temperatures), and temperature difference in the cascade heat exchanger for optimum performance of the cascade heat pump has been reviewed. It was found that optimising each design parameter of the cascade heat pump is necessary for maximum system performance and this may improve the exergetic efficiency, especially of cascade refrigeration systems, by about 30.88%. Cascade heat pumps have wider range of application especially for artificial snow production, in the supermarkets,for natural gas liquefaction, in drying clothes and food and as heat recovery system. The performance of cascade heat pumps can be improved by 19% when coupled with other renewable energy sources for various real time applications. Also, there is the need for much research on refrigerant charge amount of cascade heat pumps, refrigerant-refrigerant heat exchangers to be used as cascade heat exchanger, cascade heat pumps for simultaneous cooling, heating and hot water generation and on the use of variable speed compressors and their control strategies in matching system capacity especially at part load conditions.

Feasibility Study of R134a/R404a Cascade Heat Pump Cycle in Heat Pump Dryers with Electrical Heaters at Low Temperatures

Heat pump cycles have been widely applied to dryers for their high efficiency. However, low–efficiency electrical heaters are often used during early drying stage for frozen foods or winter since a standard heat pump cycle cannot operate at low temperature. This study introduced cascade heat pumps replacing electrical heaters to improve dryer performance at low temperatures. Experiments were performed to examine changes in performance of the cascade heat pump dryers in relation to ambient temperature, low-stage cycle mass flow rate, and high-stage cycle mass flow rate. The results showed a significant improvement in low-temperature dryer performance with the introduction of cascade heat pump cycles.

基于烟气余热回收的热泵供热系统热力学分析

为降低供热耗能,采用热泵回收烟气余热,可有效提高机组供热效率。以某300 MW亚临界CFB锅炉机组为例,分别在脱硫塔前后设置低温省煤器和烟气冷凝器,组成新型热泵供热系统,并建立该热泵回收烟气余热热力学模型,分析其烟气余热利用方式对热泵的热力学及供热性能的影响。计算结果表明,布置低温省煤器,设计工况下,热泵性能系数(COP)为1.746时,烟温由130℃降至90℃,可回收最大烟气余热20.87 MW,降低脱硫塔耗水量28.792 t/h;布置烟气冷凝器,可作为热泵低温热源,同时可回收烟气余热10.10 MW,回收冷凝水13.654 t/h。当热网回水温度升高时,COP降低,但热泵系统和供热系统的㶲效率均升高;当冷凝器出口水温升高时,COP和供热系统㶲效率降低,但热泵系统㶲效率升高。回收烟气余热的热泵供热方式,可有效利用烟气低阶能量且具有良好的节能节水收益。

松辽盆地北部地温场特征及地热能开发利用方向探讨

探讨了松辽盆地中低地温场的形成机制,莫霍面隆起、上地幔上隆及壳内高导层的存在是地温梯度及大地热流值高的深部原因。分析了地温场分布特征,地温梯度高值区主要集中分布在兰西—肇东—肇州—肇源以南和哈尔滨—双城以北地区,最大值位于哈尔滨与肇源之间,达到5.4℃/100m,在林甸、泰康以南、齐齐哈尔以西、肇源西北处也发育局部高值区。以嫩江组一、二段泥岩、青一段泥岩和泉二段泥岩作为隔水层,划分为上、中、下三套热储层体系,中部热储层埋藏较深、地层温度较高、砂岩发育,是重点热储层。从纯地热水和油田采出水两方面探讨了开发利用地热资源的方式,认为利用纯地热水资源投资巨大,而开发利用油田采出水热能投资少,见效快,技术及经济风险相对较低,是现阶段热能利用的主要方向。

中深层浅层耦合地源热泵系统供热性能实测分析

针对中深层浅层耦合地源热泵系统,本文介绍了其在不同热负荷规律下梯级利用的系统运行模式。对某项目耦合系统进行了整个冬季的连续监测,得到了其实际供热情况。分析结果表明,中深层井比浅层井的取热温度高53℃、取热量大5.6倍。梯级利用模式的中深层地热取热量较无梯级利用模式增大了1倍。中深层地热供热量中的30%来自于一级换热、70%来自于热泵二级换热。结果表明了中深层浅层耦合地源热泵系统能源梯级利用的占比及优势。

计及含蒸汽热泵工业园区能量品位转换的综合能源优化调度

沿海工业园区具有大量蒸汽需求,且存在能源利用率低及风电浪费严重的问题。为此,以位于中国江苏省靠近海上风电并网点的某沿海工业园区为研究对象,提出一种考虑高温蒸汽热泵能量品位转换的综合能源系统优化调度方法。首先,构建高温蒸汽热泵能量品位转换模型,以实现电热耦合及能源梯级利用;然后,提出含高温蒸汽热泵的风电消纳策略,以促进系统风电消纳;最后,考虑风电出力预测误差,建立以总运行成本最小为目标函数的综合能源系统随机优化调度模型。仿真结果表明,所提调度方法有效促进了海上风电消纳,可在解耦冷热电联产(CCHP)机组“以热定电”运行约束的同时满足工业园区的蒸汽负荷需求。同时,提升了能源利用效率,具有良好的社会经济效益,可有效保障系统运行的可靠性。

变工况下热泵供热及膨胀机供热的热力性能对比分析

通过对各设备进行建模,以某300 MW热电联产机组为例,对热泵供热及利用小型膨胀机发电后排汽供热两种方案进行变工况分析。结果表明,对于热泵供热方案,在不同的主蒸汽流量下,都存在一个最佳出口热网水温,使系统煤耗最低;采用热泵最佳参数与膨胀机方案进行变工况对比,发现在采暖抽汽参数较低时,热泵方案的煤耗高于膨胀机方案,随着采暖抽汽参数的增大,当热泵出口最佳热网水温超过70℃时,热泵方案的煤耗开始低于膨胀机方案;同样,在采暖抽汽参数较低时,热泵供热效率比膨胀机方案低,当热泵出口最佳热网水温超过64℃时,热泵方案供热效率开始超过膨胀机方案;提出等效节能量指标,并通过计算表明该指标可用于对比两方案的节能效益。

夏热冬冷地区新型高温空气源热泵实验研究

为满足空气源热泵冬季集中供热的需求,该文采用新型工质将空气源热泵的制热温度提高至90℃以上。首先建立高温空气源热泵的数学模型并对该系统进行理论计算,进而搭建高温空气源热泵试验台,分别在环境温度为0、5、10℃时对模拟结果进行实验验证,当热水进口温度为80℃时,系统实际COP分别较理论结果低5.9%、5.3%和1.7%。该空气源热泵相比现有技术提升制热温度40℃以上,因此具有较好的市场应用前景和推广意义。

空气源复叠式热泵系统性能的模拟分析

本文采用模拟分析的方法,研究了R404a/R134a高温输出空气源复叠式热泵的性能特征,结果表明热泵在输出温度为90℃、环境温度为0~35℃时,性能系数(COP)从2.14上升到3.04;当环境温度为20℃时、输出温度为80~100℃时,COP从2.94降低到2.23。本文进一步分析了云南昆明真实空气温度波动下复叠式热泵的全天运行性能,结果表明,在变耦合温度调控下热泵的平均COP可达到2.53,兼顾适应性和高效率,也证明了空气源复叠压缩式热泵在高温输出工况下的良好可行性。