Development and Experimental Study of Air Source Heat Pump Water Heater

The principle and development prospect of air source heat pump water heat were introduced,as well as the designation of condenser (storage water tank),experimental study on installations was also carried out.The results showed that air source heat pump water heater was superior to conventional system.Under the operation of cooling and heating,heat pump comprehensive utilization equipment could improve heating performance,reduce energy consumption,and recycle condensing heat to provide hot water.

Operating performance of novel reverse-cycle defrosting method based on thermal energy storage for air source heat pump

To solve the fundamental problem of insufficient heat available during defrosting while ensuring the efficient and safe system operation for air-source heat pumps (ASHPs). A novel reverse-cycle defrosting (NRCD) method based on thermal energy storage to eliminate frost off the outdoor coil surface was developed. Comparative experiments using both the stand reverse cycle defrosting (SRCD) method and the NRCD method were carried out on an experimental ASHP unit with a nominal 2.5 kW heating capacity. The results indicate that during defrosting operation, using the NRCD method improves discharge and suction pressures by 0.24 MPa and 0.19 MPa, respectively, shortens defrosting duration by 60%, and reduces the defrosting energy consumption by 48.1% in the experimental environment, compared with those by the use of SRCD method. Therefore, using the NRCD method can shorten the defrosting duration, improve the indoor thermal comfort, and reduce the defrosting energy consumption in defrosting.

Operation Performance of Air Source Heat Pump System for Space Heating in Tianjin

An air source heat pump system (ASHPS) used in an office building is set up and studied experimentally. Its operating performance in winter is evaluated based on test data and a comparative discussion is given on the effect of climate conditions and heating load ratio on the operation behavior. Then heating capacity variation caused by evaporator frosting is analyzed as well. Finally, the defrosting parameters and the technical feasibility are studied for a constant heating demand. The experimental results indicate that both the outlet water temperature drop and the system COP should be taken into account when setting defrosting parameters, and ASHPS is a viable technology for space heating and hot-water production in winter in Tianjin, which can maintain the room temperature above 19 ℃ when the outdoor temperature is -2 ℃.

Modeling and Optimization of Solar Collector Design for the Improvement of Solar-Air Source Heat Pump Building Heating System

To enhance system stability,solar collectors have been integrated with air-source heat pumps.This integration facilitates the concurrent utilization of solar and air as energy sources for the system,leading to an improvement in the system’s heat generation coefficient,overall efficiency,and stability.In this study,we focus on a residential building located in Lhasa as the target for heating purposes.Initially,we simulate and analyze a solar-air source heat pump combined heating system.Subsequently,while ensuring the system meets user requirements,we examine the influence of solar collector installation angles and collector area on the performance of the solar-air source heat pump dual heating system.Through this analysis,we determine the optimal installation angle and collector area to optimize system performance.

Research on Operation Optimization of Heating System Based on Electric Storage Coupled Solar Energy and Air Source Heat Pump

For heating systems based on electricity storage coupled with solar energy and an air source heat pump(ECSA),choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency.In this paper,four cities in three climatic regions in China were selected,namely Nanjing in the hot summer and cold winter region,Tianjin in the cold region,Shenyang and Harbin in the severe cold winter region.The levelized cost of heat(LCOH)was used as the economic evaluation index,and the energy consumption and emissions of different pollutants were analyzed.TRNSYS software was used to simulate and analyze the system performance.The Hooke-Jeeves optimization algorithm and GenOpt software were used to optimize the system parameters.The results showed that ECSA systemhad an excellent operation effect in cold region and hot summer and cold winter region.Compared with ECS system,the systemenergy consumption,and the emission of different pollutants of ECSA system can be reduced by a maximum of 1.37 times.In cold region,the initial investment in an air source heat pump is higher due to the lower ambient temperature,resulting in an increase in the LOCH value of ECSA system.After the LOCH value of ECSA system in each region was optimized,the heating cost of the system was reduced,but also resulted in an increase in energy consumption and the emission of different pollutant gases.

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.

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.

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.

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。

光伏、光热与空气源热泵热水系统碳减排特性仿真与实测

我国生活热水供热品质、使用量逐步提升,其能耗在建筑节能发展过程中占比突显。为比较太阳能热利用、光伏电加热及空气源热泵热水系统的碳减排特性,本文建立了各类系统的性能化设计模型,并会同国家级检测中心开展了实测验证,分析了系统碳减排特性与室外环境温度、太阳辐照资源及运行控制策略的相关性。结果表明:严寒、寒冷地区低温环境显著影响太阳能集热保温和空气源热泵蒸发工况,在Ⅱ类太阳能资源区太阳能热水系统碳减排贡献更大;夏热冬冷、夏热冬暖地区空气源热泵性能最优,Ⅱ、Ⅲ类太阳能资源区受归一化温差影响,太阳能热利用时长和稳定性不及光伏电加热热水系统;光伏电加热热水系统受光伏组件效率影响,能源利用率不及太阳能热水系统,但通过增加光伏装机容量获得的节能收益提升最为显著。

空气源热泵与市政热力双热源供暖系统设计与运行分析

介绍了北京市某项目的供暖节能改造,从减少投资成本、降低后期维护费用、缩短投资回收期及应对极端天气的角度,因地制宜地选择了低温空气源热泵与市政热力双热源运行方案。改造完成后,通过1个供暖季的运行,与传统市政蒸汽供暖系统相比,双热源供暖系统能源消耗总量减少了49.4%、供暖费用减少了650084.23元,充分验证了双热源供暖方案的节能减排效果,为供暖节能改造提供了新思路。

基于深度强化学习的空气源热泵供热系统温度控制策略

空气源热泵(air source heat pump,ASHP)负荷具备良好的可调节特性,其建模的准确性和控制策略的设计是充分发挥其调节潜力的关键。文中考虑空气源热泵供热系统的储热特性,提出了基于深度强化学习(reinforcement learning,RL)的空气源热泵供热系统温度控制策略。首先建立了基于参数辨识的空气源热泵供热系统数学模型。其次建立了空气源热泵供热系统马尔可夫过程决策模型,并基于Q-Learning算法设计了供热系统深度强化学习控制策略。基于实际运行数据的仿真结果表明,本文提出的考虑供热延迟的供热系统数学模型能够准确预测供回水温度及室内温度变化情况,且所提出的基于深度强化学习的温度控制策略能够在维持用户室内温度在设定值的前提下,有效降低用电成本。

高校食堂空气源热水系统的应用

以南通市某高校食堂项目为例,结合高校食堂的热水用水特点,对高校食堂热水热源、热水定额、冷水温度等各参数对高校食堂热水系统的影响进行探讨,并给出合理的取值建议。

Heating performance of a ground source heat pump system installed in a school building

The heating performance of a water-to-refrigerant type ground source heat pump system is represented in this paper under the actual working conditions of the GSHP(ground source heat pump) system during the winter season of 2008.Ten heat pump equipments with the capacity of 10 HP each and a closed vertical typed-ground heat exchanger with 24 boreholes of 175 m in depth were constructed.We investigated a variety of working conditions,including the outdoor temperature,the ground temperature,and the water temperature of inlet and outlet of the ground heat exchanger in order to examine the heating performance of the GSHP system.Subsequently,the heating capacity and the input power were investigated to determine the heating performance of the GSHP system.The average heating coefficient of performance(COP) of the heat pump was noted to be 5.1 at partial load of 47%,while the overall system COP was found to be 4.2.Also,performance of the GSHP system was compared with that of air source heat pump.

Evaluation of non-azeotropic mixtures containing HFOs as potential refrigerants in refrigeration and high-temperature heat pump systems

With the increasing environmental concern on global warming, hydrofluoro-olefin (HFOs), possessing low GWP, has attracted great attention of many researchers recently. In this study, non-azeotropic mixtures composed of HFOs (HFO-1234yf, HFO-1234ze(z), HFO-1234ze(e) and HFO-1234zf) are developed to substitute for HFC-134a and CFC-114 in air-conditioning and high-temperature heat pump systems, respectively. The cycle performances were evaluated by an improved theoretical cy-cle evaluation methodology. The results showed that all the mixtures proposed herein were favorable refrigerants with excel-lent thermodynamic cycle performances. M1A presented lower discharge temperature and pressure ratio and higher COPc than that of HFC-134a. The volumetric cooling capacity was similar to HFC-134a. It can be served as a good environmentally friendly alternative to replace HFC-134a. M3H delivered similar discharge temperature as CFC-114 did. And the COPh was 3% higher. It exhibits excellent cycle performance in high-temperature heat pump and is a promising refrigerant to substitute for CFC-114. And the gliding temperature differences enable them to exhibit better coefficient of performance by matching the sink/source temperature in practice. Because the toxicity, flammability and other properties are not investigated in detail, ex-tensive toxicity and flammability testing needs to be conducted before they are used in a particular application.

Thermal Efficiency Optimization of a Ground Source Heat Pump System by Assistant Preheating/Precooling: A Case Study on a Heating-Load Dominated Building

Operation strategies of Ground Source Heat Pump System(GSHPS) such as continuous or intermittent approaches have been extensively studied. In this work, a novel strategy was proposed to maximize the energy efficiency of GSHPS. In this approach, the buildings was first air-conditioned by the preheating/precooling mode and the rest thermal load was covered by the heat pump(HP) mode. The system performance can then be optimized by considering the combination of these two operating modes. A case study was made to examine the thermal performance of a GSHPS installed in Nuremberg, Germany. Thermal performance of the HP and the preheating/precooling operating modes was examined. The system was optimized by deploying the assistant preheating/precooling approach and over one-year period monitoring showed that the seasonal Coefficient of Performance(COP) of the GSHPS was 4.12 in winter and 5.01 in summer. These COP values are higher than that of the conventional GSHPS. Thus, this proposed strategy could be an efficient way to improve the thermal performance of GSHPS.

太阳能-空气源热泵牧草干燥系统制热性能研究

以太阳能-空气源热泵牧草干燥系统为研究对象,通过系统不同工作模式的温升、恒温制热试验及带载试验,分析了温升速率、单位温升能耗、COP及除湿效率。研究结果表明:联合制热模式与太阳能单独制热相比,单位温升耗电量降低了86.2%,温升速率提高了99~112倍。联合制热模式与热泵单独制热试验相比,在温升过程中温升速率降低了7.7%~17.6%,单位温升耗电量降低8.0%;在恒温制热过程中,前者COP比后者提高了6.5%~11.1%,耗电量降低了5.8%~10.7%;在升温制热过程中前者COP比后者提高了6.0%~10.4%,耗电量降低了6.6%~11.1%。联合干燥模式比热泵单独干燥模式的SMER值高19.8%~36.2%。

基于ANFIS的太阳能-空气源热泵供暖系统温度控制研究

针对太阳能-空气源热泵供暖系统运行环境复杂多变,模糊控制器的设计高度依赖人工经验的问题,提出一种基于自适应神经模糊推理系统(ANFIS)改进的模糊控制方法。该方法利用ANFIS在复杂系统建模中的优势,结合供暖系统温度响应特性和实际运行数据,建立联合供暖系统变工况ANFIS模型,生成与系统性能适配的模糊规则库并传递给模糊控制器执行。Matlab/Simulink仿真对比试验表明,与单一的模糊控制相比,该方法的控制精度提高了17.65%,调节时间缩短了36.4%,具有更高的控制精度和响应速度。

光伏光热联合双源热泵系统运行模式研究(1):最佳切换模式验证

讨论了光伏光热联合双源热泵系统制热运行的最佳切换模式。利用TRNSYS软件建立了仿真模型,对双源(水源、空气源)热泵系统性能系数(COP_(s))进行了计算,提出以某时刻空气源热泵模式或水源热泵模式运行COP_(s)较大者优先运行作为COP_(s)切换模式。通过前期实验结果验证了模拟结果的正确性,并与常规的集热水箱温度切换模式进行了对比实验,验证了COP_(s)切换模式的有效性。结果表明,该实验系统以COP_(s)最佳切换模式运行时发电量和发电效率较集热水箱温度切换模式分别提高了5.35%和1.73%,耗电量降低了17.03%,COP_(s)提高了4.91%。