低冰点溶液在风冷多联机上的除霜应用特性研究

结合西安地区风冷多联机在冬季工况下的温湿度状况,总结已有多联机空调系统的除霜方式的特点和不足,提出一种利用喷淋低冰点溶液进行多联机空调系统除霜及其延缓除霜的方式。通过试验发现利用喷淋低冰点溶液进行除霜的效果良好,并可以延缓下一阶段的结霜过程。     

多联机空调器智能除霜控制研究

本文对多联机空调系统内部冷媒管路进行改进,并划分多个智能除霜区间,实验研究在除霜过程中,该方式对除霜时间和除霜效果的影响。结果表明,这有利于提高多联机空调系统的利用效率,减少能源浪费,增加低温制热的热舒适性。     

风冷多联机在西安地区的除霜应用研究

通过现场抽样调查西安地区多联机冬季除霜现状,得出西安地区现有多联机系统冬季运行结霜特点,并提出两种判断结霜除霜控制的理论,为合理使用多联机提供参考。     

采用相变蓄热模块多联式空调（热泵）系统除霜过程的试验研究

空调采用传统除霜方法对系统性能带来不利影响。本文通过试验研究采用相变蓄热模块的多联式空调（热泵）系统除霜过程的动态特性,并与常规的逆循环除霜方法进行对比。试验结果表明：在除霜、大湿度除霜和低温制热3种工况下,蓄热除霜的制热量比常规除霜时略高,整机的消耗功率基本相同,室内换热器的制热周期基本一致,但除霜期间室内机停机时间缩短一半;蓄热除霜除霜期间室内换热器盘管温度比常规逆循环除霜高20-25℃,蓄热除霜除霜期间室内换热器出风口温度比常规逆循环除霜高13-17℃,大大提高室内环境的舒适性。这表明相变蓄热除霜空调（热泵）系统除霜性能优于传统逆循环除霜空调（热泵）系统。     

房间空调器并行分流热气除霜方式设计与研究

针对现有热泵型房间空调器逆循环除霜与常规热气除霜方式的不足,提出一种新型热气除霜方式——并行分流热气除霜。针对并行分流热气除霜与常规热气除霜进行室外换热器温度分布仿真分析和试验验证。结果表明:常规热气除霜时室外换热器内外排盘管的除霜热量分布不均匀导致换热器外排盘管除霜快、内排盘管除霜慢,而并行分流热气除霜方式可以更好地分配换热器内外排盘管的除霜热量,换热器内外排盘管除霜的同步性更好;在同一试验条件下并行分流热气除霜比常规热气除霜的除霜时间缩短25%。     

寒冷地区多联机的设计与开发

设计并开发寒冷地区多联机产品,产品最大容量可达85 kW(30 hp)。制热工况下产品具备4种运行模式。产品通过压缩机喷液设计和热气旁通除霜模式大幅提升低温制热能力和热舒适特性,实现室外最低-15℃时制热能力无衰减。试验结果显示,热气旁通除霜模式的平均额定能力比率比逆循环除霜模式的提升8.17%,前者的除霜时间仅为逆循环除霜模式的68.28%。     

复叠式空气源热泵蓄能除霜与常规除霜特性实验研究

针对复叠式空气源热泵在冬季寒冷地区供热运行中遇到的结霜和除霜问题,本文提出增设蓄热器的蓄能复叠式空气源热泵除霜系统,通过实验研究了该系统间断制热蓄能除霜及不间断制热蓄能除霜两种除霜模式下的除霜特性,并与常规复叠式空气源热泵采用的低温级热气旁通除霜方式进行对比分析。结果表明:采用蓄能除霜方法的除霜时间较旁通除霜减少71.4%~77.6%,系统除霜能耗降低65.1%~85.2%,机组除霜运行更稳定、可靠。     

空气源热泵两种新型高效除霜控制方法的实测研究

本文针对空气源热泵在制热运行所面临的误除霜问题,介绍了基于直接测量的光-电转换(TEPS)和基于间接测量的温度-湿度-时间(THT)两种新型除霜控制方法。通过现场测试,验证了两种新型除霜控制方法的准确性和高效性。研究结果表明,TEPS和THT除霜控制方法均能实现按需除霜,相比于常规的温度-时间(TT)除霜控制方法能有效避免误除霜事故,使机组平均COP分别提升达到10%和12%。TEPS和THT除霜控制方法具有替代常规除霜控制方法的潜力和应用前景,可在空气源热泵的实际应用中积极推广。     

基于气象参数联动控制技术的多联机研究

分析采用气象参数联动控制技术对多联机节能性与舒适性的影响。研究结果表明:在待机阶段,利用未来天气的变化趋势,调整压缩机电加热带的开启时间与开启时长,能够确保压缩机启动可靠性,同时降低电加热带功耗;在制热运行阶段,根据气象参数,分别引入湿度结霜修正因子和风力除霜修正因子,调整机组能力输出,延长连续制热时间,缩短除霜时间,提高制热舒适性。     

基于辐射和对流换热新型供暖末端的空气源热泵除霜性能试验研究

常规空气源热泵在低温环境中运行时普遍存在结霜和除霜现象,由于常规室内盘管储能不足,导致逆循环除霜效果不理想。同时,基于强制对流换热的常规空气源热泵常常会引起室内热分层现象和强烈的吹风感,导致人体热舒适性较差。为解决上述问题,本文结合辐射供暖具有较高热舒适性的优点,提出一种基于辐射和强制对流换热的新型供暖末端,搭建空气源热泵辐射和对流换热性能试验台,对其除霜性能进行试验研究。结果表明:除霜周期内,该系统压缩机功率平均值为429.5 W,除霜能效比为2.88,除霜能效比高于常规空气源热泵系统。     

Defrosting performances of a multi-split air source heat pump with phase change thermal storage

Recently, multi-split air source heat pumps (ASHPs) have been used increasingly for space heating in cold winter. When it operates in frosting environment, periodic defrosting is necessary to maintain a high system performance. However, researches on its defrosting were few due to its high capital and complicated controls. To solve its fundamental problem of insufficient heat available during defrosting, a novel reverse-cycle defrosting (NRCD) method based on the phase change thermal storage has been developed. In this paper, comparative experiments using both standard reverse-cycle defrosting (SRCD) method and NRCD method were carried out on a multi-split ASHP unit with a phase change material heat exchanger (PCM-HE) acting as energy accumulator during heating operation and heat source during defrosting operation. Experimental results suggested that when using the NRCD method, the system performances, such as suction pressure and temperature, defrosting and heat-resumption durations, COP during defrosting operation can be effectively improved.     

Experiment investigation of reverse cycle defrosting methods on air source heat pump with TXV as the throttle regulator

Reverse-cycle defrosting technique is one of the simplest and most widely used defrosting methods for air source heat pumps (ASHP). However, there are still some problems if thermal expansive valve (TXV) is used as throttle regulator in the unit: the defrosting process might last so long that users would feel uncomfortable due to the fluctuation of the indoor temperature: the system cannot resume heating mode smoothly after the defrosting process, the system often breaks down due to the triggering of low-pressure switch. In this paper the authors proposed that these two problems can be greatly relieved if there is a by-pass solenoid valve in the system which can by-pass the TXV used in the defrosting mode, and best performance can be addressed if the by-pass valve is energized during the whole defrosting process.     

空气源热泵结霜机理及除霜/抑霜技术研究进展

结霜导致蒸发器的热阻增加,传热系数降低,系统COP减小,制约了空气源热泵的推广应用。本文在表面结霜机理研究现状的基础上,总结了影响结霜的各种因素相应除霜/抑霜技术,综述了逆循环、热气旁通和电加热三种常用除霜方法的研究进展,概括了改变空气参数、表面温度和换热器结构的抑霜效果,以及表面改性抑霜技术的研究现状。指出霜导热系数模型的局限性及除霜/抑霜技术存在的问题,提出今后应结合多种措施着重探索对水蒸气凝结、冷凝水冻结、霜层回融和塌陷等阶段均有较强抑制作用的抑霜技术。     

几种空气源热泵除霜方式的性能比较

针对空气源热泵除霜问题,分别对逆循环除霜系统、热气旁通除霜系统和相变蓄能除霜系统进行对比实验,并对三种除霜方式的除霜时间、除霜时压缩机排气压力、室内温度波动等特性进行比较分析。实验结果表明,相变蓄能系统除霜时的压缩机排气温度比另外两种系统高,使得冷凝温度升高,更有利于缩短除霜时间,且室内温度相对稳定,系统能耗也随之减少。     

恒温恒湿系统最佳除霜时刻控制的研究

针对于恒温恒湿系统的除霜最佳时刻的研究,本文提出了在户外温湿度恒定,室内温湿度变化状况下,当蒸发器表面上所结的霜的面积达到蒸发器总换热面积的75%时,利用此时的冷凝压力与蒸发压力的比值作为对机组除霜指令发出的基准.经实验的验证此方法还是可行的,能够运用于实际的工业恒温恒湿机组的最佳除霜时刻控制.     

A novel defrosting control method based on the degree of refrigerant superheat for air source heat pumps

When an air source heat pump (ASHP) unit operates for space heating at a frosting environment, periodic defrosting is necessary to maintain a high system performance. To defrost efficiently, it is necessary to find an effective defrosting control method. In this paper, an experiment was carried out on an ASHP unit with a capillary tube as a throttle device, under simulated frosting and defrosting conditions using time control defrosting method, and the experimental results are firstly presented. Secondly, a novel defrosting control method based on the degree of refrigerant superheat (DS) is reported. To validate the novel defrosting control method, a further experiment was conducted on another ASHP unit with an electronic expansion valve (EEV) as a throttle device, under simulated frosting and defrosting conditions. The experimental results demonstrated that when applying the novel defrosting control method, defrosting was initiated before the operating performances of ASHP unit rapidly deteriorated, which was more reasonable.     

变频空调器低温制热不停机脉冲除霜的试验研究

为提高变频空调器的低温制热量和APF值,设计一套试验方案,在机组制热运行不停机的情况下,利用室内换热器输出的液态制冷剂的余热对室外换热器进行脉冲除霜,有效延长机组的除霜周期,从而提高低温制热量和APF值。从实际试验数据可知,本方案能使变频空调器的除霜周期延长至原来的3倍,低温制热量提高15%,APF值提高0.08,制热效果与舒适性明显改善。     

空调器除霜技术研究

通过对室内机盘管温度变化特性的研究,获得了一种仅通过检测室内盘管温度的变化,来准确的进行室外机除霜的技术。     

低温条件下压缩机油位控制的实验研究

在低温条件下,为了保证直流变频多练空调的正常启动和运行,压缩机油池内的油位控制是非常重要的.压缩机启动控制对比实验研究结果表明,在启动阶段,延长回油平台时长以及增加回油循环和除霜循环有利于油位保持在安全油位之上.单台室内机开机启动时,相应的电子膨胀阀开度必须在350步以上,才能确保机组正常启动成功及油位安全.