家用热泵空调器室外机换热器的流路优化

针对家用热泵空调器用的9.52 mm和7 mm双排室外换热器,在额定制冷制热工况下,利用仿真分析的方法研究流路数对换热器性能的影响,对9.52 mm换热器的流路的进一步优化,得到制冷制热综合性能更优的流路布置方式,并在整机上进行试验验证。结果表明,制冷剂侧压降对冷凝器和蒸发器的换热都有较大影响,特别是对较小管径的换热器;由于蒸发器中制冷剂侧压降较大,热泵空调器室外机用的换热器作冷凝器时对应的最佳流路数少于作蒸发器时的;适当增加过冷管数会进一步提高热泵空调器室外机换热器的综合换热能力;试验结果与仿真结果趋势大致相同。     

全铝钎焊式平行流冷凝器性能对比试验

对6种全铝钎焊式平行流冷凝器进行冷凝换热性能对比试验,与双排9.52mm翅片管换热器进行对比,得到风阻、冷凝能力和综合冷凝能力对比试验曲线。对比结果表明：全铝钎焊式平行流冷凝器具有较高的综合冷凝性能和单位体积换热量,部分规格的平行流冷凝器的单位迎风面积的冷凝能力高于对比用翅片管换热器。     

微通道换热器和翅片管式换热器性能对比试验研究

采用一种用于比较不同换热器传热性能的测试方法和数据分析方法,对比分析一款风冷涡旋式冷水机组使用的微通道换热器和9.52 mm管翅片管式换热器的传热性能差异。分别在25.0℃,35.0℃和43.3℃环境温度下,当压缩机的运行频率在12~50 Hz范围内变化时,对换热器性能进行测试,评估换热器的传热性能差异和整机性能差异。测试数据表明,当修正的冷凝传热温差相同时,在25.0℃,35.0℃和43.3℃环境温度工况下,微通道换热器的冷凝传热量比翅片管式换热器分别高约8.6%~11.3%,13.5%~28.6%和16.4%~36.6%。微通道换热器相比翅片管式换热器在冷凝传热性能方面具有一定优势。     

5mm管径铜管换热器在商用空调机组上的应用研究

基于一台15 kW的商用空调机组,原机的室内、外换热器均采用9.52 mm管径铜管,对其进行替代设计,采用5 mm管径铜管室内、外换热器。在对5 mm管径换热器的优化过程中发现:翅片间距、翅片片型、流路设计、分液器毛细管长度均对换热量、能效、除霜效果有较大的影响。对比优化后的5 mm管径换热器和原机换热器的性能、成本、制冷剂充注量发现:5 mm管径换热器的额定制冷能力提高3.47%,能效比提高7.86%,额定制热能力和性能系数与原机相当,除霜周期较原机增加25.1 min;室外换热器成本降低约10%;室内换热器成本降低约20%;制冷剂充注量减少46%。     

铜管管径对翅片管式冷凝器性能和经济性的影响

针对大型风冷式制冷机组的应用,分析铜管管径变化时翅片管式换热器换热面积、管侧容积、换热量和压降变化情况,并进行材料成本和单位换热量材料成本的比较。研究结果表明,在合理选择管列间距和管排间距的前提下,7.94 mm和7 mm的换热器都可以达到9.52 mm换热器的换热量,并实现约10%的成本节约。     

片宽对两排翅片管式换热器性能的影响

基于传统片宽的φ7 mm两排翅片管式换热器,针对片宽对换热器性能的影响进行数值模拟和试验验证,数值模拟结果表明:片宽大于18 mm后对空气侧换热性能几乎没有影响,对空气侧压降影响较小;整机性能测试结果表明:片宽为18 mm的换热器与传统片宽换热器性能基本一致,但前者成本较低,产品竞争力提高。     

微通道换热器在R290家用空调器中的应用

以微通道换热器替代φ5 mm翅片管换热器作为冷凝器,在1.5 hp单冷R290家用空调器中进行整机性能配试,实现微通道换热器与R290家用空调器系统较理想匹配。配试试验中通过对微通道换热器的不同翅片选取、流程调整及室外机风量的优化,提高空调器能效,降低系统R290充注量。根据最终对比试验,系统制冷量提高0.7%,能效比提高3.4%,R290充注量降低8.8%。综合比较性能、充注量和成本等因素,在单冷R290家用空调器中以微通道换热器替代φ5 mm翅片管换热器作为室外机冷凝器,可以满足整机配试要求,并具备实际产品产业化应用的可行性。     

小管径铜管换热器的性能及成本分析

对比分析采用R410A制冷剂的Ф7mm铜管换热器与Ф5mm铜管换热器的性能与成本。测试结果表明,在相同的测试工况和迎风尺寸下,Ф5mm铜管换热器的换热效果比Ф7mm铜管换热器的好,可以节约大量铜材和铝材,且制冷剂充注量减少。     

翅片管式换热器的翅片耐腐蚀涂层研究

分析翅片管式换热器环境腐蚀的主要因素和常用防腐涂层的暴露试验数据,参考施加2种涂层的铜翅片-铜管换热器和铝翅片-铜管换热器的比对试验数据,对铜和铝的几种耐腐蚀涂层进行评价。有学者的研究表明,涂层铜翅片-铜管换热器的耐腐蚀性能优于涂层铝翅片-铜管换热器。同时介绍其他涂层,可为翅片管式换热器的防腐提供参考。     

微通道换热器在热泵型空调机组中的应用

将微通道换热器应用到北美市场典型的分体式热泵型空调机组中,并对采用微通道换热器的机组和采用铜管翅片式换热器的原机组的性能进行试验对比。试验结果表明,室内室外机均采用微通道换热器后,机组能力提高4％,制冷季节能效比（SEER）与制热季节能效系数（HSPF）分别提高2％和1％,换热器质量减轻44％,制冷剂充注量减少51％。平均结霜时间与原机组相比延长5％,平均除霜时间比原机组延长4％。此外,通过优化设计,制冷剂的分布更加均匀。对室外机微通道用换热器进行耐腐蚀性测试和压力交变疲劳测试,结果表明微通道换热器具有良好的可靠性。     

多元平行流冷凝器传热流动性能研究

平行流冷凝器空气侧采用间断型扩展表面的波纹型百叶窗翅片,制冷剂侧采用小水力直径的非圆截面微通道多孔铝制扁管,选用适合于该微尺度强化换热结构的传热和压降关联式,对某规格的平行流冷凝器建立数学模型并在一定工况下进行数值模拟.结果分析表明,制冷剂在非圆截面微通道内的冷凝过程中,表面张力对表面传热系数的强化效果明显;通过改变流程数和各流程管数来改变冷凝过程中的流通截面而达到调整流速的作用,从而可以保持较高的冷凝换热系数和较低的流动压降,与常规换热器相比具有显著的优越性.     

Condensation and evaporation heat transfer of R410A inside internally grooved horizontal tubes

Heat transfer coefficient and pressure drop were measured for condensation and evaporation of R410A and HCFC22 inside internally grooved tubes. The experiments were performed for a conventional spiral groove tube of 8.01 mm o.d. and 7.30 mm mean i.d., and a herring-born groove tube of 8.00 mm o.d. and 7.24 mm mean i.d. To measure the local heat transfer coefficients and pressure drop, the test section was subdivided into four small sections having 2 m working length. The ranges of refrigerant mass flow density was from 200 to 340 kg/(m² s) for both condensation and evaporation of R410A and HCFC22, and the vapour pressure was 2.41 MPa for condensation and 1.09 MPa for the evaporation of R410A. The obtained heat transfer data for R410A and HCFC22 indicate that the values of the local heat transfer coefficients of the herring-bone grooved tube are about twice as large as those of spiral one for condensation and are slightly larger than those of spiral one for the evaporation. The measured local pressure drop in both condensation and evaporation is well correlated with the empirical equation proposed by the authors.     

Study on thermal performance of micro-channel separate heat pipe for telecommunication stations: Experiment and simulation

A micro-channel separate heat pipe (MCSHP) as a cooling device for telecommunication stations (TSs) was experimentally investigated in this work. A steady-state mathematical model was built and validated with experimental data. The cooling capacity, inlet and outlet of refrigerant temperatures and refrigerant pressure of evaporator section were measured in an enthalpy difference laboratory (EDL). The average relative errors between simulation and experiment were less than 10%. The effects of geometrical design and environment conditions on thermal performance were analyzed using the validated model. As a result of the simulations, the refrigerant side pressure drop decreased by 96.61% at the flat tube height 3.0 mm compared to 1.4 mm. And the air side pressure drop decreased by 94.49%, when fin height ranged from 4 mm to 20 mm. The cooling capacity increased by 50.65% at the fin pitch 3.0 mm compared to 1.0 mm. These factors were of practical engineering importance in optimum design of MCSHP.     

微通道平行流冷凝器两相流传热和压降的修正方法

本文通过建立以R134a为制冷剂的微通道平行流冷凝器的分布参数模型,使用交复检验非线性法对微通道冷凝器两相区的传热和压降关联式进行修正,并与无修正的仿真模拟结果、传统简单多项式拟合修正法的结果进行了比较。结果表明,运用交复检验非线性法修正的效果要优于无修正及传统简单多项式拟合法,使用前者修正后可将换热量误差减少64. 5%,均方误差控制在3%以内;制冷剂侧压降误差减少82. 05%,均方误差控制在10%以内,该方法为换热量和制冷剂侧压降的修正提供了一种预测精度更高的思路和方法。     

Refrigerant R134a vaporisation heat transfer and pressure drop inside a small brazed plate heat exchanger

This paper presents the experimental heat transfer coefficients and pressure drop measured during refrigerant R134a vaporisation inside a small brazed plate heat exchanger (BPHE): the effects of heat flux, refrigerant mass flux, saturation temperature and outlet conditions are investigated. The BPHE tested consists of 10 plates, 72 mm in width and 310 mm in length, which present a macro-scale herringbone corrugation with an inclination angle of 65° and corrugation amplitude of 2 mm.The experimental results are reported in terms of refrigerant side heat transfer coefficients and frictional pressure drop. The heat transfer coefficients show great sensitivity both to heat flux and outlet conditions and weak sensitivity to saturation temperature. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow.The experimental heat transfer coefficients are also compared with two well-known correlations for nucleate pool boiling and a correlation for frictional pressure drop is proposed.     

分体式空调器长连接管制冷剂追加量的试验研究

基于制冷量为12 kW的风管送风式空调(热泵)机组进行试验研究,分析节流位置、工况等因素对长连接管制冷剂追加量的影响,得出9.52 mm液管和15.88 mm气管条件下R410A制冷剂追加量的参考值。研究发现,对于单冷型空调器,节流位置会对长连接管的制冷剂追加量产生较大影响,室内机节流时的追加量大于室外机节流;而对于热泵型空调器,节流位置对长连接管制冷剂追加量的影响较小。     

分液冷凝器在HFC410A空调系统的替换实验研究

汽液分离式冷凝器是一种管内高效冷凝换热器,它采用了一些强化换热手段,如多管程平行流冷凝、中间排液以及优化管子数目等。这里将该分液冷凝器用于HFC410A空调系统中,并进行了性能测试。结果表明:使用分液冷凝器后,HFC410A的制冷能力仅为原系统的96.4%,EER值为原来的93.8%,该分液冷凝器无法实现替换目的。通过分析发现,HFC410A对分液冷凝器的热力性能影响较大,HFC410A在分液冷凝器的气液分离效果变差,不再维持HCFC22在分液冷凝器中表现出来的近等温冷凝过程;在相同的冷凝温度下,HFC410A系统的循环质量流量较HCFC22系统减少1.2%~9.2%时,分液冷凝器的压降提高39.1%~52.6%。     

Experimental results and design procedures for minichannel condensers and evaporators using propylene

Hydrocarbons (HCs) present favorable thermodynamic and transport properties that make them attractive for use in refrigeration, air conditioning and heat pump systems. The major issue related to HCs is their flammability and hence the realization of low charge heat transfer devices is a key factor for their market placement. Although flammable refrigerants call for charge minimization, propylene heat transfer data inside minichannels is new in the open literature.In the present paper, condensation heat transfer, flow boiling heat transfer and two-phase pressure drop measurements taken with propylene (R1270) inside a 0.96 mm diameter minichannel are presented and compared against correlations.A comparative analysis of the condensation performance of R1270, R290 and two HFCs is made with the objective of minimizing the exergy losses, due to the driving temperature difference between saturation and wall and to the frictional pressure drop. An estimation of the condenser refrigerant charge is also performed. The flow boiling heat transfer performance of R1270 is discussed in comparison to the one of R290.