R1234yf/R152a用作汽车空调制冷剂的配比范围研究

使用PR方程结合vdW法则建立了R1234yf/R152a的热物性模型,在此基础上结合余函数法编制了R1234yf/R152a的热力性质和制冷系统循环性能计算程序。在汽车空调制冷工况下,获得了R1234yf/R152a在不同摩尔组分比下的压力比、排气温度、COP、单位质量制冷量、单位体积制冷量和压缩机吸气口比容,并与R134a和R1234yf/R134a(0.89/0.11)进行了比较。之后,结合燃烧速度、GWP与循环性能获得了适宜的摩尔组分比范围。当R1234yf的液相摩尔分数在0.65～0.67时,R1234yf/R152a为近共沸混合物,具有较高的安全性,且制冷循环性能与R134a较为接近。     

基于KULI的带回热器的R134a与R1234yf汽车空调系统仿真分析

使用KULI软件建立了带回热器的一维汽车空调仿真模型,通过试验数据验证了该模型的可靠性,并分别对R134a和R1234yf的系统性能进行了仿真分析。仿真结果表明:R1234yf系统的冷凝压力比R134a低,蒸发压力比R134a高;R134a系统的排气温度比R1234yf高10.5~17.9℃;R134a系统的制冷量比R1234yf高1.6%~3.4%;R134a系统的COP比R1234yf高0.2%~4.2%。     

混合制冷工质R1234yf/R32 PVTx性质的实验研究

利用基于Burnett法搭建的PVTx性质测试系统测量了混合制冷工质R1234yf/R32在温度为253~313 K范围内、R1234yf的质量分数为20%时的气相PVTx性质.详细介绍了该测量系统基于Burnett法的测量原理和PVTx性质测试系统的实验步骤,并对各种测量误差及不确定度进行了分析.根据实验数据拟合出混合制冷工质的气态维里方程,并比较了第二、第三维里系数与温度的关系.结果表明:实验数据与拟合得到的方程具有较好的一致性,为基础热物性研究和进一步研究替代制冷剂提供了详实的数据.     

新型制冷剂R1234yf/R134a可燃性实验研究

根据美国材料试验学会标准研制可燃性实验装置,对实验装置进行性能和误差分析,并进行校验。R1234yf环境性能好,臭氧消耗潜能值为零,其三元混合物R1234yf/DME/R134a可作为一种新型空调制冷剂。测试不同体积比时二元混合工质R1234yf/R134a的可燃性数据,得到其爆炸极限和临界抑爆比,并给出三元混合物R1234yf/DME/R134a的临界爆炸极限曲线图。结果表明:当R134a和R1234yf的体积比约为2时,二元混合物R1234yf/R134a达到临界抑爆点。     

太阳能辅助R744热泵系统在中原地区的性能分析

针对中原地区典型气象年(辐射极大)的冬季气象条件,通过所建立的跨临界循环热泵系统性能模拟平台,计算并对比分析了太阳能辅助R744跨临界循环及单一R744热泵系统在中原地区的运行特性;讨论了热水出水温度、传热窄点温差改变时系统制热性能系数和最优放热侧压力的变化规律。研究结果表明,在设定工况下,联合应用太阳能集热系统,R744热泵系统性能在冬季可得到大幅度提高,平均提高34.4%;热水出水温度低于70℃时,系统性能提高幅度超过36.0%;但传热窄点温差增大,系统性能有一定程度下降。     

太阳能联合空气源热泵系统温室供热实验研究

在西安地区一座日光温室中采用太阳能联合空气源热泵供热系统进行对比实验研究,比较太阳能联合空气源热泵系统改善温室内的温度、湿度及土壤温度等环境因素,分析评价太阳能联合空气源热泵系统在日光温室冬季应用的效果。实验结果表明:太阳能联合空气源热泵供热系统不仅可明显提高温室内的空气温度和土壤温度,还可有效降低温室内的湿度;在实验天气条件下,热泵单独供热时,系统的COP为2.2~3.5;太阳能联合空气源热泵供热时,系统的COP为2.9~6.0;相比于阴天工况,晴天条件下,太阳能蓄热供热时间较长,热泵补充供热时间缩短,系统COP较高。     

太阳能-空气源热泵联合干燥系统设计及干燥枸杞的实验研究

为缩短枸杞干燥时间,提高干制枸杞的质量,减少能源消耗,本文提出了一种新型太阳能–空气源热泵联合干燥系统。该系统主要由太阳能集热器和空气源热泵机组等设备组成,可以实现太阳能单独干燥、热泵单独干燥和太阳能–空气源热泵联合干燥三种工作模式。本文根据枸杞的干燥特性,分段设定最佳的干燥温度,进行了热泵单独运行和太阳能–热泵联合运行两种工作模式下干燥枸杞的对比实验。结果表明,干燥50 kg枸杞,太阳能–热泵联合运行比热泵单独运行节省了2.9 kW?h电能,若同时除去系统本身的耗能,节省的电能占热泵单独运行耗电量的29.5%。同时,与太阳能单独干燥相比,太阳能–热泵联合干燥具有较高的除湿能耗比,两者最大差值为0.71 kg/(kW?h)。本文提出的太阳能–热泵联合干燥系统具有提高干燥产品的品质、缩短干燥时间和节约干燥成本等优点,适宜推广。     

增加蓄热装置的空气源热泵-太阳能互补供暖系统优化研究

针对低温工况下多能互补供暖系统的工作性能和经济性较差等问题,文章设计了太阳能-蓄热空气源热泵互补供暖系统,该系统在传统太阳能-空气源热泵互补供暖系统的基础上增加了蓄热装置,提高了空气源热泵入口的空气温度。文章基于TRNSYS软件构建了太阳能-蓄热空气源热泵互补供暖系统的仿真模型,并分析了空气源热泵制热能效比的变化,对比了入口处有、无蓄热装置时太阳能-蓄热空气源热泵互补供暖系统的热性能和经济性。分析结果表明:在增设蓄热装置后,空气源热泵的平均制热能效比提高了34.87%;在供暖期内,系统的平均代价火用效率提高了3.24%,总能耗减少了2×10~7kJ,费用年值与太阳能保证率之比ACSF减少了3.3元;系统中各部件的火用效率均有所提高,空气源热泵工作性能的改善最为显著,火用效率提高了4.63%。     

太阳能复合热泵的节能效果分析

文中通过对太阳能—水源热泵、太阳能—空气源热泵、太阳能—地源热泵及带蓄热装置的太阳能复合热泵系统进行分析,对比了各种太阳能复合热泵的原理及应用效果。通过分析数据得出,采用将太阳能热泵系统与其他热泵相结合的方式,整体系统的COP能达到3以上,有效地提高了整体系统的能源利用效率,为未来太阳能利用提供了一种高效利用的方向。     

涡旋压缩机闪发器热泵系统的试验研究

介绍了涡旋压缩机闪发器热泵系统,并在结构特点方面与对应的过冷器系统作了比较。对研制的闪发器热泵系统原型机进行了试验研究和性能分析。结果表明:随蒸发温度的降低,原型机的制热量有所减少,但减少的速度明显低于普通热泵系统,压缩机耗功有所增加,但增加的幅度不大;闪发器系统在低温工况下比过冷器系统可以更有效提高空气源热泵的低温制热性能,是寒冷地区用小型空气源热泵比较适宜采用的系统。     

Cycle performance study on R32/R125/R161 as an alternative refrigerant to R407C

This paper presents the new ternary non-azeotropic mixture of R32/R125/R161 as an alternative refrigerant to R407C. The physical properties of the ternary mixture are similar to those of R407C, and it is environmental friendly, that is, it has zero ozone-depletion potentials (ODP) and lower global warming potentials (GWP) than R407C. Theoretical cycle performances of R32/R125/R161 and R407C are calculated and analyzed firstly. Based on the theoretical study, experimental tests are performed on a vapor-compression refrigeration system with a rotor compressor which was originally designed for R407C (without any modifications to system components for R407C). Experimental results under different working conditions indicate that the pressure ratio and power consumption of the new refrigerant are lower than those of R407C, and its refrigerating capacity and coefficient of performance (COP) are superior to those of R407C, respectively, and its discharge temperature is slightly higher than that of R407C. Therefore, the new refrigerant R32/R125/R161 could be considered as a promising refrigerant to R407C.     

On blends R32/R134a and R32/R125: Thermodynamic and heat transfer aspects

In this paper the author develops an algorithm on the basis of heat and thermodynamics theory, to predict data for film condensation on horizontal integral—fin tubes for R32/R134a and R32/R125 mixtures in 25/75, 50/50 per cent compositions by mass correspondingly. Emphasis is focused on the presentation of thermophysical properties of the blends involved in the process considered, i.e. liquid density, viscosity, surface tension, thermal conductivity and latent heat of vaporization. The main point of this work is to define with computational techniques the blend with the most favourable composition, as an environmentally acceptable solution for R22 replacement in some shell‐side condensers. Copyright © 2001 John Wiley & Sons, Ltd.     

Prediction of the condensation and boiling characteristics of R12 substitutes R22/r152a/R114 and R22/R152a/R124 inside enhanced-surface tubing

In this paper, the heat-transfer behaviour of two ternary refrigerant blends proposed as an R12 substitute, has been studied during condensation and boiling inside horizontal enhanced surface tubing. Correlations are proposed to predict the average heat transfer coefficients as well as pressure drops of newly proposed ternary refrigerant blends flow, inside enhanced surface tubing.     

Ozone friendly binary blends R 32/R 134a and the ternary R 407b

The objective of this paper is to present thermodynamic properties and characteristics of the binary refrigerant mixtures R 32/R 134a in compositions 20/80%, 30/70%, 40/60% by mass and of the ternary mixture R 407b: 10 wt% R 32+70 wt% R 125+20 wt% R 134a. A computer code has been developed and by use of a Peng–Robinson type equation of state, PVT data for all working fluids are determined. Based on the thermodynamics theory, analytical relationships for the enthalpy, entropy, constant pressure and constant volume specific heats as well as for k-type isentropic change exponents are given. Furthermore, comparisons are provided by means of diagrams illustrating the influence of state conditions on the k-type exponents k_p,V, k_T,V, k_p,T, and classical k (k=c_P/c_V). A systematic study has also been carried out and the data obtained are plotted for a better physical feeling related to the sound velocity of real gas for the R 32/R 134a blend in composition 20/80%. The results are compared with corresponding ones of the ternary R 407b.     

PERFORMANCE ANALYSIS OF VAPOUR COMPRESSION REFRIGERATION WITH R22/R124/R152a REFRIGERANT

In this paper, the performance of vapour compression refrigeration with R22/R124/R152a as the refrigerant is presented. A mathematical model of the system characteristics is developed and the simulated results agreed quite well with those of the experiments. The model was also used to analyse the most suitable composition of the refrigerant. It was found that the required composition was obtained when the mass fraction of R22 was in the range 0.2–0.4. © 1997 by John Wiley & Sons, Ltd.     

R6 and R5 procedures: The way forward

This paper first briefly summarises the existing methods in the low-temperature fracture assessment procedure, R6, and the high-temperature procedure, R5, for treating the effects of secondary stresses on structural integrity. Recently, there have been a number of developments, which identify the way forward for these procedures. A modified J-integral definition has been derived, which is path independent for cases of proportional and non-proportional loading and is ideal for evaluating the crack driving force for defects in secondary and residual stress fields. Results of finite element analysis are presented that show that the use of the modified J-integral can lead to a lower crack driving force for secondary stresses than current simplified R6 methods. More detailed calculations have assessed the effects on fracture of a slowly growing crack and constraint effects associated with secondary stresses. Preliminary results are presented, showing the long-term potential of more advanced methods in providing significant benefits in structural integrity assessments. For high-temperature applications, the paper presents methods for calculating the relaxation of secondary stresses due to both creep strain and creep crack growth, extending current methods in R5 that only allow for relaxation due to creep strain. Related work addressing the combined effects of plasticity and creep on relaxation of the crack tip fields is also presented and the results are illustrated for a typical geometry and loading.     

Experimental study of R152a and R32 to replace R134a in a domestic refrigerator

This paper presents an experimental study of R152a and R32, environment-friendly refrigerants with zero ozone depletion potential (ODP) and low global warming potential (GWP), to replace R134a in domestic refrigerator. A refrigerator designed and developed to work with R134a was tested, and its performance using R152a and R32 was evaluated and compared with its performance when R134a was used. The results obtained showed that the design temperature and pull-down time set by International Standard Organisation (ISO) for small refrigerator were achieved earlier using refrigerant R152a and R134a than using R32. The average coefficient of performance (COP) obtained using R152a is 4.7% higher than that of R134a while average COP of R32 is 8.5% lower than that of R134a. The system consumed less energy when R152a was used. The performance of R152a in the domestic refrigerator was constantly better than those of R134a and R32 throughout all the operating conditions, which shows that R152a can be used as replacement for R134a in domestic refrigerator.     

混合工质R134a/R23替代R22的可行性研究

叙述了基于新型环保型混合制冷剂R134a/R23替代制冷剂R22的问题,以及通过REFPROP7.5,对混合工质R134a/R23从物性和热力学特性进行的理论计算分析,指出,由质量分数为70%的R134a和质量分数为30%的R23组成的混合制冷剂与R22性能最为接近,在变工况运行条件下,其COP值比R22高8%左右,其冷凝压力比同条件下用R22作为循环工质低21%～36%,理论上完全具有替代R22的可能性。     

含R227ea的混合制冷剂替代R22研究

由于R410，R407系列混合制冷剂在替代R22方面的不足，更多新型的制冷剂列入了研究。R227ea具有良好的环境性能，最典型的特点是具有很好的阻燃性。文章对含R227ea各种混合物进行了理论计算和比较，并对其安全性进行了分析。计算结果表明，混合物R32／R134a／R227ea及R32／R125／R227ea不论是COP还是Qv值，都能和R22相匹配，而且优于R410A的最大特点是其冷凝压力大大降低，甚至低于R22，非常有利于原装置替代。     

The performance of a triple pressure level absorption cycle (TPLAC) with working fluids based on the absorbent DMEU and the refrigerants R22, R32, R124, R125, R134a and R152a

This paper compares the performance of a single-stage triple pressure level (TPL) absorption cycle with different refrigerant–absorbent pairs. Four HFC refrigerants namely: R32, R125, R134a and R152a which are alternative to HCFC, such as R22 and R124, in combination with the absorbent dimethylethylenurea (DMEU) were considered. The highest coefficient of performance (COP) and the lowest circulation ratio (f), were found as a function of the generator temperature for a given evaporating and cooling water temperatures. The sensitivity of the COP and f for evaporator and cooling water temperatures changes at the maximum COP for the best three working fluids were also examined. It was obtained that the preferable pair is R124–DMEU and among working fluids based on HFC the preferable pair is the R125–DMEU.