[雙語(yǔ)翻譯]--外文翻譯---可燃制冷劑的冷凝傳熱系數(shù)（英文）

1、Short communication Condensation heat transfer coefficients of flammable refrigerantsDongsoo Jung*,y,a, Soonam Chaea, Dongsoo Baea, Sukjae OhobaDepartment of Mechanical Engineering, Inha University, Incheon 402-751, Sout

2、h Korea bTechnoChem Co., Ltd., Pyungtaek-Si, Kyunggi-Do, South KoreaReceived 15 April 2003; received in revised form 18 September 2003; accepted 18 September 2003AbstractIn this study, external condensation heat transfer

3、 coefficients (HTCs) of six flammable refrigerants of propylene (R1270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of 39 ?C on a plain tube

4、of 19.0 mm outside diameter with a wall subcooling of 3–8 ?C under a heat flux of 7–23 kW m?2. Test results showed a typical trend that external condensation HTCs decrease with the wall subcooling. No unusual behavior or

5、 phenomenon was observed for these flammable refrigerants during experiments. HFC32 and DME showed 28–44% higher HTCs than those of HCFC22 due to their excellent thermophysical prop- erties. Propylene and butane showed t

6、he similar HTCs as those of HCFC22 while propane and isobutane showed 9% lower HTCs than those of HCFC22. Finally, a general correlation was made by modifying Nusselt’s equation based upon the measured data of eleven flu

7、ids of various vapor pressures including halogenated refrigerants. The general equation showed an excellent agreement with all data exhibiting a deviation of less than 3%. # 2003 Elsevier Ltd and IIR. All rights reserved

8、.Keywords: Condensation; Horizontal tube; Heat transfer coefficient; Mass transfer condensation; Propylene; Propane; Butane; Isobutane; R32Frigorige ` nes inflammables : coefficients de transfert de chaleur lors de la co

9、ndensationMots cle ´s : Condensation ; Tube horizontal ; Coefficient de transfert de chaleur ; Coefficient de transfert de masse ; Propyle ` ne ; Propane ; Butane ; Isobutane ; R321. IntroductionDue to ozone layer d

10、epletion, CFCs and HCFCs have been phased out and various alternatives have been proposed for the past years. Traditionally, flammable refrigerants have not been accepted in normal refrigera- tion and air-conditioning ap

11、plications due to a safety concern. This trend, however, is somewhat relaxed these days due to an environmental mandate. Therefore, some of the flammable refrigerants have been applied to certainapplications as a pure wo

12、rking fluid or as one of the components of mixed working fluids [1,2]. For instance, isobutane (R600a) has dominated the European refrig- erator/freezer sector for the past decade [1]. Other countries such as India and C

13、hina also would like to use it in their own refrigerator/freezer sector [3,4]. Recently, such hydrocarbons as propane (R290) and propylene (R1270) are also proposed and actually used as working fluids in heat pumps for h

14、eating applications in Europe [5]. In fact, hydrocarbons are known to offer such advantages as a low cost, availability, compatibility with the conventional mineral oil, and environmental friend- liness [1,5,6]. Jung et

15、al. [7] demonstrated that dimethyl- ether (DME, RE170) is also a good refrigerant to replace CFC12. DME which is flammable has good0140-7007/$35.00 # 2003 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig

16、.2003.09.006International Journal of Refrigeration 27 (2004) 314–317 www.elsevier.com/locate/ijrefrig* Corresponding author. Tel.: +82-32-860-7320; fax: +82- 32-868-1716. E-mail address: dsjung@inha.ac.kr (D. Jung). y As

17、societe Member of IIR as of July 1998.hNusselt ¼ 0:725 ?f ?f ? ?g ? ?gk3 f hfg ?fDTD? ?1=4ð1ÞThe predicted values by Eq. (1) are 5.8–9.7% lower than the measured ones for all fluids tested. This difference

18、 was caused mainly by the assumption used in deriving Nusselt’s equation that the condensate film is in laminar flow regime. In fact, however, the condensate film is wavy even at low Reynolds numbers causing a convection

19、 cur- rent and also reducing the film thickness, which was observed through the sight glass. This phenomenon that measured HTCs were higher than those calculated by Nusselt’s equation was also observed for other fluids a

20、s well [9,10,14]. This comparison showed that the present data for the flammable refrigerants are quite reasonable.Fig. 2 illustrates the measured condensation HTCs of six refrigerants as a function of wall subcooling. I

21、n Fig. 2, HTCs of HCFC22 and HFC134a from Refs. [9,10] are included for reference. Data of various flam- mable refrigerants of different vapor pressures exhibited a typical trend that external condensation HTCs decrease

22、as the wall subcooling increases. Among the refrigerants tested, HFC32 showed the highest HTCs which are approximately 44% higher than those of HCFC22. This is due to its excellent thermodynamic and transport properties

23、of the liquid phase. HFC32 has the largest liquid density, density difference and second largest liquid thermal conductivity among the refriger- ants tested, which have a significant effect on heat trans- fer as shown by

24、 Eq. (1). DME has the second highest HTCs which are approximately 28% higher than those of HCFC22 due also to its good thermodynamic and transport properties. Especially the liquid thermal con- ductivity of DME is the la

25、rgest among the refrigerants tested. Propylene and butane have the similar HTCs asthose of HCFC22 while propane and isobutane have the similar HTCs as those of HFC134a, which are roughly 9% lower than those of HCFC22 as

26、shown in Fig. 2. Finally, an attempt was made to provide a general correlation for the external condensation of both halo- genated refrigerants and flammable refrigerants based upon the consistent measurements. So far, d

27、ata for ele- ven refrigerants have been measured including CFC11, CFC12, HCFC22, HCFC123, HFC134a [9,10] and six fluids covered in this study. A regression analysis showed that increasing the constant in Nusselt’s equa-

28、tion by 9%, as in Eq. (2), provides an excellent fit for all data with less than 3% deviation as shown in Fig. 3.hpre ¼ 0:79 ?f ?f ? ?g ? ? gk3 f hfg ?fDTD? ?1=4ð2ÞFig. 2. Condensation HTCs as a function o

29、f wall subcooling.Fig. 3. Comparison of various refrigerants’ data with a general correlation.Fig. 1. Comparison of the present data with Nusselt’s equation.316 D. Jung et al. / International Journal of Refrigeration 27