Abstract
The paper presents the results of experimental investigation of Novec 649 refrigerant condensation in tube minichannels. This is a low-pressure refrigerant. This investigations are basis for flow structures visualization during condensation in pipe minichannels. The local and the average values of pressure drop (Δp/L) and heat transfer coefficient α in the whole range of the changes of vapour quality (x = 1 ÷ 0) were calculated. On the basis of the obtained test results there was illustrated the influence of the vapour quality x, the mass flux density G and the inner diameter of channel d changes on the studied parameters. These results were compared with the calculation results based on the dependencies of other authors.
Highlights
Due to the development of technologies and miniaturization of power equipment, compact heat exchangers are very important area of studies around the world
Zhang et al [28] in his study presented the results of R22, R410A and R407C refrigerant condensation in single circular minichannels with internal diameters of 1.088 and 1.289 mm, with parameters in the ranges of: saturation temperature Ts = 30 - 40 °C, mass flux density G = 300 - 600 kg/m2s and vapour quality x = 0.9-0.1
Rajan [17] showed in his work that R410A refrigerant is more effective than R22 because the heat transfer coefficient for R410A is higher by approximately 30 % at boiling, and, in the same time, the pressure drop is lower by approximately 40%
Summary
Due to the development of technologies and miniaturization of power equipment (while increasing their efficiency), compact heat exchangers are very important area of studies around the world. In the work of Coleman and Garimella [7, 9] was found that for channels with a hydraulic diameter greater than 10 mm, the channel dimension and surface tension didn't significantly influence on flow and thermal parameters This proves that the experimental investigations of refrigerants condensation in mini and microchannels are very important. Zhang et al [28] in his study presented the results of R22, R410A and R407C refrigerant condensation in single circular minichannels with internal diameters of 1.088 and 1.289 mm, with parameters in the ranges of: saturation temperature Ts = 30 - 40 °C, mass flux density G = 300 - 600 kg/m2s and vapour quality x = 0.9-0.1. Very interesting will be a investigation of two-phase flow structures for new refrigerants
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