Reasons for drop in shell-and-tube condenser performance when replacing R22 with zeotropic mixtures. Part 2: investigation of mass transfer resistance effects
Artikel i vetenskaplig tidskrift, 2004

Detailed calculations of condensation outside a column of horizontal smooth tubes have been carried out in order to investigate the influence of mass transfer resistance for a zeotropic refrigerant mixture. Diffusive transport is calculated locally in both phases. Calculation results show that mass transfer resistance in the gas phase reduces heat transfer by 10–20% for a binary mixture with a glide similar to that of R407C. The decrease in heat transfer due to poor mixing in the condensate is from 15 to 65% for the conditions investigated; the lower the duty, the greater the decrease. Results show that if assuming mixing in the condensate by diffusion only, the degrees of mixing and the duty dependency are similar to results in earlier work where calculations were matched to experimental data. Diffusion is likely to be the dominant mixing mechanism in the condensate, and the mixing is poor under certain conditions, which might explain the drop in condenser performance for some heat pump applications.

Mass transfer

Parameter

Tube

R22

R407C

Heat transfer

Experiment

Shell-and-tube exchanger

Measurement

Condensation

Författare

Tord Karlsson

Chalmers, Institutionen för kemiteknik och miljövetenskap, Värmeteknik och maskinlära

Lennart Vamling

Chalmers, Institutionen för kemiteknik och miljövetenskap, Värmeteknik och maskinlära

International Journal of Refrigeration

0140-7007 (ISSN)

Vol. 27 5 561-566

Ämneskategorier

Kemi

DOI

10.1016/j.ijrefrig.2004.03.012