Local heat transfer coefficients during the evaporation of 1,1,1,2-tetrafluoroethane (R-134a) in a plate heat exchanger

Abstract

The evaporation heat transfer coefficient of the refrigerant R-134a in a vertical plate heat exchanger was investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, the local value of the heat transfer coefficient was calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux, heat flux, pressure of system and the flow configuration on the heat transfer coefficient were also taken into account and a comparison with literature data was performed.

U ovom radu je eksperimentalno ispitivan koeficijent prelaza toplote pri dvofaznom toku rashladnog fluida 1,1,1,2-tetrafluoroetana (R-134a) u vertikalnom pločastom razmenjivaču toplote. Površina ploče je podeljena u nekoliko segmenata duž vertikalne ose. U svakom od segmenata izračunata je lokalna vrednost koeficijenta prelaza toplote i prikazana u funkciji srednjeg stepena suvoće u segmentu. Zahvaljujući termoparovima postavljenim duž površine ploče, bilo je moguće odrediti temperaturne profile i raspodelu stepena suvoće duž ploče. Ispitivani su uticaji masenog fluksa, toplotnog fluksa, radnog pritiska i konfiguracije toka fluida na koeficijent prelaza toplote i izvršeno je poređenje sa odgovarajućim literaturnim podacima.