Comparison of heat transfer coefficient during evaporation of natural refrigerants and R-1234yf in horizontal small tube

Calculation Method for Flow Boiling and Flow Condensation of R134a and R1234yf in Conventional and Small Diameter Channels

“…Amongst the collected data, the criterion of minichannels, i.e. Con > 0.5, is fulfilled only by the research due to De Col et al [10] and Kwang-Il Choi [13] for R1234yf, while for R134a this criterion is fulfilled by research due to Owhaib et al [19], Shiferaw et al [20], Martin-Callizo et al [21], Consolini and Thome [22], Mahmoud et al [23], and Anwar et al [25]. It can therefore be concluded that for both R134a and R1234yf, the transition from conventional size channels to minichannels takes place at a channel diameter smaller than 1.5mm.…”

Prediction of flow boiling heat transfer data for R134a, R600a and R290 in minichannels

“…Analysis presented in the following parts is conducted on the basis of available experimental data from literature due to Mancin et al [5], Ong and Thome [6], Tibiriçá and Ribatski [7], Lu et al [30], Copetti et al [17] for R14a, Copetti et al [17] for R600a and Choi et al [19], Wang et al [20] for R290. Table 1 shows the characteristic range of parameters analyzed in the experiments.…”

“…2. According to the division that Con greater than 0.5 corresponds to minichannels it can be concluded that experimental data due to Ong and Thome [6] and Choi et al [19] for internal diameter equal to 1.5 mm belong to the concept of minichannel size, whereas other data belong to the conventional size channels. 6 show the results of calculations of heat transfer coefficient for considered refrigerants such as R134a, R600a, R290 using three mentioned earlier models based on Eqs.…”

“…(13), α th . Figure 12: Comparison of test results, αexp, [17,19,20] with the predictions obtained using Eq. (13), α th .…”

“…Choi et al [19] conducted the experimental study for flow boiling of R290, R717 and R1234yf in tubes with internal diameter of 1.5 and 3 mm. The results have been obtained by tests conducted for mass flux ranging from 50 to 600 kg/m 2 s, heat flux from 5 to 60 kW/m 2 and saturation temperature from 0 to 10 o C.…”