Comparative study of flow condensation in conventional and small diameter tubes

Abstract

Flow boiling and flow condensation are often regarded as two opposite or symmetrical phenomena. Their description however with a single correlation has yet to be suggested. In the case of flow boiling in minichannels there is mostly encountered the annular flow structure, where the bubble generation is not present. Similar picture holds for the case of inside tube condensation, where annular flow structure predominates. In such case the heat transfer coefficient is primarily dependent on the convective mechanism. In the paper a method developed earlier by the first author is applied to calculations of heat transfer coefficient for inside tube condensation. The method has been verified using experimental data from literature on several fluids in different microchannels and compared to three well established correlations for calculations of heat transfer coefficient in flow condensation. It clearly stems from the results presented here that the flow condensation can be modeled in terms of appropriately devised pressure drop.

The analysis of thermal and flow characteristics of the condensation of refrigerant zeotropic mixtures in minichannels

“…In the case of heat transfer coefficient, we used the correlation of Akers [2], and Shah [24], Tang [26], Thome [29], Mikielewicz [21], and Cavallini [8]. The dependency of experimental results with the calculation results depends on both the internal diameter of a minichannel and the mass flux.…”

“…The authors of publications [20,21] proposed their own, generalized mathematical model for description of heat transfer and pressure drop during condensation and boiling of refrigerants in the small diameter channels. The analysis covered such refrigerants, as R134a, R404a, R600a, R290, R32, and R1234yf.…”

“…Based on the available research results the authors of the paper compared own mathematical models with correlations of other authors. In articles [20,21] to evaluate the value of heat transfer coefficient and pressure drop during condensation were used correlations due to Thome et Thome [28] presented the calculation model of heat transfer during the condensation of zeotropic mixtures in horizontal channels. He draws attention to three important issues concerning the condensation of mixtures, namely: 1) construction of new two-phase flow maps, 2) difference of heat transfer models of zeotropic mixtures and homogeneous refrigerants, 3) original heat transfer model concerning these mixtures.…”

Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel

“…is frequently encountered in industry and has been studied intensively for many years. The reliable prediction of flow parameters in two-phase flows is thereby an important aim; yet, heat transfer coefficients and pressure gradients predicted using leading methods often differ by more than 50% according to various reports [12][13][14].…”

Condensation of refrigerant R407C in multiport minichannel section

“…The measure of the effectiveness of this intensification is increase of the heat transfer coefficient. It can be said that the construction of modern refrigeration and air conditioning heat exchangers should meet the technical and environmental criteria, like: compact dimensions, high heat transfer efficiency, and minimal impact on the environment [3,4,13].…”