scholarly journals An improved method for flow boiling heat transfer with account of the reduced pressure effect

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1261-1272
Author(s):  
Blanka Jakubowska ◽  
Dariusz Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boiling Heat Transfer ◽  
Pressure Effect ◽  
Flow Boiling ◽  
Improved Method ◽  
Reduced Pressure ◽  
Flow Boiling Heat Transfer ◽  
Semi Empirical ◽  
Selection Of

In the paper are presented the results using the authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data to investigate the sensitivity of the in-house developed model. In the work are presented the results of calculations obtained using the semi-empirical model on selected experimental flow boiling data of the refrigerants: R134a, R1234yf, R600a, R290, NH3, CO2, R236fa, R245fa, R152a, and HFE7000. In the present study, particular attention was focused on the influence of reduced pressure on the predictions of the theoretical model. The main purpose of this paper is to show the effect of the reduced pressure on the predictions of heat transfer during flow boiling.

scholarly journals Comparison of predictive methods for flow boiling heat transfer in conventional channels and minichannels – the effect of reduced pressure

2018 ◽  
Vol 240 ◽  
pp. 01028 ◽  
Author(s):  
Dariusz Mikielewicz ◽  
Blanka Jakubowska
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Boiling ◽  
Full Range ◽  
Two Phase ◽  
Reduced Pressure ◽  
Flow Boiling Heat Transfer ◽  
Wide Range ◽  
Semi Empirical ◽  
Selection Of

In the paper are presented the results of follow on studies from [1]–[3] using authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data collected from various researchers to investigate the sensitivity of the in-house developed model. The collected experimental data came from various studies from literature and were conducted for the full range of quality variation and a wide range of mass velocity and saturation temperatures. In the work are presented the results of calculations obtained using the in-house developed semi empirical model on selected experimental flow boiling data of the refrigerants: R134a, R1234yf, R600a, R290, NH3, CO2, R236fa, R245fa, R152a and HFE7000. In the present study the particular attention was focused on the influence of reduced pressure on the predictions of the theoretical model. The results of calculations were to test the sensitivity of the flow boiling model with respect to selection of the appropriate two-phase flow multiplier, which is one of the distinctive elements of the in-house model. The main purpose of this paper however is to show the effect of the reduced pressure on the predictions of heat transfer during flow boiling.

scholarly journals The effect of reduced pressure on carbon dioxide flow boiling heat transfer in minichannels

2018 ◽  
Vol 70 ◽  
pp. 02012
Author(s):  
Dariusz Mikielewicz ◽  
Blanka Jakubowska
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Carbon Dioxide ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
Reduced Pressure ◽  
Flow Boiling Heat Transfer

In the paper presented are the results of the study on the effect of reduced pressure on flow boiling heat transfer data in minichannels as well as conventional ones. That effect renders that most of heat transfer correlations fail to return appropriate results of predictions. Mostly they have been developed for the reduced pressures from the range 0.1-0.3. The special correction has been postulated to the in-house model of flow boiling and condensation which modifies the two-phase flow multiplier as well as the temperature gradient in pool boiling. Four two-phase flow multiplier models were tested for this purpose, i.e. due to Friedel, Tran, Müller-Steinhagen and Heck and finally its in-house modification for applicability to minichannels. The model has been tested against a large selection of experimental data collected from various researchers to investigate the sensitivity of the in-house developed model. The collected experimental data came from various studies from literature and were conducted for the full range of quality variation and a wide range of mass velocity and saturation temperatures. In the work are presented the results of calculations obtained using the in-house developed semi empirical model on selected experimental flow boiling data related to carbon dioxide.

Review: General Issues and Correlations for Predicting Flow Boiling Heat Transfer Coefficients in Micro-Scale Channels

2015 ◽  
Vol 23 (04) ◽  
pp. 1530003 ◽  
Author(s):  
Chang Yong Park
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Inertial Force ◽  
Viscous Force ◽  
Vapor Quality ◽  
Micro Scale ◽  
Continuous Decrease ◽  
Flow Boiling Heat Transfer

A review study was performed for basic heat transfer mechanism and quantitative analysis of correlations for flow boiling heat transfer in micro-scale channels. Several criteria for determining threshold diameter for micro-scale channels were discussed and the concept of confinement number was commented. The distinctive feature of flow boiling in micro-scale channels were considered and it was found out that the effect of the heat flux, latent heat, viscous force, surface tension, and inertial force was more significant. Important dimensionless parameters were summarized and it was pointed out that the boiling number, capillary number, and Weber number could be expected to play important roles at flow boiling in micro-scale channels. 17 correlations for flow boiling in micro-scale channels were reviewed in this study, and they were categorized by three types of correlations such as an equivalent Nusselt number correlation, a correlation with superposition of nucleate and convection boiling mechanism, and a flow pattern-based correlation. The predicted values by the correlations were compared with 536 experimental data from four different literatures and a correlation with smallest prediction errors was found. Some correlations showed distinct trends of convection heat transfer coefficient (h) change with respect to the variation of vapor quality. The trends are categorized by three trends such as noticeable increase of h with the increase of vapor quality and significant continuous decrease after dryout point, minor increase and decrease or decrease and increase of h, and gradual and continuous decrease of h with the increase of vapor quality. For each trend of h change, recommendable correlations and their basic equation forms were proposed to compare the prediction results with experimental data or to develop a new correlation by modifying existing correlations.

Correlation of the Flow Pattern and Flow Boiling Heat Transfer in Microchannels

2011 ◽  
Author(s):  
Vladmir V. Kuznetsov ◽  
Alisher S. Shamirzaev ◽  
Igor A. Kozulin ◽  
Stanislav P. Kozlov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Pattern ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat Flux ◽  
Reduced Pressure ◽  
Heat Transfer Deterioration ◽  
Flow Boiling Heat Transfer

Flow boiling in microchannels is characterized by the considerable influence of capillary forces and constraint effects on the flow pattern and heat transfer. In this paper we used the flow patterns of gas-liquid flow in rectangular microchannel to explain the regularities of refrigerants flow boiling heat transfer. The characteristics of the flow such as frequency of elongated bubbles, their length, velocity of liquid and gas phases were determined by dual laser flow scanning for the upward and horizontal nitrogen-water flow in microchannels with the size of 1500×720 μm. The flow pattern boundaries were determined also and compared with extended Mishima and Ishii correlation. Flow boiling heat transfer data were obtained for vertical and horizontal microchannel heat sink with similar channels using refrigerants R21 and R134a. The data on local heat transfer coefficients were obtained in the range of mass flow rate from 33 to 190 kg/m2s, reduced pressure from 0.03 to 0.25 and heat flux from 10 to 160 kW/m2. The flow boiling modes with nucleate and convective boiling were observed as far as heat transfer deterioration at high vapor quality and high heat flux. It was found that deterioration occurs for the annular flow when nucleate boiling was suppressed in a thin liquid film, and for elongated bubble flow pattern. The mechanism of heat transfer deterioration was discussed. The model of heat transfer deterioration was used to predict the experimental data.

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