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Heat Transfer Characteristics and Two-Phase Flow Performance

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J1: Heat and Mass Transfer".

Deadline for manuscript submissions: closed (25 May 2023) | Viewed by 16437

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Prof. Dr. Krystian Czernek

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Department of Process and Environmental Engineering, Faculty of Mechanical Engineering, Opole University of Technology, ul. Prószkowska 76, 45-758 Opole, Poland
Interests: two-phase flow; mass transfer; fluid mechanics; thermal engineering; heat exchangers
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Prof. Dr. Stanislaw Witczak

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Department of Process and Environmental Engineering, Faculty of Mechanical Engineering, Opole University of Technology, ul. Prószkowska 76, 45-758 Opole, Poland
Interests: multiphase flow; heat transfer; energy
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Prof. Dr. Jerzy Hapanowicz

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Department of Process and Environmental Engineering, Faculty of Mechanical Engineering, Opole University of Technology, 5 MikolajczykaStr, 45-271 Opole, Poland
Interests: process engineering; process apparatus; rheology of suspensions and emulsions; Multiphase flows; experimental research

Prof. Dr. Roman Dyga

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Special Issue Information

Dear Colleagues,

Two-phase flow is a phenomenon occurring in many technological systems in modern industry, both in relation to transport processes and the thermal processing of liquid substances. As an example, we can mention here the chemical, petrochemical, pharmaceutical or food industries, in which a significant number of processes take place in two-phase systems. The simultaneous presence of gas and liquid phases, resulting from the nature of these processes, creates many difficulties in ensuring appropriate operating conditions for various types of apparatus. Examples of this occur in heat exchangers, evaporators and reactors, in which momentum, heat and mass exchange processes are carried out.

The main reasons for the occurring operational problems can be attributed to the high stochasticity of the gas–liquid two-phase flow. Maintaining proper process parameters is difficult. Such solutions, which ensure correct operation of the process equipment and, at the same time, allow eliminating unfavorable phenomena connected with the course of the processes, are gaining importance. These phenomena may include flow instability, formation of deposits on the surfaces of heating tubes of exchangers and evaporators, foaming of liquids, instability of interfacial surfaces, etc. One way to look for such solutions is to point out the possibility of realizing heat or mass transfer processes in the most efficient flow range.

This Special Issue of Energies, “Heat Transfer Characteristics and Two-Phase Flow Performance”, is addressed to specialists from all over the world who deal with mathematical modeling and experiments on heat and fluid flow. We expect papers dealing with solutions of problems of scientific and industrial relevance in the broad fields of heat transfer and fluid transportation. Papers addressed to the Special Issue will not only solve specific engineering problems but also serve as a catalyst for future directions and priorities in the research and development of heat transfer and fluid flow.

Prof. Dr. Krystian Czernek
Prof. Dr. Stanislaw Witczak
Prof. Dr. Jerzy Hapanowicz
Prof. Dr. Roman Dyga
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

two-phase flow
heat transfer
heat exchangers
hydrodynamics
measurements system
flow pattern
void fraction

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Published Papers (7 papers)

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Research

20 pages, 4608 KiB

Open AccessArticle

Investigation of Heat Transfer and Pressure Drop for R744 in a Horizontal Smooth Tube of R744/R404A Hybrid Cascade Refrigeration System—Part 2: Low-Temperature Region

by Min-Ju Jeon

Energies 2023, 16(13), 5108; https://doi.org/10.3390/en16135108 - 2 Jul 2023

Viewed by 1267

Abstract

This paper studies the evaporative heat transfer characteristics of R744 at low temperatures in a horizontal smooth tube as a cascade refrigeration system (CRS) among hybrid cascade refrigeration systems (HCRSs). There is a lack of research on the low-temperature evaporative heat transfer characteristics of R744 under the operating conditions of evaporators used in actual CRSs used in supermarkets. Therefore, this study aims to provide basic data on the evaporative heat transfer characteristics of R744 in the evaporators of refrigerators used in supermarkets. The tube used in the evaporation experiment conducted herein was a smooth horizontal copper tube with an inner diameter and length of 11.46 mm and 8000 mm, respectively. The experimental parameters were as follows: heat fluxes of 11.8–21.3 kW/m², mass fluxes of 76.3–175.1 kg/(m²·s), and saturation temperatures of −49.8–−30.2 °C. The main results are summarized as follows: the evaporative heat transfer coefficient of R744 can be predicted well by using the correlation formula of Chen at the evaporation temperature of −40 °C in the CRS. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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11 pages, 3928 KiB

Open AccessArticle

Measurements of Dispersed Phase Velocity in Two-Phase Flows in Pipelines Using Gamma-Absorption Technique and Phase of the Cross-Spectral Density Function

by Robert Hanus, Marcin Zych and Anna Golijanek-Jędrzejczyk

Energies 2022, 15(24), 9526; https://doi.org/10.3390/en15249526 - 15 Dec 2022

Cited by 11 | Viewed by 1423

Abstract

This paper concerns the application of the gamma radiation absorption method in the measurements of dispersed phase velocity in two-phase flows: liquid–gas flow in a horizontal pipeline and liquid–solid particles in a vertical pipe. Radiometric sets containing two linear ²⁴¹Am gamma radiation sources and two NaI(Tl) scintillation detectors were used in the research. Due to the stochastic nature of the signals obtained from the scintillation probes, statistical methods were used for their analysis. The linear average velocity of the dispersed phase transportation was calculated using the phase of the cross-spectral density function of the signals registered by the scintillation detectors. It is shown that in the presented cases, the phase method can be more accurate than the most commonly used classical cross-correlation one. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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23 pages, 6851 KiB

Open AccessEditor’s ChoiceArticle

Flow Boiling Heat Transfer of R134a in a Horizontal Smooth Tube: Experimental Results, Flow Patterns, and Assessment of Correlations

by Ernest Gyan Bediako, Petra Dančová and Tomáš Vít

Energies 2022, 15(20), 7503; https://doi.org/10.3390/en15207503 - 12 Oct 2022

Cited by 4 | Viewed by 1890

Abstract

This study presents an extensive evaluation of heat transfer characteristics, flow patterns, and pressure drop for saturation pressures ranging from 460–660 kPa in a horizontal smooth tube of 5 mm internal diameter using R134a as the working fluid. The effect of saturation pressures for mass fluxes of 150–300 kg/m²s and heat fluxes of 8.26–23.3 kW/m² which are typical of refrigeration and air conditioning applications are also investigated. Flow patterns observed during the study are predicted with a well-known flow pattern map of Wojtan et al. The experimental results are compared with seven (7) correlations developed based on different theories to find which correlation best predicts the experimental data. The results show that, at low mass flux, increasing saturation pressure results in an increased heat transfer coefficient. This effect is more pronounced in the low vapor quality region and the dominant mechanism is nucleate boiling. At high mass flux, increasing saturation pressure leads to an insignificant increase in the heat transfer coefficient. At this high mass flux but low heat flux, the heat transfer coefficient increases with vapor quality, indicating convective boiling dominance. However, for high heat flux, the heat transfer coefficient is linear over vapor quality, indicating nucleate boiling dominance. Pressure drop is observed to decrease with increasing saturation pressure. Increasing saturation pressure increases the vapor quality at which the flow pattern transitions from intermittent flow to annular flow. The flow patterns predicted are a mixture of slug and stratified wavy and purely stratified wavy for low mass fluxes. For increased mass fluxes, the flow patterns predicted are slug, intermittent, annular, and dryout. Cooper’s model was the best predictor of the experimental data and the trend of heat transfer coefficient. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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11 pages, 6749 KiB

Open AccessFeature PaperArticle

Investigation of Liquid–Gas Flow in a Horizontal Pipeline Using Gamma-Ray Technique and Modified Cross-Correlation

by Robert Hanus, Marcin Zych and Anna Golijanek-Jędrzejczyk

Energies 2022, 15(16), 5848; https://doi.org/10.3390/en15165848 - 11 Aug 2022

Cited by 17 | Viewed by 1954

Abstract

This article presents the application of the radioisotope absorption method in the study of two-phase water–air flow in a horizontal pipe. The measurement principle and the test stand are briefly described. The main part of the article presents the signal analysis methods applied to data obtained from scintillation detectors. Because these signals are mostly stochastic waveforms, they were analyzed statistically using the cross-correlation function (CCF), and methods that are a combination of CCF and differential methods: CCF/ASDF and CCF/AMDF, where ASDF is the average square difference function, and AMDF is the average magnitude difference function. Examples of the results of gas phase velocity measurement for four types of flow are presented. It was found that the CCF/ASDF and CCF/AMDF methods allow more accurate results of measurements of the dispersed phase to be obtained than the CCF method. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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18 pages, 4567 KiB

Open AccessArticle

Experimental Investigation of Two-Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of R448A inside Multiport Mini-Channel Tube

by Hieu Ngoc Hoang, Nurlaily Agustiarini and Jong Taek Oh

Energies 2022, 15(12), 4331; https://doi.org/10.3390/en15124331 - 13 Jun 2022

Cited by 8 | Viewed by 2794

Abstract

Regulations and restrictions against high global warming potential (GWP) refrigerants have been introduced to encourage the adoption of environmentally friendly refrigerants and mitigate the environmental impact of the HVAC industry. R448A, a zeotropic blend with a GWP of 1390, has recently been proposed as a drop-in replacement for R404A and R410A in commercial systems. In this study, the heat transfer coefficient and pressure drop characteristics of R448A within a multiport mini-channel tube were experimentally investigated. The experimental ranges of the mass and heat fluxes were 100 to 500 kg/(m²s) and 3–15 kW/m², respectively. Additionally, the range of quality from 0 to 1 was considered at two fixed saturated temperatures of 3 and 6 °C. The heat transfer coefficient increased with mass flux. Under low mass flux condition, the heat flux increased the heat transfer coefficient, but there was no noticeable effect of the saturated temperature on the heat transfer coefficient. At high mass flux, heat flux had no major effect on heat transfer, while a decrease in the saturated temperature was found to increase the heat transfer coefficient. Moreover, the pressure drop increased with an increase in the mass flux and vapor quality, whereas the heat flux did not affect the pressure drop. The heat transfer coefficient and pressure drop performance of R448A was compared with that of R410A inside the same tube. Finally, correlations for heat transfer coefficient and pressure drop were proposed for the prediction of heat transfer coefficient and pressure drop in practical applications. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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25 pages, 4434 KiB

Open AccessArticle

Investigation of Heat Transfer and Pressure Drop for R744 in a Horizontal Smooth Tube of R744/R404A Hybrid Cascade Refrigeration System—Part 1: Intermediate Temperature Region

by Min-Ju Jeon

Energies 2022, 15(6), 2285; https://doi.org/10.3390/en15062285 - 21 Mar 2022

Cited by 1 | Viewed by 2829

Abstract

In this study, the evaporation heat transfer characteristics of an intermediate temperature of R744 in a smooth horizontal tube, when operating as an indirect refrigeration system (IRS) among hybrid cascade refrigeration systems (HCRSs), are evaluated. Studies on the characteristics of intermediate-temperature evaporation heat transfer under the operating conditions of evaporators used in actual refrigeration systems, such as IRS, cascade refrigeration systems, and HCRS, used in supermarkets are lacking. Thus, this study provides basic data on the characteristics of evaporation heat transfer of R744 in the evaporators of refrigerators used in supermarkets. The tube employed to the evaporation experiment in this study was a horizontal smooth copper tube with a length of 8000 mm and an inner diameter of 11.46 mm. The experimental variables were measured over a wide range of mass flux of 200–500 kg/(m²·s), heat flux of 10–40 kW/m², and saturation temperature of −40–0 °C. The main results are summarized as follows: (1) The application of Kandlikar’s correlation formula at an evaporation temperature of −20 °C in an IRS helps in a good prediction of the R744 evaporation heat transfer coefficient. (2) The pressure drop according to the heat and mass flux showed the same heat transfer coefficient trend, but the pressure drop at saturation temperature was different from the trend of heat transfer coefficient. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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24 pages, 9285 KiB

Open AccessArticle

Experimental Study of Horizontal Flow Boiling Heat Transfer Coefficient and Pressure Drop of R134a from Subcooled Liquid Region to Superheated Vapor Region

by Ernest Gyan Bediako, Petra Dančová and Tomáš Vít

Energies 2022, 15(3), 681; https://doi.org/10.3390/en15030681 - 18 Jan 2022

Cited by 5 | Viewed by 2826

Abstract

For the past few years, research in the field of flow boiling heat transfer has gained immense popularity for unravelling the dominant mechanism responsible for controlling heat transfer and identifying a parametric trend for understanding the characteristics of flow boiling heat transfer. This has led to several assumptions and models for predicting heat transfer during flow boiling without any known generalized mechanism. This study therefore seeks to experimentally study the characteristics of heat transfer during flow boiling over a wide range but small increase in vapor quality from a single-phase subcooled region through to a two-phase superheated vapor region. The study was performed with an R134a refrigerant in a single horizontal circular stainless-steel smooth tube that had an internal diameter of 5 mm. In this experimental study, local heat transfer coefficients and frictional pressure drop were measured for low heat fluxes of 4.6–8.5 kW/m², mass fluxes of 200–300 kg/(m²s), vapor quality from −0.1 to 1.2 and a low constant saturation pressure of 460 kPa. Flow patterns observed during the study were recorded with a high-speed camera at 2000 fps. In covering a wide range of vapor quality, a peak of heat transfer coefficient near a vapor quality of zero and a local minimum observed in the low vapor quality region were observed, and both were sensitive to heat flux and mildly sensitive to mass flux. Generally, at low vapor quality, the heat transfer coefficient deteriorated with vapor quality and this was sensitive to heat flux but insensitive to mass flux and vapor quality, indicating nucleate boiling dominance in low vapor quality regions. In high vapor quality regions, the heat transfer coefficient was sensitive to mass flux and insensitive to heat flux. This indicates the dominance of convective boiling. In the low vapor quality regions, the flow patterns observed were slug and intermittent, while in the high vapor quality region, annular and mist flow patterns were observed. Generally, frictional pressure drop increased with increasing mass flux and vapor quality in the two-phase region. Full article

(This article belongs to the Special Issue Heat Transfer Characteristics and Two-Phase Flow Performance)

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