Author
Jong Joo Ha
Bio: Jong Joo Ha is an academic researcher from Korea University. The author has contributed to research in topics: Heat transfer & Mass transfer. The author has an hindex of 2, co-authored 3 publications receiving 41 citations.
Papers
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TL;DR: In this paper, both the numerical and experimental analyses in the absorption process of a bubble mode absorber were performed, where gas was injected into the bottom of the absorber at a constant solution flow rate.
Abstract: An absorber is a major component in the absorption refrigeration systems, and its performance greatly affects the overall system performance. In this study, both the numerical and experimental analyses in the absorption process of a bubble mode absorber were performed. Gas was injected into the bottom of the absorber at a constant solution flow rate. The region of gas absorption was estimated by both numerical and experimental analyses. A higher gas flow rate increases the region of gas absorption. As the temperature and concentration of the input solution decrease, the region of gas absorption decreases. In addition, the absorption performance of the countercurrent flow was superior to that of cocurrent. Mathematical modeling equations were derived from the material balance for the gas and liquid phases based on neglecting the heat and mass transfer of water from liquid to gas phase. A comparison of the model simulation and experimental results shows similar values. This means that this numerical model can be applied for design of a bubble mode absorber.
35 citations
TL;DR: In this paper, a relation between heat and mass transfer and Marangoni convection was investigated using mathematical modeling and numerical simulation in a falling film type absorber, which is able to predict velocity, temperature and mass fraction distribution.
Abstract: In an absorption refrigeration system, it is well known that water vapor absorption into lithium bromide (LiBr) aqueous solution is enhanced by the addition of surfactants. Marangoni convection plays a role but its mechanism has not clearly been understood yet. In the present study, a relation between heat and mass transfer and Marangoni convection was investigated using mathematical modeling and numerical simulation in a falling film type absorber. We used an advanced Marangoni convection model that is able to predict velocity, temperature and mass fraction distribution in a falling film type absorber. Firstly, the effect of Marangoni convection on heat and mass transfer in an absorber was examined. As a result, efficiency of heat and mass transfer was increased due to Marangoni convection. Secondly, analysis for the effects of different operating conditions on an onset of Marangoni convection was carried out. The Marangoni number for the onset of convection decreased as the initial temperature and initial water mass fraction of solution decreased.
6 citations
TL;DR: In this article, experimental analyses of the characteristics of heat transfer for removal of absorption heat in an ammonia-water bubble mode absorber were performed, where the heat transfer coefficient was estimated as a function of the input gas flow rate and solution flow rate, temperature, concentration, absorber diameter and height.
Abstract: An absorber is a major component in absorption refrigeration systems and its performance greatly affects the overall system performance. In this study, experimental analyses of the characteristics of heat transfer for removal of absorption heat in an ammonia-water bubble mode absorber were performed. The heat transfer coefficient was estimated as a function of the input gas flow rate, solution flow rate, temperature, concentration, absorber diameter and height, and input flow direction. The increase of gas and solution flow rate affects positively in heat transfer. However, the increase of solution temperature and concentration affects negatively. Moreover, under the same Reynolds number, countercurrent flow is superior to cocurrent flow in heat transfer performance. In addition, from these experimental data, empirical correlations that can explain easily the characteristics of heat transfer are derived.
1 citations
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TL;DR: In this paper, the effect of the drop-scale Marangoni effect with the sub-drop-scale local interfacial convection is investigated numerically, showing that the effect occurs only when the surface tension sensitivity to the solute concentration variation is above certain critical level.
56 citations
TL;DR: In this article, the authors presented a detailed analysis of the heat and mass transfer processes during the absorption of ammonia into water in a co-current vertical tubular absorber, where the absorption process progresses as the vapour and liquid contact inside the tubes.
54 citations
TL;DR: In this paper, two types of air-cooled absorber have been modelled: (i) falling film flow; (ii) bubble flow, and two models have been validated with experimental data obtained from a developed testing device and published numerical results of other authors from another model.
37 citations
TL;DR: In this article, a mathematical model for ammonia-water bubble absorbers was developed and compared with experimental data using a plate heat exchanger, and the analysis was performed carrying out a sensitive study of selected operation parameters on the absorber thermal load and mass absorption flux.
37 citations
TL;DR: In this paper, the development of bubble absorption refrigeration technologies is discussed from the aspects of driving energies, performance enhancement and application extension, and methods of enhancing bubble absorption performance were researched, and also the influence mechanisms of these physical and chemical methods were explained.
Abstract: This study reviews the developments of bubble absorption refrigeration technologies. Firstly, the principles of the bubble absorption refrigeration systems as well as bubble absorbers were introduced; And then bubble behavior characteristics during the absorption process were observed and expressed graphically; Thirdly, available bubble absorbers were investigated, modeled and compared; In addition, current and potential refrigerant-absorbent pairs in the bubble absorption refrigeration systems were analyzed, and about fifty fluids were involved totally. What’s more, methods of enhancing bubble absorption performance were researched, and also the influence mechanisms of these physical and chemical methods were explained; Finally, the development of bubble absorption refrigeration technologies were discussed from the aspects of driving energies, performance enhancement and application extension. The tendency of bubble absorption refrigeration technologies is expected to be high efficiency, miniaturization, and intellectualization. The expressed contents in this paper are expected to be useful for readers in the fields of absorption refrigeration technologies and the medium-low grade heat utilization technologies, especially for the equipment operating in the unsteady conditions (e.g. swing, bump, jolt, scram, etc.).
36 citations