Experiments and modeling of bubble column dehumidifier performance

Tow, Emily W.; Lienhard, John H.

doi:10.1016/j.ijthermalsci.2014.01.018

Cited by 59 publications

(37 citation statements)

References 30 publications

(57 reference statements)

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“…Recent studies by Tow and Lienhard [8][9][10] resulted in an accurate model of bubble columns that was experimentally validated. The model is used in this study, and is discussed in greater detail in Section 2.1.…”

Section: Bubble Column Dehumidifiers In Hdhmentioning

confidence: 99%

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Thermodynamic balancing of a fixed-size two-stage humidification dehumidification desalination system

Chehayeb

Narayan²,

Zubair

et al. 2015

Desalination

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Humidification dehumidification (HDH) is a desalination technology that has shown promise in small scale, decentralized applications. Previous studies on the multi-staging of HDH have used fixed-effectiveness models which do not explicitly account for transport processes in the components. However, to fully understand the effect of the variation of the mass flow rate ratio, it is necessary to implement heat and mass transfer models of the HDH system. In this paper, we model an HDH system consisting of a packed-bed humidifier and a multi-tray bubble column dehumidifier. We study the effect of the mass flow rate ratio on the performance of a fixed-size system, and we consider its effect on the entropy generation and the driving forces for heat and mass transfer. In addition, we define a generalized energy effectiveness for heat and mass exchangers. We also implement an air extraction/injection and simulate a wide range of operating conditions. We define criteria for the best system performance, and we study the effect of the distribution of available area between separate stages. We also present a thorough explanation of why the direction of extraction should always be from the humidifier to the dehumidifier.

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Section: Bubble Column Dehumidifiers In Hdhmentioning

confidence: 99%

“…The details of the solution methods used can be found in Chehayeb et al [13,27] and will not be presented in this section. It is worth noting that each of these models was validated experimentally in previous studies [8,28].…”

Section: Modelingmentioning

confidence: 99%

Thermodynamic balancing of a fixed-size two-stage humidification dehumidification desalination system

Chehayeb

Narayan²,

Zubair

et al. 2015

Desalination

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“…In traditional dehumidification systems, water vapor has to diffuse through an air layer, which increases the resistance to the mass transfer. In a bubble column, the location of condensation is the transiently formed bubble-water interface which has a very large specific area, giving it superior efficiency compared to alternative dehumidification systems [6,7].…”

Section: Bubble Column Dehumidifiermentioning

confidence: 99%

“…This study uses the model established by Tow and Lienhard [7][8][9] to evaluate the performance of the dehumidifier bubble column. This model is based on a resistance network between the hot air and cold saline water.…”

Section: Governing Equationsmentioning

confidence: 99%

“…This means that, even at infinite coil length, the saline water will only reach the air outlet temperature. Tow discusses this phenomenon in detail before defining a parallel flow effectiveness as the appropriate performance metric [7]. However, the height of a single-tray bubble column can be made very small, and multiple trays, each at a different temperature, can be stacked to form a multi-tray bubble column which is no longer limited to the performance of a parallel flow device, as shown in Fig.…”

Section: Multi-tray Bubble Column Dehumidifiermentioning

confidence: 99%

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A Numerical Solution Algorithm for a Heat and Mass Transfer Model of a Desalination System Based on Packed-Bed Humidification and Bubble Column dehumidification

Chehayeb

Cheaib

Lienhard

2014

Proceedings of the 15th International Heat Transfer Conference

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The humidification-dehumidification (HDH) desalination system can be advantageous in small-scale, off-grid applications. The main drawback of this technology has been its low energy efficiency, which results in high water production costs. Previous studies have approached this issue through thermodynamic balancing of the system; however, most theoretical work on the balancing of HDH has followed a fixed-effectiveness approach that does not explicitly consider transport processes in the components. Fixing the effectiveness of the heat and mass exchangers allows them to be modeled without explicitly sizing the components and gives insight on how the cycle design can be improved. However, linking the findings of fixed-effectiveness models to actual systems can be challenging, as the performance of the components depends mainly on the available surface areas and the flow rates of the air and water streams. In this study, we present a robust numerical solution algorithm for a heat and mass tranfer model of a complete humidification-dehumidification system consisting of a packed-bed humidifier and a multi-tray bubble column dehumidifier. We look at the effect of varying the water-to-air mass flow rate ratio on the energy efficiency of the system, and we compare the results to those reached following a fixed-effectiveness approach. In addition, we study the effect of the top and bottom temperatures on the performance of the system. We recommended the implementation a control system that varies the mass flow rate ratio in order to keep the system balanced in off-design conditions, especially with varying top temperature.

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Humidification Dehumidification Desalination

Lienhard

2014

Desalination

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Humidification-dehumidification (HDH) desalination involves vaporizing water from a saline liquid stream into a carrier gas stream and then condensing the vapor to form purified water. This chapter describes various forms of the HDH cycle, with analysis of the energy consumption of various realizations of the process. The use of mass extraction/injection to improve performance is discussed. Analyses using both fixed component effectiveness and fixed component size are considered. Bubble column dehumidifiers are described, and the effect of very high feed salinity on energy and efficiency is discussed.

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Experiments and modeling of bubble column dehumidifier performance

Cited by 59 publications

References 30 publications

Thermodynamic balancing of a fixed-size two-stage humidification dehumidification desalination system

Thermodynamic balancing of a fixed-size two-stage humidification dehumidification desalination system

A Numerical Solution Algorithm for a Heat and Mass Transfer Model of a Desalination System Based on Packed-Bed Humidification and Bubble Column dehumidification

Humidification Dehumidification Desalination

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