Ein neues Berechnungsverfahren für die Wärmeübertragung im Übergangsbereich zwischen laminarer und turbulenter Rohrströmung

“…with the air face velocity w 0 , where s is the fin spacing, d f the fin thickness and Local heat transfer coefficients in circular tubes [46,47] are applied on the saline water side. Heat transfer through the condensate film is described by Nusselt's condensation theory [28].…”

Section: Heat Transfer Equations For Plate-fin Tube Heat Exchangersmentioning

confidence: 99%

Design of Plate-Fin Tube Dehumidifiers for Humidification–Dehumidification Desalination Systems

Sievers

Lienhard

2014

Heat Transfer Engineering

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A two-dimensional numerical model of a plate-fin tube heat exchanger for use as a dehumidifier in a humidification-dehumidification (HDH) desalination systems is developed, because typical heating, ventilating, and air conditioning (HVAC) dehumidifier models and plate-fin tube dehumidifier geometries are not intended for the considerably higher temperature and humidity ratio differences which drive heat and mass transfer in HDH desalination applications. The experimentally validated model is used to investigate the influence of various heat exchanger design parameters. Potential improvements on common plate-fin tube dehumidifier designs are identified by examining various methods of optimizing tube diameter, and longitudinal and transverse tube spacing to achieve maximum heat flow for a given quantity of fin material at a typical HDH operating point. Thicker fins are recommended than for HVAC geometries, as the thermal conductive resistance of HVAC fins restricts dehumidifier performance under HDH operating conditions.

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“…The local heat transfer correlations at position z for constant wall temperature from Gnielinski [40][41][42][43], Table 1, are used with the thermophysical properties at the arithmetic mean fluid temperature between cell inlet and outlet. The critical Reynolds number ranges from 2200 to 3600 [42], depending on the inlet conditions.…”

Section: Heat Transfer Correlationsmentioning

confidence: 99%

“…Re crit = 2300 is selected, following Gnielinski [42]. For the transition region a 13 linear interpolation between the local Nusselt number for laminar flow at Re = 2300 and the local Nusselt number for turbulent flow at Re = 10 4 is applied [43].…”

Section: Heat Transfer Correlationsmentioning

confidence: 99%

Design of Flat-Plate Dehumidifiers for Humidification–Dehumidification Desalination Systems

Sievers

Lienhard

2013

Heat Transfer Engineering

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Flat-plate heat exchangers are examined for use as dehumidifiers in humidification-dehumidification (HDH) desalination systems. The temperature and humidity ratio differences that drive mass transfer are considerably higher than in airconditioning systems, making current air-conditioning dehumidifier designs and design software ill-suited to HDH desalination applications. In this work a numerical dehumidifier model is developed and validated against experimental data. The model uses a logarithmic mass transfer driving force and an accurate Lewis number. The heat exchanger is subdivided into many cells for high accuracy. The Ackermann correction takes into account the effect of non-condensable gases on heat transfer during condensation. The influence of various heat exchanger design parameters is thoroughly investigated and suitable geometries are identified. Amongst others, the relationship between heat flow, pressure drop and heat transfer area is shown. The thermal resistance of the condensate layer is negligible for the investigated geometries and operating point.A particle embedded polymer as a flat-plate heat exchanger material for seawater operation substantially improves the heat flux relative to pure polymers and approaches the performance of titanium alloys. Thus, the use of particle embedded polymers is recommended. The dehumidifier model can be applied in design and optimization of HDH desalination systems.

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Ein neues Berechnungsverfahren für die Wärmeübertragung im Übergangsbereich zwischen laminarer und turbulenter Rohrströmung

Cited by 127 publications

References 3 publications

Molten Salt Heat Transport Loop: Materials Corrosion and Heat Transfer Phenomena

Molten Salt Heat Transport Loop: Materials Corrosion and Heat Transfer Phenomena

Design of Plate-Fin Tube Dehumidifiers for Humidification–Dehumidification Desalination Systems

Design of Flat-Plate Dehumidifiers for Humidification–Dehumidification Desalination Systems

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