Dehumidification: On the Correlation of Wet and Dry Transport Processes in Plate Finned-Tube Heat Exchangers

Abstract

The transverse velocity of the condensing phase during dehumidification is analogous to the transverse velocity at the wall when exercising boundary layer control by fluid extraction through a permeable wall. Wet and dry pressure drop and heat transfer rates are analyzed for correlation using boundary layer suction theory. Data are presented for flat-plate finned-tube heat exchangers during air heating and dehumidification operations and the data show a significant effect of transverse velocity correlated by the boundary layer suction formulation. The condensate film is considered isothermal in this analysis and the results indicate that an improved modeling of the condensate film is required. We find that the transverse velocity of the condensing phase has an important effect on transport phenomena during dehumidification and that the validity of the Chilton–Colburn heat and mass transfer analogy in describing dehumidification is supported by these results. It should be noted that the dry data form the beginning of a plate fin heat exchanger data base. The present data show the effect of tube diameter and, independently, fin density variation on the Colburn and friction factors with all other geometric parameters held invariant.

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

“…Equation (11) has been confirmed experimentally for dehumidification of air by Eckels and Rabas [28].…”

“…This suction causes a velocity normal to the surface, the major source for the difference between dry and wet surface heat transfer coefficients [26][27][28]. The effect on heat transfer is taken into account by the Ackermann correction [29], which is also known as the stagnant film model of heat transfer at high mass transfer rates [30].…”

Plate Fin and Tube Heat Exchanger Modeling: Effects of Performance Parameters for Turbulent Flow Regime

“…Several authors (Choi, 2010;Goldstein Jr, 1976;Lu et al, 2011;Pongsoi, Pikulkajorn, Wang, & Wongwises, 2012) have investigated the effects of the number of tube rows on staggered plate finned tube heat exchangers. Several correlations have been proposed to the effects of heat transfer and pressure drop on the performance of heat exchangers for plain fin geometry which gave predictive ability for the plain fin heat exchangers having larger tube diameter, larger longitudinal and transverse tube pitch (Eckels & Rabas, 1987;Junqi, Jiangping, Zhijiu, Yimin, & Wenfeng, 2007;Kayansayan, 1993;Şahin, Akkoca, Öztürk, & Akilli, 2006;Yuan, 2000;Zhang, He, & Tao, 2009) proposed correlations for heat transfer and friction characteristics for several geometric parameters in the thermal and hydraulic performance of a number of plain-fin heat exchangers. A number of studies (Eckels & Rabas, 1987;Syam Sundar, Sharma, & Parveen, 2009) have been conducted into the effect of fin spacing in the performance of fin tube heat exchangers provided test results for the investigation of the effect of fin spacing and fin length.…”

“…Several correlations have been proposed to the effects of heat transfer and pressure drop on the performance of heat exchangers for plain fin geometry which gave predictive ability for the plain fin heat exchangers having larger tube diameter, larger longitudinal and transverse tube pitch (Eckels & Rabas, 1987;Junqi, Jiangping, Zhijiu, Yimin, & Wenfeng, 2007;Kayansayan, 1993;Şahin, Akkoca, Öztürk, & Akilli, 2006;Yuan, 2000;Zhang, He, & Tao, 2009) proposed correlations for heat transfer and friction characteristics for several geometric parameters in the thermal and hydraulic performance of a number of plain-fin heat exchangers. A number of studies (Eckels & Rabas, 1987;Syam Sundar, Sharma, & Parveen, 2009) have been conducted into the effect of fin spacing in the performance of fin tube heat exchangers provided test results for the investigation of the effect of fin spacing and fin length. Numerous studies have measured the heat transfer coefficient and pressure drop over an eight tube row in-lined tube array (Eckels & Rabas, 1987;Kundu, Haji-Sheikh, & Lou, 1991;Launder & Massey, 1978;Şahin et al, 2006;Tang, Min, Xie, & Wang, 2009) .…”

The Behavior of Lewis Number in Finned Tube Cooling Coils under Highly Moist Inlet Air Conditions

“…For example, Kusuda (1963) proposed the Lewis number (Le) of the moist air, saturate surface temperature range of 10-60°C was the range of 0.870.90. Seshimo et al (1988) reported the value Lewis number at 1.1 and Eckels and Rabas (1987) gave values of Lewis number between 1.11.2; in addition, Hong and Webb (1996) showed values in the range of 0.71.1. Moreover, Wang and Chang (1998) also tested the cooling coil and presented the correlation of the Lewis number (Le), but the correlation did not include the effect of relative humidity.…”