Heat and Mass Transfer Characteristics for Finned Tube Heat Exchangers with Humidification

This study proposes a new method, namely the “fully wet and fully dry tiny circular fin method,” for analyzing the heat and mass transfer characteristics of plain fin-and-tube heat exchangers under dehumidifying conditions. The present method is developed from the tube-by-tube method proposed in the previous study by the same authors. The analysis of the fin-and-tube heat exchangers is carried out by dividing the heat exchanger into many tiny segments. A tiny segment will be assumed with fully wet or fully dry conditions. This method is capable of handling the plain fin-and-tube heat exchanger under fully wet and partially wet conditions. The heat and mass transfer characteristics are presented in dimensionless terms. The ratio of the heat transfer characteristic to mass transfer characteristic is also studied. Based on the reduced results, it is found that the heat transfer and mass transfer characteristics are insensitive to changes in fin spacing. The influence of the inlet relative humidity on the heat transfer characteristic is rather small. For one and two row configurations, a considerable increase of the mass transfer characteristic is encountered when partially wet conditions take place. The heat transfer characteristic is about the same in fully wet and partially wet conditions provided that the number of tube rows is equal to or greater than four. Correlations are proposed to describe the heat and mass characteristics for the present plain fin configuration.

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Finite circular fin method for heat and mass transfer characteristics for plain fin-and-tube heat exchangers under fully and partially wet surface conditions

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2006.07.017 ◽

2007 ◽

Vol 50 (3-4) ◽

pp. 552-565 ◽

Cited By ~ 34

Author(s):

Worachest Pirompugd ◽

Chi-Chuan Wang ◽

Somchai Wongwises

Keyword(s):

Mass Transfer ◽

Heat And Mass Transfer ◽

Heat Exchangers ◽

Surface Conditions ◽

Transfer Characteristics ◽

Wet Surface

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Heat and Mass Transfer Characteristics of a Finned-Tube Evaporator Under Frosting Conditions

10.1115/imece2001/pid-25612 ◽

2001 ◽

Author(s):

Y. H. Kim ◽

Y. J. Park ◽

Y. C. Kim ◽

S. C. Shim ◽

S. K. Oh ◽

...

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Heat And Mass Transfer ◽

Air Temperature ◽

Early Stage ◽

Finned Tube ◽

Airflow Rate ◽

Air Velocity ◽

Frost Formation ◽

Transfer Characteristics

Abstract An experimental study was performed to investigate the heat and mass transfer characteristics of a finned-tube evaporator coil utilized in a domestic refrigerator under frosting conditions. Airside heat transfer coefficient was measured as a function of air temperature, humidity ratio, air velocity, and evaporating temperature. In addition, frost thickness was monitored and measured by visualization tests during frosting operation. Based on the experimental results, the degradation of heat transfer performance due to frost formation was explored as a function of operating parameters. The rate of frost formation on the evaporator increases at relatively high humidity, high airflow rate, low inlet air temperature and low refrigerant temperature. As the frost thickness increases, airflow rate gradually decreases, while the capacity increases at the early stage of frost formation and then significantly drops.

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Simultaneous heat and mass transfer characteristics for wavy fin-and-tube heat exchangers under dehumidifying conditions

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2005.05.043 ◽

2006 ◽

Vol 49 (1-2) ◽

pp. 132-143 ◽

Cited By ~ 53

Author(s):

Worachest Pirompugd ◽

Somchai Wongwises ◽

Chi-Chuan Wang

Keyword(s):

Mass Transfer ◽

Heat And Mass Transfer ◽

Heat Exchangers ◽

Transfer Characteristics ◽

Simultaneous Heat

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The New Mathematical Models for Plain Fin-and-Tube Heat Exchangers With Dehumidification

Journal of Heat Transfer ◽

10.1115/1.4029037 ◽

2015 ◽

Vol 137 (3) ◽

Cited By ~ 1

Author(s):

Worachest Pirompugd ◽

Chi-Chuan Wang ◽

Somchai Wongwises

Keyword(s):

Mass Transfer ◽

Heat And Mass Transfer ◽

Heat Exchangers ◽

Heat Transfer Performance ◽

Transfer Performance ◽

Fin Efficiency ◽

Tube Heat Exchanger ◽

Model Based ◽

Transfer Characteristics ◽

Wet Condition

For evaluating performance of fin-and-tube heat exchangers under dehumidifying conditions, the recent lumped approach models are based on the enthalpy potential or equivalent dry bulb temperature. This study proposes a new lumped approach model based on the dry bulb temperature difference. The concept of dry bulb temperature was first presented by McQuiston for derivation of fin efficiency under dehumidifying conditions in 1975. This concept is simpler than the concepts of enthalpy potential and equivalent dry bulb temperature. Nevertheless, it cannot be found that this concept is applied to the fin-and-tube heat exchangers. Moreover, this study also presents the finite circular fin method (FCFM) based on the dry bulb temperature and equivalent dry bulb temperature. The FCFM was first presented in our published literature but it was based on the enthalpy potential. The FCFM is done by dividing the fin-and-tube heat exchanger into many small segments. Then, the segments are divided into three cases: fully dry condition, fully wet condition, and partially wet condition. From the results, the new lumped approach model based on dry bulb temperature gives a good result. It is the simplest method for evaluating heat transfer performance of fin-and-tube heat exchangers under fully wet conditions. For the FCFM, the heat and mass transfer characteristics obtained by dry bulb temperature and equivalent dry bulb temperature are nearly the same as those obtained by the enthalpy potential. However, the heat and mass transfer characteristics by the FCFM based on equivalent dry bulb temperature are higher than those obtained by the FCFM based on dry bulb temperature. This is because of the effect of the nonconstant term in the two methods. The correlations applicable for both fully wet and partially wet conditions for the FCFMs based on equivalent dry bulb temperature and dry bulb temperature are proposed to describe the heat and mass transfer characteristics for the present plain fin configuration.

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