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This article presents two mathematical models for estimating the performances of finned tube heat exchangers with wavy configuration under partly and fully wet surface conditions. The actual dry bulb temperature method is the first one and the other is the method of equivalent dry bulb temperature. For the first one, the actual dry bulb temperature method that was firstly presented by our research team in 2015 is more uncomplicated than the well-known enthalpy potential method and is also easier than the equivalent dry bulb temperature method. Moreover, it has never been applicable to the finned tube heat exchanger. For accuracy, the finned tube heat exchangers are distinguished into teeny segments and every segments are separated by conditions of surface into three groups: partially wet segments, fully wet segments, fully dry segments. This procedure is called the finite circular fin method that was firstly presented by our research in 2007. From the results, the heat and mass transfer characteristics estimated by the method of equivalent dry bulb temperature are greater than those estimated by the method of actual dry bulb temperature. This is the influence of the non-constant terms in both methods. Moreover, the correlations for the conditions of party and fully wet surface are revealed for predicting the heat and mass transfer coefficients of the finned tube heat exchanger with wavy configuration. The users can apply our presented models with the proposed correlation for predicting the heat and mass transfer performances of finned tube heat exchangers with wavy configuration under the conditions of fully and partly wet surface. [ABSTRACT FROM AUTHOR]

Abstract: Correlations are proposed for the wet surface ratio of a fin-and-tube heat exchanger with plain and wavy fin geometry under dehumidifying conditions. The ‘Finite Circular Fin Method’ (FCFM) is used for data reduction. It is found that the percentage of wet surface area increases with increasing fin spacing or number of tube rows and decreasing Reynolds number. Despite the addition of tube rows or reduced fin spacing the effective surface area is increased, and its influence on a partially wet surface is apparently the opposite. This is because adding tube rows will provide a more effective temperature drop in air flow than adding fins, Moreover, the heat and mass transfer characteristics of jh and jm increase with an increase in the area of wet surface. Correlations for prediction of the percentage of wet surface area are proposed. These correlations can describe 83.81% of the area of wet surface to within ±10%. [Copyright &y& Elsevier]

Abstract: This paper presents a review of data reduction method for heat and mass transfer characteristics of fin-and-tube heat exchangers with dehumidification. There are many reduction methods for fin-and-tube heat exchangers under dehumidifying conditions. The data reduction methods being reviewed includes the original Threlkeld method, direct method, the equivalent dry-bulb method, tube by tube method, the fully wet and fully dry tiny circular fin method, and the finite circular fin method. Among these methods, the original Threlkeld method, direct method, the equivalent dry-bulb method are lumped method while others can divide the fin-and-tube heat exchangers into small segments for more accuracy in handling the surfaces to be fully dry, fully wet, or partially wet. In addition, the mass transfer characteristics can be obtained from the modified process line equation incorporated with the preceding methods. It should be noted that the conventional assumption of constant ratio (hc,o /hd,oCp,a ≈constant) is actually incorrect. This present paper can be used as the first guideline for the researcher for reducing the experimental data for fin-and-tube heat exchangers under dehumidifying conditions. [Copyright &y& Elsevier]

Abstract: The present study proposes the finite circular fin method for analyzing the heat and mass transfer characteristics of wavy fin-and-tube heat exchangers under fully and partially wet surface conditions. The analysis is carried out by dividing the wavy fin-and-tube heat exchanger into many tiny segments. The tiny segments can be analyzed based on surface conditions, i.e. fully wet, fully dry or partially wet surface condition. From the experimental results, it is found that the heat and mass transfer characteristics are insensitive to the inlet relative humidity but the effect of relative humidity on mass transfer characteristic become more pronounced when the partially wet surface condition takes place. The heat transfer characteristic is independent of the fin spacing. Effect of fin spacing on mass transfer characteristic is small when fin spacing is larger than 2.5mm. However, at smaller fin spacing, the mass transfer characteristic slightly decreases when the relative humidity increases. The ratios of h c,o/h d,o C p,a are in the range of 0.6–1.2. Correlations are proposed to describe the heat and mass transfer characteristics. These correlations can describe 95.63% of the heat transfer characteristic within 15% and 95.14% of the mass transfer characteristic within 20%. Correspondingly, 94.68% of the ratios of h c,o/h d,o C p,a are predicted by the proposed correlation within 20%. [Copyright &y& Elsevier]

Abstract: This study proposes a new method, namely the “finite circular fin method” (FCFM), to analyze the performance of fin-and-tube heat exchangers having plain fin configuration under dehumidifying conditions. The analysis is done by dividing the heat exchanger into many tiny segments (number of tube rows×number of tube passes per row×number of fins). The tiny segments are distinguished into three types: the fully dry, partially wet or fully wet surface conditions. The proposed method is capable of handling fully and partially wet surfaces. From the test results, it is found that the sensible heat transfer performance and the mass transfer performance are insensitive to changes of fin pitch. The influence of inlet relative humidity on the sensible heat transfer performance is small, and is almost negligible when the number of tube rows is above four. For one and two row configurations, considerable increase of mass transfer performance is encountered when partially wet condition takes place. The sensible heat transfer coefficient is about the same for those in fully wet and partially wet conditions provided that the number of tube row is equal or greater than four. Correlations applicable for both fully wet and partially wet conditions are proposed to describe the heat and mass performance for the present plain fin configuration. [Copyright &y& Elsevier]

Abstract: The present study proposes a new reduction method to calculate the heat and mass transfer characteristics of the wavy fin-and-tube heat exchangers under dehumidifying conditions. For fully wet conditions, the sensible heat transfer and mass transfer characteristics are relatively insensitive to the inlet relative humidity. The heat and mass transfer performances show appreciable influence of fin spacing at 1-row configuration. Both the heat and mass transfer performances increase when the fin spacing is reduced. However, the difference becomes less noticeable when Re Dc >3000. For 1-row configuration, larger wave height shows much larger difference with the fin spacing. However, the effect of inlet conditions and geometrical parameters on the heat and mass performance becomes less significant with the rise of number of tube rows. Test results show that the heat and mass transfer analogy is roughly applicable (the ratios of h c,o/h d,o C p,a are in the range 0.6–1.1, and is insensitive to change of fin spacing). The correlations are proposed to describe the heat and mass transfer characteristics. These correlations can describe 94.19% of the j h factors within 15% and 83.72% of the j m factors within 15%. Correspondingly, 93.02% of the ratios of h c,o/h d,o C p,a are predicted by the proposed correlation within 15%. [Copyright &y& Elsevier]