Conjugate heat and mass transfer in a total heat exchanger with cross-corrugated triangular ducts and one-step made asymmetric membranes

2015 ◽  
Vol 84 ◽  
pp. 390-400 ◽  
Author(s):  
Zhen-Xing Li ◽  
Ting-Shu Zhong ◽  
Jian-Lei Niu ◽  
Fu Xiao ◽  
Li-Zhi Zhang
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Total Heat ◽  
Asymmetric Membranes ◽  
One Step

Overall Efficiency of a Radial Fin Assembly Under Dehumidifying Conditions

1998 ◽  
Vol 120 (4) ◽  
pp. 299-304 ◽  
Author(s):  
L. Rosario ◽  
M. M. Rahman
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Relative Humidity ◽  
Heat And Mass Transfer ◽  
Heat Transfer Rate ◽  
Transfer Process ◽  
Transfer Rate ◽  
Total Heat ◽  
Overall Efficiency

The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing the heat transfer rate with and without fins under the same operating conditions. Calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. An analysis of the overall efficiency for the assembly was also done. Results were compared to those under dry conditions, wherever appropriate. Comparison between present results and those published for rectangular as well as radial fins under fully wet conditions were made. These comparisons established the validity of the present model. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature. The fin efficiency decreased with relative humidity.

CFD-based structure optimization of plate bundle in plate-fin heat exchanger considering flow and heat transfer performance

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yao Li ◽  
Haiqing Si ◽  
Jingxuan Qiu ◽  
Yingying Shen ◽  
Peihong Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Field Performance ◽  
High Specific Surface Area ◽  
Calculation Model ◽  
Air Separation ◽  
Transfer Efficiency ◽  
Heat Transfer Efficiency

Abstract The plate-fin heat exchanger has been widely applied in the field of air separation and aerospace due to its high specific surface area of heat transfer. However, the low heat transfer efficiency of its plate bundles has also attracted more attention. It is of great significance to optimize the structure of plate-fin heat exchanger to improve its heat transfer efficiency. The plate bundle was studied by combining numerical simulation with experiment. Firstly, according to the heat and mass transfer theory, the plate bundle calculation model of plate-fin heat exchanger was established, and the accuracy of the UDF (User-Defined Functions) for describing the mass and heat transfer was verified. Then, the influences of fin structure parameters on the heat and mass transfer characteristics of channel were discussed, including the height, spacing, thickness and length of fins. Finally the influence of various factors on the flow field performance under different flow states was integrated to complete the optimal design of the plate bundle.

scholarly journals Influence of Frost Growth and Migration in Cryogenic Heat Exchanger on Air Refrigerator

2019 ◽  
Vol 9 (4) ◽  
pp. 753 ◽  
Author(s):  
Shanju Yang ◽  
Zhan Liu ◽  
Bao Fu ◽  
Yu Chen
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Numerical Model ◽  
Heat And Mass Transfer ◽  
Frost Formation ◽  
Transient Model ◽  
Transfer Rates ◽  
Low Humidity ◽  
And Migration ◽  
Frost Layer

Frost formation degrades the performance of heat exchangers greatly, thus influencing the cryogenic refrigerator. Different from frost formation on the evaporator surface, the growth and migration of frost layer inside the heat exchanger is of low temperature and humidity. In addition to the constantly changing boundary conditions, the effective prediction is difficult. In the present study, a numerical model was proposed to analyze the frost formation in the cryogenic heat exchanger of a reverse Brayton air refrigerator. Under small amounts of moisture, the growing of frost layer was simulated through the numerical heat and mass transfer by adopting semiempirical correlations. The frost formation model was inserted into the transient model of refrigerator, and numerical calculations were performed on heat and mass transfer rates, and growth and migration of frost layers in forced convection conditions. Experiments were conducted under different air humidity to investigate the frost formation and verify the numerical model. Through the model, the influences of frosting on the refrigerator were evaluated under different moisture contents and running time. It can be used to predict the performance of air refrigerators with low humidity and provide a basis for improving the system operation and efficiency.

Heat and Mass Transfer Analysis of a Pot-in-Pot Refrigerator Using Reynolds Flow Model

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
Ramendra Pandey ◽  
Bala Pesala
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Ambient Temperature ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
Radiation Heat Transfer ◽  
Ambient Air ◽  
Total Heat ◽  
Maximum Efficiency ◽  
Radiation Heat

Heat and mass transfer analysis of evaporative cooling process in a pot-in-pot cooling system is done based on Reynolds flow hypotheses. The model proposed herein assumes that the heat transfer due to natural convection is coupled with an imaginary ambient air mass flow rate (gAo) which is an essential assumption in order to arrive at the solution for the rate of water evaporation. Effect of several parameters on the pot-in-pot system performance has been studied. The equations are iteratively solved and detailed results are presented to evaluate the cooling performance with respect to various parameters: ambient temperature, relative humidity (RH), pot height, pot radius, total heat load, thermal and hydraulic conductivity, and radiation heat transfer. It was found that pot height, pot radius, total heat load, and radiation heat transfer play a critical role in the performance of the system. The model predicts that at an ambient temperature of 50 °C and RH of 40%, the system achieves a maximum efficiency of 73.44% resulting in a temperature difference of nearly 20 °C. Similarly, for a temperature of 30 °C and RH of 80%, the system efficiency was minimum at 14.79%, thereby verifying the usual concept that the pot-in-pot system is best suited for hot and dry ambient conditions.

A Fully Wet and Fully Dry Tiny Circular Fin Method for Heat and Mass Transfer Characteristics for Plain Fin-and-Tube Heat Exchangers Under Dehumidifying Conditions

2006 ◽  
Vol 129 (9) ◽  
pp. 1256-1267 ◽  
Author(s):  
Worachest Pirompugd ◽  
Chi-Chuan Wang ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Characteristic ◽  
Transfer Characteristic ◽  
Tube Heat Exchanger ◽  
Mass Transfer Characteristic ◽  
Transfer Characteristics

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.

Combined heat and mass transfer analysis during the dehumidification process within a plate type heat exchanger

2013 ◽  
Vol 27 (6) ◽  
pp. 1875-1880 ◽  
Author(s):  
Yong Sun Cho ◽  
Seon Chang Kim ◽  
Young Lyoul Kim ◽  
Yong Tae Kang
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Plate Type
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