EXPERIMENTAL STUDY ON DROPWISE CONDENSATION - EFFECT OF MAXIMUM DROP SIZE UPON THE HEAT TRANSFER COEFFICIENT

1978 ◽  
Author(s):  
Ichiro Tanasawa ◽  
J. Ochiai ◽  
Y. Funawatashi
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Drop Size ◽  
Dropwise Condensation ◽  
Condensation Effect ◽  
The Heat Transfer Coefficient

Experimental Study and Visualization of Dropwise Condensation on SUS316 Surface Under Non-Condensable Gas Condition

2016 ◽  
Author(s):  
Jae Young Choi ◽  
Yong Hoon Jeong ◽  
Noriyuki Watanabe
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Surface Coating ◽  
Drop Size ◽  
Dropwise Condensation ◽  
Light Water ◽  
Cooling Surface ◽  
The Heat Transfer Coefficient

The passive safety features of nuclear power plant against station blackout (SBO) and intact containment integrity are the main key issues after Fukushima accident. As a corresponding safety system, passive containment cooling system (PCCS) received attention as one of the candidate systems applying to advanced light water reactors. Next generation of light water reactor, AP-1000 and ESBWR have suggested their own PCCS design. However, PCCS have difficulty in its heat exchanger volume due to low heat transfer coefficient of condensation under the presence of non-condensable gas condition. Several attempts had been studied worldwide to enhance the heat transfer coefficient of PCCS and this paper focused on dropwise condensation, which has much higher heat transfer coefficient than those found with filmwise condensation. Historically, surface coating or applying organic promoter on the cooling surface were typically used to induce dropwise condensation, but those method had disadvantage of their duration time. In general, surface coating and organic promoter were considered to have few years and few days of their duration, respectively. Therefore, an aim of our experiment was to determine whether SUS316 without any surface treatment is able to utilize dropwise condensation for PCCS heat exchanger. Following studies were compared to the filmwise condensation on SUS316 with same condition and also the experiment results reported by other researchers. The overall results determined how much the heat transfer coefficient was enhanced. To analyze the behavior of dropwise condensation, visualized images of cooling surface with droplets were graphically processed. All experiments were conducted on 13mm diameter of vertical-oriented flat surface with 6mm thickness. Air concentration (non-condensable concentration) was estimated by the partial pressure ratio of steam and air. Subcooled temperature, the difference between steam saturated temperature and surface temperature, was tested from 1 to 30 degree Celsius. High-speed camera visualized the condensate on the cooling surface with several magnification and frame speed. All measurement was measured after the whole system reached to equilibrium state and sustained it more than 30 minutes. Each data was recorded for 60 seconds and time-averaged its measurement. Experiment results indicated that SUS316 surface without any surface treatment could sustain dropwise condensation phase over 12 hours of experiment under low subcooled temperature below approximately 20 degree Celsius. Also, dropwise condensation had around 3 to 4 times enhanced heat transfer coefficients than those of filmwise condensation. The result of dropwise condensation with pure steam condition was well proportional to the power of subcooled temperature. Otherwise, the result with non-condensable gas showed heat transfer coefficient, shaded in high uncertainty of systematic error, seems to be decreased in low subcooled temperature under 5 degree Celsius. Higher sensitivity of non-condensable concentration upon heat transfer coefficient was observed on dropwise condensation more than filmwise condensation. The variation of drop-size distribution with the periodic time passage after surface sweeping was observed and patterns of drop-size distribution were repeated after the surface sweeping regardless of experimental conditions. The study provides feasibility and benefit of the utilization of dropwise condensation to PCCS heat exchanger if the system has designed to be operated within low subcooled temperature.

A Theoretical Study of Dropwise Condensation

1975 ◽  
Vol 97 (1) ◽  
pp. 72-78 ◽  
Author(s):  
Hiroaki Tanaka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Size Distribution ◽  
General Expression ◽  
Drop Size ◽  
Theoretical Study ◽  
Dropwise Condensation ◽  
Fundamental Equations ◽  
The Heat Transfer Coefficient

The so-called steady dropwise condensation consists of the transient dropwise condensation occurring repeatedly from place to place on the tracks of departing drops. By taking statistical and geometrical conditions into account, the author derives fundamental equations describing the process of this transient dropwise condensation. By solving these equations, the existence of a universal drop-size distribution is predicted. Further, by introducing a model for the cycle of drop departure, a general expression for the heat-transfer coefficient under the so-called steady dropwise condensation is obtained.

Effect of Open Micro-Channels on External Condensation Heat Transfer

2016 ◽  
Author(s):  
Brandon Hulet ◽  
Andres Martinez ◽  
Melanie Derby ◽  
Amy Rachel Betz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Thickness ◽  
Transfer Coefficient ◽  
Heat Fluxes ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Micro Channels ◽  
Lower Heat ◽  
The Heat Transfer Coefficient

This research experimentally investigates the heat transfer performance of open-micro channels under filmwise condensation conditions. Filmwise condensation is an important factor in the design of steam condensers used in thermoelectric power generation, desalination, and other industrial applications. Filmwise condensation averages five times lower heat transfer coefficients than those present in dropwise condensation, and filmwise condensation is the dominant condensation regime in the steam condensers due to a lack of a durable dropwise condensation surface. Film thickness is also of concern because it is directly proportional to the condenser’s overall thermal resistance. This research focuses on optimizing the channel size to inhibit the creation of a water film and/or to reduce its overall thickness in order to maximize the heat transfer coefficient of the surface. Condensation heat transfer was measured in three square channels and a plane surface as a control. The sizes of the square fins were 0.25 mm; 0.5 mm; and 1 mm, and tests were done at a constant pressure of 6.2 kPa. At lower heat fluxes, the 0.25mm fins perform better, whereas at larger heat fluxes a smooth surface offers better performance. At lower heat fluxes, droplets are swept away by gravity before the channels are flooded. Whereas, at higher heat fluxes, the channels are flooded increasing the total film thickness, thereby reducing the heat transfer coefficient.

Experimental Study on Integrated Performance for Flower Baffle Heat Exchanger’s Distance between Two Flower Baffles

2010 ◽  
Vol 29-32 ◽  
pp. 132-137 ◽  
Author(s):  
Xue Jiang Lai ◽  
Rui Li ◽  
Yong Dai ◽  
Su Yi Huang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
The One ◽  
Integrated Performance ◽  
Quantity Of Heat ◽  
Side Flow ◽  
The Heat Transfer Coefficient

Flower baffle heat exchanger’s structure and design idea is introduced. Flower baffle heat exchanger has unique support structure. It can both enhance the efficiency of the heat transfer and reduce the pressure drop. Through the experimental study, under the same shell side flow, the heat transfer coefficient K which the distance between two flower baffles is 134mm is higher 3%~9% than the one of which the distances between two flower baffles are 163mm,123mm. The heat transfer coefficient K which the distance between two flower baffles is 147mm is close to the one of which the distances between two flower baffles is 134mm. The shell volume flow V is higher, the incremental quantity of heat transfer coefficient K is more. The integrated performance K/Δp of flower baffle heat exchanger which the distance between two flower baffles is 134mm is higher 3%~9% than the one of which the distances between two flower baffles are 163mm,123mm. Therefore, the best distance between two flower baffles exists between 134mm~147mm this experiment.

Performance Experimental Study and Energy Consumption Calculation of Hollow Glass Window Film

2011 ◽  
Vol 250-253 ◽  
pp. 356-359
Author(s):  
Dan Ping Yang ◽  
Jia Peng He ◽  
Zheng Song Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Energy Consumption ◽  
Transfer Coefficient ◽  
Window Glass ◽  
Hollow Glass ◽  
Window Film ◽  
The Heat Transfer Coefficient ◽  
Energy Consumption Calculation

This paper taked hollow glass window as the model, and heat transfer coefficient, sunshading coefficient and energy consumption of the window glass were obtained in the situations of window glass with and without low-E film by doing experiment and theoretical calculation. The results show that both heat transfer coefficient and sunshading coefficient decrease comparing the hollow glass window film with no film. For the fixed and push-pull window of the whole window, the heat transfer coefficient decrease by 24.2% and 28.9% respectively and sunshade coefficient decreases by 31.37%. And the low-E film by this study adopting reduces energy consumption of the summer greatly by 32.96%, and has no too large effect on winter heating, so the annual energy consumption reduces and the window film saves annual energy consumption 14.62% .

Experimental study of the heat transfer coefficient and pressure drop of R1234yf condensing flow in flattened smooth tubes

2019 ◽  
Vol 106 ◽  
pp. 120-132 ◽  
Author(s):  
Hamidreza Fazelnia ◽  
Behrang Sajadi ◽  
Soorena Azarhazin ◽  
Mohammadali Akhavan Behabadi ◽  
Sajjad Zakeralhoseini
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Smooth Tubes ◽  
The Heat Transfer Coefficient

The Experimental Study on the Enhanced Evaporating Property of the Pineapple Juice by Ultrasound

2014 ◽  
Vol 494-495 ◽  
pp. 285-288
Author(s):  
Ji Tian Song ◽  
Xiao Fei Xu ◽  
Wei Tian ◽  
Jian Bo Liu ◽  
Zheng Zhao
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Feed Rate ◽  
Pineapple Juice ◽  
The Heat Transfer Coefficient

In this paper, the heat transfer of pineapple juice was investigated on a new evaporator with ultrasound. The effects of various factors on the heat transfer coefficient were analyzed, including feed rate, evaporating temperature, temperature difference of heat transfer, and juice concentration. The proposals of design and operation for this new evaporation were also discussed.

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