Cicada-inspired self-cleaning superhydrophobic surfaces

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Junho Oh ◽  
Sabrina Yin ◽  
Catherine E. Dana ◽  
Sungmin Hong ◽  
Jessica K. Roman ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Air Conditioning ◽  
Microbial Growth ◽  
Heat Transfer Performance ◽  
Self Cleaning ◽  
Bacteria And Fungi ◽  
Wetting Heat ◽  
Droplet Condensation ◽  
Individual Particles ◽  
Living Creature

Abstract Water-based heat transfer surfaces in HVAC&R (Heating, Ventilation, Air Conditioning and Refrigeration) systems have biofouling or microbial growth which might not only impose adverse effects to public health but also deteriorate the heat transfer performance of surfaces. In nature, a living creature is surviving while being exposed to formidable condition such as bacteria and fungi. Cicada wing has known to have multi-functional wings exhibiting nonwetting, and anti-microbial due to nanoscale pillars and biochemicals to achieve non-wetting characteristics. We conducted experiments on cicada wings and cicada-inspired engineered superhydrophobic samples to show that droplets jumping from superhydrophobic wings could carry away individual particles (~100 µm) or cluster of particles. This study was investigated on self-cleaning mechanism using jumping droplet condensation and elucidate further antifouling characteristics of non-wetting heat transfer surfaces.

scholarly journals Research on Heat Transfer Performance of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center

2020 ◽  
Vol 10 (2) ◽  
pp. 583
Author(s):  
Liping Zeng ◽  
Xing Liu ◽  
Quan Zhang ◽  
Jun Yi ◽  
Xianglong Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Micro Channel ◽  
Filling Rate ◽  
Air Conditioning System

This paper deals with the heat transfer performance of a micro-channel backplane heat pipe air conditioning system. The optimal range of the filling rate of a micro-channel backplane heat pipe air conditioning system was determined in the range of 65–75%, almost free from the interference of working conditions. Then, the influence of temperature and air volume flow rate on the heat exchange system were studied. The system maximum heat exchange is 7000–8000 W, and the temperature difference between the inlet and outlet of the evaporator and the condenser is almost 0 °C. Under the optimum refrigerant filling rate, the heat transfer of the micro-channel heat pipe backplane system is approximately linear with the temperature difference between the inlet air temperature of the evaporator and the cooling distribution unit (CDU) inlet water temperature in the range of 18–28 °C. The last part compares the heat transfer characteristics of two refrigerants at different filling rates. The heat transfer, pressure, and refrigerant temperature of R134a and R22 are the same with the change of filling rate, but the heat transfer of R134a is lower than that of R22. The results are of great significance for the operational control and practical application of a backplane heat pipe system.

scholarly journals Numerical Simulation of Heat Transfer Tube Characteristics of Refrigeration and Air Conditioning Based on Mixed Fractional Model

2021 ◽  
Vol 2074 (1) ◽  
pp. 012069
Author(s):  
Weihua Ding ◽  
Wei Chen
Keyword(s):  
Heat Transfer ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Enhancement Effect ◽  
Transfer Performance ◽  
Water Flow Velocity ◽  
Heat Transfer Tube ◽  
Transfer Tube ◽  
Heat Transfer Capacity ◽  
Performance Of Heat Transfer

Abstract The main parameters affecting the heat transfer performance of heat transfer tube heat exchanges include fin shape, fin spacing, fin thickness, tube row arrangement, tube diameter, dry and wet bulb temperature and flow rate. The air side heat transfer performance of heat transfer tube heat exchange and the influence of velocity field and temperature field distribution on heat transfer effect have been the focus of domestic and foreign scholars. In this paper, based on the mixed fraction model, CFD software is used to simulate the absorption process of gravity falling film outside the heat transfer tubes of refrigeration and air conditioning, and to study the flow and heat transfer characteristics of the process. The results show that, for the heat transfer tubes with the selected structure, the heat transfer capacity increases with the increase of water flow velocity, and the heat transfer enhancement effect of turbulence is enhanced. The heat transfer tubes have better comprehensive heat transfer performance than smooth tubes with the same diameter.

Heat Transfer Performance During Condensation of R-134A

2008 ◽  
Author(s):  
M. H. Al-Hajeri ◽  
A. M. Koluib
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Relevant Literature ◽  
Analytical Data ◽  
Average Pressure ◽  
Helical Pipe ◽  
R 134A ◽  
Flow Flux

This paper reports experimental investigation of condensation heat transfer and pressure drop of an ozone friendly refrigerant, R-134a, inside a helical pipe for climatic conditioning of hot regions. This study concerns the condensation of R-134a flowing through annular helical pipes with different conditions of operating refrigerant-saturated temperatures. The average pressure drop was measured and compared with data from relevant literature. The measurements R-134a were performed on mass flow flux ranges from 50 to 680 kg/m2 s. The study provides experimental and analytical data which could be used for the design and development of more efficient condensers for refrigeration and air conditioning (A/C) systems working with the same refrigerant.

A Focus on the Literature Review of Nanorefrigerants

2014 ◽  
Author(s):  
Ahmet Selim Dalkılıç ◽  
Melih Aktaş ◽  
Ali Celen ◽  
Alican Çebi ◽  
Omid Mahian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Air Conditioning ◽  
Base Fluid ◽  
Heat Transfer Performance ◽  
Heat Pumps ◽  
Wide Range ◽  
The Common ◽  
Air Conditioning Systems ◽  
Passive Techniques

The heat transfer performance of various thermal devices can be augmented by active and passive techniques. One of the passive techniques is the addition of nanoparticles had the size of 1 and 100 nanometers to the common heat transfer so that the thermal transport properties of the prepared suspension called nanofluid will be enhanced compared to the base fluid. Nanorefrigerants as a special type of nanofluids which are mixtures of nanoparticles and refrigerants have a wide range of applications in diverse fields such as refrigeration, air conditioning systems and heat pumps. In this study, the missing points on this new method are also indicated regarding the lack of studies on the determination of physical properties of nanorefrigerants and the flow of nanoparticles.

Study on the Adjustment Law of Supply Water Temperature of the Fan Coil Unit Based on Daily Air-Conditioning Load

2011 ◽  
Vol 374-377 ◽  
pp. 538-542 ◽  
Author(s):  
Zhi Jie Gao ◽  
Zhi Wei Wang ◽  
Ji Feng Zhao
Keyword(s):  
Heat Transfer ◽  
Water Temperature ◽  
Heat Pump ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Residential Buildings ◽  
Transfer Performance ◽  
Pump Unit ◽  
Heat Pump Unit ◽  
Supply Water

A new adjustment law of supply water temperature of heat pump unit was presented by analyzing heat transfer performance and computing supply water temperature of fan coil unit (FCU) in this paper. The paper established the energy equations for air side, water side and FCU in dry and wet conditions, respectively. And the heat transfer performance of FCU was obtained by analyzing the manufacturers’ performance data. According to an actual central air-conditioning system of residential buildings, we calculated the daily inlet water temperature of FCU and proposed the adjustment law for supply water temperature. The results show that the supply water temperature of cooling design day is 9.3°C, the daily supply water temperature of cooling season is higher than 7°C; the supply water temperature of heating design day is 36.4°C, the highest in heating season is 38.5°C, which is below the rated supply water temperature of heat pump unit, 45°C.

Research on Wet Thermal Recovery Plant Used by Air Conditioning

2012 ◽  
Vol 424-425 ◽  
pp. 1155-1158
Author(s):  
Yong An Li ◽  
Xue Lai Liu ◽  
Jia Jia Yan ◽  
Teng Xing
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Three Dimensional ◽  
Transfer Characteristic ◽  
Thermal Recovery ◽  
Transfer Performance ◽  
Recovery Plant ◽  
Air Channels

Based on the simulation Computational Fluid Dynamics method, in view of air conditioning with wet thermal recovery plant for heat and mass transfer characteristic, establishes air channels in three-dimensional laminar flow and heat transfer, mass transfer coupling process of mathematical physics model, discusses the air conditioning with wet thermal recovery plant air channels in temperature, concentration and pressure parameters such as distribution, application enthalpy efficiency analysis method to the heat transfer performance is evaluated. The results indicate that structure parameters of wet thermal recovery plant used by air conditioning play important influence for the heat transfer performance and flow resistance performance. The research conclusion provides guidance for air conditioning with wet thermal recovery plant of optimization.

Numerical Simulation Research on Louver Fin in Air Conditioning for Cars

2011 ◽  
Vol 383-390 ◽  
pp. 6463-6468
Author(s):  
Jun Jie Zhou ◽  
Hui Wang ◽  
Ding Biao Wang ◽  
Kang Zhang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Simulation Research ◽  
Air Conditioning System ◽  
Inlet Velocity ◽  
Heat Transfer Factor

Heat transfer and fluid flow on the air side for heat exchanger in the air conditioning system are numerically simulated by FLUENT commercial software. Numerical analysis is conducted on the plate louver fin, the sinusoid louver fin and the leaf louver fin when the inlet velocity rang is from 2m/s to 7m/s. Heat transfer factor and friction coefficient are respectively fitted with the Reynolds number by the correlation. The sinusoid louver fin is found to have the best comprehensive heat transfer performance. Not only the leaf louver fin’s comprehensive heat transfer performance is good, but also its pressure drop loss is 28.1%~38.8% lower than that of plate louver fin

Thermal Performance Research of Thermal Recovery Unit for Air-Conditioning Systerm

2011 ◽  
Vol 243-249 ◽  
pp. 4965-4968
Author(s):  
Yong An Li ◽  
Ting Ting Wang ◽  
Xue Lai Liu ◽  
Teng Xing
Keyword(s):  
Heat Transfer ◽  
Air Conditioning ◽  
Heat Transfer Performance ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Thermal Recovery ◽  
Transfer Performance ◽  
Recovery Unit ◽  
Air Channels ◽  
Flow Drag

This document established a three-dimensional laminar mathematical and physical model which describes heat transfer, mass transfer coupling process in wet thermal recovery unit for air-conditioning systerms, based on Computational Fluid Dynamics (CFD) simulations. In addition, the research discussed the distributions of pressure, temperature, concentration and other parameters in the air channels. The heat transfer performance was analyzed by enthalpy efficiency. The results showed that the structural parameters of wet thermal recovery unit for air-conditioning systerm played important influence in the heat transfer performance and flow drag performance. The research set a foundation for the optimal design of wet thermal recovery unit for air-conditioning systerm.

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