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.

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 Experimental and Simulation Study of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center

2020 ◽  
Vol 10 (4) ◽  
pp. 1255
Author(s):  
Liping Zeng ◽  
Xing Liu ◽  
Quan Zhang ◽  
Jun Yi ◽  
Xiaohua Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Outlet Temperature ◽  
Transfer Performance ◽  
Micro Channel ◽  
Heat Transfer Capacity ◽  
The Heat Transfer Coefficient

This paper mainly studies the heat transfer performance of backplane micro-channel heat pipes by establishing a steady-state numerical model. Compared with the experimental data, the heat transfer characteristics under different structure parameters and operating parameters were studied, and the change of heat transfer coefficient inside the system, the air outlet temperature of the back plate and the influence of different environmental factors on the heat transfer performance of the system were analyzed. The results show that the overall error between simulation results and experimental data is less than 10%. In the range of the optimal filling rate (FR = 64.40%–73.60%), the outlet temperature at the lowest point and the highest point of the evaporation section is 22.46 °C and 19.60 °C, the temperature difference does not exceed 3 °C, and the distribution gradient in vertical height is small and the air outlet temperature is uniform. The heat transfer coefficient between the evaporator and the condenser is larger than the heat transfer coefficient under the conditions of low and high liquid charge rate. It increases gradually along the flow direction, and decreases gradually with the flow rate of the condenser. When the width of the flat tube of the evaporator increases from 20 mm to 28 mm, the internal pressure drop of the evaporator decreases by 45.83% and the heat exchange increases by 18.34%. When the number of evaporator slices increases from 16 to 24, the heat transfer increases first and then decreases, with an overall decrease of 2.86% and an increase of 87.67% in the internal pressure drop of the evaporator. The inclination angle of the corrugation changes from 30° to 60°, and the heat transfer capacity and pressure drop increase. After the inclination angle is greater than 60°, the heat transfer capacity and resistance decrease. The results are of great significance to system optimization design and engineering practical application.

Preparation and Characterization of Rutile Titania Nanofluids Stabilized in Different Surfactants Base Fluids

2020 ◽  
Vol 10 (5) ◽  
pp. 682-695
Author(s):  
Radwa A. El-Salamony ◽  
Mohamed Z. Abd-Elaziz ◽  
Rania E. Morsi ◽  
Ahmed M. Al-Sabagh ◽  
Saad S.M. Hassan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Performance ◽  
Sodium Dodecyl ◽  
Transfer Performance ◽  
Heat Transfer Fluids ◽  
Transmission Electron ◽  
Performance Of Heat Transfer ◽  
Rutile Titania ◽  
The Stability

Background: Improvement of conventional heat transfer fluids for achieving higher energy efficiencies in thermal equipment is a key parameter to conserve energy in industries. The heat transfer fluids such as water, oil and ethylene glycol greatly suffer low heat transfer performance in industrial processes. There is a need to develop new types of heat transfer fluids that are more effective in terms of heat transfer performance. Nanofluids enhance thermal conductivity and improve the thermal performance of heat transfer systems. Methods: New titania nanofluid samples consisting of 0.0625 to 1% TiO2 nanoparticles were prepared and characterized. The method of preparation was based on prior precipitation of TiO2 from an ammoniacal solution of pH 9 and calcination at 900°C. Solubilization, homogenization and stabilization of the of the nanoparticles were performed by sonication in the presence of sodium dodecyl sulfate (SDS) anionic surfactant and cetyltrimethylammonium bromide (CTAB) cationic surfactant. Results: This treatment was also utilized to increase the stability and improve the thermal properties of the fluid. Conclusion: Several characterization techniques including measurements of hydrodynamic size distribution, zeta potential, transmission electron microscopy (TEM), viscosity, density, specific heat, thermal conductivity, and sedimentation photo capturing were used to measure and confirm the stability and sedimentation rate of the prepared nanofluids.

Development and Evaluation of Nanofluid Heavy-Duty Coolant

2014 ◽  
Vol 1082 ◽  
pp. 279-283
Author(s):  
Jin Mao Chen ◽  
Guan Jun Leng ◽  
Ru Juan Yi ◽  
Bo Gao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Organic Acid ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heavy Duty ◽  
Heat Transfer Capacity ◽  
Engine Coolant

In order to meet the demand of heat rejection requirement of heavy-duty engine, a novel nanofluid heavy-duty coolant was developed in this paper by taking advantage of nanofluid heat transfer technique and organic acid technique. Comparing with conventional heavy-duty coolant, the heat transfer capacity increased more than 10%, which solved the problems of limited thermal conductivity and convective heat transfer performance. The coolant possessed the characteristics of a qualified engine coolant should have and could be a promising engine coolant.

Effect of Increasing Wick Evaporation Area on Heat Transfer Performance for Loop Heat Pipes

2013 ◽  
Vol 711 ◽  
pp. 223-228 ◽  
Author(s):  
Shen Chun Wu ◽  
Jhih Huang Gao ◽  
Zih Yan Huang ◽  
Dawn Wang ◽  
Cho Jeng Huang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Surface Area ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Loop Heat Pipe ◽  
Transfer Performance ◽  
Loop Heat Pipes ◽  
Heat Transfer Capacity

This study investigates the effects of increasing the evaporating area of wick in a loop heat pipe (LHP). This work attempts to improve the performance of the loop heat pipe by increasing the number of grooves and thereby the surface area of the wick. The number of grooves is increased from eight to twelve. Experimental results show that increasing the number of grooves not only increases the surface area of the wick but also enhances LHP performance. When the evaporating surface area increases by 50%, which corresponds to increasing the number of grooves from eight to twelve, the heat transfer capacity increases from 310W to 470W and the thermal resistance is reduced from 0.21°C/W to 0.17°C/W. According to preliminary measurements, increasing the number of grooves in the loop heat pipe is highly promising for improving the heat transfer performance.

Investigations of Single Jet Impinging on Plates With Circular Dimples

2017 ◽  
Author(s):  
Zhiqiang Guo ◽  
Mei Zheng ◽  
Yinze Liu ◽  
Wei Dong
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Performance ◽  
Enhancement Effect ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Impingement Heat Transfer ◽  
Single Jet ◽  
Different Depths

In this paper, experimental and numerical investigations are both conducted to study the effect of circular dimples on the heat transfer performance of jets impingement. The circular dimples, set as one kind of surface structures on flat plate, have the same diameter of 3 mm but with different depths: 1.2 mm, 0.9 mm and 0.6 mm. Furthermore, in order to understand the mechanism of impingement heat transfer with circular dimples deeply, three different jet locations are studied in this paper. For the experimental investigations, the infrared thermography is applied to gain the temperature distributions on the flat plate. A comparison is made between the numerical results and experimental data, which indicates that they are in good agreement. The numerical results show that the dimples on the plates have significant effects on the impingement heat transfer. The overall averaged and local heat transfer coefficient in a single jet impingement on the smooth and dimpled plates are obtained and compared, as well as the flow structure. The effect of the dimples on the heat transfer performance of the target plates is different for different locations of dimples. Velocity distributions and streamlines near the target plates are also shown to explain the heat transfer characteristics. From the investigations, for the dimpled plates with different depths, the deeper dimples have the better averaged heat transfer on the target plates. The dimpled surface enhances the heat transfer performance obviously with H/D of 1.5. However, with the distance between the impinging hole and the target plate increasing, the transition location of the impact zone and the wall jet zone advances and the enhancement effect decreases. Moreover, further downstream region on the dimpled plates shows lower heat transfer enhancement effect and the effect becomes approximately invisible after X/D is larger than 3. The fluid in the dimples with different depths has the same streamline. The heat transfer enhancement at the downstream of dimples is better than the upstream.

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

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