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Ren T.,Shanghai JiaoTong University | Sun H.,Shanghai JiaoTong University | Xia G.,Shanghai JiaoTong University | Ding G.,Shanghai JiaoTong University | And 3 more authors.
ACRA 2016 - 8th Asian Conference on Refrigeration and Air-Conditioning | Year: 2016

To quickly design a room air conditioner with small diameter copper tube, a heat exchanger model applicable for system simulation with fast speed, high accuracy and versatility is needed. This paper presents a graph-theory based multi-zone model for fin-and-tube heat exchangers. In this model, a directed graph and a breadth first traversal algorithm are proposed to describe the refrigerant flow circuits and automatically generate the flow paths, respectively, capable to calculate flexible user defined refrigerant circuits; a sequencing method is developed to rearrange the flow paths and control the calculation order, addressing the issue of refrigerant and air coupling of different flow paths; a stepped correction method is established, improving the accuracy and keeping the advantages of fast computation speed of multi-zone model. The presented model is validated by experiments, and the deviations of the predicted heat capacity of heat exchangers from the measured ones are within 5%.


Wu W.,Shanghai JiaoTong University | Ding G.L.,Shanghai JiaoTong University | Gao Y.F.,International Copper Association Shanghai Office | Song J.,International Copper Association Shanghai Office
6th Asian Conference on Refrigeration and Air Conditioning, ACRA 2012 | Year: 2012

The heat transfer characteristics of fin-and-tube heat exchangers with 5 mm diameter tubes under wet conditions were investigated by experiments on 11 louver fin-and-tube heat exchangers. The effects of fin pitch, fin size and inlet relative humidity on air-side performance were analyzed. The results indicated that the effect of inlet relative humidity on the heat transfer rate is small, and heat transfer rate decreases with the increase of fin pitch, which is more obvious than that of fin-and-tube heat exchanger with 7 mm or larger diameter tubes. The water bridge was observed at the bottom of fin in experiments; however, it did not occur on the fin with 7 mm or large diameter tubes. A correlation for j factor was developed to predict the heat transfer performance of fin-and-tube heat exchanger with 5 mm diameter tubes. The mean deviations of the proposed j correlation are within 6.5%.


Pu H.,Shanghai JiaoTong University | Ding G.,Shanghai JiaoTong University | Hu H.,Shanghai JiaoTong University | Gao Y.,International Copper Association Shanghai Office
HVAC and R Research | Year: 2010

In this study, the effect of salt spray corrosion on the air-side performance of finned-tube heat exchangers with hydrophilic coating under dehumidifying conditions was experimentally investigated. Artificial accelerated method of salt spray corrosion on the hydrophilic coated heat exchangers was used for simulating the corrosion process of the actual heat exchangers. The experimental results show that the contact angles of hydrophilic coated aluminum fins increase with the increase of salt spray corrosion hours, which results in the degradation of hydrophilicity of fins; the heat transfer is enhanced at lower inlet air velocity and degraded at high inlet air velocity for the pitting corroded heat exchanger with hydrophilic coating; compared with the uncorroded finned-tube heat exchanger with hydrophilic coating at the inlet air velocity ranging from 0.5 to 2.0 m/s (5905.5 to 23622.0 ft/h), the effects of salt spray corrosion on the air-side heat transfer coefficient and on the air-side pressure drop are approximately within the range of -20.5%∼8.7% and 1.7%∼13.1%, respectively. Copyright © 2010 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.


Huang X.,Shanghai JiaoTong University | Ding G.,Shanghai JiaoTong University | Hu H.,Shanghai JiaoTong University | Zhu Y.,Shanghai JiaoTong University | And 2 more authors.
International Journal of Refrigeration | Year: 2010

Flow condensation pressure drop characteristics of R410A-oil mixture inside small diameter (5.0 mm and 4.0 mm O.D.) horizontal microfin tubes were investigated experimentally covering nominal oil concentrations from 0% to 5%. The research results indicate that, comparing with the frictional pressure drop of pure R410A, the frictional pressure drop of R410A-oil mixture may decrease by maximum of 18% when the vapor quality is lower than 0.6, and increase by maximum of 13% when the vapor quality is higher than 0.6. A new frictional pressure drop correlation for R410A-oil mixture flow condensation inside microfin tubes is developed based on the refrigerant-oil mixture properties, and can agree with 94% of the experimental data within a deviation of -30% to +30%. © 2010 Elsevier Ltd and IIR. All rights reserved.


Huang X.,Shanghai JiaoTong University | Ding G.,Shanghai JiaoTong University | Hu H.,Shanghai JiaoTong University | Zhu Y.,Shanghai JiaoTong University | And 2 more authors.
Experimental Thermal and Fluid Science | Year: 2010

Condensation heat transfer characteristics of R410A-oil mixture in 5 mm and 4 mm outside diameter horizontal microfin tubes were investigated experimentally. The experimental condensing temperature is 40 °C, and nominal oil concentration range is from 0% to 5%. The test results indicate that the presence of oil deteriorates the heat transfer. The deterioration effect is negligible at nominal oil concentration of 1%, and becomes obvious with the increase of nominal oil concentration. At 5% nominal oil concentration, the heat transfer coefficient of R410A-oil mixture is found to have a maximum reduction of 25.1% and 23.8% for 5 mm and 4 mm tubes, respectively. The predictabilities of the existing condensation heat transfer correlations were verified with the experimental data, and Yu and Koyama correlation [29] shows the best predictability. By replacing the pure refrigerant properties with the mixture's properties, Yu and Koyama correlation has a deviation of -15% to + 20% in predicting the local condensation heat transfer coefficient of R410A-oil mixture. © 2010 Elsevier Inc. All rights reserved.


Pu H.,Shanghai JiaoTong University | Ding G.-L.,Shanghai JiaoTong University | Hu H.-T.,Shanghai JiaoTong University | Gao Y.-F.,International Copper Association Shanghai Office
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2010

The effect of salt spray corrosion on the air-side hydrophilicity and the thermal-hydraulic performance of copper-fin heat exchangers were experimentally investigated. Artificial accelerated method of salt spray corrosion on the copper-fin heat exchangers was used for simulating the actual corroded heat exchangers. The experimental results show that, the contact angles increase with the increase of salt spray corrosion hours, which results in the degradation of the hydrophilicity of copper fin. The air-side heat transfer coefficients decrease and pressure drops increase with the increase of corrosion hours. The effect of salt spray corrosion on the heat transfer coefficients and pressure drops become more obvious with the increase of inlet air velocity. The heat transfer coefficients of the corroded copper-fin heat exchangers decrease by 4.4-34.0% and the pressure drop increase by 5.2-26.1% comparing with those of the uncorroded copper-fin heat exchanger at the inlet air velocity ranging from 0.5 to 2.0 m/s. © 2010 Springer-Verlag.


Hu H.-T.,Shanghai JiaoTong University | Ding G.-L.,Shanghai JiaoTong University | Huang X.-C.,Shanghai JiaoTong University | Deng B.,Shanghai Institute of Technology | Gao Y.-F.,International Copper Association Shanghai Office
Journal of Enhanced Heat Transfer | Year: 2011

Two-phase heat transfer characteristics of R410A/oil mixture flow boiling inside a horizontal microfin tube with the outside diameter of 5.0 mm were investigated experimentally at nominal oil concentrations from 0 to 5%. The test results show that the presence of oil enhances the heat transfer by a maximum of 30% at vapor qualities lower than 0.8. However, at vapor qualities near 0.8, the local heat transfer coefficients increase at low nominal oil concentration, reach the maximum at 3-5% nominal oil concentrations under the present experimental conditions, and then fall off with the increase of nominal oil concentration. At high vapor qualities from 0.85 to 0.9, the maximum of local heat transfer coefficient shifts to lower nominal oil concentration with the increase of vapor quality and mass flux, and the local heat transfer coefficient falls off rapidly with the increase of nominal oil concentration and vapor quality. A correlation to predict the local heat transfer coefficients of R410A/oil mixture flow boiling inside microfin tubes was developed based on local properties of refrigerant-oil mixture, and it agrees with 91% of the experimental data within a deviation of ±35%. © 2011 by Begell House, Inc.


Pu H.,Shanghai JiaoTong University | Ding G.-l.,Shanghai JiaoTong University | Ma X.-k.,Shanghai JiaoTong University | Hu H.-t.,Shanghai JiaoTong University | Gao Y.-f.,International Copper Association Shanghai Office
International Journal of Refrigeration | Year: 2010

In this study, the effects of long-term intermittent operations on the air-side heat transfer and pressure drop performance of finned tube evaporators of air conditioners were investigated by experiments on an aluminum-fin evaporator and a copper-fin evaporator. In order to simulate intermittent operations of on-off controlled air conditioners, the temperatures of the two evaporators changed to 5 ± 0.5 °C at first and then to 27 ± 0.5 °C repeatedly. The repetition number was up to 4800, and the air-side heat transfer and pressure drop of the two evaporators were tested after every 300 repetitions. The test results indicate that after long-term intermittent operations, the air-side heat transfer coefficient decreases and the pressure drop increases. The variations of the heat transfer coefficient and the pressure drop are more obvious at lower inlet air velocity, and the influence of long-term intermittent operations on the aluminum-fin evaporator is greater than that on the copper-fin evaporator. © 2009 Elsevier Ltd and IIR.


Huang X.,Shanghai JiaoTong University | Ding G.,Shanghai JiaoTong University | Hu H.,Shanghai JiaoTong University | Zhu Y.,Shanghai JiaoTong University | And 3 more authors.
International Journal of Refrigeration | Year: 2010

The influence of oil on condensation heat transfer of R410A inside 4.18 mm and 1.6 mm inner diameter horizontal smooth tubes is investigated experimentally. The experimental condensing temperature is 40 °C, and nominal oil concentration range is from 0% to 5%. The test results indicate that the presence of oil deteriorates the heat transfer, and the deterioration effect becomes obvious with the increase of oil concentration. At oil concentration of 5%, the heat transfer coefficient decreases by maximum 24.9% and 28.5% for 4.18 mm and 1.6 mm tubes, respectively. A new correlation for heat transfer coefficients of R410A-oil mixture flow condensation inside smooth tubes is proposed, which agrees with all the experimental data within a deviation of -30% ∼ +20%. © 2009 Elsevier Ltd and IIR.


Huang X.,Shanghai JiaoTong University | Zhu Y.,Shanghai JiaoTong University | Ding G.,Shanghai JiaoTong University | Gao Y.,International Copper Association Shanghai Office | And 2 more authors.
HVAC and R Research | Year: 2010

Two-phase frictional pressure drop characteristics of R410A-oil mixture flow condensation inside 4.18 mm (0.165 in) and 1.6 mm (0.063 in) I.D. diameter horizontal smooth tubes were investigated experimentally. The experimental condensing temperature is 40° (104°F), and the nominal oil concentration range is from 0% to 5%. The test results indicate that the presence of oil always decreases the flow condensation frictional pressure drop, and the decrement increases with the nominal oil concentration. The decrements for 4.18 mm (0.165 in.) and 1.6 mm (0.063 in.) are 1%∼19.5% and 1.5%∼17.4% tubes, respectively. A new correlation for the frictional pressure drop of R410A-oil mixture flow condensation inside smooth tubes is proposed and agrees with 96% of the experimental data within a deviation of -20%∼+30%. © 2010 American Society of Heating.

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