PERFORMANCE OF R-1234YF IN MOBILE AIR CONDITIONING SYSTEM UNDER DIFFERENT HEAT LOAD CONDITIONS

YU ZHAO,JIANGPING CHEN,BAIXING XU,BIN HE 대한설비공학회 2012 International Journal Of Air-Conditioning and Refr Vol.20 No.3

"Drop-in" tests of R-1234yf in a mobile air conditioning (MAC) system were conducted, and the system performance results were compared with those of the same system using R-134a. The performance tests were performed in a psychrometric calorimeter test facility based on enthalpy-difference method. The system performance was investigated under low-, middle- and high-load conditions. The results showed that the optimum refrigerant charge of R-1234yf was approximately 90% compared with that of R-134a under the same MAC system. When operated under optimum refrigerant charge, the system cooling capacity and COP of R-1234yf was 11% and 8.3% lower than that of the R-134a system, respectively. When wind tunnel test was conducted on a practical vehicle, the result showed that the carriage temperature in the vehicle with the R-1234yf system dropped slower. The average carriage temperature and blower outlet temperature were $2^{\circ}C$ higher than those of the R-134a system during the test.

EXPERIMENTAL AND CFD INVESTIGATION OF R410A DISTRIBUTORS FOR AIR CONDITIONER

QING HAN,CHI ZHANG,JIANGPING CHEN 대한설비공학회 2014 International Journal Of Air-Conditioning and Refr Vol.22 No.2

In order to obtain a higher heat transfer coffcient of refrigerant flow, the diameter of tubes tendsto be smaller and smaller, which leads to large pressure drop of the refrigerant flow. Therefore,multiple numbers of parallel refrigerant passages are employed by using distributors. It is veryimportant to distribute the two-phase refrigerant evenly into each tube, otherwise the thermalperformance is significantly deteriorated. The performance reduction by °ow mal-distributioncould be as large as 20–25%. The goal of this paper is to investigate the influence of differentconflgurations to the performance of refrigerant distributors by experiments and computational fluid dynamic code. The effects of mass flow rate and quality of distributor inlet on the characteristicswere also quantitatively considered. In this study, an experiment test rig was built tomeasure the mass flow rate and quality of four circuits after using distributors under differentconditions respectively. Refrigerant R410A was used as working fluids. Three classic types (jet,cyclone and reservoir) of distributors with four paths were manufactured and tested under relevantoperating conditions. The inlet temperature was 4C, mass flow rate range was 50–100 kg/hand the quality range was 0.1–0.3. Experimental results show that the maximum deviation ofmass flow rate for jet, cyclone and reservoir type is 13.0%, 21.6% and 10.9%, respectively; themaximum deviation of quality was 0.08, 0.10 and 0.05, respectively. In addition, the standarddeviation of mass flow rate and quality over four paths were selected to evaluate the performanceof different type distributors. The results show that the performance of jet and reservoir are betterthan cyclone. The flow behavior of two-phase refrigerant such as phase distribution and separationphenomena was studied by Computational Fluid Dynamics (CFD). The flow pattern ofinlet for R410A was investigated and used in the present model. The results in the present modelshow good and reasonable approximation with experimental data which validate the CFD simulation. CFD simulation analysis elucidates the mechanics which shows how the configurationand operation conditions affect the refrigerant distribution.

OPTIMIZATION OF THE RESERVE-TYPE DISTRIBUTOR FOR R410A AIR CONDITIONER

CHI ZHANG,YING WANG,JIANGPING CHEN 대한설비공학회 2014 International Journal Of Air-Conditioning and Refr Vol.22 No.4

Mal-distribution of refrigerant in a cross-flow type evaporator with parallel paths is very important, which can lead to a loss of heat exchanger capacity to 25%. Distributors are used to balance the two-phase refrigerant distributions in each path. Apart from the structural factors, there are other factors influencing the performance of distributor greatly. In this paper, influences of several nonstructural factors on reservoir distributor are investigated experimentally under varied working conditions. The inlet tube configuration, installation orientation and capillary tube length are also studied. One experiment apparatus is developed to measure the refrigerant mass flow rate and the quality based on R410A air conditioner. It is found that influence caused by inlet tube before the distributor is small. The average STD is only 2.76%. Influence caused by orientation is broad. The average STD is less than 9% on the orientation of 15°. On the orientation of 90°, STDs of different conditions are all more than 40%. For orientation, mass flow rate sensitivity is larger than quality sensitivity. Capillary tubes with different length can be used to adjust distribution. Average STD with sizable capillary length difference is 9.47%. It means that only small mal-distribution can be adjusted by using different-length capillary tubes. Capillary tube length sensitivity increases with the increase of difference between outlet tubes or the decrease of average length of outlet tubes.

Experimental and Numerical Investigations of the Double-Barrel Distributor for Air Conditioner

CHI ZHANG,Dandong Wang,JIANGPING CHEN,Xihui Sun 대한설비공학회 2015 International Journal of Air-Conditioning and Refr Vol.23 No.3

Flow mal-distribution of refrigerant in small diameter tube heat exchangers is a great concern, which may lead to a 25% efficiency loss. Two-phase refrigerant distributors are set before evaporators to separate refrigerant into parallel paths uniformly. In this paper, a new type of distributor with two barrels is proposed. Experimental test and numerical simulation were both carried out to evaluate the performance and to understand internal hydrodynamic flow behavior. Compared with the previous distributor, it is found that the double-barrel distributor with proper parameters performs better. The relative error between experimental and simulation results is less than 15%, which proves the reliability of the established simulation model. Computation fluid dynamics (CFD) calculation indicates that the distribution performance is improved with properly larger bottom and top barrel diameters. With the increase of the bottom barrel diameter, bene¯cial reflux of refrigerant occurs in bottom barrel and when top barrel diameter is larger, little refrigerant flows directly into outlet capillary tubes without mixture or reflux. In addition, parameters such as top barrel diameter, top barrel height, bottom barrel diameter, bottom barrel height, mass flow rate and quality are studied by Taguchi Method to analyze the parameter sensitivity. The effect of the parameters listed below ranges from biggest to smallest: mass flow rate, bottom barrel height, quality, top barrel height, bottom barrel diameter and independent top barrel diameter. An optimized two-barrel distributor is achieved with proper top and bottom barrel diameters and larger bottom and top barrel heights.

Pretreatment of sweet sorghum bagasse by alkaline hydrogen peroxide for enhancing ethanol production

Xudong Li,Weixing Cao,Chen Sun,Jiangping Qiu,Ronghou Liu,Le Zhang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.3

Effects of severe and mild alkaline hydrogen peroxide (AHP) pretreatment on ethanol production from sweet sorghum bagasse via pre-simultaneous saccharification fermentation, and the chemical structure changes of the substrates were investigated. The results showed that the bagasse pretreated by severe AHP could produce more ethanol than that of mild AHP. The maximum ethanol concentration of the bagasses from mild and severe AHP pretreatment with 8% bagasse loading was 7.642±0.140 g/L and 19.330±0.085 g/L, respectively. Moreover, the FTIR and NMR analysis illustrated that the molecule and surface structures of the pretreated bagasse were significantly changed compared with the control. The potential biomass energy production of the effluent from the pretreatment was also briefly discussed for future utilization of waste solution.The heat energy potentials of waste solution with severe and mild AHP pretreatment were 367.2 kJ/Leffluent and 327.6 kJ/Leffluent, respectively.