Papers by Author: Zhi Jun Zhang

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Authors: Li Li Zhao, Zhi Jun Zhang, Shi Wei Zhang
Abstract: The 3D physical model of the electrical water heater was built. The water-heater performance was resolved by computer fluid dynamics simulation (CFD). The heater performance is characterized by a new method rather than that the discharge efficiency, extraction efficiency and fraction of heat recoverable. The new method is based on the constant discharge water temperature and rate for end user, 5L/min and 43°C that include the hot water from EWH and cold water from outside EWH. But the water discharge rate from EWH was variable as the water temperature discharge from EWH was variable. Compared with the traditional method, it is more close to the user using reality condition.
463
Authors: Shi Wei Zhang, Guang Zhe Song, Zhuo Wang, Jin Ce Liu, Zhi Jun Zhang
Abstract: Aiming at the actual demand, the gas flow characteristics of butterfly vacuum control valves are investigated in this paper. Classification and characteristic of vacuum control valves are discussed in detail. The geometric and mathematic models for two kinds of butterfly vacuum control valves, with seal and without seal, are respectively built. The gas flows through the valve at different opening angles are simulated under different pressure by means of the Fluent software. The flow percentage function and adjustment sensitivity are introduced and formulated to describe the flow regulating characteristic of control valves. The flow conductance coefficient and flow loss coefficient are defined and formulated to describe the resistance characteristic of control valves. The dates and curves of some simulating examples are given and discussed.
1646
Authors: Jun Liu, Shi Wei Zhang, Zhi Jun Zhang
Abstract: In this paper, the vacuum freeze-drying experiments of both antler slices and whole antlers are reported in details. The moisture content and the eutectic temperature of antler were measured. A 22 h process curve of antler slice freeze drying was obtained. The freeze drying process of whole antler was also investigated. The microscopic tissue structure was observed and chemical compositions were analyzed for those freeze-dried whole antlers in comparison with the traditional water boiling and hot air drying method. More nutrients were retained for freeze drying in addition to the better physical properties than traditional drying.
441
Authors: Zhi Jun Zhang, Shi Wei Zhang, Cheng Hai Xu
Abstract: The 3D physical model of the electrical water heater was built. The water-heater performance of two kind structures was resolved by computer fluid dynamics simulation (CFD). The heater performance is characterized by a new method rather than that the discharge efficiency, extraction efficiency and fraction of heat recoverable. The new method is based on the constant discharge water temperature and rate for end user, 5L/min and 43°C that include the hot water from EWH and cold water from outside EWH. But the water discharge rate from EWH was variable as the water temperature discharge from EWH was variable. The discharge efficiency of conventional EWH was 79.312%, and the discharge efficiency of improved EWH was 84.97%. Compared with the traditional method, it is more close to the user using reality condition.
732
Authors: De Xi Wang, Zhi Jun Zhang
Abstract: The 3D physical model of the electrical water heater was built. The mathematical model of hot flow was resolved by computer fluid dynamics simulation (CFD). The effects of the rate of water draw on the heater performance have been investigated. The heater performance is characterized the discharge efficiency, extraction efficiency and fraction of heat recoverable. It was 85.9%, 66.0% and 70.9% respectively, and it was 74.0%, 27.3% and 39.9% respectively with discharge rate was 10L/min when all initial hot water temperature was 70°C. The water inner the water tank of draw rate 5L/min was well thermal stratification. It was also expatiated by the distribution temperature of CFD simulation.
1701
Authors: Zhi Jun Zhang, Shi Wei Zhang, Cheng Hai Xu
Abstract: The unsteady water discharge rate on performance of storage-type domestic electrical water-heaters with wedged inlet was studied by computer fluid dynamics simulation (CFD). The results were compared with those of conventional design EWHs having the same tank size. The heater performance is characterized the discharge efficiency, extraction efficiency and fraction of heat recoverable. The water draw-off temperature profile of steady and unsteady water discharge rate has nothing difference for wedged inlet structure, both curve was overlapped. The almost the same energy utility efficiency was gotten both steady and unsteady discharge rate for wedged inlet structure. The obviously difference of water draw-off temperature profile was shown for conventional inlet structure. Water draw-off temperature profile of unsteady discharge rate was decreased faster than steady discharge rate. The energy utility efficiency of unsteady discharge rate was also lower than steady discharge rate. The results were shown that the wedged inlet structure heater has excellent performance for energy utility efficiency under unsteady discharge rate.
299
Authors: Zhi Jun Zhang, Shi Wei Zhang, Cheng Hai Xu
Abstract: The 3D physical model with two different structure of the electrical water heater was built. The performance of water heater was studied by computer fluid dynamics simulation (CFD). The heater performance is characterized the discharge efficiency, extraction efficiency and fraction of heat recoverable. It was 73.7%, 45% and 49.8% respectively with conventional structure, and it was 81.1%, 54.1% and 59.6% respectively of improved structure with discharge rate was 5L/min when all initial hot water temperature was 90°C. The temperature distribution of different discharged stage was also disclosure. The water inner the water tank of improved structure has the better thermal stratification than traditional structure. It was also agreed with the water heat performance.
602
Authors: Shi Wei Zhang, Jin Ce Liu, Guang Zhe Song, Zhi Jun Zhang
Abstract: In order to improve the calculation method of the vacuum system design, the research focus on the way applying the Fluent software to calculation of gas flow in vacuum system in this paper. It is proved that the permission pressure lower limit is 1Pa for meeting the continuity hypothesis. The applicable flow patterns include turbulent flow, laminar flow and transitional flow between turbulent and laminar flow, which are totally defined as the viscous flow in the traditional vacuum field. By means of user define function (UDF), a layer mesh cell of negative quality source is defined to simulate the constant volume flow rate at the inlet of positive displacement vacuum pump, which makes up for the lack of compressible fluid velocity outlet boundary conditions in Fluent. The usability of Fluent in vacuum system is confirmed by a successful calculating example of gas flow in an ice condenser of vacuum freeze dryer.
1425
Authors: Shi Wei Zhang, Wen Sheng Liang, Zhi Jun Zhang
Abstract: In order to promote the performance measurement technique of the diffusion vacuum pumps, one full-automatic test equipment was newly developed and patented. The control system is the core of the test equipment and its reliability analysis is necessary. The structure and the characteristics of the test equipment are introduced in paper. The fault tree of the test equipment is set up and illustrated in detail. Based on fault tree analysis, the reliability designs of the hardware and software of the test equipment are carried out.
556
Authors: Zhi Jun Zhang, Shi Wei Zhang, Cheng Hai Xu
Abstract: Vacuum pump plays an important role in vacuum applications. The rotor and stator profile is one of the key factors for improving pump performance. In this paper, the traditional trochoidal vacuum pump that the rotor and stator profile both are trochoidal equation was introduced. The profile of trochoidal vacuum pump with two angle rotor was studied. In order to simply the design and manufacture, the rotor profile was substituted by the arc curve. The design parameter and performance was deducted on slenderness ratio. The slenderness ratio should larger than 4, otherwise the down part of the stator profile would be dent to upper. When slenderness ratio is 4, the utilization ratio of volume would be getting the maximum value, 0.5851942. The utilization ratio of volume was decreased with the slenderness ratio increased.
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