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Deng H.R.,Zhejiang University | Liu Y.M.,Zhejiang University | Ma R.F.,Zhejiang University | Han D.Y.,Zhejiang University | And 3 more authors.
IOP Conference Series: Materials Science and Engineering

The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb3Sn and NbTi, MgB2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB2, this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios. Source

Wang L.-Y.,Zhejiang University | Wang L.-Y.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | Gan Z.-H.,Zhejiang University | Gan Z.-H.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | And 7 more authors.
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

Based on an existing single stage pulse tube cooler, a cascade pulse tube cooler is designed and tested. Experimental results show that when the input electric power is 500 W, the no-load temperature of the primary stage cooler is 123.3 K, while that of the secondary stage cooler is 131.0 K. The cooling capacity at 233 K is 143.7 W and 62.9 W for the primary and secondary stage cooler, respectively, thus the cascade pulse tube cooler obtains a total cooling power of 206.6 W at 233 K, which is higher than the simulation result of the single-stage cooler 189.6 W at 233 K. The feasibility of cascade concept is demonstrated. This work is a rewarding exploration of regenerative cooling method applied at room temperature refrigeration, also it's helpful for high power pulse tube cryocoolers working at much lower temperatures. © 2015, Science Press. All right reserved. Source

Wang K.,Zhejiang University | Wang K.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | Wang K.,Nanyang Technological University | Zhang J.,Zhejiang University | And 11 more authors.
Applied Thermal Engineering

Acoustic impedance matching is critical to the overall performances of a traveling-wave thermoacoustic electric generator. This paper presents an effective approach for matching the acoustic impedances of the thermoacoustic engine and the linear alternators for maximizing the output electric power and thermal-to-electric efficiency. The acoustic impedance characteristics of the engine and the linear alternators are analyzed separately, and the methods for modulating the acoustic impedances are investigated numerically. Specially, two different coupling locations including one at the resonator and the other one at the loop of the thermoacoustic engine are compared. It is found that the imaginary part of the load acoustic impedance should be near zero for a good output performance of the engine at either coupling location. The real part of the optimal acoustic impedance for the coupling location at the resonator is smaller than that for the one at the loop. The acoustic impedance of the linear alternator can be simply and effectively adjusted to the expected range by tuning the operating frequency, load resistance and the electric capacitance. Both the experiments and numerical simulations show that a better matched condition can be achieved when they are coupled at the location at the resonator. Maximum output electric power of 750.4 W and the highest thermal-to-electric efficiency of 0.163 have been achieved. When they are coupled at the loop, the maximum electric power and the thermal-to-electric efficiency become 506.4 W and 0.146 due to the lower quality of the acoustic matching. The acoustic matching approach presented in the paper would be helpful for guiding the designs of thermoacoustic/alternator and compressor/cryocooler systems. © 2016 Elsevier Ltd. All rights reserved. Source

Zhang J.H.,Zhejiang University | Zhang J.H.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | Bao S.R.,Zhejiang University | Bao S.R.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | And 4 more authors.
IOP Conference Series: Materials Science and Engineering

Dynamic visualization is of great significance in the research of flow conditions and mass transfer process of cryogenic fluids. In this paper, two common ways to measure the concentration of cryogenic fluids are introduced and compared. To improve the real-time monitoring of cryogenic fluid, a non-contact dynamic optical measurement system using laser interferometry is designed, which is sensitive to subtle changes of fluid concentration. A precise and dynamic interference pattern can be obtained using this system. Two-dimensional concentration distribution of the fluid can be calculated from the interference pattern. Detailed calculation process is presented in the paper. Source

Li P.-C.,Zhejiang University | Li P.-C.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | Sun Z.-J.,Zhejiang University | Sun Z.-J.,Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province | And 6 more authors.
Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science)

A thermodynamic exergy analysis method was adopted in order to solve the problem that it is hard to evaluate the performance of corrugated plate heat transfer elements with perforations. Exergy loss curve and exergy loss coefficient curve were obtained by using transient test method. The curves both have a turning point at Reynolds number of about 4 400, and achieve the peak value at the turning point. The turning point was derived from the transition state that has violent irregular intense motions, and the entropy increases with the rising Reynolds number, making exergy loss and exergy loss coefficient get the maximum value of 41 kJ and 0.65, respectively. Turning point is the critical point of transition state to fully turbulent. The result shows that the exergy analysis method can evaluate the effect of heat transfer enhancement reasonably, and serious energy waste happens near the turning point. © 2016, Zhejiang University Press. All right reserved. Source

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