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Single-Phase Convection Heat Transfer
Published in Randall F. Barron, Gregory F. Nellis, Cryogenic Heat Transfer, 2017
Randall F. Barron, Gregory F. Nellis
For very low Reynolds numbers (less than about 1–2), the flow across a sphere is sometimes called creeping flow. The inertia forces are small and the viscous forces dominate. Creeping flow would result for a small (spherical) nitrogen ice particle having a diameter of 0.5 mm (0.02 in.) settling out in liquid nitrogen at 77.4 K (139.3°R) at a velocity of 0.40 mm/s (0.925 in./min), because the Reynolds number is approximately 1.0 for this condition. The drag is a result of viscous shear forces acting over the surface of the sphere.
Spacecraft and Missions
Published in Julio Sanchez, Maria P. Canton, William Perrizo, Space Image Processing, 2018
Julio Sanchez, Maria P. Canton
The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is a Hubble instrument that provides infrared imaging and spectroscopic analysis. NICMOS detects light with wavelengths between 0.8 and 2.5 μm. This range exceeds the sensitivity of the human eye. The infrared detectors in NICMOS must operate at very cold temperatures. These components are kept cold by means of a cryogenic dewar which contains frozen nitrogen ice. NICMOS is Hubble’s first and only cryogenic instrument.
Fabrication of highly isotropic porous alumina refractory clinkers consisting of platelets using a gelatin-sol
Published in Journal of Asian Ceramic Societies, 2020
Daimu Muto, Shinobu Hashimoto, Hiroki Kondo, Yusuke Daiko, Sawao Honda, Yuji Iwamoto
The cause of the suppression of coarse ice crystal formation by ethanol is presumed as follows. First, the freezing point of the aqueous ethanol solution decreases as the ethanol concentration increases. For example, the freezing points of aqueous solutions of 10, 20, and 30 wt.% ethanol are about −4.6, −11.2, and −20.9°C, respectively, and the freezing point of ethanol is −114.5°C [23]. In general, when ice crystals are formed at lower temperatures, the frequency of nucleation increases and the crystals become finer. When formed at relatively high temperatures, the crystal growth rate increases and the crystals become coarser. In addition, ethanol (C2H5OH) is composed of a hydrophilic hydroxyl group (-OH) and a hydrophobic ethyl group (-C2H5). Since the ethyl groups are bonded to each other in an aqueous ethanol solution, bonding between water molecules and ethanol molecules hardly occurs [24,25]. Upon rapid cooling with liquid nitrogen, ice crystal nuclei are formed. At this time, ethanol as an impurity is discharged out of the ice. As a result, the surrounding ice crystals are surrounded by an aqueous ethanol solution having a higher concentration and a lower freezing point, which reduces the growth rate of the ice crystals. Furthermore, the individual ice crystal sizes remain small because the ethanol is sandwiched between the ice crystals, and the ice crystals are not integrated with each other.
Porous frozen material approach to freeze-drying of instant coffee
Published in Drying Technology, 2019
Wei Wang, Shihao Wang, Yanqiu Pan, Jing Yang, Shuo Zhang, Guohua Chen
The aqueous solution of coffee was prepared by dissolving 40 g of coffee powder with 60 g of de-ionized water. The initial moisture content was 1.5 kg/kg on a dry basis. The solid frozen material without initial pores was prepared by pouring the solution into a cylindrical container of 14.8 mm in diameter with a Teflon supporting pad of 5 mm in thickness at bottom, and then placed into a freezer at –48 °C for 6 h. The porous frozen material with a certain initial porosity was prepared with two freezing steps, initial freezing and further freezing. During the initial freezing, the liquid nitrogen ice-cream making method was employed, which is described as follows. The liquid nitrogen was slowly added into the solution in a heat-insulated barrel while mechanical stirring at about 400 rpm. The solution being processed then expanded into a mousse-like frozen material with initial pores. It should be pointed out that no any additive like an emulsion stabilizer has been used in this step.[13,39] Afterwards, such a premade material was molded in a container with a supporting pad at bottom, and quickly placed into the freezer for further freezing at –48 °C for 6 h. The molding allowed forming the initially solid and porous frozen samples of equal mass.
Stress Distribution and Safety Evaluation of Pipeline in Ice Plug of Nuclear Power
Published in Nuclear Science and Engineering, 2022
Linjun Xie, Changxun Wang, Wei Zhang, Xin Shen, Minglei Hu, Chunhua Bian, Yilun Xu
Before the test, the pipe is placed on the support frame, and the flanges are sealed at both ends. As shown in Fig. 6, the liquid nitrogen ice plug jacket is installed in the middle of the pipe, and the heat transfer agent is filled between the jacket and pipe wall to improve thermal conductivity. Figure 7 shows the installation positions of the 9 thermometers and 15 low-temperature strain gauge pairs that are arranged on the outer surface of the pipeline. Then, the inlet and the exhaust valve are opened to fill the pipe with water. After that, all valves on the pipe are closed, and liquid nitrogen is injected into the jacket for refrigeration.