Experimental Investigation on Cryogenic Line Chill-Down Process by Using Liquid Nitrogen

2016 ◽  
Author(s):  
Lingxue Jin ◽  
Mansu Seo ◽  
Hyokjin Cho ◽  
Changgi Park ◽  
Cheonkyu Lee ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Liquid Nitrogen ◽  
Mass Flow ◽  
Flow Rate ◽  
Cryogenic Liquid ◽  
Transient Temperature ◽  
Outer Diameter ◽  
Horizontal Pipe ◽  
Pressure Profiles ◽  
Pipe Line

Generally, a part of transporting liquids are used as the coolant to chill down the transfer line. Minimizing the line chill-down time and the consumption of the cryogenic propellant during the line chill-down is a mainly concerned issue. In this study, the cryogenic line chill-down experiments are conducted on a 12.7 mm outer diameter, 1.25 mm wall thickness and 7 m long stainless steel horizontal pipe with liquid nitrogen (LN2) injection. The pipe is vacuum jacketed to reduce the heat inleak from room temperature to the cryogenic liquid. The temperature and the pressure profiles of the chill-down line are obtained at the location 6 meters away from the pipe inlet under various mass flow rates. The history of the transient temperature, the pressure and the mass flow rate during the line chill-down process are monitored for various cases. The relationship between the line chill-down time and the mass flow rate is analyzed and presented for one representative pipe line geometry.

An Experimental Study on Cryogenic Spray Quenching of a Circular Metal Disk II. Chilldown Efficiency and Effects of Coating and Flow Pulsing

2021 ◽  
Author(s):  
Jun Dong ◽  
Hao Wang ◽  
Samuel Darr ◽  
Jason Hartwig ◽  
Jacob Chung
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Liquid Nitrogen ◽  
Mass Flow ◽  
Flow Rate ◽  
Continuous Flow ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Teflon Coating ◽  
Bare Surface

Abstract This is the second part of a two-part series that presents the results of liquid nitrogen spray quenching of a Stainless Steel disc. The results of continuous-flow spray chilldown of a bare surface disc are summarized first that serves as the baseline information for evaluating the effects of disc surface coating and pulse flow. We found that for continuous-flow spray chilldown of a bare surface disc, the chilldown efficiency is mainly a function of the average mass flow rate with the trend of decreasing efficiency with increasing mass flow rate. Additional experiments were performed to evaluate the enhancement of cryogenic spray quenching by three techniques: 1. Using intermittent pulse sprays on SS bare surface, 2. Coating the SS surface with a layer of low thermal conductivity Teflon film, and 3. Spraying liquid nitrogen intermittently on the coated SS surface. In general, the results indicate that all three methods effectively produced higher spray thermal efficiencies and reduced liquid nitrogen mass consumption. However, it was also found that the Teflon coating was more effective than the flow pulsing due to that the Teflon coating induced a large surface temperature drop at the beginning of the chilldown that allowed the quenching to move quickly from poor heat transfer film boiling to efficient heat transfer transition and nucleate boiling regimes. This quick transition shortens the film boiling period, thus facilitates the switch to much higher heat transfer transition boiling and nucleate boiling periods earlier to complete the chilldown process faster.

Server-Rack Air Flow and Heat Transfer Interactions in Data Centers

2007 ◽  
Author(s):  
S. P. Tan ◽  
K. C. Toh ◽  
Y. W. Wong
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Data Center ◽  
Vertical Plane ◽  
Pressure Profile ◽  
Design Data ◽  
Flow And Heat Transfer ◽  
Pressure Profiles

The current study focuses on modeling the server-rack airflow and heat transfer interaction in a data center. In a typical computing facility, the computing requirements are often gradually built-up. For example, in this instance, two servers are placed in a rack designed for a six-server stack. Each server will be separately modeled to the required specifications, and also so that their numbers and placement can be changed. The mass flow rate through the server is determined by examining how pressure profiles develop at the inlet and outlet. This mass flow rate then becomes the input into the rack model. The air inflow temperatures at the front and rear grills were obtained from experiments. The pressure profile into and out of the servers were extracted from the rack model and substituted back into the server model. Iteration continues till an acceptable level of convergence is obtained. To validate the models, experiments were carried out using thermocouples arranged in a 3 × 3 grid on a vertical plane between the exit of the server and the rear cabinet wall of the rack. The results showed that the modeling had captured the essence of the flow and heat transfer interaction. The temperature and pressure profile at the rack inlet and outlet, although in a segmented form, have performed adequately to obtain a good approximation of the flow and temperature distribution within the server/rack. The methodology of passing parameters at the server-rack level using a segmented pressure profile has been established. A similar rack-room level interaction will subsequently be developed. In essence, the methodology is equivalent to replacing the server in the rack and the rack in the room with combined flow network - thermal models. But because of the coupled nature of these two different length scale systems, the models are obtained through an iterative process. The approach enables various combinations of servers and racks to be studied quickly for any undesirable effects of off-design data center operation or layout.

Charging and discharging characteristics of sensible energy storage system with multiple cylindrical passages

2021 ◽  
pp. 1-12
Author(s):  
Ravi Kumar ◽  
Anil Kumar Patil ◽  
Manoj Kumar
Keyword(s):  
Energy Efficiency ◽  
Energy Storage ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Storage System ◽  
Thermal Characteristics ◽  
Energy Storage System ◽  
Transient Temperature ◽  
Inlet Temperature

Abstract Sensible energy storage systems can be integrated with domestic and industrial systems to fulfill energy needs in the absence of an energy source. The present study experimentally investigates the thermal characteristics of a sensible energy storage system with multiple cylindrical passages during the charging and discharging cycles. Transient temperature distribution, energy storage, energy release, charging/discharging energy efficiency are evaluated by varying the mass flow rate of air from 0.022 to 0.031 kg/s and inlet air temperature from 45 to 75 oC. The maximum charging energy efficiency of 81.3% was found at 55 oC inlet temperature and 0.031 kg/s of the mass flow rate of air. The maximum discharging energy efficiency is found to be 74.3% corresponding to 45 oC inlet temperature and 0.031 kg/s of the mass flow rate of air.

A new method of flow blockage collapsing in the horizontal pipe: the pipe-rotation mechanism

2020 ◽  
Vol 18 (8) ◽  
Author(s):  
Shaohua Feng ◽  
Wenguang Jia ◽  
Jinglu Yan ◽  
Chuanwei Wang ◽  
Kerui Zhang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
New Method ◽  
Pneumatic Conveying ◽  
Horizontal Pipe ◽  
Severe Problem ◽  
Flow Blockage ◽  
Pipe Rotation

AbstractIn dense pneumatic conveying, flow blockage is a severe problem in the horizontal pipe, so accelerating the collapse velocity of blockage can improve the efficiency of powder transportation. In this paper, we offered a new method of the pipe-rotation mechanism and focused on the effect of this method on blockage collapse from collapse velocity, mass flow rate, and the change of the particle region. The physical model developed is horizontal pipe-rotation geometry at a uniform rotational speed of 0, 150, 300, 450, and 600 rpm, respectively. Then we used a computational fluid dynamics and discrete element method (CFD-DEM) model to investigate a single slug of particles passing through these geometries. The results show that collapse velocity and the mass flow rate increase with increasing rotational speed, which proves that the pipe-rotation mechanism can accelerate the collapse of flow blockage evidently. Moreover, the pipe-rotation mechanism changes the particle region significantly, which is polarized in the lower half of the pipe. It is trusted that the findings reported in this paper well serve as a helping source for further studies toward dense pneumatic conveying.

scholarly journals Extrusion Characteristics of Thin Walled Tubes for Catheters Using Thermoplastic Elastomer

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1628
Author(s):  
Soonmo Cho ◽  
Euntaek Lee ◽  
Seunggi Jo ◽  
Gyu Man Kim ◽  
Woojin Kim
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Wall Thickness ◽  
Flow Rate ◽  
High Performance ◽  
Thermoplastic Elastomer ◽  
Air Pressure ◽  
Outer Diameter ◽  
Screw Speed ◽  
Thin Walled

As the market for minimally invasive surgery has grown, the demand for high-precision and high-performance catheters has increased. Catheters for the diagnosis and treatment of cardiovascular or cerebrovascular disease mainly use a braided wire tube with a polymer inner liner and outer jacket to improve the pushability and trackability. The outer jacket should have an accurate inner and outer diameter and while maintaining a wall thickness of 150 µm or less. In this study, we designed and manufactured a tip and die capable of extruding an outer jacket with a wall thickness of 150 µm or less using a medical thermoplastic elastomer for manufacturing 8Fr (2.64 mm diameter) thin-walled tubes. The ovality and inner/outer diameters of the tube were studied according to changes in the screw speed (mass flow rate), puller speed, air pressure applied to the lumen, and distance between the quench and head, which are the main variables of microextrusion processes. The screw speed (mass flow rate), puller speed, and air pressure affected the inner/outer diameter of the tube, with screw speed and puller speed having the largest influence on diameter. The air pressure and distance between quench and head had the greatest influence on ovality. The results show the effect of different processing parameters on the characteristics of the extruded tube, which will help to establish a stable extrusion process for the manufacture of outer jackets for braided catheter shafts.

Waterhammer in a Horizontal Pipe Induced by Slug Formation and Rapid Condensation

2013 ◽  
Author(s):  
C. Samuel Martin
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
High Speed ◽  
Fast Response ◽  
Liquid Temperature ◽  
Horizontal Pipe ◽  
Pressure Transducers ◽  
High Speed Data Acquisition ◽  
Liquid Depth

The phenomenon of condensation-induced waterhammer in an ammonia refrigeration system was investigated experimentally. Waterhammer was generated by introducing warm ammonia gas over static subcooled ammonia liquid placed in a horizontal 146.3 mm diameter carbon steel pipe approximately 6.0 m long. By means of fast response piezoelectric pressure transducers and a high speed data acquisition system rapid dynamic pressures were recorded whenever a condensation-induced event occurred. Employing top-mounted diaphragm pressure transducers to sense gas pressure the speed of liquid slugs propagating along the pipe was determined. The occurrence of condensation-induced waterhammer depended upon three major variables; namely, (1) initial liquid depth, (2) liquid temperature, and (3) mass flow rate of warm gas. For given liquid depth and temperature, once the warm gas threshold conditions were exceeded, shocks occurred with greater magnitude as the mass flow rate of warm gas input was increased. With adequate subcooling condensation-induced waterhammer occurred for initial liquid depths ranging from 25% to 95% of internal pipe diameter. The threshold mass flow rate of warm gas necessary to initiate waterhammer was greater as the initial liquid depth was lowered. For numerous tests with sufficient gas mass flow rate a condensation-induced shock occurred at the end cap of the test pipe, generating an acoustic (pressure) wave that propagated at a modified speed of sound toward the gas-liquid interface at the back of the slug. Peak shock pressures could be correlated with the gas mass flow rate for various initial liquid depth and suction pressures and temperatures. As the initial liquid temperature and pressure were increased the hydraulic shocks became lower because of smaller subcooling.

The standard unit mass flow rate of gas-liquid mixtures

2020 ◽  
pp. 13-16
Author(s):  
V.N. Petrov ◽  
◽  
V.F. Sopin ◽  
L.A. Akhmetzyanova ◽  
Ya.S. Petrova ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Liquid Mixtures ◽  
Unit Mass ◽  
Standard Unit

Prediction of Leakage Mass Flow Rate Through Gas Springs

1987 ◽  
Author(s):  
Roberto Bruno Bossio ◽  
Vincenzo Naso ◽  
Marian Cichy ◽  
Boleslaw Pleszewski
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate
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