Flow Rate Of Liquid Nitrogen Research Articles

Two-phase flow characteristics of cryogenic propellant in filling the head cavity of liquid rocket engine

The filling of the head cavity downstream of the valve with liquid oxygen in a cryogenic rocket engine is a crucial stage in ignition. The work presented here intends to study the two-phase flow characteristics in the head cavity through visualization experiments and simulations, which are carried out using liquid nitrogen as the substitution fluid. The geometry used comes from the scaling of the actual head cavity in the engine. The temperature of liquid nitrogen (TLN2,s) supplied for the head cavity is higher than the saturation temperature in the head cavity (Tsat,c) with room pressure as the initial state, which is proved in the pro-cooling pipeline upstream of the valve before the filling process. Flash boiling is inevitable due to the sudden drop in pressure after the valve is opened. Then, the pressure in the head cavity rises in two steps. The production of gaseous nitrogen leads to the first step, and the mist flow is visualized because liquid nitrogen is broken up and carried by gaseous nitrogen in the form of droplets. The increase in the content of liquid nitrogen in the head cavity causes the second step, and the bubbly flow occurs as the gaseous nitrogen is dispersed as small bubbles in the continuous liquid nitrogen. The transition from mist flow to bubbly flow is led by the decrease in the superheat of liquid nitrogen (ΔT = TLN2,s- Tsat,c). The transition occurs at ΔT = 4 K ∼ 5 K and the minimum achievable superheat is 1.3 K when the mass flow rate of liquid nitrogen supplied is 5.4 kg/s ∼ 6.9 kg/s. Furthermore, the gas nitrogen content in the head cavity is mainly determined in the first step of the pressure rise. Reducing the temperature of liquid nitrogen supplied can weaken the flash boiling, and increase the content of liquid nitrogen in the head cavity.

LNG 기화열을 이용한 수조 수온 냉각성능에 관한 실험적 연구

In this study, a heat transfer performance experiment was conducted by experimentally testing the vaporization process of liquefied natural gas (LNG) using a seawater vaporizer and the process of supplying cooled seawater to the aquaculture tank. By using liquid nitrogen instead of LNG, we experimentally analyzed changes in tank water temperature according to changes in liquid nitrogen supply mass flow rate, water supply mass flow rate, and injection angle of the aquaculture tank nozzle. When testing was conducted by fixing the water mass flow rate at 0.05 kg/s and changing the liquid nitrogen mass flow rate to 0.0058 kg/s, 0.0075 kg/s, and 0.0092 kg/s, the target temperature of 17°C was reached under the experimental condition of 0.0092 kg/s.
 When the water supply mass flow rate was set to 0.05 kg/s, 0.07 kg/s, 0.08 kg/s, and 0.10 kg/s at the constant mass flow rate of liquid nitrogen of 0.0092 kg/s, the target temperature of 17°C was reached under the experimental condition of 0.07 kg/s. When the angle of the water nozzle was adjusted to 0°, 30°, and 60°, the fastest way to reach the target temperature of 17°C was the 0° experimental condition in which water was injected tangentially to the water tank.

Liquefied Natural Gas Cold Energy Utilization for Land-Based Cold Water Fish Aquaculture in South Korea

A new concept of land-based Atlantic salmon farming utilizing liquefied natural gas (LNG) cold energy is proposed. In this study, laboratory-scale experiments were conducted using liquid nitrogen as a cold energy source to confirm whether the water temperature of a fish farming tank can reach below 17 °C within an hour. In particular, the effects of the mass flow rates of liquid nitrogen (0.0075, 0.01, and 0.0125 kg/s) and water (0.05, 0.1, and 0.15 kg/s) on the cooling performances of water were investigated. The results showed that a higher mass flow rate of liquid nitrogen results in a better water cooling performance. In the case of varying the mass flow rate of liquid nitrogen, it was observed that the mass flow rate of 0.0125 kg/s showed the greatest water temperature difference of 9.10 °C/h, followed by that of 0.01 kg/s (5.88 °C/h), and 0.0075 kg/s (5.06 °C/h). In the case of varying the mass flow rate of water, it was observed that the mass flow rate of 0.05 kg/s showed the most significant water temperature difference of 7.92 °C/h, followed by that of 0.1 kg/s (6.26 °C/h), and 0.15 kg/s (5.53 °C/h). Based on the experimental results of this study and the water cooling heat source by an LNG mass flow rate of 220.5 kg/s, the estimated production capacity of Atlantic salmon was approximately 14,000 tons, which is 36.8% of that of imported salmon in South Korea.

Vitrification by Transient Vacuum Flashing Spray Cooling of Liquid Nitrogen

BACKGROUND: The transient vacuum flashing spray cooling of liquid nitrogen (LN2 ) on a microstructured surface can provide ultra-fast cooling rate and may improve cell survival rates. OBJECTIVE: To utilize flashing spray cooling of LN2 instead of film boiling to improve further cell vitrification. METHOD: This study analyzed the effects of the three key parameters (flow rate of liquid nitrogen, ambient pressure, and spray distance) on the cooling process by experimentation. RESULTS: The experimental results showed that the vacuum flashing spray cooling of LN2 can gain higher cooling rates than that achieved by film boiling in conventional vitrification methods. The three parameters all affected the vacuum flash evaporation spray cooling of LN2, and their effect trends were not monotonous but followed a parabolic trend that increased and then decreased. That is, the three parameters all have optimum values to the cooling process. CONCLUSION: Vacuum flash evaporation spray cooling can develop the ultra-fast cooling rates needed to enhance cell vitrification.

Характеристики охлаждения ракетного топлива жидким азотом в емкостях наземных комплексов с теплообменной рубашкой

The authors developed dedicated computational techniques and combined those with numerical simulation of heat transfer processes in ground complex tanks equipped with heat exchange jackets to discover the specifics of how rocket fuel may be cooled with liquid nitrogen used to sparge antifreeze in the cavities of the heat exchange jackets. The paper provides estimation data for rocket fuel cooling efficiency as a function of mass flow rate of liquid nitrogen for various options of setting up fuel mixing in the storage tank during cooling.

Experimental study on power generation plant of a 1 kW small‐scale Organic Rankine Cycle system using R290

AbstractThis work presents an experimental investigation of a small‐scale cryogenic Organic Rankine Cycle (ORC) power generation plant for cold energy utilization using scroll expander and R290. The fresh water and liquid nitrogen were used as heat source and heat sink, respectively. Furthermore, expander gross output power and isentropic efficiency, system thermal efficiency, and cold energy utilization efficiency were calculated as a principle to evaluate the overall system performance. The experimental results demonstrate that increasing pressure drop and heat source temperature will benefit the system performance in some extent, and the pressure drop exhibits a relative sensitivity to heat source temperature about the system performance. Moreover, the expander gross output power will get the peak value while the heat source and heat sink in the best matching. When the mass flow rate of liquid nitrogen at 120 kg/h, optimum pressure drop is 1.02 Mpa, and the corresponding expander gross output power, thermal efficiency, and cold energy utilization efficiency were 638.2W, 0.0586, and 0.0976, respectively. The optimum heat source temperature is 50℃ under liquid nitrogen mass flow rate of 120 kg/h, and the corresponding expander gross output power, thermal efficiency, and cold energy utilization efficiency were 674.2 W, 0.0594, and 0.099, respectively.

Parametric effect and taguchi optimization of cryogenic treatment of OHNS steel

The cryogenic treatment was played an essential role in fabrication of products with high quality and improved substance properties. The present experimental work has to improve the substance properties of Oil Hardened Non Shrinkage (OHNS) steel. Through conventional treatment, there was no possibility to increase the substance properties of steel. In cryogenic treatment process, the OHNS steel was processed under −190 °C. The cryo processor was used to treat the OHNS steel. The substance properties such as hardness and wear rate was measured through the variation of cooling rate, flow rate of liquid nitrogen and holding time. The desired optimal factors were achieved through taguchi method. The role of factor and its effect has been studied through variance test.

Development of one-axis controlled bearingless motor and its application to a centrifugal pump for extremely low temperature

In this paper, a centrifugal pump for for extremely low temperature was fabricated and evaluated by experiments in liquid nitrogen. The pump is using a bearingless motor and permanent magnet bearings to levitate and rotate the rotor without lubricating oil. The difference from the conventional study is that a one-axis controlled bearingless motor is used to reduce the magnetic bearing cost and that the bearings are installed in the liquid to eliminate a shaft-seal. Stable levitation and rotation of the rotor were confirmed in the rotation and pump experiments in liquid nitrogen. In pump experiment, the flow rate of liquid nitrogen was measured at 1 cm in a pumping height. The maximum flow rate was 1.3 L/min when the rotation speed is 1,800 rpm.

Optimum design of cryogenic pump for circulation cooling of high temperature superconducting cables

Pressure drops and temperature rises caused by the cooling with liquid nitrogen are evaluated for two typical examples of HTS cables. One is the three-in-one-type AC cable located inside a corrugated pipe, and the other is the single-core-type DC cable located inside a straight pipe. The theoretical expressions of pressure drop and temperature rise indicate the contributions from three components such as the friction between the liquid nitrogen and the wetted surfaces, the ratio of the heat input to the mass flow rate of liquid nitrogen and the vertical change of position along the cooling pipe. The numerically estimated results are validated by comparing them with the test results carried out by the other groups. Furthermore, the maximum feeding distance of HTS cable can be determined by adjusting the flow rate of pump if the maximum permissible pressure drop and temperature rise are fixed in advance.

Effect of cryogenic cooling and tool wear on surface integrity of turned Ti-6Al-4V

The aim of this work is to investigate the influence of flank wear and cutting fluid (emulsion vs. liquid nitrogen) on surface integrity in turning of titanium alloy Ti-6Al-4V. Longitudinal turning tests with pre-worn uncoated cemented carbide inserts are performed, after which the surface and subsurface layer of machined workpieces is studied. Results for residual stresses on the surface as well as in depth profiles, obtained by X-ray diffraction, are also presented. Scanning electron microscopy (SEM) is used to investigate the microstructure of the workpieces. The same tool holder was used for both cooling conditions, with the same nozzle configuration. The flow rate of liquid nitrogen was therefore limited and as a result, tool wear development was observed to be faster for cryogenic cooling than emulsion-based flood cooling. However, the results show limited differences in terms of achievable residual stresses when comparing cryogenic and conventional cooling at similar levels of tool wear. Despite an increase in tool wear rate, the cryogenic cooling conditions thus provide similar surface integrity results as emulsion cooling. The results suggest that the consumption of the cryogenic coolant can be reduced or optimized without a significant impact on surface quality.

Numerical modeling and analytical modeling of cryogenic carbon capture in a de-sublimating heat exchanger

Both a numerical and analytical model of the heat and mass transfer processes in a CO2, N2 mixture gas de-sublimating cross-flow finned duct heat exchanger system is developed to predict the heat transferred from a mixture gas to liquid nitrogen and the de-sublimating rate of CO2 in the mixture gas. The mixture gas outlet temperature, liquid nitrogen outlet temperature, CO2 mole fraction, temperature distribution and de-sublimating rate of CO2 through the whole heat exchanger was computed using both the numerical and analytic model. The numerical model is built using EES [1] (engineering equation solver). According to the simulation, a cross-flow finned duct heat exchanger can be designed and fabricated to validate the models. The performance of the heat exchanger is evaluated as functions of dimensionless variables, such as the ratio of the mass flow rate of liquid nitrogen to the mass flow rate of inlet flue gas.

Application of a liquid nitrogen direct jet system to the extinguishment of oil pool fires in open space

Liquid fuel fires occurring during industrial processes are serious safety concerns around the world due to their devastating impact on lives, the environment and property. In this study, a liquid nitrogen delivery system was set up to extinguish the oil pool fires in open space. Effects of liquid nitrogen flow rate, pipe diameter, and liquid nitrogen release distance on the suppression process were analyzed according to the mass loss, burning rate and temperature variations. When liquid nitrogen release distance was 0.50 m and pipe diameter was 0.04 m, fire extinguishing time was the shortest 1.6 s and the temperature decrease rate above the liquid fuel surface reached 275°C/s. Fuel surface cooling and blow off process were revealed through the experiments as two kinds of fire extinguishing mechanisms. Based on the flame images captured by high speed camera, the flame expansion phenomenon might occur early in liquid nitrogen injection, especially the situation of the higher flow rate of liquid nitrogen. Three approaches (ground fixed system, moving transportation, and directional transportation of liquid nitrogen) are provided for fire extinguishment of large scale fires. The results obtained provide important reference for the conduct of fire extinguishment for fires. © 2016 American Institute of Chemical Engineers Process Saf Prog 36: 165–177, 2017

Theoretical analysis and experimental investigation on performance of the thermal shield of accelerator cryomodules by thermo-siphon cooling of liquid nitrogen

Five beam line cryomodules with total 27 superconducting Radio Frequency (RF) cavities are installed and commissioned at IUAC to enhance the energy of heavy ion from 15 UD Pelletron. To reduce the heat load at 4.2 K, liquid nitrogen (LN2) cooled intermediate thermal shield is used for all these cryomodules. For three linac cryomodules, concept of forced flow LN2 cooling is used and for superbuncher and rebuncher, thermo-siphon cooling is incorporated. It is noticed that the shield temperature of superbuncher varies from 90 K to 110 K with respect to liquid nitrogen level. The temperature difference can't be explained by using the basic concept of thermo-siphon with the heat load on up flow line. A simple thermo-siphon experimental set up is developed to simulate the thermal shield temperature profile. Mass flow rate of liquid nitrogen is measured with different heat load on up flow line for different liquid levels. It is noticed that small amount of heat load on down flow line have a significant effect on mass flow rate. The present paper will be investigating the data generated from the thermosiphon experimental set up and a theoretical analysis will be presented here to validate the measured temperature profile of the cryomodule shield.

Effect of cryogenic cooling in milling process of AISI 304 stainless steel

The effects of cryogenic cooling on cutting forces in the milling process of AISI 304 stainless steel were investigated experimentally. Cryogenic cooling was achieved by spraying liquid nitrogen to tool, chips and material interfaces using a pipe with an internal diameter of 1 mm; the flow rate of liquid nitrogen was 5.2 L/min; two cutting directions (climbing and conventional milling), two machining conditions (dry and cryogenic cooling) and four cutting speeds (80, 120, 160 and 200 m/min) were used in the milling process. Cryogenic cooling and cutting speed are found to be effective on cutting forces. Cutting forces and torque in cryogenic milling are higher than those in dry milling. Cutting force is increased as the cutting speed is increased. Tool fritter around insert nose radius is the main problem of climb milling method in cryogenic cooling at low cutting speeds.

Cryogenic Design of Termination Cryostat for HTS Power Cable

A high temperature superconducting (HTS) power cable system cooled by forced-circulation subcooled liquid nitrogen is under construction in Korea. In the system, the termination cryostat designed for normal capacity of 22.9 kV, 1.26 kA is located at each end. In order to cool the cryostat effectively, we conducted several numerical analyses. It was found that major design factors were position of inlet and outlet for the liquid nitrogen as well as mass flow rate of the liquid nitrogen in the cryostat. It was also found based on the calculation of temperature distributions in the cryostat that the mass flow rate of liquid nitrogen is needed at least 0.2 kg/s. The cryostat was designed to endure the mechanical stress induced by thermal shrinkage from room temperature to liquid nitrogen temperature. The cryostat is being installed in the 30 m length, prototype single phase HTS cable system.