Tank Wall Temperature Research Articles

Liquid hydrogen tank chill and no-vent fill prediction using computational fluid dynamics

Cryogenic tank chill and fill is an important cryogenic fluid management technology that supports and enables many of NASA’s long-duration space missions. For no-vent fill, the receiver tank pressure remains below the supply tank pressure during the entire duration of the fill so that the tank does not require venting. This is especially advantageous for tank fill operations in low gravity where the position of the liquid is not always known and venting the tank may cause loss of propellant by venting liquid. In lieu of expensive tests conducted on-orbit, accurate computational models capable of predicting receiver tank pressure during cryogenic propellant tank fill may be used to reduce system and propellant mass as well as mission risk. However, these numerical models must be validated or anchored to test data. This study presents computational fluid dynamics (CFD) models with conjugate heat transfer that are used to predict a liquid hydrogen tank chill and no-vent fill ground test conducted at Lewis Research Center (now Glenn Research Center) in 1991. The specific test case chosen for model validation implemented an upward-facing jet near the bottom of a cylindrical 34 liter tank. CFD predictions are compared to experimental measurements of tank pressure, fill level, and wall temperature. The CFD results show reasonable agreement to the test data but overpredict the pressure collapse near the end of the fill despite the liquid jet penetrating the liquid-vapor interface.

Improvement of MC method in SAE J2601 hydrogen refuelling protocol using dual-zone dual-temperature model

The MC method has been published in the SAE J2601 refuelling protocol to safely and quickly refuel hydrogen fuel cell vehicles. This article adopts a dual-zone dual-temperature model that distinguishes the hydrogen temperature from the tank wall temperature to replace the dual-zone single-temperature model of the original MC method. A model (0D1D) of lumped parameter gas (0D) and one-dimensional tank wall (1D) is established simultaneously to verify the modified MC method and generate simulation data. A modified formula to the original MC method for calculating final hydrogen temperature is derived, which contains a correction factor K. The formula and coefficients of the correction factor K are determined by fitting the simulated data from the 0D1D model. The correction factor K is expressed in a piecewise function. The formulas of K are relatively complicated, so another simpler correction factor k is derived, which is a linear function. Research shows that the modified MC method extends its applicability to situations of refuelling times <30 s, while the original MC method is unsuitable. In the conditions set in this article of ambient temperature 0 to 40 °C, precooling temperature −40 to −20 °C and initial pressure 2 to 60 MPa, the modified MC method reduces the errors of final hydrogen temperature between the 0D1D model by 2 to 7 °C compared to the original one, thus improving the calculation accuracy of the pressure target and reaching a more accurate state of charge. In a word, the modified MC method improves the accuracy of refuelling control and has positive significance for the operational safety of hydrogen refuelling stations and the driver's refuelling experience.

Research on temperature rise calculation and hot spot temperature inversion method for oil immersed transformer based on magnetic - thermal - fluid

The hot spot temperature of oil-immersed transformer winding is an important factor affecting the aging of material insulation. In this paper, a magnetic field simulation model is established based on the electrical and structural parameters of the oil-immersed transformer, and the loss distribution characteristics of each wall of the transformer core, winding and fuel tank are accurately calculated by using the finite element simulation software. The simulation model of transformer fluid- thermal field is established, the simulation results of transformer thermal field are obtained, and the temperature distribution of oil-immersed transformer core and winding and the flow velocity around it are obtained. According to the simulation results of thermal field, the characteristic temperature measuring points with strong correlation between tank wall and winding temperature were determined. The inversion models of tank wall and winding hot spot temperature were established by using the support vector regression and BP neural network algorithm respectively by central composite design method. The results show that the correlation coefficient of support vector regression algorithm in predicting winding hot spot temperature reaches 0.98, and the relative error between the model predicted value and the real value is less than 8%, which is more accurate than BP neural network. The above research provides the theoretical basis and technical support for real-time monitoring of oil-immersed transformer winding hot spot temperature.

Study on hazards from high-pressure on-board type III hydrogen tank in fire scenario: Consequences and response behaviours

Exploration of thermal performances of composite high-pressure hydrogen storage tank under fire exposure were critical issues to reduce the risk of tank rupture. Three bonfire tests of type III tanks of 210 L-35 MPa with full compressed hydrogen were exposed to a pool fire to study the response behaviours in fire scenarios. Detailed data on the tank wall temperature and inner pressure were presented in this work. Prototype bonfire tests for the type III tank indicated the failure pressure limits amounted to 41.1–41.8 MPa (average 41.4 MPa). Two consequences (rupture and hydrogen blowdown) will be caused when the inner pressure beyond this limits in fire scenario. The loading-bearing capacity of the tank reduced nearly 3 times under the prescribed fire condition when compared to its average burst pressure of 123.5 MPa conducted from the hydraulic burst test. Results also shown that fire resistance rating (FRR, time to rupture) of the three tanks were 784, 666, and 596, respectively. The FRR got shorter when the tank was exposed in the engulfing fire in advance at hydrogen blowdown case.

One-Dimensional Model of a Compact DHW Heat Pump with Experimental Validation

The current work presents a computationally cost-effective numerical model that successfully simulates a heat pump water heater (HPWH) under typical working conditions of dwellings. The model’s main components are a stratified tank and the heat-pump unit. Both systems are coupled, since a good prediction of water temperature is needed to accurately predict the heat-pump performance. Ten thermocouples measured the tank wall temperature. Measurements and simulations were performed under challenging conditions of a heavy stratification. The 190 L tank stratification was successfully modeled employing a 1D model, experimentally adjusted by three tapping cycles, with 6 × 22, 6 × 33, and 3 × 33 L consumptions, covering flowrates of 4 and 6 L/min. Water temperature is obtained with an uncertainty of 2.6 °C while the heat-pump was ON. A black box model has been used to obtain the heat-pump performance out of the external and condenser temperatures. For the analyzed days, the COP estimation presents an uncertainty of only 5.1%. Finally, an application example is included. It was used to simulate six tapping cycles of the European standard for heat pump water heaters testing (EN 16147). The results show the possibilities for heat-pump manufacturers of applying this calibrated model to predict the performance of HPWHs under different conditions.

TEMPERATURE PREDICT OF AERATION TANK WALLS FOR BIOLOGICAL WASTEWATER TREATMENT SUBSYSTEM OF HAMDAN STATION

A heat transfer modeled for predicting the wall temperature of aeration tank in a biological wastewater treatment subsystem of Hamden station is presented. The method to treatment employed depending upon the pollutants in wastewater and extent to which it is desired to eliminate them in order to congregate required standards of water quality. Several heat gain and loss mechanisms concerned to develop of the model of temperature computer includes heat gains through conduction and radiation. While the heat losses referred to convection and radiation. It classified radiation heat transfer and biological reaction as a gained heat, while classifying the rate of evaporation, aerator, and wind velocity as lost heat.&#x0D; This study relied on a previous study, and based on the assumptions that have been identified so that a model development can be obtained to calculate the surface temperature of the wall of the aeration tank in a biological treatment system. The operational, weather and temperature data were to be registered from Iraqi weather forecast- Basra Airport. To obtain reliable results, the model was simulated using the STELLA software v.9.02, which gave accurate results in determining the parameters that affect the tank wall temperature changes. The STELLA software is Model calibration and considers as a dynamics language because of STELLA is software for graphic and dynamic simulation for the wall temperature of aeration tank. The results have shown a good accuracy and increment between the production walls temperatures with average ranged about (0.2 %) of present work. The model shows the sensitivity through set of precious five parameters like organic removal rate, ambient air temperature, wind velocity, air relative humidity, and the wall effective area of the aeration tank

Numerical study of the boil-off gas (BOG) generation characteristics in a type C independent liquefied natural gas (LNG) tank under sloshing excitation

In this paper, a numerical model considering phase change and external heat leakage is established to study the thermodynamic and hydrodynamic of a type C LNG tank under sinusoidal sloshing excitation. The volume of fluid (VOF) method, coupled with the mesh motion treatment, is adopted to predict the movement of the vapor-liquid interface. The sinusoidal sloshing excitation is realized by a user-defined function (UDF). Compared with related fluid sloshing experiments, the feasibility of the numerical model is verified. The numerical results show that the sloshing excitation has great influences on the thermophysical process and the BOG generation of the LNG tank. The effects of different sloshing frequencies and amplitudes on the thermodynamic characteristics of the LNG tank are studied. In addition, the partial damage of the insulation system is also studied, and it is found that the sloshing has little effect on the critical superheat of the tank wall where the insulation layer is partial damaged, but it will delay the increase of the tank wall temperature. This study is significant to deeply understand the thermal behavior of the LNG sloshing and the characteristics of the BOG generation under sloshing condition during the actual marine transportation of LNG ships.

The effects of infill on hydrogen tank temperature distribution during fast fill

The temperature rise of hydrogen tank during fast fill poses challenge on the safety of hydrogen-powered vehicles. Researchers have been continuously looking for methods to mitigate the challenge of overheating. In this paper, we proposed an innovative solution by introducing porous infill in gas tanks to slow down gas-to-wall heat transfer. The porosity of the infill is no less than 97% to maintain the volume capacity of gas tanks. To evaluate the impact of infill heat capacity, we modelled the filling process with a lumped-parameter model and obtained various time-independent temperature evolution curves. Then, we set up a 2D and a 3D finite volume model and investigated the spatial distribution of temperature rise. Four cases with different infill properties were simulated and compared. At the end of the fast fill, the infill resulted in lower tank wall temperature at the cost of higher gas temperature. The combined effect of internal gas temperature and gas-phase effective thermal conductivity largely determines the final temperature distribution. The presence of infill effectively slowed down convective heat transfer, yet overly resistive porous infill may overly slow down the gas flow and result in thermal stratification. Further studies on infill design can be done to seek more effective solutions.

Test Data Analysis of the Vented Chill, No-Vent Fill Liquid Nitrogen CRYOTE-2 Experiments

NASA is interested in developing efficient methods with which to transfer cryogenic propellants to enable future in-space cryogenic propellant vehicles, particularly the cryogenic fuel depot. The process of transferring cryogenic propellants between two vessels in a reduced gravity environment is complicated by the low normal boiling point of cryogens, high propensity for boiling during tank chilldown, and the fact that liquid cannot be transferred with the receiver tank vent valve open to space. This paper presents test data analysis of the liquid nitrogen vented chill, no-vent fill (NVF) experiments on the CRYOTE-2 tank. 53 tests were conducted, and while not originally intended, were performed in a somewhat parametric fashion. Performance between three different injectors are compared, as well as the effect of initial receiver tank wall temperature, receiver tank fluid initial condition, supply pressure, mass flow rate, and trigger point on the NVF process. From in-depth test data analysis, the highest performing injector based on maximizing evaporation heat and mass transfer between droplets and ullage as well as condensation heat transfer at the liquid/vapor interface, was the 3-spray injector.

Evaluation of Dump Tank Coolability in PHWRs During Late-Phase Severe Accident

In some of the older design of pressurized heavy water reactors (PHWRs), such as in Rajasthan Atomic Power Station (RAPS) and Madras Atomic Power Station (MAPS), in case of a severe accident, the debris/corium may cause failure of the dump port of calandria and relocate into the dump tank. The sensible and decay heat of debris/corium makes the heavy water in dump tank to boil off leaving the dry debris in dump tank. The dry debris remelt with time and the molten corium, thus, formed has the potential to breach the dump tank and move into the containment cavity, which is highly undesirable. Hence, as an accident management strategy, water is being flooded outside the dump tank using fire water hook-up lines to remove the heat from corium to cool and stabilize it and terminate the accident progression, similar to in vessel retention. However, the question is “is the molten corium coolable by this technique.” The coolability of the molten corium in dump tank as in the reactor is assessed by conducting experiments in a scaled facility using a simulant material having comparable thermophysical properties with that of corium. Melting of dry debris resting on dump tank bottom marks the beginning of the experimental investigation for present analysis. Decay heat is simulated by a set of immersed heaters inside the melt. Temperature profiles at different locations in dump tank and in the melt pool are obtained as a function of time to demonstrate the coolability with decay heat. Large temperature gradient is observed within the corium, involving high melt center temperature and low tank wall temperature suggesting formation of crust which insulates the dump tank wall from hot corium.

Effect of initial parameter on thermodynamic performance in a liquid oxygen tank with pressurized helium gas

Heat and mass transfer occurs among different species during the pressurization process with helium gas in cryogenic storage tanks, for which detailed investigations are necessary. In this article, the influence of initial parameters on the thermodynamic performance in a liquid oxygen tank is investigated. Both liquid–vapor interfacial evaporation and mass diffusion are considered. Different initial parameters are compared and analyzed. With the initial liquid temperature increasing from 94.0 to 96.0 K, the total phase change quality decreases by 20%. The initial tank wall temperature ranges from 104.0 to 106.0 K, and the final phase change quality increases by 14.01%. With the oxygen component kept constant, the tank pressure rise was reduced by 23.33% and the total phase change quantity increased by 4.25 times with the helium component ranging from 0.00 to 0.20 kg. When the initial tank pressure remained constant by adjusting the species components of the mixture, the tank pressure rise and the total phase change quantity increased by 17.6% and 8.87 times, with the initial helium increasing from 0.00 to 0.50 kg. The present study provides important conclusion that may supply some technique reference for the design of cryogenic propellant systems.

Heat transfer analysis for fast filling of on-board hydrogen tank

The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions, mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper, the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature, hydrogen pressure, tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data, the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.

Numerical solution for thermodynamic model of charge-discharge cycle in compressed hydrogen tank

The safety and convenience of hydrogen storage are significant for fuel cell vehicles. Based on mass conservation equation and energy conservation equation, two thermodynamic models (single zone model and dual zone model) have been established to study the hydrogen gas temperature and tank wall temperature for compressed hydrogen storage tank. With two models, analytical solution and Euler solution for single zone (gas zone) charge-discharge cycle have been compared, Matlab/Simulink solution and Euler solution for dual zone (gas zone, wall zone) charge-discharge cycle have been compared. Three charge-discharge cycle cases (Case 1, constant inflow temperature; Case 2, variable inflow temperature; Case 3, constant inflow temperature variable outflow temperature) and two compressed hydrogen tanks (Type III 25L, Type IV 99L) charge-discharge cycle are studied by Euler method. Results show Euler method can well predict hydrogen temperature and tank wall temperature.

A shortcut method for solving long-term thermal dynamic analysis of aircraft fuel tank by thermal node network analysis and OpenFOAM software

This article addresses a long-term thermal dynamic analysis problem for aircraft fuel tank and the related solution. The new method combines the thermal node network analysis and the finite element numerical calculation based on the OpenFOAM software. Compared to the thermal node network analysis algorithm, the computational precision is significantly improved by numerical calculation on more delicate grid in the solid region. On the other hand, compared to conventional finite element numerical calculation method, the computational efficiency is significantly improved since the liquid level at every moment is determined by the volume integral of every grid along the gravity direction instead of volume of fluid method on the Fluent software and two thermal nodes are used to represent the air and the fuel, respectively, and solve the two-phase heat transfer with the fuel tank by the aid of grid computation of the heat exchange area. Taken a typical fuel tank heated by aerodynamic heat as an example, the results comparing to the volume of fluid calculation by Fluent software show that the computation time is reduced to 10.3%, while the max deviation of the tank wall temperature is kept within 6.5%, which meets the requirements of engineering calculation precision.

Experimental research of heat-mass coupling response of liquid storage tanks

In order to study the coupling response process of the liquid tank under the external thermal attack, experiments were carried out on a vertical cylindrical storage tank by electric heating. The response processes of the tank pressure, the medium temperatures, and the wet and dry tank wall temperatures were monitored in the experiments. The coupling responding process between the evolving characters of the medium temperature and the tank wall temperature, as well as the resulting rising features of the tank pressure were analyzed comprehensively. The results indicated that, on the one side the heat transfers process across and through the tank wall were influenced obviously by the thermal-flow fields of the two phase mediums which differ a lot in the thermal physical properties. On the other side, affected by the temperature rise in the wall, the vapor medium became thermal stratified and overheated with respect to the tank pressure, and the flow regime in the liquid medium would transform from causing stratification to promoting de-stratification affected by the wall boiling phenomenon.

Investigation on no-vent filling process of liquid hydrogen tank under microgravity condition

In order to investigate the no-vent filling performance under microgravity, the computational fluid dynamic (CFD) method is introduced to the study, where a model aiming at filling a liquid hydrogen (LH2) receiver tank is especially established. In this model, the solid and fluid regions are considered together to predict the coupled heat transfer process. The phase change effect during the filling process is also taken into account by embedding a pair of mass and heat transfer models into the CFD software FLUENT, one of which involves liquid flash driven by pressure difference between the fluid saturated pressure and the tank pressure, and the other one indicates and calculates the evaporation–condensation process driven by temperature difference between fluid and its saturated state. This CFD model, verified by experimental data, could accurately simulate the no-vent filling process with good flexibility. Moreover, no-vent filling processes under different gravities are comparatively analyzed and the effects of four factors including inlet configuration, inlet liquid temperature, initial wall temperature and inlet flow rate, are discussed, respectively. Main conclusions could be made as follows: 1) Compared to the situations in normal gravity, the no-vent filling in microgravity experiences a more adequate liquid–vapor mix, which results in a more steady pressure response and better filling performance. 2) Inlet configuration seems to have negligible effect on the no-vent filling performance under microgravity since liquid could easily reach the tank wall and then cause a sufficient fluid-wall contact under any inlet condition. 3) Higher initial tank wall temperature may directly cause a higher pressure rise in the beginning, while this effect on the final pressure is not significant. Sufficient precooling and reasonable inlet liquid subcooled degree are suggested to guarantee the reliability and efficiency of the no-vent fill under microgravity.

Experimental investigation on no-vent fill process using tetrafluoromethane (CF4)

This paper investigates the transfer of liquid cryogens using a no-vent fill (NVF) process experimentally to identify the dominant NVF parameters. The experimental apparatus has been fabricated with extensive instrumentations to precisely study the effects of each NVF parameter. Liquid tetrafluoromethane (CF4) is selected as the working fluid due to its similar molecular structures and similar normal boiling point and triple point with liquid methane which has been considered as an attractive future cryogenic propellant. The experimental results show that the initial receiver tank wall temperature and the incoming liquid temperature are the primary factors that characterize the (non-equilibrium) thermodynamic state at the start of a NVF transfer. The supply pressure is also critical as it indicates the ability to condense vapor in the receiver tank. A non-dimensional map based on energy balance is proposed to find acceptable initial conditions of the filling volume at the desired final tank pressure. The non-dimensional map shows good agreement with the NVF data not only in this paper but also in the previous research.

Analysis of heat transfer and frost layer formation on a cryogenic tank wall exposed to the humid atmospheric air

In this paper heat transfer characteristics and frost layer formation are investigated numerically on the surface of a cryogenic oxidizer tank for a liquid propulsion rocket, where a frost layer could be a significant factor in maintaining oxidizer temperature within a required range. Frost formation is modeled by considering mass diffusion of water vapor in the air into the frost layer and various heat transfer modes such as natural and forced convection, latent heat, solar radiation of short wavelength, and ambient radiation of long wavelength. Computational results are first compared with the available measurements and show favorable agreement on thickness and effective thermal conductivity of the frost layer. In the case of the cryogenic tank, a series of parametric studies is presented in order to examine the effects of important parameters such as temperature and wind speed of ambient air, air humidity, and tank wall temperature on the frost layer formation and the amount of heat transfer into the tank. It is found that the heat transfer by solar radiation is significant and also that heat transfer strongly depends on air humidity, ambient air temperature, and wind speed but not tank wall temperature.

Thermohydraulic behavior of the WENDELSTEIN 7-X magnet system

A quench of the superconducting magnet system of the stellarator fusion experiment WENDELSTEIN 7-X, as well as eddy current heating of the coil housings caused by the subsequent emergency discharge, leads to helium expulsion from the conductor and housing cooling circuits. A simplified numerical analysis of the helium mass flow from the coils to the storage tanks is carried out on the basis of a given worst case quench propagation velocity. For the design of the quench gas relief system a simultaneous quench of all coils is assumed. The quench origins are presupposed to be evenly distributed throughout the coil conductor lengths. The quench gas is collected inside the cryostat by the circular coolant supply manifolds which are scaled up for this purpose. Five expulsion lines around the torus lead from each manifold via safety valves to a warm circular quench gas collector outside the cryostat. From there the helium is transferred to the gas storage tanks. Only a moderate decrease of the tank wall temperature, without cold spots, is achieved.

Heat transfer in hot-zone-forming pool fires

In pool fires of some liquid fuels, the isothermal layer, or “hot zone,” is formed below the burning surface, and increases in thickness with time. Mechanisms of heat transfer in such medium-scale hot-zone-forming pool fires were studied. The distributions of the tank wall temperature and the heat transfer rate between the tank wall and the surroundings (flame, gas above the fuel surface, fuel, and surrounding air or water) in 0.559-m-diameter fuel oil and gasoline pool fires such as reported by Burgoyne et al. were calculated using a finite difference program. The following conclusions were obtained from the calculated results: the heat input and loss of the fuel through the tank wall become sometimes dominantly large, and are never negligible compared with the direct heat input from the flame to the fuel surface; when the tank is cooled with water, the heat loss from the fuel through the wall is so large that the hot-zone thickness decreases gradually; the rate of increase of the hot-zone thickness increases with increasing thermal conductivity and thickness of the tank wall; in pool fires of lower hot-zone temperature, the convective heat transfer from the wall to the fuel is dominantly large at the upper layer of the hot zone; in pool fires of comparatively high hot-zone temperature and low thermal conductivity of the tank wall, the downward current of the fuel near the tank wall must be caused due to the heat loss from the fuel to the tank wall throughout the hot zone.