The study presents a systematic single and two-phase analysis of fluid flow and heat transfer in a liquid hydrogen storage vessel for both earth and space applications.The study considered a cylindrical tank with elliptical top and bottom. The tank wall ismade of aluminum and a multi-layered blanket of cryogenic insulation (MLI) has been attached on the top of the aluminum. The tank is connected to a cryocooler to dissipate the heat leak through the insulation and tank wall into the fluid within the tank. The cryocooler has not been modeled; only the flow in and out of the tank to the cryocooler system has been included. The primary emphasis of this research has been the fluid circulation within the tank for different fluid distribution scenario and for different level of gravity to simulate all potential earth and space based applications. The equations solved in the liquid region included the conservation of mass, conservation of energy, and conservation of momentum. For the solid region only the heat conduction equation was solved. The steady-state velocity, temperature and pressure distributions were calculated for different inlet positions, inlet opening sizes, inlet velocities and for different gravity values. The above simulations were carried out for constant heat flux and constant wall temperature cases. It was observed from single-phase analysis that a good flow circulation can be obtained when the cold entering fluid was made to flow in radial direction and the inlet opening was placed close to the tank wall. For a two-phase analysis the mass and energy balance at the evaporating interface was taken into account by incorporating the change in specific volume and latent heat of evaporation. A good flow circulation in the liquid region was observed when the cold entering fluid was made to flow at an angle to the axis of the tank or aligned to the bottom surface of the tank. The fluid velocity in the vapor region was found to be higher compared to the liquid region. The focus of the study for the later part of the present investigation was the conjugate heat transfer during a confined liquid jet impingement on a uniform and discrete heating source. Equations governing the conservation of mass, momentum, and energy were solved in the fluid region. In the solid region, the heat conduction equation was solved. The solid-fluid interface temperature shows a strong dependence on several geometric, fluid flow, and heat transfer parameters. For uniform and discrete heat sources the Nusselt number increased with Reynolds number. For a given flow rate, a higher heat transfer coefficient was obtained with smaller slot width and lower impingement height.The average Nusselt number and average heat transfer coefficient are greater for a lower thermal conductivity substrate. A higher heat transfer coefficient at the impingement location was seen at a smaller thickness, whereas a thicker plate or a higher thermal conductivity plate material provided a more uniform distribution of heat transfer coefficient. Compared to Mil-7808 and FC-77, ammonia provided much smaller solidfluid interface temperature and higher heat transfer coefficient whereas FC-77 provided lower Nusselt number. In case of discrete heat sources calculations were done for two different physical conditions, namely, when the total input power is constant and when the magnitude of heat flux at the sources are constant. There was a periodic rise and fall of interface temperature along the heated and unheated regions of the plate when the plate thickness was negligible. The average Nusselt number and average local heat transfer coefficient were highest for uniform heating case and it increased with number of heat sources during discrete heating.

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This work presents the use of numerical modeling and simulation for the analysis of transport phenomena in engineering systems including zero boil-off (ZBO) cryogenic storage tanks for liquid hydrogen, refrigerated warehouses, and human-occupied air-conditioned spaces. Seven problems of medium large spaces in these fields are presented. Numerical models were developed and used for the simulation of fluid flow and heat and mass transfer for these problems. Governing equations representing the conservation of mass, momentum, and energy were solved numerically resulting in the solution of velocity, pressure, temperature, and species concentration(s). Numerical solutions were presented as 2-D and 3-D plots that provide more insightful understanding of the relevant transport phenomena. Parametric studies on geometric dimensions and/or boundary conditions were carried out. Four designs of ZBO cryogenic liquid hydrogen storage tank were studied for their thermal performance under heat leak from the surroundings. Steady state analyses show that higher flow rate of forced fluid flow yields lower maximum fluid temperature. 3-D simulation provides the visualization of the complex structures of the 3-D distributions of the fluid velocity and temperature. Transient analysis results in the patterns of fluid velocity and temperature for various stages of a proposed cooling cycle and the prediction of its effective operating term. A typical refrigerated warehouse with a set of ceiling type cooling units were modeled and simulated with both 2-D and 3-D models. It was found that if the cooling units are closer to the stacks of stored packages, lower and more uniform temperature distribution can be achieved. The enhancement of thermal comfort in an air-conditioned residential room by using a ceiling fan was studied and quantified to show that thermal comfort at higher temperature can be improved with the use of ceiling fan. A 3-D model was used for an analysis of thermal comfort and contaminant removal in a hospital operating room. It was found that if the wall supply grilles are closer to the center, the system has better performance in both contaminant removal and thermal comfort. A practical guideline for using CFD modeling in indoor spaces with an effective meshing approach is also proposed.

Shape memory alloys (SMAs) can recover large strains (e.g., up to 8%) by undergoing a temperature-induced phase transformation. This strain recovery can occur against large forces, resulting in their use as actuators. The SMA elements in such actuators integrate both sensory and actuation functions. This is possible because SMAs can inherently sense a change in temperature and actuate by undergoing a shape change, associated with the temperature-induced phase transformation. The objective of this work is to develop an SMA based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulk head arrangement for NASA. The design of the thermal conduction switch is based on a biased, two-way SMA actuator and utilizes a commercially available NiTi alloy as the SMA element to demonstrate the feasibility of this concept. This work describes the design from concept to implementation, addressing methodologies and issues encountered, including: a finite element based thermal analysis, various thermo-mechanical processes carried out on the NiTi SMA elements, and fabrication and testing of a prototype switch. Furthermore, recommendations for improvements and extension to NASA's requirements are presented. Such a switch has potential application in variable thermal sinks to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. The SMA thermal conduction switch offers the following advantages over the currently used gas gap and liquid gap thermal switches in the cryogenic range: (i) integrates both sensor and actuator elements thereby reducing the overall complexity, (ii) exhibits superior thermal isolation in the open state, and (iii) possesses high heat transfer ratios between the open and closed states. This work was supported by a grant from NASA Kennedy Space Center (NAG10-323) with William U. Notardonato as Technical Officer.