This master thesis project aims to investigate the circumstances of boil-off for heavy vehicle transports, using LNG as fuel, and suggest possible ways of handling these gases otherwise released into the atmosphere. LNG, Liquefied Natural Gas, is when natural gas is cooled below its vaporisation point, turning it into liquid phase which is a much more dense way of storing and transporting the fuel. Trucks running on LNG store their fuel in super insulated tanks, but some heat are transferred to the fuel anyway, causing it to vaporise at a steady rate. During driving of these trucks, this vaporised gas is consumed and the pressure are kept at a certain level of 10 bar. Once the truck is turned off, consumption stops and the pressure starts to increase. After a period of standstill, normally several days, the pressure within the tank has increased to 16 bar where a valve opens to release gas from the tank. This is a safety feature, causing the pressure not to increase further creating hazards. While natural gas, mostly containing methane, is released, fuel is lost and an environmentally unfriendly substance is let out into the atmosphere. This should be avoided, to improve the environmental aspects of using LNG as a fuel for trucks, which most likely will be regulated by laws yet to come. Since the release of boil-off gases rarely should happen during the regular use of these trucks, but a system handling these gases should work at any time and place, a cheap and lightweight unit are to be fitted to these trucks. Equipment already on the truck should be used as much as possible, keeping additional costs and weight low. The only practical way of storing this gas, which is the most resource efficient way of handling these boil-off gases, is to re-liquefy it and transferring it back to the usual LNG tank on the vehicle. The second best option is to consume the gas, making it less environmentally unfriendly. While consuming the gas, as much as possible of its energy should be utilised as electricity and heat. Preferably, electricity should be produced as much as possible, charging the batteries on the truck, decreasing the fuel consumption while running and increasing the lifespan of the batteries. The most efficient way of managing the heat generated is to distribute it to the coolant system on the truck, providing it to the engine and several other components. Distributing the energy is also a matter of safety, as very hot areas otherwise might cause risks of fire. The most simple concept, that is easiest to implement in the near future, is to use a burner similar to the auxiliary diesel heaters fitted to some trucks today. This consumes fuel, generating heat to the coolant system. An additional cooler is needed, to cool of excess heat from the system keeping the temperatures to a certain level. Using this system for an extensive period of time needs an external power supply, since no electricity is generated from consuming the gas. Other technologies that could be used in the future, also generating electricity, is thermoelectric generators and solid oxide fuel cells. These are technologies now being further developed and adapted to the industry of vehicles. These technologies are especially interesting when they are implemented to these trucks for use within other systems as well, for instance utilisation of the heat within exhaust gases. A small scale re-liquefaction unit mounted to the truck is however seen as the most resource efficient solution, making it possible to keep using the gas for it intended purpose of propelling the trucks forward. This technology has to be made more compact, adapting it to the use on a truck.

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.

Rapporté à la tonne de fret, le trafic maritime est un mode de transport relativement « propre ». Néanmoins, par l’intensification des échanges mondiaux, sa part dans les émissions de Gaz à Effet de Serre (GES) au niveau mondial est appelée à augmenter. Conscients des effets néfastes associés aux GES, les pays membres des nations unies, via l’organisation maritime internationale, imposent le cadre réglementaire pour que ce secteur, vital dans une économie mondialisée, demeure écologiquement acceptable. Des objectifs ambitieux sont établis à court (2020) et moyen terme (2050). Or, d’après l’hypothèse faible de Porter, fixer des objectifs environnementaux sans imposer les moyens à mettre en oeuvre favorise l’innovation. Aussi, dans l’industrie du « shipping », les solutions fleurissent au premier rang desquelles figure l’emploi du Gaz Naturel Liquéfié (GNL) en tant que combustible. D’un point de vue thermodynamique, les inévitables infiltrations thermiques à travers les parois des réservoirs cryogéniques entraînent une variation de la pression dans le réservoir et des fluctuations de la qualité du gaz à l’admission moteur. Selon le schéma d’exploitation navire, ces deux phénomènes impactent significativement la pertinence de l’option GNL. En réponse, cette thèse propose un ensemble de modèles 0D pour, à partir d’un profil opérationnel, évaluer :1. l’évolution de la pression dans les réservoirs ;2. l’évolution de la qualité du gaz à l’admission moteur.Dans une première partie, des modèles sont proposés pour simuler les infiltrations thermiques à travers le réservoir, l’évaporation du GNL, son vieillissement (altération des propriétés du gaz par évaporation différenciée des composés) et l’évolution du taux de méthane à l’admission moteur. Puis, les modèles sont assemblés à travers une étude de cas apportée par un acteur du transport maritime. / In proportion to the ton of cargo, shipping is a relatively “clean” transportation mode. Nevertheless, due to global trade intensification, its share in the global greenhouse gas (GHG) emissions should increase. Aware that GHG adverse effects are a major concern for humanity, united nation member states impose, via the international maritime organization, a regulatory framework so that this vital sector in a global economy remains sustainable. Short (2020) and medium (2050)-term goals are set. According to the weak version of Porter’s hypothesis, strict environmental regulations encourage innovations. Hence, in the shipping industry solutions flourish among which the use of Liquefied Natural Gas (LNG) as a fuel. On a thermodynamic basis, the unavoidable heat leaks into the cryogenic tanks cause variations of the tank pressure and the natural gas quality at engine inlet. Depending on the ship’s operational profile, those two phenomena will impact significantly the LNG as a fuel option relevance. One major bottleneck slowing the uptake of LNG as a marine fuel is the lack of methods and models to perform, at a concept design level, the feasibility study. In response, this thesis proposes 0D models to assess from the operational profile:1. the tank pressure evolution;2. the gas quality evolution at engine inlet.In the first part, models are proposed to simulate heat leaks into the tanks, LNG vaporization, ageing (the alteration of natural gas thermophysical properties by a differentiate vaporization of its compounds) and methane number evolution at engine inlet. Then, the models are put together and applied on a case study. The ship concept is proposed by a freight company.

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.

As alternative fuels are becoming more common, technologies need to adjust to them. Natural gas is one of the alternative fuels that has grown during the latest years in the transport sector. Natural gas consists of around 97 % methane and is the cleanest fossil fuel. The use of natural gas can make it easier to transition to biogas as it has equivalent properties. Today Scania CV AB's trucks fuelled by natural gas are using auxiliary cabin heaters driven by diesel. This means that the natural gas trucks have two fuels on-board the truck. The goal of this project is to find a concept to eliminate the diesel fuel and replace it with an auxiliary cabin heater driven by another energy source. It will improve the heating solution and make it superior from an environmental perspective. The result of the project lead to a short-term solution with an auxiliary heater fuelled by natural gas. A long-term solution is to have a cooperation with a manufacturer to develop a better natural gas auxiliary heater that fulfils more of the requirements in the technical specification. An experiment plan is devised to test parameters out of reach of the project.