The development of the so-called Görtler vortices in boundary layer flows over a concave surface leads to strong velocity gradients in both wall-normal and spanwise directions. This determines the flow structures to become more prone to secondary instabilities, which prompt to an early transition from laminar to turbulent flow, ultimately increasing the frictional drag. It is possible to circumvent these secondary instabilities by means of passive or active flow control strategies, with sensors and actuators implemented at the wall. In this thesis, the effect of wall cooling and heating on Görtler vortices developing in supersonic and hypersonic boundary layers is investigated from a numerical point of view. The wall temperature is imposed through a ramping function that decreases or increases an upstream base wall temperature in the streamwise direction. The results show that this type of wall cooling or heating has a mild (adverse) effect on the vortex energy, and a more considerable (but beneficial) effect on the wall shear stress.

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Railway turnout heating is essential during the winter because snow and ice can hinder the movement of the switch. In Sweden, heating has traditionally been done using resistive heating wires mounted to the stock rail, but the technology is outdated and generally exhibits low efficiency and performance. Inductive heating systems such as Indheater, described in this exam work, has in previous studies shown great potential in reduction of the power consumption. Real world data comparing a resistive system and an Indheater system confirms this, with an energy consumption of the latter reaching 37,3 % of the resistive system’s consumption over two winter seasons. To achieve high efficiency and reliability, the heating system control algorithm is important, and during the work described in this report, fault detection was implemented to the programmable logic controller (PLC). Alarms will be triggered if the peak power is too low, which could indicate a heater malfunction. Additionally, detection of faulty switch position sensors and temperature sensors is also described. Given the dynamic nature of the Indheater system, calculations were performed to assess the electrical performance under both balanced and unbalanced load scenarios. Various sizes of phase compensating capacitors were compared. It is recommended to select a capacitor that provides a high power factor for a wide range of different loads, while still reducing the current enough at full load.

Vid val utav uppvärmningssystem för ett småhus är det viktigt att väga in för ochnackdelar, eftersom alla system är bra på olika sätt. Vilket system kommer är mestlämpligt utifrån husets egenskaper och behov?I detta exmenserbete jämförs fjärrvärme, bergvärmepump och frånluftsvärmepump påett utvalt nyproducerat småhus. Resultatet ska baseras på systemets kostnad, livslängd,underhåll och miljöpåverkan.Resultatet har visat att för detta specifika småhus, har frånluftsvärmepumpen varitdominerande i de utförda kalkylerna. / When choosing a heating system for a house it is important to weigh in the different prosand cons, because every system is good in its own way. Which heating system may be ofinterest, depending on the conditions of the house and its requirements?This thesis will compare district heating, geothermal heating and exhaust air heating on aspecific brand new house. The result will base on the heating systems costs, lifetime,maintenance and environmental impact.The result has proven that for this particular house, the exhaust air heating pump hasbeen dominant in the calculations performed.

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This thesis investigates the use of heat pipes for removing heat from flat plate solar collectors and transferring the energy to air in a space heating system. Heat pipes are passive devices which are very efficient at transporting heat energy. They operate using a closed evaporation-condensation cycle. This thesis presents the fundamentals of flat plate collectors, heat pipes, and a set of parameters for evaluating a heat pipe flat collector. Also included are the results of this project and the recommendations for improvements.

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Within the UK, space heating accounts for 66% of the total domestic energy used. New heating controls may offer a means to reduce this figure and help meet the UK s target of reducing its greenhouse gas emissions by 2050. However these technologies will only save energy if occupants are able to use them effectively. Currently, little is known about how occupants interact with their heating systems, in particular how they use the heating within their home and the reasons behind why it is used a specific way. To investigate further, this thesis presents research which used both qualitative and quantitative methods over two separate studies to uncover why and how households heat their homes and how people use their heating system following the installation of new heating controls. The results identify key drivers which impact how people heat their homes and highlight numerous issues preventing them from using their heating how they wish to. A taxonomy of heating use is presented based on the factors influencing heating use in homes and how those factors impact the use and control of the heating system. Occupants use of new heating controls over a ten month period is presented. Manual interaction with controls is separated from programmed heating schedules showing increased manual use over winter and a reliance on heating schedules during shoulder months. The analysis of measured heating use showed similar findings to larger scale studies, however the demanded set-point temperatures were varied and occupants regularly changed heating schedules throughout winter, indicating some of this complexity may be lost by studies inferring heating use patterns from internal temperature measurements alone. The research presented within this thesis is novel, in developing heating characters based on the factors which influence occupants heating behaviours, by presenting measured heating use, which included measured set-point temperatures, heating schedules and heating use duration. The thesis also presented the complexity of heating use within homes uncovered through use of mixed methods.