Bibliography: leaves 144-152. / viii, 152 leaves. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis describes the construction and process of solution of the differential equations in a mathematical model of heat transfer in domestic dwellings. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 1996

Thesis (Ph. D.)--Drexel University, 2005. / Includes abstract and vita. Includes bibliographical references (leaves 192-204).

The initial stage of the work was a study of an 80 tonne industrial furnace, taking observations, panel water temperature data and samples of slag layers from the sidewalls. This resulted in a simple model of layer formation which explained the observed structures, and also the effect of slag layer thickness on heat losses was examined. However, the complexity and variety of structures found were such that a full series of direct thermal conductivity measurements was deemed impractical, and so a theoretical model to calculate the thermal conductivity of complex structures from the thermal conductivities of it s components was developed. Other aspects of heat transfer both within the furnace and from the furnace interior to the water cooling were also explored. In order to obtain a reliable value of thermal conductivity for the slag component of layer structures, a technique was developed to measure the thermal conductivity of the slag. This consisted of firstly determining a viable route for the production of homogenous samples, followed by the design, construction and refinement of an experimental measuring rig. After a large number of preliminary measurements, a series of thermal conductivity values at temperatures between 300 and 800 °C were measured using operating conditions calibrated against a heat storage brick sample of known thermal conductivity. These results were used to provide the data for the theoretical thermal conductivity model, which was then applied to real structures for which thermal data was available. Comparison of the results showed good correlation. Finally, in the appended case study, the heat loss calculation was applied for various furnace situations to identify the potential heat loss savings that could be achieved by controlling the slag layer thickness and structure, and the financial implications.

No description available.

This project looks at the production of electricity by the CEGB's power stations noting the vast quantities of water required for cooling purposes. The main types of cooling system and the problem of condenser scaling often associated with the use of cooling towers and the evaporative cooling process are described, together with the usual methods of scale prevention/ treatment. The Croydon B power station is entirely dependant on treated sewage effluent for cooling water. A combination of the high total dissolved solids content of sewage effluent and their concentration by evaporative cooling made condenser scaling a particular problem. A novel method was developed, whereby nitrification of ammonia in the cooling water was used to control pH and prevent scaling. The system has been in operation for some twenty years, and this project investigates the effect of the major physical and chemical factors in cooling towers on the nitrification process. Work was carried out on a laboratory scale in a 15 litre culture vessel, a 27000 litre pilot scale cooling tower rig system and in the power station itself. The site of nitrification and the effect of pH, temperature, substrate concentration, flow rates, retention time, packing area and organic loading were investigated Differences in the reactions to these factors in the different scales of experiment were found and explanations attempted. In a power station cooling system the most important factors governing nitrification were felt to be pH, flow rate and area of packing. The results of the tests were used to develop a simple model of the system which could be used as a rapid guide to the degree of nitrification posible in any cooling tower. Finally the feasibility of the use of different sources of ammonia was investigated.

The zone method for analysing radiative heat transfer has been widely applied for furnace modelling, and is extensively reported in the open literature. The main reason for the application of this method lies in the accuracy with which it solves the radiant transfer in hot enclosures. Thus, it is generally the preferred method when it is essential to predict accurately the temperature distribution in the furnace. Its application, however, has been limited in most cases by the need to over-simplify the furnace conditions. These simplifications include the need to modify the furnace shape and zoning arrangement, the load representation, and the simulation of convection. Another significant feature of most applications of the zone method is the restriction of the simulation to steady-state conditions. This Ph.D. project aims to eliminate some of these constraints and, therefore, improve application of the zone method to furnaces. Hence, full transient conditions were simulated for different zone models, which varied in complexity from a single gas zone model to a full 3D multi-zone version. The exchange factors required in the zone method were calculated by a Monte-Carlo method using RADEX, a suitable computer code which enabled the furnace geometry to be accurately represented as well as the load, which could be simulated by a series of individual components instead of a single big slab covering the entire hearth surface area. Two different furnaces were modelled, namely a steel reheating furnace and a heat treatment furnace. Experimental data from production were used to validate the heat treatment system mathematical model. Parametric studies were then performed for both furnaces. The predictions clearly demonstrate the need for multi-zone transient models since the load temperature-history was significantly different from that predicted by a simpler long-furnace model. Another aim of the project was to produce reliable data concerning the convective heat transfer in furnaces. This parameter is often ignored in furnace modelling, or if included has been restricted to a crude single empirical value (usually 5 - 10 W/m2K). This can produce erroneous results in applications where the flame and combustion products temperatures are low, as in heat treatment furnaces. In these cases convection may play a more important role than is currently assumed. A mass transfer technique was employed in order to determine heat transfer coefficients for the heat treatment furnace for a variety of load arrangements and firing conditions. These coefficients which were significantly higher (25 - 45 W/m2K) than the usually assumed crude values were subsequently used in the mathematical models of the furnace performance.

This thesis is concerned with an experimental and theoretical investigation of domestic heat pumps. The development of heat pumps in the 1970's did not meet the original expectations and this thesis examines the reasons why. The items considered included cycling and unsteady conditions created whilst matching the heat pump's output to meet a space heating load. A detailed study was made of the hermetically sealed refrigerant compressor, the heat exchangers, and the refrigerant pressure and temperature control systems. In addition to the conventional heat pump a study was made of the advantages gained from modular designed heat pumps. The application of heat pumps to U.K. dwellings and climatic conditions was studied together with the suitability of thermostatic control. Initial studies were made of the operation of a demonstration unit. This showed how intermittent operation would reduce a heat pump performance and was followed by the development of a computer model which simulated the complete refrigerant circulation system. This allowed a study to be made of a heat pump performance at part load conditions. A computer model of the complete refrigerant cycle was developed which aided in the design and construction of a heat pump which used refrigerant R12. This was followed by the construction of a second test rig using R 134(a). The completed R 134(a) test rig was installed in an environmental chamber which could simulate outdoor weather conditions. Results from the test rigs indicated that the performance was greatly affected by on/off cycling an item that was further investigated.

This thesis presents a new method developed to adapt existing hydronic systems in buildings to take advantage of low temperature district heating (LTDH). The work carried out was performed by extensive use of buildings’ energy modelling, validated through recorded data. Two different case studies were investigated and the dynamic heat demand profiles, simulated for each building, were used to evaluate plate radiators connected to single and double string heating loops. The method considered an optimisation procedure, based on supply and return temperatures, to obtain the required logarithmic mean temperature difference (LMTD). The results of the analysis are presented as the average reduction of LMTD over the heating season compared to the base case design conditions. The developed strategy was applied to a Danish single family house from the 1930s. Firstly it was hypothesised a heating system based on double string loop. Two scenarios were investigated based on the assumption of a likely cost reduction in the end users energy bills of 1% per each 1◦C reduction of return and average supply and return temperatures. The results showed possible discounts of 14% and 16% respectively, due to more efficient operation of the radiators. For the case of single loop system, the investigated scenario assumed a cost reduction in the end users energy bill of 1% per each 1◦C lower reduction of average supply and return temperature. Although low return temperatures could not be achieved, the implementation of the method illustrates how to efficiently operate these systems and for the given scenario a possible discount of 5% was quantified. The method was also applied to a UK small scale district heating (DH) network. The analysis began by assessing the buildings of the Estate having double string plate radiator systems. Assuming a likely cost reduction in the end users energy bills of 1% per each 1◦C reduction of return temperature, the optimisation led to obtain a possible discount in the end users energy bills of 14% with a possible yearly average return temperature of 41◦C, compared to the present 55◦C. Moreover, few improvements in the operation of the heat network were proposed. It was assumed to operate the buildings with underfloor heating systems (UFH) with average supply and return temperatures of 40/30◦C, whereas the ones with plate radiators with the optimised temperatures of 81/41◦C. The results shown that an overall average return temperature of 35.6◦C can be achieved operating the heat network as suggested. This corresponds to a decrease in the average return temperature of 18.6◦C compared to the present condition and to a reduction of 10% in the distribution heat losses. Finally, the lower average return temperature achievable would guarantee a better condensation of the flue gases, improving the overall efficiency of the biomass boiler. This was quantified as a possible reduction of fuel consumption of 9% compared to present conditions.

This research explores technological interventions to reduce energy use in the domestic sector, a notable contributor to the global energy footprint. In the UK elevated challenges associated with renovating an outdated, poorly performing housing stock render a search for alternatives to provide immediate energy saving at low cost. To solve this problem, this thesis takes a holistic design approach to designing and implementing a spatiotemporal heating solution, and aims to investigate experiences of comfort, thermal comfort concepts for automated home heating, users’ interactions and experiences of living with such a system in context, and the underlying utility of quasi-autonomous spatiotemporal home heating. The mixed-methods research process was employed to explore and answer four questions: 1) what is the context within which these home heating interfaces are used, 2) to what extent can spatiotemporal automated heating minimise energy use while providing thermal comfort, 3) how are different heating strategies experienced by users, and 4) How do visibility of feedback, and intelligibility affect the user experience related to understanding and control? Ideation techniques were used to explore the context within which the designs are used with regard to all factors and actors in play and resulted in a conceptual model of the context to be used as a UX design brief. This developed model used mismatches between users’ expectations and reality to indicate potential thermal comfort behaviour actions and mapped the factors within the home context that affected these mismatches. Potential user inclusion through participatory design provided stakeholder insight and interface designs concepts to be developed into prototypes. The results of a prototype probe study using these prototypes showed that intelligibility should not be an interface design goal in itself, but rather fit in with broader UX design agenda regarding data levels, context specificity, and timescales. Increased autonomy in the system was shown not to directly diminish the experience of control, but rather, control or the lack of originated from an alignment of expectations and reality. A quasi-autonomous spatiotemporal heating system design (including a novel heating control algorithm) was coupled with the design of a smartphone interface and the resultant system was deployed in a low-technology solution demonstrating the potential for academic studies to explore such automated systems in-situ in the intended environment over a long period of time. Assessment of the novel control algorithm in an emulated environment demonstrated its fitness for purpose in reducing the amount of energy required to provide adequate levels of thermal comfort (by a factor of seven compared with EnergyStar recommended settings for programmable thermostats), and that these savings can be increased by including occupants’ thermal preference as a variable in the control algorithm. Field deployment of that algorithm in a low-tech sensor-based heating system assessed the user experience of the automated heating system and its mobile application-based control interface, as well as demonstrated the user thermal comfort experience of two different heating strategies. The results highlighted the potential to utilise the lower energy-use “minimise discomfort” strategy without compromising user thermal comfort in comparison to a “maximise comfort” strategy. Diverse heating system use behaviours were also identified and conceptualised alongside users’ experiences in line with the developed conceptual model. A rich picture analysis of all previous findings was utilised to provide a model of the design space for home automated heating systems, and was used to draw interface design guidelines for a broader range of home automation control interfaces. The work presented here served as important first steps in demonstrating the importance of assessing UX of automated home heating systems in situ over elongated periods of time. Novel contributions of (i) conceptual model of automated systems’ domestic context and thermal comfort behaviours within, (ii) nudging this behaviour by selecting a “minimise discomfort” heating strategy over “maximise comfort”, (iii) using UX to influence user expectations and subsequently energy behaviour, and (iv) inclusion of thermal preference in domestic heating control algorithm were all resultant of examining naturally occurring behaviours in their natural setting. As such, they are important exploratory discoveries and require replication, but provide new research directions that would allow reduction of domestic energy use without compromise.

Worldwide energy demand in buildings represents about 40-50% of the total energy consumption. In hot climates, such as Middle East and North Africa (MENA) countries, about 30% of the national power demand is used for HVAC applications in buildings. This has led to escalation in power demand in buildings for indoor air-cooling and high energy bills. This is exacerbated further by the widespread adoption of energy intensive and commercially dominant vapour compression air conditioning systems as the technology of choice. This research aims to address the potential of novel designs of evaporative cooling systems for space cooling and thermal comfort in buildings with reduced water and energy consumption, and low environmental impact as an alternative to vapour compression where climatically is suitable. High water consumption rates and low cooling effectiveness are some of the issues affecting the performance of existing Indirect Evaporative Coolers (IEC). A new configuration of IEC combining heat pipe heat exchanger and porous ceramic tubes is investigated in this work. The proposed cooler configuration is based on the concept of regenerative IEC system, this system incorporates heat pipes as passive heat transfer elements and porous ceramic tubes as wet medium mounted on the condenser side of the exchanger. The design of the cooler was carried out with consideration for size of the airflows channels, heat pipes for heat transfer, and porous ceramic tubes properties for water evaporation. A mathematical formulation of heat and mass transfer equations was used to develop a computer model to design and optimise the cooling system. Furthermore, a test rig was built to test a laboratory scale cooling unit, evaluate the performance and validate the simulation. The simulation results reveal that the Wet-bulb (WB) effectiveness of the cooler ranged from 0.524 to 1.053, the COP ranged from 6.33 to 17.01, and water consumption rates of the cooler were around 0.875-1.55 (l/kWh) of cooling capacity. Whereas, the experimental performance parameters of the cooler show the WB effectiveness was in the range of 0.422-0.908 for all test conditions, the COP was 4.62-13.16, and water consumption rates varied 0.841-2.82 (l/kWh) of cooling capacity. A good agreement was obtained between the experiments data and numerical results, the maximum errors between measured and computed results was around 3.94% and 4.51% of supply air temperature and humidity, respectively, while the discrepancy was in the range of 8.67-12.90% of the WB effectiveness. The impact of operational and design parameters on the cooler performance was evaluated in a parametric study using the developed numerical model. It was found that increasing the inlet air temperature, decreasing the inlet air flow rate, and/or increasing the working-to-inlet air flow ratio, results in improving the effectiveness and supply air temperature. Whereas, increasing the inlet air wet-bulb temperature depression, increasing the inlet air flow rate, and/or minimising the working-to-inlet air flow ratio leads to enhancing the cooling output and COP of the cooler. Additionally, increasing the thickness and/or the radius of ceramic tube causes a decline of cooler thermal performance. Therefore, it is recommended to operate the cooler at inlet air velocity of 2-2.5 m⁄s, 50% flow ratio of working-to-inlet air, and inlet air relative humidity below 35% for best results of supply air temperature, WB effectiveness, and COP. Whereas, for desert climate conditions, it is recommended to increase the number of heat pipe rows to 20 to insure sufficient cooling effectivity and performance that meet comfort levels. Finally, a brief economic assessment of the cooler annual operational performance for a case study was carried out, this IEC system provide sufficient cooling effectiveness to the conditioned space with significantly low power consumption compared to traditional air conditioner with annual saving of 77.60% of operational costs, and also substantially contribute to minimise CO2 emissions by saving about 86% of electricity consumption.