Auf Basis umfangreicher Messdatensätze experimentell und numerisch validierte Regeln zur optimierten Auslegung von Luft-Erdwärmetauschern

Ein Luft-Erdwärmetauscher (L-EWT) kommt wegen seines niedrigen Energiebedarfs und möglicher guter Aufwandszahlen als umweltfreundliche Versorgungskomponente für Gebäude in Betracht. Dabei ist besonders vorteilhaft, dass ein L-EWT die Umgebungsluft je nach Jahreszeit vorwärmen oder auch kühlen kann. Dem zufolge sind L-EWT zur Energieeinsparung nicht nur für den Wohnhausbau interessant, sondern auch dort, wo immer noch große Mengen an fossiler Energie für die Raumkühlung benötigt werden, im Büro- und Produktionsgebäudesektor. Der Einsatzbereich eines L-EWT liegt zwischen Volumenströmen von 100 m3/h und mehreren 100.000 m3/h. Aus dieser Bandbreite und den instationären Randbedingungen entstehen erhebliche Schwierigkeiten, allgemeingültige Aussagen über das zu erwartende thermische Systemverhalten aus der Vielzahl möglicher Konstruktionsvarianten zu treffen. Hauptziel dieser Arbeit ist es, auf Basis umfangreicher, mehrjähriger Messungen an einer eigens konzipierten Testanlage und eines speziell angepassten numerischen Rechenmodells, Kennzahlen zu entwickeln, die es ermöglichen, die Betriebseigenschaften eines L-EWT im Planungsalltag zu bestimmen und ein technisch, ökologisch wie ökonomisch effizientes System zu identifizieren. Es werden die Kennzahlen elewt (Aufwandszahl), QV (Netto-Volumenleistung), ME (Meterertrag), sowie die Kombination aus v (Strömungsgeschwindigkeit) und VL (Metervolumenstrom) definiert, die zu wichtigen Informationen führen, mit denen die Qualität von Systemvarianten in der Planungsphase bewertet werden können. Weiterführende Erkenntnisse über die genauere Abschätzung von Bodenkennwerten werden dargestellt. Die hygienische Situation der durch den L-EWT transportierten Luft wird für die warme Jahreszeit, aufgrund auftretender Tauwasserbildung, beschrieben. Aus diesem Grund werden alle relevanten lufthygienischen Parameter in mehreren aufwendigen Messkampagnen erfasst und auf pathogene Wirkungen überprüft. Es wird über Sensitivitätsanalysen gezeigt, welche Fehler bei Annahme falscher Randbedingungen eintreten. Weiterhin werden in dieser Arbeit wesentliche, grundsätzliche Erkenntnisse aufbereitet, die sich aus der Betriebsbeobachtung und der Auswertung der umfangreich vorliegenden Messdaten mehrerer Anlagen ergeben haben und für die praktische Umsetzung und die Betriebsführung bedeutend sind. Hinweise zu Materialeigenschaften und zur Systemwirtschaftlichkeit sind detailliert aufgeführt.

Attitudes and behaviour towards food attributes and organic food – a triangular methodological investigation of occasional organic consumers

Organic food is increasingly available in the conventional food retail, where organic products are offered alongside with various other types of products and compete mainly with conventional and the so-called conventional-plus products. The latter are conventional products displaying particular quality attributes on the product packaging, such as ‘no artificial additives’, or ‘from animal welfare husbandry’. Often, these quality attributes also apply to organic products. Occasional organic consumers might prefer such conventional-plus alternatives that are perceived to be ‘between’ organic and conventional products. The overall objective of this PhD thesis was to provide information about the segment of occasional organic consumers. In particular, the thesis focussed on consumer perceptions and attitudes towards the quality of, and preferences for, organic, conventional and conventional-plus products in two countries: Germany and Switzerland. To achieve these objectives, qualitative and quantitative consumer research was combined in order to explore occasional organic consumers’ perceptions and attitudes as well as to observe their preferences and buying behaviour regarding different types of food products: organic, conventional and conventional-plus products. The qualitative research showed that, depending on single criteria, organic production was both positively as well as negatively assessed by consumers. Consumer perception of organic food was found to be highly selective and primarily focussed on the final stage of the particular production process. A major problem is that consumers are still mostly unfamiliar with factors associated with organic production, have a lack of confidence, and often confuse organic with conventional products. Besides this, consumer expectations of organic products are different from the expectations of conventional products. The quantitative research revealed that attitudes strongly determine consumers’ preferences for organic, conventional and conventional-plus products. Consumer attitudes tended to differ more between organic and conventional choices rather than conventional-plus and conventional choices. Furthermore, occasional organic consumers are heterogeneous in their preferences. They can be grouped into two segments: the consumers in one segment were less price sensitive and preferred organic products. The consumers in the other segment were more price sensitive and rather preferred conventional-plus or conventional products. To conclude, given the selective and subjective nature of consumer perception and the strong focus of consumer perception on the final stage of the food production process, specific additional values of organic farming should be communicated in clear and catchy messages. At the same time, these messages should be particularly focussed on the final stage of organic food production. The communication of specific added values in relation with organic products to improve the perceived price-performance-ratio is important since conventional-plus products represent an interesting alternative particularly for price sensitive occasional organic consumers. Besides this, it is important to strengthen affirmative consumer attitudes towards organic production. Therefore, policy support should emphasise on long-term communication campaigns and education programmes to increase the consumer awareness and knowledge of organic food and farming. Since consumers expect that organic food is regionally or at least domestically produced while they less accept organic imports, policy support of domestic and regional producers is a crucial measure to fill the current gap between the increasing consumer demand of organic food and the stagnation of the domestic and regional organic food supply.

Re-Framing Trade

Given the substantial and increasing encroachment of trade agreements into almost every aspect of economic and social life, there is a pressing need for research that provides a more coherent framework for understanding the source and effectiveness of organised labour ’s power and capacity to influence international trade policy. Taking the union protests against the General Agreement on Trade in Services (GATS) as a case study, this research uses core concepts derived from social movement theory to analyse the opportunities that existed for unions to influence these trade negotiations and their capacity to identify and take advantage of such opportunities. Importantly, it adds a power analysis designed to reveal the sources of power that unions draw on to take action. The research demonstrates that even where unions faced considerable constraints they were able to re-frame trade issues in a way that built broad support for their position and to utilise opportunities in the trade negotiation process to mobilise resistance against the GATS and further liberalisation of services. The theoretical framework developed for the research provides conceptual tools that can be developed for improving strategic campaign planning and for analytical assessment of past campaigns. The theoretical framework developed for this research has potential for further application as an analytical and strategic planning tool for unions.

Optimization of Processing Technology for Commercial Drying of Bananas (Matooke)

Summary - Cooking banana is one of the most important crops in Uganda; it is a staple food and source of household income in rural areas. The most common cooking banana is locally called matooke, a Musa sp triploid acuminate genome group (AAA-EAHB). It is perishable and traded in fresh form leading to very high postharvest losses (22-45%). This is attributed to: non-uniform level of harvest maturity, poor handling, bulk transportation and lack of value addition/processing technologies, which are currently the main challenges for trade and export, and diversified utilization of matooke. Drying is one of the oldest technologies employed in processing of agricultural produce. A lot of research has been carried out on drying of fruits and vegetables, but little information is available on matooke. Drying of matooke and milling it to flour extends its shelf-life is an important means to overcome the above challenges. Raw matooke flour is a generic flour developed to improve shelf stability of the fruit and to find alternative uses. It is rich in starch (80 - 85%db) and subsequently has a high potential as a calorie resource base. It possesses good properties for both food and non-food industrial use. Some effort has been done to commercialize the processing of matooke but there is still limited information on its processing into flour. It was imperative to carry out an in-depth study to bridge the following gaps: lack of accurate information on the maturity window within which matooke for processing into flour can be harvested leading to non-uniform quality of matooke flour; there is no information on moisture sorption isotherm for matooke from which the minimum equilibrium moisture content in relation to temperature and relative humidity is obtainable, below which the dry matooke would be microbiologically shelf-stable; and lack of information on drying behavior of matooke and standardized processing parameters for matooke in relation to physicochemical properties of the flour. The main objective of the study was to establish the optimum harvest maturity window and optimize the processing parameters for obtaining standardized microbiologically shelf-stable matooke flour with good starch quality attributes. This research was designed to: i) establish the optimum maturity harvest window within which matooke can be harvested to produce a consistent quality of matooke flour, ii) establish the sorption isotherms for matooke, iii) establish the effect of process parameters on drying characteristics of matooke, iv) optimize the drying process parameters for matooke, v) validate the models of maturity and optimum process parameters and vi) standardize process parameters for commercial processing of matooke. Samples were obtained from a banana plantation at Presidential Initiative on Banana Industrial Development (PIBID), Technology Business Incubation Center (TBI) at Nyaruzunga – Bushenyi in Western Uganda. A completely randomized design (CRD) was employed in selecting the banana stools from which samples for the experiments were picked. The cultivar Mbwazirume which is soft cooking and commonly grown in Bushenyi was selected for the study. The static gravitation method recommended by COST 90 Project (Wolf et al., 1985), was used for determination of moisture sorption isotherms. A research dryer developed for this research. All experiments were carried out in laboratories at TBI. The physiological maturity of matooke cv. mbwazirume at Bushenyi is 21 weeks. The optimum harvest maturity window for commercial processing of matooke flour (Raw Tooke Flour - RTF) at Bushenyi is between 15-21 weeks. The finger weight model is recommended for farmers to estimate harvest maturity for matooke and the combined model of finger weight and pulp peel ratio is recommended for commercial processors. Matooke isotherms exhibited type II curve behavior which is characteristic of foodstuffs. The GAB model best described all the adsorption and desorption moisture isotherms. For commercial processing of matooke, in order to obtain a microbiologically shelf-stable dry product. It is recommended to dry it to moisture content below or equal to 10% (wb). The hysteresis phenomenon was exhibited by the moisture sorption isotherms for matooke. The isoteric heat of sorption for both adsorptions and desorption isotherms increased with decreased moisture content. The total isosteric heat of sorption for matooke: adsorption isotherm ranged from 4,586 – 2,386 kJ/kg and desorption isotherm from 18,194– 2,391 kJ/kg for equilibrium moisture content from 0.3 – 0.01 (db) respectively. The minimum energy required for drying matooke from 80 – 10% (wb) is 8,124 kJ/kg of water removed. Implying that the minimum energy required for drying of 1 kg of fresh matooke from 80 - 10% (wb) is 5,793 kJ. The drying of matooke takes place in three steps: the warm-up and the two falling rate periods. The drying rate constant for all processing parameters ranged from 5,793 kJ and effective diffusivity ranged from 1.5E-10 - 8.27E-10 m2/s. The activation energy (Ea) for matooke was 16.3kJ/mol (1,605 kJ/kg). Comparing the activation energy (Ea) with the net isosteric heat of sorption for desorption isotherm (qst) (1,297.62) at 0.1 (kg water/kg dry matter), indicated that Ea was higher than qst suggesting that moisture molecules travel in liquid form in matooke slices. The total color difference (ΔE*) between the fresh and dry samples, was lowest for effect of thickness of 7 mm, followed by air velocity of 6 m/s, and then drying air temperature at 70˚C. The drying system controlled by set surface product temperature, reduced the drying time by 50% compared to that of a drying system controlled by set air drying temperature. The processing parameters did not have a significant effect on physicochemical and quality attributes, suggesting that any drying air temperature can be used in the initial stages of drying as long as the product temperature does not exceed gelatinization temperature of matooke (72˚C). The optimum processing parameters for single-layer drying of matooke are: thickness = 3 mm, air temperatures 70˚C, dew point temperature 18˚C and air velocity 6 m/s overflow mode. From practical point of view it is recommended that for commercial processing of matooke, to employ multi-layer drying of loading capacity equal or less than 7 kg/m², thickness 3 mm, air temperatures 70˚C, dew point temperature 18˚C and air velocity 6 m/s overflow mode.

Factors affecting choice of financial services among rural consumers: Emerging experiences from Gicumbi District, northern Province in Rwanda

Enhancement of financial inclusivity of rural communities is often recognised as a key strategy for achieving economic development in third world countries. The main objective of this study was to examine the factors that influence consumers’ choice of a rural bank in Gicumbi district of Rwanda. Data was collected using structured questionnaires and analysed using a binary probit regression model and non-parametric procedures. Most consumers were aware of Popular Bank of Rwanda (BPR) and Umurenge SACCO through radio advertisements, social networks and community meetings. Accessibility, interest rates and quality of services influenced choice of a given financial intermediary. Moreover, the decision to open a rural bank account was significantly influenced by education and farm size (p<0.1). These results indicate the need for financial managers to consider these findings for successful marketing campaigns.