A generic simulation of energy consumption of automobile air conditioning systems
- Authors: Konz, Martin
- Date: 2003
- Subjects: Automobiles -- Air conditioning
- Language: English
- Type: Thesis , Masters , MTech (Engineering)
- Identifier: vital:10822 , http://hdl.handle.net/10948/129 , Automobiles -- Air conditioning
- Description: The air conditioning system in a car is, in addition to the heating system, installed to increase the comfort in the passenger compartment. Comfort is not the only reason for automotive air conditioning systems, as road safety also improves with the comfort of the driver, as a pleasant environment reduces driver fatigue. The rising environmental problems and, hence, resulting stringent legislation are forcing the automobile industry to develop cars with ever decreasing fuel consumptions. The question of better fuel consumption and energy utilisation does not stop with the engine and aerodynamics, but is required of the air-conditioning system as well. Thus, incessantly innovative technologies are developed to decrease the energy required by the air-conditioning systems. The interaction of the refrigerant cycle components and the rapidly changing operating conditions of the car (speed, revolutions per minute, etc.) places extensive demands on the control system. In addition, the air-conditioning system is also designed for high ambient temperatures (cool down), but is mostly used in fairly moderate conditions. This operation allows for energy saving control strategies such as externally controlled compressors, blower motor control, etc. The experimental comparison of different air-conditioning systems, components or control strategies is very time consuming and extensive, and the use of an air-conditioned wind tunnel is inevitable when experiments need to be done with reproducible ambient conditions.This, combined with the high costs of installation and operation of a wind tunnel is a major problem. Furthermore, the effect of component or control strategy enhancements should be available as soon as possible in the early stages of design. The above considerations have prompted the rapid development of new powerful simulation tools, but in most cases the simulation tools are focused on one specific component or problem only. A more holistic approach would be to combine the calculations of two or more programs. This implies the adaptation of the model to more programs which leads to a lack of transparency. Obviously, the entire development work cannot be done entirely by simulation, especially in the later phases of the development where it would still be necessary to build prototypes to evaluate the done work experimentally. However, in the early stages of development, it would be advantagous to work without expensive prototypes.
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- Date Issued: 2003
An epidemiological study of childhood asthma care by general practitioners in the Nelson Mandela Metropole
- Authors: Wickens, Nicolas John
- Date: 2003
- Subjects: Asthma in children -- South Africa -- Nelson Mandela Metropole , Epidemiology -- South Africa -- Nelson Mandela Metropole , Physicians (General practice) -- South Africa -- Nelson Mandela Metropole
- Language: English
- Type: Thesis , Masters , MTech (Biomedical Technology)
- Identifier: vital:10825 , http://hdl.handle.net/10948/124 , Asthma in children -- South Africa -- Nelson Mandela Metropole , Epidemiology -- South Africa -- Nelson Mandela Metropole , Physicians (General practice) -- South Africa -- Nelson Mandela Metropole
- Description: The purpose of this study was to measure and evaluate GPs' practices, perceptions, and beliefs with regard to chronic childhood asthma management and to identify GPs' attitudes towards practice guidelines in particular the SACAWG (South African Childhood Asthma Work Group) guideline (Motala et al., 2000). In 2001 a single period cross-sectional survey was conducted among 300 GPs in the Nelson Mandela Metropole (NMM) which comprised the Port Elizabeth, Uitenhage, and Despatch regions. GPs in clinical practice in the NMM were identified from the register of the Health Professions Council (HPC) CD-ROM (2000). The register contains names and professional information on all physicians in South Africa who have completed or in the process of completing requirements to practice medicine. GPs meeting the following criteria were identified: (1) primary self-designated practice specialty of general practice; (2) practice location in Port Elizabeth, Uitenhage, and Despatch areas; and (3) engaged in direct patient care. The HPC register contained listings for 300 GPs that matched the study criteria. Data were collected by means of a structured self-administered questionnaire. Questionnaires with a return envelope were mailed to the GPs' practices. Questionnaires were returned by 89 of the 300 eligible NMM GPs, reflecting a 29,7 % response rate. A 43-item Chronic Childhood Asthma Management questionnaire was developed and validated to assess the delivery of asthma care by GPs in the NMM. Forty-four per cent of the respondents reported performing spirometry on patients with newly diagnosed asthma as part of their initial evaluation. For patients with moderate persistent asthma prescribing of inhaled corticosteroids (ICSs) varied by patient age, with 57,4% of physicians routinely prescribing them for patients < 5 years, compared with 76,5% of physicians prescribing them for patients 5 years. Awareness of the SACAWG guidelines among these GPs was high, with 76,8% reporting that they have heard of the guidelines, and 59,4% reporting having read them. 14,5 per cent of the GPs reported developing written treatment plans for patients with moderate or severe asthma. To achieve the best results with their asthma patients, 68,1% of the physicians reported that patient compliance was imperative, 49,3% reported education as the most important, pharmacotherapy / good products was reported as most important by 29,0% of the group, environmental control was cited by 18,8% of the GPs. Several aspects of the SACAWG guidelines appear to have been incorporated into clinical practice by GPs in the NMM, whereas other recommendations do not appear to have been readily adopted. This information suggests areas for intervention to improve primary care for asthma in the NMM.
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- Date Issued: 2003