M.Ing. / In this study, alternative heat pump systems are compared for use in South African climatic conditions. Monthly heating/cooling capacities and coefficients of performance for air, vertical and several horizontal ground-source systems are calculated for Pretoria and Johannesburg. The desired type of heat exchanger is determined by considering economic factors such as the total costs, comprised of the capital and operating costs. The cost-effectiveness on investments of each system is calculated, with parameters such as the payback period, net present value and internal rate of return ...

D.Ing. / The heating of water with hot-water heat pumps is extremely energy-efficient. With the refrigerant R-22 hot water temperatures of 60° C to 65° C are possible. However, these temperatures are low in comparison with the temperatures obtained from other methods of water heating, for instance electrical geysers. Should higher water temperatures be obtained, the applications of hot-water heat pumps will increase. This is possible by using a zeotropic refrigerant mixture as working fluid. A R-22 and R-142b zeotropic refrigerant mixture shows exceptional potential in achieving hot water temperatures. The condensing coefficients need to be predicted correctly to optimize the condenser design. Unfortunately, there is a lack of detailed literature available on condensing coefficients for the recommended mass fractions of R-22 with R-142b at condensing temperatures of 60° C or more. Micro-fin tubes perform outstanding in enhancing heat transfer and are widely used to save energy. Unfortunately, there is also a lack of detailed literature on condensing coefficient at the recommended mass fractions of R-22/R-142b refrigerant mixtures condensing in micro-fins, twisted tapes and high fins at temperatures of 60° C or more. In this study condensing coefficients of R-22 and the zeotropic refrigerant mixture R-22 with R-142b were obtained in smooth tubes at mass fractions of 90%/10%, 80%/20%, 70%/30%, 60%/40%, 50%/50%. The experimental data were used to evaluate some of the methods that are commonly used to predict condensing coefficients. Experiments were also conducted at the same zeotropic mass fractions, to compare three different methods of heat transfer enhancement to that of the smooth tubes namely: micro-fins, twisted tapes and high fins. All measurements were conducted at an isobaric inlet pressure of 2.43 MPa. The test sections consisted of a series of eight tubes with lengths of 1 603 mm. The smooth tubes had an inner diameter of 8.11 mm. With the R-22/R-142b zeotropic refrigerant mixture condensing in smooth tubes, it was observed in the sight glasses that a predominantly stratified wavy flow regime exists at low mass fluxes, from 40 kg/m2s to 350 kg/m2s. The refrigerant mass fraction decreased the condensing coefficient by up to a third on average from 100% R-22 to a 50%/50% mixture of R-22 with R142b. A predominantly annular flow regime was observed at mass fluxes of 350 kg/m2s and more. At this flow regime the condensing coefficients were not strongly influenced by the refrigerant mass fraction, decreasing only by 7% as the refrigerant mass fraction changed from 100% R-22 to a 50%/50% mixture of R-22 with R142b. When the experimental data were compared with three methods that are commonly used to predict condensing coefficients it was found that the flow pattern correlation of Dobson and Chato (1998) gave the best predictions for R-22. The Silver (1964) and Bell and Ghaly (1964) method gave the best predictions for the R-22/R-142b mixtures. When the three heat transfer enhancement methods were compared with smooth tubes it was found that micro-fins were more suitable as an enhancement method than twisted tubes or high fins. It was also found that the condensing coefficients and pressure drops decrease as the mass fractions of R-142b increases.

M.Ing. / Deposition of scale on heating surfaces is a major problem in industry as well as households. The scale that forms on the heating surfaces acts as an insulator and results in decreased heat transfer effectiveness . These are two main approaches to prevent or reduce scaling. Although these approaches are claimed to be efficient, there is a need to evaluate or verify their efficacy. This calls for a method which should preferably enable quantitative and rapid evaluation of these techniques in the laboratory. A reliable, rapid and quantitative measurement method which was comprised of stripping the scale from heat exchanger pipes with a 10% acetic acid solution and measuring the Ca concentration in the acid after stripping, was developed. A total of 11 tests, 7 to test the reproducibility, 2 to test a physical water treatment device and 2 to test the effect of zinc, were conducted. The reproducibility amongst different pipes, and amongst different experiments could not be achieved. Attempts to explain the inconsistency through statistical analysis of the data showed that, the inconsistency in the results could partly attributed to chemical differences, particularly changes in calcium concentration and TDS. Metal contamination, particularly zinc could also be responsible for a part of the inconsistency.

M.Ing. / An experimental investigation was conducted into the heat transfer characteristics of horizontal smooth, micro-fin and herringbone tubes during in-tube condensation. The study focused on the heat transfer coefficients of refrigerants R-22, R-134a and R-407C inside the three tubes. The herringbone tube results were compared to the smooth and micro-fin tube results. The average increase in the heat transfer coefficient when compared to the smooth tube was found to be as high as 322% with maximum values reaching 336%. When compared to the micro-fin tube, the average increase in heat transfer coefficient was found to be as high as 196% with maximum values reaching 215%. A new unified correlation was also developed to predict the heat transfer coefficients in a herringbone and micro-fin tube. The correlation predicted the semi-local heat transfer coefficients accurately with 96% and 89% of the data points falling in the ± 20% region for the herringbone and micro-fin tube respectively. The average heat transfer coefficients were also accurately predicted with all the data points for the herringbone tube and 83% of the data points for the micro-fin tube falling in the ± 20% region. The trend of the new correlation also fitted the data accurately and the conclusion was made that the correlation is accurate and could be used successfully in practice.

No description available.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2014. / In this thesis we will establish effective numerical schemes appropriate for the solution of a non-linear partial differential equation modelling heat transfer in one dimensional longitudinal fins. We will consider the problem as it stands without any physical simplification. The main methodology is based on balancing the non-linear source term as well as the application of numerical relaxation techniques. In either approach we will incorporate the no-flux condition for singular fins. By doing so, we obtain appropriate numerical schemes which improve results found in literature. To generalize, we will provide a relaxed numerical scheme that is applicable for both integer and fractional order non-linear heat transfer equations for one dimensional longitudinal fins.

No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. May 27, 2016. / Heat transfer in a wall with temperature dependent thermal conductivity and internal heat generation is considered. We rst focus on the steady state models followed by the transient heat transfer models. It turns out that the models considered are non-linear. We deliberately omit the group-classi cation of the arbitrary functions appearing in the models, but rather select forms of physical importance. In one case, thermal conductivity and internal heat generation are both given by the exponential function and in the other case they are given by the power law. We employ the classical Lie point symmetry analysis to determine the exact solutions, while also determining the optimal system for each case. The exact solutions for the transient models are di cult to construct. However, we rst use the obtained exact solution for the steady state case as a benchmark for the 1D Di erential Transform Method (DTM). Since con dence in DTM is established, we construct steady state approximate series solutions. We apply the 2D DTM to the transient problem. Lastly we determine the conservation laws using the direct method and the associated Lie point symmetries for the transient problem / MT2016

There is considerable evidence to show that obesity is associated with the development of heart failure independent of traditional risk factors. However, clarity is required on the process involved in the transition from obesity-associated left ventricular hypertrophy (LVH) to LV dysfunction. In the present thesis I evaluated the extent to which central obesity explains variations in LV diastolic function at a community level independent of LV mass (LVM), LV remodelling or haemodynamic factors; whether obesity-related increases in LVM exceeding that predicted by workload (inappropriate LVM [LVMinappr] or alternative haemodynamic factors explains variations in LV ejection fraction (EF) at a community level; whether regression of LVMinappr is more closely associated with improvements in EF than LVM or LVM index (LVMI); and whether obesity-associated insulin resistance may explain decreases in LV diastolic function and variations in LVMinappr. Data were obtained in either 626 or 478 participants whom were representative of a randomly selected community sample and in 168 mild to moderate hypertensives treated for 4 months. In 626 randomly selected participants over 16 years of age from a community sample with a high prevalence of excess adiposity (~24% overweight and ~43% obese) after adjustments for a number of confounders including age, sex, pulse rate, conventional diastolic (or systolic) blood pressure (BP), antihypertensive treatment, LVMI and the presence of diabetes mellitus or an HbA1c>6.1%; waist circumference (p=0.0012) was independently and inversely associated with a reduced early-ro-late transmitral velocity (E/A), with similar findings noted for e’/a’ in a subset of 212 participants with tissue Doppler measurements. Waist circumference-E/A relationships persisted even after adjustments for other adiposity indices including body mass index (BMI) (p<0.05-0.005). No independent relationships between adiposity indices and E/e’ were noted (n=212). In contrast to the effects on diastolic function, waist circumference was not correlated with EF (p=0.83). The independent relationship between waist circumference and E/A was second only to age and similar to BP in the magnitude of the independent effect on E/A. The inclusion of relative wall thickness rather than LVMI in the regression equation produced similar outcomes. The inclusion of carotid-femoral pulse wave velocity (PWV), or 24-hour BP as confounders, failed to modify the relationship between waist circumference and E/A. Thus, waist circumference is second only to age in the impact of the independent association with E/A in a community sample with a high prevalence of excess adiposity. This effect was not accounted for by left ventricular hypertrophy or remodelling, 24-hour BP or arterial stiffness. In 478 randomly selected participants from a community sample, waist circumference, but not BMI was independently associated with the homeostasis model assessment of insulin resistance (HOMA-IR). HOMA-IR was inversely correlated with E/A (p<0.0001) and in a multivariate model with adjustments for waist circumference, age, sex, conventional diastolic or systolic BP, diabetes mellitus or an HbA1c>6.1%, regular tobacco use, regular alcohol intake, pulse rate, treatment for hypertension and either LVMI or LV relative wall thickness in the model, the relationship betwreen HOMA-IR and E/A persisted (partial r=-0.13 to 0.14, p<0.005). With further adjustments for either 24-hour systolic or diastolic BP (partial r=-0.11, p<0.05, n=351) or for aortic PWV (partial r=-0.11, p<0.02, n=410), the independent relationship between HOMA-IR and E/A also remained. Therefore, the relationship between indices of an excess adiposity and abnormalities in LV diastolic function may be explained in-part by insulin resistance beyond haemodynamic factors. In 626 randomly selected adult participants from a community sample with a high prevalence of obesity, the strongest independent predictor of LVMinappr was BMI (p<0.0001). With adjustments for LV stress and other confounders there was a strong inverse relationship between LVMinappr and EF (partial r=-0.41, p<0.0001), whilst only modest inverse relations between LVM or LVMI and EF were noted (partial r=-0.07 to -0.09, p<0.05-0.09)(p<0.0001, comparison of partial r values). The independent relationship between LVMinappr and EF persisted with further adjustments for LVM or LVMI (partial r=-0.52, p<0.0001). LVMinappr and LV midwall fractional shortening were similarly inversely related (p<0.0001) and these relations were also stronger than and independent of LVM or LVMI. In conclusion, in a community sample with a high prevalence of obesity, inappropriate LVM is strongly and inversely related to variations in EF independent of and more closely than LVM or LVMI and BMI was the strongest independent determinant of inappropriate LVH. Therefore LVH is a compensatory response to workload, but when exceeding that predicted by workload, as may occur in obesity, is associated with LV systolic chamber decompensation. In 168 mild-to-moderate hypertensives treated for 4 months, although in patients with an LVMI>51g/m2.7 (n=112)(change in LVMI=-13.7±14.0 g/m2.7, p<0.0001), but not in patients with an LVMI≤51g/m2.7(n=56)(change in LVMI=1.3±9.3 g/m2.7) LVMI decreased with treatment; treatment failed to increase EF in either group (1.2±10.8% and 2.7±10.7% respectively). In contrast, in patients with inappropriate LVH (LVMinappr>150%, n=33) LVMinappr decreased (-32±27%, p<0.0001) and EF increased (5.0±10.3%, p<0.0001) after treatment, whilst in patients with a LVMinappr≤150% (n=135), neither LVMinappr (-0.5±23%), nor EF (0.9±10.3%) changed with therapy. With adjustments for circumferential LV wall stress and other confounders, whilst on-treatment decreases in LVM or LVMI were weakly related to an attenuated EF (partial r=0.17, p<0.05), on-treatment decreases in LVMinappr were strongly related to increases in EF even after further adjustments for LVM or LVMI (partial r=-0.63, confidence interval=-0.71 to -0.52, p<0.0001). In conclusion, decreases in LVMinappr are strongly related to on-treatment increases in EF beyond changes in LVM and LVMI. LVH can therefore be viewed as a compensatory change that preserves EF, but when in excess of that predicted by stroke work, as a pathophysiological process accounting for a reduced EF. In 478 participants of a randomly selected community sample with adjustments for waist circumference, age, sex, conventional systolic BP, diabetes mellitus or an HbA1c>6.1%, regular tobacco use, regular alcohol intake, pulse rate, and treatment for hypertension, an independent relationship between HOMA-IR and LVMinappr was noted (partial r=0.14, p<0.002). With further adjustments for either 24-hour systolic BP (partial r=0.11, p<0.05, n=351), aortic PWV (partial r=0.13, p<0.02, n=410), or circumferential LV wall stress (partial r=0.12, p<0.02, n=478) the independent relationship between HOMA-IR and LVMinappr also remained. Thus, the relationship between indices of an excess adiposity and LVM beyond haemodynamic factors may be explained in-part by insulin resistance. In conclusion, the results of the present thesis provide clarity on the process involved in the transition from obesity-associated LVH to LV dysfunction. In the present thesis I demonstrated that an index of central obesity explains a considerable proportion of the variation in LV diastolic function at a community level independent of LVM, LV remodelling and haemodynamic factors; that obesity-related increases in LVM exceeding that predicted by workload (LVMinappr) or alternative haemodynamic factors explains a marked proportion of variations in EF at a community level; that regression of LVMinappr is more closely associated with improvements in EF than LVM or LVM index (LVMI); and that obesity-associated insulin resistance may explain decreases in LV diastolic function and variations in LVMinappr and hence EF. Therefore, studies are warranted to evaluate the impact of interventions that improve insulin sensitivity on obesity-related decreases in LV diastolic function and increases in LVMinappr.

by Wing-Hoi Tam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 95-99). / Abstracts in English and Chinese. / Title --- p.1 / Acknowledgement --- p.2 / Contents --- p.3 / Abbreviations --- p.5 / List of figures --- p.7 / List of tables --- p.9 / Primers and their sequences used in the projcet --- p.10 / Abstract --- p.12 / Introduction / Small heat shock proteins --- p.16 / Human heart sequencing EST project --- p.17 / Small heat shock protein B3 (HSPB3) --- p.18 / The alpha crystallins --- p.18 / Point mutation of a conserved arginine in the alpha-crystallin domain perturbs the overall alpha crystallins structure and function --- p.19 / HSP27 Confers thermotolerance in cells --- p.19 / Chaperone properties of sHSP --- p.20 / In Viro-chaperone function of sHSPs --- p.21 / Does the alpha-crystallin domain necessary for chaperone activity? --- p.21 / Expression HSPB3 in heart diseases patients and in porcine model --- p.22 / Small heat shock proteins in development and differentiation --- p.23 / HSPB3 role in mammalian embryogenesis --- p.24 / Structure of the small heat shock proteins --- p.25 / Crystal structure of a small heat shock protein --- p.25 / Subunit contacts --- p.26 / Muscle is the only tissue that simultaneously expresses all five sHSPs --- p.26 / "Two independent sHSP systems in muscle cells, to serve and to protect" --- p.27 / Methods and Materials / Small scale preparation of plasmid DNA --- p.29 / Large scale preparation of plasmid DNA --- p.29 / Amplification of mouse and rat HSPB3 coding region --- p.30 / Northern Blotting and Hybridisation --- p.31 / Purification of DNA fragments by GENECLEAN --- p.31 / Preparation of competent Escherichia coli for transformation --- p.32 / Transformation of DNA plasmid into competent Escherichia coli --- p.32 / 5´ة Rapid Amplification of cDNA Ends (5´ةRACE) --- p.33 / 3´ة Rapid Amplification of cDNA Ends (3´ةRACE) --- p.35 / Upstream and Downstream Genomic sequence --- p.36 / Isolation of genomic DNA from human tissue --- p.37 / Multiple tissue cDNA panel (MTC) --- p.37 / The yeast two hybrid screenings and confirmation --- p.43 / Isolation of total RNA from human tissues --- p.43 / Automated Sequencing --- p.44 / Alignment of DNA and amino acid sequence --- p.44 / Radiation hybrid mapping --- p.45 / Results / Determination of the foll length of human HSPB3 cDNA by 5' and 3' RACE --- p.46 / Identification of human HSPB3 gene in mouse and rat heart tissues --- p.49 / "Sequence homology between human, mouse and rat HSPB3" --- p.51 / Chromosomal mapping of the HSPB3 gene --- p.60 / Expression of human HSPB3 is not confined to the heart and skeletal muscle --- p.62 / Mouse HSPB3 expression is confined to the heart tissue --- p.65 / HSPB3 genomic PCR of downstream sequence --- p.67 / HSPB3 upstream genomic sequence --- p.67 / No intronic sequences between the open reading frame --- p.68 / The yeast two hybrid screening --- p.71 / HSPB3 can not form dimers --- p.82 / Expression of Prepro-CDD-ANF in human adult and fetal --- p.83 / Discussions / Previously reported sequence HSPL27 is a chimera --- p.87 / HSPB3 monomers do not dimerises --- p.88 / No intronic sequence in the HSPB3 gene --- p.89 / HSPB3 and CDD-ANF may play an important role during stress to the heart --- p.91 / Change of expression pattern of Prepro-CDD-ANF during development --- p.93 / Reference --- p.95