Airflow pressure losses through rigid metallic and non-metallic flexible ducts were studied and recommendations to improve the rating of flexible ducts were made as part of this study. The testing was done in compliance with ASHRAE Standard 120-1999, Methods of Testing to Determine Flow Resistance of HVAC Air Ducts and Fittings (ASHRAE 1999). Duct sizes of 6", 8", and 10" were tested in a positive pressure, blow-through configuration. An As-Built Test Protocol expands the test configurations specified by Standard 120-1999. Results of the current tests extend the existing ASHRAE/ACCA data for flexible duct which does not include pressure loss data for flexible ducts that are compressed beyond approximately 4%. The data from this study exhibit higher pressure drops than prior ACCA or ASHRAE data. Some configurations exhibit over ten times the pressure loss found in rigid duct or fully stretched flexible duct of the same diameter.

As a result of the rising electrical energy costs in South Africa, a method was sought to reduce the overall electrical consumption of typical shaft systems. A typical shaft configuration was analysed and the primary energy consumers were identified. The ventilation fans for this system were found to consume a total of 15% of the total energy of the shaft system. It was calculated that more than 50% of this energy is consumed by the shaft itself, more specifically by the pressure losses that occur in the shaft as the ventilation air passes through it. It was recognised that there was therefore an opportunity to achieve an energy savings and therefore a costs savings in the total cost of operating a shaft system by reducing the overall resistance of the equipped downcast shaft. However, before any work could continue in this regard, the results noted above required validation. This was achieved though the comprehensive evaluation of the Impala #14 Shaft system. This system was tested and the pressure losses noted in the calculations were verified. In order to ensure that the theory being used was accurate, the next step was to evaluate a number of shafts both from a theoretical perspective by measuring the real shaft pressure losses against time. This was done and a total of five shafts were instrumented and the actual pressure losses over the shaft plotted against time. These shafts were then subjected to a theoretical evaluation using the theory as described by McPherson in 1987. Finally, in order to ensure a thorough understanding of the behaviour of the ventilation air in shaft systems, the systems were simulated using computational fluid dynamic (CFD) techniques. On the whole there was not a good correlation between the tests and either the theoretical calculations or the CFD simulations. This was attributed to the general imperfections in the shaft and the difficulty in obtaining exact values for the drag coefficients of the buntons. These differences highlight the difficulty in modeling the non-homogenous physical environment and providing a factor that can be used to ensure that the theoretical designs are aligned with the physical reality. This factor is approximately 30%. There were also significant discrepancies between the theoretical analysis and the CFD simulation during the initial comparisons. This discrepancy reduced as the complexity of the CFD models increased, until, when the complete shaft was modeled using the full buntons sets, the pipes and the flanges, the difference between the theoretical evaluation and the CFD simulation was small. The result demonstrates that the theory is insufficient and that the inter-related effect of the buntons and fittings has not been fully appreciated. The current theory however has been developed using drag coefficients and interference factors for the buntons sets which have been taken from measurements of similar configurations. This does account for the relative accuracy of the current theory in that there is little difference between the CFD result and that of the theory. However, as the shaft parameters are changed to reflect new layouts and scenarios, it is unlikely that theory will continue to prove accurate. The final phase of the work presented here was to evaluate the cost-effectiveness of using different bunton shapes and shaft configurations. It is shown that: <ul><li> The increase in the pressure losses and therefore the direct operating costs of the shaft can vary by as much as 80%, depending on the bunton configuration chosen.</li><li> The placement of the piping in the shaft can increase the pressure losses and therefore the direct operating costs of the shaft by as much as 12%, depending on the placement of the piping in the shaft; this effect includes the use of flanges. </li><li> The use of fairings on a large cage can reduce the resistance that the cage offers to the ventilation flow by as much as 30%. This, however, does not translate into a direct saving because as the cage moves through the shaft, the overall effect is transitory. </li> </ul> The savings discussed above can be significant when the items highlighted in this work are applied correctly. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Mining Engineering / unrestricted

This thesis focuses on design of device to generate hot air. This generator is supposed to be used to perform thermal tests for a company. Introduction summarizes general knowledge about ventilators, heat transport in air flow, and pressure losses. Main part of the thesis describes development of the generator. Initial design was followed by selection of suitable solution variants, design of major parts of the generator supported by calculations and overall conception of the generator. Final part summarizes the achievements and economic analysis.

The field of microfluidics has the potential to provide a number of products to better everyday life, but is still not well understood. In previous research performed in the field, microfluidics has been shown to exhibit behavior different from what would be expected through normal pipe flow theory. While some research has shown that fluid flow through microchannels does conform to the theoretical flow mechanics, and thus can be predicted and understood through use of well-known relations; other research performed has indicated that fluid flow through microchannels experiences higher or lower pressure losses than would be expected with macro scale theory. This work strives to further explore and explain this anomaly by focusing on simple straight rectangular channels of varying hydraulic diameters from 24 µm to 88 µm, in order to form a more basic understanding for fluid flow in microchannels. Water was pumped through each of these channels at a number of different flow rates, and the static pressure was measured in two locations, a set length apart. The measured pressure loss over this length for each flow rate was then recorded and analyzed to provide relations between pressure loss and hydraulic diameter. Through the data obtained in this study, microfluidic flow of Reynolds numbers greater than 40 and in channels as small as 48 µm in diameter experienced pressure losses predicted from macroscale theory. Below these values, the data was more random, but still showed some conformance to theory. A clear relationship between measured pressure loss and hydraulic diameters over the entire range of channels was also found for two different flow rates. It is hoped that the data obtained will provide a better understanding of microfluidics and pave the way for potential applications to be realized.

Given the surmounting disagreement amongst researchers in the area of liquid flow behavior at the microscale for the past thirty years, this work presents a fundamental approach to analyzing the pressure losses experienced by the laminar flow of water (Re = 7 to Re = 130) through both rectangular straight duct microchannels (of widths ranging from 50 to 130 micrometers), and microchannels with sudden expansions and contractions (with area ratios ranging from 0.4 to 1.0) all with a constant depth of 104 micrometers. The simplified Bernoulli equations for uniform, steady, incompressible, internal duct flow were used to compare flow through these microchannels to macroscale theory predictions for pressure drop. One major advantage of the channel design (and subsequent experimental set-up) was that pressure measurements could be taken locally, directly before and after the test section of interest, instead of globally which requires extensive corrections to the pressure measurements before an accurate result can be obtained. Bernoulli's equation adjusted for major head loses (using Darcy friction factors) and minor head losses (using appropriate K values) was found to predict the flow behavior within the calculated theoretical uncertainty (~12%) for all 150+ microchannels tested, except for sizes that pushed the aspect ratio limits of the manufacturing process capabilities (microchannels fabricated via soft lithography using PDMS). The analysis produced conclusive evidence that liquid flow through microchannels at these relative channel sizes and Reynolds numbers follow macroscale predictions without experiencing any of the reported anomalies expressed in other microfluidics research. This work also perfected the delicate technique required to pierce through the PDMS material and into the microchannel inlets, exit and pressure ports without damaging the microchannel. Finally, two verified explanations for why prior researchers have obtained poor agreement between macroscale theory predictions and tests at the microscale were due to the presence of bubbles in the microchannel test section (producing higher than expected pressure drops), and the occurrence of localized separation between the PDMS slabs and thus, the microchannel itself (producing lower than expected pressure drops).

There is a constant struggle to increase the efficiency in gas turbines, where one method is to have a higher inlet temperature to the turbine. Often, this results in temperatures higher than the critical temperature of the materials, which makes cooling of the components an important part of the turbine. The cooling air is tapped from the compressor, and has hence required work while being compressed, but since it is removed from the thermodynamic cycle it will not provide any work in the turbine stages. Therefore, it is important to understand the losses in the cooling system to be able to use the smallest amount of cooling air possible, while still cool sufficiently to not decrease the turbine’s lifetime. The pressure losses in the cooling and secondary air systems are due to either friction or minor losses; contractions, expansions and bends. The losses can be described by a discharge coefficient, ; a rate of how close the actual mass flow is to the ideal mass flow, or a pressure loss coefficient, ; a rate of the pressure drop. In the cooling and secondary air systems there are orifices and cooling geometries. These can have different geometrical properties depending on application, and thereby have different heat transfer performances and causing a higher or lower pressure drop. At Siemens Industrial Turbomachinery AB, SIT AB, a one-dimensional in-house program named C3D is used for thermal calculations and calculations of flow properties of internal cooling flow networks. The program uses hydraulic networks consisting of nodes and branches to simulate the flow inside the components. Correlations used for describing pressure losses have been collected and divided depending on their valid ranges, with the aim to make pressure loss calculations easier. A MATLAB code have been developed, which, depending on input parameters, separates the correlations and returns a plot with the correlations that can be used. In order to make the code as useful as possible, a few assumptions were made; curve fitting of correlations which were only available as plots and interpolation to get larger valid ranges for some cases. These assumptions will influence the results, but the code will still be able to give an indication of which correlation to use, and hence, the objective is fulfilled. Simulations in one dimension are commonly used, since it is less time consuming than three-dimensional modelling. Therefore, with focus on the pressure losses, a one-dimensional model of a blade in the in-house program C3D has been evaluated using a three-dimensional model in the CFD program Ansys CFX. Also, two new models were created in C3D; both with geometrical properties and pressure loss coefficients adjusted to the CFX model, but the first model is using the same hydraulic network as in the evaluated, reference, model while the second is using a new network, built according to the streamlines in CFX. The resulting mass flows in the C3D models were compared to the mass flows in the CFX model, which ended in the conclusion that it is hard for the one-dimensional models to understand the complex, three-dimensional flow situations, even when adjusting them to the CFX model. Anyhow, the adjustments made the model somewhat closer to the three-dimensional case, and hence CFX should be used in an earlier stage when developing C3D models.

This master's thesis pertains to designing a new heating system in secondary grammar school's building in the city of Vlašim. The old heating system is going to be replaced completely for a new system consisting of panel radiators and distribution piping network made of copper. Thesis includes technical description of old heating system and building itself, calculating of suggested heat efficiency using calculation software TechCON, selection of new panel radiators and appropriate dimensions of piping network , calculation and regulation of pressure losses, description of heat source and inspection of its safety components - expansion vessel and safety valve, determination of system for measurement and regulation as well as calculation of equithermal curves of this system. Last but not least total usage of heat is calculated. Blueprints of heating system are included as well.

The aim of this thesis is to design an air conditioning system of a flat unit in two variants of piping. The piping system of the first floor is installed into the floor in one variant, in the other it is in the ceiling. Data received from measurements within the experiment have been used for the design. The result of the measurement are minor loss coefficient implemented for bending pipes and pressure losses caused by rubbing. These values are used for dimensioning piping variants. Both types of piping are described in the theoretical part and the method of how the experiment had been processed.

The diploma thesis is focused on the design of ventilation and cooling for the family house. The first part of the thesis deals with possibilities of ventilation and cooling, air ducts and their components and selected ventilation units. The next part deals with the analysis of air-conditioning routes, their dimensions and pressure losses. Then the heat gain is determined, and cooling is proposed. The last part deals with the comparison of financial costs for purchase of all components for ventilation and cooling, assembly, installation and operating costs. The enclosed drawings and item lists are at the end of the thesis.

The diploma thesis is focused on a ventilation and cooling design of a family house. Author’s idea was to make summary of theoretical information and project documentation for realization (installation) of the ventilation and cooling. Introduction of the house disposition, theoretical research of a current cooling and ventilation options in residential buildings are parts of this thesis. Next it contains thermal load calculation, two designs of a cooling and three designs of a forced ventilation, dimensioning of the pipelines and financial cost comparison of a purchase, assembly, working and service of a designed systems.