A two year experiment demonstrated electrical energy savings through evaporator fan cycling in part of a full-sized refrigerated controlled atmosphere apple storage facility in Yakima, Washington. Room cooling demand and evaporator fan operation was controlled by the bulk fruit temperature. Refrigerant temperature was regulated by a computer controlled ramping sequence and a weighted average of three thermistors rather than a room thermostat. Evaporator fans remained off 60-65% of the time during periods of fan cycling operation. Seasonal average fan energy savings approached 50-55% when the product remained in storage for a typical length of time. Room environment conditions, product mass loss, and fruit quality were not compromised. Bulk fruit temperature was exceptionally stable as compared to fruit stored in non-fan cycled rooms controlled by traditional means. Less fan motor heat input in the fruit storage space also results in compressor energy savings. Total electrical energy savings were projected to an 18 room fruit storage facility implementing computer controlled evaporator fan cycling. Projected electrical energy savings achievable through evaporator fan cycling for the state of Washington were made based on reported apple storage capacity. / Graduation date: 1993

As South Africa's electricity consumption increases, Eskom is promoting Demand Side Management (DSM) to aid control of both the electricity consumption and its more effective usage, thereby delaying the need to construct new power stations, which pose large economic and environmental problems. Eskom has investigated various DSM strategies, such as load shifting, co-generation, alternative fuels and energy efficient processes, and has targeted the areas of load shifting and energy efficiency as prime areas for energy savings as they are relatively inexpensive and easy to implement. Pumps and fans form a large part of the industrial load. By improving the power usage of these devices with the use of variable speed drives, large energy savings may be achieved. To enable the energy usage of industrial loads to be evaluated, a test bed system which enables a variable speed drive to be loaded with a configurable load, was constructed. The test bed system forms a tool for evaluating and demonstrating the energy savings that are possible, by replacing fixed speed drives with variable speed drives when controlling the flow rate of pumps and fans. Results from the test bed system show that by using variable speed operation of pumps and fans, some energy savings are achievable when compared to existing methods of flow control. The achievable energy savings are dependent on the system properties and the duty cycle of the pump or fan system. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

Single leaf in pocket on back end paper. / Bibliography: p. 475-488. / xxviii, 488 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study aims to develop a robust set of tools to model the performance of a range of composite coil configurations, to develop an operational model to predict the steady state performance of single and multizone air conditioning systems and to use the computational model as an exploratory tool to examine the performance of a series of candidate design solutions. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1996?

[Truncated abstract] The subject of fan noise generating mechanisms and its control has been studied intensively over the past few decades as a result of the ever-increasing demand for more powerful fans. A unique feature of fan noise is that it consists of high-level discrete frequency noise related to the blade passing frequency, and low-level broadband noise due mostly to turbulent airflow around the fan. Of the two types of fan noise, the discrete frequency noise is the more psychologically annoying component. Past research into fan noise has shown that the discrete frequency fan noise are dipole in nature and are caused predominantly by the fluctuating lift acting on the surfaces of the fan blades. Based on this, several theoretical models have been established to correlate these fluctuating lift forces to the far-field sound pressure. However, one general assumption in these models is that the fan blades are assumed rigid, and the consequence of such an assumption is that it is unclear if the far-field sound pressure is caused solely by the aerodynamic lift force, or whether the blade vibration also plays a substantial role in the generation of the far-field fan noise. One of the goal of this thesis was thus to experimentally quantify the contribution of blade vibration to far-field fan noise and it was found that blade vibration, whilst coherent with the far-field fan noise, did not contribute significantly. Aside of this, several experiments aimed at filling knowledge gaps in the understanding of fan noise characteristics were also be conducted, in particular, to understand the relationship between far-field sound pressure level to blade lengths as well as the number of blades on the fan. The experiments showed that for fans with many blades, the dependency of the far-field sound pressure on blade length is stronger than fans with less blades. Furthermore, dipole measurements showed that the dipole characteristics of fan noise does not occur only at the discrete frequencies, but also within a range of broadband frequencies, implying that the source for both discrete and broadband is the same. The second section of this thesis deals with the study of vortex shedding and its active control. When a circular cylinder (or any object) is placed in a flow within a specified Reynolds number range, flow separation and periodical wake motion is formed behind the cylinder, which is known as vortex shedding. It has been found in previous research that this wake motion is affected by acoustic field imposed on it via loudspeakers. This suggests that there is a strong acoustic-vortex relationship. However, little of this relationship is understood as conventional methods of studying vortex centre around the use of hot-wire anemometry, which effectively measures the velocity fluctuation in the flow. This thesis is the first in using a microphone to study the acoustic characteristic of the vortex wake, and experimental results shows that the two parallel shear layers of the wake carry the strongest pressure signals at the vortex shedding frequency, whilst the entrapped region between the layers carries the strongest pressure signals at the first harmonic.

M.Ing. / The performance and reliability of induced draft fans are of ever growing concarn in industry, especially in the power generation industry. The reliability and plant efficiency depend on the design conditions of all plant components. Induced draft fans handle high temperature flyash-laden flue gas, and are often plagued by mass-flow deficiencies and excessive vibration in fossil fuel powerplants [1]. In this research an existing induced-draft fan is analysed to investigate the occurrence of high stresses forming on the impeller, as these stresses lead to cracks appearing on the centre plate of the impeller. The basic approach used to address this problem is implementing the Finite Element Method starting with different cantilever beam configurations to simulate the connection of the blade with the centre plate. Geometries are kept constant to facilitate in the practical set-up implementation stage of the dissertation. The practical set-up is used to verify the results obtained from the Finite Element Method program, and it serves as a benchmark test for evaluating the further use of the chosen Finite Element Method program. A simplified Finite Element Method model is presented for the induced draft fan. Static and frequency analyses are done to determine the characteristics of the fan structure. Lastly an advanced dynamic analysis is done on the specific fan. Different ramp force functions are used to simulate different start-up curves for the fan. A conclusion will be drawn from the dissertation, and recommendations will be made for similar future research work.

An array of small, lightweight acoustic sources was investigated to determine how such an arrangement of sources would acoustically interact with a duct similar to that of a turbofan engine inlet. The sources were cylindrically curved aluminum panels excited in vibration by the application of a sinusoidally varying voltage to a piezoceramic actuator bonded to them. The finite element method was used as a design tool to size the panel based on desired vibration characteristics. A boundary element acoustic analysis was used to predict the acoustic output from various arrangements of sources. The central portion of the research was a series of experiments using an array of twelve sources arranged circumferentially in a duct. Measurements of the performance of each source revealed that the performance of the acoustic sources varied from source to source. This variation was assumed to have been caused by differences in the quality of the bond of each of the piezoceramic actuators to the panels. Directivity measurements were made in the far field. Measurements were also taken of the pressure field established in the duct cross-section. Modal decomposition was applied to the data. It was found that the dominant acoustic modes in the duct are those whose cut-on frequencies were near the frequency of excitation. / Master of Science

The results of a test program incorporating a dual hot wire aspirating probe to radially survey the by-pass duct downstream of an axial flow fan stage are presented. The probe measures time resolved total temperature and total pressure from which isentropic efficiency is calculated. The objective was to provide time resolved data to further the understanding of the flow and aid in determining the source of high losses located near the rotor tip. A technique for quantifying randomness of an unsteady flow is developed, and the randomness of the surveyed flow is shown to correlate with the losses. A new method of ensemble averaging instantaneous data is presented which produces an identifiable blade passage profile even in a random flowfield where traditional techniques often fail. Time averages of the aspirating probe data are shown to agree with conventional steady-state measurements within the experimental uncertainties. Unsteady features seen in the data are compared to similar features noted in the literature, and contour plots of the ensemble averaged data and unsteady fluctuations are presented. / Master of Science

A series of experiments was conducted to investigate the radiation of fan noise through a supersonic inlet. A scaled-down model of an axisymmetric, mixed-compression, supersonic inlet (P-inlet) was used in conjunction with a 10.4 cm (4.1 in) diameter turbofan engine simulator as the noise source. The tests were conducted at an outdoor facility under static conditions. An attempt is made to reduce the fan noise radiated in the forward sector by modifying the auxiliary inlet doors. The modified doors are designed to reduce the inlet distortion to the fan face. In addition, the new design also uses a converging flow passage in the auxiliary doors in order to take advantage of the noise attenuation due to the choking effect. Both aerodynamic and acoustic measurements are taken in the experiments. The results show that when compared to the original design, the modified auxiliary inlet doors are successful in reducing distortion to the fan face, and that the blade passing frequency tone has been decreased by an average of 6 dB in the forward sector. Results from the closed auxiliary inlet door case are also presented to provide additional comparisons. / Master of Science

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this project is to investigate the method and accuracy of simulating axial ow fans with three-dimensional axisymmetric CFD models. Two models are evaluated and compared with experimental fan data. Veri cation data is obtained from a prototype fan tested in a facility conforming to the BS 848 standards. The ow eld over the blade surfaces is investigated further with a visualization experiment comprising of a stroboscope and wool tufts. Good correlation is found at medium to high ow rates and recommendations are made for simulation at lower ow rates as well as test guidelines at the fan test facility. The results and knowledge gained will be used to amend currently used actuator disc theory for axial ow fan simulation. / AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om die metode en akkuraatheid om aksiaalvloeiwaaiers met drie-dimensionele BVM modelle te simuleer, te ondersoek. Twee modelle word geëvalueer en met eksperimentele waaiertoetse vergelyk. Veri- kasie data is verkry vanaf 'n prototipe waaier wat in 'n fasiliteit getoets is en wat aan die BS 848 standaarde voldoen. Die vloeiveld oor die lemoppervlaktes word ondersoek met 'n visualisering eksperiment wat uit 'n stroboskoop en wolletjies bestaan. Goeie korrelasie word gevind vir medium tot hoë massavloeie en aanbevelings word gemaak vir die simulasie by laer massavloeie met riglyne vir toetswerk in die toets-fasiliteit. Die resultate en kennis opgedoen sal gebruik word in die verbetering van huidige aksieskyfteorie vir numeriese aksiaalvloeiwaaier simulasies.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The majority of power stations in South Africa are located in coal rich, but arid regions where wet-cooled condenser systems are not feasible from an environmental and economic perspective. Consequently the focus on power generation cooling has shifted towards dry-cooling systems using air-cooled steam condensers (ACSC). The steam passing through the ACSC units is cooled by an air-draught, mechanically induced by large diameter axial flow fans. Consequently the effectiveness of the cooling is impacted by the performance of these fans, which ultimately affects the overall efficiency of the power plant. However, due to the large diameters (> 10 m) of these fans, their performance is predicted based on small scale test results using the fan scaling laws. The objective of this project was to develop a methodology which accurately predicts the fan performance of more than one fan configuration using computational fluid dynamics (CFD) software and validating the results with experimental tests. Four fans were considered in this study of which three were scaled fan models of large air-cooled axial fans. The performance of the scaled fan models (L1-, L2- and N-fan) were measured in a type A, BS 848 standard fan test facility. The geometries of the fans were scanned three-dimensionally to obtain the models for simulation purposes. The other fan considered was an 8- bladed axial fan designed by Bruneau (1994) and referred to as the B-fan. Simulations were carried out for the L2-, N- and B-fan for different computational domains while implementing the multiple reference frames (MRF) and steady RANS approach. Three variations of the k-ε turbulence model were also investigated. Noticeable differences were found between the experimental and numerical results of the B-fan. Good correlations between the numerical and experimental fan static pressure, fan power and fan static efficiency were found for the two scaled model fans over a large operating range. The performance of the full scale fans, however, did not correlate well with the performance of the scaled models. It is concluded that accurate simulations of axial fans are possible although these domains require a large number of mesh elements. It is recommended that further research is carried out to investigate the relationship between full scale and small scale fan models. / AFRIKAANSE OPSOMMING: Die meerderheid steenkool kragstasies in Suid-Afrika is geleë in droë, maar steenkool ryke streke waar natverkoelde kondensor stelsels uit ʼn omgewings en ekonomiese perspektief nie geskik is nie. Die fokus in kragopwekking verkoeling het dus verskuif na droë-verkoelings stelsels en spesifiek die gebruik van lugverkoelde stoomkondensors (LVSKs). Die stoom in LVSK eenhede word verkoel deur atmosferiese lug wat meganies geïnduseer word deur groot aksiaalvloeiwaaiers. Die effektiwiteit van die verkoelingsproses word gevolglik beïnvloed deur die werksverrigting van hierdie waaiers wat uiteindelik die algehele effektiwiteit van die kragstasie beïnvloed. As gevolg van hierdie waaiers se grootte word hulle werksverrigting egter bepaal op grond van kleinskaal toetsresultate en deur gebruik te maak van die waaierskaleringswette. Die hoofdoelwit van hierdie projek was om ‘n metodiek te ontwikkel wat die werksverrigting van ʼn aksiaalwaaier akkuraat kan voorspel vir ʼn verskeidenheid opstellings, deur gebruik te maak van berekenings vloei meganika (BVM) sagteware en die resultate eksperimenteel te verifieer. Die projek het vier waaiers ondersoek waarvan drie van hierdie waaiers geskaleerde modelle van groot lugverkoelde aksiaalwaaiers was. Die werksverrigting van die geskaleerde waaiers (L1-, L2- en N-waaier) was met ‘n tipe A, BS 848 standaard waaier toetsfasiliteit gemeet. Die geometrie van dié waaiers was ook drie-dimensioneel opgemeet vir simulasie doeleindes. Die B-waaier, ‘n 8 lem aksiaalwaaier, wat ontwerp is deur Bruneau (1994) was slegs numeries ondersoek. Die L2-, N- en Bwaaier was gesimuleer in verskillende berekeningsdomeine deur gebruik te maak van die multi verwysingsraamwerk en gestadigde vloeiberekenings benaderings. Drie k-ε turbulensie modelle was ook ondersoek. Merkbare verskille tussen die eksperimentele en numeriese resultate van die Bwaaier was waargeneem. Goeie korrelasie tussen die eksperimentele en numeriese resultate van die geskaleerde waaiers vir ‘n wye bedryfsbestek was gevind. ‘n Vergelyking tussen die volskaal en kleinskaal waaiers se werksverrigting het egter beduidende afwykings aangetoon. Deur gebruik te maak van ‘n groot aantal selle in die berekeningsdomein was dit moontlik om ʼn verskeidenheid aksiaalvloeiwaaiers akkuraat te simuleer. Verdere navorsing wat die verhouding tussen volskaal en kleinskaal waaiers ondersoek woord aanbeveel.