Thesis (M.S.)--University of Nevada, Reno, 2004. / "December 2004." Includes bibliographical references (leaves 43-46). Online version available on the World Wide Web.

Dissertation (Ph. D.)--University of Stellenbosch, 1992. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

No description available.

Doctor of Philosophy / The main contribution of this work is to answer several important questions relating to natural draft wet cooling tower (NDWCT) modelling, design and optimisation. Specifically, the work aims to conduct a detailed analysis of the heat and mass transfer processes in a NDWCT, to determine how significant the radial non-uniformity of heat and mass transfer across a NDWCT is, what the underlying causes of the non-uniformity are and how these influence tower performance. Secondly, the work aims to determine what are the consequences of this non-uniformity for the traditional one dimensional design methods, which neglect any two-dimensional air flow or heat transfer effects. Finally, in the context of radial non-uniformity of heat and mass transfer, this work aims to determine the optimal arrangement of fill depth and water distribution across a NDWCT and to quantify the improvement in tower performance using this non-uniform distribution. To this end, an axisymmetric numerical model of a NDWCT has been developed. A study was conducted testing the influence of key design and operating parameters. The results show that in most cases the air flow is quite uniform across the tower due to the significant flow restriction through the fill and spray zone regions. There can be considerable radial non-uniformity of heat transfer and water outlet temperature in spite of this. This is largely due to the cooling load in the rain zone and the radial air flow there. High radial non-uniformity of heat transfer can be expected when the cooling load in the rain zone is high. Such a situation can arise with small droplet sizes, low fill depths, high water flow rates. The results show that the effect of tower inlet height on radial non-uniformity is surprisingly very small. Of the parameters considered the water mass flow rate and droplet size and droplet distribution in the rain zone have the most influence on radial noniv uniformity of heat transfer. The predictions of the axisymmetric numerical model have been compared with a one dimensional NDWCT model. The difference between the predictions of tower cooling range is very low, generally around 1-2%. This extraordinarily close comparison supports the assumptions of one dimensional flow and bulk averaged heat transfer implicit in these models. Under the range of parameters tested here the difference between the CFD models predictions and those of the one dimensional models remained fairly constant suggesting that there is no particular area where the flow/heat transfer becomes so skewed or non-uniform that the one dimensional model predictions begin to fail. An extended one dimensional model, with semi-two dimensional capability, has been developed for use with an evolutionary optimisation algorithm. The two dimensional characteristics are represented through a radial profile of the air enthalpy at the fill inlet which has been derived from the CFD results. The resulting optimal shape redistributes the fill volume from the tower centre to the outer regions near the tower inlet. The water flow rate is also increased here as expected, to balance the cooling load across the tower, making use of the cooler air near the inlet. The improvement has been shown to be very small however. The work demonstrates that, contrary to common belief, the potential improvement from multi-dimensional optimisation is actually quite small.

Doctor of Philosophy / The main contribution of this work is to answer several important questions relating to natural draft wet cooling tower (NDWCT) modelling, design and optimisation. Specifically, the work aims to conduct a detailed analysis of the heat and mass transfer processes in a NDWCT, to determine how significant the radial non-uniformity of heat and mass transfer across a NDWCT is, what the underlying causes of the non-uniformity are and how these influence tower performance. Secondly, the work aims to determine what are the consequences of this non-uniformity for the traditional one dimensional design methods, which neglect any two-dimensional air flow or heat transfer effects. Finally, in the context of radial non-uniformity of heat and mass transfer, this work aims to determine the optimal arrangement of fill depth and water distribution across a NDWCT and to quantify the improvement in tower performance using this non-uniform distribution. To this end, an axisymmetric numerical model of a NDWCT has been developed. A study was conducted testing the influence of key design and operating parameters. The results show that in most cases the air flow is quite uniform across the tower due to the significant flow restriction through the fill and spray zone regions. There can be considerable radial non-uniformity of heat transfer and water outlet temperature in spite of this. This is largely due to the cooling load in the rain zone and the radial air flow there. High radial non-uniformity of heat transfer can be expected when the cooling load in the rain zone is high. Such a situation can arise with small droplet sizes, low fill depths, high water flow rates. The results show that the effect of tower inlet height on radial non-uniformity is surprisingly very small. Of the parameters considered the water mass flow rate and droplet size and droplet distribution in the rain zone have the most influence on radial noniv uniformity of heat transfer. The predictions of the axisymmetric numerical model have been compared with a one dimensional NDWCT model. The difference between the predictions of tower cooling range is very low, generally around 1-2%. This extraordinarily close comparison supports the assumptions of one dimensional flow and bulk averaged heat transfer implicit in these models. Under the range of parameters tested here the difference between the CFD models predictions and those of the one dimensional models remained fairly constant suggesting that there is no particular area where the flow/heat transfer becomes so skewed or non-uniform that the one dimensional model predictions begin to fail. An extended one dimensional model, with semi-two dimensional capability, has been developed for use with an evolutionary optimisation algorithm. The two dimensional characteristics are represented through a radial profile of the air enthalpy at the fill inlet which has been derived from the CFD results. The resulting optimal shape redistributes the fill volume from the tower centre to the outer regions near the tower inlet. The water flow rate is also increased here as expected, to balance the cooling load across the tower, making use of the cooler air near the inlet. The improvement has been shown to be very small however. The work demonstrates that, contrary to common belief, the potential improvement from multi-dimensional optimisation is actually quite small.

Thesis (Ph.D.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (p. 171-175).

Thesis (M.S.)--University of Wisconsin, 1973. / eContent provider-neutral record in process. Description based on print version record. Includes a bibliography.

Test data of forced draft cooling towers is all too meager, and that available is, in many instances, incomplete. It is the opinion of the authors that putting cooling tower design on a rational basis can be brought about only by two methods. Either complete and intensive study of all existing towers or a thorough study of models, similar to the research conducted on airplanes in wind tunnels and on boat hulls in towing tanks, is necessary. Models used should be so constructed that quantity, condition, and velocity of air; quantity and condition of water; and type and arrangement of filling may be controlled. It is by the second method that the authors believe rational tower design may best be brought about. / Master of Science

Master of Science