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Although blanket peat covers many major headwater areas in Britain, runoff production within these upland catchments is poorly understood. This thesis examines runoff production mechanisms within the blanket peat catchments of the Moor House National Nature Reserve, North Pennines, UK. Catchments ranging from 11.4 km^ down to the hillslope and plot-scale are examined. Runoff from the monitored catchments was flashy. Lag times are short and rainwater is efficiently transported via quickflow- generating mechanisms such that flood peaks are high and low flows poorly maintained. Hillslope and plot-scale runoff measurements show that the flashy catchment response is the result of the dominance of overland flow. Typically 80 % of runoff is produced as overland flow. This occurs both on bare and vegetated surfaces. Most of the remaining runoff is generated from the upper 10 cm of the peat, except where well-connected macropore and pipe networks transfer flow through the lower layers. Below 10 cm depth the blanket peat matrix fails to contribute any significant runoff Thus most groundwater-based models of peat hydrological process are not readily applicable to these catchments. Suggestions that infiltration-excess overland flow may be largely responsible for the flashy regime of these upland catchments are not substantiated by the blanket peat infiltration data presented in this thesis. Monitoring of hillslope runoff mechanisms combined with rainfall simulation (at realistic intensities of 3-12 mm hr(^-1)) and tension- infiltrometer experiments shows that saturation-excess mechanisms dominate the response. Infiltration is relatively rapid in the upper peat layers until they become saturated and overland flow begins. High water tables result in rapid saturation of the peat mass such that even at low rainfall intensity runoff production is just as efficient as during high intensity events. While macropores have largely been ignored in blanket peat, results presented suggest that up to 30 % of runoff may be generated through them. Occasionally these macropore networks develop through the deeper peat such that runoff bypasses the matrix and runs off at depth from small outlets and larger pipe networks. Seasonal variations in runoff- generating processes can be exacerbated by drought which causes structural changes to the near-surface of the peat. This was found to result in enhanced infiltration and macropore flow which may encourage pipe network development. Flow has been monitored simultaneously from several natural pipes in a 0.4 km(^2) headwater catchment of the Tees. This catchment provides one of the few examples of pipeflow monitoring outside the shallow peaty-podzols of mid-Wales. Natural pipes are found throughout the soil profile and can be at depths of up to three metres. Ground penetrating radar was useful in identifying deep subsurface piping and suggestions are made for improvements to the application. The pipe networks were found to be complex and results demonstrate that outlet location and size may bear little relation to the form and depth of the pipe a short distance upslope. Pipes generally contribute less than 10 % to catchment runoff but on the rising and falling hydrograph limbs can contribute over 30 % to streamflow. Pipeflow lag times are short suggesting that both the shallow and deep pipes may be well connected to the surface. Thus while matrix runoff contributions at depth within the peat may be low, macropore flow mechanisms can be significant.

A project report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / Underground chilling installations have an important role in deep mining operations because the total cost of cooling a mine is minimized when underground machines deliver as high a proportion of the required cooling as practicable. Thus the refrigerating load of an underground installation should be maximized to the extent permitted both by the environment in which the installation operates, and by the physical characteristics of the machines in the installation. This study analyses how, and to what extent, the refrigerating load of older, already installed water chilling machines rejecting heat into a limited supply of return water may be maximized through configuration of their water circuits and capacity control of their compressors. Multiple-machine installations are simulated in a range of scenarios, using the thermodynamically efficient series-counterflow arrangement, to predict both the potential maximum refrigerating load and the expected refrigerating load of such installations. The simulation results indicate significant potential for installations to chill water more efficiently and thus deliver larger, maximized, refrigerating loads. For scenarios where a larger-than-design flowrate of return water is available, so permitting machines to be operated with little or no capacity control, the simulated chilling efficiency and thus the expected refrigerating loads tend toward, and in some cases almost match, the potential maximum values. For simulations in which compressor capacity control is used to prevent the return water temperature from exceeding its maximum permitted value, expected refrigerating loads fall short of their potential values, by varying amounts, due to the low machine cycle efficiency caused largely by reduced compressor isentropic efficiency at part load. For a limited supply of return water for heat rejection, the simulations indicate that load maximization efforts should focus on the machines in an installation being connected in a series-counterflow arrangement and operated, as far as practicable, at or near full capacity to create the best prospect for approaching potential maximum refrigerating load.

The design of a fabric composite heat pipe has been completed. It is composed of two end caps, between which a fluid containment liner composed of metal foil and an outer structural layer composed of a ceramic fabric is stretched. The interior of the heat pipe is layered with a ceramic fabric wick. This heat pipe is being constructed currently at Oregon State University. The heat pipe test facility has been designed and built. Final assembly of the various components is now under way. This test facility consists of a vacuum chamber with a coolant jacket on the outside. Inside this chamber a test stand is placed which is composed of radiation shields and a supporting stand for the heat pipe and the heaters. Experimental work has been performed to ensure material compatibility of the metal foils used as a fluid containment liner. Specific materials tested include copper, aluminum, titanium, FEP teflon and three ceramic fabrics. These materials have been exposed to a variety of working fluids for up to 5000 hours at various sub-boiling temperatures. The best combinations of materials include aluminum or copper and acetone, or titanium and water. The least compatible combinations included aluminum or copper and water. An experimental apparatus to measure the wettability of candidate ceramic fabric wicks was designed and built. This apparatus included a pressure chamber to allow measurements to be taken at elevated pressures and temperatures. The liquid front velocity in one meter lengths of unwetted samples of ceramic fabrics was measured. A computer was used to determine liquid front position at 30 finite points along the fabric sample. Analysis of the data allowed calculation of a constant composed of two wicking parameters to be measured. Analysis of various analytical methods for predicting these parameters was performed. / Graduation date: 1993

Condensation Induced Water-Hammer, CIWH, has been an historical problem for the nuclear power industry over the past 2 decades. It has caused damage to plant systems, and considerable anguish to plant operators. This thesis has embarked on an attempt to characterize the fluid motion, heat transfer, mixing, and stability of a horizontal, stratified flow of steam over subcooled water. A literature review was conducted to determine the state of numerical and analytical methods which have been applied to this problem. The result of the review has led to the implementation of new analytical interfacial stability models. Information from the review has also led to the development of correlations for wave frequency and amplitude on the phase interface. A numerical model has been developed to estimate the temperature profile on the phase interface. Also, the model will construct, by use of the above correlations, an estimate of the interface wave structure. This wave structure is then evaluated against a non-linear model for interface stability to determine the onset of slug formation. The numerical model has been used to evaluate two known CIWH events. The results indicate that the onset of slug formation is necessary, but not sufficient, to ensure a water-hammer event. The results imply that there is the possibility that once a slug has formed, it may break up before a trapped steam void can fully collapse. The model also indicates that CIWH in steam generator, feedwater nozzle sections is not due to the formation of slug on an unstable phase interface. Rather, CIWH may occur when the liquid level inside of the feedwater nozzle is above the top of the feedring, thus creating an isolated steam pocket. The rapid condensation of the trapped steam in the causes CIWH. This particular result implies that it may be possible to completely avoid CIWH in the feedwater nozzle altogether. / Graduation date: 1991

Conventional stainless steel - water and ceramic fabric composite water heat pipes have been built and tested. The tests have been conducted to compare the performance characteristics between conventional and fabric composite heat pipe radiators for space nuclear power heat rejection systems. The fabric composite concept combines a strong ceramic fabric with a thin metal liner to form a very lightweight heat pipe. The heat pipes tested have used identical, homogeneous fabric wicks and water as the working fluid. One fabric composite heat pipe has been constructed by fitting a braided aluminoborosilicate fabric tube over the outside of the conventional stainless steel heat pipe. A more advanced fabric composite design combines the woven fabric with a 0.25 mm (10 mil) stainless steel tube as the liner, and reduces the mass of the heat pipe by a factor of three. A heat pipe testing facility was designed and built for the purpose of testing various conventional and fabric composite heat pipes. This facility allows the testing of heat pipes in a vacuum, at low temperatures, and can accommodate a variety of heat pipe designs. Instrumentation and computer interfacing provide for continuous monitoring and evaluation of heat pipe performance. Tests show that heat pipe radiator capacity can be significantly enhanced by using the fabric composite design. Tests comparing a conventional heat pipe with fabric composite heat pipes achieved a 100% increase in the emissivity and heat rejection capacity of the radiator. Since the ceramic fabric is strong enough to withstand the internal pressure of the heat pipe, a very thin metal foil can be used to contain the working fluid. The increase in heat rejection capacity, combined with the significant reduction in the heat pipe mass, translates into a substantial savings for space power systems employing fabric composite heat pipe radiators. / Graduation date: 1993

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