In 21 century finned surfaces are used in almost all condensers to enhance their heat transfer capabilities. A lot of different models are presented in the literature: on horizontal and vertical finned tubes, inside finned tubes. The validation method of the theoretical models is based on comparison between measurement of average heat transfer coefficient and one calculated by the model. But in this case it is impossible to validate all approaches made in the theory. The presented work aims to understand the real relation between assumptions made in the theory and flow of the condensate film along a fin. Therefore a comprehensive investigation of the film condensation phenomena on curvilinear surfaces has been done. This investigation has been done in the framework of the preparation of “SAFIR” and “EMERALD” space experiments aboard International Space Station. A special attention has been given to clarify some technical and technological problems that could eventually have a positive feedback for industrial applications. The model of the fin shape optimization has been developed. It takes into account surface tension forces and finite heat conductivity of the fin material. Developed model allows to significantly increase the condensate outflow as compared with the case of the optimal isothermal fin shape at the finite heat transfer conductivity. Enhancement coefficient increases with fin heat conductivity decreasing. The experimental and theoretical investigation of film condensation on a disk-shaped fin has been done under groun condition. 3D condensation model at different gravity levels has been developed. This model allows to reveal the area of dominant influence of surface tension forces. First prototype of experimental cell for the space experiments has been developed and tested. The temperature distribution along the curvilinear fin surface has been measured. The measurements of the film thickness at the fin top shows that the film thickness does not equal to zero as was assumed in some previous theoretical models. Developed model is in a good agreement with experimental results. In the ground set-up the measurement techniques as in future space experiments were realized: local temperature measurement of the fin surface, measurement of non-condensable gas mole fraction, optical system for local film thickness measurement and system of average heat transfer coefficient measurement. Experimental results approve the usefulness of these systems. Optical system based on schlieren technique for film surface deformation has been investigated and developed. This system was used for the investigation of shear driven liquid film on the mirror like substrate under microgravity condition. The microgravity condition was simulated during ESA Parabolic Flight Campaign of October-November 2009. The experimental results show the high capabilities of this system. In the framework of the space experiments preparation the analysis of appropriate liquid has been done. Three candidates have been compared: Water, Ethyl alcohol and FC-72. Third liquid has been chosen as applicable liquid for the “SAFIR” and “EMERALD” experiments. The optimal fin shapes and film thickness distribution have been calculated for the working liquid. Using obtained results requirements for space experiments have been prepared.

Gene families in vertebrates often contain more dulicates (paralogs) than in invertebrates. This has been attributed to genome duplications, i.e., tetraploidizations. Two of the gene families that have expanded in vertebrate evolution are the neuropeptide Y (NPY) family of peptides and the neuropeptide Y receptors (NPYR) that are involved in many brain functions including appetite regulation. Two NPYR genes, Y2 and Y7, were cloned in the rainbow trout. Although they arose from a common ancestral gene in early vertebrate evolution, their ligand-binding properties are very similar. Two NPYR genes were cloned in the coelacanth Latimeria chalumnae and found to be orthologs of Y5 and Y6 discovered in mammals. Analyses of gene families close to the NPYR genes in the pufferfishes T. nigroviridis and T. rubripes showed that at least 25 additional gene families had an evolutionary history similar to the NPYR family, thereby providing evidence for fish specific-duplications of these chromosomes. Cloning and phylogenetic analysis of 22 NPYR gene fragments from several ray-finned fishes showed that basal species seem to have the same repertoire as tetrapods. Despite the tetraploidization in the teleost fish lineage, many teleosts seem to have fever genes than the gnathostome ancestor due to gene loss. Only one duplicate seems to have survived. The NPY peptide family was found to have expanded in the teleost tetraploidization with duplicates of both NPY and PYY (peptide YY) in some teleosts. Fourteen neighboring gene families were found to have evolved in a similar manner as the NPY-family genes. Positional information fascilitated orthology assignment of peptide genes in teleost fishes and allowed correction of previously misidentified genes. In summary, the evolutionary history of the NPY and NPYR gene families involve large-scale duplication events coinciding with the proposed tetraploidizations. The appearance of new genes in early vertebrates and in teleost fishes probably had important implications for the evolution of new functions in this system.

No description available.

<p> Experiments were performed to investigate the effect that a gap between a heated fin and a porous plate has on the heat transfer performance of a simulated capillary evaporator. The heat transfer performance was examined for two porous plates with average pore radii of 50 and 200 μm respectively. Tests were performed for gap distances between 0 and 900 μm and heat fluxes ranging from 17 to 260 kW/m^2. The heat transfer performance of the simulated capillary evaporator initially increased as the gap distance was increased. However, a further increase in the gap distance caused a decrease in performance. The maximum heat transfer performance occurred at a smaller gap distance for the plate with the smaller pore radius. For small gap distances, persistent high temperature regions were observed on the surface of the heated foil that grew and became more frequent at higher heat fluxes. For larger gap distances, saturated regions that appeared on the foil at moderate heat fluxes suggest that microlayer evaporation may be taking place within the gap. At high heat fluxes, these saturated regions are no longer present, but the temperature of the heated foil remained stable.</p> <p> The heat transfer process in the porous media was examined using thermocouples embedded within the porous plates. These temperature measurements indicate that a two phase region forms within the porous plate for a pore radius of 200 μm. Little evidence of vapour was observed within the plate with a pore radius of 50 μm. In that case, there was more evidence of vapour present at the surface of the porous plate. There was less evidence of vapour at the surface of the porous plate for the larger gap distances, suggesting that the vapour escapes more easily through the gap at larger gap distances.</p> / Thesis / Master of Applied Science (MASc)

Eco-friendly non-CFC refrigerants were introduced in the Air Conditioning and Refrigeration industry during the last few years to reduce damage to the stratospheric ozone layer. The HFC refrigerant R-134a, which has zero Ozone Depletion Potential (ODP), is being used extensively as a replacement for R-12 and also in some centrifugal chillers as a replacement for R-11. However, the disadvantage of R-134a is its comparatively high global warming potential (GWP). Owing to energy crisis and also to reduce the indirect warming impact resulting from electrical energy usage, the new refrigeration systems should be operated at the lowest possible condensing temperatures. In view of this, several active and passive techniques for augmentation of condensation heat transfer and reduction of condensation temperature are gaining increasing attention. Passive augmentation methods are more popular than active ones. To this end, micro-finned tubes of various geometrical shapes are being explored for compact heat exchangers in the refrigeration industry as the best choice. Towards understanding the enhancement in condensation heat transfer coefficients in micro-finned tubes, a test facility has been fabricated to measure the condensing coefficients for R-134a refrigerant. Condensation experiments have been conducted on single plain and finned tubes of outer diameter 19 mm with a refrigerant saturation temperature of 400C and tube wall temperatures 350C, 320C, 300C and 280C respectively. Water is used as the cooling medium inside the tubes with the flow rate varying from 180 lph to 600 lph. The condensing coefficient typically ranged from 0.9 – 1.4 kW/(m2 K) for plain tubes and from 4.2 to 5.8 kW/(m2 K) for the finned tubes. The results of the plain v tube are found to compare favourably with the Nusselt’s theory, leading to a validation of the experimental procedure. Upon comparing the results of finned and plain tubes, it is found that provision of fins result in an enhancement factor of 3.6 to 4.6 in the condensation heat transfer coefficients. This level of enhancement is larger than that resulting from the enhanced surface area of the finned tube surface, suggesting that, apart from the extended area, the surface tension forces play an important role in the augmentation process by driving the condensate from the fin crests to the valleys in between the fins. The measured augmentation factors have also been cross-checked using the Wilson plot method. Detailed error analysis has been performed to quantify the uncertainty in the condensation heat transfer coefficient. The performance of a bank of tubes has been determined based on the measurements carried out on practical condensers of two large chillers with refrigerating capacities of 500 TR and 550 TR. On comparing the finned tube bank results and the single finned tube results, it is found that the average condensation heat transfer coefficient in a bank of tubes having N rows varies as N ¯1/6. The deterioration is in agreement with the relation proposed by Kern.

No description available.

Approved for public release; distribution is unlimited / The construction of an apparatus for the condensation performance testing of a horizontal bundle of four tubes with various refrigerants was completed. The apparatus was instrumented, and data reduction software was developed to provide bundle and single tube condensation data. Two tube bundles were tested, smooth copper tubes and low integral-fin copper-nickel tubes, with two refrigerants, R-114 and R-113. An enhancement ratio of about 2.0 for the overall heat transfer coefficient was demonstrated for the finned tubes over the smooth tubes. Internal contamination, possibly due to a breakdown of the refrigerant molecules when subjected to high temperatures in the boiling chamber, inhibited further meaningful data collection. Recommendations for improvement of the test apparatus are made. / http://archive.org/details/condensationofre00mabr / Lieutenant, United States Navy

This thesis presents investigations of diversity at three genes (class I, DQA and DQB) of the Major Histocompatibility Complex (MHC) in cetaceans. The MHC genes encode for proteins that are crucial for initiating an immune response by binding invading pathogens in vertebrates. It has been acknowledged that a high diversity at these genes results in the ability to recognise a wider range of pathogens, therefore functional diversity is important for the survival of a species. Furthermore this diversity has been created under the influence of selection, which can reveal interesting contrasts with neutral markers about the history of selection of populations and species. The diversity at two genes (DQA and DQB) in natural populations of two contrasting species of cetaceans has been investigated in more detail. The species selected included both sub-species of Hector’s dolphin, the Hector’s dolphin (Cephalorhynchus hectori hectori) and the Maui’s dolphin (Cephalorhynchus hectori maui), as well as the long-finned pilot whale (Globicephala melas). These species were chosen, because both Hector’s dolphin sub-species contrast with the pilot whale species in regards to their population size, abundance, population structure and life history. For example both sub-species of Hector’s dolphin have small population sizes and only inhabit coastal areas around New Zealand, whereas the pilot whale is an abundant, pelagic dolphin species. In Chapter 2 the expression of class II MHC genes (DQA and DQB) was demonstrated for the first time for a cetacean species, the Hector’s dolphin. Using available information from the bottlenose dolphin (Tursiops truncatus), I also designed primers to investigate class I MHC. Fragments of MHC genes were amplified from cDNA, which was derived from blood samples of two Hector’s dolphins. These dolphins were the subject of a temporary live capture, presenting a unique opportunity for blood collection. No evidence was found for duplication of both MHC class II loci, but cloning suggested a minimum of three copies of class I genes within the genomic DNA. However, the expression of all class I genes was uncertain, since only one allele could be isolated from cDNA. Functionality for all three genes (class I, DQA and DQB) was supported by the evidence for balancing selection having operated on these genes, indicated by a higher ratio of non-synonymous to synonymous substitutions. In Chapter 3, a combination of single-strand conformation polymorphism (SSCP) and direct sequencing was used to describe DQA and DQB diversity in the Hector’s and Maui’s dolphin. Genetic samples for the Hector’s dolphin were available from previously collected stranding and biopsy samples (n = 233), representing three populations from the South Coast of New Zealand and the sub-species on the West Coast of the North Island of New Zealand. For the Hector’s dolphin of the South Island, a surprisingly large number of alleles at both loci (DQA = 4, DQB = 6) were found, considering their small population size and compared to other cetacean populations with larger population sizes. The Maui’s dolphin has been classified as critically endangered with less than 100 dolphins, but showed a relatively high nucleotide diversity for DQB ( = 4.5%). This diversity was based on only three alleles that have been retained in the sub-species, representing the most divergent of all six alleles. All populations showed strong geographic differentiation at both loci (DQA: FST=0.252; DQB: FST=0.333), with the greatest differentiation between the South Island population and the North Island Maui’s dolphin. Comparison to mitochondrial and microsatellite diversity suggested influence of stochastic genetic drift, although the pressure of balancing selection acting on DQB over an evolutionary time period was also evident by a higher ratio of non-synonymous to synonymous substitutions (dN/dS=5.9) and by a pattern of trans-specific allele sharing within the family of Delphinidae. In Chapter 4 similar methods were used to describe DQA and DQB in pilot whales using genetic samples from the long-finned pilot whale that were available from five mass-strandings from around New Zealand (n = 237). A larger number of alleles than for the Hector’s dolphin were found at both loci (DQA= 8; DQB= 8), although their large population size and pelagic abundance raises the expectation of an even greater number of alleles. The overall differentiation between mass-strandings was low, but significant for both loci (DQA: FST =0.012, DQB: FST =0.014). The differentiation of all strandings was greatest for the Golden Bay mass-stranding at DQA, but deviation from Hardy-Weinberg equilibrium at DQB suggested either sub-structure within mass-strandings (Wahlund effect) or the presence of null alleles. As for the Hector’s dolphin and other mammalian species, the influence of balancing selection acting on DQB over a long evolutionary time period was evident by a higher ratio non-synonymous to synonymous substitutions (dN/dS=9.3) and by a pattern of trans-specific allele sharing within the family of Delphinidae. Overall, diversity is surprisingly similar between these two cetacean species despite different life history characteristic, but low compared to domesticated ungulate species, such as the cow. If low MHC diversity is a general feature of cetaceans, due to the marine environment as suggested previously or rather a side effect of short-term demographic forces remains speculative. A standardised nomenclature for the increasing number of MHC alleles from cetacean is proposed in this thesis to assist with future development of this research.

Finned-tube heat exchangers are predominantly used in space conditioning systems, as well as other applications requiring heat exchange between two fluids. One important widespread use is in residential air conditioning systems. These residential cooling systems influence the peak demand on the U.S. national electrical system, which occurs on the hot summer afternoons, and thereby sets the requirement for the expensive infrastructure requirement of the nations power plant and electrical distribution system. In addition to this peak demand, these residential air conditioners are major energy users that dominate residential electrical costs and environmental impact. The design of finned-tube heat exchangers requires the selection of over a dozen design parameters by the designer. The refrigerant side flow and heat transfer characteristics inside the tubes have been thoroughly studied. However, the air side flow around the tube bundle and through the fin gaps is much more complex and depends on over a dozen design parameters. Therefore, experimental measurement of the air side performance is needed. First this study built an experimental system and developed methodology for measuring the air side heat transfer and pressure drop characteristics of fin tube heat exchangers. This capability was then used to continue the goal of expanding and clarifying the present knowledge and understanding of air side performance to enable the air conditioner system designer in verifying an optimum fin tube condenser design. In this study eight fin tube heat exchangers were tested over an air flow face velocity range of 5 ?? ft/s (675-1600cfm). The raw data were reduced to the desired heat transfer and friction data, j and f factors. This reduced heat transfer and friction data was plotted versus Reynolds number and compared. The effect of fin spacing, the number of rows and fin enhancement were all investigated. The heat transfer and friction data were also plotted and compared with various correlations available from open literature. The overall accuracy of each correlation to predict experimental data was calculated. Correlations by C.C. Wang (1998b, 1999) showed the best agreement with the data. Wangs correlations (1998b, 1999) were modified to fit the current studys data.

Finned heat sink use for electronics cooling via natural convection is numerically investigated. An experimental study from the literature that is for vertical surfaces is taken as the base case and the experimental setup is numerically modeled using commercial CFD software. The flow and temperature fields are resolved. A scale analysis is applied to produce an order-of-magnitude estimate for maximum convection heat transfer corresponding to the optimum fin spacing. By showing a good agreement of the results with the experimental data, the model is verified. Then the model is used for heat transfer from inclined surfaces. After a large number of simulations for various forward and backward angles between 0-90 degrees, the dependence of heat transfer to the angle and Rayleigh number is investigated. It is observed that the contributions of radiation and natural convection changes with the angle considerably. Results are also verified by comparing them with experimental results available in literature.