Optimal Design of Heat Exchangers to Enhance Thermal Performance

Heat transfer is a key aspect of devices and industrial processes for maintaining their functionality and achieving better product quality. Heat exchangers of different types and sizes are used to transfer heat between a source and a working fluid to maintain the desirable working temperatures. Due to the space requirements of devices, there is a need for efficient heat exchangers with less size and less weight. Gyroid structure is a type of Triply Periodic Minimal Surface structures that define an internal volume that maximizes surface area and strength while minimizing mass. The hypothesis is that gyroid structures are useful in heat exchanger design, as they can optimize heat transfer to be more efficient, compared to traditional heat exchanger designs. A gyroid structured heat exchanger was designed, 3D printed, and compared to a commercial plate heat exchanger. Using different water flow rates, temperatures at the hot and cold inlets/outlets were measured using thermocouples and PicoLog until they reached steady state and calculated heat transfer rate and efficiency. It is found that heat transfer rate linearly increases with flow rate and that the heat transfer rate for the commercial heat exchanger is about twice the heat transfer rate for the gyroid one. A gyroid heat exchanger with the same surface area as the commercial one is likely to have a much larger heat transfer rate. Additional measurements, such as pressure drop and internal volume, should be taken to properly compare different heat exchangers, while minimizing heat loss and uncertainty in data

Droplet Impact, Part 1: Controlling Skirting Velocity

Droplet skirting occurs when a fluid droplet rolls over a bath of the same fluid without merging. To achieve skirting, we introduced a ~0.6 mm-diameter droplet of 1 cSt silicone oil into a bath of the same fluid by bouncing it off an angled glass slide coated with 100,000 cSt silicone oil. Our work suggests that initial skirting velocity increases as a function of slide angle and, to a lesser degree, droplet generator height. Furthermore, we conclude that the droplet lifetimes (initiation of skirting until rupture) and corresponding values (rate of decay of motion) appear consistent with theoretical predictions for such droplets based on previous research (which did not address \u3e0.75 mm-diameter droplets

Droplet Impact, Part 2: Engineering a Droplet Generator

Prior droplet impact research at DePauw used a syringe to pump fluid through a tube to create a droplet. This method generated ~2.5mm diameter droplets with secondary satellite droplets that formed during pinch-off and influenced rupture upon collision with the main droplet. Furthermore, the large diameter caused the droplet to experience significant oscillation as it fell, making it difficult to control impact shape without changing impact velocity. Part of this summer’s research focused on adapting preexisting designs for droplet generators to build our own version that creates small, consistent droplets without interference from satellite droplets or jets (which form at high speeds/large diameters)

MEMS 411: 3D Clay Printer

The Washington University School of Architecture has a class called Digital Ceramics, that utilizes a 3D Printer that prints clay instead of plastic filament. Students use this device to make art projects. As interesting as this device is, it isn’t without problems. Our team decided to tackle some of the problems involved which we recognized to be: long set-up and tear-down times, and unsuccessful prints due to nozzle falling out

Temperature dependence of aragonite and calcite skeleton formation by a scleractinian coral in low mMg/Ca seawater

Temperature-dependent aragonite and calcite formation by scleractinian corals were examined in low molar (m) Mg/Ca seawater, the experimental conditions replicating the fluctuating mMg/Ca levels prevailing throughout the Phanerozoic Eon. Incubation and skeletal growth monitoring of juveniles of the scleractinian coral Acropora solitaryensis for 4 months from the planula stage, in seawater with mMg/Ca ratios of 5.2, 1.0, and 0.5, and temperatures of 19–28 °C, indicated that polymorphism of present-day scleractinian corals in low mMg/Ca seawater is also influenced by seawater temperature. However, corals produced more aragonite than formed in inorganic CaCO3 precipitation experiments under the same conditions, except at 19 °C. Although the aragonite content reflected the results of the latter (abiotic) experiments at 19 °C, it is suggested that aragonitic scleractinian corals controlled skeletal formation biologically under low mMg/Ca conditions at higher temperature, growth rates being faster at 25 °C and slower at 19 °C for all mMg/Ca ratios. Compared with growth rates under the present-day-equivalent seawater Mg/Ca level of 5.2, juvenile growth decreased by 62.8% ± 14.7% and 56.7% ± 6.7% under mMg/Ca levels of 1.0 and 0.5, respectively; the results suggest that growth of aragonitic scleractinian corals is suppressed throughout varying seasonal temperatures under low mMg/Ca conditions. This supports previous findings from variable temperature perspectives that scleractinian corals grow more slowly in low mMg/Ca (Cretaceous) seawater, interpreted as a possible explanation for the hiatus in scleractinian reef building in the Cretaceous Period

Rapid Detection of Botulinum Neurotoxins—A Review

A toxin is a poisonous substance produced within living cells or organisms. One of the most potent groups of toxins currently known are the Botulinum Neurotoxins (BoNTs). These are so deadly that as little as 62 ng could kill an average human; to put this into context that is approximately 200,000 × less than the weight of a grain of sand. The extreme toxicity of BoNTs leads to the need for methods of determining their concentration at very low levels of sensitivity. Currently the mouse bioassay is the most widely used detection method monitoring the activity of the toxin; however, this assay is not only lengthy, it also has both cost and ethical issues due to the use of live animals. This review focuses on detection methods both existing and emerging that remove the need for the use of animals and will look at three areas; speed of detection, sensitivity of detection and finally cost. The assays will have wide reaching interest, ranging from the pharmaceutical/clinical industry for production quality management or as a point of care sensor in suspected cases of botulism, the food industry as a quality control measure, to the military, detecting BoNT that has been potentially used as a bio warfare agent

The role of herbivores in shaping subtropical coral communities in warming oceans

Tropicalization is rapidly restructuring subtropical marine communities. A key driver for tropicalization is changes in herbivory pressure that are linked with degrading ecosystem stability. Consequently, subtropical algal beds are being displaced by climate-mediated colonisation of coral communities. This process is thought to be aided by the elevated herbivory resulting from tropicalization, but the relative contribution to herbivory by different taxa is not fully understood. Evaluating herbivory pressure and its effect on coral cover and rugosity across a subtropical latitudinal gradient will help predict how these processes may change with further tropicalization and ocean warming. Herbivory pressure exerted by fishes and urchins across this subtropical latitudinal gradient remains unquantified. Using in-situ feeding observations, we quantify fish and urchin herbivory pressure at seven sites across non-accreting coral communities, and warmer accreting coral reefs in southern Japan. We then relate herbivory pressure to respective fish and urchin community structure and coral cover and rugosity. Urchin herbivory is greater on non-accreting coral communities than on true coral accreting reefs; a result which is reversed for fish herbivory. Overall, herbivory pressure is greater on accreting coral reefs than on coral non-accreting communities, but is dependent on reef characteristics as community structures differ more strongly among reefs than between regions. These factors are linked to coral cover and rugosity that differ between reefs, but not between climatic regions, further emphasising the influence of local factors on the benthic cover and the associated fish and urchin community, and thus herbivory pressure. Our findings provide a foundation for understanding how non-accreting coral communities may respond to ongoing tropicalization, given the fish and invertebrate herbivores they host

Coral assemblages at higher latitudes favor short-term potential over long-term performance

Funding for this research was provided by a Natural Environment Research Council (NERC) Doctoral Training Programme Scholarship to JC, a Royal Geographical Society Ralph Brown Expedition Award (RBEA 03/19) to MB and JC, the Australian Research Council Centre of Excellence for Coral Reef Studies (CE140100020) to JMP and others, the Australian Research Council Centre of Excellence for Environmental Decisions (CE110001014), a British Ecological Society small grant, the Winifred Violet Scott Charitable Trust, and the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement TRIM-DLV-747102 to MB. BS was supported by an Australian Research Council Discovery Early CareerResearch Award (DE230100141), a University of Sydney Fellowship and a Chancellor’s Postdoctoral Research Fellowship from the University of Technology Sydney.The persistent exposure of coral assemblages to more variable abiotic regimes is assumed to augment their resilience to future climatic variability. Yet, while the determinants of coral population resilience across species remain unknown, we are unable to predict the winners and losers across reef ecosystems exposed to increasingly variable conditions. Using annual surveys of 3171 coral individuals across Australia and Japan (2016-2019), we explore spatial variation across the short- and long-term dynamics of competitive, stress-tolerant, and weedy assemblages to evaluate how abiotic variability mediates the structural composition of coral assemblages. We illustrate how, by promoting short-term potential over long-term performance, coral assemblages can reduce their vulnerability to stochastic environments. However, compared to stress-tolerant, and weedy assemblages, competitive coral taxa display a reduced capacity for elevating their short-term potential. Accordingly, future climatic shifts threaten the structural complexity of coral assemblages in variable environments, emulating the degradation expected across global tropical reefs.Publisher PDFPeer reviewe