FLAT PLATE PULSATING HEAT PIPES WITH DIFFERENT CHANNEL GEOMETRIES FOR HIGH HEAT FLUX APPLICATIONS

The thermal performance of flat plate pulsating heat pipes with differentchannel geometries was performed in this experimental work. The testswere accomplished with two channel profiles, round and grooved. One ofthe channel geometries, located on the evaporator, can be considered novel,consisting of a round channel with two lateral grooves. Diffusion bondingtechnology was used to manufacture the PHPs made of two copper flatplates. Distilled water was used as the working fluid with a filling ratio of50% (17.9 ml) of the total volume. The pulsating heat pipes were tested atone position (vertical) under heat loads from 20 up to 2000 W. Theexperimental results showed that both flat plate pulsating heat pipesoperates successfully for high heat fluxes. The lateral grooves reduced thethermal resistance, being principally efficient in lower loads. Besides that,the novel channel considerably anticipated the operation startup. Therefore,a much better performance was obtained by the grooved channel PHP,which was constructed from a simple, low cost modification of thefabrication process

EXPERIMENTAL ANALYSIS OF A SCREEN-COVERED GROOVE HEAT PIPE

In this research, a heat pipe with screen-covered groove capillary structure was experimentally analyzed. The heat pipe was manufactured from a copper tube with the external diameter of 9.45mm, inner diameter of      6.20mm, and a total length of 200mm. A Wire Electrical Discharge Machining, or Wire-EDM, was used to manufacture axial microgrooves in the heat pipe. A layer of phosphor bronze mesh #100 completed the capillary structure. Distilled water was the working fluid and the loading filling ratio was 60% of the evaporator volume. The condenser was cooled by air forced convection, the adiabatic section was insulated with fiberglass, and the evaporator was heated by an electrical resistor and it was insulated from the environment with aeronautic insulation. The heat pipe was tested in horizontal position, under different heat loads varying from 5 up to 30W. The experimental results showed that the screen-covered groove worked satisfactorily as a capillary structure

Recuperação de larvas de nematóides tricostrongilídeos em fezes de ovinos em sistemas de monocultivo e silvipastoril

Sistemas integrados de produção como o silvipastoril pode ser uma opção de quebra de paradigmas para o pecuarista, independentemente da espécie animal em questão. O equilíbrio entre os fatores que compõe o sistema é fundamental para o desempenho animal, entre estes fatores podemos destacar a saúde animal devido à complexidade de interações e aspecto multifatorial das doenças parasitárias. O objetivo deste estudo foi avaliar a recuperação de larvas de nematóides tricostrongilídeos (L3) em fezes no sistema de integração Pecuária-Floresta e sistema de pastejo convencional, avaliando a sazonalidade destes parasitas, sua sobrevivência no ambiente e as condições microclimáticas dos sistemas avaliados. O estudo foi implantado em novembro de 2013 no campo experimental da Embrapa Agrossilvipastoril, município de Sinop/MT, onde foi conduzido até setembro de 2014 para que fossem realizadas avaliações nas quatro estações do ano. Os módulos experimentais são compostos por 60 amostras de 20 gramas de fezes de ovinos com aproximadamente sessenta mil ovos de nematóides tricostrongilídeos. A cada estação do ano estas unidades são dispostas de maneira inteiramente casualizada em dois diferentes arranjos de pastagem, sendo estes caracterizados como pastagem a pleno sol (Trat. A) e pastagem integrada a componente florestal com renques triplos de eucalipto com espaçamento entre renques de 15 metros (Trat. B). Quatorze dias após a deposição das fezes, em três horários distintos (às 06:00, 12:00 e 18:00 horas) foram coletadas as amostras de fezes remanescentes na superfície. Tais amostras foram encaminhadas ao laboratório para a obtenção do número de L3/kg de matéria seca. Com base no teste de Qui-Quadrado (95% de confiança), a média de L3 nas amostras de fezes do Trat. B foi significativamente superior ao Trat. A, 12.385 e 10.246, respectivamente. Avaliando-se as diferentes estações do ano, a média de L3 recuperadas foi superior no mês de junho (26.110), seguido pela média de março (5.728,84) e dezembro (2108,51), havendo diferença estatística entre todos os períodos. Com relação aos horários de coleta, foram recuperadas um maior número de L3 às 12:00 horas (12.638), mas não houve diferença significativa entre as médias às 06:00 (10.927) e 18:00 horas (10.382). Com base nos resultados, pode-se concluir que as estações do ano foram capazes de influenciar o número de larvas infectantes recuperadas nas fezes independentemente dos tratamentos, porém o sistema silvipastoril apresentou uma maior média quando comparado ao sistema de monocultura de pastagem. Pode-se concluir ainda que o horário de coleta de amostras pode interferir com o resultado de L3 recuperadas nas fezes

THERMAL PERFORMANCE OF THERMOSYPHON FOR DIFFERENT WORKING FLUIDS

In this paper, an experimental investigation was performed of the thermal performance of different working fluids in thermosyphons that can be used in thermal control of electronic equipment. The working fluids were considered acetone, water, ethanol, and methanol. The thermosyphon are manufactured of copper with an outer diameter of 9.45 mm, an inner diameter of 7.75 mm, a total length of 200 mm, whereas an evaporator of 80 mm length, an adiabatic region of 20 mm in length and a condenser of 100 mm in length. They were loaded with 1.39 ml of the working fluid, corresponding to a filling ratio of 40% of the evaporator volume. Experimental tests were performed in a vertical position considering thermal loads between 5W and 25W. The thermosyphons operated satisfactorily in all the tests. The operating temperature distribution as a function of time and the heat resistance behavior as a function of power dissipation have been presented for each analyzed working fluid. These results indicated that acetone is the working fluid that has the best thermal performance

Thermal Analysis of a Finned Thermosyphon for Heat Exchanger Applications

A thermosyphon is a gravity-assisted heat pipe used to improve the heat transfer in several applications. In this paper, a thermal analysis of a finned thermosyphon for heat exchanger applications was experimentally researched. The thermosyphon was manufactured from a copper tube the external diameter of 9.45 mm, the inner diameter of 7.75 mm, and a total length of 200 mm. The working fluid used was water with a filling ratio of 40% of the evaporator volume. The condenser was cooled by air forced convection, the adiabatic section was insulated with fiberglass and the evaporator was heated by an electrical resistor. Experimental tests were performed to a heat load from 5 up to 50W at vertical position (evaporator above condenser). As a result of the research, the thermosyphon operated satisfactorily to the tested position. Also, the finned thermosyphon obtained better thermal performance than the un-finned condenser, proving the effectiveness of the fin application

Characterization of a Copper Powder for Heat Pipe Wick Applications

In powder metallurgy, it is necessary to know the powder's nature to understand how the processing of a powder occurs. In this paper, a characterization of a copper powder for heat pipe wick applications was experimentally done. The copper powder manufacturing method was atomization. This metallic powder was characterized by Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectrometry (ED-XRF), and Laser Diffraction Granulometry. As a result, the purity and the shape are compatible with the powder manufacturing method and great for wicks. Also, the copper powder has a unimodal distribution that is excellent for capillary structures

A test of the hypothesis that oxalate secretion produces proximal tubule crystallization in primary hyperoxaluria type I

The sequence of events by which primary hyperoxaluria type 1 (PH1) causes renal failure is unclear. We hypothesize that proximal tubule (PT) is vulnerable because oxalate secretion raises calcium oxalate (CaOx) supersaturation (SS) there, leading to crystal formation and cellular injury. We studied cortical and papillary biopsies from two PH1 patients with preserved renal function, and seven native kidneys removed from four patients at the time of transplant, after short-term (2) or longer term (2) dialysis. In these patients, and another five PH1 patients without renal failure, we calculated oxalate secretion, and estimated PT CaOx SS. Plasma oxalate was elevated in all PH1 patients and inverse to creatinine clearance. Renal secretion of oxalate was present in all PH1 but rare in controls. PT CaOx SS was >1 in all nonpyridoxine-responsive PH1 before transplant and most marked in patients who developed end stage renal disease (ESRD). PT from PH1 with preserved renal function had birefringent crystals, confirming the presence of CaOx SS, but had no evidence of cortical inflammation or scarring by histopathology or hyaluronan staining. PH1 with short ESRD showed CaOx deposition and hyaluronan staining particularly at the corticomedullary junction in distal PT while cortical collecting ducts were spared. Longer ESRD showed widespread cortical CaOx, and in both groups papillary tissue had marked intratubular CaOx deposits and fibrosis. CaOx SS in PT causes CaOx crystal formation, and CaOx deposition in distal PT appears to be associated with ESRD. Minimizing PT CaOx SS may be important for preserving renal function in PH1

Critical Assessment of Single-Use Ureteroscopes in an In Vivo Porcine Model

Methods A female pig was placed under general anesthesia and positioned supine, and retrograde access to the renal collecting system was obtained. The LithoVue (Boston Scientific) and Uscope (Pusen Medical) were evaluated by three experienced surgeons, and each surgeon started with a new scope. The following parameters were compared between each ureteroscope: time for navigation to upper and lower pole calyces with and without implements (1.9 F basket, 200 μm laser fiber, and 365 μm laser fiber for upper only) in the working channel and subjective evaluations of maneuverability, irrigant flow through the scope, lever force, ergonomics, and scope optics. Results Navigation to the lower pole calyx was significantly faster with LithoVue compared to Uscope when the working channel was empty (24.3 vs. 49.4 seconds, p < 0.01) and with a 200 μm fiber (63.6 vs. 94.4 seconds, p=0.04), but not with the 1.9 F basket. Navigation to the upper pole calyx was similar for all categories except faster with LithoVue containing the 365 μm fiber (67.1 vs. 99.7 seconds, p=0.02). Subjective assessments of scope maneuverability to upper and lower pole calyces when the scope was empty and with implements favored LithoVue in all categories, as did assessments of irrigant flow, illumination, image quality, and field of view. Both scopes had similar scores of lever force and ergonomics. Conclusions In an in vivo porcine model, the type of single-use ureteroscope employed affected the navigation times and subjective assessments of maneuverability and visualization. In all cases, LithoVue provided either equivalent or superior metrics than Uscope. Further clinical studies are necessary to determine the implications of these findings