Compound effect of EHD and surface roughness in pool boiling and CHF with R-123

This article is a post-print version of the fianl published article which may be accessed at the link below.Saturated pool boiling of R-123 at 1 bar, including the critical heat flux (CHF), was enhanced by modifying the surface characteristics and applying a high intensity electrostatic field, the latter termed electrohydrodynamic (and abbreviated EHD) enhancement. The heat flux was varied from very low values in the natural convection regime up to CHF. Experiments were performed with increasing and decreasing heat flux to study boiling hysteresis without and with EHD. Boiling occurred on the sand blasted surface of a cylindrical copper block with embedded electrical heating elements, with standardized surface parameter Pa = 3.5 μm. The electric field was generated by a potential of 5 kV to 25 kV, applied through a 40 mm diameter circular electrode of ss-304 wire mesh, aperture size 5.1 mm, located at distances of 5 - 60 mm from the surface, with most of the data obtained for 20 mm. The data for the rough surface were compared with earlier data for a smooth surface and indicated a significant increase in the heat transfer rates. EHD produced a further increase in the heat transfer rates, particularly at low heat flux values and near the CHF. Boiling hysteresis was reduced progressively by EHD and eliminated at high field strength.This work was supported by Government of Pakistan under a scholarship programme

Desempenho e uniformidade da distribuição de água de um pivô central Performance of a center pivot irrigation system and irrigation distribution uniformity

O objetivo deste experimento foi avaliar as características de desempenho de um equipamento de irrigação pivô central, de baixa pressão, bem como determinar a uniformidade de distribuição de água, tanto abaixo como acima da superfície do solo. Para a avaliação do desempenho do sistema utilizaram-se os coeficientes de uniformidade de Christiansen (CUC) e de distribuição (CUD), calculados a partir de dados da precipitação dos aspersores. O pivô central foi ensaiado nas velocidades de 25%, 50%, 75% e 100% da velocidade máxima de deslocamento do equipamento. Utilizou-se quatro linhas de coletores, uniformemente espaçados. Os valores encontrados do CUC e o CUD foram superiores ao mínimo recomendado para a cultura do milho, confirmando o bom desempenho do pivô central. Em todas as profundidades do solo estudadas os coeficientes de uniformidade foram superiores aos obtidos acima do solo, ocorrendo um aumento nos valores dos coeficientes de uniformidade abaixo da superfície do solo com o tempo.<br>The objective of this work was to evaluate some characteristics of a center pivot irrigation system equipament, as well as to determine the water distribuition uniformity, under and over the soil surface. The Christiansen uniformity coefficient (CUC) and distribuition (CUD) were used to evaluate the system. A low pressure center pivot was tested in four different speeds: 25%, 50%, 75% and 100% of the timer sensor, and in four collectors Unes spaced. Results indicated that both coeficients presented good performance. The values of CUC and CUD were above the minimum recommended for na irrigated corn field. The uniformity coefficients in all depths of the soil were higher than the above the soil surface. Howerer, the uniformity under soil surface increased with the time in all depths

Curvas de desempenho de válvulas reguladoras de pressão novas e com diferentes tempos de utilização Performance curves of new and used pressure regulating valves

O desempenho de uma válvula reguladora de pressão, fabricada pela Fabrimar, Modelo Exact-20-Ref. RP-3-20-3/4"FF, utilizada em pivô central, foi avaliado em laboratório, conforme as normas ISO (1993). Este trabalho foi desenvolvido no Laboratório de Irrigação do Departamento de Engenharia Rural, ESALQ/USP, utilizando-se reguladores de pressão novos e com diferentes tempos de emprego no campo. As curvas de desempenho das válvulas novas satisfizeram as condições exigidas pela norma, caracterizando o regulador como do tipo A, para as velocidades de referência de 0,5 m s-1 (vazão de 0,57 m³ h-1) até 4,0 m s-1 (vazão de 4,50 m³ h-1) e várias pressões de entrada, sendo também elaborado um modelo estatístico para a pressão de saída do regulador novo, com uma vazão e uma pressão de entrada. Foram coletadas, de diversos sistemas tipo pivô central e de diferentes vãos, válvulas reguladoras de pressão do mesmo modelo, que possuíam tempos de uso de 2000, 2500, 6000, 8500, 9000 e 10000 h e, também, com diferentes qualidades de água utilizadas. Os ensaios seguiram os mesmos padrões dos novos, realizando-se uma análise estatística dos dados. Apesar dos desgastes provocados pela água de má qualidade e dos vazamentos apresentados, o desempenho hidráulico das válvulas com tempo de uso até 6000 h, não diferiu do desempenho das novas, para pressões de entrada até 826,3 kPa e velocidades de referência até 2,5 m s-1. O desempenho dos reguladores de pressão com tempos de uso iguais ou superiores a 8500 h, não se manteve semelhante ao do regulador novo, especialmente para pressões de entrada superiores a 481,7 kPa.<br>The performance of a pressure regulator valve, manufactured by Fabrimar (Model Exact-20-Ref. RP-3-20-3/4"FF), for central pivot applications, was evaluated in the laboratory following the ISO 1993 norms. The tests were conducted in the Laboratory of Irrigation of the Department of Rural Engineering, ESALQ/USP. The performance curves of the new valves satisfied the conditions established by the norm, characterizing the regulator as type A, for reference velocity of 0.5 m s-1 (flow of 0.57 m³ h-1) up to 4.0 m s-1 (flow of 4.50 m³ h-1) and several inlet pressures. A model for the outlet pressure of the new regulator, as a function of flow and inlet pressure, was also developed. Pressure regulators of a given model were collected from several central pivot systems and from different spans in the system, such that an array of pressure regulators with 2000, 2500, 6000, 8500, 9000 and 10000 h of operation at several water qualities were obtained. These pressure regulator were evaluated according to ISO 1993 as well. In spite of the effect of water sediments on the pressure regulator and observed leaks, the hydraulic performance of the valves with 6000 h did not differ in comparison to the new ones, for inlet pressures of 826.3 kPa and reference velocities up to 2.5 m s-1. The performance of the pressure regulators with 8500 h or more of operation did not perform as well as the new ones, especially for upper inlet pressures over 481,7 kPa

Pediatric Mesothelioma Tumors: The European Expert Group Contribution.

Background and Aims: In adults with mesothelioma, cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRSHIPEC) is a standard of care in limited tumor, but long-term survival is very uncommon. Very little is known about the characteristics of this tumor in the pediatric population. Methods: The EXPeRT group of very rare pediatric tumors reviewed retrospectively children and youths ( 6421 year) diagnosed in Europe with mesothelioma tumors treated between 1987 and 2018. Results: Thirty three patients were identified, 14 males and 18 females. Only one exposure to asbestos was documented. Primary tumor was located into the peritoneum (23 patients), pleura (2), vagina (2), pericardium (1), and in multiple sites (5). Histology was multicystic peritoneal mesothelioma (MCPM; 6 patients; median age 14.1year, range 2.2-21.1) or malignant (27 patients; median age 13.4 year, range 0.2- 18.7): epithelioid (21), biphasic (4) and unspecified (2). All patients with MCPM are alive despite 4 peritoneal relapses, after surgery (5 patients) and CRS-HIPEC (1pt). Metastasis at diagnosis were present in 9/27 patients with malignant mesothelioma. Among them, first line treatment was heterogeneous: preoperative chemotherapy (14 cases), exclusive surgery (3 cases), exclusive chemotherapy (5 cases), adjuvant chemotherapy (3 cases) or palliative (2 cases). Response rate to cisplatin-pemetrexed was 50% (6/12 cases) with no response to other regimens (0/12 cases). Two patients have long term tumor controlwith targeted therapy. CRS-HIPEC was performed in 19 patients (upfront 3 cases, after neoadjuvant therapy 12 patients, or after tumor progression 6 cases, including 3 twice). After a median follow-up of 6.7y (range, 0-20), 5 year overall and event free survivals are respectively 82.3% (95%IC 67.8-99.9) and 45.1% (95%IC 28.4-71.7). Conclusions: Pediatric Mesothelioma is exceptional and seems to be different from its adult counterpart with few asbestos exposures and a better outcome. Cisplatin-pemetrexed regimen showed some efficacy. Relapses could be salvaged with active therapy including CRS-HIPEC. Targeted therapy should be considered