Heat transfer enhancement of concentrated solar absorber using hollow cylindrical fins filled with phase change material

A concentrated solar absorber with finned phase change materials was experimentally studied using a Scheffler type parabolic dish concentrator. The absorber's inner surface was fixed with hollow cylindrical containers filled with phase change material (PCM) for heat transfer augmentation. The absorber's selected PCM was acetanilide (Melting point of 116 °C)—the cylindrical capsules protruding into the fluid side to create turbulence and mixing and acting as fins. The absorber surface temperature was observed to be about 130–150 °C during the outdoor tests while passing fluid through the absorber. The fluid flow rate varied from 60 to 100 kg/h during the outdoor experiments. The peak energy and exergy efficiency of parabolic dish collector (PDC) at the fluid flow rate of 80 kg/h with PCM integrated solar absorber was found to be about 67.88% and 6.96%, respectively. The integration of cylindrical PCM containers resulted in more heat transfer augmentation in the solar absorbers. The optimized solar absorber could be suitable for various applications like steam generation, biomass gasification, space heating, and hydrogen generation.     

Optimization of parameters in solar thermal collector provided with impinging air jets based upon preference selection index method

The present study examines the effect of flow and geometric parameters on the performance of solar thermal collector provided with impinging air jets. The investigation has been carried out in terms of performance defining criterions which are pertinent to determine the optimal design of impinging jet solar thermal collector. The experimental investigation indicated that the impinging air jets enhances the thermal performance but at the same time the friction power penalty also increases which depress the overall performance of the system. In view of this the preference selection index (PSI) approach based methodology has been applied using various performance criterions in order to determine the optimal design of the parameters which deliver maximum thermal performance with minimal increase in friction factor inside the collector duct. The optimum configuration of the parameters obtained as a result of proposed method is: streamwise pitch ratio of 0.435; spanwise pitch ratio of 0.869; jet diameter ratio of 0.065 and flow Reynolds number of 16,000.     

Locally one-dimensional-alternating segment explicit–implicit and locally one-dimensional-alternating segment Crank–Nicolson methods for two-dimension parabolic equations

In the paper two new locally one-dimensional alternating segment schemes for solving the 2-D parabolic problems are developed. The parabolic problems can be solved efficiently over decomposed sub-domains. Two schemes are proved to be unconditionally stable and numerical experiments show the validity of the schemes.     

Electrostatic dust collectors compared to inhalable samplers for measuring endotoxin concentrations in farm homes

Paired electrostatic dust collectors (EDCs) and daily, inhalable button samplers (BS) were used concurrently to sample endotoxin in 10 farm homes during 7‐day periods in summer and winter. Winter sampling included an optical particle counter (OPC) to measure PM_2.5 and PM_2.5–10. Electrostatic dust collectors and BS filters were analyzed for endotoxin using the kinetic chromogenic Limulus amebocyte lysate assay. Optical particle counter particulate matter (PM) data were divided into two PM categories. In summer, geometric mean (geometric standard deviation) endotoxin concentrations were 0.82 EU/m³ (2.7) measured with the BS and 737 EU/m² (1.9) measured with the EDC. Winter values were 0.52 EU/m³ (3.1) for BS and 538 EU/m² (3.0) for EDCs. Seven‐day endotoxin values of EDCs were highly correlated with the 7‐day BS sampling averages (r = 0.70; P < 0.001). Analysis of variance indicated a 2.4‐fold increase in EDC endotoxin concentrations for each unit increase of the ratio of PM_2.5 to PM_2.5–10. There was also a significant correlation between BS and EDCs endotoxin concentrations for winter (r = 0.67; P < 0.05) and summer (r = 0.75; P < 0.05). Thus, EDCs sample comparable endotoxin concentrations to BS, making EDCs a feasible, easy to use alternative to BS for endotoxin sampling.     

Effects of residual concentration of collector CTAC on flotation behavior of illite

ABSTRACT

In present study, illite flotation behavior with Cetyl Trimethyl Ammonium Chloride (CTAC) as the collector has been studied to investigate the effects of its residual concentration on froth stability and flotation. Results showed that, with increasing conditioning time, the residual concentration (frother concentration) and froth height decreased simultaneously, while the adsorbed amount (particle hydrophobicity) increased. Increasing CTAC conditioning time decreased the residual concentration in solutions, resulting in poor froth stability and flotation recovery at high pH; the adsorption rate of CTAC on illite surface was relatively high at higher pH due to strong electrostatic mechanism, making CTAC residual concentration decrease.     

UC3901在行波管收集极电源中的应用

介绍了行波管的性能,阐述了收集极电源的特点,论述了UC3901在行波管收集极电源中的应用。     

Distributed mathematical model supporting design and construction of solar collectors for drying

Coupled partial differential equations were developed to investigate which collector lengths are appropriate for drying and adsorbent regeneration under prevailing Ghanaian weather. Unlike approaches based on empirical data, the numerical model is more flexible. Effects of operational and design variables on outlet temperature and performance were systematically studied. Collector length and air speed affect performance indicators. Operational overall heat loss coefficient, an important characteristic of the collector, is not constant but varies during the day. With plausible physical parameters, the model describes the experimental data well. Collector lengths of 1.5 and 4.5?m suited drying and regeneration, respectively.     

基于合肥市硬塑至坚硬粘土的大断面顶管施工技术研究与应用

合肥市塘西河上游雨水分流工程位于硬塑至坚硬状态的粘土层中，土体的干强度及韧性高。本文针对这一特殊地质条件，对顶管施工技术进行了研究，在不改变顶管机械整体状态下对顶管刀盘进泥孔和刀具进行了设计改进，顶管施工进度提高了近二倍，解决了在此土层中顶管施工顶进慢的施工难题，取得了较好的经济效益，可为类似工程提供借鉴。     

一种含羟基烷叉双膦酸钛铁矿捕收剂的合成及浮选性能研究

采用油酸与亚磷酸、三氯化磷反应,合成了一种含羟基烷叉双膦酸的钛铁矿捕收剂,并进行了钛铁矿浮选试验,获得了钛精矿产率38.82%,TiO2品位47.52%,回收率75.82%的技术指标。该捕收剂选择捕收性能优良,合成工艺简单,利于在工业上推广应用。     

Significant impact of the current collection material and method on the performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ electrodes in solid oxide fuel cells

The effects of the current collection material and method on the performance of SOFCs with Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) cathodes are investigated. Ag paste and LaCoO₃ (LC) oxide are studied as current collection materials, and five different current collecting techniques are attempted. Cell performances are evaluated using a current-voltage test and electrochemical impedance spectra (EIS) based on two types of anode-supported fuel cells, i.e., NiO + SDC|SDC|BSCF and NiO + YSZ|YSZ|SDC|BSCF. The cell with diluted Ag paste as the current collector exhibits the highest peak power density, nearly 16 times that of a similar cell without current collector. The electrochemical characteristics of the BSCF cathode with different current collectors are further determined by EIS at 600 °C using symmetrical cells. The cell with diluted Ag paste as the current collector displays the lowest ohmic resistance (1.4 Ω cm²) and polarization resistance (0.1 Ω cm²). Meanwhile, the surface conductivities of various current collectors are measured by a four-probe DC conductivity technique. The surface conductivity of diluted Ag paste is 2-3 orders of magnitude higher than that of LC or BSCF. The outstanding surface conductivity of silver may reduce the contact resistance at the current collector/electrode interface and, thus, contributes to better electrode performance.