Study on variable condition model for steam turbine based on internal and external characteristics

It is not easy to carry out the detailed variable condition calculation of steam turbine in engineering application. In this paper, a variable condition calculation model based on the internal and external characteristics of steam turbine is proposed, and a variable condition calculation model of constant power and constant flow is established. The model is applied to calculate 75% THA, 50%THA, typical industrial and heating extraction conditions of a subcritical 330 MW unit. The error is small compared with the design value, and the calculation accuracy meets the requirements. The results show that the model has high accuracy and can meet the requirements of engineering application.

Investigating the mechanotransduction of transient shear stress mediated by Piezo1 ion channel using a 3D printed dynamic gravity pump

Microfluidic systems are widely used for studying the mechanotransduction of flow-induced shear stress in mechanosensitive cells. However, these studies are generally performed under constant flow rates, mainly, due to the...

Investigate and analysis the efficiency of photovoltaic system with active cooling based on numerical method

<p style="margin: 0in 0in 10.6pt 0.5pt; text-align: justify; text-indent: -0.5pt;">The aim of this research is to establish a simulation model to examine the performance and working efficiency of a solar cell system by using computational fluid dynamics (CFD). The proposed model consists of a water feed tube and an absorber plate, as well as a convection heat transfer system, the ansys fluent system simulation program was used. The electrical output of the panel and its efficiency have been investigated and the effect of changes in the intensity of solar radiation on the temperature of the liquid and the absorption plate on the performance of the system have been studied. A dynamic analysis of the thermal hybrid system was performed with a circulation pump. Calculations were performed using a detailed mathematical model. The analysis was performed in three cases, the first case when the system has no cooling, in the second case with constant flow, and in the third case when the pump was optimized. Finally, numerical results were compared with the practical reference results. Both results are in good agreement. The results obtained showed that the system with optimization case give a good improvement in efficiency with low reduction of the thermal efficiency compared to a constant flow.</p>

Improving the Hydraulic Effects Resulting from the Use of a Submerged Biofiter to Enhance Water Quality in Polluted Streams

Water scarcity is one of the most serious problems facing many countries. In addition, water pollution could lose more water. A submerged biofilter (SB) is used to enhance the self-purification process in polluted streams. However, most previous studies have focused on the efficiency of SB to remove pollutants and there is a lack of studies investigating the hydraulic changes in streams. The current paper aimed to study the hydraulic effects of SB on the flow behavior in streams and how to improve it. An empirical equation for determining the flow rate through SB was developed. Different cases were studied to improve the hydraulic effects resulting from the use of SB. The effect of increasing SB length was tested using different SB lengths. The results showed that increasing the length increased the upstream water depth (h1) and relative heading up (h1/h2). In the second case, comparison between continuous and fragmented SB was tested. The results showed that a fragmented biofilter increased the upstream water depth and the relative heading up. Case three tested the effect of SB height. Different SB heights were tested with a fixed length and constant flow rate. The results revealed that the upstream water depth and relative heading up decreased when the biofilter height decreased. Case four tested the effect of SB with a fixed volume and constant flow rate. In this case, the length and height of SB were changed where the volume was fixed. The results showed that the relative heading up decreased when the SB height decreased and the length increased, which revealed that the SB height can improve the hydraulic impacts. Finally, the use of SB to improve the water quality in polluted streams led to an increase of the relative heading up, which can be reduced by decreasing the height of SB.

Net Water Drag Coefficient during High Temperature Operation of Polymer Electrolyte Fuel Cells

For polymer electrolyte fuel cell (PEFC) systems in vehicle applications, net water drag coefficient ( ) is an essential index and must be negative for system operation. The feasibility of PEFC operation at temperatures over 100C was examined here by measuring and comparing the current density (j) - characteristics using PEFCs with either an Aquivion or Nafion membrane. The effect of cell temperature ( ) on was evaluated at range from 80 to 120C. Results clearly demonstrated that, for both membrane types, significantly increased increasing . Results also confirmed that, at a constant flow rate of H2 at the anode, decreased with decreasing stoichiometric ratio of air ( ), although the effect of on was relatively small. Finally, the effect of relative humidity (RH) balance of supplied gases in both sides (anode/cathode) on water transport at temperature up to 120C was examined for the Aquivion cell. Results revealed that could be significantly decreased by decreasing the RH of hydrogen supplied to the anode (RHA) and that the control of RHA is an effective method for lowering at elevated temperature operation.

Dissociation and recombination in the electrolyte flow model

We propose a one-dimensional model for the dilute aqueous solution of NaCl which is treated as an incompressible fluid placed in the external electric field. This model is based on the Poisson-Nernst-Planck system of equations, which also contains the constant flow velocity as a parameter and considers the dissociation and the recombination of ions. We study the steady-state solution analytically and prove that it is a stable equilibrium. Analyzing the numerical solutions, we demonstrate the importance of dissociation and recombination for the physical meaningfulness of the model.

Dynamic flow and shear stress as key parameters for intestinal cells morphology and polarization in an organ-on-a-chip model

Gut-on-a-chip microfluidic devices have emerged as versatile and practical systems for modeling the human intestine in vitro. Cells cultured under microfluidic conditions experience the effect of shear stress, used as a biomechanical cue to promote a faster cell polarization in Caco-2 cells when compared with static culture conditions. However, published systems to date have utilized a constant flow rate that fails to account for changes in cell shear stress ($${\tau }_{c}$$ τ c ) resulting from changes in cell elongation that occur with differentiation. In this study, computational fluid dynamics (CFD) simulations predict that cells with villi-like morphology experience a $${\tau }_{c}$$ τ c higher than bulge-like cells at the initial growth stages. Therefore, we investigated the use of a dynamic flow rate to maintain a constant $${\tau }_{c}$$ τ c across the experiment. Microscopic assessment of cell morphology and dome formation confirmed the initiation of Caco-2 polarization within three days. Next, adopting our dynamic approach, we evaluated whether the following decreased flow could still contribute to complete cell differentiation if compared with the standard constant flow methodology. Caco-2 cells polarized under both conditions, secreted mucin-2 and villin and formed tight junctions and crypt-villi structures. Gene expression was not impacted using the dynamic flow rate. In conclusion, our dynamic flow approach still facilitates cell differentiation while enabling a reduced consumption of reagents.