2021
Evaluation of thermo-hydraulic parameters during boiling and convective condensation inside channels with forced vibration
Concentration area:
Nature of the Project: Research
Start date:
Research line:
Project Status: In progress
Description:
The proposed project’s main objective is the theoretical and experimental evaluation of thermal and hydraulic parameters during boiling and convective condensation in horizontal circular channels, of conventional and reduced dimensions, subjected to forced vibration. Considering that fluid circulation in refrigeration systems is generally carried out through compressors, which eventually transmit vibrations to the system’s heat exchangers, this intensification mechanism is intrinsic to many systems. In the case of convective condensation inside horizontal channels, it is expected that the vibration of the channel favors the rupture or reduction in thickness of the liquid film along the wall, thus resulting in an increase in the heat transfer coefficient. For convective boiling inside channels subject to forced vibration, the rupture of liquid films along the wall can result in a reduction in the heat transfer coefficient or even in anticipation of wall drying. Therefore, the present research project aims to develop an apparatus for experimental evaluation of the heat transfer coefficient, pressure loss and flow patterns during boiling and convective condensation inside horizontal channels subject to forced vibration. The aim is to evaluate circular channels with internal diameters between 3 and 10 mm, flows of refrigerants R134a, R410A, R600a and R290, and saturation temperatures between -5 and 40 °C. Additionally, it is intended to use an actuator to impose vibration frequencies between 20 and 60 Hz, in order to cover the operating range of compressors driven by frequency inverters, with vertical, horizontal, axial and mixed vibration modes.
Team:
Students involved: Undergraduate: (0) / Specialization: (0) / Academic master’s degree: (2) / Professional master’s degree: (0) / Doctorate: (0) .
Members: Fabio Toshio Kanizawa – Coordinator / Leandro Alcoforado Sphaier – Member / Rian Maurício Santana – Member / Jaqueline Diniz da Silva – Member / Matheus Coitinho Constantino – Member / Brunno Abreu da Fonseca Vargas – Member.
Funders: Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do RJ – Financial assistance.
Novel Concepts for Transition Delay in Hypersonic Boundary Layers and their Optimization
Concentration area:
Nature of the Project: Research
Start date:
Research line:
Project Status: In progress
Description:
Use the solver developed at UFF under the AFOSR award FA9550-18-1-0419 to generate three-dimensional, disturbance-free, steady-states for the hypersonic laminar flow around a circular cone at an angle of attack. The method developed by the Research Collaborator has been successful in achieving convergence of one- and two-dimensional problems without spurious convectively unstable disturbances. The application to three-dimensional lifting bodies of interest to the Air Force will be studied during the visit. Previously designed three-dimensional grids will be used to calculate the solution with the new methods. The solution will be compared with previously computed and published solutions using the NASA solver VULCAN-CFD. Also, both linear and nonlinear stability analyzes will be performed with these disturbance-free base flow solutions using stability solver developed by the PI. The main goal is to uncover the mechanisms that lead to the appearance of stationary and convectively unstable modes in three-dimensional steady-state solutions, usually in the form of stationary crossflow vortices. The prediction of boundary layer transition with base flow solutions contaminated with spurious disturbances is not reliable. The calculation of the true basic state solutions without the spurious, grid-dependent disturbances will allow a reliable boundary-layer transition prediction with stability analysis techniques and facilitate the development of control strategies for such configurations. Budget: U$ 22,650.00.
Team:
Students involved: Academic master’s degree: (1) .
Members: Leonardo Santos de Brito Alves – Coordinator / Rodrigo Tavares Veloso – Member / Pedro Paredes – Member / Meelan Choudhari – Member.
Funders: Air Force Office of Scientific Research – Grant.