Jeferson Diehl de Oliveira

This study experimentally investigated the flow boiling pressure drop and flow patterns of R-600a in a horizontal multiport extruded tube with 1.47 mm ID. The experiments were carried out with mass flux between 35 and 165 kgm−2s−1 and heat flux ranging from 4.5 to 18.5 kWm−2 at a saturation temperature of 24 °C. Flow patterns and void fraction dist...

The current study developed an analytical model to predict the PV module's operating temperature based on an experimental database, which considers cell temperature, local meteorological data (irradiance, ambient temperature, wind velocity, and humidity), voltage, and current generated by the photovoltaic system associated with the purely resistive...

This investigation is devoted to analyzing hydrodynamic behavior and mass transfer performance in water electrolysis processes in an alkaline solution (30%wt KOH) under different current densities, using vertical stainless steel 304 electrodes (20 mm X 60 mm) with a separation of 20 mm between them in an electrolyzer made of glass (80 mm X 80 mm X...

Due to microscale effects, the segmented microchannels or micro pin fins heat sinks came out as a high thermal management solution. In this context, the present work analyzes the influence of different heights of micro pin fins with an aligned array and investigates their influence on pressure drop and heat transfer behavior. The HFE-7100 is used a...

Flow patterns are found in many processes involving multiphase flows in the industry. This experimental investigation focuses on the behavior of the vorticity fields found in the liquid-vapor interface during flow boiling of R-600a with heat flux varying from 5 to 20 kW/m^2 and fixed mass flux of 890 kg/(m^2s) at a saturation temperature of 17 ºC....

The studies carried out in the area of cell preservation have been of significant importance in recent years. This process, known as cryopreservation, has been used for decades and aims to preserve various cellular materials at cryogenic temperatures. Different methods allow cryopreservation, where the best known are the slow freezing and vitrifica...

This experimental and phenomenological study investigated fluctuations and characteristic frequencies of pressure drop and flow pattern during flow boiling of isobutane in a horizontal mini-channel 1.0 mm in diameter. The fluid was investigated at a saturation condition of 27°C, heat flux ranging between 1 and 80 kW/m² and mass flux ranging from 38...

The continuous search for techniques that optimize the heat transfer process, including phase-change processes, makes it necessary to understand the vapor bubble dynamics in the boiling process. The present work aims to study the bubble growth and departure process from an artificial cavity in the saturated nucleate boiling regime using HFE-7100 as...

Flow patterns are found in many processes involving multiphase flows in the industry. This experimental investigation focus on the behavior of the vorticity fields found in the liquid-vapor interface during flow boiling of R-600a with heat flux varying from 5 to 20 kW/m2 and fixed mass flux of 890 kg/(m2s) at a saturation temperature of 17 ºC. Test...

The studies carried out in the area of cell preservation have been of major importance in recent years. This process, known as cryopreservation, has been used for decades and aims to preserve various cellular materials at cryogenic temperatures. There are different methods that allow cryopreservation, where the best known are the slow freezing and...

This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanop...

Flow patterns are found in many processes involving multiphase flows in the industry. This study experimentally investigated the behavior of the velocity field in the liquid-vapor interface during flow boiling of isobutane at a saturation temperature of 17 °C with heat flux varying from 5 to 20 kW/m² and fixed mass flux of 890 kg/(m²s). Tests were...

The growing demand for techniques that optimize the heat transfer process, especially those involving phase change, makes it necessary to understand the dynamics of the vapor bubble in the boiling process. Thus, this study aims to analyze the bubble dynamics for pool boiling of HFE-7100 (at saturated conditions) on a plain copper surface. Experimen...

An experimental study was performed to investigate both flow patterns and heat transfer during flow boiling of propylene (R-1270) at a saturation temperature of 25 °C in a small circular tube with an inner diameter of 1.0 mm. The heat flux was varied from 5 to 60 kW/m² and the mass flux ranged from 240 up to 480 kg/m²s, with vapor quality ranging f...

The dynamics of time series obtained from an optical sensor for analysis of flow patterns has been investigated during flow boiling of hydrocarbons in a horizontal tube with 1 mm inner diameter. The tests were performed with the refrigerants R-600a, R-290 and R-1270 at 17 °C saturation temperature, with mass flux ranging from 240 to 480 kg/(m²s), c...

Evaporators with mini and micro channels are one of the main focuses in the design and development of equipment applied to compact refrigeration systems. The objective of this work is to investigate pressure drop of natural refrigerant, isobutane (R-600a), in the single-phase flow through two small tubes, with 1.0 mm and 2.6 mm of internal diameter...

Flow patterns and local heat transfer coefficients were investigated experimentally during flow boiling of R-290 in a tube with inner diameter equal to 1.0 mm. The tests were conducted at heat fluxes ranging from 5 to 60 kW/m², mass flux from 240 to 480 kg/(m²s) at 25 °C saturation temperature. Both mass flux and heat flux have a significant influe...

Pressure drop for propane and isobutane were performed in a horizontal small tube of stainless steel with 1.0 mm inner diameter. The tests were conducted at mass fluxes from 240 to 480 kg m⁻²s⁻¹ and heat fluxes from 5 to 60 kW m⁻² at 25 °C saturation temperature. The effect of flow patterns, mass flux, vapour quality and heat flux are discussed. St...

The local heat transfer coefficient and flow pattern were studied experimentally during flow boiling of R-600a inside a horizontal small tube (inner diameter ID = 1.0 mm). The effects of heat flux, mass velocity and vapor quality have been investigated. The tests were conducted at heat fluxes from 5 to 60 kW m⁻², mass velocity from 240 to 480 kg m⁻...

Evaporators of small and medium refrigeration systems, as in commercial and automobile air conditioning applications, are being studied to develop more compact and lighter equipment, that reach good thermal performance and reliability, with low pressure drop. In this way, evaporators are being designed with small channels and materials like aluminu...