scholarly journals Design, Simulation, and Fabrication of a Copper–Chrome-Based Glass Heater Integrated into a PMMA Microfluidic System

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1067
Author(s):  
Santiago Tovar ◽  
Cesar A. Hernández ◽  
Johann F. Osma
Keyword(s):  
Heat Transfer ◽  
Heating Surface ◽  
Fluid Flows ◽  
Microfluidic System ◽  
Heat Transfer Process ◽  
Heater Surface ◽  
Thermal Flow ◽  
Flow Rates ◽  
Thermal Flow Sensor ◽  
Heating Behavior

In this paper, the development of a copper–chrome-based glass microheater and its integration into a Polymethylmethacrylate (PMMA) microfluidic system are presented. The process highlights the importance of an appropriate characterization, taking advantage of computer-simulated physical methods in the heat transfer process. The presented system architecture allows the integration for the development of a thermal flow sensor, in which the fluid flows through a 1 mm width × 1 mm length microchannel across a 5 mm width × 13 mm length heating surface. Using an electrothermal analysis, based on a simulation and design process, the surface heating behavior curve was analyzed to choose a heating reference point, primarily used to control the temperature point within the fluidic microsystem. The heater was characterized using the theory of electrical instrumentation, with a 7.22% error for the heating characterization and a 5.42% error for the power consumption, measured at 0.69 W at a temperature of 70 °C. Further tests, at a temperature of 115 °C, were used to observe the effects of the heat transfer through convection on the fluid and the heater surface for different flow rates, which can be used for the development of thermal flowmeters using the configuration presented in this work.

Solar-Powered Water Distillation System

2013 ◽  
Author(s):  
Abdlmonem Beitelmal ◽  
Drazen Fabris ◽  
Reece Kiriu
Keyword(s):  
Heat Transfer ◽  
Control System ◽  
Experimental Testing ◽  
Heat Transfer Process ◽  
Heat Transfer Fluid ◽  
Manufacturing Cost ◽  
Flow Rates ◽  
Water Distillation ◽  
Distillation System ◽  
Solar Powered

Future water demand is predicted to increase while current resources are continuously depleted. In this paper, a standalone off-the-grid water purification system is designed to provide an economically sustainable model for delivering clean drinking water is presented. This system utilizes concentrated heat generated by solar parabolic troughs to boil brackish water for the distillation process. The water vapor is then condensed into clean drinkable water in a water collection tank. The process of designing and optimizing the solar-powered distillation system (Heat exchanger, boiler, parabolic troughs, tracking and control system, photovoltaic panels and vapor and the heat transfer fluid pumps) and specifically the process of fabricating the parabolic trough is presented and discussed in details. Two troughs were designed and fabricated each with an area of 1.5 m2 (16 ft2). Each trough provides approximately 125 watts/ft. Duratherm 450, a non-toxic, non-hazardous heat transfer fluid (HTF) is selected for the solar trough hot loop. Additional system performance analysis was conducted through experimental testing and through a virtual system model utilizing the Engineering Equation Solver (EES). EES is used to model the heat transfer process of the overall distillation system and a range of optimum HTF flow rates were determined. The experimental results show an increase in water temperature within the boiler for the new range of HTF flow rates. In addition, the results show that the solar troughs are more robust, less expensive to manufacture, operate at a higher temperature and provide a higher performance when compared to a system that utilizes thermal panels. The overall system manufacturing cost is approximately $6000, which includes tracking, a control system and other required distillation components. This system is designed to fit into a standard 20-foot shipping container for ease of transportation worldwide.

scholarly journals Thermal Flow Sensors for Harsh Environments

2017 ◽  
Author(s):  
Vivekananthan Balakrishnan ◽  
Hoang-Phuong Phan ◽  
Toan Dinh ◽  
Dzung Viet Dao ◽  
Nam-Trung Nguyen
Keyword(s):  
Fluid Flows ◽  
Harsh Environments ◽  
Thermal Flow ◽  
Hostile Environment ◽  
Flow Sensors ◽  
Flow Sensing ◽  
Thermal Flow Sensor ◽  
Transduction Mechanisms ◽  
Operational Modes ◽  
Higher Sensitivity

Flow sensing in hostile environment is of increasing interest for applications in automotive, aerospace, and chemical and resource industries. Compared to their counterparts, thermal flow sensors are attractive candidates due to the ease of fabrication, lack of moving parts and higher sensitivity. Recently, a number of thermal flow sensor prototypes have been reported in the literature demonstrating the measurement of fluid flows under hostile conditions. This paper summarizes the concept of thermal flow sensing, operational modes and transduction mechanisms. Then, the choice of materials and their corresponding properties are presented in details. The paper also reports recent progress in the development of thermal flow sensors for harsh environment. In addition, the issues and considerations in packaging are reviewed. Finally, we conclude the review with the future prospects.

Fabrication and Multiphysics Modeling of MEMS Thermal Flow Sensor

2019 ◽  
Author(s):  
Justin Cable ◽  
Kevin R. Anderson
Keyword(s):  
Microelectromechanical Systems ◽  
Flow Direction ◽  
Flow Sensor ◽  
Constant Current ◽  
Thermal Flow ◽  
Maximum Heat ◽  
Flow Rates ◽  
Maximum Heat Transfer ◽  
Thermal Flow Sensor ◽  
Hot Film

Abstract A micromachined thermal flow sensor is presented demonstrating sensing liquid flow rates as low as 2 microliters per minute capable of being used for biomedical applications. These flow sensors rely on the varying electrical resistance of sensors generated by forced convection at different flow rates. The sensor array presented was constructed using microelectromechanical systems (MEMS) techniques including micro-molding, wet etching and dry etching utilizing biocompatible materials. A numerical model was built using COMSOL multi-physics in order to predict and optimize the electrical, thermal and fluid behavior of the sensor, which was verified with experimental data. The construction allowed for multiple thermal flow sensing operational modes. Here, constant current hot film and constant current calorimetric were simulated and tested. A variety of flow sensor geometries were compared to investigate maximum heat transfer to the sensors, thermal insultation, size, sensitivity and range capabilities. The sensor design is such that it is capable of detecting different flow direction and various flow ranges for different fluids. In addition to the performance capabilities outlined, the sensor is relatively inexpensive and should have a long lifetime due to the lack of moving parts.

Heat Transfer to Two-Phase: Air, Viscoelastic Fluid Flows Over a Hot Cylinder

2002 ◽  
Author(s):  
B. K. Rao
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Viscoelastic Fluid ◽  
Cross Flow ◽  
Fluid Flows ◽  
Horizontal Cylinder ◽  
Two Phase ◽  
Flow Rates ◽  
Heated Cylinder ◽  
Aqueous Polymer

Over a range of 70 < Rea < 9600, 7 < Pra < 130, 0 < ∃ < 0.12 and 0.7 < n < 1, circumferential wall temperatures for air-water and air-aqueous polymer (viscoelastic) solution flows over a horizontal cylinder were measured experimentally. The 2.5-cm-diameter and 7.5-cm-length cylinder was heated by passing direct electric current through it. The peripherally averaged heat transfer coefficient for relatively dilute viscoelastic-air solutions, at any fixed flow rate of liquid phase, increases with ∃. Such increase is more pronounced at lower flow rates of liquid phase. For relatively more elastic solutions, the two-phase heat transfer decreases with increasing ∃. Such reduction is more pronounced at higher flow rates of liquid phase. A new correlation is proposed for predicting the Nusselt number for air-viscoelastic fluid flows over a heated cylinder in cross flow.

Boiling-Curve Measurements From a Controlled Heat-Transfer Process

1971 ◽  
Vol 93 (4) ◽  
pp. 408-412 ◽  
Author(s):  
W. C. Peterson ◽  
M. G. Zaalouk
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Boiling Heat Transfer ◽  
Saturation Temperature ◽  
Heat Transfer Process ◽  
Stable Operation ◽  
Heater Surface ◽  
Transfer Processes ◽  
New Information ◽  
A New Technique

Feedback has been introduced around a boiling heat-transfer process in such a way that stable operation of the process has been obtained in all boiling regions including the transition region, in which, as is well known, the process itself is unstable. This system makes it possible to obtain much new information concerning both the steady-state and dynamic characteristics of boiling heat-transfer processes. Pool-boiling data which were obtained by the use of this system are presented. Accurate measurements of heater voltage and current were obtained by a new technique involving the use of digital instruments. These data are presented in the form of plotted experimental points in the nucleate, transition, and film boiling regions. The new measurement technique is described. Values of n in the equation q/As = CTdn are determined for all three boiling regions, where q = Btu/hr, As is heater surface area, and Td is temperature difference between heater surface and ambient liquid. The ambient liquid is distilled water maintained at saturation temperature under atmospheric pressure.

Fouling of Heat Transfer Surfaces by Solutions of Egg Albumin

1978 ◽  
Vol 41 (3) ◽  
pp. 187-194 ◽  
Author(s):  
A. C. LING ◽  
D. B. LUND
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Fluid Flow ◽  
Steel Surface ◽  
Biological Fluids ◽  
Heating Surface ◽  
Heat Transfer Process ◽  
Protein Solutions ◽  
Stainless Steel Surface ◽  
Egg Albumin

A major problem which can be encountered when biological fluids are heated is the deposition of components from the fluid on the heating surface. This results in loss of efficiency in the heat transfer process and usually contributes to requirements for more severe cleaning regimes to return the surface to the original clean condition. Since proteins have been implicated as a major source of the problem in heat exchanger fouling, we studied the effect of process and fluid variables on deposition from protein solutions. An electrically heated stainless steel surface was exposed to egg albumin solutions flowing at a variety of temperatures, fluid flow rates, and concentrations. The system for studying the rate of burn-on is unique and has been described elsewhere. The surface temperatures of the stainless steel surface could be monitored and controlled to any desired temperature. Results of the study indicated: (a) fouling rate increased with an increase in protein concentration, (b) increasing the fluid flow rate did not have a significant effect on rate of fouling, (c) increasing the temperature difference increased fouling rate, and (d) surface finish did not influence fouling.

Nonlinear Aspects of High Heat Flux Nucleate Boiling Heat Transfer

1995 ◽  
Vol 117 (4) ◽  
pp. 981-989 ◽  
Author(s):  
P. Sadasivan ◽  
C. Unal ◽  
R. Nelson
Keyword(s):  
Heat Transfer ◽  
Chaotic Behavior ◽  
Period Doubling ◽  
Thermal Conditions ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Transfer Process ◽  
High Heat Flux ◽  
Heater Surface ◽  
Nucleation Sites

This paper deals with potential nonlinear effects in nucleate boiling systems as a result of the behavior of individual nucleation sites on the heater surface. This requires detailed microscopic modeling of the surface. A computational model has been formulated for this purpose. The model addresses the three-dimensional transient conduction heat transfer process within the problem domain comprised of the macrolayer and heater. Hydrodynamic effects are represented through boundary conditions. Individual nucleation sites are activated or deactivated depending on the thermal conditions that prevail at the site. The model has been used to examine the behavior of sites on a realistic heater surface. The results indicate that significant spatial and temporal temperature variations can occur on the surface, and that thermal interactions among sites can result in some sites operating intermittently. Surface-averaged temperatures show nonlinear period-doubling behavior. A chaotic case was found. Qualitative comparisons are made to both local instantaneous temperature measurements and recent experiments that showed chaotic behavior. We believe that such nonlinear behavior is one of the reasons that mechanistic predictive capabilities for the boiling process have remained elusive.

Heat transfer analysis around thermal flow sensor for liquid

2017 ◽  
Vol 2017.8 (0) ◽  
pp. PN-11
Author(s):  
Junya HARA ◽  
Ken YAMAMOTO ◽  
Shinichi IKE ◽  
Seishi NAKANO ◽  
Masahiro MOTOSUKE
Keyword(s):  
Heat Transfer ◽  
Flow Sensor ◽  
Heat Transfer Analysis ◽  
Thermal Flow ◽  
Thermal Flow Sensor

Variation of Superheat With Subcooling in Nucleate Pool Boiling

1991 ◽  
Vol 113 (1) ◽  
pp. 201-208 ◽  
Author(s):  
R. L. Judd ◽  
H. Merte ◽  
M. E. Ulucakli
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Heat Removal ◽  
Nucleate Boiling ◽  
Constant Heat Flux ◽  
Heat Transfer Process ◽  
Heater Surface ◽  
Nucleate Boiling Heat Transfer ◽  
Microlayer Evaporation

An analysis is presented that explains the variation of superheat with subcooling that has been observed by a number of researchers investigating nucleate boiling heat transfer at constant heat flux. It is shown that superheat initially increases with increasing subcooling near saturated conditions because of the way in which changes in active site density and average bubble frequency with increasing subcooling affect the rate of heat removal from the heater surface by enthalpy transport and microlayer evaporation. As subcooling increases further, natural convection begins to play an increasingly important role in the heat transfer process. Ultimately, natural convection is able to accommodate the entire imposed heat flux, after which superheat decreases as subcooling increases. The success of the analysis in explaining the variation of superheat with subcooling suggests that the rate of the heat removal from the heater surface is completely determined by the mechanisms of enthalpy transport, natural convection, and microlayer evaporation.

scholarly journals Boiling of a refrigerant of low GWP on the surface with copper microchannels

2018 ◽  
Vol 70 ◽  
pp. 02007
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Atmospheric Pressure ◽  
Rectangular Cross Section ◽  
Heating Surface ◽  
Heat Transfer Process ◽  
Geometrical Parameters ◽  
Variable Depth ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The boiling curves and heat transfer coefficients between the heating surface and fluid were investigated in the paper. Copper samples with horizontal microchannels of rectangular cross-section, variable depth and width were the objects of the study. The following geometrical parameters have been used: microchannel width 0.2; 0.3 and 0.4 mm, depth between 0.2 and 0.5 mm (change every 0.1 mm). Boiling refrigerant was Novec-649 (GWP = 1), and the experiment was performed at atmospheric pressure. Geometrical parameters impact, within a given range of heat flux 3 – 130 kW/m2, on the heat transfer process was determined.

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