Modeling of High-Current Arcs with Emphasis on Free Surface
... the interfacial regions. Indeed, in virtually all previously published papers concerning weld pool behavior, this interfacial region was introduced in terms of the boundary conditions, with a Gaussiantype current and heat flux distribution being specified. By the same token, in previous studies of w ...
... the interfacial regions. Indeed, in virtually all previously published papers concerning weld pool behavior, this interfacial region was introduced in terms of the boundary conditions, with a Gaussiantype current and heat flux distribution being specified. By the same token, in previous studies of w ...
Chapter 4 - McGraw Hill Higher Education
... Consider a system undergoing a series of adiabatic processes from a specified state 1 to another specified state 2. Being adiabatic, these processes obviously cannot involve any heat transfer, but they may involve several kinds of work interactions. Careful measurements during these experiments indi ...
... Consider a system undergoing a series of adiabatic processes from a specified state 1 to another specified state 2. Being adiabatic, these processes obviously cannot involve any heat transfer, but they may involve several kinds of work interactions. Careful measurements during these experiments indi ...
Distribution and prediction of solute in Al–Zn–Mg alloys
... the amount of Mg increases, the agreement is getting poor. This can be explained because the mathematical model employed for predictions considered the growth kinetics of a dendrite at low velocity [7,8] to describe the growth of a dendrite grain. The difference between previous models [16,17] is th ...
... the amount of Mg increases, the agreement is getting poor. This can be explained because the mathematical model employed for predictions considered the growth kinetics of a dendrite at low velocity [7,8] to describe the growth of a dendrite grain. The difference between previous models [16,17] is th ...
PrOBLEMS_PACK
... superheated by 7.4 °C. The stream now loses its heat to the surrounding and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at 200 °C. Calculate the final pressure and quality, as well ...
... superheated by 7.4 °C. The stream now loses its heat to the surrounding and the piston moves down, hitting a set of stops at which point the cylinder contains saturated liquid water. The cooling continues until the cylinder contains water at 200 °C. Calculate the final pressure and quality, as well ...
Thermo fundamentals
... Therefore, it is required to have more accurate predictions for a substance, over a larger region and without limitations. Several equations are proposed by various scientists and researchers. 1. Van der Waal’s Equation of State : ...
... Therefore, it is required to have more accurate predictions for a substance, over a larger region and without limitations. Several equations are proposed by various scientists and researchers. 1. Van der Waal’s Equation of State : ...
Chapter 5
... It should always be kept in mind that there is no such thing as a “conservation of volume” principle. Therefore, the volume flow rates into and out of a steady-flow device may be different. The volume flow rate at the outlet of an air compressor is much less than that at the inlet even though the ma ...
... It should always be kept in mind that there is no such thing as a “conservation of volume” principle. Therefore, the volume flow rates into and out of a steady-flow device may be different. The volume flow rate at the outlet of an air compressor is much less than that at the inlet even though the ma ...
ENGINEERING_THERMODYNAMICS
... When two systems are separately in thermal equilibrium with a third system then they themselves is in thermal equilibrium with each other. 20. What are the limitations of first law of thermodynamics? 1. According to first law of thermodynamics heat and work are mutually convertible during any cycle ...
... When two systems are separately in thermal equilibrium with a third system then they themselves is in thermal equilibrium with each other. 20. What are the limitations of first law of thermodynamics? 1. According to first law of thermodynamics heat and work are mutually convertible during any cycle ...
Countercurrent exchange
Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some component, between two flowing bodies flowing in opposite directions to each other. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. For example, in a distillation column, the vapors bubble up through the downward flowing liquid while exchanging both heat and mass.The maximum amount of heat or mass transfer that can be obtained is higher with countercurrent than co-current (parallel) exchange because countercurrent maintains a slowly declining difference or gradient (usually temperature or concentration difference). In cocurrent exchange the initial gradient is higher but falls off quickly, leading to wasted potential. For example, in the diagram at the right, the fluid being heated (exiting top) has a higher exiting temperature than the cooled fluid (exiting bottom) that was used for heating. With cocurrent or parallel exchange the heated and cooled fluids can only approach one another. The result is that countercurrent exchange can achieve a greater amount of heat or mass transfer than parallel under otherwise similar conditions. See: flow arrangement.Countercurrent exchange when set up in a circuit or loop can be used for building up concentrations, heat, or other properties of flowing liquids. Specifically when set up in a loop with a buffering liquid between the incoming and outgoing fluid running in a circuit, and with active transport pumps on the outgoing fluid's tubes, the system is called a Countercurrent multiplier, enabling a multiplied effect of many small pumps to gradually build up a large concentration in the buffer liquid.Other countercurrent exchange circuits where the incoming and outgoing fluids touch each other are used for retaining a high concentration of a dissolved substance or for retaining heat, or for allowing the external buildup of the heat or concentration at one point in the system.Countercurrent exchange circuits or loops are found extensively in nature, specifically in biologic systems. In vertebrates, they are called a Rete mirabile, originally the name of an organ in fish gills for absorbing oxygen from the water. It is mimicked in industrial systems. Countercurrent exchange is a key concept in chemical engineering thermodynamics and manufacturing processes, for example in extracting sucrose from sugar beet roots.Countercurrent multiplication is a similar but different concept where liquid moves in a loop followed by a long length of movement in opposite directions with an intermediate zone. The tube leading to the loop passively building up a gradient of heat (or cooling) or solvent concentration while the returning tube has a constant small pumping action all along it, so that a gradual intensification of the heat or concentration is created towards the loop. Countercurrent multiplication has been found in the kidneys as well as in many other biological organs.