In this article we will discuss about the meaning and process of mass transfer. Meaning of Mass Transfer: When a system contains two or more components whose concentrations vary from point to point, there is a natural tendency for mass to be transferred, minimising the concentration differences within the system. The transport of one constituent from a region of higher [...]
In this article we will discuss about the Fick’s law of diffusion. Consider a chamber in which two different gas species, B and C, at the same temperature and pressure are initially separated by a partition. The left compartment has a high concentration of gas B (dark circles) whereas the right compartment is rich in gas C (white circles). Higher [...]
Consider evaporation of water contained in a tube or tank and its subsequent diffusion through the stagnant layer of air over it. Assumptions: (i) The system is under steady state and isothermal conditions (ii) The total pressure within the tube is constant and equal to the outside pressure (iii) Both air and water vapours behave as perfect gases (iv) Air [...]
In this article we will discuss about the general equation for mass transfer. Also learn about equimolal diffusion. General Equation of Mass Diffusion: Consider mass balance of species B diffusing through a control volume (dx × dy × dz) in a solid or stationary fluid medium C. Accumulation of mass of species B in the elemental volume due to its [...]
When a fluid flows around an object or when the object moves through a body of fluid, there exists a thin layer of fluid close to the solid surface within which shear stresses significantly influence the velocity distribution. The fluid velocity varies from zero at the solid surface to the velocity of free stream flow at a certain distance away [...]
In this article we will discuss about:- 1. Introduction on Halogen Lamp 2. Principle of Operation of Halogen Lamp 3. Safety 4. Handling Precautions. Introduction on Halogen Lamp: A halogen lamp (also called tungsten-halogen lamp or quartz halogen lamp) is an incandescent lamp wherein a tungsten filament is sealed into a small transparent envelope filled with a halogen gas such [...]
Learn about the comparison between filament lamps and fluorescent lamps. Comparison # Filament Lamp: 1. Simple, reliable and cheap. 2. Average life 1000 hrs. 3. Reddish Light. 4. Life is not affected by frequent switching. 5. No stroboscopic effect. 6. Voltage variations, which vary with the wattage, affect the temperature, efficiency and also the life. 7. Brightness is very high [...]
The following points highlight the four main factors to be considered while selecting lamps. The factors are: 1. Fitting Required for Filament Lamp 2. Lamp Connection Caps 3. Reflectors 4. Diffusers. Factor # 1. Fitting Required for Filament Lamp: Light fitting should be made of cold rolled annealed steel sheets duly oiled and picked against rust. Fitting for outdoor use [...]
A number of methods have been employed for lighting calculations, among which may be mentioned as: 1. Watts for Square Meter Method 2. Lumen or Light Flux Method 3. Point to Point or Inverse-Square Law Method. 1. Watts for Square Meter Method: This is principally a "rule of thumb" method, very handy for rough calculation or checking. It consists in [...]
In this article we will discuss about the nature of light. Lighting is one of the major uses of electrical energy. Sun is the biggest source of natural light. Artificial lighting may be electrical or non-electrical. Where there is no natural light, use of artificial light is made. Artificial lighting produced electrically has advantages like cleanliness, ease of control, reliability, [...]