View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge. Photoshoped pics are developed. Some pics and GIF from Google. Videos from YouTube ( Engineering Sights ).
Get link
Facebook
Twitter
Pinterest
Email
Other Apps
Boiler Feed Water Treatment
Get link
Facebook
Twitter
Pinterest
Email
Other Apps
-
Boiler Feed Water
Natural water usually contains solid, liquid and gaseous impurities. It cannot be used for Power Generation.
Makeup Water is needed ↠ to replace the losses due to Blow Down and Leakages in the cycle.
Salt of Calcium and Magnesium is harmful because when heated, it precipitates as solid residue.
If 1 litre water is added in boiler ↠ 1 - 2 % of water waste as evaporation losses.
Classification of Impurities in Water
Impurities in water are classified into the following types:
A. Visible Impurity
Microbiological Growth ↠ presence of micro-organisms which produce clogging.
Turbidity and Sediments ↠ Turbidity (suspended insoluble matter) and sediments (coarse particles which settle down in stationary water).
B. Dissolved Gases
Carbon dioxide
Oxygen
Nitrogen
Methane
Hydrogen Sulphide
C. Mineral and Salts
Iron and Magnesium
Sodium and Potassium Salts
Flourides
Silica
D. Mineral Acids
Presence of undesirable (reaction with the boiler material).
E. Hardness
Salts of calcium and magnesium (carbonate, chloride, sulphate) are responsible for hardness (which can resist heat transfer and clogs the passage in pipes).
Increase particle size from sub-microscopic micro-floc to visible suspended particles.
Micro-flocs ↣ brought in contact with each other by slow mixing.
Once floc reached its optimum size and strength ↣ ready for sedimentation.
Sedimentation ↣ water is allowed to stand at stand-still in big tanks so solid matters settle down and clean water is drained out.
Filtration ↣ raw water is passed through number of membrane (micro-filtration, ultra-filtration, nano-filtration, reverse osmosis) to remove all impurities to get permeate.
It is defined as, "dissolved calcium and magnesium hardness removal process using solid material of sandy texture (resin or formally called as Zeolite)".
Raw water ↣ pass through cation and anion exchanger to remove cations and anions ↣ clean (or soft) water.
For anion bed ↣ Alkaline solution.
For Cation bed ↣ Acidic solution.
Regeneration of Zeolite:
Back-washing of Bed ↣ pump to regulate water from cation to anion exchanger tank in reverse direction with soda ash.
Hydrographic Survey Hydrography is the science which determines the physical features and the navigable portions of the Earth's surface adjoining coastal areas. Surveyors study bodies of water to see what the floor looks like. Techniques and Instruments used in Hydrographic Survey : Many instruments are used in hydrographic survey like multibeam sonars, LIDAR, multibeam echo sounders(MBES), global positioning system (GPS), laser scanners etc. Among these instruments some are discussed ahead which are mostly used. 1. Light Detection and Ranging: LIDAR is used to measure the elevation or the depths of water bodies by analyzing the reflection of laser light off an object or seafloor. Bathymetric LIDAR is used to determine is used to determine the depths of water bodies by measuring the time delay between the pulse of transmission and its return signals. 2.Multibeam Sonars: Multibeam echo sounders(MBES) or sonar systems transmit sound energy which strike seafloor a
TAPING CORRECTIONS There are two types of corrections depending upon the type of errors in tape due to the different conditions. 1. Systematic Errors : Slope Erroneous tape length Temperature Tension Sag 2. Random Errors : Slope Alignment Marking & Plumbing Temperature Tension & Sag 1. Temperature Correction It is necessary to apply this correction, since the length of a tape is increased as its temperature is raised, and consequently, the measured distance is too small. It is given by the formula, C t = 𝛼 (T m – T o )L Where, C t = the correction for temperature, in m. 𝛼 = the coefficient of thermal expansion. T m = the mean temperature during measurement. T o = the temperature at which the tape is standardized. L = the measure length in m. For Foot Unit : C t = 6.45×10^-6 (T m – 68 )L For Metric Unit : C t = 1.16
Rankine Cycle Rankine cycle is an ideal cycle for Vapour Power Cycles and is normally used for Electricity Generation. The Rankine cycle consist of following steps: 1 ↝ 2 : Isentropic Compression in Pump. 2 ↝ 3 : Constant Pressure Heat Addition in Boiler. 3 ↝ 4 : IsentropicExpansion in Turbine. 4 ↝ 1 : Constant Pressure Heat Rejection in Condenser. Energy Balance: Since, all the devices which Rankine Cycle posses are steady flow devices, so the energy balance for Rankine cycle is: 》For Pump ( q = 0 ): 》For Boiler ( w = 0 ): 》For Turbine ( q = 0 ): 》For condenser ( w = 0 ): The thermal efficiency of Rankine Cycle is: How can we Increase the Efficiency of A Rankine Cycle: The efficiency of a Rankine cycle can be increased: Increasing the avg. temperate at which heat is added Decreasing the avg. Temperature at which heat is rejected. The above two objectives can be achieved by following three methods: 1. By
Comments
Post a Comment
HI, we wI'll contact you later