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 ).
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Boiler Safety and Test
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Boiler Hydro Test
Boiler hydro test is used to ensure all the welding joints, pipe bents and all headers are water leak proof.
It is done at pressure of 1.5 times of design pressure.
E.g.: If design pressure of boiler is 50 bar, then the hydraulic test pressure will be 75 bar.
Pre-Checklist Hydro Test
Following are the pre-checklist for the hydro test of Boiler:
All erection work should be completed.
Confirm that no foreign material left in the boiler.
Confirm the drum manhole is closed with proper gasket.
Confirm all the drain system ready for operation.
All safety valve should be gagged.
The range of the pressure should be 2 times of the maximum test pressure but not less than test pressure.
The pressure gage should be pre-calibrated before test.
The test pump should have capacity of more than test pressure.
Minimum quantity of demineralized water should be available equivalent to the boiler capacity.
Ensure condensate and Feedwater chemistry parameters to strictly adhere to the required standard.
PH value should be in range of 8 - 9.
The water temperature should not less than 21.1 ℃.
Isolate all pressure and temperature gages except some pressure gages for hydraulic pressure measurements.
Start the boiler filling with the filling pump through the drain header (or filling time).
Close all vents sequentially after water coming from the vents.
Start the hydro test pump ensure all vents closed and rise pressure gradually to the design pressure and then the pressure to be raised up to the test pressure. E.g.: Design pressure = 200 bar, Test pressure = 300 bar).
Hold the pressure raising at 50 bar and 100 bar to check any valve passing and inspect leakage in pressure parts.
Once the pressure reached to the test pressure stop pressurizing and observe pressure drop if the pressure drop is very less then the test is successful.
If any defect is found, type of defect should be solved.
If the pressure is holding better then the pressurizes at 50 bar by opening top vents.
After this, checking team is ready is to inspect inside boiler physically.
After safety test, documents to be prepared and signed with the concerned authorities.
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
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