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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Engine Cooling Systems
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Necessity Of Engine Cooling:
If there is no engine cooling system in a car, it might reaches higher temperature which can important components burn gasket, delivery lines.
If no engine cooling system, lubrication oil can change its composition.
High temperature attainment can reduce the strength of piston, cylinder lining, etc.
Engine cooling is required to keep the temperature low to increase volumetric efficiency, reduce engine failure.
Demerits Of Over-Cooling:
Disadvantages of over-cooling are:
Starting of engine becomes difficult.
Reduction in engine life.
Inadequate lubrication of engine.
Improper vaporization of fuel.
Demerits Of Under-Cooling:
Disadvantages of under-cooling are:
Reduction in life of piston and cylinders due to the attainment of high temperature.
Under cooled engine lead to pre-ignition of fuel in SI engines.
Composition of lube oil may change.
Effects of Operating Variables on Engine Heat Transfer:
Compression Ratio ↣ if compression ratio is greater than mean total volume of engine is increased which increase the compression and expansion. Due to greater expansion temperature of gas is reduced, thereby decrease in heat transfer happened.
F/A Ratio ↣ At 1.2 equivalence ratio, maximum gas temperature reaches and maximum heat rejection occurs.
Engine Load or Speed ↣ With the increase in engine speed, the temperature of engine increases which increase the heat rejection.
Ignition Timing ↣ When the spark advance is different from the optimum value, the heat rejected is increased.
Cooling Systems:
There are two types of Engine Cooling Systems which are given below:
Air Cooling System ↣ Used fins(on the outer surface of engine) on which air strikes and cooling happens.
Water/Liquid Cooling System ↣ Used liquid (mostly water) for cooling.
Water Cooling Systems are further divided into different types which are explained below:
1. Thermosyphon Cooling System:
Cooling is independent of engine speed.
The circulation of water starts only after the engine has become hot enough to cause thermosyphon effect.
Radiator should be above engine for flow of water to be cooled under force of gravity.
2. Forced or Pump Cooling System:
Water is continuously flow into engine by centrifugal pump operated by engine.
Thermostat is used to control water temperature.
If the temperature of water does not cross the pre-determine temperature of thermal expansion of thermostat, the water is continuously flowing through pump into engine.
If the temperature of water cross the pre-determine temperature of thermal expansion of thermostat, the water is cooled first by passing it through radiator and then flow into engine by means of pump.
3. Evaporative Cooling System:
Water from tank is flowed by pump into engine for cooling.
When water is heated, it is allowed to flow through pipe into radiator where vapors moves up and is cooled (condensed) by flowing water through jackets.
This system is only for stationary engines.
4. Pressurized Water Cooling System:
The rate of heat transfer depends upon the temperature difference between bodies, surface area and conductivity of materials.
To reduce the size of radiator, the cooling system is sealed from atmosphere and is kept under certain pressure.
In this case temperature of boiling water increases as the pressure on it is raised.
This allow the greater heat transfer due to greater temperature difference.
Main Components Of Water Cooling System:
Following are the main components of water cooling system:
1. If engine cooling system fails to operate, it will destroy you sensors, engine components, wiring which connects fuse, sensors and ECU can be damaged. Because if engine cooling system doesn't work, it will result in increase in temperature which can cause advance combustion which can damage our engine furthermore. 2. Engine Cylinders are cooled by flowing liquid ( normally water but in some cases oil ) through water jackets. Water Jackets are small hole on the engine block located near to engines cylinders for cooling.
Angles & Directions Angles are also called bearings. Bearings are the acute angles between lines and meridians. They are divided into following types. Related Terms : Meridian : Imaginary line joining North and South poles. Declination : Difference between magnetic and true meridians. Azimuth : Clockwise angle taken from Geodatic North. * If area is greater ➤ use Geodatic North * If area is smaller ➤ use Magnetic North Magnetic Declination maybe towards East or West. For east ➤ Magnetic bearing=true bearing - Declination For west ➤ Magnetic bearing=true bearing + Declination Forward Bearing : Bearing taken in the direction of traverse. Backward Bearing : Bearing taken in opposite direction of traverse. Forward bearing - Backward bearing=180 For anti-clockwise : FB of line = BB of previous line + angle Example: In an anti-clockwise traverse <A=102'30',...
Projection: The term Projection is defined as: Presentation of an image or an object on a surface. The principles used to graphically represent 3-D objects and structures on 2-D media and it based on two variables: Line of Sight. Plane of Projection. Line of Sight & Plane of Projection: Line of sight is divided into 2 types: Parallel Projection Converging Projection & A plane of projection is an imaginary flat plane upon which the image created by the lines of sight is projected. Orthographic Projection: When the projectors are parallel to each other and perpendicular to the plane of projection. The lines pf sight of the observer create a view on the screen. The screen is referred to as the Plane of Projection (POP). The lines of sight are called Projection lines or projectors. Rules of Orthographic Projection: Edges that are parallel to a plane of projection appear as lines. Edges that are incl...
Pressure: Pressure is defined as: ' Normal force per unit area of body'. There are different pressures which we described ahead: Atmospheric Pressure ⟺ Pressure exerted by atmosphere. Absolute Pressure ⟺ The actual pressure at a given point. It is calculated with respect to absolute zero pressure. Gage Pressure ⟺ It is difference between the absolute pressure and the local atmospheric pressure. Vacuum Pressure ⟺ Pressure below atmospheric pressure. Pressure At A Point In A Fluid: For the pressure at a point in fluid, consider a triangular area of fluid. Consider a free body diagram with in a fluid mass. The force and weight components along Z-axis is given by: So, pressure at a point of a fluid at rest or motion is independent of direction as long as there are no shearing stresses present. Types Of Forces: There are two types of forces which are described ahead: Body Forces ⟺...
1. What will happen when the engine cooling system fails to cool engine components which are to be cooled?
ReplyDelete2. How engine cylinders are cooled?
1. If engine cooling system fails to operate, it will destroy you sensors, engine components, wiring which connects fuse, sensors and ECU can be damaged. Because if engine cooling system doesn't work, it will result in increase in temperature which can cause advance combustion which can damage our engine furthermore.
ReplyDelete2. Engine Cylinders are cooled by flowing liquid ( normally water but in some cases oil ) through water jackets. Water Jackets are small hole on the engine block located near to engines cylinders for cooling.