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Questions and Answers
What is the ultimate strength drop percentage of unalloyed steel as steam temperature raises from 300 to 400 оC?
What is the ultimate strength drop percentage of unalloyed steel as steam temperature raises from 300 to 400 оC?
What is the recent practice limit for steam temperature?
What is the recent practice limit for steam temperature?
In a closed feed water heater, where does the feed water pass through?
In a closed feed water heater, where does the feed water pass through?
What type of heater is known to need only a single pump regardless of the number of heaters?
What type of heater is known to need only a single pump regardless of the number of heaters?
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Which gases, when dissolved in water, make it corrosive and reactive with metals?
Which gases, when dissolved in water, make it corrosive and reactive with metals?
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Which process is commonly used in the liquefaction of coal?
Which process is commonly used in the liquefaction of coal?
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What is defined as a suspension of finely divided fluid in another?
What is defined as a suspension of finely divided fluid in another?
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What is the lowest grade of coal?
What is the lowest grade of coal?
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What is the primary issue faced by heat pumps?
What is the primary issue faced by heat pumps?
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Which refrigerant is predominantly used in commercial refrigeration systems?
Which refrigerant is predominantly used in commercial refrigeration systems?
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Cascade refrigeration systems are configured in which manner?
Cascade refrigeration systems are configured in which manner?
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What is typically the coefficient of performance (COP) of an actual absorption refrigeration system?
What is typically the coefficient of performance (COP) of an actual absorption refrigeration system?
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Where is the sight glass commonly located in a refrigeration system?
Where is the sight glass commonly located in a refrigeration system?
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Which material should methyl chloride not come into contact with?
Which material should methyl chloride not come into contact with?
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What is the required clearance above the floor for refrigerant piping crossing an open space?
What is the required clearance above the floor for refrigerant piping crossing an open space?
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What is the acceptable percentage distortion limit for seats and discs over five years?
What is the acceptable percentage distortion limit for seats and discs over five years?
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Which mechanism is used to reduce steam temperature by spraying low temperature water from boiler drum?
Which mechanism is used to reduce steam temperature by spraying low temperature water from boiler drum?
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Which process is employed to remove carbon dioxide from water?
Which process is employed to remove carbon dioxide from water?
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What substance is commonly used to absorb silica from water?
What substance is commonly used to absorb silica from water?
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What effect do excess hydrogen ions have on water quality?
What effect do excess hydrogen ions have on water quality?
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How does temperature affect the pH of water?
How does temperature affect the pH of water?
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What is the typical pH level maintained for boiler water to minimize corrosion?
What is the typical pH level maintained for boiler water to minimize corrosion?
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Which type of turbine operates efficiently for heads up to 300 meters?
Which type of turbine operates efficiently for heads up to 300 meters?
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What is the primary function of a barometric condenser in steam systems?
What is the primary function of a barometric condenser in steam systems?
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Which characteristic is not a physical property of water?
Which characteristic is not a physical property of water?
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What type of dam is most suitable for construction on weak foundation soils?
What type of dam is most suitable for construction on weak foundation soils?
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What term describes the volume of water that drains freely from an aquifer?
What term describes the volume of water that drains freely from an aquifer?
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Which term represents the line defined by the water level in multiple artesian wells?
Which term represents the line defined by the water level in multiple artesian wells?
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Which of the following is a positive sign of river pollution?
Which of the following is a positive sign of river pollution?
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What instrument is utilized for continuous measurement of atmospheric humidity?
What instrument is utilized for continuous measurement of atmospheric humidity?
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What energy transfer mode occurs between a solid surface and a moving liquid or gas, combining conduction and fluid motion?
What energy transfer mode occurs between a solid surface and a moving liquid or gas, combining conduction and fluid motion?
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During the simple heating and cooling process, how is the humidity ratio affected?
During the simple heating and cooling process, how is the humidity ratio affected?
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What effect does superheating the refrigerant in a vapor compression cycle without useful cooling have on the COP?
What effect does superheating the refrigerant in a vapor compression cycle without useful cooling have on the COP?
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When the refrigerant is sub-cooled at the condenser exit in a vapor compression cycle, what happens to the refrigerating effect?
When the refrigerant is sub-cooled at the condenser exit in a vapor compression cycle, what happens to the refrigerating effect?
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In a vapor compression cycle, increasing the condenser pressure affects which aspect?
In a vapor compression cycle, increasing the condenser pressure affects which aspect?
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What happens to the mass flow rate when there is an increase in the pressure drop in the condenser?
What happens to the mass flow rate when there is an increase in the pressure drop in the condenser?
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If the vaporizing temperature in a vapor compression cycle is increased, which of the following will improve?
If the vaporizing temperature in a vapor compression cycle is increased, which of the following will improve?
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When the pressure drop in the evaporator increases, what is the effect on the refrigerating effect?
When the pressure drop in the evaporator increases, what is the effect on the refrigerating effect?
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Which component's power output is least affected by an increase in pressure drop within the condenser?
Which component's power output is least affected by an increase in pressure drop within the condenser?
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What happens to the moisture content after expansion when the condenser pressure in a vapor compression cycle increases?
What happens to the moisture content after expansion when the condenser pressure in a vapor compression cycle increases?
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Study Notes
Refrigeration Systems
- Frosting is a major problem in heat pumps.
- R-502 is the dominant refrigerant used in commercial refrigeration systems.
- Cascade refrigeration systems are connected in series.
- A regenerator is used to preheat the solution partially before it enters the generator in absorption refrigeration systems.
- The COP of actual absorption refrigeration systems is typically less than 1.
- A sight glass is often located on the liquid line.
- Electronic detectors are used to detect vibrations in the current caused by the ionization of decomposed refrigerant between two oppositely-charged platinum electrodes.
- Miscibility refers to the ability of oil to mix with refrigerants.
- Joints and refrigerant-containing parts located in air ducts carrying conditioned air must withstand a temperature of 70°F without leaking into the airstream.
- Refrigerant piping crossing open spaces in buildings must be at least 2.2 meters above the floor unless it's located against the ceiling and permitted by the authority.
- Methyl chloride should not be in contact with any material that can cause corrosion or decomposition.
- Magnesium should not be in contact with halogenated refrigerants.
- Aluminum and its alloys are suitable for use in ammonia systems.
- If a pressure-relief device is used to protect a pressure vessel with an inside dimension of 6 inches or less, the ultimate strength of the vessel must be at least three times the design pressure.
- Seats and discs in pressure-relief devices should be limited in distortion to a set pressure change of not more than 5% over five years.
- Liquid receivers, if used, should not occupy more than 95% of their volume when the refrigerant temperature is 90°F.
- The discharge line should be vented to the atmosphere through a diffuser fitted to its upper extremity.
Thermal Power Plants
- Thermal power plants convert fossil fuels into shaft work.
- The ultimate strength of unalloyed steel drops by 30% as steam temperature rises from 300 to 400°C.
- Current practice limits steam temperature to 438°C.
- In a closed feed water heater, the feed water passes through the inside of the tube.
- A drain cooler is used if extracted steam, upon condensation, gets subcooled.
- Closed heaters only need a single pump, regardless of the number of heaters.
- Open heaters are also known as deaerators.
- Dissolved gases like O2 and CO2 make water corrosive, reacting with metal to form iron oxide.
- Cogeneration cycles are typically used in paper mills, textile mills, chemical factories, sugar factories, and rice mills.
- Tranquil flow must always occur above the critical depth.
- Passout turbines are employed when steam is continuously extracted for process heating.
- Binary cycle power generation uses combinations of fluids with different properties, such as mercury and water, for high-temperature applications.
- The critical temperature of mercury is 1460°C.
- The critical pressure of mercury is 108 MPa.
- Magnetohydrodynamic (MHD) technology converts heat directly to electricity using magnetism.
- Zinc telluride is NOT a material used for thermoelectric elements.
Coal and Biomass
- Graphite is a type of coal formed after anthracite.
- Peat is the lowest grade of coal.
- Volatile matter helps in the ignition of coal.
- Combustion ratio is the ratio of fixed carbon to volatile matter.
- An emulsion is a suspension of a finely divided fluid in another fluid.
- Gasohol contains 90% gasoline and 10% ethanol.
- The Fisher-Tropsch process is commercially used in coal liquefaction.
- Biomass is organic matter produced by plants in both land and water.
Thermal Power Plant Components
- In thermal power plants, induced draft fans are located at the foot of the stack.
- Forced draft fans are installed at the inlet of the preheater.
- Once-through boilers known as drumless boilers.
- Desuperheaters reduce steam temperature by spraying low-temperature water from the boiler drum.
Water Treatment
- Aeration can remove carbon dioxide from water.
- Magnesium hydroxide is often used to absorb silica from water.
- Excess hydrogen ions make water acidic.
- The pH of water varies with its temperature.
- A pH of 9.5 is typically maintained for boiler water to minimize corrosion.
Hydroelectric Power
- Francis turbines have a degree of reaction of 1/2.
- Barometric condensers use a series of baffles to expose a large surface area for steam fed from below to come in direct contact with cooling water.
- A hydrograph shows the variation of river flow (discharge) with time.
- A flume is an open channel erected on a surface above the ground.
- Deriaz turbines are used for heads up to 300 meters and have diagonal flow.
Diesel Engines
- Oil is atomized by air blast or pressure jet at about 70 bar for injection into diesel engines.
- Common rail injection is a type of solid injection where a single pump supplies fuel under high pressure to a fuel header.
- Thermosiphon cooling in diesel engines is driven by density differential.
- Dry sump lubrication systems use a separate storage tank outside the engine cylinder for oil storage and are used in high-capacity engines.
- Detonation produces extreme pressure differentials and violent gas vibrations.
- In spark ignition engines, detonation occurs near the end of combustion.
- In compression ignition engines, detonation occurs near the beginning of combustion.
- Morse tests are used to measure the indicated power of multi-cylinder engines.
- Ethyl nitrate is added to minimize ignition delay and decrease engine knocking.
Fluid Mechanics
- The center of pressure is the point on a submerged plane surface where the resultant force acts.
- Pascal's Law states that the pressure at any point in a fluid at rest is the same in all directions.
Water Resources
- Hardness is not a physical characteristic of water.
- Buttress dams are best suited for weak foundations.
- Specific yield is the volume of water that will drain freely from an aquifer.
- The peizometric surface is a line defined by the water level in a group of artesian wells.
- Chloride content is a positive indication of pollution in a river.
- A hygrograph is used to measure atmospheric humidity continuously.
Fluid Mechanics
- Entrance losses, losses through elbows, fittings, and valves are generally expressed as functions of kinetic energy.
- Dry air contains no water vapor.
- On a psychrometric chart, constant-enthalpy lines coincide with constant-temperature lines at temperatures below 50°C.
- The amount of moisture in the air depends on its temperature.
- The deep body temperature of a healthy person is maintained at 37°C.
- Air motion plays an important role in human comfort.
- During simple heating and cooling processes, humidity ratio decreases.
- The condensive cooling process follows a line of constant wet-bulb temperature on the psychrometric chart.
- A superheated vapor is a vapor that is not about to condense.
- Sublimation is the process of passing from the solid phase directly into the vapor phase.
- Robert Boyle observed that the pressure of gases is inversely proportional to their volume.
Thermodynamics
- Heat is energy in transition.
- Convection is a mode of energy transfer between a solid surface and an adjacent liquid or gas in motion. It involves combined effects of conduction and fluid motion.
- Radiation is usually considered a surface phenomenon.
- Work is an energy interaction between a system and its surroundings.
- Dynamic equilibrium describes a process where the system remains in equilibrium at all times.
Vapor Compression Cycle
- Superheating the refrigerant in a vapor compression cycle without useful cooling decreases the COP and increases compressor power.
- Sub-cooling the refrigerant at the condenser exit increases the refrigerating effect and decreases the mass flow rate.
- Increasing the vaporizing temperature increases the COP but decreases the temperature difference between the evaporator and compressor.
- Increasing the condenser pressure increases compressor power and decreases the moisture content after expansion.
- Increasing the pressure drop in the condenser increases the heat rejected and decreases the mass flow rate.
- Increasing the pressure drop in the evaporator increases the refrigerating effect.
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Description
This quiz covers essential concepts related to refrigeration systems, including types of refrigerants, their applications, and operational principles like COP and miscibility. Test your knowledge on system components such as sight glasses, joints, and the role of regenerators in absorption refrigeration.
