78 Questions
What is the primary purpose of refrigeration and air-conditioning?
To control the environments of living and non-living subjects
Why is adaptation to unpredictable environmental variations not feasible for living and non-living beings?
It hinders efficiency and performance
What does refrigeration achieve in terms of temperature relative to its surroundings?
Maintains a temperature lower than its surroundings
Which important environment variables are mentioned in the text as constantly changing?
Temperature, humidity, pressure, and air motion
What does refrigeration achieve by extracting heat from the space under consideration?
Maintains a lower temperature than the surrounding atmosphere
Why is control of the environment essential for living and non-living beings?
To provide comforts for better performance and longevity
What was the working fluid used by Jacob Perkins in his hand-operated refrigeration system?
Ether
Who obtained the first American patent for a cold air machine to produce ice?
Dr. John Gorrie
In the 19th century, what was developed to replace natural ice?
Artificial ice producing machines
What was the purpose of the vapor-absorption refrigeration system developed by Ferdinand Carre?
To meet the demand for ice during the civil war
What was the heat source used to separate ammonia vapor in Ferdinand Carre's refrigeration system?
A burner
What was the world's first installation of a refrigeration machine used for brewery?
James Harrison's system
In which century were large-sized refrigeration machines developed?
20th century
Who developed the first two-stage modern compressor in 1915?
Dr. John Gorrie
What method was used to keep water outside homes overnight in ancient India and Egypt to produce ice?
Evaporation in cool, dry air with radiative heat transfer
Who is credited with obtaining the first British Patent for a refrigeration system in 1790?
Thomas Hariss and John Long
What is the precise meaning of air conditioning?
Controlling temperature, humidity, cleanliness, and air motion
Why is external power always required in air conditioning systems?
To pump out or in the heat
In the winter air conditioning system, what is added to the space being conditioned?
Extra moisture
What does comfort air conditioning primarily deal with?
Residential buildings and offices only
Which parameter is NOT considered essential for the comfort of human beings in air conditioning?
Air pressure
What role does a dehumidifier play in summer air conditioning?
Removing extra moisture from the space
Why is air motion considered essential for comfort in air conditioning?
To distribute conditioned air evenly
What distinguishes industrial air conditioning from comfort air conditioning?
Includes control of air pressure
What is the primary difference between summer and winter air conditioning systems?
Heating versus cooling the space
What happens to the humidity levels during rain in Delhi and Kolkata?
Humidity decreases in Delhi but increases in Kolkata.
What was the most important development in refrigeration systems after the 1920s?
Invention of new refrigerants like chlorfluor hydrocarbons
What was a major advantage of chlorfluor carbons as refrigerants compared to NH3 and SO2?
Non-toxicity
Which specialized field of refrigeration involves removing heat from substances in chemical, petroleum, and petrochemical plants?
Industrial refrigeration
What are some examples of applications of air conditioning mentioned in the text?
Treating air to control temperature, humidity, cleanliness, and distribution
Why is cooling required in buildings even in places where temperatures remain normal?
To remove heat generated internally by people and equipment
What is the main purpose of comfort air conditioning in residential and official buildings?
To maintain comfortable conditions for people
What role does air conditioning play in hospitals and medical buildings according to the text?
To maintain humidity levels and cleanliness
In what way does spot heating differ from spot cooling?
Spot heating is more practical in cold weather while spot cooling is more effective in hot weather.
What is the primary function of air conditioning in environmental laboratories?
To control humidity and cleanliness of air
What is the purpose of maintaining a high temperature and humidity in one laboratory?
To study the behavior of animals in tropical climates
In the printing industries, what problems arise if humidity is not properly maintained?
Curling or buckling of paper
Why are textiles sensitive to changes in humidity and temperature?
To prevent rust formation
How does air conditioning help in the manufacturing of precision metal parts?
Maintain uniform temperature to avoid expansion and contraction
What is a major contributor to the cooling load in vehicles like planes, trains, and ships?
Heat from solar radiation
What is the purpose of using a vapour compression cycle in air refrigeration systems?
To improve the efficiency of cooling systems
What is the standard unit of refrigeration used?
Ton refrigeration
Why do raw photographic materials deteriorate quickly in high humidity and temperatures?
Because of high humidity and temperatures
What is the role of air conditioning in computer rooms?
Control temperature, humidity, and cleanliness of the air
How does refrigeration help extend storage life for perishable food products?
By maintaining low temperatures above freezing point
What is the purpose of the expansion valve in a refrigeration system?
To allow the liquid refrigerant to pass at a controlled rate after reducing its pressure and temperature
What is the role of the condenser in a vapor compression refrigeration system?
To cool and condense the high pressure and temperature vapor refrigerant
At what stage of the theoretical vapor compression cycle does the liquid refrigerant evaporate in a refrigeration system?
Expansion process
What happens to the refrigerant in the condenser of a vapor compression refrigeration system?
It is cooled and condensed from a high pressure and temperature vapor to liquid
What is the function of the receiver in a vapor compression refrigeration system?
To store the condensed liquid refrigerant before supplying it to the evaporator
During which phase of the vapor compression cycle does no heat absorption or rejection occur by the liquid refrigerant?
Expansion process
What happens to the pressure of the vapor refrigerant during isentropic compression in a vapor compression cycle?
Pressure increases
How is the condensed liquid refrigerant supplied to the evaporator in a refrigeration system?
Through the receiver output valve
What happens to the medium when liquid-vapor refrigerant evaporates in an evaporator?
The medium absorbs heat from the evaporating refrigerant
Which part of a vapor compression cycle stores the high pressure and temperature vapor refrigerant before being condensed?
Receiver
What is one of the main benefits of superheating the suction vapour in refrigeration systems?
Ensures complete vaporization of the liquid in the evaporator
What role does superheating of the suction vapour play in modulating the capacity of the expansion valve?
Increases the capacity of the expansion valve
For which refrigerant is the maximum Coefficient of Performance (COP) obtained with superheating of the suction vapour?
Freon 12
What is the primary effect of superheating the suction vapour in refrigeration systems in terms of specific volume?
Increase in specific volume of suction vapour
Compared to the decrease in evaporator pressure, what is noted about the effect of an increase in condenser pressure on refrigerating capacity and power consumption?
It is less significant
What is the equation for the refrigerating effect (RE) during evaporation?
RE = h1 - hf3
What does the Coefficient of Performance (C.O.P.) represent in a refrigerating system?
Ratio of refrigerating effect to work done
How does a decrease in suction pressure impact the Coefficient of Performance (C.O.P.) of a refrigerating system?
Decreases the C.O.P.
What is the net effect of a decrease in suction pressure on the refrigerating capacity of a system?
Decreases refrigerating capacity
How does a decrease in evaporator pressure affect the reciprocating compressor's capacity?
Decreases compressor's capacity
What is the consequence of a decrease in evaporator temperature on a reciprocating compressor?
Decreases volumetric efficiency
How does an increase in condenser pressure affect refrigeration capacity?
Decreases refrigeration capacity
What happens to the Coefficient of Performance (C.O.P.) with decreasing evaporator pressure?
Decreases C.O.P.
What effect does increasing condenser pressure have on power consumption?
Increases specific work
What is the main reason for a decrease in refrigeration capacity due to an increase in condenser pressure?
Decrease in refrigerating effect
What is the primary purpose of refrigeration according to the text?
Cooling down a space where heat is unwanted
Why does the temperature inside a refrigerator decrease when food products are kept inside?
Unwanted heat from the food products is removed
In the context of refrigeration, why do air-conditioned cars have to reject heat to the surroundings?
To lower the temperature inside the car by removing heat
What is one of the main reasons for using refrigerators in homes and canteens?
To slow down bacterial growth in food products
Why is it necessary for a refrigerator to transfer unwanted heat from food products to the surrounding environment?
To maintain a lower temperature inside the refrigerator
What role does a heat pump play in maintaining comfortable temperatures in different seasons inside a car?
It rejects heat in hot seasons and absorbs heat in cold seasons
What distinguishes refrigeration from natural heat flow processes according to the text?
Heat flow in refrigeration is always from high to low temperatures
How does refrigeration influence the temperatures inside a car during summer?
By rejecting heat from inside, lowering internal temperature
Explore the fundamentals of refrigeration and its importance in adapting to varying environmental conditions. Learn about temperature, humidity, pressure, and air motion as crucial variables in maintaining a conducive physical environment.
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