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Refrigerator is an electronic device that dissipates heat from inside to the outer surroundings to keep the internal environment cool. A heat pump is the reverse of the refrigerator. Both are quite opposite to each other concerning cooling and heating effects. Refrigerator and heat pumps are used for various domestic and industrial purposes.
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Key Takeaways: refrigerator, heat pump, evaporation, condenser, evaporation coil, expansion valve, refrigerant, air handler, air output unit
Refrigerator
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In a refrigerator a coolant is present. It is made to take the heat out of the stored items into the outer surroundings to keep the stored items at low temperatures.
Refrigerator Mechanism
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Components of Refrigerator
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Generally, refrigerators consist of components like evaporation coil, expansion valve, compressor, condenser, and refrigerant.
Components of Refrigerator
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Working Principle of Refrigerator
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Refrigerator works on the second law of thermodynamics. It keeps the stored items cool in a recurring process called the vapour compression refrigeration cycle. It works in the following steps:
- The evaporation coils on the back of the refrigerator allow the hot refrigerant gas to dissipate its heat.
- The refrigerant gas after losing heat gets condensed into a liquid at high pressure.
- The high-pressure refrigerant liquid circulates through the expansion valve.
- The refrigerant liquid heats up, boils and vaporises.
Working of Refrigerator
- The temperature of the liquid falls to about -20°F.
- When the cold gas passes through the expansion coil, the inside temperature becomes cold by absorbing heat.
- Consequently, the low-pressure refrigerant gas is absorbed by the compressor.
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Heat Pump
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Heat pump is a system that is used to heat or cool an enclosed space by transferring heat energy from a cooler space to a warmer space through the refrigeration cycle. It moves heat in the opposite direction in which heat transfer would take place without the application of any external power.
Heat Pump System
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Components of Heat Pump
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A heat pump consists of different components like air handler, air output unit, refrigerant, compressor, reversing valve, and expansion valve. An air handler is an indoor unit, whereas the air output unit is an outdoor unit.
Components of Heat Pump
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Working Principle of Heat Pump
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- Refrigerant is sent through the air handler. Here heat is absorbed by the refrigerant. After absorbing heat energy the liquid refrigerant heats up and evaporates into gas form.
- The gaseous refrigerant passes through a compressor. Here the gas gets pressurised to heat up. The hot and pressurized refrigerant gas moves into the air output unit.
Working Principle of Heat Pump
- As the air outside the space is cooler than the hot compressed refrigerant gas, heat is transferred from the refrigerant to the outside air.
- The refrigerant condenses into a liquid state due to cooling. The cycle continues.
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Things to Remember
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- Refrigerators consist of components like evaporation coil, expansion valve, compressor, condenser, and refrigerant.
- A refrigerator works on the second law of thermodynamics.
- The refrigerator keeps the stored items cool in a recurring process called the vapour compression refrigeration cycle.
- The evaporation coils on the back of the refrigerator allow the hot refrigerant gas to dissipate its heat.
- A heat pump is a system that is used to heat or cool an enclosed space by transferring heat energy from a cooler space to a warmer space through the refrigeration cycle.
- A heat pump consists of different components like air handler, air output unit, refrigerant, compressor, reversing valve, and expansion valve.
- An air handler is an indoor unit, whereas the air output unit is an outdoor unit.
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Sample Questions
Ques: What are the five components of a refrigerator? (2 marks)
Ans: The five components of a refrigerator compressor, condenser, evaporator, expansion valve, and refrigerant.
Ques: What is a refrigerant? What are the different types of refrigerants? (3 marks)
Ans: A refrigerant can be a chemical compound that transforms easily from liquid to gas state. There are a different kinds of refrigerants as follows:
- Chlorofluorocarbons (CFCs) - R12
- Hydrochlorofluorocarbons (HCFCs) - R22
- Hydrofluorocarbons (HFCs) - R410A and R134.
Ques. What is a refrigerator? What is the basic principle of a refrigerator? (3 marks)
Ans: In a refrigerator a coolant is present. It is made to take the heat out of the stored items into the outer surroundings to keep the stored items at low temperatures. The two important aspects in the basic principle of a refrigerator are:
- Absorption of a certain amount of heat for changing of a liquid to a vapour by evaporation
- Release of the same amount of heat for changing a vapour back to the liquid state by condensation
Ques: Which cycle is used in refrigeration? What are its other applications? (2 marks)
Ans: Vapor-compression refrigeration is the cycle used in refrigeration. It is applied in electronic devices like refrigerators, air- conditioners, and heat pumps.
Ques: What are the different applications of refrigeration? (3 marks)
Ans: Refrigeration has different applications as follows
- Air can be separated into different constituents due to fractional distillation at different temperatures.
- It is used for the condensation and storage of ammonia gas in industries.
- It is used to dehumidify air by liquefying and separating the moisture present in it.
- It is used in the preservation of vegetables, organic chemicals, and explosives.
Ques: What are the different applications of a heat pump? (3 marks)
Ans: Heat pump can be applied in different fields as follows:
- It is used to heat enclosed spaces like a workspace, greenhouses, and domestic houses.
- It is used to heat water from heat generated in other processes.
- In industries, it is used to heat fluid substances before chemical reactions.
- It is used to recover process heat from other reactions.
Ques: Can air be used as a refrigerant in refrigerators and air coolers? (3 marks)
Ans: Yes, it can be used. In the air cycle, refrigeration systems air is used as the refrigerant. On compression and expansion air creates heating and cooling effects, Air is one of the best substitutes to CFC refrigerants as they cause adverse greenhouse effects in the atmosphere and also damage the ozone layer.
Ques: What are five important differences between refrigerator and heat pump? (5 marks)
Ans: The following table shows differences between a refrigerator and heat pump:
| Refrigerator | Heat Pump | |
|---|---|---|
| 1 | A refrigerator maintains the temperature of a system below the surrounding temperature. | A heat pump maintains the temperature of a system above the surrounding temperature. |
| 2 | It transfers heat energy from a low-temperature reservoir to a high-temperature thermal reservoir. The useful space is a low-temperature reservoir. | It transfers heat energy from a low-temperature thermal reservoir to a high-temperature thermal reservoir. The useful space is a high-temperature reservoir. |
| 3 | The evaporator is located inside the space. | The evaporator is located outside the space. |
| 4 | The condenser is located outside the space. | The condenser is located inside the space. |
| 5 | It is used in the preservation of vegetables, organic chemicals, and explosives. | It is used to heat enclosed spaces like a workspace, greenhouses, and domestic houses. |
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