Working Principle and Parts of Home Refrigerator

 

Domestic Freeze or Refrigerator 

• Refrigerators work by using refrigerant which circulates inside the coils
•   It changes from a liquid to a gas. This process is called evaporation cooling
• The most refrigerators temperature is kept between 0 to 5 degrees Celsius  ( -9 to 0°F) for maintaining fresh vegetables
• Some freezer-only units can operate at lower temperature of  −34 °C (−29 °F) and lower as per need of their purpose.
• Food items are placed in various compartment of refrigerators
  • Freezer section (lowest temperature) for ices making
  • The doors side space for cold-drinks
  • Upper shelves for vegetables
  • Lower shelves for raw vegetables
  • Crisper drawers.

• Before using the refrigerators, we have to understand working principle of refrigerators considering electric safeties

How does the home refrigerator work?

• A coolant is used to absorb heat from the food to be cooled
• The coolant is initially compressed by the compressor, which heats it up
• The hot coolant is then passed through the condenser coils at the back of the fridge, where the heat is dissipated. The coolant then passes through the expansion valve, where it expands and becomes a cold gas
• The low-temperature coolant absorbs the heat from objects and then the heated coolant releases heat on the back side of in the condenser coil of the freeze

Simple Refrigeration Cycle

The working fluid is coolant and it passes through the evaporator, condenser, expansion coil and refrigeration chambers

• Compressor
• Condenser
• Evaporator
• Capillary tube
• Thermostat
• Capacity control system
• Receiver

 

Working principle of refrigeration cycle

The working principle of a refrigerator is based on the transfer of heat from a low-temperature environment (inside the refrigerator) to a higher-temperature environment (outside the refrigerator). This process is achieved through a combination of several components and thermodynamic principles. Here’s a simplified explanation of how a refrigerator works:

1. Refrigerant:
   • The refrigerator uses a refrigerant, a substance with properties that allow it to absorb and release heat efficiently.
   • The most commonly used refrigerants are hydrofluorocarbons (HFCs) or hydrochlorofluorocarbons (HCFCs).
2. Compression:
   • The process begins with a compressor, which is usually located at the back of the refrigerator.
   • The compressor’s role is to compress the refrigerant gas, increasing its pressure and temperature. As a result of compression, the molecules in the gas become closer together, and their energy (temperature) increases.
3. Condensation:
   • The high-pressure, high-temperature refrigerant gas then flows into the condenser coils, located either at the back or underneath the refrigerator. The condenser coils are designed to dissipate heat efficiently.
   • As the hot refrigerant gas flows through the coils, it comes into contact with the cooler air in the room or the outside environment.
   • The heat from the refrigerant is released to the surroundings, causing the refrigerant to condense into a high-pressure liquid.
4. Expansion:
   • The high-pressure liquid refrigerant then moves through a small opening called the expansion valve or capillary tube.
   • This valve restricts the flow of the refrigerant, causing a pressure drop.
   • As a result, the refrigerant expands rapidly, leading to a decrease in pressure and temperature.
5. Evaporation:
   • The low-pressure, low-temperature refrigerant then enters the evaporator coils, which are usually located inside the refrigerator. The evaporator coils are in direct contact with the air inside the refrigerator.
   • As the warm air from inside the refrigerator passes over the cold evaporator coils, heat is transferred from the air to the refrigerant. This causes the refrigerant to evaporate, transforming it back into a low-pressure gas.
6. Absorption of heat:
   • As the refrigerant absorbs heat from the air, it cools down the air inside the refrigerator, creating a cold environment for storing food and other items.
7. Circulation:
   • The compressor then draws the low-pressure gas back into the system, starting the process over again.
   • This continuous circulation of the refrigerant allows the refrigerator to maintain a cool temperature inside while transferring heat outside.

• By continuously repeating these steps, a refrigerator can maintain a cool internal temperature, keeping food fresh and preserving its quality.
• The process of heat transfer and refrigerant circulation is what enables the refrigerator to extract heat from the inside and release it outside, thereby cooling the contents of the refrigerator.

 

1. When food items are kept in the fridge, the cool refrigerant is passed.
2. The heat from the food items is absorbed by the refrigerant.
3. The heat absorbed by the refrigerant gets transferred to the relatively cooler surroundings outside.

• The cooling fluid is passed through the expansion coils inside the fridge and its pressure dec

Major Parts of Freeze

The details of the components are mentioned below

 

Evaporator

• The evaporator in the refrigerator is located inside a fridge and makes the items in the refrigerator cold.
• It removes the unwanted heat from the food items through liquid refrigerant.
• The pressure of the liquid refrigerant must be low.
•  Two variables decide the low pressure- first, heat gets absorbed from the product to the liquid refrigerant and the second one is the removal of air pressure by the compressor.
• Through evaporation, the refrigerant turns liquid into a gas and cools down the area. Hence, it produces the appropriate environment for storing and preserving food.

 

Compressor

• The compressor and the electric motor are kept in a single enclosed container
•  A reciprocating type compressor is generally used  in the fridge
• It is used to increase the pressure of refrigeration and keep the recirculation of coolant.
• The compressor can make the refrigerator hot by putting pressure on the warm part of the circuit.

• It consists of an electrical motor that sucks in the refrigerant from the evaporator and compresses it to make a hot and high-pressure gas (coolant).
• It helps to compress and convert low-temperature to high temperatures.

 

• Cross section of compressor is shown below

Condenser

• It is placed in the rear of the fridge.
• It is useful to extract heat from the refrigerant.
• It cools down the refrigerant and changes the matter. That means it changes gas back into liquid. This is the refrigerator cooling system.
• To remove from the condenser coil, fans above the condenser unit draw air over the condenser coils
• The desired range of temperature of condensation: -15 degrees to -1 degrees C
• The coolant vapor cools down to form a liquid refrigerant.

 

Expansion coils  (Capillary tubes)

• It is an expansion coil and consists of a thin piece of tubing.
• The liquid refrigerant is routed through the capillary coils and distributed into the low-pressure environment of the evaporator.

 

 

 

Thermostat

• It is a knob that adjusts the temperature setting
• The thermostat helps to control the cooling process in the fridge by monitoring the temperature and switching the compressor on and off.
• When an object is cold enough inside the fridge, the sensor can sense that and turn off the compressor.
• When it senses too much heat, it switches the compressor on, and the cooling process begins again.

 

Capacity control system

• It regulates the power and energy consumption
• It manages dehumidification and decreases compressor cycling.
• It has an on/off option, which is the simplest form of capacity control.

Receiver

• The receiver acts as a vapor seal.
• These are made for both horizontal and vertical installation.

 

Refrigerant Used in Refrigerator

n household refrigerators, the most commonly used refrigerants are hydrofluorocarbons (HFCs) or hydrochlorofluorocarbons (HCFCs). The specific refrigerant used can vary depending on the age and type of refrigerator. Here are a few examples:

R-134a:

• This HFC refrigerant has been widely used in refrigerators and air conditioning systems.
• It has a relatively low global warming potential (GWP) compared to some older refrigerants.

R-410A:

• Another HFC refrigerant is commonly used in newer refrigeration and air conditioning systems.
• It is known for its high energy efficiency and is often used as a replacement for older refrigerants like R-22.

R-600a

• This is a hydrocarbon refrigerant, specifically isobutane.
• It is becoming increasingly popular due to its low environmental impact and excellent energy efficiency. R-600a is commonly used in newer refrigerators, especially in Europe and many other regions.

How to select Refrigerant 

• It’s worth noting that there has been a global effort to phase out high-GWP refrigerants, including HFCs and HCFCs, due to their contribution to climate change.
• As a result, there has been a shift towards using more environmentally friendly refrigerants with lower GWP, such as hydrofluoroolefins (HFOs) and natural refrigerants like carbon dioxide (R-744), ammonia (R-717), and hydrocarbons.
• The specific refrigerant used in a refrigerator can vary depending on factors like the manufacturer, model, and regional regulations.
• It’s always best to refer to the refrigerator’s documentation or contact the manufacturer for the specific refrigerant used in a particular appliance.

Major issues in Refrigerator

• Due to long use or poor maintenance, you may face practical issues in refrigerators. You can refer the post on this site. The cost can be reduced by regulars maintenance cost
• There are some  common Problems and need to fix in time in your refrigerator

• • Cooling problem
  • Buildup of Frost in the Ice Dispenser.
  • Ice Maker is not working
  • Freezer not too cold
  • High Cycling of refrigerator
  • Fresh Food Compartment is not cold
  • Sheet of Ice on the Freezer Floor.

Working Principle of Electric Geyser: Benefits, Parts and Types

 

Is a water heater called a Geyser?

• Water heater is a also called as geyser when the electricity is used as source of heating using the electric resistance rod.
• It was the invention of an Englishman named Benjamin Waddy Maughan who named his invention after the well known Icelandic hot spring called Geyser.
• In some parts of the world, particularly in India and South Africa, a water heater is commonly referred to as a “geyser.”
• This term is a regional or colloquial way of describing a device that heats water for domestic use, such as for bathing, washing dishes, and laundry.
• The term “geyser” likely originated from the natural geothermal geysers that erupt with hot water and steam, and it was used to describe water heaters that mimic the action of these natural phenomena by providing hot water on demand.
• In many other English-speaking regions, especially in the United States and Canada, the term “water heater” or simply “hot water heater” is more commonly used.
• So, whether you call it a “water heater” or a “geyser” depends on the regional language and colloquialisms in use.
• The function of the appliance is the same: to heat water for various household purposes.

How does an Electric Geyser heat up water?

• The geyser converts electrical energy into heat energy using electric resistance.
• That heat is transfer to surrounding water in the geyser or water bucket.
• After heating the convection flow is formed in the water

• Water geysers, also known as hot water heaters or simply heaters, are devices that are used to heat water for various domestic purposes such as bathing, cleaning, and cooking
• These appliances have become an indispensable part of modern households, providing a constant supply of hot water at the turn of a tap
• The most common type of water geyser is the storage tank heater, which works by heating water in an insulated tank and maintaining the temperature of the water until it is needed
• The tank is typically mounted on the roof or on the wall of a building and can range in size from 20 to 80 gallons, depending on the needs of the household. The tank is usually made of stainless steel or glass-lined steel, which helps to prevent corrosion and extend the life of the heater.

Main Benefits a water Geyser

• One of the main benefits of having a water geyser is the convenience of having a constant supply of hot water
• This eliminates the need to wait for water to heat up on the stove or in a pot, and it also allows for multiple people to use hot water simultaneously without having to wait
• Additionally, many modern water geysers come equipped with a variety of features such as temperature control, energy-saving modes, and safety features such as automatic shut-off
• However, it is important to keep in mind that water geysers can be expensive to purchase and install, and they also consume a significant amount of energy. Therefore, it is important to choose a water geyser that is both efficient and meets the needs of the household
• Factors such as the size of the tank, the type of fuel source, and the type of heating element should all be considered when making a purchase.

Benefits of Electric Geyser Popular over solar water heater

•   To get the hot water continuously in all season, an electric geyser or water heater  (EWH) is more useful device
• EWH easy to install anywhere with the electric power
• Its water temperature can easily be regulated automatically by a thermostat
• It works on the principle of thermal storage i.e. the water is preheated by immersion water in a storage vessel and is kept for future use. To get the water in a storage vessel and is kept for future use
• To get the hot water from time to time, the storing vessel is provided with thick insulation or it is properly legged to dissipate the heat.
• The heating element is fixed at the bottom horizontally or vertically
• As the water heater is switched ‘on’ the cold water is heated up, becomes lighter and starts moving up while the cold water being heavier comes down
• Thus due to this circulation of water, we can get hot water from the outlet valve. If the element is fixed horizontally, the water above it, is heated very slowly but when the element is fixed vertically, the water surrounding this is heated up very soon. So the vertical fitting of the element in the water heater is more referred.

 

What are Parts of Electric Geyser?

• The electric geyser consists of a water tank fitted with two pipes:
  • Inlet pipe for cold water
  • Outlet pipe of hot water
• The water tank is fitted with heating elements that are controlled by thermostats
• The thermostats ensure that water is not heated above a set temperature value
• The tank is normally covered with some insulating material and enclosed inside a metal casing.

Water Geyser Installation and Maintenance

Important Points to take care of during the geyser installation:

• Ensure that there is sufficient space available for the geyser unit in the bathroom
• Correct height from the ground
• Ensure continuous water supply
• The Geyser unit must be installed at the correct height from the ground.
• Firm wall structure.
• Unblocked water pipes.
• Safe electrical connections.

 

• Typically, geysers have a lifespan of five years and over this time they corrode.
• Homeowners can lengthen the lifespan of their geysers by maintaining them properly

Major Parts of Installations and process

An electric water heater works by using electrical resistance to heat water inside a tank. Here’s a step-by-step explanation of how it operates:

Cold Water Inlet:

• Cold water from your home’s plumbing system enters the water heater through a pipe connected to the bottom of the tank.
• This cold water is then stored in the tank until it’s needed.

Heating Elements:

• Inside the tank, there are one or two heating elements made of materials like stainless steel or copper.
• These heating elements are connected to electrical wires and are submerged in the water.

Thermostat Control:

• The water heater has a thermostat, which allows you to set the desired temperature for the hot water.
• When the water temperature inside the tank drops below the set temperature, the thermostat signals the heating elements to turn on.

Electric Resistance Heating:

• When the heating elements receive the signal from the thermostat, they start heating up.
• Electric current flows through these elements, and they resist the flow of electricity, which generates heat.
• This heat is transferred to the water in the tank, raising its temperature.

Heat Distribution:

• The heating process begins at the bottom of the tank, where the heating elements are located.
• As the water in the vicinity of the heating elements gets warmer, it rises to the top of the tank. This movement, known as convection, causes the cooler water at the top of the tank to move down to the bottom to be heated. This cycle continues until the entire tank reaches the desired temperature.

Temperature and Pressure Regulation:

• To ensure safety, electric water heaters are equipped with a temperature and pressure relief valve. If the water temperature or pressure inside the tank exceeds safe levels, this valve opens to release excess pressure and prevent the tank from exploding.

Hot Water Outlet:

• When you open a hot water tap or use a hot water appliance in your home, hot water is drawn from the top of the tank through a pipe connected to the hot water outlet.
• This hot water is then delivered to the point of use, such as a faucet or showerhead.

Energy Efficiency:

• Many electric water heaters come with insulation to reduce heat loss from the tank.
• This insulation helps the heater maintain the water temperature efficiently, reducing energy consumption and heating costs.

Maintenance:

• Over time, sediment and minerals from the water can accumulate at the bottom of the tank.
• This can reduce the heater’s efficiency. Periodic maintenance, like flushing the tank to remove sediment, is necessary to keep the water heater operating efficiently.
• Electric water heaters are relatively straightforward and reliable appliances, commonly used in homes to provide a continuous supply of hot water for bathing, washing dishes, laundry, and other domestic purposes.
• They are available in various sizes to meet the hot water needs of different households.

 

Classification of Electric Geyser or Electric Water Heater

Electric geyser can be classified in the following ways:

Immersion Water Heater or Electric Rod

• It can be put in any vessel full of water and by switching on, the water is heated up
• This is risky you have to monitor heating of water
• It is a portable and cheap and has been described before. You can refer the details of immersion water heater in the post. You have to control the temperature manually rather than thermostat. However, the electric geyser is more safer than it.

 

 Self-contained Heaters

These are of two types:

Pressure Type Water Heater.

• These consist of a storage vessel, heavily legged, electrically heated and provided with a thermostat system.
•   In other words it is called cistern type water heater as it works on atmospheric pressure.
• This type of water heater is used at that place where the hot water is required at more than one service points with one heater only.
• This heater gets its supply of cold water from the cistern (over head tank) connected with the water mains and the water controlled with the help of a float valve.
• The copper pipes connected with the heating chamber are used to supply the hot water under pressure to different service points which are controlled with a tap.
• The element and thermostat are fixed at the removable plate fitted on the base of the water heater for their easy service and to remove them easily.
• The water is of 750 to 3000 W.

These are of two types:

• (i) Constant volume pressure type water heater:
  • In this heater, the hot water drained off is replaced equally with cold water having equal volume.
  • So it is called a constant pressure type water heater
• (ii) Non-constant volume pressure type water heater:
  • in this heater,  the rate at which the hot water flows out is not the same at which the cold water enters into the heating chamber.
  • So it is known as non-constant or varying volume pressure type water heater Read more on Sarthaks.com –

Non-pressure Type Water Heater

• This type of water heater is used at that place where the hot water is required only at one service point e.g. for wash-basins and sinks etc. Such water heaters have an open outlet i.e. not having any stop-cock.
• Its water is controlled from the inlet side.
• These contain two cylindrical vessels, one fitted inside the outer. The inner vessel consists of heating chamber made of tinned copper. Inside it, the heating element and thermostat are fixed vertically at the bottom.
• The outer vessel is made of lead-coated-steel and painter outside with enamel paint.
• The space between the two vessels is filled with heat resisting insulating material to reduce heat loss.
• The temperature of the water is controlled automatically with thermostat.
• The inlet and outlet pipes are chromium plated to avoid corrosion.
• The cold water flows from the cold water supply pipe (inlet pipe) and enters in the heating chamber and is controlled by a valve. The hot water flows out from the top of the heating chamber through the hot water pipe (outlet pipe).
• An anti drip device is provided with the hot water pipe to cut off the quick hot water supply and to prevent the water to be drained off through the cold water pipe valve when the supply of cold water fails.
• As the hot water pipe is an open outlet, when the cold water inlet valve is opened, the cold water rushes into the heating chamber, displaces and forces out an equal quantity of hot water through the hot water outlet pipe.  To save the water heater from the developed pressure inside the heating chamber, a vent plug is fitted at the top which allows extra pressure in atmosphere. The wattage of this water heater is about 750 to 2000 W etc.

Classifications based on Applications 

Space Heaters

There are several types of electric heaters designed for various purposes and heating needs. Here are some common types of electrical heaters:

• • Convection Heaters: These heaters warm the air in a room through natural convection, where cool air is drawn in, heated, and then rises. Examples include oil-filled radiators and ceramic heaters.
  • Radiant Heaters: Radiant heaters emit infrared radiation, which directly heats people and objects in their line of sight. They provide quick, focused heat and are ideal for spot heating in small areas.
• Baseboard Heaters: These heaters are typically installed along the baseboards of rooms and use convection to heat the air. They are often used as supplemental heating sources.
• Wall Heaters:

Wall heaters are mounted on walls and provide localized heating for specific rooms or areas.

hey come in various types, including fan-forced and convection heaters.

Industrial Applications of Heaters 

• Fan Heaters:
  • Forced-Fan Heaters: These heaters use an internal fan to blow air over heating elements and distribute warm air quickly. They are efficient for heating larger spaces.
  • Tower Heaters: Tower heaters are tall, compact heaters equipped with a fan. They can oscillate to distribute warm air evenly in a room.
• Ceiling Heaters: Ceiling-mounted heaters are often used in commercial or industrial settings. They blow warm air downward to heat large spaces efficiently.
• Underfloor Heating: This type of heating system is installed beneath the floor, typically using electric resistance cables or mats. It provides even, radiant heat and is common in bathrooms and kitchens.
• Infrared Heaters: Infrared heaters emit infrared radiation, which heats objects and people directly. They are energy-efficient and can be used for both indoor and outdoor heating.
• Portable Heaters: Portable heaters are small, easily movable units that are convenient for providing temporary heating in specific areas. They include various types such as space heaters, ceramic heaters, and radiant heaters.
• Panel Heaters:
  • Panel heaters are flat, wall-mounted units that heat the surrounding air using convection.
  • They are typically slim and can be a discreet heating solution.
• Towel Warmers:
  • Towel warmers are designed to heat towels in bathrooms, making them warm and comfortable to use after bathing or showering. They are often wall-mounted or freestanding.
• Kick Space Heaters:
  • These heaters are installed beneath cabinets or counters in kitchens or bathrooms to provide extra heat in areas where space is limited.
• Garage Heaters: Designed for heating garage spaces, these heaters come in various forms, including forced-air garage heaters and infrared garage heaters.
• Heat Lamps: Heat lamps use infrared radiation to provide localized heat. They are commonly used in bathrooms or for keeping food warm in restaurants.
• Each type of electric heater has its advantages and disadvantages, and the choice of heater depends on factors such as the size of the area to be heated, energy efficiency, safety considerations, and the specific heating needs of the user.

Summary 

•  Electric Water geysers (EWG) have become an indispensable part of modern households, providing a constant supply of hot water for various domestic purposes
• With several types of water heaters available on the market, it is important to choose one that is both efficient and meets the needs of the household
• Regardless of the type of water geyser chosen, it is essential to have it installed and maintained by a professional plumber to ensure that it operates safely and efficiently.

Automatic Street Light Control Circuit using LDR

 Following is yet another simple Electrical/Electronics project for automatic street light control systems especially for students, newbies and hobbyists.

Features:

• It is a dark detector circuit based on LDR and a transistor (BC-547 NPN) which automatically switches ON and OFF the street light system.
• It automatically switches ON street lights when the sunlight goes below the visible region of our eyes. (e.g. in the evening after sunset). 
• It automatically switches OFF the lights when sunlight falls on it ( i.e. on LDR ) e.g. in the morning, the sensor called LDR (Light Dependent Resistor) senses the light just like our eyes and deactivates the circuit.

Advantages:

• The automatic operation of street light controlling systems help to reduce the energy consumption as compared to the manually operated street light controlling operations. This is because there is a delay in the earlier switching operations both in morning (during sunrise) and evening (during sunset).
• On sunny and rainy days, ON and OFF time is noticeably differ which is one of the major disadvantages of using timer circuits or manual operation for switching the street light system.

Components Required:

• LDR – Light Dependent Resistor
• 2 Nos. of transistors. (NPN transistor – BC547 or BC147 or BC548)
• Resistor- 1kΩ, 100kΩ, 330 Ohm & 470 ohms.
• Light emitting diode (LED) – Any color
• Connecting wires – (Use single-core plastic-coated wire of 0.6mm diameter (the standard size) or any wire used in computer networking).
• Power supply-6V or 9V

Procedure

• Insert first transistor Q1-BC547 (NPN) on breadboard (or general PCB) as shown in the circuit diagram 1.
• Connect another transistor Q2- BC547 (NPN) on the breadboard as in step 1.
• Connect  wires across the emitter pin of both transistors and -Ve terminal of battery (lowest/bottom row of breadboard.)
• Connect  a wire across the Collector pin of transistor Q1 and Base pin of transistor Q2.
• Connect a resistor 1K across the positive terminal of battery (topmost row of breadboard) and Collector pin of transistor Q1.
• Connect  Light Dependent Resistor (LDR) across the positive terminal of battery (topmost row of breadboard) and base terminal of transistor Q1.
• Insert a resistor- 330 Ohm across base pin of transistor Q1 and negative terminal of battery (lowest bottom row of breadboard).
• Connect a resistor 330R across the positive terminal of battery (topmost row of breadboard) and anode terminal of LED (Light emitting diode) & Connect the cathode terminal of LED to Collector pin of transistor Q2.

The simple circuit is ready for testing now. Connect 6V to 9V battery terminals to the circuit as shown in fig and see the output. As you block light falling on the Light dependent resistor(LDR), the LED glows and vice versa.

LED GLOWS EVEN IN LESS DARKNESS. Use torch light or lighter if the LED glows in less darkness. In addition, you can try to adjust the sensitivity of this circuit by using a variable resistor in place of R1-300 Ohm. You may use other resistances as well, (e.g., 1KΩ, 10KΩ and 100KΩ, etc.)

Pictorial Story: (Click images to enlarge)

Components & Schematic Circuit Diagrams for Automatic Street Light Control System

Circuit Diagram 1. Automatic Street Light Control System.(Sensor using LDR & Transistor BC 547.). We have tried and Cicuit#1 in this  tutorial but you may also try the second one (Circuit#2) mentioned below ight after circuit no 1.

Circuit Diagram 2 . Automatic Street Light Control System using LDR and two nos. of Transistor BC 547.

Whenever light falls on the LDR (Light Dependent resistor), the LED is OFF i.e. the LED does not glow.

In the dark (e.g. when light is blocked to the LDR), the LED is ON i.e. the LED is ON.

Snapshot taken out from the Video.

Some Basic Electronic Projects Circuit Diagrams based on LDR

• Automatic Street Light Control System using LDR 
• Electronic Eye Circuit – Based on LDR
• Automatic LED Emergency Light Circuit using LDR
• Automatic Night Lamp Using LDR