• SkillCat Team

How Does Domestic Refrigerator Work: A Complete Guide - Part 1

Updated: Sep 4

Working of Domestic Refrigerators: Chapter 1


Introduction to Domestic Refrigerator


In this module, we will introduce you to the domestic refrigerator. We will also discuss refrigerator size and capacity. Skip to quiz!!


Domestic Refrigerator

A refrigeration system provides cooling in a closed space by lowering the temperature. The refrigeration system we use in our home is a domestic refrigerator.


A domestic refrigerator is a home appliance to store food and drinks.

Unlike a large commercial system, a domestic refrigerator provides cooling to

a small area.


A refrigerator is a rectangular storage container that can easily fit in our kitchen space.

We also use them in ice cream parlors, small stores, and garages to keep food and drinks cold.


A refrigerator transfers heat from the space inside to its external environment. This will cool the space inside to a temperature below the room temperature.


If we keep food at room temperature, it can get spoilt easily. The growth of bacteria present in food slows down when we cool it. The cold temperatures inside the refrigerator help food stay fresh longer.


It is essential to keep perishable foods like meat and dairy products refrigerated. If we leave milk on the kitchen counter, bacteria will spoil it in two to three hours. However, keeping milk at a lower temperature will stay fresh for a week or two.


Refrigerator Compartments


Along with the temperature, the refrigerator also controls the humidity of the air. The temperature and the amount of moisture needed to retain the quality of food may vary. The table to the right shows the storage requirements of various food items.


For example, green leafy vegetables keep their crispness and nutrients best in cold, moist air. They are kept at a temperature in the range of 32-40 °F. On the other hand, blackberries and cherries are kept at 31-32 °F.


A refrigerator has two main sections to satisfy the storage requirements of different food items.

These sections include:

  • Refrigerator or fridge, and

  • Freezer

The optimal temperature range for the refrigerator is 34 ℉ to 42 ℉ to keep food safe yet unfrozen. The refrigerator section is larger than the freezer. We use the refrigerator section for storing ready-to-eat foods, such as dairy products, packaged foods, and beverages.


The refrigerator's freezer section is designed for food that needs to stay frozen or for long-term storage.

That is why we find the temperature in the range of -6 ˚F to 4 ˚F in a freezer.

The freezer is where we keep our frozen vegetables and ice cream.


Refrigerator Size and Capacity


There are a variety of refrigerators available in the market to satisfy customer needs. The measurements we need to keep in mind while selecting a refrigerator for any application are:

  • Refrigerator capacity,

  • Refrigerator size, and

  • Family size.

Recall that capacity of a HVAC system is the ability to heat or cool a given amount of space.

If your HVAC system is too small, it won’t be able to efficiently heat or cool your home. Similarly, if the system has a higher capacity than your home requires, it will heat or cool your home too quickly.


A refrigerator's cooling capacity is the ability of the cooling system to remove heat from stored food items. This differs from an air conditioner that circulates cool air to the room.


Recall that capacity of the air conditioning system is measured in tons. Unlike air conditioners, refrigerator capacity is specified by the storage volume from which heat is removed. It is the inside volume of the refrigerator and is expressed in cubic feet or liters.


The volume of the exact space inside the refrigerator is not easy to find. That is why refrigerator capacity is measured in liters. The capacity of the domestic refrigerators varies from about 4 cubic feet (113L) to 29 cubic feet (821L).

As discussed earlier, domestic refrigerators are available in a wide range of sizes and designs.

The size of the refrigerator is specified by its overall depth, width, and height.


The capacity and size of refrigerator varies as per our cooling requirements.

The image to the right shows industry recommended capacity of refrigerator depending upon family size.


A refrigeration system provides cooling in the space by lowering the temperature.

A refrigerator has two main sections to satisfy the storage requirements of different food items.

Unlike air conditioners, refrigerator capacity is specified by the storage volume from which heat is removed.



Domestic Refrigerator Configurations


In this module, we will learn about refrigerator types. We will also discuss their advantages. Skip to quiz!


Refrigerator Types

The refrigerator we use in our home is of two types. These include:

  • Freestanding refrigerator, and

  • Built-in and integrated refrigerator.

Freestanding refrigerators is a refrigerator that stands on its own. They are unattached and not built into any furniture or cabinets. They can be easily moved around if our kitchen needs to be rearranged.


Built-in appliances are permanently installed in the kitchen, so they can't be relocated.

They are integrated directly into the kitchen cabinetry and offer a professional, integrated look.


Freestanding Refrigerators


There are different types of freestanding refrigerators available in the market.

These include:

  • Compact and portable,

  • Single door,

  • Two-door,

  • Side by side, and

  • Side by side with the french door configuration

Compact and portable refrigerators are often used as a supplementary model in family rooms, offices, and other convenient places. Many fit on or under a horizontal work surface of the kitchen.


Compact refrigerators have a smaller capacity—mostly less than six cubic feet. That is why refrigerators of this type have a small freezer compartment for ice trays. They can be installed at any height and relocated easily due to their compact size.

Single-door refrigerators provide both fresh and frozen food storage in one compartment. Frozen food storage is located on the top side, whereas fresh food like vegetable storage is underneath the freezer.


Refrigerators of this type generally have a small capacity—mostly less than 14 cubic feet. Most shelf areas are within reach of a seated person. Freezer compartments have side-opening doors for easier accessibility.


Unlike a single-door refrigerator, two separate doors are present in a two-door refrigerator. One door is the main door for opening the refrigerator, and another one is for the freezer. This allows us to open the freezer without opening the main door.


Double door refrigerators are larger than a single door, and 4-5 member families all daily needs can fit into this easily. They are available in 6.0 cubic feet (170L) to 21.0 cubic feet (595L) capacity.


Much like a two-door refrigerator, side by side refrigerator is divided into two sides. One side is for the fridge compartment, and the other side is for the freezer. Here we find freezer on the left side and fridge on the right side.


A side-by-side refrigerator will provide ample vertical space to store taller items. However, horizontal space is slightly lesser than a two-door refrigerator.


Side by side refrigerator is split down in the middle, and the door hinge swing is shorter. This makes them a better fit in tight spaces. They are available in a capacity of 18.0 cubic feet (510L) to 25.0 cubic feet (710L).


Much like the side-by-side, the french door refrigerator is divided in half. Instead of two halves made horizontally, french door models have vertically oriented two sections. The bottom drawer is our freezer section.


Refrigerator with french door come in different configurations.

These types include:

  • Four, five, or six doors french door refrigerator and

  • Quad door refrigerator

Some of the french door models have two doors at the top and two drawers at the bottom. Quad door models are divided into quarters. In the quad door, we can convert one of the bottom doors into the regular refrigerator.


Built-in and Integrated Refrigerators


Unlike freestyle refrigerators, the built-in refrigerator is placed on our kitchen cabinet instead of placing separately. The sides of the built-in refrigerator flush against kitchen cabinetry, and the door comes out a few inches beyond the kitchen cabinet.


Much like a built-in refrigerator, the sides of the integrated refrigerator flush against kitchen cabinetry. The difference is the door of integrated models completely sticks with the cabinet.

When the door is closed, an integrated refrigerator looks identical to any other cabinet in our kitchen.


Both integrated and built-in refrigerators are available in different designs. The compressor of the built-in refrigerator is mounted on the top side. In contrast, the compressor is on the bottom side of the integrated refrigerator.

Built-in and integrated refrigerators deliver a sleek and luxury style we can’t achieve with freestanding models. They are expensive and designed for luxury or high-end kitchens.


We cannot move integrated and built-in refrigerators if our kitchen needs to be rearranged. Although, we can customize them to fit correctly

inside our kitchen.


Refrigerators are available in the market are freestanding, built-in, and integrated type. Freestanding refrigerators as the name suggests are standing freely. Built-in and integrated refrigerator is placed on our kitchen cabinet instead of placing separately.

Freezers


In this module, we will learn freezer configuration and types. We will also discuss their application. Skip to quiz!


Freezer Configuration


Recall that refrigerators are classified based on their arrangement are freestanding, built-in, and integrated types. Refrigerators are also classified according to the placement of the freezer inside our refrigerator. These include:

  • Top mount freezer, and

  • Bottom mount freezer

As the name implies, a top-mount freezer has its freezer placed above the fridge. A bottom mount freezer will have its freezer positioned below the fridge.


As discussed earlier, single-door and two-door refrigerators have a freezer compartment at the top. Two-door refrigerator variants are also available with a freezer at the bottom. Recall that all types of french door refrigerators have a freezer at the bottom.


Most of these top and bottom freezer units have refrigerator cabinets with single swing doors. The freezer compartment of the bottom freezer type has a drawer or swing door variety. Meanwhile, the freezer compartment of the top mount is swing type.


The bottom mount freezers of swing-door or a pull-drawer style have organizing baskets.

This will help you organize and access your frozen goods easily compared to top mount refrigerators.


The freezer configuration will affect our daily use. Since we tend to open the fridge compartment more often than the freezer, having the fridge at eye level will make it easier to use. We don't have to bend down each time to reach something inside the fridge.




Freezer Type


With a modern fridge, we require a lot of room to accommodate the refrigerator system. But without the freezer, the refrigerator system will be small and will fit into the tiniest of spaces.


Recall that the temperature in the freezer is below 0℉, so we can store food items for a longer time in the freezer. In a freezerless refrigerator, there will be no freezer compartment. This is why they are used in the small shops to keep drinks or snacks for a limited time.


Apart from a freezerless refrigerator, we might also need a machine whose sole purpose is to store frozen food. For these extra or frozen food storage for a longer time, there are dedicated freezers. These include:

  • Chest freezer

  • Upright freezer

Chest freezers are laid out horizontally with their doors opening at the top. They can either come with a solid hinged-top door or a sliding glass door. A chest freezer is used in an ice cream parlor, utility room, or house basement.


Upright freezers stand vertically – they look a lot like regular refrigerators except that they don’t have a fresh-food compartment. It is just a slim tall freezer compartment compared to the wide and bulky chest freezers. Upright freezers are used in the small garage or basement to save space.


Because of the built-in shelves, upright freezers are easier to organize compared to chest freezers. Upright freezers are also easier to reach into as the compartments are shallow. Meanwhile, a chest freezer only has one deep compartment for everything.


A top-mount freezer has its freezer placed above the fridge. A bottom mount will have its freezer positioned below the fridge. In a freezerless refrigerator, as the name implies, there will be no freezer compartment. Chest freezer and upright freezer are dedicated freezers to store frozen food.





Refrigeration Cycle


In this module, we will recall the refrigeration cycle used in the refrigeration system. We will also discuss the components of the refrigerator. Skip to quiz!



Refrigeration Cycle


A refrigerator removes heat from closed space by using the basic refrigeration cycle. Recall that the four main components of the basic refrigeration cycle are:

  • Compressor,

  • Condenser,

  • A metering device, and

  • Evaporator

Recall that a refrigerator works by transferring heat from the space inside to its outside. It uses a refrigerant to do this. A refrigerant is a fluid used in refrigeration systems to transfer heat.


Recall that ODP is the capacity of a refrigerant to damage the ozone layer. Recall that GWP is the capacity of a ref to cause global warming. These factors measure the environmental impact of the refrigerant.


The earlier generation of refrigerators used R-134a refrigerant. A majority of modern domestic refrigerators use R-600a refrigerant. This is because R-600a has lower ODP and GWP compared to R-314a.


The molecules of vapor refrigerant are pressed closer together to increase the pressure. As pressure increases, temperature also increases. The high-pressure, high-temperature vapor refrigerant enters the condenser.


Heat is removed from the vapor refrigerant by the flow of relatively cool air over the condenser. As the high-temperature vapor refrigerant transfers its heat to the cool air, it changes from vapor to liquid. The liquid refrigerant is then sent to an expansion device.

When the refrigerant enters the throttling valve, it expands and releases pressure. Consequently, the temperature drops at this stage as pressure and temperature are related.

The liquid refrigerant is then circulated through an evaporator.


In the evaporator, the refrigerant absorbs heat from the closed inside space of the refrigerator. Let us discuss each of these components in detail.



Compressor


Recall that the compressor’s main job is to increase the pressure of the refrigerant.

We see the following types of compressors in the refrigerator.

  • Reciprocating compressors,

  • Scroll compressors, and

  • Screw compressors

These are categorized based on how they work.

Recall that a motor drives reciprocating compressors. They have a piston and cylinder, just like a car engine.


Domestic refrigerators usually have hermetically sealed reciprocating compressors. Recall that the motor and the compressor are contained and sealed inside a single shell in hermetic compressors. They are also relatively quiet, which makes them ideal for household use.


Recall that the scroll compressor consists of two matching scrolls, one stationary and the other rotating around the first. One scroll rotates around the other in a circular motion to compress the refrigerant.


Screw compressors also use a circular motion to compress refrigerant. This is why they are sometimes called rotary screw compressors.


Condenser

Recall that the condenser’s main job is to cool down the refrigerant. The main types of condensers in the refrigerator are:

These condensers are classified based on their structure.


A wire and tube condenser is similar to a fin and tube condenser. The difference is, there are no plate-like fins in the wire and tube type of condenser. In their place, thin wires are used. The wires act as fins to increase the heat transfer area.


The reason for wires in place of plate fins is because the condenser can be seen outside in the refrigerator. If we use the plate fins, it may cut someone's hand. So we use wires that can be made relatively safer.


Plate surface condensers are flat, as shown in this image. The refrigerant carrying tubes are attached to the outer walls of the refrigerator. Unlike fin tube condenser, the whole body of the refrigerator acts like a fin and no separate fins are provided.


Metering Device

Recall that the metering device’s job is to decrease the pressure of the refrigerant.

Refrigerator mainly use the two main types of metering devices:

  • Capillary tube, and

  • Thermal expansion valve (TXV)

We will discuss how these metering devices

work in refrigerators in detail.


Capillary tubes have a small diameter, which reduces the amount of refrigerant that can flow through at a time. This decreases the pressure of the refrigerant. Let’s take a look at a video explaining this concept.


The refrigerant in the tube starts off with very high pressure. As it flows through this long thin capillary tube, refrigerant loses its pressure, and we only get a slow stream of water at the end.


Capillary tubes are more susceptible to clogging and damage. That is why modern refrigerators use thermostatic expansion valves. TXV’s controls the amount of refrigerant that flows into the evaporator based on the evaporator outlet temperature.



Evaporator


Recall that the evaporator’s job is to absorb heat from the space inside the refrigerator. Refrigerator mainly use the two main types of evaporators:

  • Bare tube, and

  • Plate surface evaporators

Bare tube evaporators are the simplest type of evaporator. These evaporators are generally just refrigerant tubes that are made of either copper or aluminum. There is refrigerant inside the refrigerant tube changes from liquid to vapor by absorbing heat from the air.


Plate surface evaporators are flat, as shown in this image. These evaporators are made up of two plates that are joined together. Usually the two plates are made of aluminum because it conducts heat well.


Liquid refrigerant flows through a tube made between the two plates. This tube carrying refrigerant is the raised part of the plate that we can see in this image.


Plate surface evaporators are an improvement over bare tube evaporators. This is because they have a higher surface area for air to flow over them. The higher the surface area, the more heat can be transferred into the refrigerant.


In plate surface evaporators, food can be placed directly on the plate for more effective cooling. This improves heat transfer even more.


Unlike bare tube evaporators, there are no tubes in plate surface evaporators. This makes them easy to clean and defrost.


Plate surface evaporators are less likely to leak refrigerant and safe to handle. This is because plates are stronger than tubes. As there are no fins, there is no danger of cutting our hands.

This makes them suitable for refrigerators.


We see the following types of compressors in refrigerators:

  • Reciprocating compressors,