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Refrigeration System Trainer aiding the technical requirements in Vocational Institutes

11-11-2021

The concept of refrigeration and its relation with thermodynamics is a crucial part of engineering & vocational studies in colleges. With an array of degree programs encompassing refrigeration, heating, ventilation, and air conditioning, students learn the basics and get a practical understanding of installing, repairing, and maintaining refrigeration system trainer units. Such programs pave a specialised technical career for students ranging from a technician to an engineer. 

When artificial refrigeration, as we know it today was not discovered, natural refrigeration was achieved by the use of evaporative cooling or ice. Ice was harvested during winters and stored in ice houses for use during summer and was also transported from colder regions to warmer places. In Europe, America, and Iran a number of ice houses were built to store ice. Materials like sawdust or wood shavings were used as insulating materials in these icehouses. Later on, cork was used as an insulating material.

Another popular method of making ice during the old days was nocturnal when water was cooled by radiation to the stratosphere. Owing to the popularity of ice, it was exported to other continents that were warmer. However, with the advent of artificial refrigeration in 1755, the natural method slowed its pace. Even though the first refrigeration machine that was designed by Scottish professor William Cullen, could only produce a small quantity of ice in the lab, it paved a scientific path for refrigeration units to evolve. 

After years of exploration and advancement, the refrigeration systems gained popularity to cater to the unending requirement of not only ice but air conditioning as well. Moreover, the understanding that air conditioning units do not create cool air has also reflected the refrigeration principle on the second law of thermodynamics. With the concept that heat will always flow from hot to cold spontaneously, the refrigeration system trainer units have become one of the many vital topics that a vocational or technical learning student practices in college. 

With the constant advancement in the refrigeration system trainer units, there is an exponential expansion in the need for technicians and engineers to operate & troubleshoot the refrigeration units that are used for both commercial and industrial purposes. Catering to the massive refrigeration industry, the students opting for specialised studies in this field need hands-on experience alongside the theoretical Refrigeration and Air Conditioning Technician program courses. 

 

What makes Refrigeration System Trainer acceptable in Vocational Institutes

Refrigeration cycles are vital in today’s industrial and domestic life. Many applications including, but not limited to, residential air conditioning, shopping malls heating ventilation & air conditioning, and food and liquid refrigeration operate with refrigeration cycles. Students graduating with a mechanical engineering technology degree, such as an associate, bachelor, or technical certificate need to have sufficient hands-on experience with refrigeration cycle operation, troubleshooting, analysis, and optimization.

Considering refrigeration technicians install and maintain refrigeration equipment, such as freezers and ice makers, as well as heating and air conditioning systems, they need a formal education to obtain a licence or enter the field as an apprentice. There, they receive on-the-job training under the supervision of an experienced or journeyman technician. This training is supplemented by practical lessons on actual refrigeration system trainer equipment.

However, the units that are deployed commercially or at domestic places are not fit for use as a trainer simply because they are not built for one. Nevertheless, using training equipment, that comes with preset electrical faults to troubleshoot and measure pressure, vacuum, flow rate, and temperature, works best for a group of students practising on one piece of equipment. It is also convenient for a teacher to impart thorough knowledge on the refrigeration concept in the presence of a trainer unit. 

The learning of thermodynamics concepts goes a long way for students to use their theoretical knowledge in the practical environment and get a clear picture of what lies ahead in their career. Students acquire a broad knowledge of the design, installation, and service techniques of heating and air conditioning systems for commercial and residential settings.

To ensure they are fully prepared for their career, they gain the know-how that they need through hands-on activities, learning to maintain, size, and select equipment for air conditioning and refrigeration application.

Students in different technical courses would apply thermodynamics and heat transfer principles to evaluate cycle efficiency, compressor power, and temperature rise and drop across the evaporator, condenser, compressor, and throttling valve.

The experimental information outcomes help students to understand theoretical principles in an experimental environment. This practical exposure not only helps the students visualize the refrigeration cycle but also provides an opportunity to compare the theoretical values, such as power consumed, EER, COP of the cycle, to the actual values obtained by the running unit. 

 

A Glance into Refrigeration History

It dates back to the 1800s when natural refrigeration was a vibrant part of the global economy that was harvested from the pristine rivers and lakes of the northern United States & New England, stored in large quantities in ice houses, and exported to the rest of the world. However, since sawdust was the insulation, the ice that reached the other parts of the world was adulterated with it. 

It was during this time when many mechanical-type refrigeration systems were being invented and used refrigerants such as sulphur dioxide, methyl chloride, ether, carbon dioxide, as well as wine, brandy, vinegar, etc.

The early refrigeration systems designed between 1850 and 1920 produced ice year-round to compete with harvested ice and the method used was the can ice system. The complaint then was that it required distilled water to prevent air bubbles in the ice. The ice industry continued to grow, and large plants with ice capacities were installed, most of which used steam-driven ammonia compressors. Atmospheric condensers also were appearing, as the supply of well water or river water was insufficient.

In the early 1900s, reciprocating compressors were refined. However, they still operated at low revolutions per minute. In the late 1930s and early 1940s, new compressor development produced a v/w-type compressor that operated at rotating speeds to 1,200 rpm and was smaller, lighter, and less expensive than the older vertical compressors.

Slightly better oil separators were also developed. These machines have been improved engineering-wise over the years and are still viable compressors for smaller refrigeration systems. Most manufacturers of this type of compressor have ratings for all refrigerants including ammonia, halocarbons, hydrocarbons, and CO2.

In the late 1960s, the helical screw compressor, invented in Sweden in 1935, was being manufactured in several countries. These efficient compressors had far more displacement than the available reciprocating compressors. Helical screw compressors can be used for almost any high-pressure refrigerant. In the late 1970s, a single screw compressor was introduced into the global market to compete with the twin helical screw compressor in the smaller displacement area.

All of these technological advancements have led to today’s efficient freezing methods for making ice and producing frozen foods.

 

Types of Refrigeration System trainer

There are four types of refrigeration system trainer units and to get ahead of the curve for the technical training purposes, below listed  are the details on each of them:

 

Mechanical-Compression Refrigeration Systems

The most widely used refrigeration cycle method is mechanical compression. It has applications in both air conditioning and commercial and industrial refrigeration. As the name suggests, these types of systems transfer heat by mechanically compressing refrigerant into a low-pressure, cold liquid and expanding it into a high-pressure, hot gas. 

 

Absorption Refrigeration

Heat is also transferred in absorption refrigeration systems by compressing and expanding refrigerant. These systems rely on the process of absorption and heat, instead of an electrically powered mechanical compressor, to move the refrigerant from the low-pressure side to the high-pressure side. 

 

Evaporative Cooling

Unlike the mechanical-compression and absorption refrigeration systems, evaporative cooling doesn’t use the traditional refrigeration cycle. Instead, these units, often called swamp coolers, cool warmer outdoor air by blowing it over water-soaked pads as it enters the home.

The water absorbs the heat from the air and evaporates. The cooler air is channelled into the home and the warm air out of it. 

 

Thermoelectric Refrigeration

Thermoelectric refrigeration system trainer units are unique considering they do not use refrigerant or water, instead these systems use an electric current and a thermocouple.

This type of refrigeration is generally used for small cooling loads that can be difficult to access, such as electronic systems.

All refrigeration systems work by transferring heat around, moving it from a designated area to somewhere else, thus cooling that designated area off and reversing the natural flow of heat with the application of energy. How this happens, however, varies among the four different types of refrigeration systems.

 

Different types of Refrigerants

Refrigerants are substances that can boil at a wide range of temperatures with the application or removal of pressure. Like all liquids, they absorb heat when they boil into gas and release it when they condense back into a liquid.

The basics of the refrigeration process deal with moving the refrigerant from the low-pressure side of the closed system to the high-pressure side. These refrigerants are used in various appliances such as Air conditioners, cooling machines, etc. They typically use the thermodynamic phenomenon of phase changes for converting gas into a liquid and vice-versa.

 

Refrigerants used in industrial spaces:

 

Water

Water is one of the substances filled with perfect chemical and thermodynamic properties. It has been used as a type of refrigerant for decades due to its easy availability. Well, it can’t be considered to be a refrigerant alone, but when chilled in cooling plants, it is put to use in the circuits for lowering the temperatures. For using water as a refrigerant, there is a need for ambient temperature that is higher than 100° C.

HFC R134A

This refrigerant is used in air-conditioned cars but also put to use in commercial refrigerant spaces in refrigerant piping. While talking about its features, it is enriched with minimal toxicity, non-combustibility, flawless thermal stability, and non-corrosiveness.

Hydrocarbons (HCS)

This refrigerant is filled with chemicals that are used in commercial refrigeration systems, air conditioning systems, and domestic refrigeration systems. This refrigerant is apt for industrial cooling as it has propane with zero ODP (Ozone depletion potential). 

But it needs specific safety installations. While working with Hydrocarbons, one has to keep certain things in mind for better operation, such as avoiding welding in the same area and staying away from sparks and wire.

Ammonia (R717)

Ammonia is considered to be the oldest and most commonly used refrigerant in industrial cooling plants. It is power-packed with halogen-free chemicals. Here, the application process is in smaller components, thereafter eradicating the need for big cooling plants. Besides, it has a lower molecular weight, high critical points, and a high coefficient of performance.

CO2 R744

This refrigerant has to be handled with care due to its heavyweight, while in a situation of leakage it might replace oxygen. On the brighter side, CO2 R744 has a minimum impact on the environment as it is non-toxic and non-flammable.

Refrigerants used in Buildings:

HCFC -22 (R-22)

It is one of the most commonly used refrigerants for residential heat pumps and air-conditioning systems, but leaks could be a cause of ozone depletion. Due to this situation, now there are other alternatives available for the same. In 2010, HCFC-22 became obsolete and was no longer used in air conditioners. However, as 2020 commenced, it can be used but only when recovered and recycled for use in the same system.

R-410A Refrigerants

It is one of the most commonly used refrigerants. Generally, it consists of two hydrofluorocarbon refrigerants, difluoromethane, and pentafluoroethane. R-410A is considered to be a non-ozone depleting refrigerant. When compared to R-407C and R-22, this refrigerant provides better energy efficiency.

It doesn’t contain chlorine and is a much better option than R-22. R-410 is widely used by air conditioner and refrigeration system manufacturing companies. It is also one of the most popular choices among people for chilling units, commercial refrigeration, and air conditioning.

R-600 Series Refrigerants

R-600 series refrigerant is enriched with natural sources having zero ODP and minimal possibility of global warming. It has to be designed with the utmost precision and used carefully to avoid fire issues. 

 

 

Why CO2 as a Refrigerant?

CO₂ is emerging as the go-to solution as traditional HFCs are phased out and retailers look for new ways to reduce their carbon footprint. Technology advancements in CO2 systems are making these systems more economically viable, in terms of both equipment and installation cost but also energy and operating costs. Here are a few advantages of using CO2 as a refrigerant:

 

Cost

There are a few notable benefits associated with opting for transcritical CO2. When compared to other refrigerants, carbon dioxide is much cheaper on a per-pound basis. Even though changing HFC or HFO systems over to CO2 isn’t practical, and it will take time for the return on investment to be realized, the cost savings of CO2 compared to traditional refrigerants are real and significant.

These cost savings come in the form of cheaper fluids as well as higher attainable efficiency for the system as a whole.

 

Sustainability

Unlike synthetic refrigerants such as R-134 and R-404A, which have high global warming potentials, CO2 has negligible global warming potentials. Because of this, CO2 is often referred to as “future proof,” meaning that as regulatory agencies continue to evaluate and outlaw synthetic refrigerants due to environmental reasons, CO2 will remain a viable option.

 

Heat Reclaim

Because CO2’s index of compression greatly exceeds that of synthetic refrigerants, its discharge temperature is higher than that of traditional HFC refrigerants. Additionally, CO2’s higher enthalpy means more of the rejected heat can be reclaimed, therefore making transcritical CO2 systems more attractive for heat reclaim purposes.

As a general rule of thumb, the higher the system’s ambient temperature, the more heat will be available for reclaim, however, CO2 systems still provide usable quantities of recoverable heat even in winter conditions. The reclaimed heat can then be routed to other areas of the operation, such as building HVAC or domestic hot water, improving the system’s efficiency.

 

 

A whole universe of science exists behind the ways refrigeration operates to keep the world cooler where refrigeration is just one part of the entire industry that encompasses keeping air conditioning, ventilation, and refrigeration (HVAC/R).

This makes the study & training of the subject vital for students in their vocational or technical institutes. Granted the size of the refrigeration industry and the massive number of students enrolling for the course, institutes need a relatively low-cost affordable educational air-conditioning and refrigeration trainer unit.

The unit as developed assists students in the mechanical engineering technology program and helps them practically understand the thermodynamic and heat transfer principles in an active learning environment. 

The unit as designed allows pressure and temperature reading which would allow the determination of the actual performance of the unit and the efficiency when using the power consumed by the unit. Compared to commercially available similar models, the developed unit provides a very attractive tool for educators.

Several component performances could be evaluated through the usage of the developed unit such as the evaporator, condenser,  compressor, and the system as a whole. Through the different applications and activities, the students learn the principles in an applied environment, experience the challenges and characteristics of each component, and make observations based on experimental and actual data rather than just theoretical principles.

 

Bestech Australia offers an extensive range of refrigeration system trainer units designed to teach students the basic principles of the vapour compression refrigeration cycle. The teaching equipment is curated to help students who are new to refrigeration understand concepts such as latent heat, superheat, subcooling, and saturation temperature. The emphasis is on the function and design of each of the major system’s components used in today’s facilities.

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