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Laboratory Refrigerators and Freezers – Principle, Parts, Applications

Refrigerators and freezers of the residential variety are meant to store food and beverages. Refrigerators of the household variety are only authorised in laboratories for ...

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Refrigerators and freezers of the residential variety are meant to store food and beverages. Refrigerators of the household variety are only authorised in laboratories for the storage of non-flammable or non-explosive substances. The in-built ignition sources (temperature controls, thermostats, light switches, light assemblies, fans, defrost mechanisms, etc.) in the freezers provide a flammable or explosive hazard if these machines are utilised to store flammable materials or unstable substances. In order to store flammable or explosive goods in a refrigerator or freezer, the refrigerator or freezer must be UL-rated.

The purpose of laboratory refrigerators is to cool samples or specimens for preservation purposes. They consist of refrigerated units for preserving blood plasma and other blood products, in addition to vaccinations and other medical or pharmaceutical supplies. They differ from regular refrigerators found in homes and restaurants in that they must be absolutely hygienic and dependable.

In order to limit the risk of bacterial contamination and explosions of volatile substances, laboratory refrigerators must maintain a constant temperature. To reach a high level of precision, the refrigerator requires constant air circulation and a fan to maintain a uniform temperature. When the door is opened, the fan switches off to prevent cold air from escaping the unit. Laboratory refrigerators include distinct compartments to minimise cross-contamination and can store blood and vaccinations, among other medical supplies.

Working Principle of Laboratory Refrigerators and Freezers

A refrigerator operates by employing a coolant to transfer heat from food items to the surrounding environment. The coolant is initially heated by compression by the compressor. The heated coolant is then circulated through the condenser coils at the back of the refrigerator, where the heat is expelled. After passing through the expansion valve, the coolant expands into a chilly gas. This cold gas is circulated through the expansion coils within the refrigerator, where it absorbs the food’s heat and maintains its coldness.

Simply put, there are three steps involved in the operation of a refrigerator or fridge:

  1. Inside a refrigerator, food is circulated with cool refrigerant.
  2. The refrigerant absorbs the food’s heat.
  3. The absorbed heat is transferred by the refrigerant to the considerably cooler outdoor environment.
Parts/Components of Laboratory Refrigerators and Freezers
Parts/Components of Laboratory Refrigerators and Freezers | Image Source: scienceabc.

The refrigeration and cooling process is based on the removal of heat from one region and its transfer to another. When a low-temperature liquid is brought close to things to be cooled, the heat from the objects is transferred to the liquid, which then evaporates and removes the heat.

You may already be aware that gases become hotter when compressed and colder when allowed to expand. This is why a bicycle pump feels warm when used to inflate a tyre, whereas perfume spray feels frigid.

The tendency of gases to become hot when they are compressed and cold when they are expanded, as well as the use of sophisticated technologies, allow a refrigerator to cool its contents.

A Laboratory Refrigerators and Freezers Must-have features to consider

  • A refrigeration system designed for maximum cooling efficiency.
  • Low power usage yields substantial energy savings.
  • System of forced air circulation for improved temperature homogeneity and rapid recovery following door openings.
  • Intelligent automated defrost function that only defrosts when necessary.
  • User-friendly and intuitive control methods.
  • A door with insulation and a magnetic gasket seal.
  • LED lighting that conserves energy and has a longer lifespan than fluorescent lighting.

Parts/Components of Laboratory Refrigerators and Freezers

Parts/Components of Laboratory Refrigerators and Freezers
Parts/Components of Laboratory Refrigerators and Freezers | Image Source: scienceabc.

1. Refrigerant

Refrigerators cannot function without refrigerant. It begins as a gas, becomes a liquid, and then returns to a gas as it cycles through the refrigerator’s components. This is the technique by which the refrigerator gets cooled. As refrigerants in the early stages of refrigerator technology, hazardous gases such as ammonia were utilised. In the 1930s, producers began employing freon as an alternative. Freon was utilised for decades until current scientific discoveries revealed it to be hazardous to the Earth’s ecosystem. The majority of new refrigerators currently utilise HFC 134a.

Parts/Components of Laboratory Refrigerators and Freezers
Parts/Components of Laboratory Refrigerators and Freezers

2. Compressor

The compressor initiates the chilling process in a refrigerator. A motor drives the compressor, which boosts the gas’s temperature and pressure before sending it to the condenser. The compressor is normally located towards the back, bottom edge of the refrigerator. Built-in refrigerators, however, typically position the compressor(s) on top.

3. Condenser

In the condenser, the refrigerant becomes liquid. In the condenser, heated vapours are condensed into a liquid. It is distinguished by its massive copper coils, which can be found along the unit’s bottom or rear.

Parts/Components of Laboratory Refrigerators and Freezers
Parts/Components of Laboratory Refrigerators and Freezers

4. Expansion Valve (Or Capillary Tube)

This cooling procedure is then transferred to the expansion valve, which consists of a thin series of copper tubes. The expansion valve drastically reduces the temperature and pressure of the liquid refrigerant, causing approximately half of it to evaporate. This refrigerant’s repeated evaporation at extremely low temperatures is what keeps your refrigerator and/or freezer cool.

5. Evaporator

The evaporator is where the cooling process concludes and the next cycle begins. It transforms the remaining refrigerant liquid into vapour, which the compressor uses to restart the refrigeration cycle.

6. Other Parts

  1. Thermistor: It monitors the refrigerator’s inside temperature.
  2. Evaporator Fan Motor: The evaporator fan motor drives the fan that distributes cold air throughout the freezer and refrigerator compartments.
  3. Condenser Fan Motor: Fans are utilised to push air through condenser coils in refrigerators with compressor compartment mountings in order to cool the refrigerator and dissipate heat.
  4. Water Inlet Valve: It generates sufficient water pressure to open the valve and dispense water into the ice tray in order to produce ice.
  5. Water Filter: A clogged water filter prevents water from reaching the ice maker, hence inhibiting the production of ice.

Types of Laboratory Refrigerators

There are four types of refrigerators used in laboratories.

Types of Laboratory Refrigerators
Types of Laboratory Refrigerators
  1. Explosion proof refrigerators: Explosion-proof freezers are designed to store combustible liquids and hazardous chemicals. The lack of electrical equipment in the storage space eliminates fires produced by sparks, making it safe for use with combustible items.
  2. Lab fridges: Lab refrigerators are designed to maintain stable temperatures and feature digital displays for monitoring the temperatures. General laboratory refrigerators must include lockable, easy-to-clean compartments. Additionally, they are utilised to cool samples and preserve them.
  3. Refrigerators for blood banks: Blood bank refrigerators adhere to all American and European laws. Along with temperature monitoring, dependability is essential for this type. In addition, they must have distinct chambers for storing various sample kinds.
  4. Refrigerators for chromatography: Refrigerators for chromatography are developed for scientific experiments. They are most commonly utilised in laboratories where exact temperature settings and stability are required for medical samples and operations. For example, a chromatography equipment can be assembled within the refrigerator chamber of a laboratory refrigerator. See image on the right for an illustration.

Types of Lab Freezers

1. Ultra-Low Temperature Freezers

  • If your laboratory handles components that demand a cold environment, you must obtain ultra-low temperature freezers. This enables the storage of such materials at temperatures below -40 degrees Celsius.
  • Some ultra-low freezers are capable of reaching temperatures as low as -86°C thanks to two independent evaporator circuits that surround the internal chamber.
  • Additionally, you should be aware that ultra-low freezers often require a considerable amount of electricity to sustain the lowest temperatures.
  • Utilization recommendation: ultra-low temperature freezers are good for storing materials requiring low temperatures in laboratories and medical facilities.

2. Chest Freezers

  • The availability of sufficient storage space is a priority for several laboratories and medical institutes. The chest freezer is a huge piece of equipment that opens from the top as opposed to the front.
  • As is the case with the majority of laboratory refrigerators, chest freezers are equipped with alarm systems that provide lock and temperature change notifications and display digital temperature readings.
  • Chest freezers are not equipped with shelves. If your laboratory demands a high level of storage organisation, it would be unwise to choose chest freezers.
  • Utilization Recommendation: Laboratories that must store large things in a single unit should invest in chest freezers, as they are optimal for this purpose.

3. Under-Counter Freezers

  • Under-counter freezers come in a variety of configurations, including general-purpose, explosion-proof, and flammable material storage.
  • In addition to allowing you to select the appropriate size and temperature range, under-counter freezers also feature levelling feet.
  • In addition, under-counter freezers are ventilated with forced air, and you do not need additional clearance space if you choose the general-purpose type.
  • There are also provisions for adjusting the defrost frequency, indicating that you should not anticipate accidental thaws and dehydration of samples.
  • Use recommended: The ability to conserve space is one of the most major benefits of under-counter freezers, since they fit snugly beneath lab benches and countertops. If minimising space is a priority in your laboratory or medical institution, then under-counter freezers are appropriate.

4. Upright Freezers

  • In numerous laboratories and medical institutes, upright freezers are arguably the most prevalent type.
  • Because these freezers open from the front, they resemble conventional household freezers used to store groceries.
  • There are a variety of sizes of upright freezers, ranging from small counter-top models to big models for holding vast volumes of laboratory samples.
  • Typically, upright freezers include inside shelving units, allowing you to optimise space and organise samples without difficulty.
  • In addition to their organisational qualities, upright freezers are popular in the medical industry due to their space efficiency.
  • In contrast, because to their vertical shape, upright freezers do not require a great deal of floor area, however they can store the greatest quantity of items.
  • Use upright freezers if you require a freezer that maximises temperature consistency to ensure that all laboratory samples are exposed to the same conditions. Additionally, this reduces the recovery period after opening the freezer door.

How does a refrigerator work?

The operation of a refrigerator consists of the following steps:

  1. The compressor is responsible for compressing the refrigerant gas. As the gas is compressed, it generates heat.
  2. The coils on the rear of the refrigerator diffuse the heat of the heated refrigerant gas. At high pressure, the refrigerant gas condenses into a liquid.
  3. The liquid under high pressure flows through the expansion valve.
  4. The liquid instantly boils and vaporises, causing its temperature to drop to approximately -25°F. As the cold gas passes through the expansion coils (inside the refrigerator), it absorbs heat to cool the interior.
  5. The compressor draws in low-pressure refrigerant gas, and the cycle continues.

The essential component of the refrigerator, the compressor, compresses the refrigerant gas. As the gas is subjected to high pressure, it heats up. Now, this gas travels to the condenser coils (thin radiator pipes) in the back of the refrigerator, where the coils assist disperse its heat so that it gets cool enough to condense and transform back into its liquid phase.

As a result of the condenser releasing the food’s heat into the environment, the condenser feels warm to the touch.

The liquid currently under high pressure flows via the expansion valve. Consider the expansion valve a tiny hole. On one side of the opening is liquid refrigerant under high pressure. On the opposite side of the hole is a region of low pressure (because the compressor is sucking gas out of that side).

After passing through the expansion valve, the pressure of the liquid decreases. As a result, it becomes a gas with a temperature of -25°F.

When this cool gas runs through the expansion coils (which are positioned within the refrigerator), it absorbs heat and thus cools the interior of the refrigerator.

This low-pressure refrigerant gas is again pulled in by the compressor, and the entire cycle continues, ensuring that the refrigerator’s contents remain continuously cool.

Safe Laboratory Refrigerator/Freezer Operating Procedures

  1. Never keep combustible substances with a flash point below 37.8°C (100°F) in a household (domestic) refrigerator.
  2. Never store food or beverages intended for human consumption in a refrigerator or freezer used in a laboratory.
  3. Ensure that all of the chemicals in the refrigerator are suitable. Guidelines for Chemical Storage
  4. All containers placed in a refrigerator or freezer must be thoroughly sealed or capped, as well as firmly positioned. No aluminium foil, corks, or uncoated glass stoppers should be used to seal containers.
  5. Refrigerator shelves should be outfitted with adequate plastic trays for secondary food containment in the refrigerator and freezer. If plastic trays are unavailable, liquid chemicals must be placed in secondary containers to contain spills.
  6. All objects stored in a refrigerator must bear the proper labels. View Requirements for Chemical Labeling
  7. Only store chemicals in the quantities required for a fair duration. If refrigerated substances are not properly stored and sealed, they may be highly susceptible to disintegration.
  8. Keep in mind that power interruptions and technological malfunctions might cause interior temperatures to rise, which can have a negative impact on chemical contents. When you open the refrigerator, be aware of any strange odours, fumes, etc.
  9. Units must be permanently placed and grounded; extension cords are prohibited.
  10. Refrigerators and freezers should be emptied and manually defrosted at least annually, if not more frequently as needed.

Guidelines on use of laboratory refrigerator

  • There should be no exposed samples or reference materials; instead, they should be stored in plastic pouches or standard vials. This is necessary to prevent cross-contamination resulting from closeness to other samples.
  • Light-sensitive samples must be stored in amber or dark-colored vials.
  • Labels should be carefully fastened and covered with a transparent film so that moisture condensation does not render them illegible.
  • Chemicals, standards, foods, and pharmaceuticals should be stored in temperature zones that correspond to their storage requirements. Do not succumb to the temptation to place the sample wherever, as this will not serve the intended goal.
  • It is recommended to name the cabinets and maintain a current list of sample locations, which should be updated using user records. Additionally, this will save precious time in locating samples and standards as required.
  • At least weekly, clean the cabinets and shelves only after turning off the electricity.

Calibration of Laboratory Refrigerators and Freezers

  • As with any other scientific device, laboratory refrigerators require regular calibration and the maintenance of calibration records, unlike domestic refrigerators.
  • A calibrated thermometer is placed in a beaker with silicone oil in several drawers and the freezer. After 15 minutes of stabilisation with the door closed, temperature readings are taken. The temperature range for cabinets should be between 2 and 8 degrees Celsius, while the temperature range for the freezer should be between -10 and -20 degrees Celsius.
  • A well-maintained and calibrated refrigerator will aid in the preservation of samples and standards over longer time periods. Never use a laboratory refrigerator to keep food and beverages, as unintentional contamination from stored chemicals might have severe effects.

Uses of Laboratory Refrigerators and Freezers

  • Anti-frost blowers in laboratory refrigeration units keep moisture levels low, providing for a drier environment for moisture-sensitive dried reagents and materials.
  • Refrigerators allow for the preservation of samples, specimens, vaccinations, and medications at a specified temperature to prevent their spoilage, whereas freezers accurately freeze rather than cool goods.
  • It preserves the stability of reagents used for the chemistry analysis by providing a precise temperature control system during refrigeration.
  • It includes measures for climate control that preserve the quality of microbiological medium.

Advantages of Laboratory Refrigerators and Freezers

  • Freezers are crucial for establishing a secure cold chain, which is necessary for the complete preservation of biological materials used in medical procedures including blood transfusions, vaccines, and other therapies.
  • In this way, biological materials and vaccines can be kept in a stable environment thanks to proper monitoring and alarming of temperature changes.
  • Strong air circulation systems with air cooling vents in refrigerators and freezers help encourage greater airflow (ventilation).
  • Intentionally constructed freezers and fridges may be secured with digital locks, allowing only authorised employees access.
  • There are further advantages to using backup battery sources in the machine during temperature excursions caused by power interruptions.
  • It’s used to stop or prevent biological contamination in research facilities.

Limitations of Laboratory Refrigerators and Freezers

  • Risks associated with the use of refrigerators and freezers in laboratories include chemical incompatibility, inadvertent release of gases from the contents, and the possibility of spillage or gas emission.
  • It’s more expensive to run, fix, and fuel.
  • Due to the refrigerant, such as CFCs that contribute to ozone layer depletion, they constitute a threat to the environment if not disposed of properly.

Laboratory Refrigerators and Freezers Examples and Buy

Thermo Scientific MR45SS-GARE-TS Series GP Laboratory Upright Refrigerator

  • Exceptional security features
  • Outstanding temperature stability
  • Intuitive digital controls
  • Quality, robust construction

NOR-LAKE LR161WWW/0 General Purpose Laboratory Refrigerator, Upright Auto Defrost

  • Dimensions are 67-1/2″ H x 34 W x 30-1/4 D
  • Package Quantity: 1
  • Product Type: Lab Supply
  • Country Of Origin: United States

American BioTech Supply ABT-HC-UCFS-0104G Premier Undercounter Refrigerator

  • Exterior color: White
  • Refrigerant: R600a
  • Defrost: cycle
  • UL/c-ul Listed
  • Digital temperature display

HNZXIB 80L (2.7Cu Ft) Vertical Ultra-Low Temperature Freezer

  • SUS304 interior, healthy and good looking, easy cleaning; Double door gaskets provide good seal
  • Unique patented technology for auto cascade single-stage compression refrigeration system and a recipe for mixed CFC-free refrigerants
  • Superior performance: strong and quick cooling, the lower final temperature
  • World-famous brand thermostat: Italian Dixell temperature controller, high control accuracy, digital temperature display, Hi/Low temperature & sensor fault alarms, easy operation
  • EBM condenser fan motor: strong and reliable, low failure rate, long working life.Low noise

HNZXIB -86° C Horizontal Ultra-low Temperature Laboratory Freezer

  • Intelligent computer configuration makes temperature control more accurate. Microcomputer digital control, real-time temperature display, adjustment unit is 0.1℃.
  • Humanized design, easy to use. The internal controls and temperature indicating devices of the refrigerator are installed on the front of the refrigerator, which is convenient and quick to use, and has a beautiful appearance.
  • Equipped with an intelligent alarm system. Complete alarm system (over-temperature alarm system failure alarm) and temperature recording system (optional) to ensure the safe storage of items in the refrigerator.
  • The ultra-thick environmentally-friendly insulation layer effectively reduces heat loss, saves energy and prolongs service life,The inner cavity of the box is made of stainless steel, and the tubular copper tube evaporator is easy to fetch, the heat dissipation effect is good, and the inner tank is easy to clean.
  • We use express delivery. Wooden packing. 7-10 days to arrived

References

  • https://pdf.indiamart.com/impdf/15406183033/MY-2305501/thermo-scientific-tsx-series-high-performance-undercounter-lab-refrigerator.pdf
  • https://www.escolifesciences.com/products/lab-refrigerators-and-freezers
  • https://www.thermofisher.com/in/en/home/life-science/lab-equipment/cold-storage/lab-refrigerators.html
  • https://www.laboratory-equipment.com/refrigerators-and-freezers.php
  • https://www.coolmed.co.uk/knowledge/news/what-is-a-laboratory-fridge/
  • https://www.biomall.in/category/lab-refrigerators-and-freezers
  • https://ehs.oregonstate.edu/sites/ehs.oregonstate.edu/files/pdf/si/labrefrigerators_si.pdf
  • https://www.globalspec.com/learnmore/labware_scientific_instruments/thermal_processing/laboratory_freezers_refrigerators
  • https://americanbiotechsupply.com/blogs/american-biotech-supply/2020/10/08/types-of-lab-freezers-qualities-and-recommended-use
  • https://lab-training.com/how-a-laboratory-refrigerator-is-different-from-a-household-refrigerator/
  • https://medium.com/@ramilabworld/how-laboratory-refrigerators-and-freezers-are-used-in-the-lab-59ac561f8205
  • https://medium.com/@ramilabworld/the-many-uses-of-the-laboratory-refrigerator-cd179e7233c3
  • https://microbenotes.com/laboratory-refrigerators-freezers/#references
  • https://ezinearticles.com/?The-Many-Uses-of-the-Laboratory-Refrigerator&id=3425642
  • https://www.danfoss.com/en/about-danfoss/our-businesses/cooling/the-fridge-how-it-works/
  • https://byjus.com/question-answer/what-is-the-principle-of-freezing/
  • https://www.tampaapplianceparts.com/blog/what-are-the-main-working-parts-of-a-refrigerator/
  • https://microbenotes.com/laboratory-refrigerators-freezers/#references
  • https://www.scienceabc.com/innovation/how-does-a-refrigerator-work-working-principle.html
  • https://www.newfane.wnyric.org/cms/lib/NY01001283/Centricity/Domain/95/How%20a%20Refrigerator%20Works.pdf

Citation

APA

MN Editors. (December 16, 2022).Laboratory Refrigerators and Freezers – Principle, Parts, Applications. Retrieved from https://microbiologynote.com/laboratory-refrigerators-and-freezers/

MLA

MN Editors. "Laboratory Refrigerators and Freezers – Principle, Parts, Applications." Microbiology Note, Microbiologynote.com, December 16, 2022.

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