Compressors are an essential component of refrigeration systems used in cold storages. They compress refrigerant gas to increase its pressure and temperature, allowing it to release heat in the condenser and absorb heat in the evaporator. There are several types of compressors used in cold storage refrigeration, each with its advantages and disadvantages. In this article, we will discuss the types of compressors used in cold storage refrigeration and their characteristics.
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1. Reciprocating Compressors
Reciprocating compressors are the most common type of compressor used in cold storage refrigeration. They use pistons to compress refrigerant gas and are available in single or multiple stages. Single-stage compressors are suitable for small to medium-sized cold storage facilities, while multiple-stage compressors are ideal for larger facilities that require higher cooling capacities. Reciprocating compressors are reliable, efficient, and have a long service life, making them a popular choice for cold storage refrigeration.
2. Rotary Compressors
Rotary compressors use rotary blades to compress refrigerant gas and are available in two types: vane and screw compressors. Vane compressors use vanes that slide in and out of a rotor to compress the gas, while screw compressors use two interlocking rotors to compress the gas. Rotary compressors are compact, energy-efficient, and have a low noise level, making them suitable for small to medium-sized cold storage facilities.
3. Scroll Compressors
Scroll compressors use two spiral-shaped scrolls to compress refrigerant gas, creating a continuous flow of gas that reduces vibration and noise. They are available in single or multiple stages and have a high energy efficiency rating, making them suitable for small to medium-sized cold storage facilities. Scroll compressors have a low noise level, making them suitable for noise-sensitive environments such as hospitals and laboratories.
4. Centrifugal Compressors
Centrifugal compressors use a high-speed impeller to compress refrigerant gas, creating a centrifugal force that increases the gas's pressure and temperature. They are suitable for large cold storage facilities that require high cooling capacities and are available in single or multiple stages. Centrifugal compressors are energy-efficient and have a long service life, but they require more maintenance than other types of compressors.
5. Screw Compressors
Screw compressors use two interlocking screws to compress refrigerant gas, creating a continuous flow of gas that reduces vibration and noise. They are available in single or multiple stages and are suitable for small to medium-sized cold storage facilities. Screw compressors are energy-efficient and have a low noise level, making them suitable for noise-sensitive environments such as hospitals and laboratories.
Conclusion
The type of compressor used in cold storage refrigeration depends on the facility's size, cooling capacity, and environmental factors. Reciprocating compressors are the most common type of compressor used in cold storage refrigeration, while rotary, scroll, centrifugal, and screw compressors are suitable for specific applications. Understanding the characteristics of each type of compressor is essential to select the appropriate compressor for the cold storage facility, ensuring efficient and reliable operation.
Introduction
In the era of global trade, cold room has become increasingly important due to its role in improving the efficiency of transporting goods worldwide. Whether youre a learner or an Expert, this article will give you a comprehensive understanding of cold room. So, if youre curious about how cold storage works, keep reading!
What Is Cold Room?
Cold Room is also called Cold Storage.A cold room is a sealed and insulated space where storage temperatures for goods are controlled and regulated using refrigeration technology based on local climatic conditions.
The function of a Cold Room
The function of a cold room is to keep goods at their ideal temperature and humidity, ensuring they stay fresh for as long as possible and maximizing their shelf life.
8 Major Industries Applications
Cold storage is widely used in modern production and daily life. You can see the application of cold storage in the following industries:
Agriculture Industry
Cold storage technology can help extend the shelf life of fresh fruits, vegetables, and nuts, preserving their freshness. Storing seeds in a cold environment can prevent them from getting damp and moldy, maintaining their quality. Storing flowers and seedlings in cold storage can prolong the shelf life of flowers during transportation and improve the survival rate of precious seedlings.
Food Retail Industry
Retail foods like ice cream, dairy products, and poultry require specific temperature and humidity conditions for storage. Cold storage technology is used to distribute and retail these products, extending their market reach while preserving their nutritional value and taste.
Pharmaceutical and Medical Industry
With advancements in the pharmaceutical industry, the manufacturing and storage conditions of medicines require precise temperature and humidity control. The demand for cold storage in the pharmaceutical industry continues to increase. Additionally, in the field of bio-medicine, such as the storage and testing of blood samples and organ transplants, cold storage technology enables the safe transportation of these samples over long distances, contributing to life-saving efforts.
Brewery Industry
The brewing process for beer and wine requires refrigeration as they need to undergo fermentation at different temperatures. Stable temperature conditions are essential for long-term storage and taste preservation of alcoholic beverages.
Chemical Industry
The storage and protection of chemical substances increasingly rely on cold storage technology. Cold storage applications are seen in storing chemical reagents, temperature-sensitive materials, stability testing of chemical formulations and products, and storage of hazardous chemicals.
Hospitality Industry
Cold storage plays a crucial role in the hospitality industry, including the storage of ingredients and ingredients such as meat, vegetables, fruits, dairy products, and the production and display of low-temperature dining products such as ice cream, as well as the reserve of juices and beverages.
Fishing Industry
Cold storage is essential for storing fish during deep-sea fishing operations and for ice-fresh or frozen processing of various fish species in seafood processing and sales, ensuring quality and freshness.
Cold Chain Logistics Industry
The use of refrigerated vehicles and refrigerated containers provides temperature and humidity control throughout the transportation process for various temperature-sensitive products such as food, medicines, chemicals, and flowers, ensuring safety and product quality.
Evolution of Modern Cold Room Technology
In the late 19th and early 20th centuries, American engineer William C. Frick invented the first mechanical refrigeration system using a compressor. This marked the start of modern refrigeration technology. Over 100 years, cold storage has advanced with automation and energy-saving techniques. Today, its becoming smarter and controlled through the Internet of Things.
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Classification of Cold Room Types
You can classify cold rooms according to different methods. Here are eight common classification methods for cold rooms:
Classification by Cold Room Volume
- Cold rooms with a nominal volume between 5,000 sqm and 20,000 sqm are defined as medium-sized cold rooms.
- Cold rooms with a nominal volume greater than 20,000 sqm are defined as large-scale cold rooms.
- Cold rooms with a nominal volume less than 5,000 sqm are defined as small-scale cold rooms.
Note: The volume of the cold room should be calculated based on the nominal volume of the refrigerated space, which is obtained by multiplying the net indoor area of the refrigerated space by the net room height.
Classification by Cold Room Internal Design Temperature
- High-temperature cold rooms: -2 to +8 , mainly used for storing fruits and vegetables.
- Medium-temperature cold rooms: -10 to -23, mainly used for refrigerating frozen foods.
- Low-temperature cold rooms: -23 to -30, mainly used for storing frozen seafood and meat products.
- Ultra-low-temperature cold rooms: -30 to -80, mainly used for rapid freezing before refrigeration of fresh products.
Classification by Type of Stored Items
- Fruit and vegetable preservation cold rooms: For storing fruits and vegetables to maintain freshness.
- Meat products cold rooms: For storing various types of meat.
- Seafood and aquatic product cold rooms: For storing marine products such as shellfish, algae, and fish
- Modified atmosphere preservation cold rooms: For storing fruits, vegetables, and other products under modified atmospheric conditions.
- Biomedical cold rooms: For storing vaccines, drugs, blood, bone marrow, and other items.
- Scientific research and chemical cold rooms: For storing flammable and explosive chemical hazardous materials.
Classification by Cooling Method
- Air-cooled cold rooms: Use cold air circulation by cold air fans to lower the temperature inside the room.
- Water-cooled cold rooms: Use a water circulation system to cool the air inside the room.
Classification by Cold Room Function
- Refrigerated storage: For storing products that need to be kept at lower temperatures, such as fresh fruits and vegetables.
- Freezing storage: For storing frozen foods, such as frozen meat and frozen foods.
- High-humidity storage: For storing products that require a high-humidity environment, such as seafood and flowers.
Classification by Cold Room Building Structure
- Stand-alone cold rooms: Cold rooms are standalone buildings separated from other buildings.
- Built-in cold rooms: Cold rooms are integrated into other buildings, such as supermarkets or warehouses.
Classification by Period of Use
- Temporary storage cold rooms: For temporarily storing goods, with products expected to be shipped quickly after a certain period.
- Long-term storage cold rooms: For long-term storage of goods, such as seasonal products or inventory products.
Classification by Special Requirements
- Explosion-proof cold rooms: Cold rooms equipped with explosion-proof safety measures, suitable for storing flammable and explosive materials.
- Corrosion-resistant cold rooms: Using special materials and coatings to prevent corrosion, suitable for storing chemicals.
How Do Cold Rooms Work? Cold Room Working Principal
The operation of a cold storage facility consists of two parts: first, constructing a well-sealed enclosed space using insulated panels. Then, utilizing a refrigeration cycle system composed of a compressor, condenser, expansion valve, and evaporator to cool the goods inside the cold storage and maintain the storage temperature as per the design requirements. Below, we explain the principles of the four basic processes of the refrigeration system in a cold storage:
- Compression process: Low-temperature, low-pressure refrigerant gas is drawn into the compressor, where it is compressed into high-temperature, high-pressure gas. The compression process raises the temperature and pressure of the refrigerant.
- Condensation process: The high-temperature, high-pressure refrigerant gas enters the condenser, where it releases heat through a radiator, cooling the refrigerant and transforming it into high-temperature, high-pressure liquid. The condensation process releases the heat of the refrigerant into the external environment.
- Expansion process: high-temperature and high-pressure refrigerant gas passes through the expansion valve, reduces the pressure, becomes a low-temperature and low-pressure refrigerant gas and liquid mixture, and enters the evaporator.
- Evaporation process: low-temperature and low-pressure refrigerant liquid and gas mixture. Inside the evaporator, the refrigerant quickly evaporates from liquid to gas by reducing pressure. During the evaporation process, it absorbs the heat of the goods stored in the cold storage to achieve a cooling effect. The refrigerant drops from high temperature to low temperature and becomes a low-pressure and low-temperature gas and returns to the compressor.
By continuously repeating these four processes, the refrigeration system of the cold storage facility can continuously transfer the heat inside the cold storage to the external environment, thereby stably maintaining the low temperature inside the cold storage.
4 Main Components of Refrigeration system?
The refrigeration system of a cold storage facility is the core system, consisting of four main components: the compressor, condenser, evaporator, and expansion valve. Heres a detailed explanation of each component:
- Compressor: This is the power source of the refrigeration system, responsible for raising the pressure and temperature of the refrigerant, maintaining system circulation, enhancing cooling efficiency and capacity, and ensuring stable operation. There are various types of compressors commonly used in cold storage, including rotary, scroll compressor, piston compressor, screw compressor, and centrifugal compressors. The selection of compressor types depends on the size of the cold storage and refrigeration capacity requirements, and multiple compressors can be used in parallel operation.
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- Evaporator: The evaporator plays a crucial role in absorbing heat from the cold storage, reducing temperature, and reducing air humidity to improve comfort. Common types of evaporators include unit coolers, bare tube, plate, finned tube, and shell and tube evaporators.
- Condenser: This is an important heat exchanger in the refrigeration system responsible for converting the refrigerant from gas to liquid. It achieves this by transferring heat from the high-pressure, high-temperature refrigerant to the surrounding environment. Common types of condensers include water-cooled, air-cooled, and evaporative condensers.
- Expansion Valve: This is an essential component that regulates pressure, controls refrigerant flow, and prevents issues like liquid hammer and compressor overheating. Common types of expansion valves include thermal, electronic, and automatic expansion valves.
Its important to understand the selection criteria and sequence of these four core components. Based on the design temperature and temperature differential of the cold storage, cooling equipment and mechanical equipment loads are calculated. The evaporator is selected based on the cooling equipment load and its heat transfer capacity, while the expansion valve is chosen accordingly. The compressor is selected based on the mechanical equipment load and its refrigeration capacity, and the condenser is chosen accordingly. This ensures the selection of rational and compatible components for the refrigeration system.
Cold Room Installation, the Installation Procedure
One significant reason for issues in cold storage facilities is improper installation during construction. Therefore, the installation and construction of cold storage are crucial. Heres a checklist of installation steps to ensure your cold storage is properly constructed:
- Material Preparation: Before starting the installation construction of cold storage, all necessary materials must be prepared. These materials include cold storage panels, cold storage doors, compressor refrigeration units, cold air fans, temperature control boxes, expansion valves, copper pipes, electrical control cables, cold storage lights, sealing agents, etc.
- Installation of Cold Storage Panels and Doors: Assembling cold storage panels is the first step in installation. When assembling the cold storage panels, ensure that the ground is level to ensure a tight seal at the top of the cold storage, maintaining good sealing.
- Installation of Cold Air Fans: The installation of cold air fans inside the cold storage should be based on the direction of the cold storage body structure. Ensure that the distance between the cooling fans cooling fan and the cold storage panel is greater than 0.5 meters to maintain good air circulation.
- Installation of Compressor Refrigeration Units: Semi-sealed or fully sealed compressors should be installed with oil separators, and an appropriate amount of machine oil should be added to the oil separators. The bottom of the compressor needs to be installed with shock-absorbing rubber pads and sufficient maintenance space should be reserved.
- Installation of Refrigeration Pipelines: The diameter of the pipeline must be calculated according to the design requirements. Arrange the suction pipes, exhaust pipes, drain pipes, supply pipes, etc., of the refrigeration system according to the design requirements, and ensure proper welding of the pipelines.
- Installation of Electrical Control Systems: The electrical control system of the cold storage includes electrical equipment such as control boxes, electric doors, and interior lighting. Since the interior environment of the cold storage is humid and the surface of the cold storage panels is metal, it is prone to leakage. Therefore, low-voltage equipment, such as lighting fixtures, should be used for electrical appliances inside the cold storage.
- Sealing Testing: After the installation of the cold storage, but before the trial run, there are two important tests:Firstly, you need to perform an air-tightness and water-tightness test on the cold storage, ensuring the stability of temperature, humidity, and air circulation inside the cold storage. Secondly, conduct an air-tightness test on the refrigeration system. After the entire refrigeration system is welded, perform an air-tightness test on the compressor, condenser, evaporator, refrigeration pipelines, etc., using special testing equipment through methods such as nitrogen pressurization or vacuuming. After a successful test, maintain pressure for 24 hours to complete the testing.
- Cold Storage Enters Commissioning Phase.
How to commission your cold Room? Operation Sequence
Once your cold storage unit is installed, if youre unsure how to commission it, the following step-by-step guide will walk you through the process. When commissioning a cold storage unit, its essential to have a professionally trained operator:
- Preliminary Inspection: Ensure that the cold storage unit is properly sealed, the refrigeration system is connected correctly, electrical connections are secure and correct, and safety measures for trial operation are in place.
- Electrical Connection: Check that the power supply voltage is normal, inspect compressor impedance and motor insulation for normalcy, and verify the proper opening and closing of valves in the refrigeration system. Set the target temperature for the cold storage unit.
- Evacuate and Charge Refrigerant: Vacuum the refrigeration system and inject refrigerant into the liquid storage tank. Initially charge 70%-80% and gradually add more during system operation.
- Start the Refrigeration Compressor: Observe if the compressor runs smoothly and check if the evaporator and condenser operate normally.
- Normal Cooling Operation: Monitor the pressure and temperature of various parts of the refrigeration system in the cold storage unit. Pay particular attention to observing frost formation on the condenser and expansion valve, changes in oil level and color in the compressors oil sight glass, and any abnormal noises from the equipment.
- Check Seal and Temperature: Verify the seal integrity of the cold storage unit and check for air leaks in the doors. Use temperature sensors to measure temperatures at different locations inside the cold storage unit. Record and monitor temperature changes to confirm whether the temperature remains within the target range.
- Troubleshooting: Set a trial operation time based on the design requirements of the cold storage unit. Address any faults or anomalies promptly during the trial operation.
- Trial Operation Report: Based on the operation results and data, compile a trial operation report summarizing the evaluation and recommendations for the cold storage equipment and system.
- Following these steps will ensure that your cold storage unit is ready for normal operation and item storage.
Cold Room Common Problems Analysis. Problem Classification
When operating and maintaining a cold storage facility, you may encounter various issues. Here, we summarize several common types of problems in cold storage and provide analysis. You can analyze and inspect equipment failures more targetedly based on the abnormal phenomena observed in the cold storage:
- The first type is inadequate design of the cold storage facility, resulting in the refrigeration system being unable to operate continuously and properly. For example, an unreasonable temperature difference in the design of the cold storage facility can lead to compressor damage due to excessive exhaust temperatures. Additionally, a large temperature difference in design can cause excessive and rapid frosting of the evaporator.
- The second type is poor installation of the cold storage facility, leading to problems during operation. For example, poor sealing during installation can lead to leaks, thereby increasing energy consumption and operating costs of the refrigeration system.
- The third type is improper operation of the cold storage facility, resulting in damage to refrigeration equipment and malfunctions. For example, incorrect operation such as starting the compressor before the evaporator leads to insufficient evaporation of the refrigerant, causing liquid hammer and damaging the compressor.
- The fourth type is wear and failure of refrigeration system components after a certain period of normal operation. For example, consumables such as refrigerants and electronic components in the refrigeration system should be inspected regularly and replaced in a timely manner.
Cold Room Industry Development and Trends
By the end of , the global cold storage market capacity is approximately $120.5 billion and is expected to maintain an annual growth rate of 13.15%. By , the global cold storage market capacity is projected to reach $414.6 billion. The future development of cold storage will exhibit the following main trends:
- Firstly, as emerging markets in Asia, Africa, and Latin America continue to develop economically, there will be a sustained high demand for cold storage globally.
- Secondly, the rapid growth of global trade in food and pharmaceuticals demands better temperature control during transportation. Therefore, mobile cold chain logistics will become a rapidly growing sub-market in cold storage development.
- Thirdly, with continuous improvements in cold storage technology and rising global energy costs, the development of cold storage will pay more attention to energy consumption and move towards greater efficiency and energy conservation.
- Fourthly, with the development of cold chain logistics, cold storage equipment will incorporate more intelligent Internet of Things (IoT) technologies. Utilizing big data and artificial intelligence will enable real-time temperature monitoring and tracking of stored goods in cold storage.
FAQ:
Difference Between Chilling Room and Freezing Room
Their temperatures are different. The chilling room typically ranges from -2°C to 0°C, while the freezing room generally ranges from -23°C to -18°C.
Cold Room Temperature Chart for Typical Foods
The cold rooms storage temperature, relative humidity, and suitable range for storing food.
RoomTemperatureRelative humidityFood typeChilling Room0°C to 4°Cmeat & EggFreezing Room-23°C ~ -18 °C-30°C ~ -23 °Cmeat & VegetableFish & ShrimpChilling Food Storage Room-2°C to 0°C0°C to 2°C+2°C to +4°C+7°C to +13°C+11°C to +16°C80-85%85-90%85-90%85-95%85-90%Fresh EggApplePotatoTomatoBananaFreezing Food Storage Room-20°C to -15°C-25°C to -18°C85-90%90-95%Frozen MeatFrozen Fish
8 Tips for Cold Room Maintenance
As you know, proper maintenance of cold rooms is crucial for their normal operation. Here are 8 handy tips for you:
Tips 1. Regularly check the electrical connections and power voltage of the cold room.
Tips 2. Clean the cold room regularly and check for any ice buildup on the panels.
Tips 3. Monitor the temperature and humidity levels inside the cold room at all times.
Tips 4. Periodically inspect the pipes and valves of the refrigeration system for tightness and refrigerant leaks.
Tips 5. Check the defrosting of the evaporator regularly. Ensure the motors and fans of the cold air unit are properly lubricated.
Tips 6. Regularly inspect the condenser of the compressor unit and promptly remove any scale buildup.
Tips 7. Check the oil level and color of the compressors refrigeration oil regularly, along with the discharge temperature of the compressor.
Tips 8. Keep an eye out for any abnormal vibrations or noises in the refrigeration system, and promptly troubleshoot any issues found.
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