When purchasing cooling equipment for dairy processing, a stable milk temperature is of vital importance. An inefficient cooling system can lead to bacterial growth, increased energy consumption, and the risk of milk spoilage. This guide explains the working principles of dairy milk chiller systems, helping you optimize cooling performance and reduce operational issues.
What is a Dairy Milk Chiller System?
Definition of a Dairy Milk Chiller System
The dairy milk chiller system is a food-grade refrigeration system specifically designed for the dairy industry. Its main function is to rapidly remove the heat from fresh milk, reducing its temperature from approximately 35°C – 38°C (the temperature during milking) to a safe storage temperature (typically 2°C – 4°C).
Below 4°C, the microbial activity in milk is significantly reduced, so the dairy milk chiller can inhibit bacterial growth and extend the milk shelf life.
Features of Dairy Milk Chiller Systems
Rapid Cooling Performance
The dairy milk chiller system can reduce the milk temperature to around 4°C within a very short period of time, typically designed to meet ISO 5708 cooling performance standards.
Hygienic Construction
- All the dairy milk chiller components in contact with milk are made of food-grade SS304 or SS316L stainless steel. Their surfaces are designed to be smooth, seamless, and corrosion-resistant, ensuring the flavor of the milk.
- The dairy milk chiller is integrated with a Clean-in-Place system. It uses hot water and detergents for automatic circulation rinsing, allowing for disinfection without disassembling the equipment.
Intelligent Temperature Control
- Some advanced dairy milk chillers have up to six levels of capacity adjustment capabilities, which can automatically adjust the cooling intensity according to the speed of milking progress. Therefore, they prevent power waste or localized freezing.
- Dairy milk chiller systems are equipped with a PLC controller, making the temperature control accuracy reach ±0.5°C, effectively preventing excessive or insufficient cooling.
- The storage tank of a dairy milk chiller is equipped with a sanitary-grade stirrer. It stirs the milk to ensure uniform temperature distribution and prevent fat layer separation.
Energy-Efficient
- The Heat Recovery System (RHR) in the dairy milk chiller system can capture the waste heat released during the refrigeration process and use it to preheat the hot water for cleaning. This highly reduces electricity costs.
- Dairy milk chiller systems employ scroll compressors, which have a higher efficiency compared to traditional reciprocating compressors and are quieter when working.
- There is high-density polyurethane foam (PUF) filled between the inner and outer tanks, minimizing heat loss and maintaining stable milk temperature.
Types of Dairy Milk Chiller Systems
Except for the two types of air-cooled chiller and water-cooled chiller, dairy milk chiller systems can be divided into several categories according to different refrigeration principles, heat exchange medium and applications.
Direct Expansion Dairy Milk Chiller System (DX)
In this system, the refrigerant directly evaporates and absorbs heat in the evaporation coil inside the milk storage tank. Its structure is simple, and the initial investment is low, making it suitable for small and medium-sized dairy farms. But if the milk volume is too low, there is a risk of partial freezing.
Indirect/Glycol Dairy Milk Chiller System
In a glycol chiller, the refrigeration unit first cools the secondary coolant (usually a food-grade glycol solution) and then cools the milk through the heat exchanger.
Its temperature control is very accurate, and the coolant can store cold energy, ideal for large dairy factories.
Ice Bank Milk Cooling Systems
Dairy milk chillers with ice bank systems can freeze water and use the ice to cool during the milk collection period. This enables off-peak electricity usage and provides cold capacity reserves, ideal for areas with unstable power supply.
Pre-Cooling Systems
This kind of dairy milk chiller system can cool the milk to around 20°C with groundwater first, which can significantly reduce the load of the subsequent refrigeration units
Some dairy milk chillers can cool the milk to the target temperature (4°C) before entering the storage tank with efficient heat exchangers. This can inhibit bacterial growth efficiently.
Common Problems and Troubleshooting of Dairy Milk Chiller Systems
There are some common problems that may occur during the operation of your dairy milk chiller systems. Knowing these problems and their troubleshooting methods helps you better maintain a well-cooled system for your dairy industry.
Low Cooling Efficiency
Sometimes, your dairy milk chiller cannot cool the milk to the target temperature (4°C) effectively.
The reason may be that your condenser is clogged, the refrigerant is insufficient, or there is an overload.
Troubleshooting
- To avoid clogged condensers, you should clean the fins of the condenser regularly. You can use approved cleaning agents to clean.
- To check if the refrigerant is enough, you can observe the pressure gauge of the refrigeration system. Low pressure means that your refrigerant needs to be replenished.
- You can verify whether the milk pumping speed matches the power of the chiller, avoiding overload.
Milk Icing
If the mixer is broken or the temperature controller has failed, the milk may be frozen.
Troubleshooting
- If there is a milk icing, you can first check if the mixer is working well.
- If the temperature control goes wrong, you can calibrate or replace it.
Failure to Start
If your dairy milk chiller system cannot start, it may be because of an electrical fault like loose wiring, a blown fuse, or a tripped circuit breaker. Or because your chiller triggers a safety protection, which can be high-voltage protection due to poor heat dissipation or low-voltage protection due to severe refrigerant leakage.
Troubleshooting
- To troubleshoot the electrical fault, you can check the status of circuit breakers and fuses in the distribution panel.
- You can check the error codes on the control panel and determine the protection type according to the manual.
Excessive Bacterial Count
If the cleaning system fails (which may be because of Insufficient cleaning water temperature, insufficient detergent concentration, or clogged spray balls) or the cooling rate is too slow, bacteria will grow quickly.
Troubleshooting
- You can check the maximum water temperature of the CIP and the level of the chemical agents to ensure they are all proper.
- You can check if there is any scaling in the heat exchanger, and keep it clean.
Abnormal Noise or Vibration
Aging parts of compressors or liquid impact can cause abnormal noise, and damaged fan blades of the condenser or loose bolts can also make noise or vibration.
Troubleshooting
If the compressor makes a metallic knocking sound, you must immediately shut it down to prevent the system from burning out.
Applications of Dairy Milk Chiller Systems
Raw Milk Collection
In milk farms, dairy milk chiller systems rapidly reduce the fresh milk from 35°C – 38°C to below 4°C. Then the milk should be stored at this low temperature for 48 hours.
Scattered small farms always use dairy milk water chillers to centrally process the raw milk delivered by each farmer. They pre-cool and store the milk before transporting it to the large processing plant.
Post-Pasteurization Cooling
The dairy milk chiller system is important for the rapid cooling after pasteurization or ultra-high temperature sterilization (UHT). They ensure its freshness and prevent the reactivation of heat-resistant bacteria. Then the system continuously provides cooling to the plate heat exchangers, ensuring stable operation.
Value-added Dairy Products
Except for ensuring the quality of milk itself, the dairy milk chiller system is also used for making lots of value-added milk products.
For example, when making yogurt, you need a dairy milk chiller to rapidly lower the temperature to stop the fermentation process after yogurt fermentation is completed, thus preventing excessive acidity.
When producing cheese, a dairy milk chiller system is vital in controlling the milk temperature during the whey separation and curd formation process.
When making ice cream, you can use a dairy milk chiller to maintain a lower temperature for the maturation process of the frozen mixture.
Environmental Temperature Control
In some high-end dairy product packaging rooms, dairy milk chillers are used to control the environmental temperature to meet the standards of food clean rooms.
Cold Chain Logistics
At large dairy transfer stations, you can use dairy milk chiller systems to keep the ideal milk temperature before it is loaded into refrigerated trucks.
Institutional Applications
For some institutions that have a daily demand for large quantities of bulk milk, such as large hotels, restaurants, and school cafeterias, installing small dairy milk chiller systems can ensure the safety of milk usage.
Dairy Milk Chiller Size Choosing Guide
Choosing a suitable dairy milk chiller system is very important for ensuring the stability of your milk industry. When selecting, you can take the following factors into consideration:
Cooling Capacity
First and foremost, you must calculate the suitable chiller cooling capacity.
The formula is: Cooling Capacity (kW) = Flow rate (L/s) × 4.186 × Temperature difference (ΔT). And do not forget to add a safety margin in the final.
Generally, for medium and small-sized dairy farms (2,000–10,000L/day), the chiller cooling capacity is about 5RT-20RT (approximately 18–70kW); For large processing plants (50,000L+/day), a chiller with a capacity of over 80RT is usually required.
Cooling Type
We have proposed several dairy milk chiller types in the above part, each of which has its own advantages and suitable applications. You need to choose the most suitable type according to your working conditions. For example, if your factories are in areas with unstable electricity or tiered electricity rates, you can choose dairy milk chillers with the ice bank system.
Technical Features
The parts that are in contact with milk must be made of SS304 or SS316L stainless steel. Besides the material, some technical features are also important for achieving a higher efficiency.
You can choose dairy milk chillers with inverter compressors or scroll compressors to save energy consumption. The heat recovery device is effective in reducing the cost of water heating.
How does a Dairy Milk Chiller System Work?
Components of a Dairy Milk Chiller System
To learn how a dairy milk chiller system works, first you should know its structure and components.
To complete the refrigeration cycle, there are four main components, including the compressor, condenser, expansion valve, and evaporator.
In the heat exchange system, the plate heat exchanger (PHE) enables milk and coolant flows in opposite directions on both sides of the plate to achieve cooling. The water pump is used to circulate the coolant between the chiller and the heat exchanger. And the pre-coolers use well water for initial cooling before the milk enters the main cooling system.
For storage and agitation, there are a bulk milk tank, an agitator, and CIP spray balls.
There are temperature sensors to monitor the milk temperature in real time. In addition, a dairy milk chiller is always equipped with a control panel for monitoring temperature, pressure, and operating status, and automatically starts and stops the compressor and agitator. You can also add the heat recovery device (RHR) as needed.
Working Principle of a Dairy Milk Chiller System
Generally, the working process of a dairy milk chiller system can be divided into two sections, the refrigerant cycle and milk cooling, which operate at the same time.
The Refrigerant Cycle
The refrigerant cycle relies on the refrigerant to absorb and release heat. It can be divided into four parts: evaporation, compression, condensation, and expansion.
Evaporation
The low-temperature and low-pressure liquid refrigerant enters the evaporator. It absorbs heat from the milk, and then the liquid refrigerant boils and evaporates into a gas.
Compression
The compressor sucks in the low-temperature and low-pressure gas and compresses it into high-temperature and high-pressure gas.
Condensation
The high-temperature gas passes through the condenser and releases heat to the ambient air or water. So the refrigerant returns to a liquid.
Expansion
The high-pressure liquid passes through the expansion valve and drops in pressure. Its temperature also drops. Finally, the refrigerant re-enters the evaporator for the next cycle.
Milk Cooling and Processing
Pre-filtering
The fresh raw milk is first filtered to remove impurities and then enters the storage tank or plate heat exchanger.
Heat Exchange
For a direct expansion chiller, milk directly comes into contact with the cooling wall of the storage tank for cooling.
Other types are indirect cooling. The dairy milk chiller first cools the glycerol solution and then absorbs the heat from the milk through the plate heat exchanger.
Agitation
The agitator rotates at a constant speed, ensuring that the milk comes into sufficient contact with the cooling surface. This can prevent local freezing and maintain uniform temperature.
Constant Temperature Storage
When the set temperature is reached, the temperature control system keeps the milk at this low temperature until it is transported.
FAQ
What are the Food-Grade Requirements for Dairy Milk Chillers?
The dairy milk chiller system must comply with strict food-grade requirements. For material, it must be made of AISI 304 or 316L stainless steel, and the surface roughness should be Ra ≤ 0.8 μm without any dead ends. The storage tanks and pipelines must be tightly sealed, and the sealing material should also use food-grade elastomers such as EPDM, silicone, or Viton. If the system uses a secondary coolant, it must be a food-grade propylene glycol.
How Efficient Dairy Milk Chillers Reduce Operational Costs?
In general, dairy milk chillers can highly reduce operational costs by using pre-cooling technology, RHR, VSD/VFD, scroll compressor, and advanced monitors.
Can One Dairy Milk Chiller Cool Multiple Bulk Storage Tanks?
Yes. In a centralized cooling system, the dairy milk chiller system can transfer cooling energy generated by a central chiller to different storage tanks with a distribution manifold. Your chiller cools the coolant, and then it is pumped into the plate heat exchangers of each storage tank.
How to Maintain a Dairy Milk Chiller System?
We recommend that you check the control panel and record the inlet and outlet temperatures of the refrigeration system every day. After milking, you need to clean and disinfect the tank and pipelines.
You can check and maintain some components monthly or quarterly, such as the condenser, the CIP system, the sealing components, and the agitators. And every year, you can ask a professional to verify the refrigeration pressure, expansion valve settings, and overall cooling efficiency.
What are the Advantages of Using Dairy Milk Chiller Systems?
There are lots of advantages to using dairy milk chiller systems. They can inhibit bacterial proliferation effectively and ensure the natural flavor and vitamin components of milk. The “on-demand cooling” function can optimize the milk collection frequency and reduce the transportation cost. Besides, the automatic system reduces the need for manual intervention and ensures the continuous operation of your production line.
Final Thoughts
It’s obvious that a well-designed dairy milk chiller system can reduce your product losses, stabilize storage temperatures, and lower your operating costs. As a profound chiller manufacturer, Chillerone customizes high-performance dairy cooling chiller systems specifically designed for achieving efficient, stable, and long-term operation in demanding dairy application environments. Contact us, and get your tailored milk cooling solutions.
English 
Spanish 
Arabic 
Vietnamese 
