ADVICE FOR CHOOSING NEW REFRIGERATION EQUIPMENT
Evaporators (air coolers)
Most often, to reduce equipment costs, the decision is made to choose smaller evaporators that operate at higher temperature differentials (dT). Such evaporators freeze faster because, with too large a dT, a large amount of moisture condenses from the air. Rapid frosting comes with three costly problems: increased electricity consumption, reduced equipment efficiency, and product moisture loss.
Product moisture loss not only reduces product quality but also its weight. As a result, significant money is lost, and it becomes harder to sell the products. Product moisture loss due to poor system performance is unavoidable when freezing and storing berries/mushrooms, and in vegetable storage facilities, attempts are made to solve this problem by installing humidifiers, though often unsuccessfully.
Electricity costs increase when evaporators are improperly selected due to the additional energy required to freeze water and then thaw it. This causes a decrease in equipment performance, as when purchasing refrigeration systems, attention is only paid to the lowest immediate cost, forgetting about the expenses of operating the equipment. We and our clients have repeatedly encountered systems that consume twice as much electricity and fail to achieve the desired results.
Of course, all of this can be avoided with our company's refrigeration solutions. One of them is careful selection of appropriately sized evaporators. According to the European Union standard EN328, the temperature differential (dT) between the evaporator and the supplied air must not exceed 8°C and must be smaller at temperatures below 0°C. For vegetable storage we are manufacturing to meet <=5C differential. The initial investment may be higher, but the additional funds invested pay off much faster, bringing benefits and successful business.
Refrigeration units (machines)
There are various ways to construct multi and single compressor refrigeration units, but we would like to highlight a few of the most popular solutions currently. Knowing that refrigerant prices have increased, the world is trying to find alternatives to this problem. There are several substances: CO2, ammonia, and propane, which are meant to replace refrigerants, but they have significantly more disadvantages than advantages.
CO2 systems are known for operating at low temperatures (down to -20°C and below). These are two-stage systems consisting of a CO2 system operating at low temperatures and a refrigerant/ammonia system operating at high temperatures. A heat exchanger is used for heat transfer between these two systems, which is energy inefficient. Since CO2 pressure in pipes can reach up to 120 bar when the temperature rises to 20°C (which is very dangerous), the CO2 unit must be kept below 0°C to avoid high pressure in the refrigeration system. This necessitates another refrigerant/ammonia refrigeration system to maintain the operating temperature for the CO2 system when it stops. The two-stage system not only becomes very expensive but also particularly dangerous, as working CO2 pressures can reach up to 100 bar.
The efficiency of such CO2 systems is lower, and the cost is higher than that of refrigerant refrigeration systems, for the reasons mentioned earlier. This means that CO2 requires 20-30% higher investments, the building must withstand rapid pressure changes, and maintenance and electricity costs reach about 15-30% more than standard refrigerant refrigeration machines.
Ammonia systems have been used since the late 19th century to this day. These systems are known for their high capacity—more than 100kW. Ammonia, like CO2, causes very little damage to the ozone layer. The efficiency of ammonia compressors themselves is higher than that of refrigerant compressors, but for the entire system to function, it requires pumps and other components that make the ammonia system's efficiency similar to that of refrigerant systems. It should also be noted that ammonia systems are explosive, flammable, and hazardous to human health and products. Therefore, all electrical devices must be hermetic, and buildings must be adapted for explosions. This makes ammonia, like CO2, a very expensive refrigeration solution.
When addressing reliability issues in continuous production, in freezing tunnels, industrial space cooling, or server rooms, it's worth considering dual/triple systems. Instead of one large system, two or more separate systems should be installed. With two independent systems, if one fails, 50% of the capacity remains, which slows down but does not completely stop the space cooling. In higher-capacity redundant systems, refrigerant leakage is minimised, so rapid servicing is not necessary, and maintenance costs are lower.
High-quality assembly of the system is essential in any refrigeration system. Liquid separators, anti-vibration inserts, high/low-pressure protections, and properly assembled piping are necessary. Without proper protections in the system, the risk of damaging the compressor increases, and therefore the system's longevity decreases.
Maintenance and costs
Purchasing a refrigeration system is only one part of costs of system operation. If the initial price is low, often the evaporators are smaller than the required size (are selected to operate at higher temperature differentials), there are no liquid separators, simple automation is installed, etc. As a result, operating costs and electricity consumption increase.
As an example, we can compare a commercial-class evaporator, which is cheaper, and an industrial evaporator that is optimally selected. Requirements for low-temperature refrigeration system: 20kW of cooling at -22°C, dT = 7°K, system operates at 50%. Comparison table with full specifications:
| Parameters | Commercial | Industrial |
|---|---|---|
| Initial cost, € | 6500 | 8800 |
| Capacity, kW | 20.5 | 20.2 |
| Temperature differential (dT), °K | 7 | 7 |
| Fin area, m2 | 133.5 | 170.6 |
| Total fan power, kW | 2040 | 980 |
| Number of defrost heaters, units | 9 | 12 |
| Total defrost power, kW | 16290 | 13136 |
| Moisture condensation, kg/h | 1.8 | 1.8 |
| Annual fan energy consumption, € | 1072 | 515 |
| Investment payback period, years | 4 years 4 months |
The fin area in the evaporator has the greatest impact on its cost. The larger it is, the more efficiently heat is collected. In the commercial evaporator, the fin area is 28% smaller, so to collect 20kW of heat, a fan twice as powerful is required. Over a year, the larger evaporator costs twice as much, so choosing an industrial evaporator leaves you with €500 in savings each year due to cheaper operation. After 4 years, this initial difference between the evaporators evens out and starts to bring you profit. If the system operates for 15 years, there's an opportunity to work at lower costs, making it easier to sell products and earn more.
There are other differences between evaporators as well. The industrial one is made and painted better, manufactured with better quality control, and its defrosting costs are lower. Therefore, in a full system, the difference in initial costs can pay off even faster. For larger factories or farms, daily inspection costs decrease because they simply work. When implementing state projects or purchasing privately, we recommend evaluating all costs and exploring various specifications to choose systems that truly bring profit.
Equipment control systems
The purpose of an industrial controller is to ensure uninterrupted and safe operation under any conditions, even during failures. The controller must also maintain optimal operating conditions and save electricity. We have encountered many different solutions, but we offer only our perfected systems.
The refrigerant quantity is constantly monitored in the system, so we can easily detect potential leaks and inform the user. Our systems have full refrigeration capacity regulation, so the optimal operating mode is automatically selected for each temperature. Defrosting speed and duration are automatically calculated, so the evaporator does not overheat, always fully defrosts, and does not transfer unnecessary heat to the cold room. The user interface is very simple—just enter the desired temperature. The control systems guarantee simple refrigeration equipment maintenance. Faults are precisely indicated, so any company servicing refrigeration equipment can quickly resolve any issues using the necessary materials or tools.
We always plan for our clients to expand, so we've created monitoring systems adapted for large companies, informing about equipment status and helping to monitor the refrigeration process remotely.