Selection of Industrial Chiller Units

In the production and processing process of the industrial field, due to the needs of the process, chiller units are often used, and these chiller units are generally collectively referred to as "industrial chiller units". For example, in the manufacturing process of some chemical products, the pharmaceutical industry, as well as the supporting equipment of laboratories, the food processing industry, beverage processing plants, etc., when temperature control is required, different models of chiller units need to be selected according to the specific process or operating conditions. When selecting an industrial chiller, it is usually said that "a chiller unit of approximately several horsepower (HP) will do". The "several horsepower" mentioned here refers to the power of the compressor, which is the core component of the chiller unit. Especially for small industrial chiller units, it is customary to calculate using "horsepower" when selecting.

The compressor is the core component of the entire chiller unit device system, also known as the refrigeration main unit, engine head, etc. It is a device used to compress and transport the refrigeration working medium, driven by an electric motor. By compressing the low-pressure superheated refrigerant gas into a high-temperature and high-pressure gas, it enables the refrigerant to continuously circulate in the system, providing power for the refrigeration system to achieve the refrigeration purpose. The power of the compressor determines the refrigeration capacity of the industrial chiller unit. Therefore, calculating the "horsepower" of the industrial chiller is actually calculating the magnitude of the refrigeration capacity required for the system application.

When calculating the refrigeration capacity, first of all, it is necessary to consider which heats need to be taken away by the chiller unit in the specific process application. For example, if it is planned to cool a set of plastic processing molds, it is necessary to consider all the heat generated during the entire processing process. The role of the industrial chiller is to take away the heat transferred to the mold during the processing process to achieve the purpose of cooling the mold. The heat removed from the cooled substance or space per unit time under the specified operating conditions is the refrigeration capacity. Therefore, when calculating the refrigeration capacity, the time factor should be considered, that is, how long it takes to cool to a certain temperature.

Now, the development of many industries has been very mature, and the processing technology process of products is completely standardized. When selecting a chiller unit, there will be corresponding models of industrial chillers to match. However, other factors should also be considered when making the selection, such as the influence of the ambient temperature on the refrigeration capacity of the industrial chiller. For example, the same chiller unit will definitely have different usage effects when used in Hainan and Beijing, and in winter and summer. In addition, in order to ensure the long-term stable operation of the chiller unit, it should maintain a certain working time ratio, rather than allowing it to work under full load for a long time or start and stop too frequently. Therefore, a certain safety factor should be taken into account based on the calculated load to ensure the refrigeration effect.

In addition, the refrigeration capacity of the industrial chiller is related to the type of compressor and the structure of the unit system, and the refrigeration efficiency varies. For example, the refrigeration efficiencies of an air-cooled chiller unit and a water-cooled chiller unit with the same horsepower are different. The refrigeration capacity of a 10HP water-cooled chiller unit under standard operating conditions is approximately around 32KW; while the refrigeration capacity of a 10HP air-cooled chiller unit under standard operating conditions is only approximately around 29KW. In addition, industrial chillers using scroll compressors or screw compressors have higher refrigeration efficiency than piston compressor units.

That is to say, in the case of the same demand for refrigeration capacity, if a water-cooled chiller unit is used, the horsepower of the compressor required will be smaller than that of an air-cooled chiller unit. If a scroll compressor is used, the unit power will be smaller and more energy-efficient than that of a piston compressor. Generally, the refrigeration efficiency of an air-cooled chiller unit is around 2.6, and the refrigeration efficiency of a water-cooled chiller unit is around 3.0. By dividing the refrigeration power by the energy efficiency ratio, you can know the horsepower of the industrial chiller. If the condensation water temperature of the water-cooled chiller unit is below 35 degrees and the ambient temperature of the air-cooled chiller is below 43 degrees, the refrigeration capacity of the air-cooled chiller unit is approximately 0.8 times that of the water-cooled chiller unit with the same power.

When selecting an industrial chiller unit, a safety factor is generally set to ensure that there is sufficient cooling capacity to control the temperature of the application equipment within the required range. However, the horsepower of the chiller unit is not the larger the better. Excessive refrigeration capacity will lead to large initial investment and high energy consumption during use. When calculating the refrigeration capacity of an industrial chiller unit, you can refer to the following formula:

Refrigeration capacity = Chilled water flow × 4.187 × Temperature difference × Coefficient

Among them:
(1) "Chilled water flow" refers to the flow of chilled water required when the machine is working;
(2) "Temperature difference" refers to the temperature difference between the inlet and outlet water of the machine;
(3) "4.187" is the specific heat capacity of water;
(4) When selecting an air-cooled chiller, it is necessary to multiply by a coefficient of 1.3, and when selecting a water-cooled industrial chiller unit, the coefficient is 1.1.

Regarding the matching between the chiller unit and the cooling tower:
Under normal circumstances, a 1HP chiller unit needs to be matched with a cooling tower of 1.2 cooling tons to take away the heat generated by the industrial chiller unit. In some industries, the cooling water required for process cooling can be recycled.

For example, for the chiller unit used in injection molding molds, facilities such as the factory's fire protection water pool can be used. The water from the injection molding mold is transported to the cooling tower for cooling, then flows into the water pool for storage, and is then transported by the water pump to the injection molding machine for cooling again, which can save energy and reduce costs.

Finally, let's introduce several key points of knowledge on the nameplate of the chiller unit.

On the nameplate of the chiller unit, the manufacturer will mark some parameters, mainly including voltage, current, power, temperature, pressure, flow rate, liquid level, concentration, etc., or these parameters will be displayed on the instruments and meters of the unit during operation. Some parameters need to be detected and measured with special instruments and meters during daily inspections.

(1) Voltage: Currently, industrial chillers in China basically use two types of industrial power supplies, 220V (single-phase) and 380V (three-phase). When selecting, it is necessary to ensure that the power supply voltage matches the power consumption voltage of the equipment. Too high or too low voltage will cause the chiller unit to fail to operate or damage the equipment.
(2) Current: The nameplate of the chiller unit generally indicates the rated current and the actual operating current. In addition, it should be noted that components constituting the unit, such as the compressor, water pump, fan, etc., will also have their own nameplates indicating parameters such as the current of the components.
(3) Power: The nameplate will indicate the overall operating power consumption and the rated power of the chiller unit. Sometimes, the power of each component will also be marked on the nameplate.
(4) Temperature: The temperatures of the chiller unit include the evaporator temperature, condensation temperature, compressor suction temperature, compressor discharge temperature, intermediate temperature, the subcooling temperature of the refrigerant before the throttle valve, the temperature of the compressor oil in the crankcase, the cooling water temperature, the chilled water temperature, etc. Most manufacturers will display the cooling water temperature and the chilled water temperature on the control panel or the temperature controller.
(5) Pressure: The pressures of the industrial chiller unit include the evaporation pressure, condensation pressure, intermediate pressure, cooling water pressure, chilled water pressure, lubricating oil pressure, etc. From these parameters, the operating conditions of the system can be judged. For example, when the refrigerant in the refrigeration system is insufficient, the evaporation pressure of the system will become low, triggering a pressure alarm.
(6) Flow rate: The flow rate parameters of the chiller unit include the refrigerant flow rate, cooling water flow rate, chilled water flow rate, etc. By observing the cooling water flow rate and the chilled water flow rate, it can be determined whether the high-pressure alarm of the chiller is caused by insufficient cooling water flow rate when it occurs; the chilled water flow rate can indicate whether the amount of chilled water required for the system application is sufficient.
(7) Liquid level: It refers to the oil level in the crankcase and the refrigerant level. By observing the liquid level mirror, the situation of the lubricating oil or refrigerant in the system can be judged.
(8) Concentration: Generally, it refers to the concentration of the secondary refrigerant, such as the concentration of the ethylene glycol solution, brine solution, etc.
(9) There are also some other common parameters on the nameplate or in the instruction manual, such as the refrigerant model, weight, pipeline interface dimensions (dimensions of the inlet and outlet of chilled water and cooling water, etc.).

Make the correct selection based on the above parameters, and observe, monitor, and control each parameter in a timely manner during operation to make all parameters operate economically and reasonably within the permitted upper and lower limits, so as to achieve the effects of large refrigeration capacity and low energy consumption, and improve the service life of the chiller unit.