An article will take you to have a detailed understanding of the relevant temperature and pressure parameters of the chiller unit

1. Evaporation pressure and temperature
In the operation of a chiller, the evaporation temperature, pressure, and heat brought into the evaporator by cold water are closely related. When the cooling load is high, the return water temperature of the evaporator's cold water increases, causing an increase in the evaporator temperature and corresponding evaporation pressure. On the contrary, when the cooling load decreases, the temperature of the cold water return decreases, and its evaporation temperature and pressure both decrease.

2. Condensation pressure and temperature
In a chiller, the pressure indicated by the high-pressure gauge is called the condensation pressure, and the temperature corresponding to this pressure is called the condensation temperature. The level of condensation temperature, while the evaporation temperature remains constant, has a decisive significance for the power consumption of the unit. As the condensation temperature increases, the power consumption increases. Conversely, as the condensation temperature decreases, the power consumption also decreases.

Therefore, during the operation of the chiller unit, attention should be paid to ensuring that the cooling water temperature, water quantity, water quality and other indicators are within the qualified range. When air is present in the condenser, the temperature difference between the condensation temperature and the outlet of the cooling water increases, while the temperature difference between the inlet and outlet of the cooling water decreases. At this time, the heat transfer effect of the condenser is not good, and the outer part of the condenser feels hot to the touch. In addition, the scaling and sludge on the water side of the condenser tube also play a significant role in heat transfer.

3. Pressure and temperature of cold water
The cold water flow rate of the evaporator is inversely proportional to the temperature difference between the supply and return water, that is, the larger the cold water flow rate, the smaller the temperature difference; On the contrary, the smaller the flow rate, the greater the temperature difference. So, the operating conditions of the chiller set the temperature difference between the cold water supply and return to 5 ℃, which actually regulates the cold water flow rate of the unit. The control of cold water flow is manifested by controlling the pressure drop of cold water through the evaporator. Under standard operating conditions, the cooling water supply and return pressure on the evaporator is set to decrease by 0.5 kgf/cm2. The pressure drop setting method is to adjust the opening of the cold pump outlet valve and the opening of the evaporator supply and return water valves.

4. Pressure and temperature of cooling water
The chiller operates under standard operating conditions, with a condenser return water temperature of 30 ℃ and an outlet temperature of 35 ℃. For operating chillers, environmental conditions, load, and cooling capacity have all become fixed values. At this point, the condensation heat load is undoubtedly also a constant value. The standard stipulates that the temperature difference between the inlet and outlet is 5 ℃, and the cooling water flow rate must also be a certain value. And the flow rate is inversely proportional to the difference in inlet and outlet water temperature. So, when the chiller operates under standard operating conditions, it is sufficient to specify the temperature difference between the inlet and outlet of the cooling water. This flow rate is usually controlled by the pressure drop of the cooling water entering and exiting the condenser.

Under standard operating conditions, the pressure drop of the condenser outlet is set to around 0.75kgf/cm2. The pressure drop setting method also adopts adjusting the opening of the cooling water pump outlet valve and the condenser inlet and outlet water pipe valve. In order to reduce the power consumption of the chiller, the condenser temperature should be minimized as much as possible. There are two feasible measures: one is to reduce the return water temperature of the condenser, and the other is to increase the cooling water volume.

5. Suction temperature of the compressor
The suction temperature of a compressor refers to the temperature of the refrigerant gas in the suction chamber of the compressor. The intake temperature not only affects the exhaust temperature, but also has a significant impact on the volumetric cooling capacity of the compressor. When the suction temperature of the compressor is high, the exhaust temperature is also high, and the specific capacity of the refrigerant when it is sucked in is large. At this time, the refrigeration capacity per unit volume of the compressor is small. On the contrary, when the suction temperature of the compressor is low, its unit volume cooling capacity is large.

6. Compressor discharge temperature
The exhaust temperature is much higher than the condensation temperature, and the direct influencing factor of the exhaust temperature is the suction temperature of the compressor, which is directly proportional to the relationship between the two.

7. Oil pressure difference, oil temperature, and oil level height
The lubricating oil system is an indispensable part of the normal operation of the unit, providing lubrication and cooling conditions for the moving parts of the unit. The oil pressure difference, oil temperature, and oil pressure height of the lubricating oil are the three elements that ensure the lubrication and cooling of moving parts of the unit under normal working conditions.

The function of oil pressure difference is to make lubricating oil flow in the oil system pipeline under the drive of the oil pump, and overcome its flow resistance when transported to various working parts. Without sufficient oil pressure difference, it is impossible to ensure that the system has sufficient lubrication and cooling oil, as well as the power required to drive the energy regulating device.

Oil temperature: refers to the lubricating oil temperature during the operation of the unit. The temperature of the oil has a significant impact on the viscosity of the lubricating oil. A low oil temperature will increase the viscosity of the oil, reduce its fluidity, and make it difficult to form a uniform oil film, which cannot achieve the expected lubrication effect; At the same time, it will also cause a decrease in the flow rate of oil, reducing the amount of lubricating oil and increasing the power consumption of the oil pump.

Oil level height: refers to the height of lubricating oil in the storage container. The oil storage tanks of each unit are equipped with oil level display devices. The general rule is that the oil level inside the oil storage container should be 5mm above and below the central horizontal line of the mirror. The purpose of specifying the oil level height is to ensure that there is sufficient supply of oil circulation to maintain continuous circulation during the operation of the oil pump. Low oil level can easily cause oil pump loss, and even lead to unit operation failure or damage accidents. Therefore, it is necessary to supplement the lubrication system with lubricating oil of the same brand in a timely manner when the oil level is too low, until the oil level in the oil tank reaches the specified height of the sight glass.

8. Unit operating current and voltage
The rated power supply voltage required for general units is 380V, three-phase, 50Hz, and the average phase voltage instability rate of the power supply is less than 2%. The operating voltage of all motors should be within ± 5% of the voltage specified on the compressor nameplate.

Source: Mechanical and Electrical Network