[[TitleIndustry]]

Water chiller applications, characteristics and common faults

Date:Mar 27, 2020

The chiller includes four main components: compressor, evaporator, condenser, and expansion valve, thus achieving the cooling and heating effect of the unit.

Chillers are commonly known as freezers, refrigerators, freezers, freezers, coolers, etc., because they are widely used in various industries, their names are numerous. With the continuous development of the chiller industry, more and more humans are beginning to pay attention to any choice of the chiller industry. It is more and more important for human beings. In terms of product structure, "energy-efficient water-cooled screw units", "water source heat pump units", " "Screw-type heat recovery unit", "High-efficiency heat pump unit", "Screw-type low-temperature refrigeration unit" and other highly competitive product structures. The principle of its nature is a multifunctional machine that removes liquid vapor through compression or heat absorption. Refrigeration cycle. The steam compression chiller includes four main components: a vapor compression refrigeration cycle compressor, an evaporator, a condenser, and some metering devices, thus realizing different refrigerants. Absorption chiller uses water as a refrigerant and relies on the water and lithium bromide solution to achieve a strong affinity for refrigeration effect. Chillers are generally used in air-conditioning units and industrial cooling.


In air conditioning systems, chilled water is usually distributed to heat exchangers or coils in air handling units or other types of terminal equipment for cooling in their respective spaces, and then the cooling water is redistributed back to the condenser to be cooled. In industrial applications, chilled water or other liquid cooling pumps are used in process or laboratory equipment. Industrial chiller is used in various industries to control the cooling of products, mechanisms and factory machinery. Generally speaking, water chiller can be divided into water-cooled and air-cooled according to the form of cooling. Technically, water-cooled energy efficiency is 300 to 500 kcal / h higher than air-cooled. In installation, water-cooling needs to be included in the cooling tower. Air-cooled is removable without additional assistance.

Refrigeration form


The performance forms of chiller can be roughly divided into two types


Air-cooled chiller-features


1. No installation cooling tower, easy to install and easy to move, suitable for occasions where no water supply is needed.


2. Low noise fan motor, excellent cooling and condensing effect, stable throttling mechanism, and excellent anti-rust treatment.


3.Using European and American high-performance compressors, high EER value, low noise and stable operation.


Water-Cooled Chillers-Features


1. Ergonomic panel, fully automatic control, equipped with precision electric temperature controller, can run smoothly for a long time.


2. The use of high-efficiency heat transfer heat exchangers has the advantages of less cooling loss, easy oil return, and no frost cracking of heat transfer tubes.


3. Japan-US imported high-performance compressor with high EER value, low noise and stable operation.

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As shown in the figure, at the beginning, the compressor takes in the low-temperature and low-pressure refrigerant gas after evaporation and refrigeration, and then compresses it into a high-temperature and high-pressure gas and sends it to the condenser. Flow into the thermal expansion valve, throttling into low-temperature and low-pressure wet steam, flow into the shell and tube evaporator, absorb the heat of the frozen water in the evaporator to reduce the water temperature; the evaporated refrigerant is sucked back into the compressor, and repeats The next refrigeration cycle.

Unit characteristics


Air-cooled Screw Chiller-Features


1. The air-cooled condenser is fin type, adopts double oil ripple hydrophilic aluminum platinum, and is manufactured by professional heat exchanger processing equipment. It has the advantages of compact structure, small size, light weight, and high heat exchange efficiency. Low speed large leaf axial fan can effectively reduce the operating noise and reduce the impact on the surrounding environment.


2. The unit control system adopts imported PLC program controller, and the human-machine world is equipped with a large screen touch screen. The interface is simple and elegant, and the operation is intuitive and simple.


3. The unit has reliable safety protection devices, including: high and low voltage protector, exhaust overheat protector, compressor motor overheat protector, overload current protector, antifreeze temperature protector, water flow protector, emergency stop switch, temperature sensing Fusible plugs, safety valves, etc.


Water-cooled screw unit-Features


1. Simple structure, stable heat exchange, lasting efficiency and convenient maintenance


2. The unit control system adopts imported PLC program controller, and the man-machine interface is equipped with a large screen touch screen. The interface is simple and elegant, and the operation is intuitive and simple.


Performance characteristics


Air-cooled low temperature chiller-Features


Low-temperature chiller is a special chiller designed for special low-temperature environments. Its super cooling capacity is used for food preservation in hotels, restaurants, supermarkets and other commercial places, large-scale cold storage meat, seafood rapid freezing, refrigeration, ice-making fields, Food processing freezing / refrigeration, pharmaceutical, chemical and other low temperature environments provide reliable protection.


1. Complete product range, including three series: high temperature (water temperature -5 ℃), medium temperature (water temperature -10 ℃), low temperature (water temperature -15 ℃).


2. The structure is highly optimized. The heat exchanger plate is used to support the body. The structure is simple, compact and practical.


3. A perfect combination of high-quality screw compressors and the highest quality and high-efficiency heat exchangers, with an energy efficiency ratio of up to 4.5.


4. Four-stage or stepless capacity control to precisely match load changes.


Water-cooled low temperature chiller-Features


Water-cooled chiller is small in size and large in cooling capacity. It adopts world-famous imported compressors. It has excellent low-temperature performance, reliability and durability. The product is designed according to industrial application characteristics. It has a built-in low-temperature circulating water pump and stainless steel freezing water tank. The materials are all anti-corrosive materials, which can effectively prevent rust and corrosion. The microcomputer LED quantity controller has temperature display, set temperature, automatic adjustment of frozen water temperature and compressor delay protection function. Select brand-name contactors, relays and other electrical components , Equipped with a complete set of indicators and switches, the operation is clear at a glance, built-in electronic water level indicator and alarm device, low water level automatic alarm, the operator can grasp the water level of the freezing water tank through the control panel, and replenish the water in time. The unique modular design, each The system of each compressor is safe and independent. Even if there is a problem in one system, it will not affect the normal work of other systems.


Water source heat pump hot water unit-features


1. The unit design is reasonable, the structure is compact, the appearance is beautiful, the volume is small, and the floor area is small;


2. Energy saving and environmental protection, while providing customers with industrial cold water, it can also supply a large amount of free sanitary hot water. The cooling of the thermal system is increased, the energy utilization rate is high, and the recovered heat can reach 30-80% of the cooling capacity;


3. Low operating costs, improve unit efficiency, improve working conditions, and save unit operating costs;


4. It is safe and reliable, and the temperature and temperature are relatively constant, making the heat pump unit more reliable and stable, ensuring the efficiency and economy of the system, and no special maintenance or operation is required, and the operation and maintenance costs are minimal;


5. Reliable: stable performance, low noise, long service life, thermal factor collection technology reduces unit load and reduces failure rate.


6. Intelligent control, fully automatic microcomputer control, without manual monitoring, can realize remote or centralized management


Air-cooled heat pump unit-features


High efficiency and energy saving, with a comprehensive energy efficiency ratio of up to 8.0, which can provide cooling, heating, and domestic hot water operating conditions. Automatically switch according to the ambient temperature and hot water demand, making full use of energy.


The investment is profitable, and the cold quantity is recovered when hot water is produced, which can achieve zero cost of refrigeration.


Safe and environmentally friendly, using refrigerant as the medium, non-toxic and non-explosive. It can be connected to the original hot water system. It can also replace high-risk and high-cost boiler systems. It can also be used in conjunction with solar systems to replace electric heating parts.


Fully automatic computer control, no special person monitoring required, can be operated through remote or centralized management system.


Unit type or modular type, assembled structure, slim size, can be flexibly installed on the roof, terrace or machine room.


Air cooler


Chillers are used in air conditioners.


1.Industrial air cooler-characteristics


The industrial air cooler is designed for the cooling process of aluminum-free wave soldering, reflow soldering and other equipment. According to the temperature control temperature, the specifications are divided as follows: 10 degrees or more, 5-10 degrees, 0-5 degrees, -5--15 degrees.


2, central air-conditioning-characteristics


The water-cooled cabinet air conditioner is a new type of central air-conditioning unit. It concentrates the essence of domestic and foreign products. It is manufactured using modern advanced technology. It has excellent quality and beautiful appearance. There are two types of products, (direct-blowing and duct-type). specification


Central air-conditioning host:


1. The water-cooled chiller uses horizontal shell-and-tube condensers and shell-and-tube evaporators. It has the characteristics of simple structure, stable heat exchange, long-lasting efficiency, and convenient maintenance. It has been recognized as the most ideal structure for the central air-conditioning host. composition.


2. The unit control system adopts imported plc controller, and the man-machine interface is equipped with a large screen touch screen. The interface is simple and elegant, and the operation is intuitive and simple.


3. The unit has reliable safety protection devices, including high and low voltage protectors, exhaust overheat protectors, compressor motor overheat protectors, overload current protectors, antifreeze temperature protectors, water flow protector emergency stop switches, and easy temperature sensing. Fuses, safety valves, etc.


Maintenance


Start-up and shutdown sequence of the chiller To ensure the normal operation of the air-conditioning main unit after startup, you must ensure that:


① The condenser dissipates heat well, otherwise the cold-condensation temperature and the corresponding condensing pressure will be too high, causing the high-pressure protection device of the chiller to stop and even cause failure.


② The cold water in the evaporator should be circulated. Otherwise, the cold water temperature will cause the cold water temperature protection device to operate and stop, or the evaporation temperature and the corresponding evaporation pressure will be too low. This will cause the cold water in the evaporator to freeze and damage the equipment. Therefore, the chiller's startup sequence is: (must be strictly observed) Cooling tower fan on-> cooling water pump on-> chiller pump on-> chiller on The chiller shutdown sequence is: (must be strictly followed) Stop-> cooling tower fan stop-> cooling water pump stop-> cold water pump stop.


Precautions


① When shutting down, the chiller should be shut down half an hour before work, and the chiller should be shut down after work, which is conducive to saving energy, while avoiding downtime and protecting the unit.


② Before running the refrigeration cycle, make sure that all the valves of the heating cycle pipeline are closed.


Operating procedures


① Preparations before starting


1) Make sure that the power of the unit and controller is on.


2) Make sure that the cooling tower fan, cooling water pump and cold water pump are turned on.


3) Make sure that the end fan coil units are powered on.


② Start


1) Press the status key on the keyboard, and then switch the unit ON / OFF (on / off) toggle switch below the keyboard to the ON position.


2) The unit will do a self-check. After a few seconds, one compressor will start, and the other compressor will start after the load increases.


3) Once the unit is started, all operations are not automatic. The unit starts and stops automatically according to the change of the cooling load (the temperature of the chilled water supply and return water).


③ Normal operation


1) The unit is running normally, the controller will monitor the oil pressure, motor current and other parameters of the system. Once any problem occurs, the control system will automatically take corresponding measures to protect the unit and display the fault information on the unit screen. (See installation, operation and maintenance manual for details)


2) Every 24 hours operation period, there should be a special person to permanently record the unit's operating conditions at fixed intervals.


④ Stop


1) As long as the unit ON / OFF toggle switch under the keyboard is switched to the off position, the unit can be stopped.


2) To prevent damage, do not turn off the power of the unit even when the unit is stopped.


3. Operation of fan and water pump


① The cooling tower fan, cooling water pump, and cold water pump are all independently controlled. Before starting, make sure that the power supply is normal, there is no reverse phase, and there is no phase loss.


② Before the pump is turned on, make sure that the valves in the pipeline have been opened.


Calculation


How to choose the best industrial chiller for you? In fact, there is a simple selection formula:


Cooling capacity = chilled water flow * 4.187 * temperature difference * coefficient


1. Frozen water flow refers to the cold water flow required by the machine during operation, and the unit needs to be converted into liters / second;


2. Temperature difference refers to the temperature difference between the water entering and leaving the machine;


3.4.187 is quantitative (specific heat capacity of water);


4. When selecting air-cooled chiller, the multiplication factor is 1.3. When selecting water-cooled chiller, the multiplication factor is 1.1.


5. Select the corresponding machine model based on the calculated cooling capacity.


The general habit is to use P to calculate how much the chiller is equipped with, but the most important thing is to know the rated cooling capacity. If the general air-cooled 9.07KW looks like, choose a 3P machine. Therefore, the most important choice of industrial chiller is to find the rated cooling capacity.


Common malfunctions


1. The evaporation pressure is too low:


the reason:


(1) The amount of cold water is insufficient.


(2) Less cooling load.


(3) The orifice plate is malfunctioning (only the evaporation pressure is low).


(4) The heat transfer tube of the evaporator deteriorates the heat transfer due to scale pollution (only the evaporation pressure is too low).


(5) The amount of refrigerant is insufficient (only the evaporation pressure is too low).


Solution:


(1) Check the cold water circuit so that the amount of cold water reaches the rated water volume.


(2) Check the setting temperature of the automatic start-stop device.


(3) Check whether the expansion throttle is unblocked.


(4) Clean the heat transfer tube.


(5) Replenish the refrigerant to the required amount.


2. Condensing pressure is too high:


the reason:


(1) The amount of cold water is insufficient.


(2) The capacity of the cooling tower is reduced.


(3) The temperature of the cold water is too high and the cooling capacity is too large, which increases the load on the condenser.


(4) The presence of air.


(5) The heat transfer of the condenser tube is deteriorated due to pollution from scale and the like.


Approach:


(1) Check the cooling water circuit and adjust to the rated flow.


(2) Check the cooling tower.


(3) Check the expansion throttle, etc., so that the temperature of the cold water approaches the rated temperature as soon as possible.


(4) Exhaust air for exhausting operation. If the exhausting device needs to be operated frequently, you must find out where the air leaks in and eliminate it.


(5) Clean the tube.


3. The oil pressure difference is too low:


the reason:


(1) The oil filter is clogged.


(2) The opening of the oil pressure regulating valve (drain valve) is too large.


(3) The output of the oil pump is reduced.


(4) Bearing wear.


(5) The oil pressure gauge (or sensor) fails.


(6) Too much refrigerant is mixed in the lubricating oil (the oil pressure is too low due to oil foaming at startup).


Approach:


(1) Replace the oil filter element.


(2) Close the small oil pressure regulating valve to increase the oil pressure to the rated oil pressure.


(3) Disintegration inspection.


(4) Replace the bearing after disassembly.


(5) Check the oil pressure gauge, recalibrate the pressure sensor, and replace if necessary.


(6) After the refrigerator is stopped, the oil heater must be turned on to maintain the given oil temperature (confirm whether the oil heater is disconnected and whether the setting value of the oil heater temperature control is correct).


4. Oil temperature is too high:


the reason:


(1) The cooling capacity of the oil cooler is reduced.


(2) The supply amount of the refrigerant for cooling the oil cooler is insufficient due to the clogging of the refrigerant filter screen.


(3) Bearing wear.


Approach:


(1) Adjust the oil temperature regulating valve.


(2) Clean the refrigerant filter screen.


(3) Repair or replace bearings after disassembly.


5. Overload of main motor:


the reason:


(1) The phase voltage of the power supply is unbalanced.


(2) The voltage drop of the power line is large.


(3) The amount of cooling refrigerant supplied to the main motor is insufficient.


Approach:


(1) Take measures to balance the power supply phase voltage.


(2) Take measures to reduce the voltage drop of the power line.


(3) Check the filter of the refrigerant filter and clean the filter; open the refrigerant inlet valve


Reduce energy consumption


First, adjust the operating load ratio


Different load ratios of chiller have an inevitable relationship to energy consumption. During the daily chiller operation, 70% to 80% of the load operation energy consumption is far lower than 100% of the load operation, so the specific requirements of the unit are combined In a given time, the purpose of reducing energy consumption can be achieved by reducing the load ratio of the chiller. As long as the unit cooling power consumption is at a lower level, the energy consumption is greatly reduced at this time.


Second, increase evaporation temperature


In actual use, as long as the chiller evaporation temperature and the condensation temperature are effectively increased, the purpose of improving energy efficiency can be achieved, especially for chiller equipment equipped with a cooling water tower. Using such methods can greatly improve the cooling water tower. The efficiency of the cooling water source reduces the problem of energy loss. According to the introduction of domestic refrigerator manufacturers, increasing the evaporation temperature and reducing the condensation temperature are the most common methods to reduce power loss.


Third, reduce pipeline blockages


If the pipeline is blocked, it will seriously affect the increase of water flow and lead to the increase of energy consumption. In actual use, keeping the pipeline in a clear state by different methods can greatly reduce the excessive consumption of various types of energy. To achieve the purpose of improving the working efficiency of chiller.


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