Circulating water mainly includes industrial water and household water, and the main purpose is towater saving。Industrial circulating water is mainly used in cooling water system, so it is also calledCirculating cooling water；Domestic circulating water is mainly used in water heaters.
Chinese name
circulating water
Foreign name
circulating water
Classification
Circulating water mainly includes industrial water and household water
The circulating cooling water is of closed type (closed type) and open type.In the closed cooling water system, the cooling water is not exposed to the air, the water loss is small, and the contents of various minerals and ions in the water generally do not change.In the open circulating water system, the water is re cooled through the cooling tower, so the cooling water must be in contact with the air in the process of recycling, and some water will continue to be lost by evaporation when passing through the cooling towermineralAnd ion content are also continuously concentrated and increased.
The circulating water consists of circulating pump, control system, one-way valve, etc. It forms a complete set of hot water circulating system with water heater, hot water main pipe and hot water return pipe;The working principle is that the control system sends the signal circulating pump, which drives the water to start the water heater for heating in the internal circulation, and stops working when the set time or temperature is reached, and the existing hot water is opened at the hot water use point.[1]
Water is indispensable to human daily life and industrial production.With the development of industrial production, the water consumption is increasing, and many regions have seen the phenomenon of insufficient water supply. Therefore, reasonable and economical water use has become an important issue in the development of industrial production.
Industrial water mainly includes boiler water, process water, cleaning water, cooling watersewageEtc.The largest water consumption is cooling water, accounting for more than 90% of industrial water consumption.Different industrial systems and different uses have different requirements for water quality;However, the requirements for water quality of cooling water used by various industrial departments are basically the same, which makes cooling water quality control as an application technology develop rapidly.In the factory, cooling water is mainly used to condense steam and cool products or equipment. If the cooling effect is poor, it will affect the production efficiency, reduce the product yield and product quality, and even cause production accidents.
Water is an ideal cooling medium.Because water is very common, compared with other liquids, water has a larger heat capacity or specific heat, and its latent heat of vaporization (evaporation) and melting is also very high.Specific heat is the heat absorbed when the temperature of unit mass of water rises by one degree.The commonly used units are calorie/gram degree (Celsius) or British thermal unit (B.T.U.)/pound degree (Fahrenheit).When these two units are used to express the specific heat of water, their values are the same.The material with large heat capacity or specific heat needs to absorb a large amount of heat when its temperature rises, but its own temperature does not rise significantly, so water has good heat storage performance.Latent heat is the heat absorbed or released when the state of matter changes.The evaporation of one gram of water into one gram of steam needs to absorb nearly 10000 calories of heat. Therefore, water can absorb a lot of heat when evaporating, so that the water temperature will drop. This process of relying on water evaporation to take away heat is called evaporation heat dissipation.
andwaterSimilarly, air is also a common cooling medium.The thermal conductivity of water and air is very poor. At 0 ℃, the thermal conductivity of water is 0.49 kcal/m · h · ℃thermal conductivityIt is 0.021 kcal/m · h · ℃, but the thermal conductivity of water is about 24 times higher than that of air.Therefore, when the cooling effect is the same, water cooling is much smaller than air cooling equipment.Large industrial enterprises and factories with large water consumption generally use water cooling.Commonly used water cooling systems can be divided into three categories, namely, once through system, closed system and open evaporation system. The latter two cooling water systems are recycled, so they are also calledCirculating cooling water system。
cooling water system The system that uses water to cool the process medium is called the cooling water system.There are usually two kinds of cooling water systems: once through cooling water system and circulating cooling water system.[2]
Closed circulating cooling water systemclosed recirculation cooling water system 。In this system, the cooling water is not discharged immediately after use, but recycled.The open evaporation system is one of the most widely used cooling systems with the most types.It also uses water cooling to remove the heat emitted by the process medium or heat exchange equipment, and then evaporates some of the hot water when the hot water is in direct contact with the air, so that most of the hot water can be recycled after being cooled.Therefore, such a system is also called an open circulating cooling water system.According to the different contact methods of hot water and air, it can be divided into many types.See Table I for classification of open circulating cooling water system.[2]
Table IClassification of open evaporation systems
Classification of open evaporation systems
Cooling tower
The cooling water is sent to each heat exchanger in the system by the circulating pump to cool the process heat medium. The cooling water itself rises in temperature and becomes hot water. The hot water with the circulating water volume of R is sent to the top of the cooling tower and sprayed onto the packing in the tower by the water distribution pipe.The air flows from the tower bottomShutterIt enters the tower in the gap and is pumped up by the fan at the top of the tower to exchange heat with the falling water droplets and the water film on the packing. The water droplets and the water film gradually become cold in the process of falling. When it reaches the cooling pool, the water temperature just drops to meet the requirements of cooling water.As the air rises in the tower, it gradually becomes hot, and finally escapes from the tower top, taking away water vapor.The loss of this part of water is called vapor loss E.When hot water is splashed down from the tower top, due to the influence of external wind blowing and fan suction, there will be a certain splash loss and entrainment loss of the circulating water along with the air.The water lost due to these losses is collectively referred to as wind loss D.In order to maintain a certain ion concentration in the circulating water, the make-up water M must be continuously added to the system and a certain amount of sewage must be discharged outside the system.This amount of water is called blowdown loss B.
There are many types of cooling towers. According to tower structure and air flow, there areNatural draft cooling towerAnd mechanical draft cooling tower.According to the relative flow of air and water in the tower, it can be divided into counter flow type and cross flow type.For the structure and characteristics of various types of cooling towers, please refer to relevant references.Mechanical draft cooling tower has the best cooling effect.The cycle ratio should be comprehensively considered in the design, which should be 3-5 times.[2]
Concentration multiple
Circulating cooling waterThe concentration multiple of is the ratio of the salt content of the circulating cooling water to the salt content of the make-up water.
Increasing the concentration multiple of circulating cooling water can reduce the amount of make-up water, thus saving water resources;It can also reduce the amount of sewage, thus reducing environmental pollution and waste water treatment.In addition, increasing the concentration ratio can also save the consumption of water treatment agent, thus reducing the cost of cooling water treatment.However, if the concentration ratio is increased too muchhardnessWhen the alkalinity and turbidity rise too high, the scaling tendency of water increases a lot, which makes scaling control too difficult;It will also increase the content of corrosive ions (such as Cl and SO4) and corrosive substances (such as H2S, SO2 and NH3) in the circulating cooling water, and increase the corrosivity of water, thus increasing the difficulty of corrosion control;Excessively increasing the concentration ratio will also cause the retention time of agents (such as polyphosphates) in the cooling water system to increase and hydrolyze.Therefore, the concentration ratio of cooling water is not the higher the better. Generally, the thermoelectric system can be controlled 5-8 times, and the chemical industry and oil refining can be controlled 2-4 times.
Quartz sand filtration is one of the most effective means to remove suspended solids in water. It is an important unit in advanced sewage treatment, sewage reuse and water supply treatment.Its function is to further remove the flocculated pollutants in the water. It can achieve the purpose of water purification through the interception, sedimentation and adsorption of filter materials.[2]
Scope of application
1. It is used for industrial water, domestic water and municipal water supply systems that require effluent turbidity ≤ 5mg/L to meet drinking water quality standards;
2. Removal of suspended solids and solids in industrial sewage;
3. Can be used asIon exchange methodPretreatment equipment in softening and demineralization systems, and coarse filtration equipment for industrial water supply with low water quality requirements;It is also used in swimming pool circulating treatment system, cooling circulating water purification system, etc.[2]
Home system
Announce
edit
classification
The preheating circulating water can be roughly divided into four categories: 1Remote control panel(wall crossing remote control);2. Water control version (water popular);3. Computer board (fully automatic);4. Mechanical plate (semi-automatic).
1. For indoor forced exhaust machine, it is recommended to use mechanical circulating water.(Two shower rooms, suitable for mass customers)
Reason: The mechanical version has few programs and is easy to operate. Press it before use. There is a reset switch. It can be used in winter and not in summer.
2. Outdoor unit, it is recommended to use the water flow version if there is a return pipe
Advantages: Turn on the hot water faucet to circulate, and turn off the water to stop.
If there is no return pipe, it is better to use wireless remote control,
Advantages: multiple remote controls are configured for anytime, anywhere operation.
Disadvantages: The outdoor unit is installed far away, and it is inconvenient to switch. If there is a return pipe, boiling water anywhere is equivalent to switching. If there is a remote controller, it can be remotely controlled indoors
Use feeling: when you get up in the morning, you want to take a shower. Don't move it. Just use the remote control at the bedside and go to the bathroom to take a shower when you get up.Open the direct hot water outlet.
3. For indoor balancing machines with more than two shower rooms, circulating water should be installed at a distance. It is strongly recommended to use the mechanical plate inlet pump circulating water system
Reason: The balancing machine is originally installed in the bathroom, which is not too far from the bedroom. Just drive it before use, so that two shower rooms and the kitchen can use hot water at the same time.[1]
Return pipe
It is recommended that those with return pipes can use flow controlled and automatic ones.
1. The water flow means that if you turn on and off the hot water in any place where there is hot water, the circulating water will automatically circulate at the speed of three seconds and one meter. After the circulation is completed, you can turn on any place where there is hot water, and the hot water will come out directly.Advantages: It is strongly recommended that wall mounted furnace users use water flow control, because it can be set for a short time control, that is, hot water can be available at any time within a certain time.
2. Fully automatic means temperature control. Generally, the bath centers such as villas or hair salons can choose the fully automatic mode. The so-called full-automatic mode is to set the temperature of the water heater to 42 degrees, set the circulating water system to 38 degrees, and then connect a temperature sensing probe to the end of the return pipe. In this way, once the temperature is lower than 38 degrees, it will automatically start up. It is wasteful to start up N times a day,It is recommended that families do not use this function.
Note: Why can't the above two functions be used without a return pipe? If the water flow does not have a return pipe, sometimes the cold water will start. Because the pump body of the water control panel is equipped with a water flow sensor, the circulating water will work if the water in the pipe fluctuates greatly.
The temperature control should not be used, because if there is no return pipe, the circulating water will squeeze the cold water inside the hot water pipe into the cold water pipe when it is started frequently. In this way, the cold water can also be turned on to produce hot water. Therefore, users who use the computer board should not debug the computer board by themselves, so as to avoid the debugging error being set to the temperature control.
If there is no return pipe, it is recommended to use mechanical board or remote control board.
1. The mechanical board is the most economical, because there are few components in the mechanical board, the failure rate must be low.
2. The remote control panel can directly control the circulating water system when lying on the bed, and then the preheating effect can be achieved.
Precautions for solar energy users: the installation of solar energy circulating water system must have a return pipe. If there is no return pipe, the circulation effect cannot be achieved. It is recommended not to buy blindly. Before purchasing, it is recommended to consult experts for solutions.The solution is to add another return pipe. The manufacturer has not solved the problem of solar energy installation without return pipe.[1]
