Application and selection of chiller (ice water machine)
In recent years, with China's accession to the WTO, the manufacturing industry has entered a golden period, and at the same time, the market competition is fierce, and the requirements for product quality have also been greatly improved. In fact, in the process of improving products, manufacturers often overlook a subtle and important factor. In the production process, due to the continuous generation of heat in the mechanical, mold and industrial reactions, the product quality is unstable when the temperature exceeds the material tolerance. The plastic products and electroplating production are taken as examples. The cooling time in the production of plastic products accounts for more than 80% of the whole cycle. The importance of reducing the cooling time shows that the chilled water can absorb heat in time, so that the temperature of the cavity is rapidly reduced, the product is accelerated, and the opening is shortened. So now, Hengxing and chiller (http://) tell you about the selection method of some chillers. I hope I can help my friends.
In electroplating production, chilled water can lower the temperature of the plating solution and keep the temperature constant within a certain range, so that the metal molecules are quickly attached to the surface of the plating member with a steady current, so that the product is smooth and the density is increased. Industrial chiller (temperature range: +20 °C TO -25 °C adjustable) is widely used in a variety of industrial production - 1. Chemical (scholar) industry 2. Plastic products, plastic containers, film, plastic profiles, pipes, wires , cable sheathing, tire industry 3. Electroplating and machine cutting fluid cooling industry 4. Pharmaceutical industry 5. Electronics industry 6. Hardware industry 7. Food and beverage industry 8. Footwear industry 9. Laboratory 10. Medical equipment 11. Optical Instruments, etc.
1. The chemical industry is mainly used for cooling and cooling of chemical reactors (chemical heat exchangers), and takes away the huge heat generated by chemical reactions in time to achieve the purpose of cooling (cooling) to improve product quality.
2. Manufacturing industry for plastic products, plastic containers, food packaging films, medical packaging films, etc. â— In the injection molding process of plastic products (television, computer, washing machine, mobile phone, refrigerator, air conditioner, plastic toy, automotive plastic parts, etc.) Timely and effective cooling (cooling) will directly affect the appearance and appearance of the product, which will affect production efficiency and affect production costs and corporate profits.
â— The production of plastic containers (blowing bottles) and packaging films is even more inseparable from chillers (ice water machines). If the plastic container cannot be cooled and shaped in the production process, the produced container will not be full, the wall thickness will be uneven, the color will not be bright, and even the molding will not be possible, resulting in low product quality. In the production of packaging film, if there is no cold water (wind) cooling molding, it is impossible to produce a qualified product. Cooling with cold water (wind) provided by a chiller (ice water machine) not only greatly improves product quality, but also increases production efficiency.
3. Cooling of electroplating solution, hydraulic oil and machine tool cutting coolant â—In electroplating production, the electroplating solution generates heat in the electroplating reaction without any part, so that the temperature of the plating solution gradually rises. When the temperature of the electroplating solution is higher than the process requirement, It has a great influence on the firmness, uniformity, flatness and surface finish of the surface plating of the produced electroplated products. The choice of chiller (ice water machine) provides the freezing of the electronic components in the production process to maintain or cool the components at a specific temperature, the performance parameters of the electronic components can be controlled in the design state. Water to cool and maintain the constant temperature of the plating solution will greatly improve the electroplating production process and production efficiency.
â— The cooling of the coolant of the machine tool cutting tool, the control of the blade edge temperature will directly affect the tool life and product quality.
4. Pharmaceutical industry The pharmaceutical industry is mainly used for the control of temperature and humidity in production workshops and the heat of reaction in the process of producing APIs.
5. The electronics industry requires the components to be held or cooled at specific temperatures during the production of electronic components. The performance parameters of the electronic components can be controlled in the design state.
Several questions about the selection of chillers
First, how to choose a chiller In fact, a pair of molds is a heat exchanger, heat is transferred from the molten plastic to the mold, and then the mold is introduced into the circulating cooling medium - ice water, only a small part of the air enters the air And the press template of the injection molding machine. It is well known that a relatively large portion of the plastic molding cycle is used for cooling, sometimes accounting for more than 80% of the plastic molding cycle, so it is absolutely necessary to control the cooling time to a minimum. For example, a mold molding cycle is generally 20 seconds. If the water in the original cooling tower is changed to ice water produced by a chiller, it can be shortened to 16 seconds. Although the chiller originally selected is more expensive, it can increase production by 20% and achieve significant gains in long-term production. So how do you choose the energy of ice water? From the above we can know that it is related to the specific heat of the molding material, the temperature at the time of melting, the weight and the temperature at which the product is demolded. The formula for calculating the ice water energy required for a pair of molds is: Q=W×C×△T×S
Where: Q is the required ice water energy kcal/h;
W is the weight of the plastic raw material kg / h;
C is the specific heat of the plastic raw material kcal / kg ° C;
△T is the temperature difference between the temperature of the melt and the release of the product °C (see attached table);
S is the safety factor (usually 1.35-2.0). When the single machine is matched, the small value is generally selected. When a chiller is matched with multiple molds, the value is taken. If the air-cooled chiller is selected, S should also be used. Choose a bigger one.
For example: a pair of molds to produce PP products, the production volume per hour is about 50kg, what is the cooling requirement? What size should the chiller be suitable for?
Q=50×0.48×200×1.35=6480(kcal/h);
It requires 6480kcal/h cooling per hour. It is difficult to obtain more complete data during the PR chiller. According to our previous years of planning and supporting sales experience, △T=200°C, it is an average value of many common products after years of statistics.
If the hot glue path is attached to the mold, the energy of the hot glue path should be added to the calculation of the cold amount. Generally, the hot glue path is in KW. When calculating, the unit should be converted into kcal/h, 1KW=860kcal/h. If the water supplied to the plant is sufficient, the temperature is low, and the cost is low, there is no need to use a chiller at this time, which is generally unrealistic unless the plant can be at the lake with low water temperature; the other is Urban deep well water supplies meet the needs of temperature and flow, but often the cost is too high. This method can be used for experimental setups, but for factories it is impractical to do so.
Second, ice water temperature difference mold cooling fluid (ice water) temperature is generally subject to changes in the shape of processed materials and products, such as polyethylene thin wall beakers, molds require ice water temperature below 0 ° C; and most other In case, the temperature of the ice water required by the mold is above 5 °C. The microcomputer full-function chiller can provide ice water above 5 °C. The low-temperature intelligent temperature-controlled chiller can meet the requirements below 5 °C and below 0 °C.
The temperature difference between the ice water at the inlet and outlet of the mold is often set according to the requirements of the product. In many cases, the temperature difference is 3-5 ° C is ideal, but sometimes the temperature difference is 1-2 ° C. The smaller the temperature difference, the greater the flow of ice water required to carry the same amount of heat out, and the smaller the flow required. For example, when the temperature difference is 5 °C, the flow rate needs 60L, and when the temperature difference is 2 °C, the flow rate needs 150L.
Third, the ice water flow required for a pair of mold ice flow is directly related to the heat to be taken away by the mold and the temperature difference between the ice water entering and leaving the mold. For example; to take 6480kcal/h of heat away from the mold, if the temperature difference is 3 °C, what is the minimum flow required? Ice water flow Q = 6480 ÷ 3 ÷ 60 = 36 (L / min).
Fourth, the softening of ice water quality treatment water, in the process of using chiller, is also a problem that can not be ignored, the pH value of water also needs to be constantly observed, the best PH value should be equal to 7, greater than 7 PH value It will produce terrible corrosion. If no measures are taken, it will cause scale in the evaporator and mold, which will act as heat insulation. In severe cases, the energy conversion effect will be reduced by 30%. Obviously this requires consideration of softening of hard water. The most efficient method is to configure an electronic hard water softener in the system. The softener is designed by ion exchange principle. Depending on the flow rate, softeners of different specifications can be configured to be directly connected to the circulating water line. Generally, the cost of the water treatment softener is not too high, and a certain proportion of detergent can be added to the circulation system periodically. .
5. The flow rate and pressure of the ice water machine are generally cooled by injection molding. The pressure of ice water is 0.1~0.2Mpa, which can meet the requirements. The full-function cold water machine of microcomputer can meet this requirement. When the pressure requirement is higher than 0.2Mpa, it needs to be separately Planning to facilitate the use of pumps with corresponding pressures to meet the needs of the system's water supply.
Table of relationship between flow and pipe diameter:
Pipe diameter 3/8′′ 1/2′′ 3/4′′ 1\" 1\'/4′′ 1\'/2′′ 2′′ 3′′
Flow rate 12 20 35 60 90 130 230 560
First, how to choose a chiller In fact, a pair of molds is a heat exchanger, heat is transferred from the molten plastic to the mold, and then the mold is introduced into the circulating cooling medium - ice water, only a small part of the air enters the air And the press template of the injection molding machine. It is well known that a relatively large portion of the plastic molding cycle is used for cooling, sometimes accounting for more than 80% of the plastic molding cycle, so it is absolutely necessary to control the cooling time to a minimum. For example, a mold molding cycle is generally 20 seconds. If the water in the original cooling tower is changed to ice water produced by a chiller, it can be shortened to 16 seconds. Although the chiller originally selected is more expensive, it can increase production by 20% and achieve significant gains in long-term production. So how do you choose the energy of ice water? From the above we can know that it is related to the specific heat of the molding material, the temperature at the time of melting, the weight and the temperature at which the product is demolded. The formula for calculating the ice water energy required for a pair of molds is: Q=W×C×△T×S
Where: Q is the required ice water energy kcal/h;
W is the weight of the plastic raw material kg / h;
C is the specific heat of the plastic raw material kcal / kg ° C;
△T is the temperature difference between the temperature of the melt and the release of the product °C (see attached table);
S is the safety factor (usually 1.35-2.0). When the single machine is matched, the small value is generally selected. When a chiller is matched with multiple molds, the value is taken. If the air-cooled chiller is selected, S should also be used. Choose a bigger one.
For example: a pair of molds to produce PP products, the production volume per hour is about 50kg, what is the cooling requirement? What size should the chiller be suitable for?
Q=50×0.48×200×1.35=6480(kcal/h);
It requires 6480kcal/h cooling per hour. It is difficult to obtain more complete data during the PR chiller. According to our previous years of planning and supporting sales experience, △T=200°C, it is an average value of many common products after years of statistics.
If the hot glue path is attached to the mold, the energy of the hot glue path should be added to the calculation of the cold amount. Generally, the hot glue path is in KW. When calculating, the unit should be converted into kcal/h, 1KW=860kcal/h. If the water supplied to the plant is sufficient, the temperature is low, and the cost is low, there is no need to use a chiller at this time, which is generally unrealistic unless the plant can be at the lake with low water temperature; the other is Urban deep well water supplies meet the needs of temperature and flow, but often the cost is too high. This method can be used for experimental setups, but for factories it is impractical to do so.
Second, ice water temperature difference mold cooling fluid (ice water) temperature is generally subject to changes in the shape of processed materials and products, such as polyethylene thin wall beakers, molds require ice water temperature below 0 ° C; and most other In case, the temperature of the ice water required by the mold is above 5 °C. The microcomputer full-function chiller can provide ice water above 5 °C. The low-temperature intelligent temperature-controlled chiller can meet the requirements below 5 °C and below 0 °C.
The temperature difference between the ice water at the inlet and outlet of the mold is often set according to the requirements of the product. In many cases, the temperature difference is 3-5 ° C is ideal, but sometimes the temperature difference is 1-2 ° C. The smaller the temperature difference, the greater the flow of ice water required to carry the same amount of heat out, and the smaller the flow required. For example, when the temperature difference is 5 °C, the flow rate needs 60L, and when the temperature difference is 2 °C, the flow rate needs 150L.
Third, the ice water flow required for a pair of mold ice flow is directly related to the heat to be taken away by the mold and the temperature difference between the ice water entering and leaving the mold. For example; to take 6480kcal/h of heat away from the mold, if the temperature difference is 3 °C, what is the minimum flow required? Ice water flow Q = 6480 ÷ 3 ÷ 60 = 36 (L / min).
Fourth, the softening of ice water quality treatment water, in the process of using chiller, is also a problem that can not be ignored, the pH value of water also needs to be constantly observed, the best PH value should be equal to 7, greater than 7 PH value It will produce terrible corrosion. If no measures are taken, it will cause scale in the evaporator and mold, which will act as heat insulation. In severe cases, the energy conversion effect will be reduced by 30%. Obviously this requires consideration of softening of hard water. The most efficient method is to configure an electronic hard water softener in the system. The softener is designed by ion exchange principle. Depending on the flow rate, softeners of different specifications can be configured to be directly connected to the circulating water line. Generally, the cost of the water treatment softener is not too high, and a certain proportion of detergent can be added to the circulation system periodically. .
5. The flow rate and pressure of the ice water machine are generally cooled by injection molding. The pressure of ice water is 0.1~0.2Mpa, which can meet the requirements. The full-function cold water machine of microcomputer can meet this requirement. When the pressure requirement is higher than 0.2Mpa, it needs to be separately Planning to facilitate the use of pumps with corresponding pressures to meet the needs of the system's water supply.
Table of relationship between flow and pipe diameter:
Pipe diameter 3/8′′ 1/2′′ 3/4′′ 1\" 1\'/4′′ 1\'/2′′ 2′′ 3′′
Flow rate 12 20 35 60 90 130 230 560
6. Cooling of the hydraulic oil and barrel feeding section Generally, the hydraulic oil and the barrel feeding section are cooled by the water of the cooling tower, because this is not only the best method, but also economical in terms of production cost, unless There are specific requirements for its temperature, which can be cooled with ice water.
7. The insulated ice water pipe of the ice water pipeline must be insulated and insulated, because the pipe insulation not only prevents the serious loss of the cold, but also prevents the dew condensation water formed on the outer wall of the pipe. For example: ice water temperature 10 ° C, ambient temperature 30 ° C, a 25 m long, surface area of ​​25 m2 metal pipe heat radiation up to 750kcal / h, which is almost 10% of the cooling capacity of 3HP compressor, 5HP compression The amount of refrigeration generated by the machine is about 6%.
The connection between the chiller and the mold is usually connected by a reinforced hose, because such a hose has its own function of heat insulation, but the length is more than 5 m, and moderate insulation is also considered.
Schedule: Injection molding and mold temperature and specific heat required for different molding materials.
Material Injection Temperature °C Mold Temperature °C Specific Heat Kcal/kg°C
Polyethylene 160～310 0～70 0.55
Polystyrene 185～250 0～60 0.35
Nylon NYLON 230～300 25～70 0.58
Polycarbonate PC 280～320 70～130 0.03
Polypropylene PP 200～280 0～80 0.48
ABS 180～260 40～80 0.40
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