Water chillers are energy-saving machines that achieve refrigeration effects through steam compression or absorption cycles. The full name of water chillers is cooling water circulators, also known as refrigerators, chillers, freezers, water chillers, ice chillers, small water chillers, industrial water chillers, refrigeration units, low-temperature water chillers, and laser water chillers. Due to their widespread use in various industries, their aliases are countless depending on the industry.
The water chiller is closely related to the quality of the mold industry, and considerable attention is paid to the quality of the mold industry. The external surface finish of the mold must reach Grade 7 (Ra1.6), such as the surface produced by cold extrusion or machining, with a metallic luster. The tolerances and finishes indicated on the drawings all affect product molding, so during processing, appropriate chillers should be selected for cooling based on different accuracy requirements.
There are many mold hardware factories that want to achieve their desired cooling effect, but do not know which machines are more suitable for their production workshops. Now, Beijing Beike Pu will analyze the selection of mold cooling water chillers and precautions for everyone, hoping to be helpful to friends in the mold industry.
A mold is a heat exchanger, where heat is transferred from melted plastic into the mold, and then into the constantly circulating cooling medium - ice water. Only a small portion enters the air and the molding plate of the injection molding machine. It is well known that a significant portion of the plastic molding cycle is used for cooling, sometimes accounting for more than 80% of the plastic molding cycle. Therefore, it is absolutely necessary to minimize the cooling time. For example, the molding cycle for a pair of molds typically takes 20 seconds. If the water from the original cooling tower is replaced with ice water generated by a water chiller for cooling, it can be reduced to 16 seconds. Although the cost of the initially selected chiller is higher, it can increase production by 20% and can yield significant benefits in long-term production. So, how to choose ice water energy? 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 the time of demolding the product.
1、 Treatment of water quality of mold cooling chiller
The softening of water is also a problem that cannot be ignored during the use of water chillers in the mold industry. The pH value of water also needs to be constantly observed. The optimal pH value should be equal to 7, and a pH value greater than 7 can cause terrible corrosion phenomena. If no measures are taken, scaling can occur in the evaporator and mold, which can act as heat insulation. In severe cases, the energy conversion effect can be reduced by 30%. This clearly requires consideration of softening of hard water. The most effective method is to configure an electronic hard water softener in the system, which is designed and manufactured based on the principle of ion exchange. Depending on the flow rate, softeners of different specifications can be configured and directly connected to the circulating water pipeline. Generally, the cost of configuring a water treatment softener is not too high, and a certain proportion of scale remover can also be regularly added to the circulating system.
So, how to choose ice water energy? 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 the time of demolding the product.
2、 First, consider the temperature difference of the mold cooling water chiller
The temperature of mold cooling fluid (ice water) is generally subject to significant changes in processing materials and product shape, such as polyethylene thin-walled beakers, where the ice water temperature is required to be below 0 ℃ for molds; In most other cases, the temperature of ice water required by the mold is above 5 ℃. The microcomputer fully functional cold water machine provides ice water above 5 ℃. The low-temperature intelligent temperature controlled cold water machine meets the requirements of below 5 ℃ and below 0 ℃.
The temperature difference between the ice water at the mold inlet and outlet is often set according to product requirements. In many cases, a temperature difference of 3-5 ℃ is optimal, but sometimes a temperature difference of 1-2 ℃ is also required. The smaller the temperature difference, the greater the flow of ice water required to carry the same amount of heat out, while the smaller the flow required.
For example, when the temperature difference is 5 ℃, the flow requires 60L, while when the temperature difference is 2 ℃, the flow requires 150L. Ice water flow The ice water flow required for a mold is directly related to the heat to be taken away by the mold and the temperature difference between the ice water entering and exiting the mold. For example; To remove 6480 kcal/h of heat from the mold, if the temperature difference is 3 ℃, what is the minimum required flow rate? Ice water flow Q=6480 ÷ 3 ÷ 60=36 (L/min).
3、 Flow and pressure of mold cooling chiller
Generally, for cooling of injection molding molds, the pressure of ice water can be selected from 0.1 to 0.2 Mpa to meet the requirements, while the microcomputer fully functional cold water system can meet this requirement. When the pressure requirement is higher than 0.2 Mpa, additional planning is required to facilitate the use of pumps with corresponding pressure to meet the water supply needs of the system.
Table of Relationship between Flow and Pipe Diameter: Pipe Diameter 3/8 ″ 1/2 ″ 3/4 ″ 1 "1 '/4 ″ 1'/2 ″ 2 ″ 3 ″ Flow 1220356090130230560
It requires 6480 kcal/h of cooling capacity per hour, and it is difficult to obtain relatively complete data during the process of selecting a PR water chiller. According to our previous years of planning and supporting sales experience, △ T=200 ℃, which is an average value of many commonly used products after years of statistics.
Water chiller application industry:
Water chillers are mainly used in the plastic industry: plastic molding, injection molding, extrusion, bottle blowing, thermal molding, mechanical industry: laser technology, welding, mechanical cutting, non cutting processing, casting, electroplating, electronics industry: surface treatment, electroplating, electrophoresis, medical equipment, electronics industry, circuit board production, electronic chip manufacturing, chemical industry and other industries: chemical, paper, pharmaceutical, food processing, aluminum profiles Aluminum alloy, tempered glass, coated glass production, ultrasonic cleaning, jewelry processing, leather, fur processing, ink production, aquaculture.