Definition of steam heat exchanger and types of two heating equipment
The steam heat exchanger is similar in structure to the conventional heat exchanger, except that its heat source is steam. In industrial production activities, equipment that uses steam as a heat source to heat water can be divided into two categories. One type is direct heating equipment, and the other is indirect heating equipment. The following describes the types of equipment included in these two types.
First, direct heating equipment
Steam heat exchanger
The steam heat exchanger uses a high steam flow rate to produce a negative vacuum suction water mixture. The conditions of use not only require a certain pressure of the steam, but also must have a certain kinetic energy to mix.
2. Steam mixer
The steam is directly injected into the water through the same-diameter porous device. The steam pressure must be greater than the system pressure of 0.2MPa or more, the steam flow rate is not adjustable, there is noise, and the steam pressure and the system pressure overlap when opening or closing, which has certain destructive power to the heating and air conditioning system. Cannot be used in closed systems, is a phase-out product.
3. Spray heat exchanger
Water is injected into the steam directly by spraying through a porous device. Adjustable steam flow, no noise, 0.2MPa low pressure steam is excellent. Disadvantages: It is afraid that the impurities in the water will block the spray holes, and the heat exchanger will be easily vaporized when the steam pressure fluctuates greatly. The bath must be stored with a water tank and a water pump, and cannot be isothermally exchanged.
Second, indirect heat exchange equipment
1. Tube heat exchanger
Laminar heat transfer, first-class heat transfer thermal efficiency does not exceed 80%, condensate temperature is high, exceeds 100 ° C, easy to vaporize, steam pressure is lower than 0.2 MPa, easy to generate steam and water impact noise, and has the function of storing hot water The water temperature is hot and cold. Heavy weight, easy to scale. Due to the need for a certain pipe-drawing distance for maintenance, the floor space is large and the price is high, which basically eliminates the product.
2. Spiral plate heat exchanger
With laminar heat transfer, there are two different materials: one is carbon steel and the other is stainless steel. The thermal efficiency is less than 80% and cannot be repaired in one use. The ratio of the tubular tube is relatively small, easy to scale, low in cost, and the condensate temperature exceeds 100 °C. Easy to vaporize, when the steam pressure is less than 0.2MPa, the condensed water and steam generate soda water impact noise, which is not widely used because of the low price.
3. Bellows heat exchanger
The vibration and laminar flow mixing heat transfer, the first-stage heat transfer thermal efficiency does not exceed 80%, the land occupation is small, the scale is easy to scale, the condensation temperature exceeds 100 ° C, the vaporization is easy, and the steam pressure is less than 0.2 MPa, the water and steam generate impact noise. Because of the small size, it was a popular product in the early 1990s.
4. Floating coil heat exchanger
Using vibration heat transfer, the technology is basically developed from the introduction of American technology. The use of steam kinetic energy, the heat transfer surface generates vibration to destroy the water film, and the laminar flow becomes steady flow heat transfer. It is a relatively advanced method in the world, and can use the temperature difference to detach itself from hard scale, but it is ineffective for microporous soft scale. Depending on the manufacturing process, the thermal efficiency is about 80%-90%. Steam below 0.2 MPa is prone to soda impact noise. The storage type has a large temperature difference between the upper and lower sides, and there is a dead water area. When the steam pressure and the water pressure are large, the vibration frequency is too large, the water molecules are not in contact with the heat exchange surface, and the heat cannot be transferred. If it is too small, the water film is not damaged and the heat transfer coefficient is affected.