Heat and cold pipe exchanger
Heat-exchangers of the plate type, plate heat exchanger, plate type heat exchanger
It is composed of stamped and formed concave-convex stainless steel plates. The concave-convex lines between the two adjacent plates form a 180-degree relative combination, so the concave-convex ridges between the two plates of the plate heat exchanger form staggered contact points. After the contact points are combined by vacuum welding, they form The high-pressure-resistant staggered circulation structure of the plate heat exchanger, these staggered circulation structures make the cold and hot fluid in the plate heat exchanger produce strong turbulence to achieve a high heat exchange effect. The plate heat exchanger is composed of a set of corrugated metal plates with four corner holes for the two liquids to pass through. The metal plates are installed in a frame with a fixed plate and a movable compression plate on the side, and are clamped by clamping bolts. The plate is equipped with a sealing gasket to seal the fluid channel and guide the fluid to alternately flow into the respective flow channel to form heat exchange. The fluid flow rate, physical properties, pressure drop and temperature difference determine the number and size of the plates. The corrugated plate not only improves the degree of turbulence, but also forms many supporting points, which are enough to withstand the pressure difference between the media. The metal plate and the movable plate pressing plate are hung on the upper guide rod and positioned by the lower guide rod, and the rod end is fixed on the support column.
Chinese name plate heat exchanger, foreign name Plate heat exchanger material stainless steel, titanium alloy application field refrigeration, heating, ventilation, air conditioning, oil cooling
2 working principle
3 Application areas
4 Pay attention to the problem
5 Cleaning method
1. The plate heat exchanger is made of polymer synthetic fiber using a special process, which has the characteristics of high moisture permeability, good air tightness, tear resistance, and aging resistance.
2. The energy-saving effect of plate heat exchanger products has reached the advanced level abroad, with long life and good temperature conductivity, suitable for areas with large indoor and outdoor temperature differences and small humidity differences.
3. The plate heat exchanger can be equipped with different functional sections such as heating, cooling, humidification, purification, and noise reduction according to user requirements.
4. Plate heat exchangers usually use stainless steel (sus 304, sus316), titanium alloys to be brazed in vacuum at high temperature to form brazed welding, or use sealing ring bolts to lock into a combined type.
5. The plate heat exchanger forms a compact plate heat exchanger, which can withstand operation under continuous high temperature and high pressure conditions.
Nengke plate heat exchanger is an important device for large-scale air conditioning system exhaust energy recovery, high temperature flue gas waste heat recovery and computer CPU heat dissipation. The structure has a vacuum liquid-filled head and a core. The vacuum liquid-filled head is set on both sides of the vacuum liquid-filled channel. One side of the vacuum-filled head is provided with a nozzle. The core consists of a vacuum-filled channel and several plate-fin channels. It is constructed by stacking at intervals. The vacuum filling channel is provided with partitions on the upper and lower sides, and seals are arranged on both sides, and fins can be arranged in the channel. The plate-fin channel is provided with partitions on the upper and lower sides, seals are arranged on both sides, and fins are arranged in the channel. Each plate-fin channel is divided into two parallel heat medium channels and cold medium channels by a strip. After assembling, the whole is arranged horizontally inclined or vertically.
Refrigeration, HVAC, air-conditioning, oil cooling and other industries; heat treatment plants and brazing plants; automobile parts manufacturing plants, mechanical hardware and injection molding machine manufacturers, home appliance air-conditioning plants, shipbuilding industries, etc.
a. Refrigeration: used as a condenser and evaporator.
b. HVAC: intermediate heat exchangers used with boilers, intermediate heat exchangers for high-rise buildings, etc.
c. Chemical industry: soda ash industry, synthetic ammonia, alcohol fermentation, resin synthesis cooling, etc.
d. Metallurgical industry: heating or cooling of aluminate mother liquor, cooling of chain steel process, etc.
e. Machinery industry: various quenching liquid cooling, reducer lubricating oil cooling, etc.
f. Power industry: high-voltage transformer oil cooling, generator bearing oil cooling, etc.
g. Paper industry: bleaching process heat recovery, heating washing liquid, etc.
h. Textile industry: cooling of viscose lye solution, cooling of boiling nitrocellulose, etc.
i. Food industry: fruit juice sterilization and cooling, animal and vegetable oil heating and cooling, etc.
j. Grease process: soap-based atmospheric drying, heating or cooling various process liquids.
k. Central heating: heating the waste heat area of the thermal power plant and heating the bath water.
l. Others: petroleum, medicine, ships, seawater desalination, geothermal utilization
Pay attention to the problemedit
The plate type or corrugated type should be determined according to the actual needs of the heat exchange occasion. If the flow rate is large and the pressure drop is small, the plate type with small resistance should be selected, otherwise, the plate type with large resistance should be selected. According to the fluid pressure and temperature, determine whether to choose a detachable type or a brazing type. When determining the plate type, it is not advisable to choose a plate with a single plate area that is too small, lest there are too many plates, the flow rate between the plates is too small, and the heat transfer coefficient is too low. This problem should be paid more attention to for larger heat exchangers.
The process refers to a group of parallel flow channels in the same flow direction of a medium in the plate heat exchanger, and the flow channel refers to the medium flow channel composed of two adjacent plates in the plate heat exchanger. Generally, several flow channels are connected in parallel or in series to form different combinations of cold and hot medium channels.
The process combination form should be calculated based on heat exchange and fluid resistance, and determined under the requirements of process conditions. Try to make the convective heat transfer coefficients in the cold and hot water channels equal or close to get the best heat transfer effect. Because the convective heat transfer coefficient on both sides of the heat transfer surface is equal or close to the heat transfer coefficient to obtain a larger value. Although the flow velocity between the plates of the plate heat exchanger is not equal, the average flow velocity is still used in the calculation of heat exchange and fluid resistance. Since the pipes of the "U"-shaped single process are all fixed on the compression plate, it is convenient to disassemble and assemble.
In the design and selection of plate heat exchangers, there are generally certain requirements for pressure drop, so it should be checked. If the check pressure drop exceeds the allowable pressure drop, the design selection calculation needs to be re-calculated until the process requirements are met. 
According to the form of the heat exchanger, there should be enough space at both ends of the heat exchanger to meet the requirements of condition (operation) cleaning and maintenance. When the fixed tube plate heat exchanger is installed, there should be enough space at both ends so that the tubes can be drawn out and replaced. In addition, when cleaning the inside of the tube by mechanical method, both ends of the tube can be scrubbed. The fixed head cover end of the floating head heat exchanger should have enough space to be able to withdraw the tube bundle from the shell, and the outer head cover end must also leave a position of more than one meter to install and remove the outer head cover and the floating head cover. The fixed head cover of the U-shaped tube heat exchanger should leave enough space to draw out the tube bundle, or leave enough space at its opposite end to allow the shell to be removed.
When chemical cleaning is used, it is necessary to analyze and test the scale of the scale according to the actual conditions and water quality to prepare reagents for cleaning.
Since the difficulty of cleaning increases rapidly with the increase of the thickness or deposition of the scale layer, the cleaning interval should not be too long. It should be based on the characteristics of the production device, the nature of the heat exchange medium, the corrosion rate and the operating cycle. Carry out inspection, repair and cleaning.
Tubular heat exchanger
Partial view into inlet plenum of shell and tube heat exchanger of a refrigerant based chiller for providing air-conditioning to a building
A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant.
2.1Shell and tube heat exchanger
2.2Plate heat exchangers
2.3Plate and shell heat exchanger
2.4Adiabatic wheel heat exchanger
2.5Plate fin heat exchanger
2.6Finned tube heat exchanger
2.7Pillow plate heat exchanger
2.8Waste heat recovery units
2.9Dynamic scraped surface heat exchanger
2.10Phase-change heat exchangers
2.11Direct contact heat exchangers
2.12Microchannel heat exchangers
3HVAC and refrigeration air coils
4Helical-coil heat exchangers
5Spiral heat exchangers
7Monitoring and maintenance
8.2Birds, fish, marine mammals
11Current market and forecast
12A model of a simple heat exchanger
Countercurrent (A) and parallel (B) flows
Fig. 1: Shell and tube heat exchanger, single pass (1–1 parallel flow)
Fig. 2: Shell and tube heat exchanger, 2-pass tube side (1–2 crossflow)
Fig. 3: Shell and tube heat exchanger, 2-pass shell side, 2-pass tube side (2-2 countercurrent)
There are three primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is the most efficient, in that it can transfer the most heat from the heat (transfer) medium per unit mass due to the fact that the average temperature difference along any unit length is higher. See countercurrent exchange. In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger.
For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger. The exchanger's performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence.
The driving temperature across the heat transfer surface varies with position, but an appropriate mean temperature can be defined. In most simple systems this is the "log mean temperature difference" (LMTD). Sometimes direct knowledge of the LMTD is not available and the NTU method is used.
Double pipe heat exchangers are the simplest exchangers used in industries. On one hand, these heat exchangers are cheap for both design and maintenance, making them a good choice for small industries. On the other hand, their low efficiency coupled with the high space occupied in large scales, has led modern industries to use more efficient heat exchangers like shell and tube or plate. However, since double pipe heat exchangers are simple, they are used to teach heat exchanger design basics to students as the fundamental rules for all heat exchangers are the same.
1. Double-pipe heat exchanger (a) When the other fluid flows into the annular gap between two tubes, one fluid flows through the smaller pipe. The flow may be a current flow or parallel flow in a double pipe heat exchanger. (b) Parallel flow, where at the same point, the hot and cold liquids join, flow in the same direction and exit at the same end.
(c) Counter flow, where at opposite ends, hot and cold fluids join, flow in the opposite direction and exit at opposite ends.
The figure above illustrates the parallel and counter-flow flow directions of the fluid exchanger. If this is done under comparable conditions, more heat is transferred to the counter-flow device than to the parallel flow heat exchanger. Owing to the large temperature