Heat exchanger Basics
Heat : refers to objects that are conducted between two cold heat transfer , the heat transfer process.
Heat Purpose:
A: heating or cooling , vaporization , condensation of the production process in order to maintain the required temperature , power and phase calendar ;
B: conduction, radiation. The case of the two substances do not mix temperature conductivity changes ;
C: high-calorie utilization, heat utilization : The hot fluid to be cooled cold fluid to be heated heating .
Classified by mode of heat transfer
A direct heat heat exchanger. One kind of wall without heat , hot fluid from the cold fluid and direct contact heat exchanger during operation , such heat exchangers are often used in industrial production .
Two partitions heat heat exchanger. Cold and hot fluid through the tube , and plate heat exchange of the heat transfer wall surface of the heat exchanger during operation , is the most common and most commonly used heat , cold, hot fluid is a fluid , can be air, gas , steam, water . This is the focus of this article to discuss the type of heat exchanger .
3 regenerative heat exchanger. Department of intermittent heat , the heat regenerator is feasible and effective heat recovery means , is often used to recover waste heat of combustion gas and steam, the amount of the adjustment method unevenly .
Several types of heat exchanger

1: finned
    The finned heat exchanger tube box , shell, tubes and other major elements. Finned heat exchanger tube bundle core tubes as the heat-conducting element , together with the decision baffle heat exchanger heat transfer performance. Tube box and the shell has decided finned heat exchanger pressure capability and operational safety and reliability .
    Finned heat exchanger is recuperative heat exchanger, the heat exchange fluid passage formed within and known tube , tubes constituting the fluid channel is called the outer shell . Tube and shell respectively, through two different fluid temperature , the higher temperature fluid through the wall of the heat transfer tubes to the low temperature fluid , the higher temperature fluid is cooled , the lower temperature fluid is heated , thus achieving two fluid heat transfer process purposes.

2: Shell and Tube
    Shell and tube heat exchanger. Shell and tube heat exchanger is the most common general structure , which includes : a fixed tube heat exchanger , U-shaped shell and tube heat exchangers, heat exchanger with expansion joints , floating head heat exchanger, segmented for heat , tube heat exchanger , etc. Fixed tube heat exchanger has a simple structure , light weight, and low cost ; drawback is due to thermal expansion caused by the tube bending . U-shaped shell and tube heat exchanger is made ​​to overcome this shortcoming of the tube "U" shape , one end fixed other end activities , making the impact of the heat exchanger is not expanded , the structure is relatively simple, light weight , and its shortcomings can not be mechanically cleaned , Removable tube inconvenience , unit capacity and low heat transfer per unit mass for temperature, the tube where the fluid medium relatively clean heat exchanger with expansion joint swelling resolves the problem , with the expansion joints of the structure , it applies to large temperature difference fluid and the high pressure fluid , since the connector can be removed for cleaning, it is possible to easily scale processing fluid , while the low-pressure gas is not suitable , but its drawback is that manufacturing complexity . Floating head shell and tube heat exchanger, floating head is not connected to the housing , free expansion , so that not only solves the problem of thermal expansion , but also easy to clean , repair time could be extracted in the die for a fixed tube sheet , tube , casing each heat exchanger housing when the volume of 1 m3 , the heat transfer area of ​​about 30 ~ 40 m3. The U -type shell and tube heat exchanger, floating head heat exchanger volume of 1 m3 each case , its heat transfer area of ​​about 70 m2 .
    Heat pipe heat exchanger tubes are packaged in a sealed container using a liquid evaporation and condensation processes , efficiently transport heat a heat transfer device . As with a number of heat pipe heat exchanger components and assembled heat pipe heat exchanger called a heat exchanger. Heat pipe type heat exchanger used for air - air heat exchanger , then, both ends of the heating section of the heat pipe and the radiating section with fins to improve the heat transfer . Advantage of the heat pipe heat exchanger heat transfer surface that is essentially isothermal , the heat transfer area per unit volume is large, choose a different working refrigerant , can heat pipe at different temperature conditions , relatively simple structure, the thermal expansion problems caused by small. However , the heat pipe heat exchanger the primary problem , as the heat transfer element is a heat pipe for the working fluid within the working environment of use is a certain critical heat transport quantity and the operating temperature limits , and if the temperature continues to work beyond this limit , then the evaporator section will " dry up " and stop working.

3: Plate
    Plate heat exchanger. Since the heat transfer surface of the plate heat exchanger can be pressed out of convex -shaped drainage grooves , at a lower Reynolds number turbulent state can occur , so the heat transfer coefficient is high , generally up to 3 000 ~ 5 000Kcal / m2. h. ℃, with the same flow rates compared to shell and tube heat exchangers , this value is approximately shell and tube heat transfer coefficient of 3 to 5 times , though , when the resistance of the plate heat exchanger will be larger , such as the power consumption in the same condition as compared to the plate heat exchanger shell and tube heat transfer coefficient ratio of about twice as high . As the plate heat exchanger compact, the gap is small , and thus the heat transfer area per unit volume increases, the mounting shell and tube area of ​​about 1/ 2 to 1 / 3 , and the construction costs can save area , each Case volume of 1 m3 , its heat transfer area of ​​about 80 m2 , in addition, the plate heat exchanger is easy to increase or decrease the heat transfer area for shell and tube heat exchanger in the need to increase the handling capacity of the liquid , the original heat exchanger almost impossible to increase the heat transfer area , the plate heat exchanger is very easy to increase the heat transfer area , thereby increasing the capacity , in addition, only the heat transfer plate heat exchanger shell plate exposed to the atmosphere , and therefore, heat loss negligible , nor do they need insulation measures. Plate heat exchanger in the operation and maintenance aspects of the features is quite easy assembly and disassembly , or even having to completely disassemble , loosen the bolts can only draw the plates clean , replace the gasket , and even replace the plate . This heat transfer medium prone to deposition of the material is particularly important . Allows temperature and pressure : the plate heat exchanger is used by each of the two gaskets between the plates to prevent leakage of materials , thus sealing the periphery of its length is very long, to prevent leakage of the plate heat exchanger gasket is an important part , the gasket can withstand the temperature, pressure and chemical stability is often a plate heat exchanger the temperature and pressure limits, and allows a range of materials . Further, since the small gap between the heat transfer surface , the heat transfer surface of a convex , smooth than traditional large pressure loss , in addition , plate heat exchangers are subject to a lower working pressure .

4: plate-fin
    Plate-fin heat exchanger is by the partition , fin seal , deflector head, interface composed of a heat exchange facility , which seals the fluid through the separator and the outside is divided into two channels separated by board transfer the heat from one medium to another medium , wherein a fluid in order to achieve the purpose of heating or cooling .
    Because of the special structure of the fins , the fluid in the channel to form a strong turbulence , the thermal boundary layer on the continued damage, thus effectively reducing the thermal resistance , improved heat transfer efficiency . General boiling water heat transfer coefficient is 1 500 ~ 30 000 Kcal / m2. H. ℃. Another plate-fin heat exchanger structure more compact, the heat transfer area per unit volume , generally larger than the column tube heat exchanger thermal efficiency of more than five times , each case when a volume of 1 m3 , the heat transfer area of ​​160 m2 or so. Plate-fin heat exchangers are lighter and strong , because the thin fins , usually 0. 2 ~ 0. 3 mm, and as compact structure , small size, generally made ​​of aluminum , which is very light weight , while the fin both the primary heat transfer surfaces , but also the support of two separators , the high strength. Plate-fin heat exchanger adaptable, in the same equipment allows two to nine kinds of medium heat , and can be used for gas - gas , gas - liquid , liquid - liquid heat exchange between . Main disadvantages: due to the narrow channel , prone to blockage and increasing the pressure drop , when the heat exchanger fouling after cleaning is very difficult , and because the separator and the heat exchanger fins are thin aluminum ( foil ) made and therefore requires no corrosion on the aluminum media , if an internal string leakage caused by corrosion , it is difficult to repair.

5 : The new micro-channel
    Conclusion : Energy is currently one of the important issues facing humanity , energy development and conversion of utilization has become an important national issue , and the heat exchanger is essential to the process of energy utilization equipment, have to use almost all industrial areas , chemical, metallurgy , power , transportation, aviation and aerospace sectors are particularly widespread application . In recent years, the development of new technologies and new energy development and utilization of various types of heat exchangers more and more emphasis on the industrial sector , while the heat is energy-saving measures in the more critical equipment, therefore , whether it is from industrial development , or from the efficient use of energy , heat exchanger rational design , manufacture , selection and operation are of great significance. With the development of high technology , the heat exchanger industry will usher in a more rational and more advanced types contribute to human development . More technical information please contact Lehman exchanger discussed.