HEAT EXCHANGERS !!!! Shell and Tube !!!

Ssup guys !!! Am so sorry to keep you all waiting ... but this stupid Windows Live Writer ceased to work :( ...Anywayz , am back in business , stronger as ever , so lets get into business right away !!!

Today it's about HEAT EXCHANGERS !!!
The most basic and common machine used in industries nowadays .

A Heat Exchanger , speaking in general terms is a device which " EXCHANGES HEAT " , simple right . Now as engineers we must complicate it :P .....so...A Heat Exchanger is a device *ahem* , which is used for effective heat transfer operations between two mediums , effectively , two fluids during industrial processes !!! Normally , there is no direct contact between the two media , but a thermally conductive wall exists separating them .


There are two primary classifications of heat exchangers -
1) The Parallel Flow Heat Exchanger

2) The Counter Flow Heat Exchanger

In the former , the fluids flow parallel to each other ; they enter the heat exchanger from  the same side and exit it from a common side . The latter is exactly opposite .
Always the Rebel wins the lot ;) , not surprisingly , the counter flow "rebel" Heat Exchanger is the one which gives more heat efficiency !!!

There are many types of heat exchangers , slowly and slowly i am going to highlight each one of them everyday ;)  .... today it will be The " SHELL AND TUBE " Heat Exchanger !!!

As the name itself declares , a Shell and Tube Heat Exchanger consists of an "outer" SHELL inside which a bundle of TUBES are arranged . This set of tubes is named a "Tube Bundle" . One fluid runs through these tubes , while the other flows outside the tubes BUT inside the shell . The heat is transferred from one fluid to the another through the walls of the tubes , either from tube side to shell side , or vice-versa .

But the tubes are not so simple as the one above guys :P ..... There are numerous tubes , for larger heat-exchange are , which are arranged inside the shell in patterns , either straight or in a U-shape , accordingly to the amount of heat it must exchange .

We can easily control the fluid in the tubes , but what about the one which is free-flowing in the shell ??? Hence , things called " BAFFLES" are used to direct the flow in the shell , so that the fluid in the shell is not flowing in a gingerly fashion creating pressure differences in the shell fluid .

The void like things in the right of the above picture are called "PLENUMS" , also called as "Water Boxes" , these help in pumping equal amount of the fluid in equal intervals of time in an orderly fashion .
Also depending on the number of times the fluids go around the heat exchanger , it can be diversified into ONE PASS or TWO PASS , the latter being the more efficient one .

Also they can be classified based on the phase of the fluids used in the shell and tubes . If the fluid used in each of them is in the same phase it is christened as a " SINGLE PHASE " Heat Exchanger . If the fluid in the shell is in a different phase than that of the tubes , it is called a " TWO PHASE " Heat Exchanger .

For an Heat Exchanger to be an efficient one , it must transfer heat well . Thus , the tube material in particular must have good thermal conductivity . Also , it must be able to resist thermal stresses which arise due to the difference in the temperatures of the two fluids in contact with the walls of the tube , thus repeatedly expanding and contracting .
Hence , the material must be Strong , Thermally Conductive and Corrosion resistant . Here comes the concept of " SUPER-ALLOYS " . These are used to make the tubes of the heat exchanger.
Ex:- Inconel , Hastelloy ,etc .
Stainless Steel and Carbon Steel can also be used , but they cannot compete with the above super-alloys in terms of efficiency developed .


ADVANTAGES :
1) used in oil refineries , and other large scale industrial processes

2) the BOILER used in locomotive engines is actually a modified heat exchanger , so is the CONDENSER used in refrigeration. They are essentially  TWO PHASE SHELL AND TUBE HEAT EXCHANGERS !!!

3) used in waste water treatment

4) the nuclear power plant's "Pressurized Water Reactors" is actually a TWO PHASE , U TUBE , SHELL AND TUBE HEAT EXCHANGER .

5) used in aircrafts . The Heat Exchanger takes the heat from the engine's oil system and showers it on the fuel , thus , leading to better fuel economy and an absence of using expensive anti-refrigerants in the fuel .

6) maybe the most common use of an heat exchanger is the RADIATOR !!!


Well people , thats about heat exchangers , or i must say a part of it :P ... there is more to come about the other types in the following posts !!!
BUT , i would want to say that the world's most efficient heat exchanger is INSIDE you !!!!
Believe me , thats true !!!



your LUNGS !!!!



just finished reading THE LOST SYMBOL !!! maybe this is what Dan Brown meant by saying YOUR BODY IS YOUR TEMPLE !!! Isn't nature wonderful !!!