Heat exchangers are the gadgets which are utilized to trade warm between at least two liquids which are at various temperature. Warmth exchangers are real gadgets utilized in building
FLOW OF FLUID:
Before concentrate the sort of warmth exchangers we ought to have appropriate information of the kind of stream utilized in warmth exchangers, in light of the fact that diverse sorts of streams are utilized in warmth exchangers as per our necessity. These streams are parallel stream, counter stream and cross stream. In these three kinds of stream the general bearing of hot and chilly liquid changes as it were. The liquids might be isolated by a plane divider or by concentric cylinder called as twofold pipe.
In the event that both the liquids i.e. hot and cool liquid goes into the warmth exchangers at same end and afterward ventures out parallel to one another till the external end i.e. both liquid moves same way then it is known as parallel stream.
At the point when both the liquid goes into the warmth exchangers at inverse course yet additionally moves parallel to one another then it is known as counter stream.
In this stream both the liquids moves at right point to one another through the warmth exchanger.
For better proficiency the warmth exchangers are characterizes to boost the surface territory of contact between two liquids and limit the stream opposition. From over three cases counter stream warm exchangers is most proficient among all these on the grounds that it can exchange high measure of warmth and it has higher temperature distinction along its unit length.
The different types of heat exchangers are classified in three main categories.
- Direct Transfer type Heat Exchanger
- Direct Contact type Heat Exchanger
- Regenerative or Storage type of Heat Exchanger
A.) Direct Transfer type Heat Exchanger:
These are otherwise called recuperators warm exchangers. In which the liquids are isolated by a divider i.e. both hot and chilly liquid don’t come into contact with one another. The divider can be a straightforward divider or cylinder or some unpredictable structure like balances and astounds. Surface warmth exchangers are all the more usually utilized name of these warmth exchangers they can be developed with substantial warmth move surfaces in a generally little volume and are reasonable for warming, cooling, dissipating and gathering applications. The warmth exchangers come in these classifications are
- Surface Condenser
- Oil Cooler
- Air Preheater
- Shell and Tube Heat Exchanger
- Plate Heat Exchanger
- Plate and Shell Heat Exchanger
- Plate Fin Heat Exchanger
- Dynamic Scraped Surface Heat Exchanger
- Pillow plate heat exchanger
Surface condenser is a sort of warmth exchanger for the most part utilized in warm power stations. These are water cooled condensers and introduced at the exit of the steam from steam turbine. It changes over steam from its vapor shape to its fluid state at a weight lower than environment weight. Where cooling tower can’t introduce we favor surface condenser on that put. At some point air additionally use as cooling liquid when watersupply isn’t adequate, yet air cooled condenser are not all that effective in light of the fact that they can’t accomplish wanted steam weight and temperature at outlet. Surface condensers have different applications in various businesses additionally where single liquid is recycles over and over by gathering and warming it.
It is a mechanical gadget used to diminish the vitality utilization by preheating of the liquid before going into the boilers. It is a kind of warmth exchanger which is for the most part utilized in boilers, control plant and refrigeration and cooling. In every one of these gadgets economizer may have distinctive in development yet the fundamental capacity is same. Economizer comprises of a few cylinders in which one liquid is disregarding the cylinders. In the event of steam boilers cooled liquid i.e. water experiences these cylinders previously going into the kettle and hot pipe gases which are discharged through the stack streams over these cylinders because of this the temperature of the channel water increments marginally before bubbling. Because of economizer we can spare fuel utilization and streamline our procedure by utilizing waste warmth.
Oil cooler is another sort of warmth exchanger in which high temperature oil is cooled by utilizing some coolant. For the most part water is utilized as cooling liquid because of simple accessibility. This is for the most part a twofold pipe course of action. In which both hot and cool liquid pass at the same time. It is most basic and effortlessly worked warmth exchanger. The stream can be parallel or might be counter according to the prerequisite. One liquid enters through internal pipe and second one is through external pipe. As the oil moves through one pipe the water moves through second pipe this procedure constantly rehashed.
As name propose air preheater use to pre warm the air before further use to build the warm effectiveness of the gadget. It is a kind of warmth exchanger. The warmth lost from by the pipe gas use to pre warm the air before going into the heater in the event of warm power plant. The air preheater warm exchanger is introduced between the economizer and smokestack. This is a cylindrical structure. The chilly outside air going through cylinders and hot vent gases ignore these cylinders and trade warmth to warm within cool air before going into the heater.
SHELL AND TUBE HEAT EXCHANGER:
Shell and Tube warm exchanger is utilized for high weight applications. It works typically at 30 bar weight and temperature more noteworthy than 260oC. It has tough structure to support the high load and at high weight. It comprises of number of cylinders which are masterminded longitudinally in the shell. One liquid is going through these cylinders and the other liquid ignoring them through shell opening. Every one of the cylinders are associated with one channel and one outlet through which first liquid is pass, this can be hot or chilly. The second is ignoring these cylinders, astounds are given inside the shell to expand the contact of second liquid (which streams inside the shell) with cylinders. The shell and cylinder have different shapes and structure yet the fundamental capacity of various kinds are normal. The cylinder width ought to be inside legitimate limit not very little not very extensive, in light of the fact that little distance across cylinders experience issues in cleaning of fouling yet little cylinders make warm exchanger efficient and smaller. The confounds utilized in shell coordinate the liquid stream over the cylinders. They likewise keep the cylinders from vibrating. Diverse structures of perplexes are utilized according to necessities. Astounds give disturbance in the liquid stream inside the shell which results in higher warmth exchange coefficient for the external cylinders surface.
PLATE HEAT EXCHANGERS:
This is the sort of warmth exchanger. This comprises of thin plates having parallel cross-sectional territory. These plates are isolated by a little separation. The surface territory of these plates is very expansive in light of the fact that substantial surface zone rules huge warmth exchange through these cylinders. These plates are produced by utilizing gasket and brazing and made up of tempered steel. Because of substantial surface region of plates this warmth exchanger is progressively powerful as contrast with shell and cylinder warm exchanger and it is for the most part utilized in the refrigeration applications. Gasket coordinates the streams between exchange plates and averts outside spillage. Gaskets are masterminded each stream to moderate between interchange plates. The sides of the considerable number of plates have an opening for the death of liquid, for extraction of warmth from the plates when liquid courses through it. This is done for the most part in intermittent way according to the prerequisite.
PLATE AND SHELL HEAT EXCANGER:
It is blend of the two plates with both shell and cylinders warm exchangers. Plates are mounted in a shell. A progression of plates are consolidating for better warmth exchange. These plates are comprised of hardened steel of some top notch materials. These plates are hanged vertically in shell. These plates are ridged to give purposes of help for expanding heat exchange. The plates utilized are roundabout in cross-area and welded together to fit in the shell. This innovation offers high warmth exchange at high temperature and weight. Gaskets are utilized here; this is the fundamental favorable position of plate and shell warm exchanger since it gives a security against spillage at high weight and temperature. The full pack of plates amassed into an external shell that makes an auxiliary stream way through shell side.
PLATE FIN HEAT EXCHANGER:
This warmth exchanger comprises of a pack of fines which are organized in straight, counterbalance and in wavy frame to build the adequacy of the gadget. The stream can be cross stream or counter stream according to our prerequisites. For better warmth exchange the plate and blade warm exchanger is comprised of aluminum combinations. Aluminum compounds decrease the heaviness of entire unit. It is utilized in low temperature application like gaseous petrol, helium, oxygen and transport businesses, for example, engines and airplane motors. It has high warmth exchange effectiveness because of the vast warmth exchange region of fines and effortlessly withstand at high weight. Now and again stopping up happens on the grounds that the pathway is extremely limited and cleaning of this obstructing is very troublesome.