Classification of heat exchangers

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Heat Exchangers :-

A heat exchangers is a device, which transfers thermal energy between two fluids at different temperatures. the most of the thermal engineering application, boths of the fluid are in motion and mattianede of heat transfer is convection .

Examples are automobile radiators, condenser coil in refrigerator, air conditioner, solars water heater, chemical industries, domestic boilers, oil coolers in heat engine, milk chillers in pasteurizing plant.

Applications of Heat Exchanger :

i) The condenser coil in a refrigerator.
ii) The evaporator of Domestic Refrigerator .
iii) The condenser used in cooling tower.
iv) Domestic boiler.
v) The solar water heater .
vi) Automobile radiator .
vii) The foods industry .
vii) Dairy product industry .

Classification of heat exchangers :-

1. Classifications of according to construction :-

*The tubular heat exchangers .
*Plates of the heat exchangers.
*The extended surface heat exchangers .

Classification according to transfer process :-

*The indirect contact heat exchangers .
*The direct contact heat exchangers .

3.Classification according to flow arrangement :-

*Parallel flow exchangers .
*The flow of counter heat exchangers .
*The cross flow heat exchangers .

4.Classification according to pass arrangement :-

*The single pass arrangement .
*The multi-pass arrangement .

5. Classification according to Physical state of the fluids :-

*Condensers .
*Evaporators .

*Shell and tube heat exchanger :–

*This is the most common types of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications .
*It consists of buddle of round of tube placed inside cylindrical shell with tube axis parallel to that of shell .
*The through is one fluid is carried a bundle of tubes enclosed by shell .
*The through is other fluids forced the shell and the surface of tubes flow over the outside. The heat is exchanged take place between hot fluid and cold fluid .
*Baffles are used to direct the shell-side fluid flow along tube held & to hold tubes in position prevent the effects of vibration .

*Shell and coil type of heat exchanger :-

*Shell and coil type heat exchanger consist of helical coil .
*The helical coil is compact in shell .
*Cooling medium is passed thought he coil and liquid to be cooled is passed from top of shell.
The cooled liquid is taken out from bottom of shell.
*Generally in this type of heat exchanger counter flow arrangement is used.

*Plate types of heat exchanger :-

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*It is consists of a series of a closely spaced parallel plates with fins held in betweens .
*The fins have the dual purpose of the holding the plates together & of forming a secondary (fin) surface for heat transfer.
* Two fluids plates separate the which is flow through passages alternately formed between the plates.
*The typical of cross flow boths fluid unmixed arrangements as shown in figure, in which heat is transfer between fluids “A” and fluids “B”.
*Counters flows or the parallel flows arranged of can also be possibles .
*The plate-fin heat exchanger is widely used in many industries, including the aerospace industry for its compact size and lightweight properties.

*Double pipe heat exchanger (Pipe in pipe heat exchanger) :-

*It is one of the simplest and cheapest types of heat exchanger.
*The name suggests the consists of two pipes, one within the other.
*One fluid flows through the inner pipe while the other flows through the outer pipe, which surrounds the inner pipe.
*Usually the hotter fluid flows through the inter pipe.
*The designs use inner tubes /pipes fitted with the longitudinal fins to increase the heat transfer area and improve heat transfer.

Heat exchanger use for :-

1) Mills Chiller Plant : Plate type heat exchanger Justification :-

a) Non-reactive material.
b) The leak proof joints.
c) Not mixing of two fluids .
d) Non-toxic material .
e) Non corrosive material.

2) Radiator of an Automobile :- Plate and tube type Heat Exchanger (Air Water Convective Radiator)

Justification :-

a) It is used to cool engine of automobile.
b) The water flow though the jacket along with the engine and carried away from the heat by convection .
c) This water enters into radiator where it gives it’s heat to air of atmosphere which is passover water tubes. Though plates.

Classification of heat exchanger and their applications :-

1. Nature of heat exchange process :-

Heat exchangers, on the basis of nature of heat exchange process are classified as follows :-

(a) (i) The direct contact (or open) heat exchangers :-

Examples :-
(i) The Cooling ,tower.
(ii) Jet, condensers.
(iii)The direct contact.

(ii) The indirect contact heat exchangers :-

(a) Regenerators :-

Examples :-
(i) IC, engines and gas turbines.
(ii) The open hearth and glass melting furnaces.
(iii) The air heaters of blast furnaces.

(b) The recuperators :-

Examples :-

(i) The automobile radiators.
(ii) The oil Coolers Intercooler preheated, Superheaters, condensers, surface feed heaters of a steam power plant & economiser. (iii) Milk chiller of Pasteurizing plant.
(iv)The evaporator of an ice plant.

2. Relative direction of fluid motion :-

According to the relative directions of two d into the following 3 categories are :-

(i) The parallel-flows or the unidirectional flows :-

Examples :-

Oil coolers, oil heaters, the water heaters etc.

(ii) The counter-flows :-

Examples :-

The cooling unit of refrigeration of the system etc.

(iii) The cross-flows :-

Examples :-

The automobile radiator etc.

3. The design and constructional features :-

The basis of design & constructional features, the heat exchangers are classified as under :-

(i) Concentric tubes.
(ii) Shell & tubes.
(iii) Multiple shelf and tube passes.
(iv) The compact heat exchangers :-
Example :- Plate-fin, flattened fin tubes exchangers etc.