eat exchanger is any device that is used to transfer heat from one fluid to another and the two fluid must be hot and cold fluid
Example:car radiator
Direction of flow
1. Parallel flow
2. Counter flow Heat exchanger
3. Cross flow Heat exchanger
Design of Heat exchanger
1. Concentration flow
2. Shell and tube heat exchanger
3. Compact Heat exchanger
Nature of Heat exchanger
1. Direct flow Heat exchanger
2. Indirect flow Heat exchanger
They one take in Heat is called a cold fluid and the heat carrier is called hot fluid. In hear exchanger, the temperature of each fluid changes as it passes through the heat exchanger hence the temperature of the diving wall between the fluid also changes along the length of the exchanger. Hear exchanger Design is handled by the speciality and professional. The engineers need acquittance with the heat transfer design principles to evaluate bids and to detect operating problems
Examples:
Automobile radiator
Oil cooler of heat engine
Condenser
Types of heat exchanger
Classification based on nature of heat exchanger process
1. Direct contact heat exchanger or open,the exchanger of heat or energy take place by Direct mixing of the hot and cols fluid. This Type of heat exchanger utilized where mixing of the two fluid is desired and harmless
Example:
Cooling tower
Contact feed heater
Jet condenser
2. Indirect contact hear exchanger this type of heat exchanger the hot fluid and cold fluid is not allowed to mixes rather the heat transfer is through the wall that separate the two fluids.the two type is
Regenerate
Recuperate
N.B in the Regenerator heat exchanger the hot and cold fluid pass alternatively through a space containing solid particles (matrix).this particles providing alternatively a sink and a sources for heat flow. The performance of a Regenerator heat exchanger is affected by the following factors,
1. Heat capacity of the Regenerating material
2. Rate of heat absorption
3. The release of heat
Recuperatator heat exchanger are commonly used heat exchanger the fluid are separated by a wall of copper aluminum,alloy and brass. The heat transfer process consists of convention with the fluid and the wall and conduction between the fluid and the wall
Example of Recuperatator
Condenser
Evaporator of refractor system
Classification of heat exchanger based on directions of fluid flow
[ ] Parel flow
[ ] Counter-current flow heat exchanger
[ ] Cross flow heat exchanger
1. Parel flow heat exchanger just as the name suggests the two fluid hot and cold fluid travel in this same direction. The two fluid stream enters at one end and leaves at the other end
2. Counter-current heat exchanger, the two fluid hot and cold cross one another in space usually at 90⁰ or right angles. Hot fluid flows in a separate tube and there is no mixing of the fluid streams Example:cooling of refrigeration system, automobile radiator
Classification of the heat exchanger based on design and constructional
1. Concentrate tube heat exchanger, here two Concentrate tube is used each carrying one of the fluids. The direction of the flow maybe Parel or Counter-current. The effectiveness of the heat exchanger is increase by using swirling flow
2. Shell and tube heat exchanger
3. Compact heat exchanger
Heat exchanger analysis
Recall the normal heat equation
Q=MCp^T
WHERE Q= Quality of heat transferred
M=mass flow rate kg/s
Cp=specific heat capacity of fluid
At constant pressure j/kg⁰c
^T=Temperature rise of fluid. across heat exchanger
Let use hand c to repent hot and cold fluid. Assuming there is no heat loss to the surrounding and potential and kinetic change are negligible .
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