Fundamentals of Heat Pipes With Applications and Types
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A heat pipe heat exchanger is a simple device which is made use of to transfer heat from one location to another, using an evaporation-condensation cycle.
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![A heat pipe heat exchanger is a simple device which is
made use of to transfer heat from one location to another,
using an evaporation-condensation cycle.
Heat pipes are referred to as the "superconductors" of heat
due to their fast transfer capability with low heat loss[1].
What is a Heat Pipe?](https://image.slidesharecdn.com/final-heatpipe-180510090254/85/Fundamentals-of-Heat-Pipes-With-Applications-and-Types-2-320.jpg)
![Working Principle
The heat input region of the heat pipe is called evaporator(heat
source), the cooling region is called condenser (heat sink).
In between the evaporator and condenser regions, there may be
an adiabatic region[1].](https://image.slidesharecdn.com/final-heatpipe-180510090254/85/Fundamentals-of-Heat-Pipes-With-Applications-and-Types-3-320.jpg)
![1.Container
The function of the container is to isolate the working fluid from
the outside environment.
Selection of the container material depends on
many factors. These are as follows[2]:
Compatibility (both with working fluid and external
environment)
Strength to weight ratio
Thermal conductivity
Ease of fabrication, including welding, machine ability and
ductility
Porosity
Wettability](https://image.slidesharecdn.com/final-heatpipe-180510090254/85/Fundamentals-of-Heat-Pipes-With-Applications-and-Types-5-320.jpg)
![2.Working Fluid
The prime requirements are[2]:
1. Compatibility with wick and wall material
2. Good thermal stability
3. Wettability of wick and wall materials
4. Vapor pressure not too high or low over the operating temperature
range
5. High latent heat
6. High thermal conductivity
7. Low liquid and vapor viscosities
8. High surface tension
9. Acceptable freezing](https://image.slidesharecdn.com/final-heatpipe-180510090254/85/Fundamentals-of-Heat-Pipes-With-Applications-and-Types-6-320.jpg)
![3.Wick Structure
1. It is a porous structure made of materials like steel, aluminium, nickel or copper
in various ranges of pore sizes.
2. The prime purpose of the wick is to generate capillary pressure to transport the
working fluid from the condenser to the evaporator.
3. It must also be able to distribute the liquid around the evaporator section to any
area where heat is likely to be received by the heat pipe.
4. The maximum capillary head generated by a wick increases with decrease in pore
size.
5. Other necessary properties of the wick are compatibility with the working fluid
and wettability [2].](https://image.slidesharecdn.com/final-heatpipe-180510090254/85/Fundamentals-of-Heat-Pipes-With-Applications-and-Types-7-320.jpg)
![Heat pipe withstands more than one heat transfer limitation
such as vapor-pressure, sonic, entrainment, capillary and
boiling limitations. These limitations are depending on the
working fluid, wick structure, dimensions of the heat pipe and
the heat pipe operational temperature. The driving mechanism
in the heat pipe is the heat input, Q, which is related to the
mass flow rate of the working fluid and latent heat of
vaporization( hfg )[4].](https://image.slidesharecdn.com/final-heatpipe-180510090254/85/Fundamentals-of-Heat-Pipes-With-Applications-and-Types-12-320.jpg)
Fundamentals of Heat Pipes With Applications and Types
- 2. A heat pipe heat exchanger is a simple device which is made use of to transfer heat from one location to another, using an evaporation-condensation cycle. Heat pipes are referred to as the "superconductors" of heat due to their fast transfer capability with low heat loss[1]. What is a Heat Pipe?
- 3. Working Principle The heat input region of the heat pipe is called evaporator(heat source), the cooling region is called condenser (heat sink). In between the evaporator and condenser regions, there may be an adiabatic region[1].
- 4. Container Working fluid Wick or Capillary structure
- 5. 1.Container The function of the container is to isolate the working fluid from the outside environment. Selection of the container material depends on many factors. These are as follows[2]: Compatibility (both with working fluid and external environment) Strength to weight ratio Thermal conductivity Ease of fabrication, including welding, machine ability and ductility Porosity Wettability
- 6. 2.Working Fluid The prime requirements are[2]: 1. Compatibility with wick and wall material 2. Good thermal stability 3. Wettability of wick and wall materials 4. Vapor pressure not too high or low over the operating temperature range 5. High latent heat 6. High thermal conductivity 7. Low liquid and vapor viscosities 8. High surface tension 9. Acceptable freezing
- 7. 3.Wick Structure 1. It is a porous structure made of materials like steel, aluminium, nickel or copper in various ranges of pore sizes. 2. The prime purpose of the wick is to generate capillary pressure to transport the working fluid from the condenser to the evaporator. 3. It must also be able to distribute the liquid around the evaporator section to any area where heat is likely to be received by the heat pipe. 4. The maximum capillary head generated by a wick increases with decrease in pore size. 5. Other necessary properties of the wick are compatibility with the working fluid and wettability [2].
- 8. Electronics cooling Solar energy Heat exchanger Dehumidifier production tools, medicine and human-Other applications body temperature control, engines and automotive industry.
- 9. Thermosyphon Loop heat pipe Oscillating heat pipe Variable conductance Rotating and Revolving
- 10. flexibility in operation and application, Are very efficient in transporting heat even under small temperature difference, Requires no mechanical or electrical input, Are virtually maintenance free, Provide lower operating costs, Last a very long time, Are environmentally safe.
- 12. Heat pipe withstands more than one heat transfer limitation such as vapor-pressure, sonic, entrainment, capillary and boiling limitations. These limitations are depending on the working fluid, wick structure, dimensions of the heat pipe and the heat pipe operational temperature. The driving mechanism in the heat pipe is the heat input, Q, which is related to the mass flow rate of the working fluid and latent heat of vaporization( hfg )[4].
- 18. 1-Vijayakumar,P., Sajairaj,S., and Santhoshkumar,R."Review on Conventional, Modern Heat Pipes and Its Applications "International Research Journal of Engineering and Technology,Vol.3,pp.513-518,2016. 2-Bahman,Z." Heat Pipe Design and Technology": Modern Applications for Practical thermal Management"2011. 2-Ong,K."Heat pipes"Jurutera.pp.16-18,2008. 4-Hussain,H&Anwar,A. "Comparison Between a Heat Pipe and a Thermosyphon1 Performance with Variable Evaporator Length Journal of Al Rafdain Engineering,Vol.21,No.2,pp.1-12,2011.