Heat Pipes

SEMINAR SEMINAR ON ON “HEAT “HEAT

PIPES”PIPES”

PRESENTED BY:PRESENTED BY:

[email protected]@gmail.comm

WHAT IS A HEAT PIPEWHAT IS A HEAT PIPE

Heat pipe is a simple device that can Heat pipe is a simple device that can quickly transfer heat from one point to quickly transfer heat from one point to another. another.

They are often referred to as the They are often referred to as the "superconductors" of heat as they "superconductors" of heat as they possess an extra ordinary heat transfer possess an extra ordinary heat transfer capacity & rate with almost no heat loss. capacity & rate with almost no heat loss.

The idea of heat pipes was first suggested by The idea of heat pipes was first suggested by R.S.Gaugler in 1942.In 1963, G.M.Grover R.S.Gaugler in 1942.In 1963, G.M.Grover invented its remarkable properties & serious invented its remarkable properties & serious development began.development began.

CONSTRUCTIONCONSTRUCTION

It consists of a sealed hollow tubeIt consists of a sealed hollow tubeusing thermoconductive metal such asusing thermoconductive metal such as copper or aluminium.copper or aluminium. On the internal side of the tube's On the internal side of the tube's side-walls a wick structure exerts aside-walls a wick structure exerts a capillary force.capillary force. It is similar to a thermosyphon. TheIt is similar to a thermosyphon. The pipe Consists of a small amount of pipe Consists of a small amount of coolant and the rest of the pipe is filledcoolant and the rest of the pipe is filled with vapour phase of the working fluid.with vapour phase of the working fluid.

DESIGN CONSIDERATIONSDESIGN CONSIDERATIONS

Three basic components of a heat Three basic components of a heat pipe are: pipe are:

the container the container the working fluid the working fluid the wick or capillary structurethe wick or capillary structure

CONTAINERCONTAINER The function of the container is to The function of the container is to

isolate the working fluid from the isolate the working fluid from the outside environment. outside environment.

It has to therefore be leak-proof, It has to therefore be leak-proof, maintain the pressure differential maintain the pressure differential across its walls, and enable transfer across its walls, and enable transfer of heat to take place from and into of heat to take place from and into the working fluid. the working fluid.

Selection of the container material Selection of the container material depends on Compatibility (both with depends on Compatibility (both with working fluid and external working fluid and external environment) ,Strength to weight environment) ,Strength to weight ratio ,Thermal conductivity ,Porosityratio ,Thermal conductivity ,Porosity

Working fluidWorking fluid The pipe contains a small quantity of a The pipe contains a small quantity of a

"working fluid" or coolant (such as water, "working fluid" or coolant (such as water, ethanol or mercury) with the remainder of the ethanol or mercury) with the remainder of the pipe being filled with vapour phase of the pipe being filled with vapour phase of the working fluid. working fluid.

The materials and coolant chosen depends on The materials and coolant chosen depends on the temperature conditions in which the heat the temperature conditions in which the heat pipe must operate, with coolants ranging from pipe must operate, with coolants ranging from liquid helium for extremely low temperature liquid helium for extremely low temperature applications to mercury for high temperature applications to mercury for high temperature conditions. However, the vast majority of heat conditions. However, the vast majority of heat pipes uses either ammonia or water as workingpipes uses either ammonia or water as working fluid.fluid.

Wick or Capillary StructureWick or Capillary Structure The prime purpose of the The prime purpose of the

wick is to generate capillary wick is to generate capillary pressure to transport the pressure to transport the working fluid from the working fluid from the condenser to the condenser to the evaporator. evaporator.

This is typically a sintered This is typically a sintered metal powder or a series of metal powder or a series of grooves parallel to the tube grooves parallel to the tube axis, but it may in principle axis, but it may in principle be any material capable of be any material capable of soaking up the coolant. soaking up the coolant.

WorkingWorking Inside the container is a Inside the container is a

liquid under its own liquid under its own pressure, that enters the pressure, that enters the pores of the capillary pores of the capillary material, wetting all material, wetting all internal surfacesinternal surfaces. .

Applying heat at any point Applying heat at any point along the surface of the along the surface of the heat pipe causes the liquid heat pipe causes the liquid at that point to boil and at that point to boil and enter a vapor state.When enter a vapor state.When that happens,the liquid that happens,the liquid picks up the latent heat of picks up the latent heat of vaporization.vaporization.

Contd…Contd…

The gas, which then has a higher The gas, which then has a higher pressure, moves inside the sealed pressure, moves inside the sealed container to a colder location where container to a colder location where it condenses. it condenses.

Thus, the gas gives up the latent Thus, the gas gives up the latent heat of vaporization and moves heat heat of vaporization and moves heat from the input to the output end of from the input to the output end of the heat pipe. the heat pipe.

Contd…Contd… Heat pipes have an effectiveHeat pipes have an effective thermal conductivity manythermal conductivity many times that of copper. times that of copper. The heat transfer or transportThe heat transfer or transport capacity of a heat pipe is capacity of a heat pipe is Specified by its " Axial Power Specified by its " Axial Power Rating (APR)“.Rating (APR)“. . It is the energy moving axially. It is the energy moving axially along the pipe. The larger the heat pipe along the pipe. The larger the heat pipe

diameter, greater is the APR. Similarly, longer diameter, greater is the APR. Similarly, longer the heat pipe lesser is the APR. Heat pipes the heat pipe lesser is the APR. Heat pipes can be built in almost any size and shape. can be built in almost any size and shape.

ADVANTAGESADVANTAGES

The advantage of heat pipes is their great The advantage of heat pipes is their great efficiency in transferring heat. They are efficiency in transferring heat. They are actually a vastly better heat conductor actually a vastly better heat conductor than an equivalent cross-section of solid than an equivalent cross-section of solid copper. Heat flows of more than copper. Heat flows of more than 230MW/m^2 have been recorded (4 times 230MW/m^2 have been recorded (4 times the heat flow from the surface of the sun).the heat flow from the surface of the sun).

Heat pipes contain no moving parts and Heat pipes contain no moving parts and typically require no maintenance.typically require no maintenance.

relatively space efficient.relatively space efficient.

LIMITATIONSLIMITATIONS below a certain temperature, the below a certain temperature, the

working fluid will not vaporize at all, working fluid will not vaporize at all, and the thermal conductivity will be and the thermal conductivity will be reduced to that of the solid metal reduced to that of the solid metal casing .casing .

When heated above a certain When heated above a certain temperature, all of the working fluid in temperature, all of the working fluid in the heat pipe will vaporize and the the heat pipe will vaporize and the condensation process will cease to condensation process will cease to occur; in such conditions thermal occur; in such conditions thermal conductivity will be reduced to that of conductivity will be reduced to that of the solid metal casing.the solid metal casing.

APPLICATIONSAPPLICATIONS

Heat pipes are used in a wide range of Heat pipes are used in a wide range of products like air-conditioners, products like air-conditioners, refrigerators, heat exchangers, transistors, refrigerators, heat exchangers, transistors, capacitors, space staction,etc. capacitors, space staction,etc.

Heat pipes are also used in laptops to Heat pipes are also used in laptops to reduce the working temperature for betterreduce the working temperature for better

efficiency. efficiency. VAPIPE is recent developed heat pipe used VAPIPE is recent developed heat pipe used

in a car engine to vaporise gasoline by in a car engine to vaporise gasoline by exhaust gases .exhaust gases .

THANK YOU….THANK YOU….