What is heat pipe PDF?
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].
How does a heat pipe work?
The heat boils the fluid and pushes the fluid vapor to the colder region of the heat pipe. The colder region, which is typically coupled to a heat sink, is known as “the Condenser”. The fluid gives up its latent heat and condenses back to a liquid, and is again absorbed in the wick structure.
What is thermosyphon heat pipe?
This is a natural fluid circulation heat pipe which has no wick material presence. It is a simple heat pipe consisting of a sealed vessel charged with working fluid under a vacuum condition. It is made up of evaporator and condenser sections, sometimes with adiabatic section in between them.
How do you calculate the heat transfer of a heat pipe?
Effectiveness of a heat pipe can be represented by a system of thermal resistance. The thermal resistance ? can be represented by ? ? = ? − ? ? ? ∘ C / W . ( 1 ) The overall heat transfer coefficient, ℎ of the heat pipe can be given by ? ℎ = ? ? ? − ? ? W / m 2 ⋅ ∘ C .
What is heat pipe efficiency?
According to the experimental results, the optimum condition of heat pipe is when nanoparticles being at 1.0 wt. %. Under this condition, the thermal efficiency is 16.8%, which is higher than that of heat pipe charged with distilled water. The charge amount can be decreased from 60% to 20%.
How does a pulsating heat pipe work?
While standard heat pipes usually rely on a wick structure to return the fluid to the heat source, a pulsating heat pipe consists of thin channels with up to several dozens of turns that are partially filled with liquid and evacuated. Due to the surface tension, segments consisting of fluid and vapor are formed.
What is used in heat pipe?
The heat pipes for HVAC applications are usually made of copper tubes, aluminum fins.. Different working fluids are used to suit various temperature ranges. In the case of heat pipes for HVAC applications, commercially available refrigerants are normally used as the working fluid.
Why is thermosyphon used?
Thermosiphoning is used for circulation of liquids and volatile gases in heating and cooling applications such as heat pumps, water heaters, boilers and furnaces. Thermosiphoning also occurs across air temperature gradients such as those utilized in a wood fire chimney or solar chimney.
What liquid is used in heat pipes?
water
Working Fluids The most common heat pipe working fluid is water for an operating temperature range from 1°C to 325°C. Low temperature heat pipes use fluids such as ammonia and nitrogen. High temperature heat pipes utilize cesium, potassium, NaK and sodium (873–1,473°K).
What is oscillating heat pipe?
Oscillating heat pipes (OHPs) use pressure-driven, two-phase fluid flow to rapidly transfer heat between heat sources and heat sinks. They can be built in materials, fluids, shapes, and sizes that are not possible with conventional capillary-driven heat pipes or vapor chambers.
What is the pressure inside a heat pipe?
The practical upper-temperature limit for copper/water heat pipes is roughly 150°C, and is set by the maximum allowable stresses in the copper envelope; see Figure 6. At 150°C, the saturated water vapor pressure is 69 psia (477 kPa).
What is the principle of thermosyphon?
What is a Thermosiphon? A thermosiphon is a passively driven thermal management device that utilizes the motive forces of natural convection and conduction. The device uses these forces to create a cyclic fluid flow from areas of high heat to low heat and back.
What is thermosyphon filter?
Thermosyphon filter is an ON LINE Transformer Oil Preservation system for Power Transformers .. The system basically consist of a container containing Adsorbant (Normally Activated alumina) which has very high moisture absorbtion capacity.
How is ammonia used in cooling?
In the refrigerant cycle, ammonia gas undergoes compression through the application of the compressor. This causes the gas to heat up under pressurization. The gas moves into the condenser where heat is dissipated in the coils. This condenses the ammonia, changing it into liquid form, but still at high pressure.
Where are heat pipes used?
Nowadays heat pipes are used in several applications, where one has limited space and the necessity of a high heat flux. Of course it is still in use in space applications, but it is also used in heat transfer systems, cooling of computers, cell phones and cooling of solar collectors.