Heat pipes come in several different styles:
1. Vapor Chamber Heat Pipes
Heat is transferred to the fluid using a wickless structure in vapor chamber heat pipes. They are employed in LED lighting, CPUs, and electronics. While these versions have uniform temperature distribution and the ability to cool multiple devices, they are expensive and require that the evaporator and condenser be on a single flat plane. The absence of a wick is the primary distinction between vapor chamber heat pipes and conventional heat pipes.
2. Variable Conductance Heat Pipes (VCHPs)
Variable conductance heat pipes (VCHPs) are heat-transfer systems that move heat using a working fluid and a non-condensable gas (NCG). VCHPs are used in energy systems, spacecraft, and electronics. They have benefits like high heat transfer rates, passive operation, and orientation flexibility. They do, however, come with a few drawbacks such as high manufacturing costs and a more complex design than conventional heat pipes. In contrast to a conventional heat pipe, every VCHP has a variable conductance mechanism that enables it to control the rate of heat transfer based on the difference in temperature between the evaporator and condenser sections.
3. Diode Heat Pipes
A diode heat pipe is a heat transfer device that utilizes a diode to control the heat flow direction. It comes in two types: Liquid Trap Diodes and Vapor Trap Diodes. They are used when heat flow in the reverse direction needs to be prevented. Furthermore, they are employed for the thermal control of spacecraft and electronics. High heat transfer rates and low power consumption are benefits; a narrow temperature range and sensitivity to orientation are drawbacks.
4. Thermosyphons
A thermosyphon heat pipe is a passive heat transfer device that uses gravity to circulate a working fluid, usually in a closed loop. It is frequently used in solar water heaters and for cooling electronics. Its benefits include ease of use, reliability, and affordability, while its drawbacks include a lack of flexibility and sensitivity to orientation. The mechanism used by conventional heat pipes and thermosyphons to transfer condensate from the condenser to the evaporator is the primary distinction between them. The condensate is transported by a wick in heat pipelines that uses capillary action, while gravitational forces are used in thermosyphons.
5. Loop Heat Pipe
A loop heat pipe is a form of heat transfer device that uses a two-phase mechanism to extract heat from a source and passively transmit it to a condenser or radiator. LHPs can operate against gravity and provide dependable performance over greater lengths than heat pipes can. Heat is transferred from a heat source to a heat sink efficiently and without any energy input. Unfortunately, LHPs are complex and expensive. LHPs are employed in industrial operations, electronics cooling, and thermal control of spacecraft.
6. Oscillating or Pulsating Heat Pipe
A passive, two-phase heat transfer device called an oscillating or pulsating heat pipe (PHP) moves heat through capillary action and oscillatory motion. It has uses in the automotive, aerospace, and electronics industries. Its benefits include affordability, low thermal resistance, ease of construction, and effective thermal performance. Numerous consumer electronics such as smartphones, tablets, and gaming consoles employ these heat pipes. They can help dump the heat that they produce, enhancing their functionality and lifespan. One drawback is the restricted working range. The use of oscillatory motion, which is thermally driven and combined with capillary forces, distinguishes PHP from conventional heat pipes.