Contact resistance is generally encountered in thermal engineering whenever a concentrated heat source is in feel with a larger heat conducting surface. This phenomenon extends also to galvanic current and mass transfer problems. The focus of this record is on thermal feel resistance, which often appears as a bottleneck in heat management, and is of relevance in applications such as integrated circuits and laser heating.
What is the thermal feel resistance?
Nuclear Reactor
In contacting bodies, real interaction between two surfaces occurs only over wee contacts. The actual area of contact, i.e., the total area of all microcontacts, is typically less than 2% of the nominal feel area. When heat flows in/out of a body straight through this small area, the heat flux lines are correspondingly constricted/spread apart and the resulting thermal resistance is referred to as constriction/spreading resistance. This resistance is defined as the inequity between the temperature of a heat source/microcontact and the temperature of a heat sink far from it divided by the total heat flow rate straight through the feel area. The thermal feel resistance (Tcr) is a combination of spreading and constriction resistances and the resistance of the gas which fills the gap between the two contacting bodies, if applicable.
Thermal feel resistance plays a vital role in the produce of numerous thermal, electrical, and electronic devices and systems. Electronic equipment, aircraft structural joints, surface thermocouples, boundary lubrication, nuclear reactors, biomedical industries, and cryogenic liquid storage devices are only a few examples of such systems.
Contact Resistance at a porous medium-solid surface interface
The term "porous medium"describes any material consisting of a solid matrix with interconnected pores. The interconnectedness of the pores allows the flow of one or more fluids straight through the material. Recently, high porosity open-cell media such as metal foams and fibrous media have started to receive more attention. These materials are great candidates for a wide variety of thermofluid applications such as microelectronics cooling, fuel cells, and contract heat exchangers. Due to high porosity of these materials, the total feel area is much smaller than the feel area between solid contacting surfaces. The geometric complexity and the random orientation of solid ligaments in high porosity materials complicate the estimate of Tcr at their interface with a surface.
How prominent is the thermal feel resistance?
Thermal feel resistance is a function of mechanical and thermal properties and surface characteristic of the contacting bodies as well as feel pressure and temperature.
Predicting converyance phenomena in high porosity media plays a key role in the optimization of water and thermal supervision for a variety of industrial applications such as gas diffusion layers in fuel cells and metal foam-based heat exchangers. Thermal feel resistance contributes a large part of the total thermal resistance in high porosity materials. For instance, Tcr contains between 65 and 90% of the total resistance in Toray gas diffusion layers.
Reducing the roughness and out-of-flatness of the contacting surfaces, addition the feel pressure and employing high conductive materials can help us to sell out the thermal feel resistance.
Thermal perceive Resistance