mass transfer is the process by which a mechanical device is used to move a fluid or gas to transfer heat.
the process by which a mechanical device is used to move a fluid or gas to transfer heat?
mass transfer
heat convection occurs when bulk flow of a fluid (gas or liquid) carries heat along with the flow of matter in the fluid. the flow of fluid may be forced by external processes, or sometimes (in gravitational fields) by buoyancy forces caused when thermal energy expands the fluid (for example in a fire plume), thus influencing its own transfer. the latter process is often called "natural convection". all convective processes also move heat partly by diffusion, as well. another form of convection is forced convection. in this case the fluid is forced to flow by use of a pump, fan or other mechanical means.
heat transfer
heat pipes are a heat recovery device that use a multi-phase process to transfer heat from one airstream to another. heat is transferred using an evaporator and condenser within a wicked, sealed pipe containing a fluid which undergoes constant phase change to transfer heat. the fluid within the pipes changes from a fluid to a gas in the evaporator section, absorbing the thermal energy from the warm airstream. the gas condenses back to a fluid in the condenser section where the thermal energy is dissipated into the cooler airstream raising the temperature. the fluid/gas is transported from one side of the heat pipe to the other through pressure, wick forces or gravity, depending on the arrangement of the heat pipe.
heat recovery ventilation