CONVECTIVE HEAT TRANSFER TEST BED
Heat Transfer Enhancement using a Nanofluid
It is known that the addition of nanoparticles to a fluid may enhance its thermal characteristics. However, the amount of nanoparticles, or type of nanoparticles, is difficult to determine without careful analysis of the heat transfer capabilities of the fluid before and after introduction.
ESI has designed a system for determining the thermal characteristics of a carbon nanofiber rich fluid and compared the results to other standard fluids that are typically used in heat exchangers. The flow loop design is based on the circulation of the test fluid through a small heat exchanger.
In essence, the whole design may be described by the following block diagram, Figure 1, with the test fluid being pumped from the reservoir, through the heat exchanger, and back to the reservoir through an electronic flowmeter.
The test fluid in the reservoir is heated using a secondary heat source. In this case the thermal energy is supplied by an electrical hot water boiler capable of maintaining near constant hot water temperature through a coil that is immersed within the test fluid reservoir, Figure 2. This ensures that the test fluid under consideration has no direct contact with any electrical supply and may be changed without the need for cleaning the boiler.
A centrifugal fan provides a cooling source for forced convection across the heat exchanger assembly, with multiple temperature sensors monitoring the system, i.e.
– Plenum Air inlet temperature
– Plenum Air outlet temperature
– Test Fluid Reservoir temperature
– Heat Exchanger Inlet temperature
– Heat Exchanger Outlet temperature
The thermal characteristic of a new nanofluid is presented in terms of the Nusselt Number (Nu), Fig 3, and compared with standard fluids, namely: water, distilled water, and Ethylene Glycol.
Results have indicated that for the same range of power input to each of these fluids the nanofluid provided a larger heat transfer (Nu) for an increased Reynolds number (Re).
Figure 1: Schematic of the Heat Transfer Flow Loop
Figure 2: Overview of the NanoFluid Thermal Performance Flow Loop
Thermal Performance of the NanoFluid