 | Exploring Flow and Heat Transfer Characteristics of New Polymer-Nanofluids Thesis Advisor: Prof. Milivoje Kostic Graduate Assistant: Craig Netemeyer
See also: nFHT_Apparatus.htm * More at: www.kostic.niu.edu/DRnanofluids <<Click on the picture to enlarge |
Thermal conductivity studies have been the focus of nanofluid research so far, but ultimately, their flow and heat transfer characteristics in real, practical applications will determine their usefulness as advanced flow and heat-transfer fluids. In that regard, the main purpose of this thesis research is to investigate the flow and heat transfer characteristics of different nanofluids using recently developed apparatus. The addition of nanoparticles in a base fluid has been shown to significantly improve the heat transfer capabilities of that base fluid. The nanoparticles also adversely impact the flow capabilities of the base fluids, so it is necessary to balance the two properties in order to create the optimal suspension. A Hot-Wire Thermal Conductivity (HWTC) apparatus and a Parallel-Plate Thermal Conductivity (PPTC) apparatus have already been developed and used to measure the thermal conductivities of the nanofluids. These two apparatuses will be used in conjunction with the new Nanofluid Flow-and-Heat-Transfer (N-FHT) apparatus.
The N-FHT apparatus is the focus of the current research (See Appendix A for the apparatus schematic). The N-FHT apparatus works by pressurizing a 1 liter batch of nanofluids with nitrogen gas and then releasing it to flow down a heated capillary tube. The heating power, temperature change along the capillary tube, and the flow rate of the fluid is measured in order to calculate the flow and heat transfer characteristics (friction factor and Nusselt number). Investigation of flow and heat transfer characteristics in a wide range of flow rates (Reynolds numbers), including both laminar and turbulent flow regimes will be performed. By varying the concentration of nanoparticles and polymers in the base fluids, we will be able to determine the optimal nanofluid suspension parameters.
Much work has been completed over the past semester. Fabrication of the apparatus is now complete and all of the sensors have been calibrated. The thermocouples were calibrated against an RTD temperature gauge and now read within 0.1 degrees Celsius accuracy. The ultrasonic level sensor was calibrated against a lab grade caliper within the operating range of 2 to 14 inches. All of the measured data by the sensors are acquired and processed by a National Instruments’ Computerized Data Acquisition System using LabView® application software. Preliminary flow experiments have been performed with distilled water which is being used to calibrate the ultrasonic level and other sensor (See Appendix B for a detailed breakdown of the work completed).
The plan for the summer is to run the flow and heat transfer tests. The first task is to fully calibrate the apparatus using distilled water. Water has well established properties and results for Nusselt Number, and friction factor correlations in wide range of flow rates. It is also possible to use the N-FHT apparatus as a capillary viscometer. A separate program will be developed to determine the viscosities of the test fluids in laminar flow through the apparatus. After the calibration is complete, nanofluid testing will commence. The first step will be to fabricate different types of nanofluids. Different concentrations and types of nanoparticles and polymers will be added to the base fluids and mixed using mechanical agitation and an ultrasonic mixer. After the nanofluids are created, the thermal conductivity will be measured using the HWTC and PPTC apparatuses. The viscosity of the fluid will then be measured using the Brookfield Cone-and-Plate Digital Viscometer and/or capillary viscometer. The thermal conductivity and viscosity will then be used as input to the N-FHT apparatus’s DAQ system. After that, the fluid will be run through N-FHT apparatus, and the flow and heat transfer data will be determined from measured data. Consistency and error uncertainty of measurements will be determined in repetitive testing under the same conditions. Finally, a parametric investigation will be conducted to optimize nanofluids properties and their flow and heat transfer characteristics. This research should increase NIU competitiveness in acquiring external research grants.
APPENDIX A – N-FHT Apparatus Schematic
1) Test fluid is pressurized with nitrogen in high-pressure reservoir
2) Fluid flows through the stainless steel capillary tube heated with high-current DC
3) Temperatures are measured along the tube as the test fluid flows through
4) The fluid exits the tube and the outlet temperature is measured along with inlet temperature and heating power
5) The flow rate is calculated using the measured change of fluid level in the low-pressure reservoir
6) Nusselt Number and friction factor is calculated using the collected data