Development of experimental techniques for measurement of heat transfer rates in heat exchangers in oscillatory flows

Heat exchangers are important components of thermoacoustic devices. In oscillatory flow conditions, the flow and temperature fields around the heat exchangers can be quite complex, and may significantly affect heat transfer behaviour. As a result, one cannot directly apply the heat transfer correlations for steady flows to the design of heat exchangers for oscillatory flows. The fundamental knowledge of heat transfer in oscillatory flows, however, is still not well-established. The aim of the current work is to develop experimental apparatus and measurement techniques for the study of heat transfer in oscillatory flows. The heat transferred between two heat exchangers forming a couple was measured over a range of testing conditions. Three couples of finned-tube heat exchangers with different fin spacing were selected for the experiment. The main parameters considered were fin spacing, fin length, thermal penetration depth and gas displacement amplitude. Their effects on the heat exchanger performance were studied. The results were summarised and analysed in terms of heat transfer rate and dimensionless heat transfer coefficient: Colburn-j factor. In order to obtain the gas side heat transfer coefficient in oscillatory flows, the water side heat transfer coefficient is required. Thus, an experimental apparatus for unidirectional steady test was also developed and a calculation method to evaluate the heat transfer coefficient was demonstrated. The uncertainties associated with the measurement of heat transfer rate were also considered.

[1]  Rex Klopfenstein,et al.  Air velocity and flow measurement using a Pitot tube , 1998 .

[2]  G. Swift.  Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators , 2017 .

[3]  Andrej Pázman,et al.  Nonlinear Regression , 2019, Handbook of Regression Analysis With Applications in R.

[4]  Artur J. Jaworski,et al.  Convective heat transfer from fins-on-tubes heat exchangers in an oscillatory flow. , 2011 .

[5]  John M. Cimbala,et al.  Fluid Mechanics: Fundamentals and Applications , 2004 .

[6]  R. Viskanta,et al.  Journal of Heat Transfer Policy on Reporting Uncertainties in Experimental Measurements and Results , 1993 .

[7]  Y. Çengel.  Introduction to thermodynamics and heat transfer , 1996 .

[8]  D. A. Mooney,et al.  Introduction to Thermodynamics and Heat Transfer , 1956 .

[9]  H. Bass,et al.  Temperature discontinuities between elements of thermoacoustic devices , 1997 .

[10]  D. G. Archer.  Thermodynamic Properties of the NaCl+H2O System l. Thermodynamic Properties of NaCl(cr) , 1992 .

[11]  D. Butterfield,et al.  Problems with Pitots. Issues with flow measurement in stacks , 2004 .

[12]  Fabio Polonara,et al.  23RD IIR INTERNATIONAL CONGRESS OF REFRIGERATION , 2011 .

[13]  Emmanuel C. Nsofor,et al.  Experimental study on the heat transfer at the heat exchanger of the thermoacoustic refrigerating system , 2007 .

[14]  S. J. Kline,et al.  Describing Uncertainties in Single-Sample Experiments , 1953 .

[15]  James E. Braun,et al.  Characterizing heat transfer coefficients for heat exchangers in standing wave thermoacoustic coolers , 2005 .

[16]  Zhihua Gan,et al.  Heat transfer of laminar oscillating flow in finned heat exchanger of pulse tube refrigerator , 2014 .

[17]  Michael A. Lombardi,et al.  Stopwatch and Timer Calibrations , 2004 .

[18]  C. Angell,et al.  Heat capacity of water at extremes of supercooling and superheating. Technical report , 1981 .

[19]  Hugh W. Coleman,et al.  Experimentation, Validation, and Uncertainty Analysis for Engineers , 2009 .

[20]  R. W. Carter,et al.  Thermodynamic Properties of the NaCl + H2O System. 4. Heat Capacities of H2O and NaCl(aq) in Cold-Stable and Supercooled States , 2000 .

[21]  Ray Scott Wakeland,et al.  Effectiveness of parallel-plate heat exchangers in thermoacoustic devices , 2004 .

[22]  Pascal Stouffs,et al.  Experimental study of heat transfer in oscillating flow , 2005 .

[23]  George Mozurkewich,et al.  Heat transfer from transverse tubes adjacent to a thermoacoustic stack , 2001 .

[24]  David K. Perkins,et al.  THERMOACOUSTIC REFRIGERATOR HEAT EXCHANGERS: DESIGN, ANALYSIS AND FABRICATION , 1994 .

[25]  W. Wagner,et al.  The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use , 2002 .

[26]  Frank P. Incropera,et al.  Introduction to Heat Transfer -5/E. , 2008 .

[27]  W. P. Arnott,et al.  Thermoacoustic engines , 1991, IEEE 1991 Ultrasonics Symposium,.

[28]  Hobart M. Hudson,et al.  Pipe Flow: A Practical and Comprehensive Guide , 2012 .