Download or read book Pool Boiling of Low GWP Replacements for R134a on a Reentrant Cavity Surface Extensive Measurement and Analysis written by Mark A. Kedzierski and published by . This book was released on 2017 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper quantifies the pool boiling performance of R134a, R1234yf, R513A, and R450A on a flattened, horizontal Turbo-ESP surface. The study showed that the boiling performance of R134a on the Turbo-ESP exceeded that of the replacement refrigerants for heat fluxes greater than 20 kWm-2. On average, the heat flux for R1234yf and R513A was 16 % and 19 % less than that for R134a, respectively, for R134a heat fluxes between 20 kWm-2 and 110 kWm-2. The heat flux for R450A was on average 57 % less than that of R134a for heat fluxes between 30 kWm-2 and 110 kWm-2. A model was developed to predict both single-component and multi-component pool boiling of the test refrigerants on the Turbo-ESP surface. The model accounts for viscosity effects on bubble population and uses the Fritz (1935) equation to account for increased vapor production with increasing superheat. Both loss of available superheat and mass transfer resistance effects were modeled for the refrigerant mixtures. For most heat fluxes, the model predicted the measured superheat to within ℗ł 0.31 K.
Download or read book Pool Boiling of R515A R1234ze E and R1233zd E on a Reentrant Cavity Surface written by Mark A. Kedzierski and published by . This book was released on 2019 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper quantifies the pool boiling performance of R515A, R1234ze(E), and R1233zd(E) on a flattened, horizontal Turbo-ESP surface for air-conditioning applications for heat fluxes between roughly 10 kWm-2 and 100 kWm-2. Both R515A and R1234ze(E) are replacements for R134a, while R1233zd(E) is a replacement for R123. The measured boiling curve for R515A had roughly a 14 [percent] larger heat flux than that of R1234ze(E) for heat fluxes greater than 45 kWm-2. For heat fluxes between 14 kWm-2 and 85 kWm-2, R515A and R1234ze(E) exhibited a heat flux that was 33 [percent] and 17 [percent] larger than that for R134a. The heat flux of R1233zd(E) was roughly 18 [percent] larger than that for R123 for heat fluxes between 30 kWm-2 and 87 kWm-2. A pool boiling model that was previously developed for pure and mixed refrigerants on the Turbo-ESP surface was improved by nondimensionalizing the model constants and improving their statistical significance. For most heat fluxes, the model predicted the measured superheat to within +/- 0.7 K. The model was used to show that the vapor Prandtl number and the product of the latent heat and vapor density significantly influenced the boiling heat flux.
Download or read book Effect of IF WS2 Nanolubricant on R134a Boiling on a Reentrant Cavity Surface Extensive Measurement and Analysis Details written by Mark A. Kedzierski and published by . This book was released on 2019 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report quantifies the influence of inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles on the pool-boiling performance of R134a/polyolester mixtures on a commercial (Turbo-ESP) boiling surface. Tungsten disulfide nanoparticles, of roughly 150 nm, were used at a 15 % mass fraction in a base polyolester lubricant to produce the test nanolubricant. The nanolubricant was mixed with R134a at a 1 % mass fraction. The study showed that the nanolubricant caused an average 37 % degradation in the boiling heat flux as compared to R134a/neat-lubricant boiling on a reentrant cavity surface at the same superheat. Similarly, boiling with R134a/neat-lubricant caused, on average, a 27 % degradation in the boiling heat flux as compared to pure R134a boiling and the same superheat. An analysis was presented which showed that the nanoparticles were too large and too dense to promote a boiling enhancement. In addition, the fullerene-like structure and the large size encouraged nanoparticle settling, which presumably filled cavities of the boiling surface leading toadditional boiling degradations.
Download or read book Nist Technical Note 1631 written by U.s. Department of Commerce and published by Createspace Independent Publishing Platform. This book was released on 2014-02-18 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper quantifies the influence of diamond nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a roughened, horizontal, flat surface. Nanofluids are liquids that contain dispersed nano-size particles.
Download or read book Pool Boiling of HFO 1336mzz Z on a Reentrant Cavity Surface written by Mark A. Kedzierski and published by . This book was released on 2018 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper quantifies the pool boiling performance of R1336mzz(Z), and R123 on a flattened, horizontal Turbo-ESP surface for heat fluxes between roughly 10 kWm-2 and 120 kWm-2. The study showed that the boiling performance of R1336mzz(Z) on the TurboESP did not differ statistically from that of R123 for heat fluxes between 13 kWm-2 and59 kWm-2. For heat fluxes larger than 59 kWm-2, the R123 boiling heat flux was up to 5 % larger than the heat flux for R1336mzz(Z). For heat fluxes between 4 kWm-2and 13 kWm-2, the R123 heat flux was approximately 53 % larger than that of R1336mzz(Z). The R1336mzz(Z) pool boiling curve was measured for three saturation temperatures and exhibited an optimum with respect to saturation temperature near the middle saturation temperature of 298.1 K. A pool boiling model from the present authors was modified to include a single-phase transfer term and was used to predict both single-component and multi-component performance of the test refrigerants on the Turbo-ESP surface. For most heat fluxes, the modified model predicted the measured superheat to within +/- 0.5 K.
Download or read book Nist Technical Note 1663 written by Mark A. Kedzierski and published by Createspace Independent Publishing Platform. This book was released on 2014-02-19 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper quantifies the influence of Al2O3 nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a roughened, horizontal, flat surface. Nanofluids are liquids that contain dispersed nano-size particles. A lubricant based nanofluid (nanolubricant) was made by suspending nominally, 10 nm diameter Al2O3 particles in a synthetic ester to roughly a 1.6 % volume fraction. The nanoparticles enhanced the boiling heat transfer relative to that for R134a/polyolester mixtures without nanoparticles for the three lubricant mass fractions that were tested.
Download or read book Horizontal Convective Boiling of R134a R1234yf r134a and R1234ze e Within a Micro fin Tube With Extensive Measurement and Analysis Details written by National Institute of Standards and Technology and published by CreateSpace. This book was released on 2014-02 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents local convective boiling measurements in a micro-fin tube for R134a and two low global warming potential (GWP ) refrigerants: R1234yf/ R134a, 56/44 % mass and R1234ze(E). Water heating either in counterflow or in parallel flow with the test refrigerant was used to vary the heat flux for a given quality. The heat transfer coefficient of the three test fluids were compared at the same heat flux, saturated refrigerant temperature, and refrigerant mass flux using an existing correlation from the literature. The resulting comparison showed that refrigerant R134a exhibited the highest heat transfer performance in large part due to its higher thermal conductivity as compared to the tested low-GWP refrigerants. For the example case presented here, the heat transfer coefficient for R1234yf/ R134a (56/44) remains within 5 % of the heat transfer coefficient for R134a, having essentially identical performance for qualities less than 30 %. The heat transfer coefficient for R1234ze(E) is roughly 700 kW, K-1, m-2 (approximately 14 %) less than that of R134a for qualities greater than 30 %. The smaller heat transfer coefficient of R1234ze(E) as compared to that of R134a is primarily due to the 11 % smaller thermal conductivity and the 21 % smaller reduced pressure as compared to R134a at this test temperature. The measurements are important as part of the evaluation of low-GWP replacement refrigerants for R134a in unitary refrigeration and air-conditioning equipmen
Download or read book Effect of Concentration on R134a Al2O3 Nanolubricant Mixture Boiling on a Reentrant Cavity Surface with Extensive Measurement and Analysis Details written by Mark A. Kedzierski and published by . This book was released on 2013 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Al2o3 Nanolubricant on R134a Pool Boiling Heat Transfer With Extensive Measurement and Analysis Details written by nist and published by CreateSpace. This book was released on 2014-03-17 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper quantifies the influence of Al2O3 nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a roughened, horizontal, flat surface. Nanofluids are liquids that contain dispersed nano-size particles. A lubricant based nanofluid (nanolubricant) was made by suspending 20 nm diameter Al2O3 particles in a synthetic ester to roughly a 1.6 % volume fraction. The nanoparticles enhanced the boiling heat transfer relative to that for R134a/polyolester mixtures without nanoparticles for the three lubricant mass fractions that were tested. The enhancement occurred for the lowest heat fluxes, which gives the opportunity for designing chillers for lower approach temperatures. For the 0.5 % nanolubricant mass fraction, the nanoparticles caused a heat transfer enhancement relative to the heat transfer of pure R134a/polyolester (99.5/0.5) as large as 400 % for the lowest tested heat flux. The average heat flux improvement for heat fluxes less than 40 kW/m2 was approximately 105 %, 49 %, and 155 % for the 0.5 %, the 1 %, and the 2 % mass fractions, respectively. The heat flux enhancement for all of the mixtures increased with respect to decreasing heat flux. Due to the good quality of the nanolubricant suspension, the performance of the (99.5/0.5), and the (98/2) nanolubricant mixtures was stable over time.
Download or read book Horizontal Convective Boiling of R134a R1234yf R134a and R1234ze e Within Micro Fin Tube with Extensive Measurement and Analysis Details written by U.s. Department of Commerce and published by CreateSpace. This book was released on 2014-06-24 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internally enhanced tubes, like the micro-fin tube, are used by most manufacturers in the construction of evaporators and condensers for new unitary refrigeration and air-conditioning equipment. The reason for the micro-fin tube's hold on unitary equipment is that it provides the highest heat transfer with the lowest pressure drop of the commercially available internal enhancements (Webb and Kim, 2005). Most of the experimental measurements for evaporative heat transfer coefficients in the micro-fin tube have been done for traditional refrigerants like R134a. Pressure from the policies set by the Montreal Protocol (1987), the Kyoto Protocol (1997) and the European Mobile Directive (2006) have caused a recent shift to refrigerants with both zero ozone depletion potential (ODP) and low global warming potential (GWP). Johnson et al. (2012) reports that azeotropic R1234yf/ R134a (56/44) (i.e., XP10) 1 and R1234ze(E) are among the low-GWP refrigerants identified for evaluation by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Low-GWP Alternative Refrigerants Evaluation Program as potential replacement refrigerants for R134a. The reason for this is that both R1234yf/ R134a (56/44) and R1234ze(E) have zero ODP and 100 year GWPs of approximately 600 and 6, respectively (Hickman, 2012 and Bitzer, 2012). Consequently, flow boiling heat transfer data for the micro-fin tube with R1234yf/ R134a (56/44) and R1234ze(E) are essential for the evaluation of their use for unitary applications.
Download or read book Effect of Bulk Lubricant Concentration on the Excess Surface Density During R134a Pool Boiling with Extensive Measurement and Analysis Details written by nist and published by Createspace Independent Publishing Platform. This book was released on 2013-11-14 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper investigates the effect that the bulk lubricant concentration has on the non-adiabatic lubricant excess surface density on a roughened, horizontal flat pool-boiling surface. Both pool boiling heat transfer data and lubricant excess surface density data are given for pure R134a and three different mixtures of R134a and a polyolester lubricant (POE). A spectrofluorometer was used to measure the lubricant excess density that was established by the boiling of a R134a/POE lubricant mixture on a test surface. The lubricant is preferentially drawn out of the bulk refrigerant/lubricant mixture by the boiling process and accumulates on the surface in excess of the bulk concentration. The excess lubricant resides in an approximately 40 mm layer onthe surface and influences the boiling performance. The lubricant excess surface density measurements were used to modify an existing dimensionless excess surface density parameter so that it is valid for different reduced pressures. The dimensionless parameter is a key component for a refrigerant/lubricant pool boiling model given in the literature. In support of improving the boiling model, both the excess measurements and heat transfer data are provided for pure R134a and three R134a/lubricant mixtures at 277.6 K. The heat transfer data shows that the lubricant excess layer causes an average enhancement of the heat flux of approximately 50 % for the 0.5 % lubricant mass fraction mixture relative to pure R134a heat fluxes between 4 kW/m2 and 20 kW/m2. Conversely, both the 1 % and the 2 % lubricant mass fraction mixtures experienced an average degradation of approximately 60 % in the heat flux relative to pure R134a heat fluxes between approximately 4 kW/m2 and 20 kW/m2. This study is an effort toward generating data that can be used to support a boiling model that can be used to predict whether lubricants degrade or improve boiling performance.
Download or read book Effect of Bulk Lubricant Concentration on the Excess Surface Density During R134a Pool Boiling with Extensive Measurement and Analysis Details written by Mark A. Kedzierski and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Horizontal Convective Boiling of R1234yf R134a and R450A Within a Micro fin Tube written by Mark A. Kedzierski and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents local convective boiling heat transfer and Fanning friction factor measurements in a micro-fin tube for R134a and two possible low global warming potential (GWP) refrigerant replacements for R134a: R1234yf and R450A. Test section heating was achieved with water in either counterflow or in parallel flow with the test refrigerant to provide for a range of heat fluxes for each thermodynamic quality. An existing correlation from the literature for single and multi-component mixtures was shown to not satisfactorily predict the convective boiling measurements for flow qualities greater than 40 %. Accordingly, a new correlation was developed specifically for the test fluids of this study so that a fair comparison of the heat transfer performance of the low GWP refrigerants to that of R134a could be made. The new correlation was used to compare the heat transfer coefficient of the three test fluids at the same heat flux, saturated refrigerant temperature, and refrigerant mass flux. The resulting example comparison, for the same operating conditions, showed that the heat transfer coefficient of the multi-component R450A and the single-component R1234yf were, on average, 15 % less and 5 % less, respectively, than that of the single-component R134a. Friction factor measurements were also compared to predictions from an existing correlation. A new correlation for the friction factor was developed to provide a more accurate prediction. The measurements and the new models are important for the evaluation of potential low-GWP refrigerants replacements for R134a.
Download or read book Effect of Bulk Lubricant Concentration on the Excess Surface Density During R134a Pool Boiling with Extensive Measurement and Analysis written by Mark A. Kedzierski and published by . This book was released on 2003 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of CuO Nanolubricant on R134a Pool Boiling Heat Transfer with Extensive Measurement and Analysis Details written by Mark A. Kedzierski and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of CuO Nanolubricant on R134a Pool Boiling Heat Transfer with Extensive Measurement and Analysis Details written by Mark A. Kedzierski and published by . This book was released on 2007 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Acoustic Excitation on R134a Al2O3 Nanolubricant Mixture Boiling on a Reentrant Cavity Surface with Extensive Measurement and Analysis Details written by Mark A. Kedzierski and published by . This book was released on 2014 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:
