Li-Zhong Han

Performance analysis of an absorption heat transformer with different working fluid combinations

The absorption heat transformer (AHT) is a promising system for recovering waste heat. It can effectively recover about 50% of the waste heat and reuse it in industrial processes. However, there exists a need for identifying suitable working fluid combinations and for evaluating their relative performance characteristics. As an initial step, this paper presents a comparative performance study for the absorption heat transformer with H2O/LiBr, TFE(2,2,2-trifluoroethanol)/NMP(N-methy1-2-pyrrolidone), TFE/E181(dimethylether tetraethylene glycol) and TFE/PYR(2-pyrrolidone). The results show that the four working fluid combinations are all suitable for absorption heat transformers. H2O/LiBr is suitable at lower operating temperatures, while TFE/NMP, TFE/E181 and TFE/PYR are suitable at higher operating temperatures.

Experimental vapor pressure data and a vapor pressure equation for trifluoroiodomethane (CF3I)

Abstract Sixty four vapor pressure data points for trifluoroiodomethane (CF3I) have been measured for the temperature range from 243.15 to 393.15 K. The maximum total pressure uncertainty of these data is estimated to be within ± 1.0 kPa. The purity of the sample used in this work is 99.95% with 3.4 ppm of water. Based on this data set, a vapor pressure equation for CF3I has been developed. This equation contains four coefficients and correlates the measured vapor pressures within ± 0.03%.

PVT properties, vapor pressures and critical parameters of HFC-32

Abstract One hundred twenty three PVT data points for HFC-32 in the gaseous phase have been measured using Burnett method along fourteen isotherms for temperatures from 243 to 373 K, pressures from 0.07 to 5.7 MPa and densities from 1.8 to 240 kg m −3 . The present experimental PVT data, compared with the EOS developed by Piao et al., has an RMS deviation of 0.17%. Sixty vapor pressure data points for HFC-32 have also been measured for the temperature range from 233 to 351 K. The RMS deviation of the pressures in the present data from the vapor pressure equation developed by Piao et al. is 0.063%. Based on the present data and selected data from other investigators, a new vapor pressure equation for HFC-32 has been developed. By means of visual observation of the disappearance of the meniscus in an optical cell, the critical temperature, density and pressure for HFC-32 have been determined to be 351.295 ± 0.010 K, 425 ± 3 kg m −3 and 5.785 ± 0.002 MPa, respectively. The purity of the HFC-32 was 99.95 wt.%.

Vapor pressure of 1,1,1,2,3,3,3-heptafluoropropane

Abstract A total of 84 vapor pressure data points for 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) have been measured in the temperature range from 243 to 375 K. The maximum total pressure uncertainty of these data is estimated to be within ±1 kPa. The purity of the sample used in this work is 99.9 mol%. Based on this data set, a vapor pressure equation for HFC-227ea has been developed. The root-mean-square (RMS) deviation of the experimental data from the vapor pressure equation is 0.057%. The normal boiling point of HFC-227ea was also determined.

Surface tension of HFC-134a

Abstract Zhu, M.-S., Han, L.-Z. and Lu, C.-X., 1992. Surface tension of HFC-134a. Fluid Phase Equilibria 86: 363-367 This paper describes the differential capillary rise technique used to measure accurately the surface tension for HFC-134a. A set of accurate experimental surface tension data for HFC-134a measured with this apparatus is also presented. The data span the temperature range 19–68°C. The sample purity was 99.98%.

An experimental study of PVT properties of CFC alternative HFC-134a

Abstract HFC-134a is currently considered as a prospective substitute to the conventional CFC-12. In the present study, we have measured PVT property of HFC-134a for the gas phase by using Burnett method. The experimental apparatus designed and developed by ourself is introduced in detail. Tested experiment is done using high purity He. The RMS Dev. in pressure is 0.087%. The experimental uncertainty of the present measurement has been estimated being within±15mK for temperature, ±AlcPa for pressure respectively. The sample used is having a purity either one of 99.98 or 99.95 wtX. Forty-two PVT data have been measured. The present experimental PVT data as well as those reported by Wilson et al., Weber and Piao et al. are compared with the EOS developed by Piao et al. The results show that the present data are reliable.

Imaging of thermal conductivity with sub-micrometer resolution using scanning thermal microscopy

With the development of new emerging technologies, many objects in scientific research and engineering are of sub-micrometer and nanometer size, such as microelectronics, micro-electro-mechanical systems (MEMS), biomedicines, etc. Therefore, thermal conductivity measurements with sub-micrometer resolution are indispensable. This paper reports on the imaging of various micrometer and sub-micrometer size surface variations using a scanning thermal microscope (SThM). The thermal images show the contrasts indicating the differences of the local thermal conductivity in the sample. Thermal resistance circuits for the thermal tip temperature are developed to explain the heat transfer mechanism between the thermal tip and the sample and to explain the coupling between the local thermal conductivity and the topography in the test results.

Surface tension of trifluoroiodomethane (CF3I)

Abstract The surface tension of trifluoroiodomethane (CF3I) has been measured in the present work. The measurements were conducted under equilibrium conditions between the liquid and its saturated vapor. Thirty data points have been obtained by differential capillary rise method (DCRM) in the temperature range from 243 to 344 K. The temperature uncertainty is within ±10 mK. The accuracy of surface tension measurements is estimated to be within ±0.1 mN m−1. The correlation of surface tension also has been proposed, the RMS deviation is 0.58%.

Experimental pressure-volume-temperature data and an equation of state for trifluoroiodomethane (CF3I) in gaseous phase

Abstract Some 175 pressure-volume-temperature data points in gaseous phase for trifluoroiodomethane (CF 3 I) have been measured using Burnett/isochoric methods. Burnett expansion measurements were made both at 353.15 K and at 323.15 K. Based on the pressure-volume relationships established both at 353.15 K and at 323.15 K isotherms, data were collected along isochores. Data along eight isochores were measured at the temperature range from 323.15 K to 393.15 K. Data along five isochores were measured at the temperature range from 278.15 K to 323.15 K. The pressure range is from 0.19 to 1.75 MPa. The maximum total temperature uncertainty in this work is estimated to be within ± 10 mK, the maximum total pressure uncertainty in this work is estimated to be within ± 500 Pa. The present data have been correlated with a virial equation of state. This equation has a root-mean-square deviation (RMS) deviation of 0.11 % in pressure and a RMS deviation of 0.12% in density. The purity of the sample used in this work is 99.95 wt.% with 3.4 ppm of water.

Speed of sound and ideal-gas heat capacity at constant pressure of gaseous trifluoroiodomethane (CF3I)

Abstract The speed of sound of the gaseous trifluoroiodomethane (CF3I) was measured for temperatures from 273.15 to 333.15 K and pressures from 58 to 276 kPa with a cylindrical, variable-path acoustic interferometer operating at 156.252 kHz. The uncertainty of the speed of sound was less than ±0.1%. The ideal-gas heat capacity at constant pressure and the second acoustic virial coefficients were determined over the temperature range from the speed of sound measurements. The ideal-gas heat capacity at constant pressure and second virial coefficients calculated from the present speed of sound measurements were compared with the available data. The uncertainty of the ideal-gas heat capacity at constant pressure was estimated to be less than ± 1%.