Lie Xu

Thermal contact conductance between solid interfaces under low temperature and vacuum

In this article, an experimental device used for thermal contact conductance tests under low temperature and vacuum was demonstrated in detail, which may be used to simulate the real environment of some solid materials, such as stainless steel, or aluminum in a space satellite. Thermal contact conductance experiments of stainless steel, of aluminum, and between stainless steel and aluminum were made for 0.02 Pa and 100–330 K. The relationships of thermal contact conductance to the contact loading pressure and to the temperature were measured. It is demonstrated that the thermal contact conductance between stainless steel, aluminum, between stainless steel, and aluminum contacts rises with the temperature increase of the contact interface, as well as the loading pressure increase of the contact interface. The thermal contact conductance of aluminum is larger than that of stainless steel for the same temperature and same loading pressure of the contact interface. The thermal contact conductance between stai...

Nucleate pool boiling heat transfer measurements of HFC23/CFC13 system

Nucleate pool boiling heat transfer data of the HFC23/CFC13 system have been systematically measured in a wide range of pressures and heat fluxes. The experimental results are also compared with the measured data of R508A and R508B. It is found that the heat transfer coefficient of R503 (HFC23/CFC13=0.511/0.489) is higher than that of R508A and R508B. Furthermore, the measured data were compared with the predicted results with three well-known correlations. Correlation by Fujita and Tsutsui can provide acceptable results. Most of the data fall within ±20% of this correlation.

Pulse Tube Refrigerator with low Temperature Switching Valve

Publisher Summary This chapter proposes a new method for achieving large refrigeration powers for some industrial applications. It proposes a new type of pulse tube refrigerator, termed pulse tube refrigerator with low temperature switching valve. Pulse tube refrigerator has been developing at an amazing speed Its refrigeration performance is now becoming comparable to that of G-M refrigerator or Stirling refrigerator. Therefore pulse tube refrigerator is finding more and more applications. It is suitable for industrial applications that require large refrigeration powers. In this kind of pulse tube refrigerator a recuperative heat exchanger instead of a regenerator is used and a switching valve is installed at the cold end of an orifice pulse tube. The adiabatic expansion efficiency of the orifice pulse tube with low temperature switching valve, which actually works as a new type of expander, has been experimentally investigated. Adiabatic efficiencies higher than 40% have been achieved in the preliminary experiments.

NUCLEATE POOL BOILING HEAT TRANSFER OF BINARY MIXTURES WITH DIFFERENT BOILING RANGES

The nucleate pool boiling heat transfer data on a smooth flat surface were measured for three binary mixtures of HC600a/HFC134a, HC600a/HC290, and HC600a/HFC23. Much effort was made to investigate the influence of the boiling range on the pool-boiling heat transfer performance. From the experimental results, the HC600a/HFC23 mixture with a wide boiling range showed lower heat transfer coefficients (HTCs) than the mixture with a narrow boiling range such as HC600a/HFC134a and HC600a/HC290 systems. The measured data were also compared with the results predicted by five well-known correlations. It can be found that the average deviation is less than 25% for mixtures with narrow boiling ranges, but a larger deviation for mixtures with wide boiling ranges.

Pulse tube refrigerator with low temperature switching valve: concept and experiments

The concept of a new type of pulse tube refrigerator, termed pulse tube refrigerator with low temperature switching valve, is proposed. It is suitable for industrial applications that require larger refrigeration powers. In this kind of pulse tube refrigerator a recuperative heat exchanger instead of a regenerator is used and a switching valve is installed at the cold end of an orifice pulse tube. The adiabatic expansion efficiency of the orifice pulse tube with low temperature switching valve, which actually works as a new type of expander, has been experimentally investigated. Adiabatic efficiencies higher than 40% have been achieved in the preliminary experiments. Methods for increasing the adiabatic efficiency are discussed.

The fast measurement of thermal conductivity for the refrigerant by the transient hot-wire contrast method

Abstract This paper describes a fast measuring method of thermal conductivity by the transient hot-wire contrast method. It introduces the measuring method and apparatus, gives the experimental results and error analysis. The method can be used to measure the thermal conductivity of refrigerants at various temperatures quickly, and it is especially fit for the high viscosity refrigerants. It has the virtues of short testing time and high accuracy. Using the method the thermal conductivities of two kinds of refrigerants at low temperature have been measured, the accuracy of the measurement is estimated to be within ± 2%.